Major abnormalities are easily seen with the naked eye, especially if the iris is light colored. A penlight is used to compare the injured iris' color with that of the fellow eye.3
1 Examination of the iris always includes examination of its aperture, the pupil.
2 Dividing the globe into anterior and chambers is especially important in an aphakic or pseudophakic eye filled with silicone oil.
3 Heterochromia is obviously impossible to diagnose without inspecting the fellow eye. Color difference is much more difficult to notice at the slit lamp since the two eyes cannot be viewed simultaneously.
The slit lamp remains the most important diagnostic tool. The iris must be inspected for the presence of wounds, membranes, and IOFBs, as well as for its shape (i.e., iridodialysis). Examination of the pupil is crucial (see Chap. 1.9 and Table 2.6.1), and includes evaluation both static (e.g., shape) and dynamic components (e.g., reaction to light). Inflammation, which always accompanies trauma, makes the pupil small4 and may make it appear "muddy" due to swollen vessels and protein debris.
If an abnormality such as an irregular pupil size or iris discoloration is found, the ophthalmologist must ask the patient about preexisting conditions (previous injury, drug use) and diseases (uveitis). If necessary, an old photograph should be used for comparison to determine whether a heterochromia is congenital or a sign of siderosis. A greenish iris discoloration is often observed in (pre)phthisical eyes.
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