Abstract
Purpose:
Myopic eyes exhibit retinal thinning which is thought to be associated with expansion of the globe during myopia development. The aim was to compare retinal contour and retinal thickness in four retinal meridians to examine how it changes as a function of refractive error, with the hypothesis that regions that exhibit the greatest expansion of the globe should be associated with greater retinal stretching, and thus retinal thinning.
Methods:
Forty-six subjects, aged 22-39 years, were included in the study, with refractive errors ranging from +0.75 D to -9.50 D and less than 1.50 D astigmatism. Subjects were divided into four refractive groups: emmetropes (+0.75 D to -0.75 D; n=13) ; low myopes (-1.00 D to -3.00 D; n=10); moderate myopes (-3.00 D to -6.00 D; n=14), and high myopes (more than -6.00 D; n=9). Perifoveal retinal thickness was measured using an Optovue RTVue spectral-domain OCT. Axial length was measured centrally and peripherally out to 30 degrees eccentricity in the vertical and horizontal meridians with a Zeiss IOL Master biometry system, and retinal contour coordinates were derived from these measurements using a schematic eye model derived for each subject.
Results:
Retinal depth at 30 deg eccentricity increased significantly with increasing myopia in all four retinal quadrants, (p<0.001). Asymmetries in retinal contour were also found, with low myopes exhibiting relatively steeper inferior retina compared to superior retina at 20 deg (p=0.005) and 30 deg (p=0.015) eccentricities, and high myopes exhibiting relatively steeper temporal retina than nasal retina at 20 deg (p=0.004) and 30 deg (p<0.001) eccentricities. Steeper retinal contours, or greater retinal depths, at 30 deg eccentricity were associated with retinal thinning in the superior (p=0.017) and inferior (p=0.012) quadrants. In the nasal region at 10 deg eccentricity, however, shallower retinal contour was associated with retinal thinning in the perifovea (p=0.049).
Conclusions:
Regional variations exist in myopic eye growth, resulting in local differences in retinal thickness and retinal contour. At 30 deg eccentricity, greater retinal depth, or steeper contour, is associated with thinner retina in myopia. However the opposing trend was found in the nasal retina at 10 deg eccentricity; thus a shallower retinal contour near the optic nerve head may indicate greater posterior expansion of the globe.
Keywords: 605 myopia •
688 retina •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)