Prognostic Factors Of Intracorneal Rings Segment, Profile To A Successful Treatment And Probability Of Success Calculation

To identify the prognosis factors of success for intracorneal rings segment (ICRS) implantation in keratoconus, determine a “good responder” patient and calculate the probability of success of the intervention (Psuccess).

Retrospective case series. University-hospital La Timone, Marseille, France.

130 eyes had ICRS implantation with Keraring and Intacs SK. Refractive, topographic, and aberrometric variables were evaluated before and after surgery, then patients were separated in “success” and “failure” group based on postoperative refractive and aberrometric data. Univariate and multivariate analysis has been completed to find prognosis factors and to create a probability of success calculation (Psuccess).

64.6% patients presented a success and 35.4% a failure. In the success group, corrected distance visual acuity (CDVA) in logMAR was higher (0,38 ± 0,23 vs 0,28 ± 0,21, p=0,03), corneal asphericity (Q-value) was less prolate (-0.92 ± 0.43 vs -1.10 ± 0.40; p=0,009), and distance between Kmax and center of pupil (DKmax) was higher (1.65 ± 0.83 vs 1.35 ± 0.70; p=0,045). Maximal keratometry (Kmax) was lower (58.38 ± 4.83 vs 59.86 ± 4.42; p=0,068) and spherical equivalent (SE) was more negative (-3.77 ± 3.20 vs -3.05 ± 3.65; p=0,09) but not significant. With a logistic regression model, we created a calculation formula of Psuccess including keratoconus stage, CDVA, uncorrected distance visual acuity (UDVA), SE, Kmax, Q-Value and DKmax.

ICRS implantation have more chance of success in stage III keratoconus, eccentric, with myopic astigmatism, visual loss, Q-Value close to zero and low Kmax. The calculation of Psuccess helps to select patients for this surgery.