Table 1.
Amsler-Krumeich clinical classification of keratoconus by stage.
| Stage | Characteristics |
|---|---|
| I | Eccentric steepening |
| Induced myopia and/or astigmatism of ≤5.00 D | |
| Keratometric reading ≤48.00 | |
| Vogt's lines, typical topography | |
|
| |
| II | Induced myopia and/or astigmatism 5.00 to ≤8.00 D |
| Keratometric reading ≤53.00 | |
| Pachymetry ≥ 400 μm | |
|
| |
| III | Induced myopia and/or astigmatism 8.00 to ≤10.00 D |
| Keratometric reading >53.00 | |
| Pachymetry 200 to 400 μm | |
|
| |
| IV | Refraction not measurable |
| Keratometric reading >55.00 D | |
| Central scars | |
| Pachymetry ≤ 200 μm | |
The patient is at the specific stage if one of the characteristics applies. Pachymetry is measured at the thinnest site of the cornea.
D, diopters.