Page 1300 - Problem-Based Feline Medicine

63. The cat with abnormal iris

appearance

Michael E. Bernays

KEY SIGNS
● Abnormal iris shape.
● Abnormal iris coloration.

MECHANISM?
● Inflammatory processes, either idiopathic or associated with infectious agents, are the most
common cause of changed iris appearance. Neoplasia, immune-mediated inflammation and
degeneration are less frequent mechanisms for change.

WHERE?
● Iris.
● Other organ systems.

WHAT?
● Most diseases which alter iris appearance are inflammatory associated with infectious agents such
as FIP, FIV, FeLV and Toxoplasma, or are idiopathic. Iris neoplasia from melanoma or lymphosar-
coma are less common. Iris atrophy associated with age-related degeneration is common in old cats.

QUICK REFERENCE SUMMARY
Diseases causing abnormal iris appearance

DEGENERATIVE
● Iris atrophy* (p 1299)
Thinning of the iris with loss of normal iris color. Loss of normal pupillary constrictor function
resulting in sluggish pupil light reflex in an old cat.
ANOMALY

● Iris coloboma (p 1304)
Notch-like or sectorial defect in structure of the iris. Unusual.
● Persistent pupillary membranes (p 1304)
Small strand-like structures going from one part of the iris collarette to another, to the anterior lens
capsule or to the posterior corneal surface. Rare.

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