Evaluation of healthy equine eyes by use of retinoscopy, keratometry, and ultrasonographic biometry.
OBJECTIVE
To assess natural variations in degree of refraction, corneal curvature, corneal astigmatism, corneal radius, and intraocular distance of healthy equine eyes.


METHODS
159 horses with healthy eyes that were admitted to a veterinary teaching hospital for nonophthalmic surgeries.


METHODS
Eyes of horses were examined with a retinoscope prior to anesthesia and with a keratograph and A- and B-scan ultrasonographic biometers during surgery. In addition, manual caliper measurements of horizontal and vertical corneal radii were obtained.


RESULTS
Mean +/- SD degree of refraction in the horizontal meridian of eyes was -0.06 +/- 0.68 diopters (D). Vitreous body length and horse age correlated negatively with refraction values. The horizontal corneal radius (15.96 +/- 1.28 mm) was larger than the vertical corneal radius (15.02 +/- 1.09 mm). Accordingly, the vertical corneal curvature (21.56 +/- 1.68 D) was greater than the horizontal corneal curvature (22.89 +/- 1.65 D). Axial globe length (40.52 +/- 2.67 mm), anterior chamber depth (6.35 +/- 0.59 mm), lens thickness (12.30 +/- 0.83 mm), and vitreous body length (21.87 +/- 1.85 mm) were positively correlated with body weight, height, and age. Results of keratograph and caliper measurements correlated well for horizontal corneal diameter but poorly for vertical corneal diameter. Results of A- and B-scan ultrasonography differed by < or = 1 mm in 64% of measured eyes.


CONCLUSIONS
Results of keratometry and ultrasonographic biometry varied widely. Additional research is needed to validate the keratograph used in our study for measurements in equine eyes.
Department of Small Animals and Horses, Faculty of Veterinary Medicine, Vienna University, Vienna 1210, Austria. p.grinninger@uu.nl
Petra
P
Grinninger
Monika
M
Skalicky
Barbara
B
Nell
D000367:Age Factors; D000818:Animals; D001699:Biometry / Q000379:methods; D005123:Eye / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005260:Female; D006736:Horses / Q000033:anatomy & histology / Q000502:physiology*; D008297:Male; D015999:Multivariate Analysis; D009799:Ocular Physiological Phenomena; D042262:Retinoscopy / Q000379:methods / Q000662:veterinary; D012737:Sex Factors; D014463:Ultrasonography