Consideration of growth (age)‐related effects on globe size and corneal thickness in ovine eyes for use in laboratory studies

Abstract

PurposeThe aim was to assess differences in eyeball mass, corneal diameter and central corneal thickness in slaughterhouse‐procured ovine eyes.MethodsOver a 12‐year period, measurements of eye globe mass, horizontal corneal diameter and central corneal thickness were routinely undertaken within two hours post‐mortem. Only eyes free of obvious mechanical damage or disease were used.ResultsFrom measurements on 736 quality‐selected and trimmed eyes, globe wet mass ranged from 10.4 to 25.2-g, horizontal corneal diameter from 19.0 to 26.5-mm and central corneal thickness measured by ultrasonic pachymetry from 0.543 to 0.836-mm (with an overall average of 690 ± 0.056-mm). The ocular globe mass was strongly correlated to horizontal corneal diameter (r2 = 0.829). Central corneal thickness correlated with globe mass (r = 0.543) and to horizontal corneal diameter (r = 0.402). Based on the different anatomical measurements, a lamb's eye would be expected to have a thinner cornea (average 0.640-mm) than that of an adult outbred ewe (average 0.730-mm). In freshly procured eyes showing signs of slight corneal oedema, central corneal thickness was greater (average 0.856 ± 0.052-mm) and up to 24 hours of cold storage resulted in predictable increases in central corneal thickness of six to 24 per cent, especially in eyes showing signs of corneal oedema before storage.ConclusionsBased on the correlations obtained, differences in ovine eyes can be attributed to growth‐related differences in the animals and thus, indirectly to their expected ages. A simple measure of the horizontal corneal diameter in ovine eyes used for laboratory studies would be a useful indicator in reporting these studies.