The relationship between retinal and choroidal thickness and visual acuity in highly myopic eyes

Background/aims To correlate visual acuity in highly myopic eyes without macular disease with retinal and choroidal thickness as measured by spectral-domain optical coherence tomography (OCT). Methods 60 eyes of 46 highly myopic patients (spherical equivalent -6 D or axial length 26mm) were studied in a clinical setting. Eyes with any clinical evidence of maculopathy or amblyopia were excluded. Eyes were imaged using the 3D-2000 OCT (Topcon Corporation, Tokyo, Japan). Two independent investigators manually measured: choroidal thickness at 500-m intervals up to 2500-m nasal and temporal to the fovea, subfoveal choroidal thickness, foveal thickness, outer nuclear layer and photoreceptors in addition to retinal pigment epithelium (RPE). Statistical analysis was performed. Results Mean age was 45.9 +/- 17.9years (range 18-99), mean best-corrected visual acuity (BCVA) LogMAR was 0.11 +/- 0.19 (range 0-1), mean axial length was 28.2 +/- 2.4mm (range 26-35.3) and mean spherical equivalent was -12.05 +/- 5.02 D (range -6 to -26). Mean macular choroidal thickness was 157 +/- 84.6m (range 16.7-426.5), mean subfoveal choroidal thickness was 166 +/- 88.7m (range 13.5-486.5), mean foveal thickness was 221.1 +/- 30.3m (range 157.5-296), mean outer nuclear layer was 121.3 +/- 22.6m (range 74-191.5) and mean photoreceptors in addition to RPE was 99.5 +/- 10.8m (range 71.5-115.5). BCVA (LogMAR) negatively correlated with macular choroidal thickness (r=-0.371, p=0.003), subfoveal choroidal thickness (r=-0.358, p=0.004) and photoreceptors and RPE aggregate (r=-0.346, p=0.006). Conclusions Subfoveal choroidal thickness, mean macular choroidal thickness and outer retinal thickness are the most important predictive factors of visual acuity in highly myopic eyes without macular pathology. Outer nuclear layer and foveal thickness are not related to visual acuity.