Bilateral segmental accessory iris membrane with narrow anterior chamber angle.

Accessory iris membrane (AIM) is a rare anomaly characterized by hyperplasia of the superficial mesodermal layer of the iris.[1234] Unlike previously described cases with circumferential involvements, this is the first reported case of segmental AIM, with both eyes demonstrating duplicated iris tissue confined to the inferonasal part of the pupil and a shallow anterior chamber. A whitish band is present along the free margin of the membrane [Fig. 1a and b], which appears non-contractile on pupil dilation with mydriatic [Fig. 1c and d]. Ultrasound biomicroscopy and anterior segment optical coherence tomography both confirmed the location of the membranous structure anterior to the iris plane.

Figure 1

Anterior segment photography by slit lamp of bilateral accessory iris membrane (a and c right eye, b and d left eye)

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