Clinical outcome of intrastromal corneal ring segment implantation with two different nomograms in keratoconus patients

Abstract

Aim The aim of this study was to assess the clinical effects of Keraring implantation in patients with keratoconus (KC) using a newly created nomogram (NN) based on cone location and Q value compared with the manufacturer’s standard nomogram (SN). Patients and methods This is a prospective randomized controlled clinical trial that included 100 keratoconic eyes of 100 patients. The patients were randomly assigned into two groups: group NN and group SN. Group NN underwent Keraring implantation based on the newly developed nomogram, while group SN followed the manufacturer’s standard nomogram. The primary outcome measures included visual acuity, different refractive measurements, keratometry values, and Q values, while the secondary outcome measure was Belin ABCD KC grading. All outcome measures were evaluated at 12 months postoperatively. Results The mean age of group NN was 22.96±7.45 years and that of group SN was 24.12±7.00 years, with no statistically significant difference (P=0.46). At 3 months postoperatively, group NN demonstrated substantial improvements compared with group SN. Group NN exhibited a greater improvement in uncorrected distance visual acuity [mean difference (MD) in LogMAR visual acuity=−0.61 compared with −0.31 in group SN, P<0.0001] and corrected distance visual acuity (MD: −0.34 LogMAR compared with −0.05 LogMAR in group SN, P<0.0001). Significant reductions were noted in sphere (MD: 4.22 D in group NN compared with 2.33 D in group SN, P<0.0001), refractive cylinder (MD: 2.87 D in group NN compared with 1.74 D in group SN, P=0.003), and spherical equivalent (MD: 5.56 D in group NN compared with 3.12 D in group SN, P<0.0001). Keratometric values and Belin ABCD grading system (particularly A and D categories) also showed more pronounced improvements in group NN than in group SN (P<0.0001). Conclusion The personalized approach of the new nomogram (NN) based on cone location and Q value resulted in superior visual, refractive, and corneal topographic outcomes compared with the standard nomogram (SN) during the implantation of Keraring in KC patients. The individualized nomogram allowed for more precise corneal reshaping and restoration of corneal asphericity.

Keywords

• intrastromal corneal ring segments
• keraring
• keratoconus
• nomograms
• q value