Abstract
Purpose To evaluate the corneal Functional Optical Zone (FOZ) and the Effective Optical Zone (EOZ) of the ablation, among eyes that underwent LASEK/Epi-LASEK treatments for hyperopic astigmatism. Methods Twenty LASEK/Epi-LASEK treatments with mean defocus +2.21 ± 1.28 D performed using the SCHWIND AMARIS were retrospectively evaluated at 6-month follow-up. In all cases pre-/post-operative Corneal-Wavefront analyses using the Keratron-Scout (OPTIKON2000) were performed. FOZ-values were evaluated from the Root-Mean-Square of High-Order Wave-Aberration (RMSho), whereas EOZ-values were evaluated from the changes of Root-Mean-Square of High-Order Wave-Aberration (ΔRMSho) and Root-Mean-Square of the change of High-Order Wave-Aberration (RMS(ΔHOAb)). Correlations of FOZ and EOZ with Planned Optical Zone (POZ) and Defocus correction (SEq) were analyzed using a bilinear function. Results At six-month, defocus was −0.04 ± 0.44 D, ninety percent eyes were within ± 0.50 D from emmetropia. Mean RMSho increased 0.18 ± 0.22 μm, SphAb −0.30 ± 0.18 μm, and Coma 0.07 ± 0.18 μm 6-month after treatment (6-mm diameter). Mean FOZ Pre was 7.40 ± 1.48 mm, mean POZ was 6.76 ± 0.22 mm, whereas mean FOZ Post was 5.53 ± 1.18 mm (significantly smaller, p < 0.0001; bilinear correlation p < 0.005), mean EOZ ΔRMSho 6.47 ± 1.17 mm (bilinear correlation p < 0.005), EOZ RMS(ΔHOAb) 5.67 ± 1.23 mm (significantly smaller, p < 0.0005; bilinear correlation p < 0.05). EOZ positively correlates with POZ and declines steadily with SEq. A treatment of +3 D in 6.50-mm POZ results in 5.75-mm EOZ (7.75-mm NPOZ), treatments in 7.00-mm POZ result in about 6.25-mm EOZ (8.25-mm nomogrammed POZ). Conclusions FOZ Post was significantly smaller than FOZ Pre. EOZ ΔRMSho was similar to POZ, whereas EOZ RMS(ΔHOAb) was significantly smaller. Differences were larger for smaller POZ or larger Defocus. SEq up to +2 D result in EOZ, at least, as large as POZ. For SEq higher than +2 D, a nomogram for OZ can be applied.
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