Corneal opacities: In order to function properly the cornea should be transparent, any opacity will impair function. If you can correctly identify the different types of corneal opacities and their cause, then you will know whether or not appropriate treatment (medical and/or surgical) will improve or restore corneal clarity. Do a thorough examination of the cornea, look from different angles, use a bright light and magnification. Think about the colour of the opacity, is it blue/grey, red, white or black/brown? There may be more than one colour present in an affected cornea, as there are only a limited number of ways that it can respond to insult. Blue/grey opacity is due to oedema, which may be the result of epithelial or endothelial cell loss. Red can be due to vascularisation, which may be superficial or deep, or more rarely due to intrastromal haemorrhage. White opacites are the most frequently seen and may be due to fibrosis, cellular infiltrate, lipid or calcium deposition. Black deposits are most likely to be pigmentation, usually superficial and sub-epithelial, but also occasionally endothelial. In cats, brown pigmentation associated with a sequestrum is also a possibility. There is one more opacity that doesn’t follow the above rules and that is a corneal foreign body, which can come in all shapes, sizes and colours!

Anterior chamber, lens and vitreous: A number of different lesions, resulting from different disease processes, can cause an opacity of the ocular media, affecting the visual axis. This short presentation covers opacities affecting the anterior chamber, lens and vitreous. The focus is on recognising and identifying the opacity by looking at numerous examples. Lesions discussed include uveal cysts, hypopyon, hyphaema, cataract and asteroid hyalosis.