Uveal diseases

From Cat
Anatomy of the uveal tract
Persian cat with heterochromia iridum
White DSH with subalbinotic eye. Note that the iris lacks pigment and is almost translucent. The pink fundus reflex indicates a similar lack of pigment and also absence of tapetum in the fundus

Uveal diseases and uveal changes are relatively common eye diseases in cats and are readily diagnosed by both pet owners and pet practitioners due to the prominent position and obvious appearance of the iris.

The uveal tract consists of the iris, ciliary body and choroid. The characteristic pgiment of the iris is due to the presence of melanocytes which produce melanin pigment, explaining why iris melanoma are relatively common in cats[1].


The iris of young kittens is grey to slate-blue in color. In most adult cats the iris is yellow to gold but other variations includes shades of green and blue. Rarely, in complete albinism, the iris is pink. Occasionally, especially in oriental and white cats, each iris is of different color with one eye blue and the other yellow to green.

Ciliary body

The ciliary body functions as a pump, responsible for the production and removal of aqueous humour, replenishment of vitreous glycosaminoglycans, provision of anchoring points for the lens zonular fibres and rather limited dynamic accommodation of the lens. The rate of aqueous production is 15 μl/min and is normally equaled by aqueous outflow, thus maintaining a relatively constant intraocular pressure.

Congenital abnormalities

Acquired abnormalities of the iris


  1. Barnett, KC & Crispin, SM (2002) Feline ophthalmology: An atlas and text. Saunders, USA