Advanced Orthokeratology (ok): Clinical And Topographic Changes After Ok

Résumé: Orthokeratology is a technique that temporarily reduces myopia by wearing overnight reverse geometry rigid contact lenses, which reshape the corneal epithelium in a predictable, temporary, and reversible manner. The remodeling is done thanks to the special geometry of these lenses made to measure according to the corneal topographic data of the patient. The aim of the research reported in this thesis is to develop a greater understanding of the clinical and corneal topographic response to OK lenses, to report the current practice in our country, a further aim of this study is to identify influential lens parameters in existing and customized OK lens designs on corneal topography and axial length elongation over time. The first chapter is a literature review of orthokeratology which include a general perspective of lens designs and fitting process. A retrospective statistical study was carried out in Algeria to report the practice of orthokeratology, to investigate the visual function results, safety, and subjective responses with this technique in myopes. The third chapter represent the corneal topographic changes after orthokeratology to quantify the amount of both mid-peripheral curvature steepening and total refractive power change. The next chapter analyzed and compared treatment zone diameter, location and amount of maximum defocus and pupil size with orthokeratology, finally customized lens design was analyzed, corneal changes and axial length were followed over time to investigate the stability correlated with myopia. The use of orthokeratology in 48 young myopes in Algeria was reported to be safe as no serious complication were observed with a high success rate for first lens fitting. The results are promising and encourage to use orthokeratology in the region. With OK lenses, the amount of mid-peripheral power change and tangential topographical curvature change were ?0.75D and ?4.00D, respectively. Centrally and temporally only, did they vary significantly with initial spherical refractive error, the results from this study should provide valuable insights into the topographic and refractive changes occurring with orthokeratology which may aid in the design of soft lenses to control myopia. The maximum mid-peripheral steepening was found to be outside of the pupil, especially in high illumination condition, the results from this study provide additional information into the size of the treatment area and refractive changes found at the point of maximum defocus occurring with orthokeratology when used for the slowing of myopia progression. Customized OK lens designs give a small treatment zone diameter and powerful mid-peripheral annulus, the corneal topographic changes trend to decrease over time by slight amount and axial length is better controlled, future Orthokeratology and Myopia control studies must take into account this stability of topographic changes over time.

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