Biomechanical parameters, mean keratometry may predict short-term outcomes of ICRS implantation

Prediction of short-term postoperative visual outcomes after intracorneal ring segment implantation in keratoconic eyes was enabled by biomechanical parameters and mean keratometry, according to a study.

The potential for long-term predictions were limited by biomechanical changes in the cornea, the study authors said.

The retrospective study analyzed 45 consecutive eyes of 35 patients with keratoconus who were implanted with Keraring (Mediphacos) intrastromal corneal ring segments. Corneal topography, visual acuity, refraction and aberrations were analyzed during 6 months of follow-up. Corneal biomechanical changes were analyzed with the Ocular Response Analyzer (Reichert).

“KeraRing segments are safe and useful for corneal modeling in keratoconus, but their effect is not maintained in a medium to long term in all cases. … In the long term, corneal biomechanical changes can still occur, and these changes seem to be responsible for the limitation of the ring segment effect in some cases,” the study authors said.

Significant changes in corneal resistance factor and corneal hysteresis were observed at 3 months (P = .03) and at 6 months (P = .02) postoperatively. Multiple regression analysis indicated that corrected visual acuity at 1 month postop correlated significantly with preop mean keratometry and preop differences between corneal hysteresis and corneal resistance factor (P < .01).

At all time points, preoperative corneal biomechanical parameters were significantly correlated with postoperative corneal higher-order aberrations (P ≤ .05); the correlation grew stronger at the end of follow-up.

There were no significant correlations at 6 months between postop visual outcomes and preoperative parameters.

The authors noted that future studies should address the possibility that corneal collagen cross-linking may help stabilize the ring segment effect at 1 month after intracorneal ring segment implantation.

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Source:

Cornea. 2012;31(5):491-499.