Novel Q-value-based nomogram for single intracorneal ring se
A Study was conducted to compare the efficacy of implanting a single Keraring segment according to a novel Q-value-based nomogram (QN) to that of segment implantation according to the manufacturer's standard nomogram (SN), for keratoconus treatment.

This was a prospective, randomized controlled trial of 104 patients with Amsler-Krumeich grade 1 or 2 keratoconus, and type 1 or 2 cone asymmetry determined according to manufacturer's classification. They were randomly distributed into two groups:
-group A patients (n = 52) underwent Keraring implantation according to the SN, and
-group B patients (n = 52) underwent implantation of a single (210° arc-length) Keraring segment according to the QN.

Both treatments were combined with accelerated transepithelial cross-linking, and follow-up was 6 months. Main outcome measures were preoperative and postoperative visual acuity, subjective refraction and corneal topography.

--At postoperative month 6, group B exhibited statistically significantly higher values of mean uncorrected distance visual acuity (UDVA), sphere, K2, K-average, K-max and Q-anterior compared to that of group A.

--However, group A exhibited better refractive cylindrical improvements. In group A, spontaneous extrusion of one Keraring segment was documented.

Conclusively, Single 210° arc-length segment implantation using this objective of QN was more efficacious for keratoconus treatment than using the subjective SN. The nomograms were comparable when the Q-anterior value was more than -1.00; however, the QN was superior to the SN when the Q-anterior value was less than -1.00. The QN yielded greater postoperative UDVA and smoother corneal remodelling than did the SN for treatment of grade 1 and 2 keratoconic eyes.