Abstract
Purpose :
Research has shown the human choroid to rapidly thicken in response to full-field myopic retinal defocus, however the extent of the choroid’s regional selectivity and influence of refractive error hasn’t been thoroughly examined. This study explores the choroidal response to myopic defocus within the temporal and nasal retinal hemifields.
Methods :
The eyes of 21 young adults (10 myopic, MSE -2.27±1.10D, 11 emmetropic, MSE +0.07±0.29D, mean age 21.1±1.5 years) were exposed to 3 viewing conditions whilst viewing a 6m target binocularly: +3.00D temporal defocus, +3.00D nasal defocus, and a control condition (clear vision). Radial OCT scans of both eyes were captured at baseline, 25 and 45 minutes of defocus, and 20 minutes following cessation of defocus. Choroidal thickness was measured and analysed using a repeated measures ANOVA with 3 within-subject factors of defocus condition, time, and choroidal region (3mm nasally and 3mm temporally), and 1 between-subject factor of refractive error.
Results :
A statistically significant interaction between defocus condition, time, and choroidal region was observed (F5,523=6.687, p<0.001). Mean choroidal thickness across the 6mm macular area showed no significant change from baseline to each timepoint in the control condition (all p>0.05). Significant macular choroidal thickening from baseline was seen following 45 minutes of nasal defocus and 20 minutes of recovery (+6.13±7.81µm and +3.90±7.99 µm respectively, both p<0.05). This thickening differed between the 3mm nasal and 3mm temporal regions at 45 minutes, being significantly greater nasally than temporally (+8.04±9.76µm and +4.22±9.42µm, respectively, p=<0.002). Similarly, temporal defocus significantly increased the mean macular choroidal thickness at 45 minutes (+2.45±7.15µm, p<0.05), however significant thickening was contained within the temporal choroidal region (+4.28±8.50µm, p=<0.001). No significant impact of refractive error was found (F5,516=0.795, p=0.554).
Conclusions :
This study found evidence of fast-acting, regionally selective choroidal compensation to inducing and removing short-term myopic defocus within nasal and temporal choroidal regions, irrespective of the presence of low/moderate myopia. These findings provide further insight into the mechanisms underlying defocus-inducing optical interventions for myopia management.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.