Topography in keratoconus Abolfazl Kashfi MD Isfarhan medical university.
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Transcript of Topography in keratoconus Abolfazl Kashfi MD Isfarhan medical university.
Topography in keratoconus
Abolfazl Kashfi MDIsfarhan medical university
Pattern recognition
Pattern recognition
inferior steepening asymmetric or broken bowtie
Pattern recognition
• Advantages easy and quick • Disadvantages subjective qualitative severely affected by scale
Keratometric data normal cornea
• Flatten from center to periphery 2-4D• Nasal is flatter than temporal• 41 to 47 D at center average 43.5 D• Each eye is mirror images of the fellow eye
Simulated keratometry (Sim K)
Central corneal power (D)
< 47.2 Normal 47.2 < Keratoconus suspect<48.7> 1 D difference between SimK(S) of fellow eyes >48.7 Keratoconus> 2 D difference between SimK(S) of fellow eyes
Inferior - Superior (I-S) index
• Rabinowitz- McDonnel I-S index (difference between average of five superir points and five inferior points in central 3mm of cornea each 30 degrees apart)
< 1.4 Normal 1.4< Keratoconus suspect < 1.9 > 1.9 keratoconus
maybe normal in central KC
Corneal Surface Asphericity index (CAI)
Q valueAbout – 0.26 normal
Less (more negative) than -0.26 keratoconus suspect
Corneal Surface Asymmetry index (SAI)
(Sum of difference between symmetric points )
Normal less than 0.5 D
Surface Regularity Index (SRI)
compares differences between neighbor points within central 4.5 mm
0 < normal < 1>1 keratoconus suspect
non specific
Differential Sector Index (DSI)Divides the cornea to 8 equal sectors (each sector 45 degrees)Reports the greatest difference in average power betweenany two sectors
0.21< Normal < 3.51
Opposite Sector Index (OSI)Divides the cornea to 8 equal sectors (each sector 45 degrees)Represents the greatest difference of average powerin opposite sectors
-0.55 < Normal < 2.09
Center Surrond Index (CSI)
The difference in the average area corrected corneal power between the central corneal zone 3 mm in diameter and a 3 mm annulus surrounding the central area
-0.28 < Normal < 0.80
Keratoconus Predictability Index (KPI)Maeda and Klyce has generated KPI using 8 keratometric indices and 11 quantitative criteria and a complex data analysis system called “neural network system”.
Keratoconus >23 %
Keratoconus index (KCI)the keratoconus-like pattern is determined and expressed as a percentage
0 < keratoconus suspect < 5%Keratoconus >5 %
Skewed Radial Axes (SRAX)
>20 degree abnormal
KISA% index (keratometry, I-S, skew percentage, astigmatism)
Normal < 60 %60% < keratoconus suspect < 100 %keratoconus >100%
Keratoconus Severity Index (KSI)
Normal < 15%15% < suspect < 30%Keratoconus > 30 %
Highest rate of steepening (HRS)Abnormal > 1.5 D per 1 mm
Thanks for your attention