Stiffness of retinal and choroidal tissue: a surface wrinkling analysis of epiretinal membranes and choroidal folds.

Abstract

To measure the wrinkling periodicity (peak-to-peak or trough-to-trough distance) for epiretinal membranes and contraction-induced choroidal folds, and use this data to infer differences in the elastic properties of the retina and choroid, respectively. Retrospective case review. Forty eyes were identified with epiretinal membranes (33 eyes) or contraction-induced choroidal folds (seven eyes). Digital red-free photographs were used to determine the average peak-to-peak distance between adjacent folds of retina or choroid using commercially available software. The average peak-to-peak spacing was considerably larger for contraction-induced choroidal folds vs retinal folds caused by epiretinal membranes (278.2 +/- 62.2 vs 82.2 +/- 7.66 microm, respectively; P = .0001). There was no statistically significant correlation between the peak-to-peak distance and patient age for the epiretinal membrane group (P = .25) or the choroidal folds group, although the age range of patients within the later group was narrow. Epiretinal membranes and contraction-induced choroidal folds are two examples of wrinkling of biologic tissue under tangential stress. The larger peak-to-peak spacing for choroidal folds vs retinal folds demonstrates that the choroid is considerably stiffer than the retina under mechanical deformations.