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A. Desgroseilliers, P. J. Harasymowycz, A. A. Kamdeu Fansi, D. Tardif, M. R. Lesk; Plateau Iris: Gonioscopic and UBM Findings Associated With a Positive Dark Room Provocative Test After Iridotomy. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5101.
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To determine factors that predispose to a positive 45 minutes prone dark room provocative test (DRPT) in patients with plateau iris after laser iridotomy (LI).
In this retrospective observational cohort study, patients diagnosed with narrow angles persisting following LI (performed between March 2003 and June 2007) were submitted to a DRPT. Subjects were subsequently subdivided to form a positive (an increase of IOP of 6 mmHg or more) and a negative (maximum increase 3mmHg) DRPT group. Eyes of patients were imaged in 4 quadrants using an ultrasound biomicroscope. Quantitative assessment of UBM images was made by a blinded observer using research software. Measurements obtained included the anterior chamber depth (ACD), angle opening distance at 500 micrometers (AOD 500), angle recess area (ARA), anterior chamber angle (ACA), trabecular-ciliary process distance (TCPD), iris thickness (IT), iris-ciliary process distance (ICPD), height of plateau, distance of iris-cornea contact, and number of open quadrants. Demographic/clinical data were obtained from the patient charts. Comparisons of UBM measurements (mean and most open quadrant), clinical and demographic data were made using a t test or a khi-2 test accordingly. Correlation between UBM measurements and a positive DRPT was studied using Pearson correlation.
35 eyes of 35 patients were studied : 17 had a positive DRPT (group A) with a mean increase in IOP of 11.1 ± 3.5mmHg and 18 had a negative DRPT (group B) with a mean increase in IOP of 0.9 ± 0.1mmHg. Mean patient age was 57.9 ± 10.5yrs and 57.3 ± 10.8yrs in groups A and B (p=0.9). There was a significant difference in sex distribution (58% men in group A and 83% women in group B, p=0.01). Mean refraction was 3.41 ± 2.27D in group A and 2.60 ± 2.06D in group B (p=0.3). There was no statistically significant difference between the two groups in any UBM measurement. However, on indentation gonioscopy, patients in group A had significantly more synechial angle closure (35% vs. 0%, p=0.008) and more frequent double hump sign (59% vs. 11% p=0.005).
UBM measurements could not predict a rise in IOP after DRPT in patients with narrow angles following iridotomy. However, the presence of synechial angle closure and double hump sign on indentation gonioscopy was associated with a positive DRPT. While plateau iris is known to be more prevalent in women, men may be at higher risk of developing a positive DRPT.
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