Affects: Dogs
Iris cysts are hollow cavities in the eye filled with secretion. They come in various sizes, numbers, shapes, pigments, and can be free-floating, attached to the pupillary margin, or within the posterior chamber. Most frequently iris cysts do not cause any issues, but they can cause problems like: "fly biting" behavior, corneal endothelial pigment, lens capsular pigmentation, altered iris movement, decreased aqueous outflow with subsequent glaucoma, or block the vision when grown too big. They can be acquired or innate. Possible causes are inflammation, drug-induced, uveitis, a trauma, tumor-induced, parasitic, or implantation. Most frequently iris cysts are benign and need no treatment. Sometimes iris cysts are causing problems and need to be deflated. Iris cysts can be treated with trans corneal diode laser treatment, fine-needle aspiration or surgical excision. A conservative approach for the treatment of iris cysts is favored.
Clinical Presentation: Primary cysts come in various sizes and number but are usually fluid-filled, with regular borders and a smooth surface. The iris could be slightly displaced anteriorly because of a primary cyst, but normally no problems occur with primary cysts. Secondary cysts cause most of the times problems, and thus also need treatment. Secondary cysts usually have a rough surface, irregular borders, solitary and unilateral. Possible problems could be displacement of the iris, iritis and raised intraocular pressure.
A clinician should also be able to tell the difference between a cyst and a tumor. The main differences are that cysts usually cause displacement or the iris whereas a tumor arises and grows into the iris stroma. In the presence of an intrinsic or sentinel vessel than you probably have to deal with a tumor. The last main difference can be shown with transillumination, since transillumination always creates a shadow with a tumor but almost never with a cyst.
Diagnosis: Iris cyst must be differentiated from other kinds of possible "bodies" in the eye. After the body has been established as an iris cyst, it must be categorized as primary or secondary. It is necessary to differentiate secondary cysts even further. Clinical examination can achieve this differentiation with the use of multimodal imaging techniques like UBM, ultrasound B-scan (USB), anterior segment optical coherence tomography (as-OCT) and magnetic resonance imaging.