A translation for Corpora Nigra is ‘black body’.
These are small dark enlargements most commonly found on the dorsal pupillary border (top bit of the pupil).
Their job is considered to be shading the retina from sunlight when the pupil is small on bright sunny days. We simply wear sunglasses ☺️
Occasionally these can become enlarged due to fluid production inside. We then call them iris cysts. Mostly these are of no concern. The Corora Nigra can occasionally be large in size or number and affect vision. They are an uncommon cause of ‘spookiness’ or behavioural changes.
An important growth to rule out however, is ocular (eye) melanoma. These tend to occur on an area of the iris which is not the pupil border. These are dangerous as they can be invasive and cause detrimental damage to the eye resulting in vision loss and pain.
If you are concerned, an ocular examination by the vet should help with the initial diagnosis, but ultrasound can also be used to help determine which structure is present. Ultrasound of the eye is a relatively simple process and can provide vital information to assist a diagnosis.
Next time you go to see your horse, have a look at these amazing structures. If you get to know what is normal for your horse, you will quickly be alerted when something changes.