Chan 2015.

Study characteristics
Patient Sampling	Retrospective case‐control study; 128 topographic images of 128 people were selected at the Singapore National Eye Center
Patient characteristics and setting	The forme fruste keratoconus group (24 images) involved clinically and topographically normal eyes with the contralateral eye showing frank keratoconus. These cases were obtained from the database of people with keratoconus from the Singapore National Eye Center. The diagnosis of keratoconus in the contralateral eye was reconfirmed by clinical examination and evaluation of topographies from the Orbscan IIz corneal topography system (Bausch + Lomb TechnoLas, Munich, Germany) and Tomey keratoconus screening system (TMS, software version 2.4.2J, Tomey TMS‐2N; Tomey Corp, Nagoya, Japan) by a corneal sub‐specialist. The control group (104 images) involved normal preoperative topographies of people who had myopic LASIK (with or without astigmatism) performed at least 4 years before with no resultant ectasia.
Index tests	The SCORE Analyzer is based on a linear regression analysis that constructs a set of linear functions of variables known as discriminant functions. It combines 12 Placido and tomographic indices in a weighted fashion to classify corneas as suspicious for keratoconus or normal.
Target condition and reference standard(s)	Clinically evident keratoconus was defined by evidence of ≥ 1 slit‐lamp biomicroscopic findings including conical protrusion of the cornea at the apex, Fleischer's ring, Vogt's striae, and corneal stromal thinning. The classification was performed by 1 corneal specialist. Cases were classified before inclusion.
Flow and timing	All cases were included in the reference standard and index test. All data were included in a 2 × 2 table.
Comparative	Not applicable
Notes	No funding source mentioned.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient selection
Was a consecutive or random sample of patients enrolled?	No
Was a case‐control design avoided?	No
Did the study avoid inappropriate exclusions?	No
Could the selection of patients have introduced bias?		High risk
Are there concerns that the included patients and setting do not match the review question?			High
DOMAIN 2: Index test (All tests)
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	Yes
Was the model designed in an appropriate manner?	Yes
Could the conduct or interpretation of the index test have introduced bias?		Low risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			Low concern
DOMAIN 3: Reference standard
Is the reference standard likely to correctly classify the target condition?	No
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
Could the reference standard, its conduct, or its interpretation have introduced bias?		High risk
Are there concerns that the target condition as defined by the reference standard does not match the question?			Low concern
DOMAIN 4: Flow and timing
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Could the patient flow have introduced bias?		Low risk
DOMAIN 5: Comparative