INTRAOCULAR-PRESSURE VARIATION ASSOCIATED WITH BODY LENGTH IN YOUNG AMERICAN ALLIGATORS (ALLIGATOR-MISSISSIPPIENSIS)

Using an applanation tonometer, 5 replicate intraocular pressure (IOP) measurements were obtained from each eye of 12 young clinically norma l, American alligators. Alligator length ranged from 46 to 117 cm, mea sured from snout to tail tip. All IOP were recorded by a single observ er at an ambient temperature of approximately 25 C, and ranged from 5 to 35 mm of Hg. Observer reliability was excellent (intraclass r = 0.9 3), and IOP did not change over the ordered sequence of 5 replicate me asurements/eye. Replicate Iop measurements were, therefore, averaged i n each eye for comparison between eyes of the same alligator. Left and right eye IOP were highly correlated within individual alligators (r = 0.92), whereas the mean within-animal difference between left and ri ght eye IOP was not statistically significant (95% confidence interval [CI] for the left eye-right eye mean difference, -1.9 to 1.5 mm of Hg ). Mean iop determined for 5 confirmed females and 3 confirmed males d id not differ significantly between the sexes (95% CI for the male-fem ale difference in means, -2.1 to 3.7 mm of Hg). Mean +/- SEM IOP of 23 .7 + 2.1 mm of Hg determined for 4 alligators < 50 cm long was signifi cantly (P = 0.009) greater than mean IOP of 11.6 + 0.5 mm of Hg determ ined for 8 alligators > 50 cm long (95% CI for the difference in means , 8.5 to 15.7 mm of Hg). In young alligators, the relation between bod y length and IOP appears to be nonlinear, possibly with a negative exp onent.