Table 1.

Studies use posterior elevation and derived parameters to discriminate subclinical keratoconus and normal eyes

Authors	Modality	Significant difference between subclinical KC and N	AUROC		Cut-off point			Multiple factor models
			Parameter that achieves high AUROC	AUROC (%)	Value	Sensitivity (%)	Specificity (%)	Content of model	Sensitivity (%)	Specificity (%)
De Sanctis et al10 (2008)	Pentacam	Yes	Max PE5	93	29 μm	68	90.8
Jafarinasab et al47 (2011)	Galilei	Yes	Max PE7	92	50.5 μm	79.9	94
Ucakhan et al48 (2011)	Pentacam	Yes	Max PE5	78.9	20.5 μm	81.8	66.7	All posterior elevation parameters combined in model All posterior elevation parameter + cornea power + thickness	56.8 77.3	85.7 92.1
Arbelaez et al18 (2012)	Sirius							Anterior cornea surface data (curvature, thickness, and height) Anterior + posterior cornea surface and pachymetry data (curvature, thickness, and height)	75.2 92	94.9 97.7
Ruiseñor Vázquez et al17 (2014)	Pentacam	Yes Yes	Db Da	80 94	0.78 1.26	62.2 89.2	88.2 90.3

Notes: Modalities used to achieve posterior elevation and derived parameters include Pentacam, Galilei, and Sirius. All the best posterior parameters have a significant difference between subclinical keratoconic eyes (KC) and normal eyes (N). AUROC, area under receiver operating characteristic curve, is a tool to select optimal models for diagnostic decision making. In this table, a parameter or model with a higher AUROC has higher sensitivity and specificity to discriminate subclinical keratoconus from normal eyes. Cut-off point is the parameter value at which the highest sensitivity and specificity are achieved. Notice not a single posterior parameter was able to achieve greater than 90% in both sensitivity and specificity. Multiple factor models are the logistic regression model of artificial intelligence models that involves more than one parameter. Notice adding cornea power and thickness into the model improves both sensitivity and specificity from only using posterior elevation parameters alone. Adding posterior cornea parameters to the model improves sensitivity and specificity from only using anterior cornea parameters. And this anterior + posterior cornea surface and pachymetry data (curvature, thickness, and height) model achieves larger than 90% in both sensitivity and specificity. Max PE5 is a parameter that measures the maximum posterior elevation from the reference best-fit sphere within the central 5 mm of cornea. Max PE7 is similar to Max PE5 but measures within the central 7 mm of cornea. Db and Da both were obtained from the Pentacom software Belin-Ambrosio Enhanced Ectasia Display. Db is the deviation of the normality of the back cornea elevation, whereas Da is the deviation of the normality of relational thickness. Relational thickness indices express the ratio of the thinnest pachymetry and the respective pathymetry progression. Pachymetry progression refers to the percentage in cornea thickness increase along each meridian starting from the thinnest corneal point.