KERATOCONUS PROGRESSION AFTER INTRASTROMAL CORNEAL RING SEGMENT IMPLANTATION

To analyse how implantation of intrastromal corneal ring segment (ICRS) implantation influences progression in patients with confirmed progressive keratoconus.

Centro Hospitalar de Entre o Douro e Vouga, Santa Maria da Feira, Portugal.

Retrospective study involving eyes treated with ICRS with triangular section implanted with manual technique. Visual, refractive, topographic and aberrometric measures were assessed at least four times, two of them prior to surgery to document progression (visit 1 and 2), within 6 months of surgery (V3) and after at least 2 years from surgery (V4). Progression was documented using Pentacam ® Belin ABCD Progression Display. Outcome measures included LogMAR uncorrected (UCVA) and best spectacle corrected (BCVA) visual acuity, spherical equivalent (SE), corneal dioptric power in the flattest (K1) and steepest (K2) meridians, mean corneal dioptric power (mean K), topographic astigmatism (A), asphericity at 8 mm (Q), minimum pachymetry (MP) and root mean square coma aberration (RMS-Coma).

The study evaluated 22 eyes of 20 patients with a mean age of 25.40 years ± 6.27 (SD) at implantation date (54.5% male; 45.5% male). Average follow-up duration at the last visit (V4) was 3.13 ± 0.89 years. Measurements worsened between the 2 preoperative examinations, confirming the progressive status of the disease. All visual, refractive, topographic and aberrometric measurements had a statistically significant improvement (p < 0.05) from V2 to V3 and all measurements retained significant improvement (p < 0.05) at V4 when compared to V2. At the last visit (V4) we noticed a slight regression of mean K value from 45.12 ± 2.39 (V3) to 45.80 ± 2.05 (V4; p < 0.05) and of Q value from -0.27 ± 0.21 (V3) to -0.35 ± 0.24 (V4, p < 0.05), but still markedly improved from preoperative values of 47.95 ± 2.74 mean K and -0.77 ± 0.33 Q value (p < 0.05). There were no statistically significant differences (p > 0.05) in UCVA, BCVA, SE, A and MP values when comparing V3 to V4 and there was a slight improvement in RMS-coma value from 2.684 ± 1.140 µm to 2.461±1.094 µm (p < 0.05).

ICRS implantation significantly improved visual, refractive, topographic and aberrometric parameters in confirmed progressive keratoconus. Most of these measurements remained stable at a minimum of 2 years of follow-up with exception of a slight regression in keratometry and asphericity values and an improvement in coma aberration during the follow-up period. Uncorrected and corrected visual acuity improved after surgery and remained stable throughout the follow-up period.