Bilateral third eyelid ectopic cilia (hairs) in an adult horse

It was surprising that these hairs formed in a progressive manner on the third eyelids of a middle-aged horse. Hairs on the outside surface of the third eyelid are common and through wicking of the tears away from the tear ducts can cause a chronic tearing but not eye irritation. the location of these hairs caused contact with the cornea and sclera with resultant inflammation. The advantage of getting this diagnosed is it is very treatable.
DrO

Bilateral third eyelid ectopic cilia in an adult horse
Vet Ophthalmol. 2020 Sep;23(5):913-917.
Authors
Carolin L H Chiwitt 1 , Emma J Scurrell 2 , Heidi J Featherstone 3 , Christine L Heinrich 4
Affiliations

1 TKS Tierärztliche Klinik Stommeln, Pulheim, Germany.
2 CytoPath Ltd, Ledbury, UK.
3 The Ralph Veterinary Referral Centre, Marlow, UK.
4 Eye Veterinary Clinic, Leominster, UK.

PMID: 33462922
DOI: 10.1111/vop.12814

Abstract

A 15-year-old Cob mare presented with a 4-month history of chronic epiphora and intermittent blepharospasm in the right eye. On ophthalmic examination, two translucent aberrant hairs were identified at the third eyelid margin corresponding to an area of corneal fibrosis and neovascularization. Partial excision of the third eyelid was performed, and histopathology confirmed ectopic hair follicles. Two weeks later, clinical signs recurred in the same eye. Examination revealed another pair of aberrant hairs on the bulbar surface of the third eyelid near its leading edge. This portion of the third eyelid was also excised, and histopathology confirmed two additional ectopic hair follicles. Eight months later, the horse developed similar clinical signs in the left eye. Ophthalmic examination showed a single aberrant translucent hair at the third eyelid margin associated with focal fibrosis and neovascularization of the ventromedial cornea. Partial excision of the third eyelid was performed, and histopathology confirmed an ectopic hair follicle within the third eyelid conjunctiva. Excision was curative at 4 years postoperatively with no further recurrence in either eye.