Classification of Keratoconus eye disorder is an important task. The advantage to classify or grade any disease is  to help select the best treatment option. For example in keratoconus treatment – to determine whether the first best treatment option is intacs surgery or cxl. If you were comparing the best kertoconus treatment options available between various surgeons it would be helpful to know what your stage of disease is. A single treatment option may suffice in early disease. In advanced keratoconus disorder more than one might be required.

This also helps compare efficacy of keratoconus treatment amongst clinicians and researchers. Sometimes the classification like classification of cross linking is done to standardize reports and claims. Staging also helps in accepting newly discovered treatment modalities.

Amsler-Krumeich Grading - Classification of  Keratoconus Eye Disorder

1 Non central Bulging
Nearsightedness, induced astigmatism, or both <5.00 D
Mean central Keratometry <48 Diopter
2 Nearsightedness, induced astigmatism, or both from 5.00 to 8.00 D
Mean central Keratometry <53.00 Diopter
No corneal scarring
Corneal pachymetry>400 microns
3 Nearsightedness, induced astigmatism, or both from 8.00 to 10.00 D
Mean central Keratometry >53.00 Diopter
No scarring
Corneal Pachymetry 300 – 400 microns
4 Unable to refract to improve vision
Mean central Keratometrys >55.00 Diopter
Central corneal scarring
Corneal Pachymetry < 200 microns
Grade Descriptors for Overall Scarring
1.0 Slight but not in center of vision, total area is less than 1.5 mm
2.0 Approaching center of vision and more apparent, total area is 1.5  to 2.5mm
3.0 In center of vision, dense but translucent, total area is 2.5 mm or more
4.0 Dense opaque in center and affecting vision, total area is 2.5 mm or more
Grade Stage Corneal scarring* Slit-lamp signs* Axial Pattern Other Features
0 Corneal Topo WNL   –  – Typical Average corneal power (ACP) ≤ 47.75 D, Higher-order RMS error** ≤ 0.65
1 Abnormal Cornea Topography     –    – Atypical: 
– Irregular
-Sup. bowtie
-Inf. bowtie
-Inf. or Sup. area of steepening no more than 3.00 D steeper than ACP
ACP ≤ 48.00 D, Higher-order RMS error ≤ 1.00
2 Suspect Topography Isolated area of steepening:
-Central steep
Additional features:ACP ≤ 49.00 D  or  Higher-order RMS error > 1.00, ≤ 1.50
3 Mild Keratoconus  – Maybe Implies Keratoconus Additional features:ACP ≤ 52.00 D  or  Higher-order RMS error > 1.50, ≤ 3.50
4 Moderate Keratoconus Add features:Corneal scarring and overall CLEK grade up to 3.0 Possible Implies Keratoconus Additional features: ACP > 52.00 D, ≤ 56.00 D  or  Higher-order RMS error > 3.50, ≤ 5.75
5 Severe dKeratoconus Add features:Corneal scarring CLEK grade 3.5 or greater overall Always present Implies Keratoconus Additional features: ACP > 56.00 D  or  Higher-order RMS error > 5.75″

**higher-order first corneal surface wavefront root mean square (RMS) error

For grades 0-1, all of the parameters in a category must be met. For all grades, as long as all required parameters are present the worst feature is given the highest weight in this classification of keratoconus eye disorder.



As science is progressing and newer detection instruments and treatment modalities are being discovered there is a constant upheaval in the classification of keratoconus eye disorders.

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I want to halt Keratoconus!

I am tired of wearing glasses and contacts. My vision is affecting my work. I am worried I may loose vision. I want to preserve my precious vision!