Light reflected specularly by the inner limiting membrane (ILM) provides in
formation 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 th
e 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 regr
ession lines are log(10) rho = -4.234 - 0.0118 age and radius r = 1484 - 13
.6 age, respectively (age in years, r in micrometers). (C) 1999 Optical Soc
iety of America [S0740-3232(99)02905-1].