Keratoconus Staging
Ophthalmology
Amsler-Krumeich stages I to IV, and a plain view of how often the criteria disagree.
How it is calculated
- Stage I: eccentric steepening, induced myopia or astigmatism of 5.00 D or less, mean central keratometry of 48.00 D or less, Vogt's striae, no scarring.
- Stage II: induced error above 5.00 D up to 8.00 D, mean K of 53.00 D or less, thinnest pachymetry 400 µm or more, no central scarring.
- Stage III: induced error above 8.00 D up to 10.00 D, mean K above 53.00 D, thinnest pachymetry between 200 and 400 µm, no central scarring.
- Stage IV: refraction not measurable, mean K above 55.00 D, thinnest pachymetry 200 µm or less, central corneal scarring.
- Staging takes the worst criterion met. The criteria frequently disagree with one another — a well-documented weakness, and part of why the Belin ABCD classification was proposed — so each criterion's own stage is shown alongside the answer.
References
- Amsler M. Le kératocône fruste au Javal. Ophthalmologica 1938; and Krumeich JH, Daniel J, Knülle A. Live-epikeratophakia for keratoconus. J Cataract Refract Surg 1998;24:456-463.
- Belin MW, Duncan JK. Keratoconus: the ABCD grading system. Klin Monbl Augenheilkd 2016;233:701-707 — the modern alternative, for context.
About these tools
OcuLearning Clinical Tools is part of an educational platform. These calculators are provided for learning and reference, and are not medical advice, a diagnosis, or a treatment recommendation.