Keratoconus correction using intrastromal corneal ring segments and posterior chamber phakic intraocular lens implantation

The results and conclusions of the study by Alfonso et al.1 of combined intrastromal corneal ring segments (ICRS) (Keraring, Mediphacos Ltd.) and posterior chamber phakic intraocular lens (pIOL) (Visian Implantable Collamer lens [ICL], Staar Surgical) implantation in patients with keratoconus coincide with those presented by Navas et al.,A who conducted a similar evaluation of 7 eyes of 6 patients with keratoconus who had sequential ICRS. In that study, 6 eyes received ICRS (Intacs, Addition Technology, Inc.) and 1 eye, corneal rings (Visiontech Medical Optics Ltd.) and the ICL; 4 eyes received the toric ICL and 3, the spherical ICL, as needed (Figure 1).Figure 1: Clinical slit-lamp photograph and optical coherence tomography showing ICRS and ICL (Superior, triangular shaped Cornealring; inferior hexagonal shaped INTACS). Arrow shows the rhomboidal mark of the toric ICL.In the Navas et al. study, the mean uncorrected distance visual acuity (UDVA) improved from 0.05 ± 0.03 preoperatively to 0.57 ± 0.13 after both procedures (P=.0001 for all). The mean manifest refraction spherical equivalent decreased from −11.03 ± 4.80 diopters (D) preoperatively to −0.46 ± 0.52 D after both procedures (P=.0003) with at least 9 months of follow-up (mean 38.18 ± 18.7 months). Similar results were reported by Alfonso et al.1; the outcomes are consistent with our safety index for both procedures, 1.77 at 36 months of follow-up, and no patient in either study lost 2 or more lines of corrected distance visual acuity. The postoperative mean UDVA was slightly better and had a lower standard deviation in the Navas et al. study. However, Alfonso et al. reported a final spherical equivalent of −1.198 ± 1.326 D in contrast to −0.68 ± 0.45 D (0 to −1.25 D) in the Navas et al. study, probably because of more predictable results with the toric ICL than with corneal relaxing incisions. In the Navas et al study, we used 6.0 mm optic diameter ICRS in 6 cases and 5.0 mm optic diameter in 1 case; there was no difference in the final outcome. We agree with Kamburoğlu et al.2 that combined ICRS and anterior chamber iris-fixated pIOLs in keratoconus eyes is technically challenging and the nonflexible version requires creation of a 6.5 mm scleral tunnel. We prefer the ICL because of the quality of the optics and the stability of the toric version in the treatment of high astigmatism, as previously reported for the optical correction of stable keratoconus with toric pIOLs.3 Despite the fact that the antiastigmatic clear cornea relaxing incisions are a reliable and practical way of reducing preexisting corneal astigmatism,4 the effects of these incisions are not predictable in an ectatic cornea or after modification of the curvature with ICRS implantation. In the studies by Alfonso et al. and Navas et al., the mean age of the patients was similar (38 versus 37 years). Further studies should consider younger cases in which keratoconus progression is still an important issue. Overall, we agree with Alfonso et al.1 that the implantation of ICRS and ICL is a safe and effective sequential approach for the treatment of keratoconus.