Structure of the inner retinal surface in simple diabetic retinopathy

An eye with moderate simple diabetic retinopathy in a 47-year-old man was enucleated for rubeotic glaucoma of 2 months' duration and was subjected to histopathological and ultrastructural studies. Particular attention was paid to the structure of the retinal surface as examined by scanning electron microscopy. Six normal eyes and 2 eyes with long-standing central retinal vein occlusion served as the control. The inner retinal surface in normal eyes with posterior vitreous detachment appeared as a smooth, continuous sheet seen by scanning electron microscopy. No cell-like structure was detected on the retinal surface. In the eye with simple diabetic retinopathy, on the other hand, numerous spherical cells with pseudopodic protrusions were observed throughout the retinal surface which were identified as macrophages in light, scanning and transmission electron microscopic studies. The macrophages were particularly dense and were arranged in circinate pattern corresponding to circinate lesions within the retina. The macrophages were also densely populated in retinal areas with hard exudates. In areas adjacent to the macrophages, the inner retinal surface lost its smooth and continuous structure. The matrix in the inner limiting membrane disappeared in such areas so that a coarse network of filaments lay bare on the retinal surface. These findings indicate that the inner retinal surface would be pathologically altered in simple diabetic retinopathy, particularly where hard exudates are located.