As surgeons, we understand that every procedure presents some degree of risk to our patients. Refractive surgery being no exception, the conventional LASIK procedure has long been known to induce higher order aberrations (HOA) in its recipients, the most significant of which have been spherical, then coma, following by trefoil aberrations.¹ The question has been then: what role do ocular aberrations play in overall visual performance?

Over the last several years, the research community has made a concerted effort to better understand this relationship between HOAs and visual acuity, with compelling results. A number of studies now indicate that in order to achieve optimal outcomes with refractive surgery, ophthalmologists need to target for zero ocular aberrations.² One study in particular was able to show causation between greater HOAs and poorer postoperative best corrected visual acuity (BCVA) (Figure 1).³

In theory, these findings would suggest that one of today's available LASIK strategies would be more successful than the others. Current options include:

Figure 1: As HOAs increased, BCVA began to decline.

i) traditional LASIK, which we already know induces HOAs

ii) wavefront 'optimized' LASIK, which attempts to maintain preoperative HOAs

iii) wavefront 'guided' LASIK, which strives to reduce or possibly even eliminate all HOAs.

I recently conducted a study to test this theory, and took a retrospective look at the relationship between HOAs and visual outcomes in patients who had received 'wavefront optimized' and 'wavefront guided 'ablations.⁴ We were able to conclude, as outlined below, that for the majority of patients, nearly 90% in our study, wavefront guided LASIK provided better optical results than wavefront optimized LASIK.

Optimized vs. guided

During the last quarter of 2005 and 2006, I performed both wavefront optimized and wavefront guided laser procedures. Wavefront optimized ablations were performed with the Wavelight Allegretto Wave (Sterling) laser whose treatment is based on sphere and cylinder, while wavefront guided ablations were carried out by the Advanced Medical Optics (AMO) combined Wavescan and Visx Star4 excimer laser, CustomVue, whose treatment is based on wavefront. All flaps were created with the IntraLase femtosecond laser (AMO), as it has become my standard of care.

Figure 2: Guided ablation was able to maintain HOAs 20% better than optimized ablation.

Of the total 211 patients who were included in the study, 102 received optimized ablations, while the remaining 109 received guided ablations. The treatment range for the refractive surgery ranged from +3.00D to -11.00D, with less than 3D of astigmatism. Preoperative and postoperative wavefronts were analysed with 6mm pupils on an OPD scan (Nidek) for spherical, coma, and trefoil and all HOAs, and BCVAs and uncorrected visual acuities (UCVA) were recorded.