Scheimpflug imaging accurately diagnoses keratoconus (KC) in pediatric eyes, with the corneal assessment index from the relational thickness and other OCULUS values analyzed for 8 mm zone (CAIRO 8) index providing the greatest accuracy, according to a study published in Eye.

Researchers conducted a retrospective observational study of 480 eyes of 480 children consisting of patients with KC (n=48) and a non-keratoconic control group (n=432). Among patients with KC, 8 had formed fruste keratoconus (FFKC) while the remaining 40 had frank KC. Investigators excluded children with poor quality images, previous ocular trauma, surgeries, or corneal pathology other than ectasia from the analysis.

Researchers reviewed data from Scheimpflug topography images for all participants and investigated a total of 36 indices. They used the area under the receiving operating characteristic (AUROC) curve to determine the diagnostic accuracy of each index. The team determined that all 4 indices did not show discriminative power in differentiating KC and FFKC from normal corneas. The remaining 32 indices showed variable degrees of diagnostic accuracy. 

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Researchers noted that CAIRO 8 had the highest AUROC value (0.979) and 8 indices showed non-inferiority to it. These indices included Ambrosio’s relational thickness maximum (ART max) and avg, the pachymetric progression index maximum (PPI max) and avg, the back elevation from the best-fit toric ellipsoid (BE BFTE), the KC index (KI), the topographic KC indices (TKC), and the index of height decentration (IHD) (P >.05 for all). 

“For diagnosis of pediatric KC or even FFKC, we recommend relying on some indices, namely CAIRO 8, ART max and avg, PPI max and avg, BFTE, KI, TKC, and IHD, rather than the other indices,” the investigators suggest.

Study limitations include a retroscopic nature.


Hashem AO, Aziz BF, Wahba SS, Roshdy MM, Elawamry AI. Diagnostic accuracy of different keratoconus detection indices of pentacam in paediatric eyes. Eye. Published online May 3, 2022. doi:10.1038/s41433-022-02070-x