Purpose
To measure macular choroidal thickness (CT) using 1-micron SD-OCT system and to investigate the geographic CT differences among low, mildly and highly myopic subjects.
Methods
20 myopic subjects (n=40 eyes) without other identified pathologies participated in this study: 20 eyes of ≤3 diopters [D] (low myopic), 10 eyes between -3D and -6D (mildly myopic), and 10 eyes of ≥6 D (highly myopic). The mean age of subjects was 30.2 years (±7.6 years; range, 24 to 46 years). A 100-kHz SD-OCT system, capable of 6-mm ranging distance and 12-mm-wide field of view, was used to acquire 3D datasets from the subjects. The 3D OCT image of choroid was segmented into superior, inferior, nasal and temporal quadrants. The measured CT represented the normal distance between outer retinal pigment epithelium (RPE) layer and inner scleral border. Measurements were made within concentric regions centered at the fovea, extended to 5 mm away from the fovea at 1 mm intervals in the nasal and temporal directions. Statistical analysis was performed to evaluate CT at each region and observe the relationship between CT and the degree of myopia.
Results
For low myopic eyes, CT is the thickest under the fovea (273.85±49.01μm) as is in the case of healthy eyes. Peripheral to the fovea, the mean CT decreases rapidly along the nasal direction, reaching a minimum of 180.65±58.25μm at 5 mm away from the fovea; this value is 234.25±42.27μm in the temporal direction. In contrast, the thickest CTs lie in the temporal region for mildly and highly myopic eyes (where CT=194.94±27.28μm and 163±34.89μm, respectively), whilst the thinnest CTs appear in the nasal region (where CT= 100.84±16.75μm and 86.64±42.6μm, respectively). The CT reduction rate is calculated as 31.28μm/diopter from low to mild myopia, whilst it is 13.49μm/diopter from mild to high myopia.
Conclusions
The CT decreases gradually with the increased myopia. The current results support the theory that choroidal abnormality may play an important role in the pathogenesis of myopic degeneration.
Keywords: 452 choroid •
605 myopia •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)