Keratoconus after 40 years of age: a longitudinal comparative population-based study

  • Hassan Hashemi
  • Soheila Asgari
  • Shiva Mehravaran
  • Mohammad Hassan Emamian
  • Akbar FotouhiEmail author
Original Paper



To determine 5-year changes in keratoconus indices and corrected distance visual acuity in 40–64-year-old keratoconus compared with normal subjects.


In this prospective population-based cohort study, 5-year changes in Belin grading system indices including the average radii of curvature in the 3 mm zone surrounding the thinnest point in the anterior (ARC-3 mm) and posterior (PRC-3 mm) cornea, corrected distance visual acuity, minimum corneal thickness, maximum Ambrosio’s relational thickness (ART-max), and maximum anterior keratometry indices centered on steepest point in the central 3 mm (Kmax-3 mm), 4 mm (Kmax-4 mm), and 5 mm (Kmax-5 mm) zones were compared between keratoconus and normal participants. In the analysis, comparisons were made between all keratoconus eyes and the right eyes of normal participants.


The mean age in the keratoconus (n = 16 eyes) and normal (n = 1986 eyes) groups (48.31 ± 4.78, 49.37 ± 5.79 years, respectively) was not statistically different (P = 0.327). The two groups differed in terms of changes in PRC-3 mm (− 0.07 ± 0.15 vs. + 0.001 ± 0.14 mm, respectively, P = 0.042) and ART-max (− 6.28 ± 25.19 vs. + 15.8 ± 72.7 μm, respectively, P = 0.003). There were significant correlations between the reduction in PRC-3 mm and its baseline value (β = − 0.20, P < 0.001) and keratoconus (β = − 0.26, P < 0.001). The reduction in ART-max significantly correlated with its baseline value (β = − 0.43, P < 0.001) and keratoconus (β = − 111.74, P < 0.001).


According to these findings, posterior corneal steepening and thinning in keratoconus patients continue after the age of 40 years, but it is clinically negligible. The changes are independent of normal age-related changes and appear to be slower in cases with steeper and thinner corneas.


Keratoconus Ectasia display indices Posterior corneal steepening Corneal thinning Middle age 



Shahroud Eye Cohort Study was supported by the Noor Ophthalmology Research Center and Shahroud University of Medical Sciences (Project Number: 8737). No funding was received for this research.

Compliance with ethical standards

Conflict of interest

All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.Noor Ophthalmology Research CenterNoor Eye HospitalTehranIran
  2. 2.ASCEND Center for Biomedical ResearchMorgan State UniversityBaltimoreUSA
  3. 3.Ophthalmic Epidemiology Research CenterShahroud University of Medical SciencesShahroudIran
  4. 4.Department of Epidemiology and Biostatistics, School of Public HealthTehran University of Medical SciencesTehranIran

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