Individual factors influencing trabecular morphology in glaucoma patients undergoing filtration surgery

Epidemiologic studies have shown that various lifestyle characteristics are statistically associated with the chronic open-angle glaucomas. This study was designed to investigate the influence of individual factors on the light-microscopic morphology of the trabecular meshwork in open-angle glaucomas.

Quantitative computer-assisted topographic analysis of the trabecular meshwork was performed in meridional sections of 80 trabeculectomy specimens from patients with primary open-angle (n = 36), exfoliative (n = 30) and pigment-dispersion (n = 14) glaucoma. Measurements included inner wall length of the, central thickness of the trabecular meshwork, and compactness of the Schlemm canal and trabecular meshwork. Morphologic data were correlated with individual patient data including age, duration of the disease, maximum intraocular pressure, cup-disc ratio, refraction, height, weight, body mass index, a simple morbidity index, previous surgery, and number of topical antiglaucomatous medications used.

Inner wall length of the Schlemm canal was significantly lower in eyes with previous filtering surgery (P = 0.03), but not in eyes with a high number of topical medications (P = 0.17). There was a significant tendency for the inner wall length of the Schlemm canal to be shortened in patients where high maximum intraocular pressure was combined with long-term glaucoma (P = 0.027). Body mass index did not differ significantly between patients with primary open-angle, exfoliative, and pigment-dispersion glaucoma and showed no correlation with the quantitative data of the meshwork. The morbidity index correlated well with body mass index (0.0006) and age (P < 0.0001).

Contrary to findings of experimental mice studies, we found no indication that glaucoma patients with lower body mass index have a larger lumen of the Schlemm canal than patients with a higher body mass index. Although caution should be used when interpreting data from trabeculectomy studies, there is a certain probability that a history of previous filtering surgery and of a long-term high intraocular pressure will be associated with a shortening of the Schlemm canal.