Spectroscopic measurements during the corneal collagen cross-linking procedure for in vitro human corneas

The transmittance of UVA light through the human preserved cornea of over 400 mu m thickness during the corneal collagen cross-linking procedure has been measured spectroscopically. The 25 corneas, (average thickness of 570 mu m), preserved in OptisolGS, were washed with saline, desepithelization was performed, and the cornea was laid on the lid of a Chiron Ophthalmics corneal storage chamber. A UV-VIS optical fiber was positioned at the crystalline position (10mm after the endothelium) and fixed in a 3mm hole of the chamber and then connected to a spectrophotometer to detect the amount of delivered UVA light on the endothelium. Current procedure protocol was performed, i.e., one drop of riboflavin 0.1%, 400 mOsm, was applied on the naked cornea, every 5 minutes (total of 12 drops). The UV irradiation (365+/-5 nm, 3mW/cm(2), 1.51 mW, 5.405 J/cm(2)) was performed after 30 min of instillation for an additional 30 min. The average transmittance of the desepithelized cornea without Riboflavin at the crystalline position is 65.8%'; after the 1st drop of Riboflavin, transmittance is 51.4%; after 2nd drop, 46.1%; after 3rd drop, 41.9%; after 4th drop, 38.7%; after 5th drop, 35.9%; after 6th drop 33.6%; after 7th drop, 31.0%; after 8th drop; 28.8%; after 9th drop, 27.2%; after 10(h) drop, 25.4%; after 11th drop, 23.9%; and finally after 12th drop, 22.5%. The average transmittance in terms of energy during the 30 min irradiation procedure fluctuated from 0.930 to 0.675mW/cm2.