MULTIZONE AND TRANSITION ZONE PHOTOREFRACTIVE KERATECTOMY FOR HIGH MYOPIA

BACKGROUND: Variations in ablation profile may alter the stability of refraction and cause adverse effects in photorefractive keratectomy. W e compared the benefits of multizone and transition zone ablation in t he treatment of high and extreme myopia. METHODS: A scanning excimer l aser system, Nidek EC-5000 was used with three-zone treatment and our results were compared retrospectively with results obtained in a group with a conventional ablation profile using a transition zone. RESULTS : Six-month follow-up data were available for 65 eyes with a transitio n zone and 46 eyes with three-zone treatment. Postoperative mean (+/-S D) healing time was 2.98 days (+/-0.12) and 3.02 days (+/-0.15), and n ight vision disturbances were 16% and 11.5% respectively, (p>0.05). Re fractive regression was also similar in the two groups; uncorrected vi sual acuity of 20/40 or better was 90.77% and 89.14%. At 6 months post operatively, the mean (+/-SD) corneal clarity score was 0.61 ( +/-0.29 ) in the transition zone group, and 0.51 (+/-0.07) in the multizone gr oup (p<0.05). CONCLUSION: No discernible differences between treatment s were found in either epithelial healing or refractive outcome, such as regression, between the groups. Corneal haze was less in eyes treat ed with three-zone ablation.