Abstract
Purpose: :
Corneal thinning by dehydration is a significant safety issue during the corneal-cross-linking procedure. In order to evaluate corneal pachymetry changes induced by different riboflavin preparations we performed an in vitro-trial with human donor corneas.
Methods: :
Nine corneo-scleral buttons of human donors that were not suitable for transplantation were used in this trial. The corneo-scleral buttons were mounted on an artificial anterior chamber filled with air. The air-pressure was increased to 80 mmHG to dehydrate the donor cornea until the corneal thickness was below 600 µm. Thereafter the pressure in the artificial anterior chamber was reduced to 20 mmHg. The corneas were divided into three groups and the following Riboflavin preparations were applied every 2 minutes for 30 minutes: 1) riboflavin with 20% dextrane 2) riboflavin with 1.5% methylhydroxypropylcellulose 3) hypotonic Riboflavin solution. Every ten minutes the corneal pachymetry was measured using the Visante OCT (Carl Zeiss Meditec).
Results: :
The mean baseline pachymetry was 578±31 µm in group one, 534±19 µm in group two and 568±30 µm in group three. In group one a mean loss of pachymetry of 226,7 µm was found after 30 minutes. In group two, pachymetry was reduced by 16,5 µm and in group three pachymetry increased by 39 µm after 30 minutes.
Conclusions: :
Isotonic riboflavin in a solution with 20% dextran results in corneal dehydration and reduction of pachymetry. The use of a hypotonic riboflavin solution results in an increase in corneal pachymetry, but this effect is known to be of short duration. A riboflavin preparation with methylhydroxypropylcellulose in the tested concentration seems to prevent corneal dehydration by still providing sufficient viscosity to coat the cornea.
Keywords: cornea: clinical science • keratoconus