The Effect of Transscleral Pressure on Human Scleral Thickness and Hydration

Lee, Sang Bumm; Kwon, Jung Yoon; Edelhauser, Henry F

Abstract

PURPOSE: The purpose of this study was to evaluate the effect of transscleral pressure on the thickness and hydration of the human sclera.
METHODS
Scleral sections excised from moist-chamber-stored human globes were mounted in a perfusion chamber that can create transscleral pressure. The scleral thickness was measured at 15-minute intervals using ultrasonic pachymetry with pressure changes of 15, 30, and 60 mmHg every 2 hours. The scleral hydration was measured by maintaining a constant pressure (15, 30, and 60 mmHg) for 4 hours, weighing the hydrated tissue, then drying for 24 hours at 120degrees C, and finally weighing the dry tissue.
RESULTS
The changes of scleral thickness from the initial control thickness in the 7-mm perfusion chamber (n=6) were -0.38+/-2.11%, 0.26+/-2.99 %, and -3.92+/-3.40% at 15, 30, and 60 mmHg, respectively. In the 10-mm perfusion chamber (n=5), the thickness changes were -0.56+/-1.35%, -1.05+/-1.63%, and -2.71+/-1.60% at 15, 30, and 60 mmHg, respectively. Scleral thickness was slightly decreased with the increase of transscleral pressure. There was a statistically significant decrease in scleral thickness from 30 mmHg to 60 mmHg in the 7-mm perfusion chamber (p<0.05). Changes of the scleral hydration value in the 7-mm perfusion chamber were -0.79+/-1.06% (n=5), 0.66+/-1.40% (n=5), and 0.05+/-1 . 3 0 % (n=5) at 15, 30, and 60 mmHg, respectively. There were no statistically significant changes in the scleral hydration with transscleral pressure change of 0~60 mmHg (p>0.10).
CONCLUSIONS
The scleral hydration remained essentially unchanged with the transscleral pressure change of 0 ~ 60 mmHg, whereas the scleral thickness showed a slight decrease with the increase of transscleral pressure. Further histologic studies will be needed to assess the ultrastructural change of human sclera in the future.