Iris. At the same time, inspect each iris. The markings should be clearly defined. With your light shining directly from the temporal side, look for a crescentic shadow on the medial side of the iris. Since the iris is normally fairly flat and forms a relatively open angle with the cornea, this lighting casts no shadow.
Occasionally the iris bows abnormally far forward, forming a very narrow angle with the cornea. The light then casts a crescentic shadow.
In open-angle glaucoma—the common form of glaucoma—the normal spatial relation between iris and cornea is preserved and the iris is fully lit.
This narrow angle increases the risk of acute narrow-angle glaucoma— a sudden increase in intraocular pressure when drainage of the aqueous humor is blocked.
Pupils. Inspect the size, shape, and symmetry of the pupils. If the pupils are large (>5 mm), small (<3 mm), or unequal, measure them. A card with black circles of varying sizes facilitates measurement.
Miosis refers to constriction of the pupils, mydriasis to dilation.
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