A shadow on the nasal iris during a flashlight test suggests what about the anterior chamber depth?

A shadow on the nasal iris during a flashlight test indicates an abnormally shallow anterior chamber. This phenomenon occurs because when the light is shone at the eye, it casts a shadow on the iris if the anterior chamber is not sufficiently deep. In a normal or deeper anterior chamber, the light would typically illuminate the entire area of the iris without creating a shadow.

The presence of a shadow suggests that the angle of the anterior chamber may be narrow, which could lead to conditions such as angle-closure glaucoma. Therefore, a shadow observed in this test is an important clinical sign that highlights potential issues with anterior chamber depth, warranting further examination and evaluation of the patient's ocular health.