P 161 In vitro evaluation of surface regularity following ablation with seven different excimer lasers

Purpose: To invcsligatc the polcnlial bcnclit of a lnrgcr ablation zone lix myopic PRK Methods: We reviewed the charts ,of patients who were included in the prospective evaluation of the Summi: Technologies lasers (Waltham, MA) with a minimum of 6 months follow up. 30 eyes treated with the Omnimed excimer laser (ablation zone 6 mm) were compared to 30 matched eyes treated with the Excimed model (abln!ion zone 5 mm). Surgical pammelcrs such as depth of ablalion, number of pulses, and duration of procedure were correlated to postoperative outcome including uncorrected and best corrected visual acuity, spherical equivalent and cylinder under cycloplegia, reported glare and halos. and subjective reduction of vision in dim light conditions. In addition, haze, cents-ation of ablation, amount of initial flattening of central cornea, regressicn of refractive effect and the rate of central island formation at 3 months were also assessed. Results: Larger ablation (6 mm) was associated with a more progressive flattening of the central cornea and with less regression over time. I Iowcvcr, oo significant diffcrcnce was obscrvcd io term of hwc or reported halos, while a higher incidence of central island was obscrvcd io this group as compared to the 5 mm group. Conclusion: These results suggest that a huger ablation zooe may be benelicial in patienls with large pupil area as well as itI pnticols with an expected healing response above standard level.