Histologic findings in pigment dispersion syndrome and pigmentary glaucoma

To investigate the morphologic changes in the trabecular meshwork in a case series of eyes with pigment dispersion syndrome and pigmentary glaucoma, and surgical trabeculectomy specimens from eyes with pigmentary glaucoma.

Trabecular meshworks from 6 whole eyes from 3 donors and 7 trabeculectomy specimens were studied by light and electron microscopy. Axonal counts from the whole eyes were correlated with qualitative and quantitative data of meshwork changes.

Changes in the meshwork varied around the circumference of the eyes, but in all 6 eyes in most regions of the circumference there were numerous pigment granules within trabecular cells; pigment was not found within intertrabecular or cribriform spaces. In some regions of the circumference there was trabecular cell loss, loss of intertrabecular spaces, fusion of lamellae, and an increase in extracellular material under the inner wall of the canal. Separation of the normal tendinous connection to the canal wall cells was noted in some regions of all eyes. This change could be associated with regions of pathologic separation of the inner wall from the cribriform region, associated with partial obliteration of the lumen of the canal with cells and cell processes. In eyes with pronounced axon loss, meshworks showed most pronounced loss of trabecular cells and increased extracellular material. Trabeculectomy specimens had similar changes and, in addition, showed damaged trabecular cells and collapse of intertrabecular spaces without fusion of lamellae, consistent with artifacts from manipulation during surgery.

Loss of trabecular cells, fusion of trabecular lamellae with collapse of intertrabecular spaces, increase in extracellular material, and obliteration of the canal were found in various amounts around the circumference of eyes with pigment dispersion syndrome and elevated intraocular pressure, and pigmentary glaucoma. These probably all contribute to the development of increased intraocular pressure. Meshworks from trabeculectomy specimens showed these findings and also showed artifactual damage of cells and loss of intertrabecular spaces. This suggests that handling during surgery may cause single trabeculectomy specimens to give only an incomplete picture of the pathophysiology of pigmentary glaucoma.