Retinal distortion and cotton-wool spots associated with epiretinal membrane contraction

Several articles on surgery for macular pucker have noted the presence of intraretinal white spots, presumably cotton-wool spots, associated with epiretinal membranes. It was proposed that membrane contraction and resultant nerve fiber layer distortion might lead to blockage of axoplasmic flow and thus a cotton-wool spot. To see whether the observations supported this concept, the authors studied patients with epiretinal membranes associated with intraretinal white spots involving the center of the fovea, where there are normally no retinal vessels and the only axons are in Henle fiber layer.

Four patients with epiretinal membranes associated with prominent areas of intraretinal whitening involving the center of the fovea were examined before and after surgery. Observations and measurements were made from projected fundus photographs.

The intraretinal white spots, which appeared preoperatively to lie in the center of the fovea, proved to have been pulled in from more peripheral retina by the epiretinal membrane. These white areas were associated with surprisingly great distortion of the inner retina. Stretching of the inner retina seemed to play a larger role in the retinal distortion than full-thickness retinal folding.

The appearance and time course of these intraretinal white lesions were consistent with cotton-wool spots caused by mechanical disruption of axonal flow. The marked retinal stretching and distortion of the innermost layers of the retina were the most striking findings in this study and also seemed consistent with the concept that membrane contraction and resultant nerve fiber layer distortion might lead to blockage of axoplasmic flow and thus a cotton-wool spot.