Table 1.
The New ABCD system for classification of keratoconus
| ABCD Criteria | A ARC (3 mm Zone) |
B PRC (3 mm Zone) |
C Thinnest Pach µm |
D BDVA |
Scarring |
|---|---|---|---|---|---|
| Stage 0 | >7.25 mm (<46.5 D) | >5.90 mm (<57.25 D) | >490 µm | =20/20 (=1.0) | - |
| Stage I | >7.05 mm (<48.0 D) | >5.70 mm (<59.25 D) | >450 µm | <20/20 (<1.0) | -, +, ++ |
| Stage II | >6.35 mm (<53.0 D) | >5.15 mm (<65.5 D) | >400 µm | <20/40 (<0.5) | -, +, ++ |
| Stage III | >6.15 mm (<55.0 D) | >4.95 mm (<68.5 D) | >300 µm | <20/100 (<0.2) | -, +, ++ |
| Stage IV | <6.15 mm (>55.0 D) | <4.95 mm (>68.5 D) | = 300 µm | <20/400 (<0.05) | -, +, ++ |