Official ESCRS | European Society of Cataract & Refractive Surgeons


Novel tomographic determinants of keratoconus progression: keratoconus area

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Session Details

Session Title: Keratoconus

Session Date/Time: Monday 16/09/2019 | 14:00-16:00

Paper Time: 14:36

Venue: Free Paper Forum: Podium 2

First Author: : A.Cunha PORTUGAL

Co Author(s): :    P. Correia   L. Torrão   R. Moreira   F. Falcão-Reis   J. Pinheiro-Costa                 

Abstract Details


Keratoconus is a chronic non-inflammatory corneal ectasia. The majority of studies related to keratoconus progression focuses on central cornea changes, which is the steepest point in corneal curvature. Nevertheless, it is possible to document variations in the curvature of the cornea beyond its steepest point. We define keratoconus area enlargement as an increase of more than 1D in the anterior curvature in non-apical corneal areas. Our purpose is to evaluate keratoconus area enlargement as a new parameter for ectasia progression, and to compare it to the most recent and reliable parameters used on keratoconus progression.


Department of Ophthalmology, Centro Hospitalar de São João Hospital, Porto, Portugal


We have designed a cohort study with 100 patients with keratoconus, 113 eyes were included in the analisys. Scheimpflug scans of patients with more than 1 year of follow-up, with two scans separated by 12±3 months, were evaluated for progression. Keratoconus area enlargement were confirmed by two independent observers. Variables used for detection of keratoconus progression were Kmax, Kmean, K2, PachyMin, D-Index, Corneal Astigmatism and PRC of 3.0 mm centered on the thinnest point. Correlation analysis and Receiver operating characteristic curve (ROC) analysis was performed.


Considering Keratoconus area enlargement and keratoconus progression as change in at least 2 tomographic variables, progression was present in 55.8% and 50.4%, respectively.The variations of keratometric readings (ΔKmax, ΔKmd, ΔK1, ΔK2), D-index and ELEBmax showed positive associations with area progression (p=0,001, p<0,001, p<0,001, p<0,001, p=0.005 and p=0.008), respectively. Evaluating the performance of Kmax, D-index and keratoconus area enlargement in a ROC curve, as isolated parameters, they had a sensitivity of 49%, 82% and 77% and a specificity of 100%, 95% and 66% to detect keratoconus progression (auc=0.746, p<0,001; auc=0.885, p<0,001; auc=0.716; p<0,001), respectively.


Considering progression as changes in two or more variables, the sensitivity of Kmax in the detection of keratoconus progression was lower than of keratoconus area enlargement. This difference can be explained by the changes in keratoconus outside the small area represented by Kmax. As such, area enlargement has a comparable sensitivity with parameters currently used and can be an early marker of disease progression. Consequently, we suggest the inclusion of keratoconus area enlargement in the evaluation of keratoconus progression in conjunction with other variables to increase the reliability of our clinical evaluation.

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