Corneal and scleral distensibility ratio on enucleated human eyes.

The rigidity of the cornea and sclera was measured on ten enucleated human eyes by means of the distensibility ratio test. The eyes were obtained from the Medical Eye Bank of Maryland with the donor age ranging from 63 to 86 years. The time of anterior-posterior and equatorial measurements varied from 2 to 32 hours after enucleation. Changes in distensibility were recorded with a circumference gauge when pressure was elevated over a 100 mm. Hg pressure span. Scleral distensibility was greatest when a pressure change from 20 to 30 mm. Hg was recorded and decreased exponentially until approximately the 90 mm. Hg pressure level. Depending on the time elapsed after enucleatidn, the data on corneal distensibility was a curve of an S-shape pattern with maximum and minimum values. Maximum was recorded near the 50 mm. Hg level on a freshly enucleated eye. The maximum value increased and shifted toward lower pressure levels as time between enucleation and measurement was prolonged. In a test taken 32 hours after enucleation the maximum value was recorded at the initial pressure change from 20 to 30 mm. Hg. At this time interval the S-shape pattern of the curve was absent and the distensibility decreased uniformly as pressure was elevated. A statistical evaluation for the scleral part of these eyes showed no significant deviation. The characteristic of the corneal distensibility curve, however, showed clearly that the comeal distensibility was a function of two variables, namely age of donor and time elapsed after enucleation.