Table 1.
Accepted Abnormality Thresholds of Keratoconus Indices for the Galilei System Based on Literature Review
| Parameter | Description | Abnormal Threshold |
|---|---|---|
| AAI | Asymmetry of asphericity over the corneal surface correlates to rate of curvature change | > 25 |
| CSI | Difference between the area-corrected corneal power between two rings on the corneal surface | > 1.00 |
| DSI | Greatest difference between any two 45-degree corneal sectors | > 3.50 |
| IAI | Average of corneal power variations along each meridian of the corneal surface | > 0.50 |
| I-S | Dioptric asymmetry between the inferior and superior corneal hemispheres | > 1.4 |
| KPI | Compilation index that describes the percent probability of keratoconus | > 30 |
| OSI | Greatest difference between any two oppositely positioned 45-degree corneal sectors | > 2.10 |
| PPK | Probability index that describes the optimal threshold for detecting keratoconus | > 45 |
| SDP | Standard deviation of total corneal power | > 2.00 |
| SAI | Average of differences in corneal power between opposite points on the corneal surface | > 0.50 |
| SRI | Sum of power variations along ten central rings over corneal surface, characterizes local fluctuations | > 1.55 |
Abbreviations: AAI: Asphericity Asymmetry Index; CSI: Center/Surround Index; DSI: Differential Sector Index; I-S: Inferior-Superior Index; IAI: Irregular Astigmatism Index; KPI: Keratoconus Probability Index; SDP: Standard Deviation of Corneal Power; OSI: Opposite Sector Index; PPK: Percentage Probability of Keratoconus; SAI: Surface Asymmetry Index; SRI: Surface Regularity Index.