Any opacity of the lens or its capsule is known as a cataract, and they have many different causes. Cataracts are much more common in dogs than cats, it is important to recognise them In oredrand understand what to do next. A good ophthalmic examination will help you differentiate cataracts from nuclear sclerosis. It will also allow you to assess for any other pathology in the eye and decide if it is related to the cataract. Cataracts can be removed surgically, by phacoemulsification, but not all cataracts or indeed eyes are suitable for this to be performed. Many cases will require medical treatment to control the uveitis associated with cataract development, but it is important to note that there is no medical treatment that removes the cataracts themselves. Careful and thorough patient assessment is required, with tonometry, gonioscopy, ultrasound and electroretinography all essential in the work-up prior to considering surgery. Many cataracts are small and non-progressive, never requiring medical or surgical intervention. Others may progress and lead to vision loss, with some maturing very quickly, resulting in uveitis (Phacolytic) or even lens rupture due to intumescence (Phacoclastic). Knowing how to distinguish between these types of opacities is key to being able to give a prognosis for the affected eyes and patients.