Three month follow-up of changes in the rabbit cornea after photoablation with a pulsed scanning beam at 213 nm

摘要

Abstract: A scanning beam of nano-second pulses at 213 nmflattens the cornea as predicted. However, there is aconsiderable variability in the flattening and theablation is not safe. Ablation for 16 D flattening withan active spot overlap of 50% induced 8.9 $POM 5.3 D (n$EQ 7) as measured by the TMS topography system (ring 7average) and 5.8 $POM 4.1 D (n $EQ 5) as measured withthe SK-1 (2 mm zone) system. Ablation for 6 Dflattening with an active spot overlap of 70% inducedapproximately 2 D flattening to 2 D steepening (n $EQ3) as measured with the TMS (ring 7) and 6.6 $POM 4.33D (n $EQ 7) flattening as measured by SK-1 (2 mm zone)keratometry. There was no change in IOP at 12 weeksafter as compared to before ablation. There was a netincrease of central and peripheral corneal thickness at12 weeks after the ablation as compared topreoperatively. Epithelial defects remained up to 4weeks after ablation. After four weeks, vessels hadinvaded the cornea in 30% of the cases and remainedthroughout the three months observed. It is concludedthat 213 nm nano-second pulses can be used forflattening the cornea but the system should not be usedfor clinical trials in humans until the adverse effectscan be avoided.!12