Refractive Versus Tomographic Nomogram Strategies For Intracorneal Ring Implantation In Enantiomorphic Keratoconus
Published 2026 - 44th Congress of the ESCRS
Reference: PP14.08 | Type: Free paper | DOI: 10.82333/v0pe-zk27
Authors: Dr Pablo Rodrigues* 1 , Dr Bernardo Moscovici 1 , Dr Renato Ambrosio Jr 2 , Dr Mauro Campos 1 , Dr Walton Nose 1
1Unifesp,Sao Paulo,Brazil, 2Rio de Janeiro Corneal Tomography and Biomechanics Study Group,Rio de Janeiro,Brazil
Purpose
To compare the visual, refractive, keratometric, and aberrometric outcomes of intrastromal corneal ring segment (ICRS) implantation using refractive- versus tomography-based nomograms in the contralateral eyes of keratoconus patients.
Setting
Surgical Optics Sector, Department of Ophthalmology and Visual Sciences, Federal University of São Paulo (UNIFESP), São Paulo, Brazil.
Methods
Thirty patients (60 eyes) with bilateral enantiomorphic keratoconus underwent femtosecond-laser-assisted ICRS implantation in a randomized, intraindividual contralateral-eye design. In each patient, one eye was planned with a refractive-based nomogram guided by manifest refraction and the flat topographic axis. In contrast, the fellow eye was treated using a tomography-based phenotypic nomogram. Examinations included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction, keratometry, higher-order aberrations (HOAs), topometric indices, corneal volume, and patient satisfaction at baseline and 6 months; outcomes were compared using paired analyses.
Results
Baseline values were similar between the groups (all p > 0.05). At 6 months, both nomograms showed significant improvements in UDVA, CDVA, spherical equivalent, and refractive cylinder (all p < 0.05). Tomography-based planning achieved a greater reduction in maximum keratometry (−3.2 ± 1.8 D vs −2.1 ± 1.7 D; p = 0.03) and vertical coma (−0.85 ± 0.43 µm vs −0.54 ± 0.37 µm; p = 0.04). No differences were found in the efficacy and safety indices, spherical equivalent correction, or satisfaction. The ratio of implant to corneal volume was similar (p = 0.39), suggesting that differences were due to design and axis rather than volume. No sight-threatening complications were noted.
Conclusions
Both strategies were effective and safe, with significant functional improvement in both groups. Tomography-based planning achieved greater keratometric flattening and coma reduction than refractive-based planning, while maintaining equivalent safety. Tomography-guided nomograms provide a comprehensive, broadly applicable framework for ICRS implantation