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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #268853
Title: Ocular findings in quarter horses with hereditary equine regional dermal asthenia

Author
item MOCHAL, C - Mississippi State University
item MILLER, W - Mississippi State University
item COLLEY, A - Mississippi State University
item LINFORD, R - Mississippi State University
item RYAN, P - Mississippi State University
item RASHMIR-RAVEN, A - Mississippi State University

Submitted to: Journal of the American Veterinary Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2010
Publication Date: 8/1/2010
Citation: Mochal, C.A., Miller, W.W., Colley, A.J., Linford, R.L., Ryan, P.L., Rashmir-Raven, A. 2010. Ocular findings in quarter horses with hereditary equine regional dermal asthenia. Journal of the American Veterinary Medical Association. 237(3):304-310.

Interpretive Summary: The objectives of this study were to compare ocular (eye) structures of Quarter Horses with a disease known as hereditary equine regional dermal asthenia (HERDA) with those of Quarter Horses not affected by HERDA (control horses) and to determine the frequency of new eye ulcers for horses with and without HERDA during a 4-year period. The results of this study found that eye corneal thickness of horses with HERDA was significantly less than that of control horses, but tear production of horses with HERDA was significantly greater than that of control horses. The incidence of eye corneal ulcers was significantly greater for horses with HERDA than for horses without HERDA during the 4-year period. The clinical relevance of these findings suggest that alterations in eye corneal thickness, arrangement of structures in the eye, and incidence of eye corneal ulcers are indicative of abnormalities in horses with HERDA which were not limited to the skin.

Technical Abstract: The objective of this study was to compare ocular structures of Quarter Horses homozygous for hereditary equine regional dermal asthenia (HERDA) with those of Quarter Horses not affected by HERDA (control horses) and to determine the frequency of new corneal ulcers for horses with and without HERDA during a 4-year period. Cohort study of ocular structures and retrospective case series of horses with and without HERDA. The cohort portion of the study involved 10 Quarter Horses with HERDA and 10 Quarter Horses without HERDA; the retrospective case series involved 28 horses with HERDA and 291 horses without HERDA. Ophthalmic examinations, Schirmer tear tests, tonometry, corneal pachymetry, histologic examinations, and scanning electron microscopy (SEM) were performed in cohorts of Quarter Horses with and without HERDA. Records were reviewed to determine the incidence of corneal ulcers in horses with and without HERDA during a 4-year period. Corneal thickness of horses with HERDA was significantly less than that of control horses, but tear production of horses with HERDA was significantly greater than that of control horses. Results of SEM revealed zones of disorganized, haphazardly arranged collagen fibrils in corneas of horses with HERDA that were not evident in corneas of control horses. The incidence of corneal ulcers was significantly greater for horses with HERDA than for horses without HERDA during the 4-year period. Alterations in corneal thickness, arrangement ofcollagen fibers, and incidence of corneal ulcers indicated that abnormalities in horses with HERDA were not limited to the skin