Purpose: LASIK allows not only to correct for the refractive error but also to extend depth of focus by inducing controlled amounts of spherical aberration (SA). However the success of the procedure may depend on the particular SA values required by each patient. We evaluate a customization procedure where the optimum values of SA were determined for each patient using an adaptive optics vision analyzer before the surgery.
Methods: A group of 38 hyperopic/presbyopic patients were evaluated before and after surgery using the Adaptive Optics Vision Analyzer (AOVA, Voptica SL, Murcia, Spain). This is a clinical instrument to perform vision testing with full control of the optical aberrations induced in the patient’s eye non-invasively. The AOVA includes a wave-front sensor, a liquid crystal on silicon spatial light modulator to induce any desired aberration profile on the patient’s eye, and a micro-display to present the visual stimuli. Visual acuity was measured for defined combinations of residual defocus and SA at infinity, 60 cm and 40 cm. In each patient, the sets of optimized values of defocus and SA required to maintain adequate near and far VA were determined. Then, and taking into account the patient’s corneal asphericity (Q-value), the LASIK procedure (WaveLight Allegretto Wave Eye-Q Laser, Alcon) was settled to induce the desired range of negative SA in one eye. The fellow dominant eye was treated only to reach emmetropia without inducing SA. After the surgery, through focus VA, residual refraction, and SA was measured using the AOVA in each patient.
Results: The average Q-value changed from -0.1 to -0.6 in the dominant eyes, and from -0.05 to -0.8 in the eyes treated for inducing extra asphericity. The average value of SA providing an extended depth of focus was around -0.2 microns for 4.5-mm pupil. In these eyes, the required positive addition for intermediate and near vision changed from +1.00D and +1.70D to +0.40D and +1.00D respectively. In those eyes with no SA induced, the positive addition required hardly changed.
Conclusions: Hyperopic presbyopic patients are ideal candidates for customized LASIK to induce an extended depth of focus. This procedure can be optimized when mediated with adaptive to predict the right amount of SA to be induced. These results suggest that the LASIK guided with and AOVA can provide improved visual outcomes at all distances.