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Abstract #20753 Published in IGR 10-1
Accommodation-induced changes in iris curvature
Dorairaj S; Oliveira C; Fose AK; Liebmann JM; Tello C; Barocas VH; Ritch RExperimental Eye Research 2008; 86: 220-225
Eyes were imaged using anterior segment ultrasound biomicroscopy to compare alterations in iris contour following the onset of accommodation in eyes with narrow angles, pigment dispersion syndrome, and controls. A radial perpendicular image in the horizontal temporal meridian was obtained for one eye while the subject focused on a distant target ( approximately 6m, unaccommodated state) with the fellow eye. The subject then focused steadily on a near target ( approximately 0.33m, accommodated state) for 3min. Images were acquired at 0, 1, 2, and 3min. Iris curvature was determined by measuring the maximum distance between the posterior iris surface and a line from the iris root to the first point of contact between the iris and lens. In control subjects (n=22), iris curvature decreased immediately after the onset of accommodation, but not significantly (p=0.49), from 246±37μm (mean±SEM) to 205±82μm; curvature increased after 3min of accommodation to 298±57μm (p=0.10 vs. onset of accommodation). Eyes with pigment dispersion syndrome (n=15) exhibited curvatures of 60±79μm when unaccommodated, -3±83μm immediately after accommodation (p=0.12), and 146±94μm (p=0.01) 3min later. Eyes with narrow angles (n=16) exhibited curvatures of 449±45μm when unaccommodated, 414±46μm immediately after accommodation (p=0.37), and 523±40μm (p<0.01) 3min later. The results confirm the time-dependent nature of iris contour response, with significant differences observed between the initial observation after accommodation and the observation 3min later. The largest drop in curvature immediately after accommodation and the most rapid increase in curvature during subsequent observation were seen in the PDS subjects. We suspect that the more rapid increase in curvature in the PDS subjects is due to the elevated anterior chamber pressure caused by the "reverse pupillary block" effect.
Dr. S. Dorairaj, Department of Ophthalmology, The New York Eye and Ear Infirmary, New York, NY, USA
Classification:
6.12 Ultrasonography and ultrasound biomicroscopy (Part of: 6 Clinical examination methods)
9.3.5 Primary angle closure (Part of: 9 Clinical forms of glaucomas > 9.3 Primary angle closure glaucomas)
