Investigators Propose Keratoconus Screening Algorithm

Corneal topography is a non-invasive medical imaging technique for mapping the surface curvature of the cornea
The study suggests relying on topography measurements to identify patients at risk.

This article is part of Ophthalmology Advisor’s conference coverage from the 2021 meeting of American Society of Cataract and Refractive Surgery (ASCRS), held in Las Vegas from July 23 to 27, 2021. The team at Ophthalmology Advisor will be reporting on a variety of research presented by the cataract and refractive surgery experts at ASCRS. Check back for more from the ASCRS 2021 Meeting.


To best identify patients at risk, clinicians should follow a specific criteria that takes into account baseline refraction and topography measurements, according to a research team who outlined their  findings at the American Society of Cataract and Refractive Surgery (ASCRS) 2021 meeting in Las Vegas. 

Patients who present with at least 2 D of refractive astigmatism, or who have 1 D to 2 D of against the rule (ATR, 60 ˚ to 120 ˚), refractive astigmatism should be referred for further evaluation and corneal topography, the study shows. 

The recommendations follow a retrospective analysis of the baseline manifest refraction of 1020 eyes with keratoconus that have not undergone previous corneal surgery. Based on Pentacam® (Oculus) metrics (maximum, steep, flat, and mean keratometry), the team divided patients into 3 groups based on the axis of astigmatism: with the rule (WTR, 0 ˚ to 30 ˚, 150 ˚ to 180 ˚), ATR (60 ˚ to 120 ˚), and oblique astigmatism (120 ˚ to 150 ˚, 30 ˚ to 60 ˚). 

The study shows the average manifest refraction of all eyes was sphere of -2.2D, and cylinder of 3.2D. Patients younger than 20 years were commonly found to have ATR (37%) and oblique (32%) astigmatism, respectively. 

Topography metrics show Kmax, Ksteep, Kflat, Kmean, and Kastig were 58.0±0.6 D, 50.6±0.4 D, 46.8±0.4 D, 48.0±0.4 D, and 3.8±0.2 D, respectively. In eyes with Kmax <50D, Kastig was 2.0±0.2D, and average Ksteep <45D, the report explains.

Researchers advocate for additional consideration for patients with at least 2 D of corneal astigmatism in the hopes that this would empower general eyecare practices to offer a low-cost screening approach.

Disclosure: Multiple study authors declared affiliations with the biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.  

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Greenstein S, Wawrzusin P, Hersh P, Gelles J, Ando A, Garvey N. Refraction and keratometryin keratoconus: a proposed screening algorithm. Poster presented at: 2021 ASCRS Annual Meeting; July 2021; Las Vegas, NV. Abstract 76244.