International Journal of Keratoconus and Ectatic Corneal Diseases

Register      Login

VOLUME 6 , ISSUE 2 ( July-December, 2017 ) > List of Articles


Distinction between Early Keratoconus with Normal Vision and Normal Cornea based on Pattern Recognition Analysis

Alfredo Vega-Estrada, Jorge L Alio, Pablo Sanz, María J Prieto, Antonio Cardona, Miguel Maldonado, Ramon Gutierrez, Rafael I Barraquer, Luis M Sádaba

Citation Information : Vega-Estrada A, Alio JL, Sanz P, Prieto MJ, Cardona A, Maldonado M, Gutierrez R, Barraquer RI, Sádaba LM. Distinction between Early Keratoconus with Normal Vision and Normal Cornea based on Pattern Recognition Analysis. Int J Kerat Ect Cor Dis 2017; 6 (2):58-66.

DOI: 10.5005/jp-journals-10025-1144

License: CC BY 3.0

Published Online: 01-09-2017

Copyright Statement:  Copyright © 2017; The Author(s).



To find the profile that differentiates most normal corneas from early keratoconus with normal vision.

Materials and methods

Multicentric, comparative study including a total of 995 eyes and divided into two groups: 625 eyes suffering from early keratoconus but with normal vision [spectacle corrected distance visual acuity (CDVA) of 0.9 decimal or better] and 370 normal control eyes with same normal vision level. To ascertain the main differences that would allow the identification of the keratoconic eyes from normals, a pattern recognition analysis was performed combining two statistical methods: Principal component analysis (PCA) and discriminant analysis. Visual and refractive parameters, corneal topography, aberrometry, and PCA were evaluated in both groups.


The application of the PCA with Varimax rotation offered a total of five factors which explains the 85.51% of the total variability. Discriminant analysis indicated that factors 1 and 3 were at the greatest discriminating capacity. From a total of 318 cases, the newly identified abnormal pattern profile allowed the recognition of 275, which presents a sensitivity and specificity of 71.6 and 97.3% respectively.


In eyes with normal CDVA, those factors related to the nonorthogonal shape irregularity of the cornea and the refractive power are the ones that showed more discriminating capabilities between normal and early keratoconic eyes.

Clinical significance

Principal component analysis allows to correctly discriminate between normal and mild keratoconus patients; additionally, this method is not restricted to a particular corneal topography technology and is available to any normally equipped ophthalmology office.

How to cite this article

Alio JL, Vega-Estrada A, Sanz P, Prieto MJ, Cardona A, Maldonado M, Gutierrez R, Barraquer RI, Sádaba LM. Distinction between Early Keratoconus with Normal Vision and Normal Cornea Based on Pattern Recognition Analysis. Int J Kerat Ect Cor Dis 2017;6(2):58-66.

  1. Keratoconus. Surv Ophthalmol 1998 Jan-Feb;42(4):297-319.
  2. Le keratocone frusta au javal. Ophtalmologica 1938;96:77-83.
  3. Keratocone classique et keratocone fruste, arguments unitaires. Ophtalmologica 1946;111(2-3):96-101.
  4. Risk factors and prognosis for corneal ectasia after LASIK. Ophthalmology 2003 Feb;110(2):267-275.
  5. Validation of metrics for the detection of subclinical keratoconus in a new patient collective. J Cataract Refract Surg. 2014 Feb;40(2):259-268.
  6. Comparison of multimetric D index with keratometric, pachymetric, and posterior elevation parameters in diagnosing subclinical keratoconus in fellow eyes of asymmetric keratoconus patients. J Cataract Refract Surg 2015 Mar;41(3):557-565.
  7. Keratoconus-integrated characterization considering anterior corneal aberrations, internal astigmatism, and corneal biomechanics. J Cataract Refract Surg 2011 Mar;37(3):552-568.
  8. Outcome analysis of intracorneal ring segments for the treatment of keratoconus based on visual, refractive, and aberrometric impairment. Am J Ophthalmol 2013 Mar;155(3):575.e1-584.e1.
  9. Accuracy and precision of EyeSys and Orbscan systems on calibrated spherical test surfaces. Eye Contact Lens 2004 Apr;30(2):74-78.
  10. Corneal biomechanical properties in normal, post-laser in situ keratomileusis, and keratoconic eyes. J Cataract Refract Surg 2007 Aug;33(8):1371-1375.
  11. Keratoconus management guidelines. Int J Kerat Ect Cor Dis 2015 Jan-Apr;4(1):1-39.
  12. Detection of keratoconus in clinically and algorithmically topographically normal fellow eyes using epithelial thickness analysis. J Refract Surg 2015 Nov;31(11):736-744.
  13. Assessment of the impact of keratoconus on vision-related quality of life. Invest Ophthalmol Vis Sci 2013 Apr;54(4):2902-2910.
  14. Template-based correction of high-order aberration in keratoconus. Optom Vis Sci 2013 Apr;90(4):324-334.
  15. Genetic association of COL5A1 variants in keratoconus patients suggests a complex connection between corneal thinning and keratoconus. Invest Ophthalmol Vis Sci 2013 Apr;54(4):2696-2704.
  16. Comparative evaluation of refractive surgery candidates with Placido topography, Orbscan II, Pentacam and wavefront analysis. J Cataract Refract Surg 2008 Apr;34(4):623-631.
  17. Influence of the reference surface shape for discriminating between normal corneas, subclinical keratoconus and keratoconus. J Refract Surg 2013 Apr;29(4):274-281.
  18. A new pachymetry based approach for diagnostic cutoffs for normal, suspect and keratoconic cornea. Eye (Lond) 2012 May;26(5):650-657.
  19. Geometrical custom modeling of human cornea in vivo and its use for the diagnosis of corneal ectasia. PLoS One 2014 Oct;9(10):e110249.
  20. Corneal higher order aberrations: a method to grade keratoconus. J Refract Surg 2006 Jun;22(6):539-545.
PDF Share
PDF Share

© Jaypee Brothers Medical Publishers (P) LTD.