Holographic interferometry of excimer-laser-ablated bovine eyes: first results

PURPOSE: To investigate the effects of areal corneal ablations of different depth on the biomechanical properties of the cornea. METHOD: The qualitative change of the holographic interferometric fringe pattern of enucleated bovine corneas due to areal mechanical ablations (group A) of 35% and 70% depth of the central cornea and 15, 30, and 50% excimer laser ablations in each eye (group B) was investigated. RESULTS: Ablations of 50% (group B) and 70% (group A) showed a significant variation of the fringe pattern as an effect of the corneal weakening. 15% excimer laser ablations of 5 mm diameter did not result in noticeable changes of the fringe pattern. Half of the 30% ablated corneas in group B showed newly appearing fringes within the area of ablation, indicating a local reduction of the corneal stiffness after ablation. CONCLUSION: The thickness of the remaining tissue is very important for the biomechanical behavior of the cornea after areal ablations. There are interindividual differences regarding the change of material properties due to excimer laser ablation of 30% depth of ablation.