The Effect of Transscleral Pressure on Human Scleral Thickness and Hydration

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 (p0.10). 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.