Eyelids & the Anterior Segment:
                        Case nineteen

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This is the left eye of a 19 year-old woman who was seen in casualty for a right corneal abrasion. Her left visual acuity was 6/6.

a. What is the diagnosis?

Persistent pupillary membrane.

b. What is the cause for this abnormality?

It results from incomplete involution of the anterior tunica vasculosa lentis and is the most common developmental abnormality of the iris . The membranes always arise from the collarette (compared with acquired causes in which the membrane can arise from any part of the iris) and may be attached to the anterior surface of the lens; span over the pupil to attach to the opposite side or be free floating.

c. Does it have any visual consequences?

Pupillary membrane seldom causes visual disturbance. When attached to the anterior surface of the lens it may cause cataract formation which is always visually insignificant. In rare cases, where the membrane is so extensive that the vision is affected then iridectomy may be needed.