Ultrasound Biomicroscopy and Iris Pigment Dispersion: a Case-Control Study

Background/aims: the study involved eyes affected by pigment dispersion syndrome (PDS) or pigmentary glaucoma (PG) investigated by ultrasound biomicroscopy (UBM). Different iridocorneal parameters were assessed and compared to those from healthy controls. The aim was to investigate the capacity of the UBM in differentiating the cases and, potentially, in confirming the pathogenic mechanisms. Methods: patients with a first diagnosis of PDS or PG were included. A cohort of healthy volunteers, matched for sex, age and refractive errors was recruited. All underwent UBM examination and the following parameters were assessed in relaxed and stimulated accommodative state in one eye: iris-lens contact (ILC); iridocorneal angle (ICA); iris concavity (IC). A receiver-operating characteristic (ROC) analysis assessed the ability of UBM to discriminate between subjects with and without PDS/PG. Results: twenty-four eyes formed the case group, four diagnosed as PG and the remaining 20 as PDS. Twenty-five eyes entered the control group. The two groups were statistically superimposable except for baseline intraocular pressure; higher in the case group (p = .0001). All UBM parameters showed statistic differences between the two groups. ICA in near vision was the best-performing parameter reaching a sensitivity (= specificity) of 0.875 with a cut-off at 53.0°. The second most sensitive parameter was IC, still in near vision. Conclusion: all UBM parameters considered were statistically different between the two groups. ROC analysis showed ICA and IC in near vision to be the most discriminant parameters. This evidence confirms the importance of iris movements in inducing the peculiar features of PDS/PG.