An iris cysts looks like a brown sphere inside the eye. It can either be attached to the iris or free floating inside the eye. An iris cyst is transparent when light shines through it. It is important to differentiate iris cysts from iris tumours. Iris tumours also look like a brown mass inside the eye but light does not pass through them.
Animals can have either a single iris cyst or multiple cysts. Most of the time iris cysts cause no problems.
In horses iris cysts often involve the copra nigra. (top or bottom edge of the pupil) This can rarely cause head shaking and changes in behaviour.
Complications of iris cysts
Secondary glaucoma - an increase in the eye pressure - can occur if there are lots of cysts. The cysts can cause abnormalities to the flow of fluid inside the eye - some breeds are predisposed like Great Danes.
If the cysts burst then pigment from the cyst can deposit either on the front of the lens or on the inside of the cornea. Very occasionally this may reduce vision.
Treatment of iris cysts
Treatment of iris cysts is indicated when there are numerous cysts, or the cysts are large enough, so that they may affect vision.
Treatment options include:
1. Diode laser to "pop" the cyst: This is very effective as the cysts often collapses on itself.
2. Intraocular needle expulsion: A needle is introduced inside the eye and the iris cysts are "sucked out".
In horses the cysts can be treated with laser whilst the horses is standing and under sedation.
Post operative treatment
There is minimal post-operative care required after lasering an iris cyst. Most animals will need anti-inflammatory medication after surgery for about 1 week. After the first post-operative visit these are usually discontinued.