[Femtosecond-assisted Ferrara intrastromal corneal ring implantation for treatment of keratoconus: Functional outcomes at one year].

INTRODUCTION

Intrastromal corneal rings (ICR) have been used for several years for the correction of irregular astigmatism in patients with keratoconus.

OBJECTIVE

To evaluate the effectiveness of femtosecond-assisted ICR implantation for treatment of keratoconus and to define predictive factors of success.

PATIENTS AND METHODS

We undertook a retrospective study of patients with keratoconus who underwent femtosecond-assisted Ferrara ICR implantation between December 2012 and May 2014 at the University Hospital of Besançon. To determinate predictive factors of success, we divided patients into 2 groups based on the gain of at least two lines of best corrected visual acuity (BCVA) at 1 year after surgery ("good responders") or the gain of only one line of BCVA, no change, or the loss of lines of BCVA ("poor responders"). For each group, we analyzed preoperative refractive and keratometric values. Moreover, to verify if preoperative visual acuity could be a predictive factor of success, four groups were created based on initial visual acuity, and postoperative BCVA was compared.

RESULTS

We retrospectively studied 32 eyes of 29 patients with keratoconus who underwent femtosecond-assisted Ferrara ICR implantation between December 2012 and May 2014 at the University Hospital of Besançon. From one month to 1 year postoperatively, we observed a significant improvement in BCVA and a significant decrease in cylinder and keratometry values (P<0.05). In total, 90.6% of patients had an increase in visual acuity (VA) of at least one line within 1 year while 9.4% had a decrease or stability of their VA. The average cylinder value decreased from -4.81±2.45 diopters (D) preoperatively to -2.39±1.94 D (P<0.001) at 1 year postoperatively, and the average of the maximum keratometry from 51.14±3.89 D to 48.52±4.00 D (P<0.05). Four predictive factors of success were statistically significant: type of ectasia (type 1 or 2), stage of keratoconus (Krumeich 1 or 2), implantation of only 1 ICR and a preoperative VA less than 0.4 (decimal scale). Eighty-six percent of patients with an initial VA<0.4 (decimal scale) gained 2 lines of BCVA within 1 year and 80% 3 lines versus 52% and 41%, respectively for patients with initial VA≥0.4 (decimal scale).

CONCLUSION

Femtosecond-assisted Ferrara ICR implantation for treatment of keratoconus is a reliable and reversible technique. Implantation results in greater efficiency for patients with moderately advanced asymmetric keratoconus with an initial VA<0.4 (decimal scale).