Intraocular Pressure Decreases Near Completion of Ocular Biometric and Pubertal Growth in Dutch-Belted Rabbits

Abstract

Purpose: To evaluate the relationship of ocular growth and intraocular pressure (IOP) before, during, and after puberty in male Dutch-belted rabbits.<br />

Methods: Twenty male Dutch-belted rabbits were acquired at 8 weeks of age and their light/dark cycle reversed. Ocular biometrics and IOP were measured every 4 weeks between the ages of 10 and 34 weeks. Data collected included IOP by pneumatonometry at 10 AM and noon, central corneal thickness (CCT) by ultrasonic pachymetry, anterior chamber depth (ACD) by optical pachymetry, and corneal diameter measurements.<br />

Results: All outcome variables showed statistically significant change during puberty (2 way ANOVA p<0.0001). Central corneal thickness increased from 316 ± 13 µ at 10 weeks to 337 ± 13 µ at 30 weeks. Anterior chamber depth increased from 1.93 ± 0.25 mm at 10 weeks to 2.56 ± 0.11 mm at 30 weeks. Corneal diameter increased from 11.8 ± 0.8 mm at 10 weeks to 13.0 ± 0.7 mm at 30 weeks. IOP at 10 AM increased from 24.3 ± 1.3 mmHg at 10 weeks to 26.6 ± 2.8 mmHg at 30 and 26.82 mmHg at 34 weeks after peaking at 28.7 ± 2.6 mmHg at 22 weeks. The decrease in IOP corresponds with the slowing of change in ocular growth.<br />

Conclusions: Significant non-linear changes were observed in the anterior segment and IOP of Dutch-belted rabbits through puberty. A decrease in IOP is seen as ocular growth and pubertal changes slow at weeks 30-34. This may be the result of increased uveoscleral outflow via the deepening of the anterior chamber and increased surface area of the ciliary body band that is exposed to aqueous in the anterior chamber or via a similar mechanism increasing the area of exposed Schlemm's canal or stretching of the trabecular meshwork beams. Evaluation of aqueous humor dynamics will give further insight into the mechanism for the decrease in IOP observed and may reveal new therapeutic targets for the treatment of glaucoma.<br />