Keratoconus: Classification scheme based on videokeratography and clinical signs

Abstract

PURPOSE To determine in a longitudinal study whether there is correlation between videokeratography and clinical signs of keratoconus that might be useful to practicing clinicians. SETTING Cornea-Genetic Eye Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA. METHODS Eyes grouped as keratoconus, early keratoconus, keratoconus suspect, or normal based on clinical signs and videokeratography were examined at baseline and followed for 1 to 8 years. Differences in quantitative videokeratography indices and the progression rate were evaluated. The quantitative indices were central keratometry (K), the inferior–superior (I–S) value, and the keratoconus percentage index (KISA). Discriminant analysis was used to estimate the classification rate using the indices. RESULTS There were significant differences at baseline between the normal, keratoconus-suspect, and early keratoconus groups in all indices; the respective means were central K: 44.17 D, 45.13 D, and 45.97 D; I–S: 0.57, 1.20, and 4.44; log(KISA): 2.49, 2.94, and 5.71 (all P<.001 after adjusting for covariates). Over a median follow-up of 4.1 years, approximately 28% in the keratoconus-suspect group progressed to early keratoconus or keratoconus and 75% in the early keratoconus group progressed to keratoconus. Using all 3 indices and age, 86.9% in the normal group, 75.3% in the early keratoconus group, and 44.6% in the keratoconus-suspect group could be classified, yielding a total classification rate of 68.9%. CONCLUSIONS Cross-sectional and longitudinal data showed significant differences between groups in the 3 indices. Use of this classification scheme might form a basis for detecting subclinical keratoconus.

A combination of topographic and pachymetric parameters in keratoconus diagnosis

“…A KISA% index value of 100% was reported to be highly sensitive and specific for diagnosing keratoconus, and a value between 60 and 100 was suggested to indicate keratoconus suspect [8]. Furthermore, it was suggested that the use of topography-based quantitative variables significantly improved the repeatability, reliability and reproducibility of the diagnostic indices as in above-mentioned studies [17].…”

“…Corneal topography is an essential tool for diagnosing corneal ectatic disorders [15][16][17]. With an increase in refractive surgeries, accurate interpretation of corneal topographic outcomes has become critical.…”

Evaluation of Visual Acuity, Pachymetry and Anterior-Surface Irregularity in Keratoconus and Crosslinking Intervention Follow-up in 737 Cases

“…There have been several reports in the peer-review literature lately, regarding the keratectasia and keratoconus assessment 17 and progression monitoring, 18,19 as well as postoperative follow-up due to various CXL interventions. 20 The current options of the clinical investigator include quantitative evaluation of corneal morphologic parameters 21 derived from topography 22,23 or Scheimpflug topometry.…”

Assessing Progression of Keratoconus and Cross-linking Efficacy: The Belin ABCD Progression Display

“…10 Several classification systems for keratoconus have been proposed. [11][12][13][14][15][16][17][18][19] The Amsler-Krumeich (AK) system is amongst the oldest and still widely used. In the AK system, the severity of keratoconus is graded from stages I-IV using spectacle refraction, central keratometry, presence or absence of scarring, and central corneal thickness.…”