Pigment dispersion syndrome patients do not have larger-than-normal irides

To compare iris cross-sectional area and thickness in the accommodated and unaccommodated states in controls versus patients with pigment dispersion syndrome (PDS) and to quantify short-term response of the iris to accommodation.

Thirty-three patients with PDS and 17 control subjects were examined with ultrasound biomicroscopy. A radial image of the iris and ciliary body was taken at the temporal quadrant before and after accommodation with the patient looking at a standardized target. Iris thickness was measured from a line perpendicular to the iris from points on the trabecular meshwork 500, 1000, and 3000 μm from the scleral spur. Ciliary body thickness was measured 500 μm posterior to the scleral spur. Independent sample t tests (2-sided) compared iris thickness and cross-sectional area between groups.

All participants were of European descent. Mean age was 45.6 ± 5.4 years (mean ± 95% confidence interval) in the PDS group and 34.9 ± 5.5 in the controls. Mean refractive error was -4.26 ± 1.0 diopters in the PDS group and -4.83 ± 1.0 diopters in the controls (P=0.499). There was no significant difference in iris cross-sectional area in the accommodated and unaccommodated states between the 3 groups. For all quantities measured (iris thickness at 500, 1000, 3000 μm; iris cross-sectional area; ciliary body thickness and area), there was no significant difference between the control group and the PDS group (P>0.35).

Iris cross-sectional area and thickness and ciliary body thickness were similar in the accommodated and unaccommodated states in PDS and controls. This result provides further suggestive evidence that nongeometrical factors contribute to the development of PDS.