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Georgios Labiris, Athanassios Giarmoukakis, Anna Koutsogianni, Theocharia Sideroudi, Vassilios Kozobolis; Evaluation Of The Level Of Agreement Between Intended And Measured Ablation In Wavefront Optimized (WFO) Myopic Spherocylindrical Correction. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2844.
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To evaluate the level of agreement between intended and measured ablation of the WFO profile, corrected by the Wellington nomogram and assess the impact on refractive outcomes.
86 patients who underwent in both eyes either LASIK (86 eyes) or PRK (86 eyes) WFO treatment were included in the study. The Allegretto excimer laser (software version: 2.020) was used in all cases. For the LASIK group, the Carriazo-Pendular microkeratome with 130µm cutting head was used for the creation of the flap (the hinge was created at 12 o’clock position). Differences between intended and measured ablation were evaluated with Scheimpflug camera. Refractive outcomes were evaluated by means of postoperative spherical equivalent (postSE) and postoperative defocus equivalent (postDE) and contrast sensitivity.
Both PRK and LASIK groups demonstrated significant differences between intended and measured ablation (16.7 + 8.5, p<0.001 & 11.8 + 18.5, p<0.001, respectively). For both groups, the intended ablation was the primary determinant of the measured difference (r-square 0.769 & 0.765, respectively). PRK spherocylindrical corrections over 100µ had significant impact on both postSE and postDE (p:0.044, p:0.05, respectively), while LASIK spherocylindrical corrections over 100µ had significant impact only on postDE (p:0.04). No differences were detected in contrast sensitivity for both groups. Moreover, measured differences had no impact on the number of re-treatments or ectasias (none observed).
The WFO profile corrected by the Wellington nomogram is an efficient solution for myopic spherocylindrical errors. However, its efficacy is reduced in higher refractive errors that require higher intended ablations. The aforementioned results, suggest that the nomogram should be further improved to address differences between intended and measured ablations and especially deviations from the desired visual outcome.
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