Treatment and long-term follow-up of distichiasis, with special reference to the Friesian horse: a case series

Reasons for performing study: Distichiasis is very uncommon in horses and treatment options and outcome remain unknown. Objectives: To describe treatment and long-term follow-up of distichiasis in the horse. Study design: Retrospective clinical study. Methods: Case records of horses admitted for diagnosis and treatment of uni- or bilateral distichiasis between 2003 and 2012 were reviewed. Long-term (>6 months after last treatment) follow-up was by telephone conversation with the owner or referring veterinarian. Data were analysed using a Chi-squared test. Results: Eighteen cases were identified, of which 17 were Friesians. All horses had signs of corneal irritation or ulceration concurrent with distichiasis. In total, 29 eyes were affected with distichiasis of which 23 had clinical signs. All corneas were stained with fluorescein and 13 had fluorescein positive defects (45%). The lower eyelidwas affected more often. Two different electrocautery deviceswere used for treatment. The complicationswere slight scarring of the eyelids (100%) and clinical recurrence (54%). Successful resolution of the clinical signs after one treatment occurred in 46% of the horses and in 77% of the horses satisfactory long-term results were found after a mean of 2 treatments (range: 1– 6 treatments). There was significant correlation between number of hairs and recurrence (P<0.002). Conclusions: There is a breed predisposition of distichiasis in the Friesian horse. In Friesian horses that present with uni- or bilateral corneal irritation or corneal ulceration, careful examination of the eyelid margins should be performed to diagnose distichiasis. Electrocautery is a valid and successful therapeutic modality which is minimally invasive, inexpensive, has a low complication rate and is easy to perform in the standing sedated horse. The recurrence rate is low in horses with less than 5 distichiae.