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J. Choremis, A. Wallerstein, M. Cohen, P. Demers, M. Bashour, J. Antoniou; Comparison of Programmed Optical Zone Size and Effective Treatment Zone Size for B &L; Plano-Scan and Zyoptix LASIK . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2630.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To measure the effective treatment zone size (ETZ) on the B&L; 217z laser with Plano-Scan software and Zyoptix software. To compare these measurements to programmed optical zone size (POZ). To compare the ETZ between the two ablation techniques. Methods: Retrospective chart review of 50 myopic Plano-Scan and 50 Zyoptix eyes. Orbscan topography was performed pre-operatively and post-op at the one month visit. The area of a best fit circle or oval on the ablation, on the anterior elevation difference maps, was used to calculate the ETZ. The outer edge of the green zone which corresponds to a 10um depth difference was used as the sharp demarcation to outline the ETZ. The POZ was calculated as the area of the circle. Results: Preliminary results include 31 Zyoptix and 35 Plano-Scan treated eyes. The mean spherical equivalent (SE) refraction for this study group was -5.75D (+/- 1.7D). For both Plano-Scan and Zyoptix treatments there was a strong positive correlation between the POZ and the ETZ. The ETZ/POZ ratio was 63.5% (+/- 9.8%) and 69.2% (+/- 8.6%) for Zyoptix and Plano-scan respectively in the low myopia group with SE -2.00D to -5.75D. This difference between the ablation techniques was statistically significant with p< 0.05. In the high myopia group with SE -6.00D to -10.00D the ETZ/POZ ratio was 72.2% (+/- 7.2%) and 69.2% (+/- 6.3%) for Zyoptix and Plano-Scan respectively, a non significant difference. Conclusion: The overall ETZ is appreciably smaller than the POZ for both Plano-Scan and Zyoptix ablations. This has important implications in surgeon planning to avoid night vision disturbances. The difference in ETZ/POZ ratio between ablation techniques is to be discussed.
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