INTRASTROMAL CORNEAL RING SEGMENTS AND PHAKIC INTRAOCULAR LENS IMPLANTATION FOR KERATOCONUS CORRECTION: FIVE-YEAR LONG-TERM FOLLOW-UP

The purpose of the study was to evaluate the short and mid-term efficacy, safety, and predictability of sequential implantation of ICRS and a phakic intraocular lens (pIOL) for therapeutic and refractive correction of keratoconus.

Keratoconus is an asymmetrical and progressive corneal ectasia characterized by irregular astigmatism, myopia, and higher order aberrations, causing loss of visual acuity. Intrastromal corneal ring segments (ICRS) implantation is an effective method for reducing astigmatism and higher-order aberrations. Many patients with keratoconus have moderate to high myopia and, even though, ICRS implantation significantly improves the ectasia, most patients require contact lenses or spectacles to correct the residual refractive error. 

A retrospective study was designed, comprising patients with keratoconus who had Ferrara-type ICRS implantation followed 6 to 12 months later by pIOL implantation for ametropia correction. Over a 1- and 5-years follow-up period after pIOL implantation, the main outcome measures were uncorrected and corrected distance visual acuity (UDVA and CDVA, logMAR scale), spherical equivalent refraction in diopters (D), topography parameters and endothelial cell density. Efficacy and safety indexes were calculated at 1 and 5 years of follow-up.

The study included 28 eyes who completed the 5-year follow-up. Mean age was 28,34 ±3,56 years at the time of ICRS implantation. Seven iris-claw foldable lenses and 21 posterior chamber sulcus supported lens were implanted. Around 14,3% (4 eyes) of the lenses implanted were toric. The mean UDVA was 0.92 ±0.14 preoperatively, 0.71 ±0.13 6-months after ICRS implantation (p=0,46), and 0.26 ±0.25 6-months after pIOL implantation (P<0,01), with a significant decrease at 5 years (0.32 ±0,22, p<0.05). The mean CDVA was 0.39 ±0.27, 0.25 ±0.24 (p=0,10), and 0.17 ±0.24 (p<0,01), respectively, and remained stable 5 years (0.20 ±0.22, p=0.76). Twelve months after pIOL implantation, the efficacy and safety indexes were equal or higher than 1.0. Manifest cylinder decreased after ICRS implantation, from -2,97 ±1,55D to -1,47 ±1,09D after 12 months (p<0.01) and -1,54 ±0,97D at 5 years (p=0,02); the spherical equivalent decreased significantly after pIOL implantation, from -8,72 ±5,64D to -0,96 ±1,35D at 12 months (p<0,01), remaining stable at 5 years (-1,03 ±0,97D; p>0.05). Spherical equivalent was within ±0.50D of the attempted correction in 12 eyes (42.9 %) and within ±1.00D in 20 eyes (71.4%). Mean endothelial cell density decreased from 1980 ±252 cells/mm² after ICRS implantation to 1648 ±310 cells/mm² 12-months after pIOL implantation (p=0,08), remaining stable at 5 years after pIOL implantation (1549 ±343 cells/mm²; p=0.84).

Sequential ICRS and pIOL implantation provided good visual and refractive outcomes, indicating that it is a predictable procedure for refractive correction of keratoconus. In our study these results remained stable over a 5-year follow-up period.