Comparison of visual and refractive outcomes following Intacs implantation in keratoconus eyes with central and eccentric cones

Objective: To compare visual and refractive outcomes after Intacs implantation in keratoconus eyes with central and eccentric cones and to validate the current nomogram used to select Intacs size.

Design: Comparative study.

Participants: The charts of 20 patients in a single practice, who had symmetric (15 eyes) or asymmetric (16 eyes) implants, were retrospectively reviewed.

Methods: Intacs were implanted by a single surgeon using a femtosecond laser. Based on Scheimpflug imaging, central and eccentric cone patterns received symmetric and asymmetric Intacs, respectively. Uncorrected distance visual acuity (UDVA) and best-corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), and keratometry (K) values were measured pre- and postoperatively.

Results: The mean improvement in UDVA and CDVA in the symmetric group was 3.8 ± 0.9 and 0.6 ± 0.5 lines, and in the asymmetric group was 3.4 ± 0.7 and 1.8 ± 0.3 lines, respectively. The mean change in manifest refraction spherical equivalent (MRSE), refractive cylinder, and average K in the symmetric group was 2.40 ± 0.71 D, 0.02 ± 0.90 D, and -2.71 ± 0.50 D, and in the asymmetric group was 2.67 ± 1.21 D, 0.05 ± 0.47 D, and -2.35 ± 0.40 D, respectively. In CDVA, asymmetric Intacs showed statistically significant and better results than symmetric Intacs (p = 0.0016). There was no statistically significant difference between the means of symmetric and asymmetric implantation for UDVA, MRSE, average K, or corneal astigmatism (p > 0.05).

Conclusions: The implantation of symmetric and asymmetric Intacs segments in keratoconus eyes with central and eccentric cones, respectively, was found to have comparable visual and refractive outcomes except for CDVA, which improved significantly more in the asymmetric group. This study also demonstrates the validity of the nomogram used.