Abstract
Purpose :
This study tested the integration of a novel corneal correction concept in presbyopia surgery to minimize corneal distortion. The correction was based on achieving a corneal symmetrical shape. The hypothesis is that a point-symmetric thickness reduces postoperative off-centered corneal shift caused by Intra Ocular Pressure and helps to a progressive alignment of the visual axis
Methods :
A retrospective study of 122 healthy eyes of 62 presbyopic patients (mean age = 49 ± 4 years; SE = -3.44 ± 2.09 D) was performed. Patients underwent Lasik for presbyopia and refractive error including a customized corneal correction to achieve a symmetrical shape in terms of corneal thickness. The correction was performed by an overlap of semi-cylinder ablations separated by 90° or 45° in groups 1 and 2, respectively. An image processing routine coupled to Orbscan II measurements was applied to characterize the symmetry of corneal thickness in the 3-5 mm zone. The progression of the posterior corneal elevation and the posterior corneal curvature was evaluated over the first postoperative year. The UDVA and UNVA were compared as well
Results :
84 eyes of 42 patients (mean age = 50 ± 4 years; mean SE = -3.62 ± 2.19 D) were in group 1, and 38 eyes of 20 patients (mean age = 47 ± 4 years; mean SE = -3.04 ± 1.78D) were in group 2. In group 1, no significant symmetry improvement in corneal thickness nor in posterior corneal shape was noticed postoperatively. In group 2, a significant symmetry improvement in corneal thickness was observed at third postoperative month (p = 0.03). Posterior corneal shape (p = 0.04), and alignment of the visual axis, (p = 0.03), significantly improved at the third month. Irregular patterns of the posterior axial map decrease from 57% of patients at preoperative, to 0% at first postoperative year. At 12 months, UDVA was 20/25 or better in 78% of group 1 and 89% of group 2; the UNVA was 20/40 or better in 53% of patients in group 1 and in 100% of patients in group 2
Conclusions :
In group 2, the correction method achieved a significant symmetry improvement in corneal thickness. Posterior corneal shape symmetry and alignment of the visual axis significantly improved from the third month. None of the patients was found with an irregular axial map pattern at first postoperative year. There was a corresponding improvement in UDVA and clearly in UNVA as compared with patients in group 1 where the symmetry correction failed
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.