Horse Veterinary Questions? Ask an Equine Vet.
I'm sorry to hear that your foal has an eye issue. Usually, with a corneal ulcer we can use a fluorescein eye stain to see if there is a defect on the cornea itself (outside of the eye). The stain is only picked up by the rough underlying corneal tissue, and not the normal outer corneal layer. It is a fluorescent green color. If there is a corneal ulcer, I generally avoid using any ophthalmic (eye) ointment that has a steroid in it like dexamethasone as this slows the healing process. Instead I use a Neomycin-polymixin-bacitracin eye ointment to treat/prevent any bacterial infection on the cornea.
The visual difference between a corneal ulcer and a cataract is that an ulcer is on the outer layer of the cornea (out side of the eye) and a cataract is inside the eye in the lens (which is behind the iris and pupil of the eye). Cataracts can appear rather suddenly if they are associated with trauma and subsequent inflammation in the eye itself. If this is associated with trauma, then the medication you are using with dexamethasone may be needed as it will reduce inflammation in the eye. There are also congenital cataracts but these don't usually show up acutely (suddenly).
You can always have a fluorescein stain test done to rule out if it is a corneal ulcer. Ulcers are visible on the outside of the eye. I would imagine that if your veterinarian used an ophthalmoscope then he would have determined if the white cloudy spot is in the eye or on the cornea.
I hope this has fully answered your question. If you have any other questions or concerns, please don't hesitate to ask.
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