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F. Luengo Gimeno, C. Chan, L. Li, A. C. Fong, D. T. Tan, J. S. Mehta; Use of ACE Tracker Following Femtosecond Ablation; VisuMax and IntraLase. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2873.
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© ARVO (1962-2015); The Authors (2016-present)
Femtosecond lasers (FSL) have been shown to produce accurate corneal flaps for LASIK surgery. However, opaque bubble layer (OBL) is an inherent problem with all femtosecond lasers. Excessive OBL may interfere with the function of an eye tracker. The aim of our study is to determine the efficiency of the ACE tracker, following FSL flap creation with either the IntraLase (IL) or the VisuMax (VM) FSL.
Prospective study on 86 eyes from 47 consecutive patients. 41 eyes (47.67%) had flap creation by IL FSL, 45 eyes (52.32%) by VM FSL. ACE tracker was initiated three times in standardized background illumination to obtain iris recognition. The mean target optical zone was 6.34mm (6.00 to 6.5mm). Eye tracking success was determined if the eye movements could be followed despite the presence or not of OBL. A uni/multivarite logistic regression analysis was performed.
We studied 86 eyes (mean values: age 29.42y (20 to 51), sphere -5.64 D (-9.75 to -0.25, SD 2.17), cyl 1.65 D (-3.75 to 0.00, SD 1.63), optical zone 6.34 mm (5.6 to 7, SD 0.20), keratometry 43.48D (40.1 to 42.8, SD 1.32), flap thickness 109.30um (90 to 115, SD 5.21). 41 eyes were treated with IL, 37 (90.24%) were able to be tracked. VM was used on 45 eyes of which 43 (95.56%) were able to be tracked. No specific pattern of OBL formation was seen with either FSL even though VM tended to cause OBL in the mid-periphery cornea. The LASIK procedure could be completed in all eyes after disabling the tracker in the non-tracked cases. 9 eyes received Zyoptix Aspheric treatment and 77 Zyoptix TS treatment. Univariate analysis showed a significant association between positive tracking and the smaller optical zone (p=0.03). There were no statistical differences between the two FSL with respect to eye tracking.
Although these 2 FSL have differences in their mechanism of action, they produce similar patterns of OBL which do not significantly interfere with the ACE tracker. Patients can benefit synergistically from both these new advancements in laser technologies.
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