Optimisation of corneal biomechanical characteristics in orthokeratology for myopia control

Abstract

The rapid increase in myopia prevalence has escalated a wealth of research interest in the prevention mechanisms of myopia. Orthokeratology (ortho-k) is among the most promising approaches. A reluctance to employ this modality has been observed, owing to the selective treatment outcome and the long-term effects to the corneal tissue. This thesis investigates the attitudes of clinicians towards various myopia control interventions, including ortho-k within a cross-sectional internet-based survey; long-term effects of ortho-k lens wear on corneal biomechanical properties in myopic school-children over a two year period; short-term corneal biomechanical changes over the first 7 nights of lens wear; and the influence of factors (age, ethnicity, eye/body size and nutrition) on corneal biomechanical properties in healthy adults. The aim of this thesis is to aid a deeper understanding of the role of corneal biomechanical properties in ortho-k lens wear,specifically for myopia control. The findings within the thesis demonstrate that surveyed eye-care practitioners are aware of the scientific findings within the field of myopia control; two thirds would still prescribe single vision glasses to their patients, owing to a lack of clear guidelines and the selective treatment outcome. Results of the ortho-k studies suggest that the corneal biomechanical characteristics are affected by long term ortho-k wear, having a stabilising effect to the components of the anterior eye in progressing myopia. Short term ortho- k lens wear study reveals marked changes in corneal biomechanical parameters within the first seven nights of lens wear. Ortho-k itself and the anterior segment changes observed cannot explain all the variation in treatment response. The final study demonstrates the relationship between corneal biomechanical parameters and nutrition, ocular biometry and body size, suggesting that individual factors, although non-substantially, contribute towards the treatment outcome. It, is therefore, suggested to establish an internationally acknowledged guideline for myopia control. Further studies should be designed to understand the complex mechanisms underlying ortho-k in myopia control.