[Refractive outcome and prognostic factors for success of intracorneal ring segment implantation in keratoconus: A retrospective study of 75 eyes].

PURPOSE: To define the prognostic factors for success and to evaluate the predictability of intracorneal ring segments (ICRS) in the treatment of keratoconus.

METHODS

In this retrospective study conducted at the University Hospital of Nantes, Keraring ICRS were implanted in 75 eyes of 65 patients with keratoconus. Best spectacle corrected visual acuity (BSCVA), manifest refraction and corneal topography were analysed. To define prognostic factors, we compared the results of 2 groups: "IMP" (gain of at least 2 lines of BSCVA) and "ROS" (the others). We evaluated the predictability of the nomogram with a mathematical model proposed by Pena-Garcia et al. (IOVS 2012).

RESULTS

At 3 months, BSCVA improved from 0.3 to 0.2 logMAR (P<0.05). A total of 61 % of the patients experienced a gain of at least 1 line of BSCVA. Spherical equivalent decreased by 2.32 diopters (D), cylinder decreased by 2.47 D, and maximal keratometry by 2.62 D (P<0.05 for each compared with preoperative values). A total of 90 % of the patients whose BSCVA did not improve achieved a significant refractive improvement. A preoperative BSCVA>0.3 logMAR is a prognostic factor for gain of at least 2 lines of BSCVA (P=1.6E-3). Predictability was fair: only 43 % had a±1D difference from the spherical equivalent predicted by the nomogram. There was no statistically significative difference between gain or loss of BSCVA predicted by the mathematical model and the postoperative results.

CONCLUSIONS

ICRS are visually and refractively effective. Predictability could be improved by using mathematical models and knowledge of prognostic factors for success, allowing for better patient selection.