Journal articles on the topic 'Corneal ablation'
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Wilkerson, Joseph L., Sandip K. Basu, Megan A. Stiles, Amanda Prislovsky, Richard C. Grambergs, Sarah E. Nicholas, Dimitrios Karamichos, Jeremy C. Allegood, Richard L. Proia, and Nawajes Mandal. "Ablation of Sphingosine Kinase 1 Protects Cornea from Neovascularization in a Mouse Corneal Injury Model." Cells 11, no. 18 (September 17, 2022): 2914. http://dx.doi.org/10.3390/cells11182914.
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The purpose of this study was to investigate the role of sphingosine kinase 1 (SphK1), which generates sphingosine-1-phosphate (S1P), in corneal neovascularization (NV). Wild-type (WT) and Sphk1 knockout (Sphk1−/−) mice received corneal alkali-burn treatment to induce corneal NV by placing a 2 mm round piece of Whatman No. 1 filter paper soaked in 1N NaOH on the center of the cornea for 20 s. Corneal sphingolipid species were extracted and identified using liquid chromatography/mass spectrometry (LC/MS). The total number of tip cells and those positive for ethynyl deoxy uridine (EdU) were quantified. Immunocytochemistry was done to examine whether pericytes were present on newly forming blood vessels. Cytokine signaling and angiogenic markers were compared between the two groups using multiplex assays. Data were analyzed using appropriate statistical tests. Here, we show that ablation of SphK1 can significantly reduce NV invasion in the cornea following injury. Corneal sphingolipid analysis showed that total levels of ceramides, monohexosyl ceramides (HexCer), and sphingomyelin were significantly elevated in Sphk−/− corneas compared to WT corneas, with a comparable level of sphingosine among the two genotypes. The numbers of total and proliferating endothelial tip cells were also lower in the Sphk1−/− corneas following injury. This study underscores the role of S1P in post-injury corneal NV and raises further questions about the roles played by ceramide, HexCer, and sphingomyelin in regulating corneal NV. Further studies are needed to unravel the role played by bioactive sphingolipids in maintenance of corneal transparency and clear vision.
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Liang, Wentao, Li Huang, Xiang Ma, Lijie Dong, Rui Cheng, Marcus Dehdarani, Dimitrios Karamichos, and Jian-xing Ma. "Pathogenic Role of Diabetes-Induced Overexpression of Kallistatin in Corneal Wound Healing Deficiency Through Inhibition of Canonical Wnt Signaling." Diabetes 71, no. 4 (January 19, 2022): 747–61. http://dx.doi.org/10.2337/db21-0740.
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It was reported previously that circulation levels of kallistatin, an endogenous Wnt signaling inhibitor, are increased in patients with diabetes. The current study was conducted to determine the role of kallistatin in delayed wound healing in diabetic corneas. Immunostaining and Western blot analysis showed kallistatin levels were upregulated in corneas from humans and rodents with diabetes. In murine corneal wound healing models, the canonical Wnt signaling was activated in nondiabetic corneas and suppressed in diabetic corneas, correlating with delayed wound healing. Transgenic expression of kallistatin suppressed the activation of Wnt signaling in the cornea and delayed wound healing. Local inhibition of Wnt signaling in the cornea by kallistatin, an LRP6-blocking antibody, or the soluble VLDL receptor ectodomain (an endogenous Wnt signaling inhibitor) delayed wound healing. In contrast, ablation of the VLDL receptor resulted in overactivation of Wnt/β-catenin signaling and accelerated corneal wound healing. Activation of Wnt signaling in the cornea accelerated wound healing. Activation of Wnt signaling promoted human corneal epithelial cell migration and proliferation, which was attenuated by kallistatin. Our findings suggested that diabetes-induced overexpression of kallistatin contributes to delayed corneal wound healing by inhibiting the canonical Wnt signaling. Thus, kallistatin and Wnt/β-catenin signaling in the cornea could be potential therapeutic targets for diabetic corneal complications.
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Abdelhalim, Ibrahim, Omnia Hamdy, Aziza Ahmed Hassan, and Salah Hassab Elnaby. "Nd:YAG fourth harmonic (266-nm) generation for corneal reshaping procedure: An ex-vivo experimental study." PLOS ONE 16, no. 11 (November 29, 2021): e0260494. http://dx.doi.org/10.1371/journal.pone.0260494.
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Corneal reshaping is a common medical procedure utilized for the correction of different vision disorders relying on the ablation effect of the UV pulsed lasers, especially excimer lasers (ArF) at 193 nm. This wavelength is preferred in such medical procedures since laser radiation at 193 nm exhibits an optimum absorption by corneal tissue. However, it is also significantly absorbed by the water content of the cornea resulting in an unpredictability in the clinical results, as well as the high service and operation cost of the commercial ArF excimer laser device. Consequently, other types of solid-state UV pulsed lasers have been introduced. The present work investigates the ablation effect of solid-state laser at 266 nm in order to be utilized in corneal reshaping procedures. Different number of pulses has been applied to Polymethyl Methacrylate (PMMA) and ex-vivo rabbit cornea to evaluate the ablation effect of the produced laser radiation. PMMA target experienced ellipse-like ablated areas with a conical shape in the depth. The results revealed an almost constant ablation area regardless the number of laser pulses, which indicates the stability of the produced laser beam, whereas the ablation depth increases only with increasing the number of laser pulses. Examination of the ex-vivo cornea showed a significant tissue undulation, minimal thermal damage, and relatively smooth ablation surfaces. Accordingly, the obtained 266-nm laser specifications provide promising alternative to the traditional 193-nm excimer laser in corneal reshaping procedure.
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Kummelil, Mathew Kurian, Rohit Shetty, Luci Kaweri, Shama Shaligram, and Mukesh Paryani. "Outcomes of a Management Strategy in Eyes with Corneal Irregularity and Cataract." BioMed Research International 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/8497858.
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Purpose. To evaluate the outcomes of a management strategy in patients with irregular corneas and cataract.Methods. Six eyes of four patients presented for cataract surgery with irregular corneas following corneal refractive surgery. Topoguided ablation regularised the cornea, followed by phacoemulsification and intraocular lens implantation. Zonal keratometric coefficient of variation (ZKCV) measured structural changes and visual quality metrics measured functional improvement.Results. The mean duration after corneal refractive surgery was7.83±2.40years. The logmar uncorrected distance visual acuity (0.67±0.25) and the corrected distance visual acuity (0.38±0.20) improved to0.34±0.14and0.18±0.10, respectively. The changes in the standard deviations of the zonal keratometry values and the ZKCV were statistically significant in the 2, 3, and 4 mm zones. The changes in the Strehl ratio (ANOVAp=0.043) were also statistically significant.Conclusions. Corneal regularisation followed by phacoemulsification resulted in lower residual refractive error with improved visual quality metrics. This strategy is a viable option in patients with symptomatic cataracts and irregular corneas.
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ZHANG, DI, TAIFENG SUN, HAIXIA ZHANG, and LIN LI. "THE SIMULATION STUDY ON THE DEFORMATION OF RABBIT CORNEA AFTER REFRACTIVE SURGERY WITH DIFFERENT CUTTING THICKNESS." Journal of Mechanics in Medicine and Biology 17, no. 08 (December 2017): 1750118. http://dx.doi.org/10.1142/s0219519417501184.
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Based on the inflation tests data of rabbit cornea, finite element analysis has been applied to determine the material parameters, simulate corneal refractive surgery and study postoperative corneal deformations. The corneal profile and apical displacement data were recorded during the inflation experiment of five rabbit corneas. Inverse finite element method was applied to determine the material parameters from the corneal apical displacements. Based on the determined material parameters and the corneal profile information, we established five corneal geometry models that simulate refractive surgery with different cutting amounts. We analyzed displacements at corneal apex and cutting edge, corneal surface curvatures under different pressures. Both Ogden model ([Formula: see text]) and Yeoh model ([Formula: see text]) gave good fits to the experiment data. The maximum of error square sum between the calculated value and the experimental value of the displacements per point at the corneal profile was less than 0.06[Formula: see text]mm. For each model with the increase of pressure, the displacement at cutting edge was larger than that at corneal apex, both of them increased, and curvature radius of anterior and posterior corneal surface increased slowly, but the refractive power decreased slowly and tended to be a stable value. Under the same pressure, the larger the cutting amount, the larger the displacements at corneal apex and cutting edge with a cutting edge displacement of about 1.10 (less ablation model) and 1.02 (larger ablation model) times the corneal vertex displacement. Both Ogden model and Yeoh model can be used to describe corneal mechanical responses of inflation experiment. After refractive surgery, the displacement at cutting edge is larger than that at corneal apex, the curvature radius of anterior (posterior) corneal surface increases (decreases), and the refractive power decreases.
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Gutierrez, Miguel-Angel, Zejin Zhu, Rachael Philips, Anna U. Eriksson, Ramesh Halder, Peter Kim, Jennifer King, Narsing Rao, and Ram Raj Singh. "Conditional ablation of Langerhans cells exacerbates autoimmune corneal inflammation (P5134)." Journal of Immunology 190, no. 1_Supplement (May 1, 2013): 58.21. http://dx.doi.org/10.4049/jimmunol.190.supp.58.21.
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Abstract Ocular surface inflammation is common and sometimes severe in autoimmune diseases. Little is known about the role of cornea-resident dendritic cells, including Langerhans cells (LC), in ocular surface autoimmunity. Here, we analyzed corneal LC in autoimmune-prone MRL mice. LC (CD11c+ CD207+) were more abundant and activated (CD86+ CD40+) in the corneal epithelium of MRL mice than of B6 mice. However, LC were ~5-fold lower in the corneal stroma of MRL mice than of B6 mice. LC in cervical lymph nodes were also lower in MRL mice than in B6 mice. Ongoing studies will examine whether the increase of activated LC in corneal epithelium, but their reduction in corneal stroma and eye-draining lymph nodes in autoimmune mice is due to a defect in the migration of LC from the cornea to eye-draining lymph nodes. Since LC are believed to carry antigens from tissues to their respective draining lymph nodes to maintain tolerance in a tissue-specific manner, the reduced LC in eye-draining lymph nodes may lead to the breakdown of tolerance to eye antigens. To directly test the role of LC in ocular autoimmunity, we introgressed the Lang-eGFP.DTR knockin mutation from the stock B6 mice that express diphtheria toxin receptor (DTR) driven by Langerin promoter (Malissen, 2005) onto the MRL background. Diphtheria toxin injections depleted LC in Lang-eGFP.DTR MRL mice and accelerated corneal inflammation. Taken together, these data suggest a protective role of LC in corneal inflammation.
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Alcalde, Ignacio, Cristina Sánchez-Fernández, Susana Del Olmo-Aguado, Carla Martín, Céline Olmiere, Enol Artime, Luis M. Quirós, and Jesús Merayo-Lloves. "Synthetic Heparan Sulfate Mimetic Polymer Enhances Corneal Nerve Regeneration and Wound Healing after Experimental Laser Ablation Injury in Mice." Polymers 14, no. 22 (November 15, 2022): 4921. http://dx.doi.org/10.3390/polym14224921.
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(1) Background: Abnormal corneal wound healing compromises visual acuity and can lead to neuropathic pain. Conventional treatments usually fail to restore the injured corneal tissue. In this study, we evaluated the effectiveness of a synthetic heparan sulfate mimetic polymer (HSmP) in a mouse model of corneal wound healing. (2) Methods: A surgical laser ablation affecting the central cornea and subbasal nerve plexus of mice was used as a model of the wound-healing assay. Topical treatment with HSmP was contrasted to its vehicle and a negative control (BSS). Corneal repair was studied using immunofluorescence to cell proliferation (Ki67), apoptosis (TUNEL assay), myofibroblast transformation (αSMA), assembly of epithelial cells (E-cadherin) and nerve regeneration (β-tubulin III). (3) Results: At the end of the treatment, normal epithelial cytoarchitecture and corneal thickness were achieved in HSmP-treated animals. HSmP treatment reduced myofibroblast occurrence compared to eyes irrigated with vehicle (p < 0.01) or BSS (p < 0.001). The HSmP group showed 50% more intraepithelial nerves than the BSS or vehicle groups. Only HSmP-treated corneas improved the visual quality to near transparent. (4) Conclusions: These results suggest that HSmP facilitates the regeneration of the corneal epithelium and innervation, as well as restoring transparency and reducing myofibroblast scarring after laser experimental injury.
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Tatar, Mehmet Gurkan, Feride Aylin Kantarci, Aydin Yildirim, Haşim Uslu, Hatice Nur Colak, Hasan Goker, and Bulent Gurler. "Risk Factors in Post-LASIK Corneal Ectasia." Journal of Ophthalmology 2014 (2014): 1–4. http://dx.doi.org/10.1155/2014/204191.
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Purpose. To evaluate the risk factors for post-laser in situ keratomileusis (LASIK) ectasia.Materials and Methods. Medical records of 42 eyes of 28 (10 women, 18 men) patients who developed corneal ectasia after LASIK were retrospectively reviewed. Topographical features and surgical parameters of those patients were evaluated.Results. The mean age of patients was34.73±6.50(23–48) years and the mean interval from LASIK to the diagnosis of post-LASIK ectasia was36.0±16.92(12–60) months. The following factors were determined as a risk factors: deep ablation (>75 μm) in 10 eyes, FFK (forme fruste keratoconus) in 6 eyes, steep cornea (>47 D) in 3 eyes, pellucid marginal degeneration (PMD) in 2 eyes, thin cornea (<500 μm) in 2 eyes, thin and steep cornea in 2 eyes, thin cornea and deep ablation in 5 eyes, FFK and steep cornea in 2 eyes, and FFK, steep cornea, and deep ablation in 1 eye. However no risk factor has been determined in 9 eyes (21.4%).Conclusion. The findings of our study showed that most of the patients who developed post-LASIK ectasia have a risk factor for post-LASIK ectasia. However, the most common risk factor was deep ablation.
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Gelber, Tammy A., Kathleen Waltz, Corine R. Ghosn, Michael E. Stern, Beatrice Cochener, Lih-Huei L. Liaw, and Michael W. Berns. "Corneal wound healing following excimer laser ablation." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 10–11. http://dx.doi.org/10.1017/s0424820100145893.
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The excimer laser is currently being investigated in ophthalmology for refractive correction, including myopia, hyperopia and astigmatism. Laser photo ablation offers a consistent, precisely controllable method of tissue removal that potentially gives the surgeon more accurate control of surgical results than do conventional methods of corneal reshaping (i.e., diamond knives for radial keratotomy). In addition, there is interest in using laser photo ablation to smooth irregular corneal surfaces and to remove corneal stromal opacities. Early clinical studies have elucidated two problems common to refractive surgery. First, the cornea tends to develop a subepithelial haze approximately two weeks post-op in the ablation zone. In most cases this subsides during the ensuing six months. Second, the initial level of refractive correction reverses during the process of healing. This problem tends to be exaggerated in patients whose correction is greater than five diopters requiring a deeper ablation. Depending on the depth of the ablation, the epithelium, Bowman’s layer and the anterior stroma will be removed. The reparative process includes reepithelialization and the restoration of the stroma through the migration of keratocytes to the wound area. This is followed by the secretion of collagenases as well as new collagen and extracellular matrix (GAGs).
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Seiler, Theo, and Mohammad H. Dastjerdi. "Customized corneal ablation." Current Opinion in Ophthalmology 13, no. 4 (August 2002): 256–60. http://dx.doi.org/10.1097/00055735-200208000-00013.
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Kornilovskiy, I. M. "Riboflavin in the prevention of fibroplasia in laser refractive corneal surgery." Modern technologies in ophtalmology, no. 5 (September 30, 2022): 190–95. http://dx.doi.org/10.25276/2312-4911-2022-5-190-195.
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Purpose: To substantiate the use of riboflavin for the prevention of subepithelial and intrastromal fibroplasia in laser refractive corneal surgery. Material and methods: The work is based on 9-year clinical observations of the results of photorefractive and phototherapeutic corneal surgery with stroma saturation with riboflavin (more than 700 operations). Keratoablation was performed after drip, aerosol or combined saturation of the stroma with 0.1 % or 0.25 % chilled isotonic riboflavin solution. Corneal OCT was performed on RTVue 100 and RTVue XR100 devices. Keratotopographic and densitometric studies were performed on a TMS-5 instrument. These devices were used with two-wavelength optical scanning in the visible green and infrared ranges to assess prophylactic crosslinking by the change in the refractive index of the cornea. Results: During photokeratoablation, corneal stroma layers saturated with riboflavin acted as spectral filters, protecting keratocytes from secondary radiation induced by ablation. This reduced the response of aseptic inflammatory and regenerative reactions, the severity and duration of the corneal syndrome. According to OCT and corneal densitometry data, the formation of a Bowman-like structure on the ablation surface was noted with an increase in optical density in the underlying layers of the stroma. Two-wavelength optical scanning revealed a significant increase in the refractive index. The effect of laser-induced crosslinking and the increase in optical density had a damped character and did not exceed 1/2 of the stroma thickness. These changes in the cornea were a barrier between pro-inflammatory epithelial and stromal cytokines that stimulate the development of subepithelial and intrastromal fibroplasia after photokeratoablation. Conclusion. During photokeratoablation, riboflavin-saturated layers of the corneal stroma protect deeper-lying keratocytes from secondary radiation induced by ablation, and the formation of a Bowman-like structure on the ablation surface with a damping effect of crosslinking in the superficial layers of the stroma prevents the development of fibroplasia. Keywords: Riboflavin, Mitomycin-C, fibroplasia, photoablation, excimer laser corneal surgery, laser-induced crosslinking.
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Min, Ji Sang, Byung Moo Min, and Dong Cho Lee. "A New Corneal Remodeling Technique with Laser Asymmetric Keratectomy Using Semi-Cylindrical Ablation Pattern Reducing Regional Asymmetry of Corneal Thickness, Case Series." Journal of Ophthalmology & Clinical Research 9, no. 1 (July 4, 2022): 1–6. http://dx.doi.org/10.24966/ocr-8887/100091.
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Laser asymmetric keratectomy using semi-cylindrical ablation pattern (LAK-SCAP) is a new customized corneal remodeling method reducing regional asymmetry of corneal thickness, so could be to avoid and treat conventional laser refractive surgery adverse effects. Three eyes (3 patients) had laser epithelial keratomileusis (LASEK) linked LAK-SCAP (L-LAK-SCAP) to reduce regional asymmetry of corneal thickness and correct refractive errors. On Orbscan map, the cones of the corneas were located in the peripheral side, the corneal thickness imbalance was severe due to the sum of 4 direction differences in corneal thickness >80µm.
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Tian, Mingxia, Ping Ma, Guoying Mu, Lijing Chen, and Jie Feng. "Establishing a Porcine Eye Model for Manual Sub-Bowman Layer Photorefractive Keratomileusis." Journal of Ophthalmology 2020 (July 15, 2020): 1–6. http://dx.doi.org/10.1155/2020/9834760.
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Objective. To establish a porcine eye model for manual sub-Bowman layer photorefractive keratomileusis (SBPRK), which is a reformed surface ablation refractive surgery that results in preserving the corneal Bowman layer (BL). Methods. The SBPRK group consisted of eleven eyes of 8 healthy pigs with BL flaps by mechanical technique followed by laser ablation. Regarding the remaining 5 eyes, 3 random eyes had transepithelium photorefractive keratectomy (TransPRK) (the TransPRK group), while the other 2 eyes were untreated (the blank control group). All the pigs were followed up for 8 weeks. Slit-lamp biomicroscopy and optical coherence tomography (OCT) were examined before the surgeries and at 1 week, 4 weeks, and 8 weeks after the surgeries. Results. In a few days after the surgery, 3 eyes of the SBPRK group were excluded from the study because of poor healing of the corneal flaps. At the 1st postoperative week, one eye had an irregular defect of about 3 mm in the central corneal epithelium area; the cornea of the other 7 eyes had just light edema with intact epithelium just like the cornea of the TransPRK group. At the 4th week, in the SBPRK group, the cornea was slightly hazy (haze stage 1). While in the TransPRK group, the cornea was hazier (haze stage 2). At the 8th week, in the SBPRK group, both corneas were almost transparent, and the edges of the BL flaps could not be clearly seen. Meanwhile, in the TransPRK group, the corneal haze became lighter and thinner. OCT showed that, in the SBPRK group, there was high reflection in the BL layer, and it was obvious at 1 week postoperation, decreased at 4 weeks, and calmed down at 8 weeks. However, in the TransPRK group, the high reflection diffused in the anterior corneal stroma at 1 week postoperation, enhanced at 4 weeks, and weakened at 8 weeks. Conclusions. Preserving the BL while conducting surface refractive surgery may result in less haze than TransPRK. However, further study is still needed, and this technique still requires refining until it becomes a standard clinical procedure.
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Kornilovskiy, I. M., E. M. Kasimov, and A. I. Sultanova. "Features of inflammatory and regenerative reaction to excimer laser refractive keratectomy with photoprotection." Kazan medical journal 98, no. 1 (February 15, 2017): 53–57. http://dx.doi.org/10.17750/kmj2017-53.
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Aim. To study the features of inflammatory and regenerative reaction to excimer laser refractive keratectomy with photoprotection.Methods. Clinical cases of 560 excimer laser refractive keratectomies with photoprotection in 280 patients with myopia and myopic astigmatism of different severity. The observation period varied from 1 month to 2.5 years.Results. The study showed that intensity of aseptic inflammation and the type of regenerative response are influenced by the amount of evaporated corneal tissue, which correlates with the severity of myopia. Moreover, in case of equal severity of myopia and amount of evaporated tissue inflammatory and regenerative response was less prominent if excimer laser ablation was performed under the superficial corneal flap. In this case epithelial stromal corneal flap allowed reducing the negative effect of ultraviolet exposure and interaction between proinflammatory epithelial and stromal cytokines. At photorefractive ablation of corneal stroma saturated with 0.25% isotonic riboflavin solution aseptic inflammatory and regenerative response, intensity and duration of corneal syndrome decreased. Due to such technique of photorefractive keratectomy stromal layers saturated with riboflavin absorbed the secondary ultraviolet induced by ablation. Clinical observation demonstrated the need for additional photoprotection by glasses from external unltraviolet in all types of photorefractive surgeries on cornea up to full recovery of visual and optometric parameters. Use of photoprotection during excimer laser refractive ablation allowed achieving early stabilization of vision and refraction, decreasing the duration of postoperative steroidal and nonsteroidal anti-inflammatory drugs intake by one third in average.Conclusion. Local photoprotection with riboflavin during excimer laser refractive keratectomy and photoprotection by glasses from external ultraviolet reduce the risk of oxidative stress in the cornea, postoperative aseptic inflammatory and regenerative reactions, promote stabilization of visual, optic refractive parameters and improve their predictability.
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Meyer, Carsten H., Stefan Mennel, and Jörg C. Schmidt. "Acute Keratoconus-Like Hydrops after Laser In Situ Keratomileusis." Journal of Ophthalmology 2009 (2009): 1–3. http://dx.doi.org/10.1155/2009/363482.
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Purpose.To demonstrate keratoconus-like hydrops after laser in situ keratomileusis (LASIK) by optical coherence tomography (OCT).Patient and Methods.A 21-year-old man received uneventful bilateral LASIK. On slit lamp examination or corneal topography there were no signs of fruste keratoconus. The preoperative corneal thickness was 587-m OD and the calculated ablation for two treatments was 114-m. Uneventful LASIK with an optical zone of 7 mm and an ablation of 89-m OD, and an ablation of 73-m OS was performed. Three years postoperatively, he complained about progressive myopia and impaired vision OD. His VA was hand motion OD and 20/20 OS.Results.OCT and light microscopy revealed an anterior corneal steepening and acute keratoconus-like excessive edematous swelling.Conclusion.The cornea is mechanically weakened after LASIK by the lamellar cut and tissue subtraction. Although the advocated minimal residual stromal bed thickness is 250-m, it may not be adequate to prevent progressive keratoconus-like hydrops in the selected cases.
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Gatinel, Damien. "Reevaluating the Effectiveness of Corneal Collagen Cross-linking and Its True Biomechanical Effect in Human Eyes." International Journal of Keratoconus and Ectatic Corneal Diseases 6, no. 1 (June 2017): 34–41. http://dx.doi.org/10.5005/jp-journals-10025-1140.
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ABSTRACT The induction of cross-links in corneal tissue appears to be a promising technique to increase its stiffness and this has been the basis of treatment of keratoconus (KC) and corneal ectatic disease. However, there exists a striking discrepancy between the reported biomechanical effects of corneal collagen cross-linking (CXL) in vitro compared to in vivo, and this has not received much attention in the literature. Despite the documentation of an increase in corneal stiffness in vitro by many investigators, reports that provide evidence of measurable and consistent biomechanical changes in corneal rigidity in vivo after CXL are lacking. Indeed, the absence of documented in vivo biomechanical improvement in CXL-treated corneas is a conundrum, which needs to be further explored. To explain this discrepancy, it has been postulated that biomechanical changes induced by CXL are too subtle to be measured by currently available diagnostic tools or have characteristics not discernible by these technologies. However, the dynamic bidirectional applanation device (Ocular Response Analyzer) and dynamic Scheimpflug analyzer instruments (Corvis ST) have demonstrated the ability to quantify even subtle biomechanical differences in untreated KC corneas of different ectatic degree, and document the reduction in corneal hysteresis (CH) and corneal resistance factor (CRF) in situations where the corneal stiffness is reduced, such as after laser in situ keratomileusis and surface ablation procedures. It has also been possible to demonstrate an altered CH and CRF in patients with diabetes, smoking habit, glaucoma, Fuchs’ dystrophy, and corneal edema. It is puzzling that these diagnostic tools could document subtle biomechanical changes in these situations, yet fail to measure the purported changes induced by CXL on corneas with progressive KC. This failure to document significant and consistent biomechanical changes in corneal rigidity could suggest that CXL does not induce a simple reversal of the particular biomechanical deficits that characterize KC, or make the cornea significantly more resistant to bending forces as has been widely postulated. The absence of measurable biomechanical change in living KC corneas after CXL could be a consequence of biomechanical strengthening which is insignificant compared to the marked weakening caused by preexisting alteration of the collagen structure, disorganization of collagen fiber intertwining, and compromised structural–mechanical homogeneity that are hallmarks of keratoconic disease, especially in corneas with progressive KC. The changes in the cornea induced by CXL that have been described in vivo may instead be driven by a wound healing process in response to the removal of the corneal epithelial layer and subsequent exposure to riboflavin and ultraviolet-A (UVA). This paper will present evidence that sustains this hypothesis. How to cite this article Gatinel D. Reevaluating the Effectiveness of Corneal Collagen Cross-linking and Its True Biomechanical Effect in Human Eyes. Int J Kerat Ect Cor Dis 2017;6(1):34-41.
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Djotyan, Gagik P., Ron M. Kurtz, Delia Cabrera Ferna´ndez, and Tibor Juhasz. "An Analytically Solvable Model for Biomechanical Response of the Cornea to Refractive Surgery." Journal of Biomechanical Engineering 123, no. 5 (April 25, 2001): 440–45. http://dx.doi.org/10.1115/1.1388293.
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An analytically solvable model that considers the elasticity of the cornea is developed for use in the current and novel corneal refractive surgery procedures. The model assumes that the cornea is a thin spheroid shell with an elastic response to intraocular pressure. The value of the Young’s modulus of the post-operative cornea and its dependence on the geometric parameters of the ablation zone are estimated employing “best-fit” approach to nomograms currently used in corneal refractive surgery. These elasticity parameters are applied for quantitative modeling of different types of refractive surgery for myopia.
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Cagini, Carlo, Marco Messina, Marco Lupidi, Francesco Piccinelli, Tito Fiore, Daniela Fruttini, and Leopoldo Spadea. "Posterior Corneal Surface Stability after Femtosecond Laser-Assisted Keratomileusis." Journal of Ophthalmology 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/184850.
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The purpose of this study was to evaluate posterior corneal surface variation after femtosecond laser-assisted keratomileusis in patients with myopia and myopic astigmatism. Patients were evaluated by corneal tomography preoperatively and at 1, 6, and 12 months. We analyzed changes in the posterior corneal curvature, posterior corneal elevation, and anterior chamber depth. Moreover, we explored correlation between corneal ablation depth, residual corneal thickness, percentage of ablated corneal tissue, and preoperative corneal thickness. During follow-up, the posterior corneal surface did not have a significant forward corneal shift: no significant linear relationships emerged between the anterior displacement of the posterior corneal surface and corneal ablation depth, residual corneal thickness, or percentage of ablated corneal tissue.
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Damgaard, Iben Bach, Mohamed Reffat, and Jesper Hjortdal. "Review of Corneal Biomechanical Properties Following LASIK and SMILE for Myopia and Myopic Astigmatism." Open Ophthalmology Journal 12, no. 1 (July 27, 2018): 164–74. http://dx.doi.org/10.2174/1874364101812010164.
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Worldwide, femtosecond Laser AssistedIn-situKeratomileusis (LASIK) is a well known and commonly used refractive technique, although Small Incision Lenticule Extraction (SMILE) has become increasingly popular since it was introduced in 2011. In LASIK, a corneal flap is cut with a microkeratome or femtosecond laser, followed by thinning of the stromal bed with excimer laser ablation. In SMILE, a minor intrastromal lenticule is cut with a femtosecond laser and subsequently removed through a small incision, leaving the anterior and strongest part of the cornea almost intact. Both LASIK and SMILE require cutting of corneal lamellae that may reduce the biomechanical stability of the cornea, with the potential risk of corneal iatrogenic ectasia as a severe complication. However, SMILE preserves the anterior corneal integrity and may, in theory, better preserve the corneal biomechanical strength than LASIK after surgery.A review aimed to examine the current literature that describes and compares the corneal biomechanical properties after Laser AssistedIn-situKeratomileusis (LASIK) and Small Incision Lenticule Extraction (SMILE). A comprehensive search was performed in Pubmed.gov using the following search queries: Corneal biomechanical properties, corneal biomechanics, ocular response analyser, ocular response analyzer, ORA,ex vivo, in vitro, Corvis, Corvis ST, LASIK, and SMILE.
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Kornilovskiy, I. M. "A new look at photoprotection and crosslinking in excimer laser vision correction." Modern technologies in ophtalmology, no. 5 (October 20, 2021): 132–36. http://dx.doi.org/10.25276/2312-4911-2021-5-132-136.
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Purpose. To develop approaches to excimer laser keratorefractive surgery based on a new view of the photoprotective function of the cornea, ablation-induced secondary radiation, photoprotective and side effects of crosslinking. Material and methods. The literature data and our own 32-year clinical observations of complications in excimer laser vision correction, methods of their treatment and prevention have been analyzed. Particular emphasis was placed on the analysis of works on photoprotection and crosslinking in photorefractive surgery. New approaches to excimer laser keratorefractive surgery are based on studies on the use of riboflavin for photoprotection and laser-induced crosslinking in corneal ablation (598 operations). Corneal crosslinking was assessed by computed keratotopography, optical coherence tomography, and corneal densitometry. Long-term results were followed up to 8 years. Results. Complications in excimer laser refractive surgery were associated with the development of dry eye syndrome, the formation of subepithelial or intrastromal fibroplasia. Ablation-induced secondary radiation played an important role in the development of complications of excimer laser refractive surgery. It negatively affected keratocytes, nerves and increased oxidative stress in the cornea. To protect against secondary radiation, a new technology of keratoablation with 0.25% isotonic riboflavin solution has been developed. This reduced oxidative stress and aseptic inflammatory response. According to OCT and densitometric studies, a decaying effect of crosslinking with the formation of a membrane structure on the ablation surface was revealed. Local photoprotection during ablation with riboflavin and the effect of crosslinking in combination with postoperative spectacle spectral UV photoprotection accelerated the stabilization of optical-refractive and visual results, increased the photoprotective and strength properties of the thinned cornea. This reduced the risks of keratoectasia and earlier development of cataracts. Conclusion. A new look at photoprotection and crosslinking in excimer laser refractive surgery provides for keratoablation with riboflavin in combination with postoperative spectacle spectral photoprotection from external UV radiation. Key words: excimer laser refractive surgery, dry eye, fibroplasia, keratoectasia, riboflavin, photoprotection, crosslinking.
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Sultanova, A. I. "Riboflavin use as photoprotector in laser corneal refractive surgery." Kazan medical journal 97, no. 3 (June 15, 2016): 410–14. http://dx.doi.org/10.17750/kmj2016-410.
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The works of different authors on the role of riboflavin in the oxidative stress suppression in tissues and organs were analyzed. Experimental and clinical studies showed that the riboflavin (vitamin B2) has antioxidant properties and acts as a coenzyme for redox enzymes affecting the glutathione reduction. Russian scientists studies established a significant negative linear correlation between the level of malondialdehyde in blood serum and riboflavin consumption. Several studies showed that riboflavin deficiency affects the activity of antioxidant enzymes, including glucose peroxidase, superoxide dismutase and catalase, which leads to a reduction in tissue cells antioxidant potential. The riboflavin feasibility in laser refractive surgery is due to the development of oxidative stress in the cornea in response to the intervention and the need for its correction. In photorefractive corneal surgery, it is worsened by secondary ablation induced by ultraviolet radiation. Works of the last few years show that the oxidative effect of the radiation is attenuated when performing the excimer laser refractive ablation after presaturation of the stroma with riboflavin solution. Experimental studies showed that both drip and aerosol corneal saturation with 0.25% isotonic riboflavin solution does not affect the accuracy of excimer laser ablation of the corneal stroma. In the clinic, performing transepithelial photorefractive keratectomy with riboflavin photoprotection for myopia with astigmatism of varying degrees and without astigmatism minimized corneal syndrome, sterile inflammatory response. It accelerated epithelialization and was accompanied by early optometric indicators stabilization, which confirmed the feasibility of riboflavin use as photoprotector in laser corneal refractive surgery.
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Toropov, V. O., E. V. Kozina, and A. V. Toropov. "Features of intraoperative pachymetry in fractional laser keratomylosis of myopia by FemtoLASIK method." Modern technologies in ophtalmology, no. 5 (October 20, 2021): 165–68. http://dx.doi.org/10.25276/2312-4911-2021-5-165-168.
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Comparison of preoperative pachymetry with intraoperative pachymetry; evaluation of the features of intraoperative pachymetry during surgery, practical application. Material and methods. The analysis of the results of 58 operations for myopia by the FemtoLASIK method was carried out. Femtosecond laser is a Ziemer femtosecond laser. Refractive ablation – with a SCHWIND Amaris 750 S excimer laser with integrated OCP. Pachymetry was performed in the center of the cornea at the diagnostic stage and during the operation: before the formation of the flap, after the formation and removal of the flap, and after the completion of ablation. Results. It was statistically reliably revealed that intraoperative pachymetry during FemtoLASIK differs from the planned one. The regularity is associated with the process of hydration of the corneal stroma during vacuum fixation of a femtosecond laser and with the process of dehydration during laser ablation. Conclusion. The obtained results allow us to speak about step-by-step control of the corneal thickness during FemtoLASIK and comparison of the planned parameters with those measured during the operation, as a way to timely detect deviations from the operation plan and, as a result, reduce the risk of pathological corneal thinning. In cases where the values of the corneal thickness in the central zone before the operation and the flap thickness correspond to the preoperative plan, the discrepancy between the planned RST indicator and its actual measured value during the operation is not critical. Key words: FemtoLASIK, intraoperative pachymetry, residual thickness of the stromal bed, hydration, corneal dehydration.
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Tomoyose, Katsuo, Yuka Okada, Takayoshi Sumioka, Masayasu Miyajima, Kathleen C. Flanders, Kumi Shirai, Tomoya Morii, Peter S. Reinach, Osamu Yamanaka, and Shizuya Saika. "Suppression ofIn VivoNeovascularization by the Loss of TRPV1 in Mouse Cornea." Journal of Ophthalmology 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/706404.
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To investigate the effects of loss of transient receptor potential vanilloid receptor 1 (TRPV1) on the development of neovascularization in corneal stroma in mice. Blocking TRPV1 receptor did not affect VEGF-dependent neovascularization in cell culture. Lacking TRPV1 inhibited neovascularization in corneal stroma following cauterization. Immunohistochemistry showed that immunoreactivity for active form of TGFβ1 and VEGF was detected in subepithelial stroma at the site of cauterization in both genotypes of mice, but the immunoreactivity seemed less marked in mice lacking TRPV1. mRNA expression of VEGF and TGFβ1 in a mouse cornea was suppressed by the loss of TRPV1. TRPV1 gene ablation did not affect invasion of neutrophils and macrophage in a cauterized mouse cornea. Blocking TRPV1 signal does not affect angiogenic effects by HUVECsin vitro. TRPV1 signal is, however, involved in expression of angiogenic growth factors in a cauterized mouse cornea and is required for neovascularization in the corneal stromain vivo.
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Mikhailov, P. P., E. V. Kudryashova, and A. N. Kulikov. "Prediction of refractive shift in the phototherapeutic keratectomy on the example of a patient with subepithelial mucinous corneal dystrophy." Modern technologies in ophtalmology, no. 5 (September 30, 2022): 201–10. http://dx.doi.org/10.25276/2312-4911-2022-5-201-210.
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Purpose. To present the treatment results of a patient with subepithelial mucinous corneal dystrophy by phototherapeutic keratectomy (PTK) using the excimer-laser system WaveLight EX500 (Alcon, USA) taking into account the induced myopic refractive shift. Material and methods. Patient S., 67 years old, with subepithelial mucinous corneal dystrophy and compound hyperopic astigmatism of both eyes. To determine the possibility of surgical treatment, in addition to the general ophthalmological examination, there were performed: optical coherence tomography (OCT) of the cornea to evaluate the total corneal thickness and the opacity depth; Corneal topography to evaluate total corneal refractive power and maximal anterior refractive power. FTK calculations were made basing on OCT data considering clinical refraction. The follow-up period was 3 months. Results. As a result of treatment, the corneal transparency of both eyes was restored. The ablation of the left eye corneal stroma with the standard PTK protocol to a 90-micron depth caused an increase in the patient’s refractive power by 3.87 D in spherical equivalent, which led to excessive myopic refraction. When performing PTK on the right eye, decrease of the ablation depth to 80-micron, as well as the two-stage formation of the anterior corneal profile with the formation of its wider «base» and a smaller optical zone diameter led to less refractive power increase of 2.62 D in spherical equivalent, which caused an emmetropic refraction in this case. Conclusion. The presented clinical case shows that various protocols for PTK implementation in patients with superficial corneal opacities can make it possible to not only achieve corneal transparency, but also to control the refractive shift and to define the final clinical refraction. Keywords: corneal dystrophy, phototherapeutic keratectomy (PTK), refractive surgery.
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Du, Ruirui, Lihua Fang, Yinyu Song, Xingming Tao, and Luchao Lin. "Effects of intraocular pressure and aspheric transition zone ablation profile on corneal biomechanics after conventional refractive surgery." E3S Web of Conferences 271 (2021): 03040. http://dx.doi.org/10.1051/e3sconf/202127103040.
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Our Purpose is to study the effects of intraocular pressure (IOP) and aspheric transition zone (ATZ) on corneal biomechanics after pure hyperopia correction by using the finite element analysis (FEA). The values of IOP were changed, and 1-5# aspheric transition zones were designed in 1-5D hyperopia correction model. Simulate and calculate the wavefront aberration, stress and vertex displacement of cornea. The results show that with the increase of IOP and diopter, defocus increases positively and sphere increases negatively. Diopter and IOP have slight influence on coma. At 22mmHg, the maximum value of defocus was 1.367mm at 5D-1#, and the maximum value of sphere was -0.32mm at 5D-5#. IOP and diopter have great influence on the stress in the marginal region of the anterior corneal surface, and 1D-1 # has the maximum value at 22mmHg. With the increase of IOP and diopter, the vertex displacement of posterior corneal surface increased. The ATZ ablation profile has little effects on the wavefront aberration and displacement. We can draw a conclusion that refractive surgery destroys the physiological structure of cornea and has a great influence on the biomechanical properties of cornea. IOP plays an important role in maintaining the physiological structure of cornea.
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Knezović, Igor, and Sara Djurić. "Decentered Individualized Sphero-Cylindrical (DISC) Ablation and Corneal Crosslinking in Patient with Progressive Keratoconus." Case Reports in Ophthalmological Medicine 2022 (July 21, 2022): 1–5. http://dx.doi.org/10.1155/2022/1839848.
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Aim. To report a new method with which we have treated a 29-year-old patient with keratoconus and progressive bilateral visual loss during the past few years. Methods. The patient underwent inferotemporal decentered individualized sphero-cylindrical (DISC) ablation and crosslinking (CXL) of the left eye. After administration of topical anesthetic, the patient was subjected to phototherapeutic keratectomy (PTK) laser ablation of the central 7.0 mm optical zone with 50 μm depth of epithelial ablation. To avoid the possible outcome of corneal haze, 0.02% mitomycin C (MMC) was applied to the stromal surface for 40 seconds. Riboflavin 0.1% solution was then administered topically every 2 minutes for a 30-minute period followed by 5 cycles of corneal crosslinking, radiating with UV-A at 3 mW/cm2, for a duration of 5 minutes. Results. 17 months postoperative, there was an impressive improvement in uncorrected distance visual acuity, and the cornea became more regular. Results of Fourier’s analysis imply a drop of irregularity (-28.6% two months and –63% seventeen months postoperative), Zernike analysis revealed a decrease of higher order aberrations (spheric and comatic aberrations), and corneal index values in the 8 mm zone (IHD, ISV, and IVA) became lower, compared to the preoperative values. Conclusion. It is possible to obtain better outcome of visual function with DISC ablation through an individual approach compared to CXL solely. This approach might be a promising strategy in retrieving impaired vision in patients suffering from keratoconus.
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Alekseev, V. A., V. G. Kostin, A. V. Usoltseva, V. P. Usoltsev, and S. I. Yuran. "Expanding of Excimer Laser Photoablation’s Functionality in Ophthalmology." Devices and Methods of Measurements 12, no. 3 (October 15, 2021): 175–82. http://dx.doi.org/10.21122/2220-9506-2021-12-3-175-182.
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One of the significant weaknesses of excimer laser-based vision correction devices is the difficulty of achieving a required change in the refractive properties of the cornea to sharply focus the image on the retina with distance from the working area (ablation zone) center to the periphery due to a change in the laser beam incidence angle. The study is aimed at improving the quality of laser action on the eye cornea by introducing an optical corrective system into the existing excimer laser vision correction equipment, ensuring the coincidence of the direction of the laser beam incidence on the corneal surface with the normal.It has been shown that the greater the reflection coefficient, the lower the absorbed energy, and the shallower the laser radiation penetration and ablation depths, which reduces the laser action opportunities and quality. When using excimer laser vision correction devices, it has been proposed to change the angle of the laser beam incidence on the cornea with a distance from the working area (ablation zone) center to the periphery during the surgery by introducing an optical corrective system based on a lightweight controllable and movable mirror, which allows achieving the coincidence of the direction of the laser beam incidence on the corneal surface with the normal.The studies have shown that the coincidence of the laser beam incidence on the corneal surface at any point with the normal when using a priori data on the specifics of the patient's eye allows expanding the functional opportunities of excimer laser photoablation, i. e., expand the ablation zone by 30 % and eliminate the possibility of errors caused by the human factor. The technique proposed can be used for excimer laser vision correction according to PRK, LASIK, Femto-LASIK, and other methods. To implement this approach, a patented excimer laser vision correction unit has been proposed with a PCcontrolled optical shaping system comprising galvo motor platforms and galvo mirrors installed on them.
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Kim, Alisa, and Roy S. Chuck. "Wavefront-guided customized corneal ablation." Current Opinion in Ophthalmology 19, no. 4 (July 2008): 314–20. http://dx.doi.org/10.1097/icu.0b013e328302ccae.
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Li, Liang-Mao, Li-Quan Zhao, Ling-Hui Qu, and Peng Li. "Excimer Laser Phototherapeutic Keratectomy for the Treatment of Clinically Presumed Fungal Keratitis." Journal of Ophthalmology 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/963287.
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This retrospective study was to evaluate treatment outcomes of excimer laser phototherapeutic keratectomy (PTK) for clinically presumed fungal keratitis. Forty-seven eyes of 47 consecutive patients underwent manual superficial debridement and PTK. All corneal lesions were located in the anterior stroma and were resistant to medication therapy for at least one week. Data were collected by a retrospective chart review with at least six months of follow-up data available. After PTK, infected corneal lesions were completely removed and the clinical symptoms resolved in 41 cases (87.2%). The mean ablation depth was114.39±45.51 μm and diameter of ablation was4.06±1.07 mm. The mean time for healing of the epithelial defect was8.8±5.6days. Thirty-four eyes (82.9%) showed an improvement in best spectacle-corrected visual acuity of two or more lines. PTK complications included mild to moderate corneal haze, hyperopic shift, irregular astigmatism, and thinning cornea. Six eyes (12.8%) still showed progressed infection, and conjunctival flap covering, amniotic membrane transplantation, or penetrating keratoplasty were given. PTK is a valuable therapeutic alternative for superficial infectious keratitis. It can effectively eradicate lesions, hasten reepithelialization, and restore and preserve useful visual function. However, the selection of surgery candidates should be conducted carefully.
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M, Hosny. "Comparing Corneal OCT Findings in High Irradiance Corneal Crosslinking Combined with Femtosecond Laser In Situ Keratomileusis versus Femtosecond Laser In Situ Keratomileusis." Open Access Journal of Ophthalmology 6, no. 1 (January 4, 2021): 1–12. http://dx.doi.org/10.23880/oajo-16000209.
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Objective: To study Corneal OCT findings in the interface and the demarcation line under or over the interface in patients that undergo Femtosecond laser in situ Keratomeulisis compared to patients that undergo Femtosecond laser in situ Keratomeulisis combined with high irradiance corneal cross linking (Femto-Lasik Xtra). Study Design: Prospective Randomized Comparative Study. Methods: Our study included 40 eyes of 20 patients divided into 2 groups, a group of 10 patients with 20 eyes underwent Femto-Lasik & the other group of 10 patients of 20 eyes underwent Femto-Lasik Xtra. The Femto Lasik procedure was done using Alcon Wave Light FS200 laser machine. The Femto-Lasik XTRA procedure entails the administration of half fluence high irradiance cross-linking subsequent to refractive correction. A higher concentration 0.25% riboflavin is applied on the stromal bed and the flap subsequent to laser ablation with a soak time of 90 seconds, UV-A irradiance is delivered as a homogenous beam of 30 mW/cm2 for 90 s to deliver a total fluence of 2.7J/cm2. Patients were randomly observed and HEIDELBERG ASOCT was performed after 1 week, 1 month & 3 months post-operative. Results: A demarcation line was noted in femto Lasik Xtra patients, appeared more evident in the peripheral cornea and faded as it approached the central cornea. It became less evident after 1 month and 3 months period respectively. Also the flap hinge was more hyper reflective and evident in femto Lasik Xtra patients when compared to femto Lasik patients. Anterior crosslinked stroma appeared more hyper reflective than posterior stroma in femto Lasik Xtra patients. Flap edge was also more hyper reflective and better demarked in femto Lasik Xtra treated corneas when compared to femto Lasik treated corneas. Conclusion: AS-OCT showed significant differences between femto Lasik and Femto Lasik Xtra treated corneas. Significant changes were noted in the demarcation line in Femto Lasik Xtra patients along different time periods post-operative.
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Hjortdal, Jesper, and Anders Ivarsen. "New Developments in the Lenticule Extraction Procedure." US Ophthalmic Review 07, no. 01 (2014): 20. http://dx.doi.org/10.17925/usor.2014.07.01.20.
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For the last 20 years controlled excimer laser ablation of corneal tissue, either directly from the corneal stromal surface or from the corneal interior after creation of a superficial corneal flap, has become widely used to correct myopia, hyperopia, and astigmatism. Recently, an intrastromal refractive procedure whereby a tissue lenticule is cut free in the corneal stroma by a femtosecond laser and removed through a small peripheral incision has been introduced. The procedure avoids creation of a corneal flap and the potential associated risks while avoiding the slow visual recovery of surface ablation procedures. The all-femtosecond-based flap-free intracorneal refractive procedure has been documented to be a predictable, efficient, and safe procedure for correction of myopia and astigmatism. Technologic developments related to further improved cutting quality, hyperopic, and individualized treatments are desirable.
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Hjortdal, Jesper, and Anders Ivarsen. "New Developments in the Lenticule Extraction Procedure." European Ophthalmic Review 08, no. 01 (2014): 31. http://dx.doi.org/10.17925/eor.2014.08.01.31.
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For the last 20 years controlled excimer laser ablation of corneal tissue, either directly from the corneal stromal surface or from the corneal interior after creation of a superficial corneal flap, has become widely used to correct myopia, hyperopia and astigmatism. Recently, an intrastromal refractive procedure whereby a tissue lenticule is cut free in the corneal stroma by a femtosecond laser and removed through a small peripheral incision has been introduced. The procedure avoids creation of a corneal flap and the potential associated risks while avoiding the slow visual recovery of surface ablation procedures. The all-femtosecond-based flap-free intracorneal refractive procedure has been documented to be a predictable, efficient and safe procedure for correction of myopia and astigmatism. Technological developments related to further improved cutting quality, hyperopic and individualised treatments are desirable.
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Zhu, Yirui, Yanzhi Zhao, Yubao Zhang, Hongwei Yang, Jiulin Shi, Hongling Cai, Dong Zhang, Guofu Huang, Xingdao He, and Xiaoshan Wu. "In Vivo Evaluation of the Effects of SMILE with Different Amounts of Stromal Ablation on Corneal Biomechanics by Optical Coherence Elastography." Diagnostics 13, no. 1 (December 22, 2022): 30. http://dx.doi.org/10.3390/diagnostics13010030.
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This work aims to depth-resolved quantitatively analyze the effect of different stromal ablation amounts on the corneal biomechanical properties during small incision lenticule extraction (SMILE) using optical coherence elastography (OCE). A 4.5-MHz ultrasonic transducer was used to excite elastic waves in the corneal tissue. The OCE system combined with the antisymmetric Lamb wave model was employed to achieve a high-resolution, high-sensitivity, and depth-resolved quantitative detection of the corneal Young’s modulus. Eighteen rabbits were randomly divided into three groups; each group had six rabbits. The first and second groups underwent -3D and -6D SMILE surgeries, and the third group was the control group, respectively. Young’s modulus of the corneal cap and residual stromal bed (RSB) were both increased after SMILE, which shared the stress under intraocular pressure (IOP). Furthermore, the Young’s modulus of both the corneal cap and RSB after 3D SMILE group were significantly lower than that in the -6D group, which indicated that the increases in the post-operative corneal Young’s modulus were positively correlated with the amount of stromal ablation. The OCE system for quantitative spatial characterization of corneal biomechanical properties can provide useful information on the extent of safe ablation for SMILE procedures.
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Paley, Grace L., Roy S. Chuck, and Linda M. Tsai. "Corneal-Based Surgical Presbyopic Therapies and Their Application in Pseudophakic Patients." Journal of Ophthalmology 2016 (2016): 1–6. http://dx.doi.org/10.1155/2016/5263870.
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Purpose. The purpose of this review is to provide a summary of laser refractive surgery and corneal inlay approaches to treat presbyopia in patients after cataract surgery.Summary. The presbyopic population is growing rapidly along with increasing demands for spectacle independence. This review will focus on the corneal-based surgical options to address presbyopia including various types of corneal intrastromal inlays and laser ablation techniques to generate either a multifocal cornea (“PresbyLASIK”) or monovision. The natural history of presbyopia develops prior to cataracts, and these presbyopic surgeries have been largely studied in phakic patients. Nevertheless, pseudophakic patients may also undergo these presbyopia-compensating procedures for enhanced quality of life. This review examines the published reports that apply these technologies to patients after cataract surgery and discusses unique considerations for this population.
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Ventura, Bruna V., Haroldo V. Moraes, Newton Kara-Junior, and Marcony R. Santhiago. "Role of Optical Coherence Tomography on Corneal Surface Laser Ablation." Journal of Ophthalmology 2012 (2012): 1–6. http://dx.doi.org/10.1155/2012/676740.
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This paper focuses on reviewing the roles of optical coherence tomography (OCT) on corneal surface laser ablation procedures. OCT is an optical imaging modality that uses low-coherence interferometry to provide noninvasive cross-sectional imaging of tissue microstructurein vivo.There are two types of OCTs, each with transverse and axial spatial resolutions of a few micrometers: the time-domain and the fourier-domain OCTs. Both have been increasingly used by refractive surgeons and have specific advantages. Which of the current imaging instruments is a better choice depends on the specific application. In laserin situkeratomileusis (LASIK) and in excimer laser phototherapeutic keratectomy (PTK), OCT can be used to assess corneal characteristics and guide treatment decisions. OCT accurately measures central corneal thickness, evaluates the regularity of LASIK flaps, and quantifies flap and residual stromal bed thickness. When evaluating the ablation depth accuracy by subtracting preoperative from postoperative measurements, OCT pachymetry correlates well with laser ablation settings. In addition, OCT can be used to provide precise information on the morphology and depth of corneal pathologic abnormalities, such as corneal degenerations, dystrophies, and opacities, correlating with histopathologic findings.
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Jung, Seok Won, Min Jung Kim, Shin Hae Park, and Choun-Ki Joo. "Multifocal Corneal Ablation for Hyperopic Presbyopes." Journal of Refractive Surgery 24, no. 9 (November 1, 2008): 903–10. http://dx.doi.org/10.3928/1081597x-20081101-09.
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Argento, Carlos, and María José Cosentino. "Customized ablation for asymmetrical corneal astigmatism." Journal of Cataract & Refractive Surgery 27, no. 6 (June 2001): 891–95. http://dx.doi.org/10.1016/s0886-3350(01)00874-4.
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Singh, Daljit. "Ablation Pit Treatment For Corneal Decompensation." Annals of Ophthalmology 38, no. 1 (2006): 21–24. http://dx.doi.org/10.1385/ao:38:1:21.
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Zhang, Yu, Lin Lin, Yirui Zhu, Shuo Yang, and Xiaodan Huang. "Long-Term Clinical Outcome of Low-Temperature Plasma Ablation Treatment for Recurrent Corneal Erosions." Journal of Clinical Medicine 11, no. 21 (October 25, 2022): 6280. http://dx.doi.org/10.3390/jcm11216280.
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Purpose: To observe the therapeutic effect of low-temperature plasma ablation in treating patients with recurrent corneal erosions (RCEs). Materials and Methods: From 2020 to 2022, 35 participants with unilateral RCEs voluntarily enrolled. Here, 35 eyes of 35 patients were treated with low-temperature plasma ablation (coblation). All surgeries were performed by the same doctor (X.H.). The coblation went back and forth over the entire erosion area around five times for about five minutes. After the operation, patients were scheduled for follow-up visits at the outpatient clinic after 1 month, 3 months, 6 months, and 12 months, and at the end of the trial. During every visit, each patient underwent an evaluation of their ocular symptoms utilizing the following: pain score, intraocular pressure, slit lamp biomicroscopic examination, dry eye analysis, corneal topography, and corneal in vivo confocal microscopy (IVCM). Results: The mean follow-up time was 12.4 ± 6.1 months, ranging from 6 to 29 months. Of the 35 patients who had low-temperature plasma ablation, 32 eyes (91.43%) were completely symptom-free and three (8.57%) eyes had repeated episodes of recurrent corneal erosions after the surgery, at 3, 10, and 12 months, respectively. The typical RCE morphologic abnormalities observed in IVCM included the deformation and relaxation of the corneal epithelium, disorganized stromal fibers, reduced nerve fiber density, and disordered organization. After low-temperature plasma ablation, the loose cysts disappeared, and the epithelium became solid and tight. There was no obvious difference in the intraocular pressure (p = 0.090) or corneal astigmatism (p = 0.175) before and after treatment. The mean pain score decreased significantly, with a preoperative score of 7.7 ± 2.4 and postoperative score of 1.1 ± 1.8 (p < 0.001). The mean corneal thickness decreased from 562.6 ± 42.2 mm to 549.6 ± 26.9 mm (p = 0.031). The mean non-invasive keratograph tear meniscus height (NIKTMH) decreased from 0.210 ± 0.054 mm to 0.208 ± 0.045 mm (p = 0.001), and the mean TBUT decreased from 6.191 ± 2.811 s to 5.815 ± 2.802 s (p < 0.001), which manifested as a slight worsening of dry eyes. In one case, the patient’s corneal astigmatism became more severe, which may be related to the high instantaneous energy when the operation did not flush in a timely manner, and it was recovered after 6 months. Conclusion: Low-temperature plasma ablation is an effective and safe procedure to treat patients with recurrent corneal erosions.
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Anera, Rosario G., César Villa, José R. Jiménez, Ramón Gutiérrez, and Luis Jiménez del Barco. "Differences between real and predicted corneal shapes after aspherical corneal ablation." Applied Optics 44, no. 21 (July 20, 2005): 4528. http://dx.doi.org/10.1364/ao.44.004528.
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Kolenko, O. V., S. A. Shishkin, I. V. Dutchin, and E. L. Sorokin. "Study of incidence of clinically thin cornea in patients with moderate and high myopia who applied for keratorefractive surgery." Modern technologies in ophtalmology, no. 5 (September 30, 2022): 17–23. http://dx.doi.org/10.25276/2312-4911-2022-5-17-23.
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Purpose. To assess frequency of occurrence patients with insufficient thickness of optical zone of cornea for complete elimination of myopic refraction using FemtoLASIK technology. Material and methods. By random sampling, 100 patients (200 eyes) were selected with varying degrees of myopia who planned refractive surgery using the FemtoLASIK or Smile technology. The selection criterion was presence the prognosis of residual myopia in eyes due to the inability to fulfill the required ablation depth of the optical zone. The share of such patients in the total population of selected patients, their gender, age, magnitude of residual myopic refraction were found out. Results. According to results of the study in 88 patients (176 eyes, 88 %) thickness of optical zone of cornea made it possible to completely eliminate the existing myopic refraction) using the FemtoLASIK or Smile technology. In 12 patients (24 eyes, 12 %) thickness of optical zone of cornea did not made it possible to completely eliminate myopic refraction, without critical thinning of the stromal bed of cornea. The predicted residual myopia in these eyes ranged from –1.0 to –2.5 diopters. Photorefractive keratectomy technology was offered to these patients, which was agreed by 8 patients (16 eyes). Conclusion. The obtained data revealed the high relevance of the development of femtolaser refractive surgery technology, which provides for the complete elimination of myopic refraction in such patients by reducing the thickness of the corneal surface valve and, accordingly, increasing the thickness of the stromal bed. Keywords: refractive surgery, residual myopia, ablation depth, FemtoLASIK, corneal surface valve, residual stromal bed thickness.
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Doga, A. V., I. A. Mushkova, A. N. Karimova, and E. V. Kechin. "In Vivo Histomorphologic Structure of Cornea after FemtoLASIK Using Various Femtosecond Laser Systems." Ophthalmology in Russia 15, no. 3 (October 5, 2018): 264–72. http://dx.doi.org/10.18008/1816-5095-2018-3-264-272.
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Purpose:to compare in vivo histomorphologic structure of cornea after the FemtoLASIK procedure using femtolaser systems Femto Visum (Russia) and Femto LDV Z6 (Switzerland).Patients and methods:The study was carried for 70 eyes from 70 patients with low to moderate myopia after FemtoLASIK procedure. Group 1 (Femto Visum) included 36 eyes (n = 36) there the flap were formed using femtolaser Femto Visum («Optosystems», Russia), group 2 (Femto LDV Z6) included 34 eyes (n = 34) and Femto LDV Z6 was used («Ziemer Ophthalmic Systems AG», Switzerland). The excimer laser ablation was performed with Microscan Visum system («Optosystems», Russia) in both groups. The Femto Visum and Femto LDV Z6 groups were comparable in terms of pre-operative data (age, sex, corneal curvature, central corneal thickness, sphere, cylinder, spherical equivalent) (p > 0.05). In vivo histomorphological structure of the cornea was examined using confocal microscope Confoscan 4 (Nidek, Japan) 1 week, 1, 3, 6, and 12 months after FemtoLASIK. The endothelial cell density (ECD) was measured with endothelial microscope (EM-3000, Tomey, Japan) before surgery and 12 months after FemtoLASIK.Results:The main in vivo histomorphological cornea changes occurred in the anterior and middle layers of the corneal stroma during post-operative period in both groups (Femto Visum and Femto LDV Z6). The underlying corneal structures remained intact. There was no statistically significant difference between the two groups (p > 0.05). Twelve months postoperatively, the loss of ECD was 0.31 % in the Femto Visum group and 0.33 % in the Femto LDV Z6 group (p > 0,05).Conclusions:FemtoLASIK procedures using Femto Visum (Russia) and Femto LDV Z6 (Switzerland) lead to similar histomorphological cornea changes in post-operative period (p > 0.05) and they are safe for corneal structure in the treatment of myopia.
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Kornilovskiy, I. M. "Photoablation with riboflavin as an alternative to the application of Mitomycin-C in excimer laser corneal surgery." POINT OF VIEW. EAST – WEST, no. 2 (May 31, 2021): 24–27. http://dx.doi.org/10.25276/2410-1257-2021-2-24-27.
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Purpose. To substantiate the advantages of photoablation with riboflavin as an alternative to the use of Mitomycin-C in excimer laser surgery of the cornea. Material and methods. The work is based on clinical observations of the results of 598 photorefractive and phototherapeutic operations. In all cases, keratoablation was performed after drip, aerosol, or combined saturation of the stroma with 0.1% or 0.25% isotonic riboflavin solution. Corneal OCT was performed on RTVue 100 and RTVue XR100 devices. Keratotopographic and densitometric studies were performed on a TMS-5 device. Results. With photokeratoablation of the stroma saturated with riboflavin, the response aseptic inflammatory and regenerative reactions, the severity and duration of the corneal syndrome decreased. In densitometry and OCT studies, an increase in optical density was noted with the formation of a membrane structure on the ablation surface and the effect of cross-linking in the stromal layers adjacent to the ablation zone. Shielding of induced secondary radiation by riboflavin and the formation of a Bowman-like membrane structure made it possible to avoid the development of an irreversible form of fibroplasia and a decrease in visual acuity. The formed membrane structure with cross-linking in the underlying stromal layers was a barrier between pro-inflammatory epithelial and stromal cytokines, which predetermine the development of fibroplasia during photokeratoablation. Conclusion. Photokeratoablation with riboflavin prevents the development of an irreversible form of fibroplasia and can be considered as an alternative to the use of Mitomycin-C in photorefractive and phototherapeutic operations on the cornea by radiation from an argon-fluorine excimer laser. Key words: Mitomycin-C, riboflavin, fibroplasia, excimer laser corneal surgery, laser-induced crosslinking.
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Hahn, D. W., M. N. Ediger, and G. H. Pettit. "Dynamics of ablation plume particles generated during excimer laser corneal ablation." Lasers in Surgery and Medicine 16, no. 4 (1995): 384–89. http://dx.doi.org/10.1002/lsm.1900160410.
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Shimmick, John K., William B. Telfair, Charles R. Munnerlyn, Jimmy D. Bartlett, and Stephen L. Trokel. "Corneal Ablation Profilometry and Steep Central Islands." Journal of Refractive Surgery 13, no. 3 (May 1997): 235–45. http://dx.doi.org/10.3928/1081-597x-19970501-09.
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Merchea, Mohan. "Customized Corneal Ablation: the Quest for Supervision." Optometry and Vision Science 78, no. 11 (November 2001): 780–81. http://dx.doi.org/10.1097/00006324-200111000-00006.
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Raasch, T., and R. Applegate. "TOTAL REFRACTIVE MAPPING FOR CUSTOMIZED CORNEAL ABLATION." Optometry and Vision Science 75, no. 12 (December 1998): 68–73. http://dx.doi.org/10.1097/00006324-199812000-00029.
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Raasch, T., and R. Applegate. "TOTAL REFRACTIVE MAPPING FOR CUSTOMIZED CORNEAL ABLATION." Optometry and Vision Science 75, Supplement (December 1998): 68–73. http://dx.doi.org/10.1097/00006324-199812001-00029.
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Dougherty, Paul J., Kent L. Wellish, and Robert K. Maloney. "Excimer Laser Ablation Rate and Corneal Hydration." American Journal of Ophthalmology 118, no. 2 (August 1994): 169–76. http://dx.doi.org/10.1016/s0002-9394(14)72896-x.
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Woreta, Fasika A., Gavin W. Davis, and Kraig S. Bower. "LASIK and surface ablation in corneal dystrophies." Survey of Ophthalmology 60, no. 2 (March 2015): 115–22. http://dx.doi.org/10.1016/j.survophthal.2014.08.003.
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