Changes in Aqueous Humor Dynamics associated with Growth and Puberty

Abstract

 

Purpose

 

Changes in aqueous humor dynamics associated with growth and puberty have therapeutic implications for the treatment of elevated intraocular pressure (IOP) in children and young animals; yet limited information exists on the effect of growth and puberty on aqueous humor dynamics. This study describes the changes associated with growth and puberty in male Dutch belted rabbits.

 

Methods

 

Twenty rabbits were acquired at 8 weeks of age. After a reversal of the light/dark cycle, measurements were made every 4 weeks between the ages of 10 and 34 weeks. These included intraocular pressure (IOP) by pneumatonometry at 10 AM and noon, biometric measurements (reported separately), aqueous flow by fluorophotometry, outflow facility by tonography and episcleral venous pressure by venomanometry.

 

Results

 

IOP increased from 24.07 ± 1.19 mmHg at 10 weeks to 29.21 ± 1.75 mmHg at 18 weeks. This was followed by a decrease to 26.68 ± 1.49 mmHg at 26 weeks before increasing to 29.53 ± 1.90 mmHg at 34 weeks (figure). Aqueous flow peaked at 14 weeks at 2.42 ± 0.90 µl/min followed by a decrease at 30 weeks [TC(1] to 1.91 ± 0.80 µl/min (2 way RMANOVA p = 0.02). Tonographic outflow facility varied between 0.30 ± 0.33 and 0.39 ± 0.75 µl/min/mmHg throughout development (2 way RMANOVA p = 0.97). Episcleral venous pressure was the lowest at 10 weeks at 7.82 ± 1.32 mmHg and highest at 22 weeks at 14.49 ± 2.64 mmHg (2 way RMANOVA p <0.0001).

 

Conclusions

 

The initial IOP increase appears to coincide with increasing body weight and a period of increasing episcleral venous pressure. The IOP trough at 26 weeks could not be explained by changes in aqueous flow, outflow facility or episcleral venous pressure which suggests development of and increased flow through the uveoscleral pathway. The potential mediators of the significant IOP decrease at puberty may provide novel therapeutic targets for IOP lowering.