Ocular parameters in the subgroups of angle closure glaucoma.

Abstract

This study was conducted to compare anatomical parameters, thought to be responsible for causing angle closure glaucoma (ACG), among eyes having acute, subacute or chronic ACG. Ninety consecutive patients diagnosed with a subgroup of ACG, and 30 age, sex and refraction matched controls, provided a total of 240 eyes for a prospective study. The refractive error, corneal diameter, keratometry, pachymetry, lens thickness and axial length were measured and the relative lens position was calculated. The data were analysed by paired t-test, ANOVA, signed rank test and multivariate analysis. Acute ACG eyes were mildly hyperopic. All the ACG subgroups had similarly short eyeballs and a steeper corneal curvature compared to control eyes. Acute ACG lenses were thicker than all the other groups (P < 0.001), but all ACG eyes had thicker lenses than the controls. Corneal diameters and anterior chamber depths were decreased in acute and chronic ACG eyes compared with subacute ACG and controls (P < 0.001). The uninvolved fellow eyes in each subgroup differed from affected eyes only in having more posteriorly positioned lenses. There was a spectrum of anatomical variations seen in the subgroups of ACG. Acute ACG eyes expressed an extreme shift of anatomical features away from normal, especially, smaller corneal diameters, leading to a large mobile lens in an already crowded anterior segment. This predisposed them to a severe relative pupillary block, and to a form of ciliary block glaucoma. Chronic ACG eyes were less divergent from normal and therefore could have suffered a milder form of the same kind of angle closure, but over a more prolonged period. Subacute ACG eyes deviated least from controls, and therefore exhibited mild signs and spontaneous resolution. Further work is required to elucidate completely the pathophysiology that leads to ACG.