Long Term Outcomes For Intrastromal Corneal Ring Segments Implantation For Keratoconus Management: Eight-Year Results

The main purpose of this study is to evaluate the efficacy, safety and stability of ICRS implantation at 8-year long term follow-up.

Keratoconus is an asymmetric and progressive corneal ectasia. Due to the high irregular astigmatism, myopia and higher order aberrations it carries a significant impact in visual acuity. Intrastromal corneal ring segments (ICRS) implantation is a safe and relatively simple procedure with good visual outcomes. However the impact in the natural progression of the disease and long term effects are not fully validated, with some contradictory published results.

A retrospective, cohort study was designed. Our sample included 124 eyes submitted to ICRS implantation surgery using manual technique in Hospital de Braga. Visual data (corrected distance visual acuity, CDVA, and uncorrected distance visual acuity, UDVA – logMAR), refractive parameters (sphere, cylinder and spherical equivalent) and topographic data (keratometry, asphericity, coma and pachymetry) were collected. A pre-operative assessment was completed. Postoperatively patients were evaluated at 6 and 12 months and at 5 and 8 years. 

Eighty patients completed the follow-up. Mean age was 29±12y. Around 75% had a stage 1 and 2 Amsler-Krumeich corneal ectasia. At 8y UDVA was 0.35±0.32logMAR, higher than the preoperative value, 0.90±0.40(p<0.01). Around 57% achieved UDVA ≥20/40 versus 10% preop(p<0.01).  The 8y CDVA was 0.18±0.18logMAR, and preoperatively was 0.41±0.30(p<0.01). More than 73% of patients achieved a CDVA of 20/30, higher than the 35% preop(p<0.01). Safety index at the end of follow-up was 2.15 and efficacy index was 1.31. Topography showed a significant decrease in K1, K2 and Kmáx. Asphericity and coma also improved significantly. Nine eyes needed ICRS explantation, 2 had spontaneous ICRS extrusion and there was 1 case of intraoperative tunnel perforation. 

ICRS implantation significantly improve visual, refractive and topographic parameters. This improvement remained stable throughout the 8-year follow-up. This study confirms that ICRS implantation technique is a safe, reversible and minimally invasive surgery with long-term stable outcomes.