"Sticky" Third Eyelid

Q: Twice, my 12-year-old Paint gelding has gotten his third eyelid "stuck" over the top of his eyeball for 10 or 20 seconds. The first time was when water splashed in his eye during a bath. He tossed his head, rolled his eye upward, and the third eyelid stuck over the top of his eyeball, blocking his vision. Today the same thing happened when he rubbed his eye on his knee. He wasn't alarmed and continued eating his hay. I ran to retrieve saline solution. By the time I returned, his eyelid was normal.

This gelding is heterozygous for HYPP, although his HYPP is easy to manage with consistent exercise, a regular feeding schedule, daily turnout, and ample clean water. Over the years I have noticed that the beginning of an HYPP attack corresponds with the third eyelids being unusually high, covering the corners of his eyes. In contrast, these two "stuck" incidents affected only the right eye and seemed to be unrelated to any HYPP symptoms.

Why does his third eyelid get stuck over his eye? Would saline have helped the third eyelid return to normal?     Sheri, via e-mail

A: The third eyelid (nictitating membrane) flips up and rarely gets "stuck," so this behavior suggests a brief, purposeful, spastic episode or pain. In disorders where the eyelid acts "spastic" and stays up, both eyes are usually affected, as can happen with HYPP episodes, tetanus, metabolic imbalances such as hypocalcemic tetany, and neurologic toxicities.

Your horse having only the right eye affected suggests a possible irritation to that eyelid, which might be further evidenced by the second episode occurring when he attempted to rub it. Most horses with eye insults will squint or tear excessively when the eye is irritated. If this is not the case, something deeper at the base of the third eyelid might still be present.

It would be best to have your veterinarian sedate the horse and carefully examine the eyes and the eyelids for any possible foreign body (plant awns, etc.), summer sore granules, or even tumors. If nothing is found it might be useful to flush the naso-lacrimal duct through the nose opening and back up into the eyelid. Further diagnostics can become more complicated, so the basic exam is the most indicated.

About the Author

Doug Byars, DVM, Dipl. ACVIM

Doug Byars, DVM, Dipl. ACVIM, is Director of the medicine clinic at Hagyard-Davidson-McGee equine practice in Lexington, Ky.

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