Visual outcomes and corneal asphericity effects of Kerarings implantation for keratoconus treatment.

Abstract

 

Purpose

 

To evaluate changes induced by Kerarings implantation in corneal asphericity, keratometry and visual outcomes.

 

Methods

 

This study is a retrospective clinical trial, including 40 eyes of 31 keratoconus patients operated with Keraring between November 2009 and December 2012. Uncorrected visual activity (UCVA) and best spectacle-corrected visual acuity (BSCVA) assessment, keratometry and asphericity (Q factor at 20 degrees) measurement using Pentacam HR® was performed before and six months after Kerarings implantation by one experimented surgeon and according to the manufacturer nomogram. All clinical examinations were performed in a standardized manner by an independent examiner. The analyse of the visual acuity (more or less than a line) enables to differentiate two groups of “good” and “bad” responders. Biostat TGV, a freeware was used for statistical analysis. The Wilcoxon signed rank test was applied to assess the significance of difference between pre- and post-operative data and the Wilcoxon-Mann Whitney test to assess the group comparisons. The Spearman test was used to assess the correlation between different clinical variables. The significance level was defined as p≤0.05.

 

Results

 

Table 1 shows preoperative and postoperative results. We found a gain of 3.6 lines for UCVA (0.21 preoperatively to 0.46 postoperatively), 1.1 lines for BSCVA (0.59 to 0.73) and a decrease in Kmean of 1.4 D (p≤0.001). The Q factor is significantly improved, from -0.63 to -0.33 (p=0.002). Six months after Ferrara rings implantation, UCVA has gained more than one line in 70% of eyes, less than one line in 2,5% of eyes, was stable in 25% of eyes and decreased in 2.5%. On BSCVA, 47.5% of eyes gained more than one line, 22.5% gained less than one line 17.5% were stable and only 12.5% decreased their vision. We found no significant difference between preoperative parameters of “good” and “bad” responders groups. Before surgery, BSCVA is correlated to the Q factor (p=0.02) and after surgery, both UCVA and Kmax are correlated to the Q factor (respectively p=0.02 and p=0.00). But the Kmax variation and the UCVA or BSCVA gains are not correlated.

 

Conclusions

 

Kerarings have good visual outcomes and improve mean keratometry and asphericity. But there are no predictive factors of the magnitude of the visual gain and no correlation between this gain and the asphericity variation.

 

 

Keywords: 574 keratoconus • 681 refractive surgery: corneal topography • 550 imaging/image analysis: clinical