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● OSI (Opposite Sector Index)
The OSI is the largest difference in the average
refractive power between two opposing sections out
of eight divisions of the cornea. The keratoconus
eye shows a larger value.
● CSI (Center/Surround Index)
The CSI is the difference between the average
refractive power in an area within a diameter of 3.0
mm and that in the ring-shaped surrounding area of
diameters from 3.0 mm to 6.0 mm in the analyzed
section.
● SDP (Standard Deviation of Corneal Power)
The SDP is calculated by distribution of refractive
powers at all points on the videokeratograph.
The SDP value often becomes large in the case
of keratoconus, corneal transplantation, external
injuries, and when the distribution range of refractive
powers is large.
● IAI (Irregular Astigmatism Index)
The IAI sums the fluctuations of the refractive
powers on each ring for each meridian on the entire
cornea and shows the average value (irregular
astigmatism index).
When the IAI value becomes large, sections with
irregular astigmatism increase on the surface of the
cornea.
The IAI is high immediately after cornea
transplantation.
● KPI (Keratoconus Prediction Index)
The KPI is calculated using a discriminate analysis
equation, and is used as an index for calculating the
KCI that nally determines the possibility of clinical
keratoconus.
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