Reflectance and curvature of the inner limiting membrane at the foveola

Light reflected specularly by the inner limiting membrane (ILM) provides information on the topography of the retinal surface. The ILM in the central part of the foveal pit acts as a concave mirror. Light reflected specularly by this mirror forms an image of the entrance pupil in front of the retina. In 15 normal subjects (ages 16-56 years) we have measured photometric and geometrical-properties of this image to derive two characteristics of the ILM: its reflectance rho at the foveola and its radius of curvature r in the central part of the fovea. rho and r are found to decrease significantly with age (p = 0.0073 and p = 0.01, respectively). The equations of the regression lines are log10 rho = -4.234 - 0.0118 age and radius r = 1484 - 13.6 age, respectively (age in years, r in micrometers).