Very shallow anterior chamber and high IOP in an older cat
12-year-old female domestic shorthair cat with mild bilateral mydriasis noticed by the owner. Vision preserved. On slit-lamp examination both anterior chambers are very shallow: the iris and lens are displaced forwards uniformly. No aqueous flare, keratic precipitates or synechiae. Blood pressure normal.
| Parameter | Result | Reference |
|---|---|---|
| Right eye IOP (rebound tonometry) | 32 mmHg | 10–25 |
| Left eye IOP | 28 mmHg | 10–25 |
What is the diagnosis and the most appropriate medical treatment?
chevron_right Show answer and explanation
A. Glaucoma secondary to anterior uveitis; intensive topical corticosteroid
It is the commonest cause of feline glaucoma, but there are no signs of uveitis here (flare, precipitates, synechiae). A uniformly shallow chamber with an anteriorly displaced lens points to another mechanism.
B. Anterior lens luxation; urgent intracapsular lensectomy
In anterior luxation the lens lies within the anterior chamber, in front of the iris, and it is usually unilateral. Here the iris and lens move forwards together in both eyes, without luxation.
C. Aqueous humour misdirection syndrome; topical dorzolamide as first line
Correct. Typical of older cats: aqueous is misdirected into the vitreous, which pushes the iris–lens diaphragm forwards and shallows the chamber. IOP usually rises only mildly and slowly. Topical carbonic anhydrase inhibitors are the treatment of choice; lensectomy is reserved for refractory cases.
D. Primary angle-closure glaucoma; topical latanoprost as first line
Prostaglandin analogues, very effective in dogs, barely lower IOP in cats. Primary glaucoma is also rare in this species and does not explain the uniformly shallow chamber.
lightbulb Key takeaway
In cats, glaucoma is almost always secondary (uveitis, intraocular neoplasia) or due to aqueous misdirection in older animals; do not extrapolate latanoprost from dogs. Measure IOP in every older cat with mydriasis or a shallow anterior chamber, even if it can see.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.