Impact Of Eye Movement (Despite Tracking) On Hoa During Ray Trace Based Lasik

To examine the change in higher order aberration (HOA) following ray trace based LASIK and to examine the influence of eye movement during LASIK surgery.

Single Site, Private Ophthalmology, Sydney Australia

Raytrace based LASIK creates a personalised ablation profile by creating an individualised eye model using anatomical features such as tomography, corneal thickness, ACD, AL and wavefront measurement. During treatment the pupil is actively tracked to apply the ablation appropriately.  In the present study, HOA of 500 eyes and the impact of the tracked eye movement during surgery is examined. HOA was assessed pre operatively and 3 months post operatively.

Total HoA RMS in both eyes (n=500 eyes) increased marginally from 0.31±0.10 to 0.39±0.10 (p<0.001) post operatively. Spherical aberration decreased (OD 0.09±0.12 to 0.06±0.15, p<0.001; OS 0.09±0.12 to 0.06±0.15, p<0.001). Increase in vertical coma contributed to the bulk of increase in total HoA (OD -0.02±0.15 to -0.11±0.20, p<0.001; OS -0.04±0.15 to -0.09±0.20,p<0.001).  Post operative vertical coma was moderately correlated with small ablation decentration (OD: β=0.54, p<0.001; OS: β=0.47, p<0.001). The latter was correlated weakly with intraoperative vertical eye movement (OD: r=0.23, p=0.001; OS: r=0.24, p<0.001).

Increase in HoA is statistically but not clinically significant and spherical aberration decreases post ray trace based LASIK. The HOA increase results from an increase in vertical coma which correlates with vertical bells phenomenon during laser.