Purpose:
Tangential traction in the macula from a thickened posterior hyaloid membrane has been implicated as a cause of diabetic macular edema. We try to point out the ultrastructural differences between taut posterior hyaloid membrane with macular edema in PDR patients and idiopathic epiretinal membrane(ERM) with posterior vitreous detachment(PVD).
Methods:
Tissues from 23 patients(5 with taut posterior hyaloid membrane in PDR eye, 5 with ERM with PVD in PDR eye, 13 with idiopathic ERM with PVD in normal eyes) obtained during vitrectomy were examined with transmission electron microscopy. PDR eyes in our study already had been completed panretinal photocoagulation before vitrectomy and there was no other tractional fibrous membrane in them. 13 idiopathic ERM eyes had no underlying ophthalmic disease. Retinal tear and detachment were not detected.
Results:
The epiretinal tissues of posterior hyaloid membrane predominantly associated with fibillary cytoplasmic processes of glial cell covering the surface of collagen layer. In idiopathic epiretinal membrane, fibroblasts were found predominantly and glail cells(fibroastrocyte like cells), vascular endothelial cells, macrophages in frequency. In this ERM group, there was no difference of cellular component between PDR and normal eyes. We found variety of blood vessels in both groups.
Conclusions:
This study illustrates some of the ultrastructural characteristics of the taut posterior hyaloids membrane in PDR and idiopathic ERM with PVD. Both contained collagen and a large cellular component. However, taut posterior hyaloid was marked by the cytoplasmic infiltration of glial cell in surface. It may contribute to abnormal vitreomacular adherence and could play a role in the pathogenesis of macular edema in PDR patients. .
Keywords: microscopy: electron microscopy • retina • macula/fovea