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Keratoconus staging by decades: a baseline ABCD classification of 1000 patients in the Homburg Keratoconus Center
  1. Elias Flockerzi1,
  2. Kassandra Xanthopoulou1,
  3. Susanne Christiane Goebels1,
  4. Elena Zemova1,
  5. Sonia Razafimino1,
  6. Loïc Hamon1,
  7. Theresia Jullien1,
  8. Ulrike Klühspies1,
  9. Timo Eppig2,
  10. Achim Langenbucher2,
  11. Berthold Seitz1
  1. 1 Department of Ophthalmology, Saarland University Medical Center, Homburg, Germany
  2. 2 Department of Experimental Ophthalmology, Saarland University Medical Center, Homburg, Germany
  1. Correspondence to Elias Flockerzi, Department of Ophthalmology, Saarland University Medical Center, Homburg 66421, Germany; elias.flockerzi{at}


Background This retrospective cross-sectional study aims to analyse the keratoconus (KC) stage distribution at different ages within the Homburg Keratoconus Center (HKC).

Methods 1917 corneae (1000 patients) were allocated to decades of age, classified according to Belin’s ABCD KC grading system and the stage distribution was analysed.

Results 73 per cent (n=728) of the patients were males, 27% (n=272) were females. The highest KC prevalence occurred between 21 and 30 years (n=585 corneae, 294 patients). Regarding anterior (A) and posterior (B) curvature, the frequency of A was significantly higher than B in all age groups for stage 0, 1 and 2 (A0>B0; A1>B1; A2>B2; p<0.03, Wilcoxon matched-pairs test). There was no significant difference between the number of A3 and B3, but significantly more corneae were classified as B4 than A4 in all age groups (p<0.02). The most frequent A|B combinations were A4|B4 (n=451), A0|B0 (n=311), A2|B4 (n=242), A2|B2 (n=189) and A1|B2 (n=154). Concerning thinnest pachymetry (C), most corneae in all age groups were classified as C0>C1>C2>C3>C4 (p<0.04, Wilcoxon matched-pairs test). For the best distance visual acuity (D), a significantly higher number of corneae were classified as D1 compared to D0 (p<0.008; D1>D0>D2>D3>D4).

Conclusion The stage distributions in all age groups were similar. Early KC rather becomes manifest in the posterior than the anterior corneal curvature whereas advanced stages of posterior corneal curvature coincide with early and advanced stages of anterior corneal curvature. Thus, this study emphasises the necessity of posterior corneal surface assessment in KC as enabled by the ABCD grading system.

  • Cornea
  • Diagnostic tests/Investigation
  • Epidemiology

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  • Contributors All authors contributed to this work by providing their data, revising the manuscript, approving it for publication and agreeing to take full responsibility for all aspects of this work.

  • Funding This study received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests KX, SCG, SR, EZ, LH, TJ, UK, AL and BS declare that they do not have any financial disclosures in medicine. EF has received a travel grant to the Second and Third Ophthalmology Cystinosis Forum (Orphan Europe, Ulm, Germany) and an invitation to a seminar on presentation training organised by the Santen GmbH (Munich, Germany). TE was a member of the Institute of Experimental Ophthalmology, Saarland University Medical Center (Homburg, Germany), at the time of data collection and is now an employee of the Amiplant GmbH (Schnaittach, Germany).

  • Ethics approval The study (trial number NCT03923101, U.S. National Institutes of Health, was approved by the regulatory body, the local ethics committee of Saarland (Ethikkommission bei der Ärztekammer des Saarlandes, reference number 121/20). Written informed consent was provided by each patient with KC in the HKC for the analysis of data.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.

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