Long-term follow up of intracorneal ring segment implantation in 932 keratoconus eyes.

PURPOSE: To evaluate the progression of keratoconus in 932 eyes of 659 patients through visual, refractive and topographic data after intracorneal ring segment (ICRS) implantation. METHODS: Retrospective review of 659 patients who underwent ICRS (Intacs®) implantation for keratoconus between September 1997 and November 2017. Demographics, preoperative and postoperative uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) in LogMAR, corneal topography parameters (thinnest pachymetry, Kmax), central corneal pachymetry and total follow-up time were evaluated. Statistical analysis was performed using IBM SPSS Statistics 24.0 for windows. RESULTS: Nine hundred and thirty-two eyes of 659 patients, with a mean age of 30.41 years (range 11-76 years), were evaluated. Mean total follow up time was 3.02 years. Forty-one eyes had a total follow up of over 10 years. Both UCVA and BCVA improved significantly after ICRS implantation (P<0.01). Only 18 eyes (2.66% of eyes of patients under 35 years of age) were found to have progression of keratoconus based on postoperative topographic data (Mean age 23.00 years, 55.6% female, total follow-up 2 to 10 years) CONCLUSION: ICRS implantation showed long-term improvement and stability in visual and topographic results in a large case series of patients with keratoconus. Only a minimal rate of progression was detected in young patients. However, further prospective studies need to be conducted to better define predictability of postoperative visual outcomes and progression.

Allogenic corneal tissue transplantation in substitution for extruded intracorneal rings: A case series.

We describe a case series of four eyes of four keratoconus patients with extruded intracorneal ring segments (ICRS) in whom donor corneal tissue was used to substitute for the extruded ICRS in an attempt to preserve its effect. In all patients, the extruded intracorneal ring was removed through the exposed area. Donor corneal tissue (tailored to the size and shape of the ICRS) was inserted into the empty ICRS tunnel and fixed in place using 10-0 nylon sutures. At three months follow-up, all patients had a healed graft and displayed a stable Kmax, best corrected visual acuity (BCVA) and corneal topography comparable to the preoperative values. Replacing extruded intracorneal rings with donor tissue grafts in keratoconus patients appears to be a promising technique in preserving the effect of the corneal ring and possibly in treating primary keratoconus with donor tissue segments. Refinement of the technique, longer follow-up, and a larger study population is warranted.

Effects of femtosecond and excimer lasers on implanted KAMRA corneal inlay in animal models.

PURPOSE: To evaluate the effect of femtosecond laser and excimer laser on an intracorneal inlay (KAMRA®) implanted in animal models. METHODS: Femtosecond laser was used to create corneal intrastromal pockets at 250µm depth in five porcine eyes. Four intact KAMRA inlays, examined by slit-lamp biomicroscopy and light microscopy, were implanted in the pocket of four eyes. A standard LASIK flap was created above each implanted inlay in the four eyes using a femtosecond laser with flap thicknesses of 150µm, 130µm, 110µm and 90µm. In the fifth porcine eye, a LASIK flap was created using femtosecond laser at 110µm depth, and a fifth inlay was then implanted in the 250µm pocket. Excimer laser ablation was performed under the flap targeting a -3.00 refraction. The inlay was then explanted, examined and reimplanted in the same pocket followed by a second similar excimer laser ablation. RESULTS: Significant burn, shrinkage and distortion of microholes were noted in all the first four inlays following the femtosecond laser flap creation at all the various flap thicknesses. The damage was noted to be more prominent as the distance between the flap and inlay decreased. No apparent effect was noted on the fifth inlay following repeated excimer laser ablations. CONCLUSION: Unlike excimer laser, femtosecond laser appears to be hazardous and damaging to the intracorneal KAMRA inlay when applied above it.