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Published byCarissa Crooker Modified over 3 years ago

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Topography in keratoconus Abolfazl Kashfi MD Isfarhan medical university

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Pattern recognition

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inferior steepening asymmetric or broken bowtie

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Pattern recognition Advantages easy and quick Disadvantages subjective qualitative severely affected by scale

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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

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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

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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

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Corneal Surface Asphericity index (CAI) Q value About – 0.26 normal Less (more negative) than -0.26 keratoconus suspect

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Corneal Surface Asymmetry index (SAI) (Sum of difference between symmetric points ) Normal less than 0.5 D

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Surface Regularity Index (SRI) compares differences between neighbor points within central 4.5 mm 0 < normal < 1 >1 keratoconus suspect non specific

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Differential Sector Index (DSI) Divides the cornea to 8 equal sectors (each sector 45 degrees) Reports the greatest difference in average power between any 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 power in opposite sectors -0.55 < Normal < 2.09

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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

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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 %

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Skewed Radial Axes (SRAX) >20 degree abnormal

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KISA% index (keratometry, I-S, skew percentage, astigmatism) Normal < 60 % 60% < keratoconus suspect < 100 % keratoconus >100%

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Keratoconus Severity Index (KSI) Normal < 15% 15% < suspect < 30% Keratoconus > 30 % Highest rate of steepening (HRS) Abnormal > 1.5 D per 1 mm

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Thanks for your attention

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