Table 4.
The Galilei Clinical “Cheat Sheet”: Suggested Cut-off Values for Keratoconus Indices in Screening Clinical Keratoconus and Pre-Keratoconus
| Parameter | Clinical Keratoconus | Pre-Keratoconus |
|---|---|---|
| Cut-Off Value | Cut-Off Value | |
| CSI | 0.70 | - |
| DSI | 3.26 | - |
| IAI | 0.58 | 0.450* |
| I-S | 2.33 | - |
| KPI | 18.55 | - |
| Kprob | 25.55 | - |
| OSI | 2.04 | - |
| SAI | 1.25 | - |
| SDP | 1.93 | 1.065* |
| SRI | 1.52 | 0.735* |
| TCP-Central | 45.55 | - |
| TCP-Steep | 46.29 | - |
This table is to serve as a quick screening tool. Formal guidelines are not available at this time and further validation studies are required. Nevertheless, if multiple parameters are calculated to be beyond the recommended threshold values, then it should increase the index of suspicion and trigger further testing for the patient.
Abbreviations: CSI: Center/Surround Index; DSI: Differential Sector Index; I-S: Inferior-Superior Index; IAI: Irregular Astigmatism Index; KPI: Keratoconus Probability Index; Kprob: Keratoconus Probability; OSI: Opposite Sector Index; TCP: Total Corneal Power; SAI: Surface Asymmetry Index; SDP: Standard Deviation of Corneal Power; SRI: Surface Regularity Index. *These are the only indices that demonstrated diagnostic accuracy appropriate for pre-keratoconus (area under the curve >0.800); they do not represent averages as further validation studies are required, however, the authors elected to have them displayed in this table for the convenience of the clinician.