Clinical applications of short-term choroidal thickness modulation in myopia management

Abstract

A growing body of evidence shows the choroid to be a key component in the visual regulation of eye growth. Responsive to various optical and pharmaceutical stimuli, the choroid is a highly dynamic structure capable of rapid thickening and thinning. However, the significance of the fast-acting bidirectional choroidal response with respect to long-term ocular growth remains obscure. To explore the prospect of using choroidal thickness as a predictor for myopia progression, this thesis investigated transient changes in human choroidal thickness following modifications to the visual environment relevant to global myopia management strategies. Over recent years, the uncertain role of choroidal imaging in myopia management has led to its inconsistent use in clinical practice worldwide. Further, promising prescribing trends showed myopia control spectacles to be the most frequently prescribed intervention. With such lenses often employing defocusing peripheral optics, regional alterations in the choroidal spatial distribution were quantified using appropriate instrumentation following short-term exposure to patterns of spectacle lens-induced myopic defocus. The results indicated localised expansion and recovery following 45 minutes of hemifield blur in myopic and emmetropic eyes. Significant differences between the nasal and temporal choroidal alterations suggest non-uniform sensitivities to defocus across the choroid. Additionally, the impact of immediate and longstanding myopia control spectacle wear was explored, evidencing separate yet associated mechanisms mediating short- and long-term choroidal thickness changes provoked by peripheral retinal myopic blur. This thesis provides important insights into existing worldwide uses of choroidal thickness modulation in myopia management, clinical considerations when using choroidal imaging to quantify small changes, and characteristics of local choroidal responses to retinal defocus. This thesis demonstrates that immediate choroidal thickness changes may be predictive of long-term regional changes, uncovering research directions to further understand the choroid’s role in ocular growth and to identify specific choroidal regions that matter the most for myopia control.