Morphological Abnormalities of Schlemm's Canal in Primary Open-Angle Glaucoma From the Aspect of Aging

Purpose: To evaluate morphological abnormalities of Schlemm's canal (SC) among primary open-angle glaucoma (POAG) patients with a family history of POAG (group A), those without a family history of POAG (group B), and patients with normal-tension glaucoma (group C) from the aspect of aging.

Methods: A total of 160 trabeculectomy specimens from 133 POAG patients were processed for light microscopy using immunohistochemical staining of thrombomodulin and transmission electron microscopy. The following parameters were statistically evaluated: SC length, the percentage of the thrombomodulin-negative area (PTNA) of SC, and the inner-wall SC endothelial cell density (SC-ECD/100 μm).

Results: No significant differences in age were observed among the three groups (group A: 56.71 ± 14.83; group B: 58.13 ± 18.13; group C: 56.61 ± 9.78). Length of SC in the group A patients (198.70 ± 81.65 μm, n = 70 eyes) was significantly shorter than in group B (250.30 ± 70.83 μm, n = 67 eyes), and group C (277.70 ± 65.52 μm, n = 23 eyes) patients. A positive correlation of patient age and SC length was observed in group B (r = 0.45, P = 0.0013), but SC length in group A tended to decrease with aging (r = -0.22, P = 0.07). No significant difference in SC was found between group A and B patients before age 50 years (P = 0.30). Correlations between patient age and increase of PTNA (r = 0.38, P = 0.0013) and patient age and decrease of SC-ECD (r = -0.53, P = 3.95 × 10(-6)) were observed only in the group B cases.

Conclusions: Our findings suggest that SC in group A may easily collapse during middle age, while SC in group B remains open and SC endothelial cells drop out at around middle age.