Published by Rachel (Mathes) Davis, DVM, MS, DACVO July 2016
Publication: Veterinary Information Network (VIN)
Iridociliary cysts (i.e. uveal cysts, iris cysts) are relatively rare in cats.1 Cysts may occur spontaneously and are thought to arise from the posterior pigmented iris epithelium or the inner ciliary body epithelium, as with canine cysts.2 Feline cysts have been noted to be free-floating,3 adhered to the pupillary margin1 or within the posterior chamber.3 These are usually benign, but may cause dyscoria, anterior chamber shallowing or intraocular hypertension.3 They may be unilateral or bilateral, single or multiple, circular or oval, variably sized and variably pigmented. Iridociliary cysts are usually diagnosed in adult cats as incidental findings. It has been proposed that feline iridociliary cysts are more likely to be adhered to the pupillary margin than free-floating,1 although both types have been seeing in cats.
Iridociliary cysts have been suggested to occur spontaneously in cats, although one recent study showed a higher prevalence in Burmese cats, making genetic or inherited etiology possible.1 Other proposed etiologies include traumatic, congenital (with recognition of their presence later in life) or inflammatory.1-3
Ophthalmic Examination Findings: Iridociliary cysts are noted as unilateral or bilateral, single or multiple, circular or oval, variably sized or variably pigmented structures free-floating within the anterior chamber or attached to the pupillary margin. Pharmacologic mydriasis may reveal cysts attached to the posterior iris within the posterior chamber. Because pharmacologic mydriasis may cause intraocular hypertension in cats affected with iridociliary cysts, caution should be exercised in performing this diagnostic. If free-floating, cysts are gravity dependent and may be seen within the ventral anterior chamber. The presence of cysts may be confirmed with transillumination as cystic structures will transmit light (versus solid mass structures).
Disease Description in this Species
Iridociliary cysts are seen in adult cats (mean age 10yr).1 One study showed no sex-predilection,3 although another study reported a higher prevalence in female cats.1 Burmese cats are more commonly affected.1
Iridociliary cysts are noted as unilateral or bilateral, single or multiple, circular or oval, variably sized or variably pigmented structures free-floating within the anterior chamber or attached to the pupillary margin. In cats, cysts may cause dyscoria, anterior shallowing or intraocular hypertension. Cysts have also been noted to rupture, resulting in anterior dyscoria.1
- Middle-aged (10yr)
Iridociliary cysts are typically easily diagnosed based on appearance. Cysts are brown or black in cats. Tan or yellow cysts have been reported in dogs,4 but, to date, not in cats. Cystic structures are differentiated from solid masses by transillumination and movement, if free-floating. High-resolution ultrasound may be used as a diagnostic aid to differentiate cysts from uveal masses if they are unable to be transilluminated or if they are very thick-walled and do not transilluminate.5 If ventral anterior chamber cysts are present, rotating the patient to dorsal recumbency will cause the cysts to float down (i.e. “snow-globe” effect), thereby delineating them from masses.
Typically, uveal cysts are benign and incidental findings. They usually do not require treatment or monitoring over time. Iris cysts that are large and obstructing the pupil, causing visual disturbances, behavior changes or intraocular hypertension may be deflated using transcorneal diode laser therapy3 or manually using a 25-gauge or 27-gauge needle with magnification (i.e. operating microscope).2 Poorly pigmented cysts may not be amenable to diode laser therapy. Anterior chamber shallowing has been identified as a risk factor for development of intraocular hypertension (glaucoma), thus deflation should be considered for patients presenting with this.
If intraocular hypertension (intraocular pressure >25mmHg) is noted, topical anti-tensive therapy with dorzolamide or dorzolamide/timolol combination medication may be instituted BID to TID in the affected eye. Intraocular pressure should initially be evaluated 7-10 days after instituting therapy, then every 2-4 months thereafter.
Monitoring and Prognosis
Because most cysts are benign and incidental, the prognosis is typically excellent for most affected patients. If cysts are large, numerous or obstructing the pupillary margin, periodic monitoring for changes to vision or elevated intraocular pressure every 4-6 months may be warranted. If laser deflation is performed, the prognosis is good to excellent as all cats reported to have undergone this treatment have responded well with resolution of previous clinical signs.
- Iridal neoplasia
- Intraocular melanoma
- Blacklock BT, Grundon RA, Meehan M, Tetas Pont R, Hartley C. Uveal cysts in domestic cats: a retrospective evaluation of thirty-six cases. Vet Ophthalmol. 2016 Jul;19 Suppl 1:56-60.
- Hendrix DVH. Diseases and Surgery of the Canine Anterior Uvea. In Gelatt KN (ed): Veterinary Ophthalmology 4th ed. Pg 816 Blackwell Publishing, Ames IA
- Gemensky-Metzler AJ, Wilkie DA, Cook CS. The use of semiconductor diode laser for deflation and coagulation of anterior uveal cysts in dogs, cats and horses: a report of 20 cases. Vet Ophthalmol. 2004 Sep-Oct;7(5):360-8.
- Delgado E1, Pissarra H, Sales-Luís J, Peleteiro MC. Amelanotic uveal cyst in a Yorkshire terrier dog. Vet Ophthalmol. 2010 Sep;13(5):343-7.
- Bentley E1, Miller PE, Diehl KA. Use of high-resolution ultrasound as a diagnostic tool in veterinary ophthalmology. J Am Vet Med Assoc. 2003 Dec 1;223(11):1617-22, 1599.