Iris Hyperpigmentation in Cats: Progression, Globe Retention and Long-Term Survival

To evaluate progression, globe retention, and long-term survival in cats with iris hyperpigmentation.

Medical records from 2010 to 2022 were reviewed retrospectively for signalment, clinical diagnosis, and morphologic diagnosis for cats with iris hyperpigmentation. Survey of included cats' owners provided progression, globe retention, and survival data.

Ninety-two cats were included in the medical record review. Twenty of 92 (22%) had been enucleated; all 20 were confirmed on histopathology as feline diffuse iris melanoma (FDIM). Owners and referring veterinarians of 36/92 (39%) cats provided follow-up data via a survey, with a median follow-up of 3.4 years. By the time of the follow-up survey, 22/36 (61%) cats had been enucleated, 10 prior to medical record review, and 11 since medical records were reviewed. There was no difference in survival rate between cats enucleated (16/22, 73%) and not enucleated (9/14, 64%), X2 = 0.29, p = 0.69. Considering cats who died (11/36, 31%), there was no difference in mean survival time between enucleated cats (6/11, survival 3.1 y) and not enucleated (5/11, survival 4.4 y), Kruskal-Wallis K = 0.53, p = 0.47. Owners of 8/14 (57%) cats that were not enucleated reported that iris pigmentation increased slowly over the years. Four of eight cats with progression had died, at a median age of 14.0 years, with a median survival of 2.0 years following initial presentation for iris hyperpigmentation. Hyperpigmentation was not noted in any previously normal contralateral eyes.

For cats with iris hyperpigmentation, based on retrospective survey data, long-term survival may not differ for those who are enucleated early and those who are not.