Familial Internal Retinal Membrane Dystrophy

Folds in the internal limiting membrane are commonly seen, especially in the macula.  Intraretinal edema is seen throughout but may be most evident in the macula which often appears cystic.  Superficial microcystic changes in the retina are concentrated in the posterior pole.  The internal limiting membrane often appears thickened and filamentous material may be present in areas where it is separated from the retina.  The inner retina may have schisis cavities.  Visual acuity remains good until midlife.

This disorder is considered by some to result from a primary defect in Muller cells resulting in permeability defects on the retinal surface.  Evidence for this hypothesis comes from ERG studies in which light adapted responses showed a delayed and reduced b-wave, with broad and delayed ON and OFF responses and a missing flicker response.  However, responses may be inconsistent between the two eyes and more studies are needed.

Histologic studies show endothelial cell swelling, pericyte degeneration, and basement membrane thickening in retinal capillaries.