This cat is presented because the right eye has changed to a yellow-brown from the blue-green of the fellow eye. What could the cause of this be? How would you determine what the true cause is?
To my mind the differentials are development of uveitis, iris naevi (benign pigmented lesions) or frank melanoma. This picture shows little light brown areas in the iris characteristic of naevi, but there are also keratic precipitates on the back of the cornea like a grey haze, demonstrating uveitis. My only worry is that some of these are pigmented (particularly on the right) and that the intraocular pressure is 14mmHg in both eyes, rather than being lower in this one as we might expect from an inflamed eye. A paracentesis might yield cells that would give you a definitive diagnosis but removing aqueous in that manner would exacerbate any inflammation so at present I’ve chosen to watch and wait, wimp that I am!