Rare occurrence of an intumescent cataract in a diabetic domestic longhair cat.

Case summary: A domestic longhair cat in Australia was referred to an ophthalmology service with the complaint of lens opacity. An incipient cataract was diagnosed in the right eye and an intumescent cataract with an equatorial lens capsule rupture in the left eye. The patient was being treated for diabetes mellitus, and previous concerns for the eyes had included conjunctivitis and left-sided periocular swelling and epiphora. Systemic work-up performed over the 7 months before ophthalmic referral included complete blood counts, biochemistry, serology (feline immunodeficiency virus, feline leukaemia virus, toxoplasmosis, cryptococcosis), thoracic radiographs, and ocular ultrasound and electroretinography performed before phacoemulsification. The patient did not have evidence of active uveitis at the initial ophthalmological examination, and historical serology excluded some common infectious causes of uveitis. The cataracts were treated successfully by phacoemulsification in both eyes, restoring vision. However, an intraocular lens was implanted only in the right eye, as the pre-existing lens capsule tear in the left eye precluded intraocular lens placement. Based on the medical history and clinical presentation, diabetes mellitus was suspected to be the cause of the cataracts. Relevance and novel information: Intumescent cataracts are reported in humans and dogs but have rarely been reported in domestic cats. Nonetheless, the intumescent cataract in this patient had similar characteristics to those in diabetic canine cataracts.