Abstract

Laser Doppler interferometry (LDI) is a precise and noninvasive method to measure intraocular distances in vivo.¹ The appearance of several distinct components of the interference signal likely corresponding to reflections from the inner limiting membrane (ILM), retinal pigment epithelium (RPE) and the posterior surface of the sclera (Fig. 1) permits a thickness analysis of fundus layers. We defined the distance from the ILM to the RPE as retinal thickness and the distance from the cornea to the outer sclera as axial length. The distance from the RPE to the outer sclera includes the thicknesses of both the choroid and the sclera. Because the chick sclera is made of cartilage and connective tissue, it is unlikely to exhibit daily thickness fluctuations. We therefore assumed that daily fluctuations in the distance from the RPE to the outer sclera are due chiefly to choroidal thickness changes. The instrument measures optical distances. Geometrical distances are obtained by dividing the optical distances by the refractive index of the ocular media.

© 1996 Optical Society of America