Clinical utility of ocular residual astigmatism and topographic disparity vector indexes in subclinical and clinical keratoconus.
OBJECTIVE
We aimed to characterize the distribution of the vector parameters ocular residual astigmatism (ORA) and topography disparity (TD) in a sample of clinical and subclinical keratoconus eyes, and to evaluate their diagnostic value to discriminate between these conditions and healthy corneas.


METHODS
This study comprised a total of 43 keratoconic eyes (27 patients, 17-73 years) (keratoconus group), 11 subclinical keratoconus eyes (eight patients, 11-54 years) (subclinical keratoconus group) and 101 healthy eyes (101 patients, 15-64 years) (control group). In all cases, a complete corneal analysis was performed using a Scheimpflug photography-based topography system. Anterior corneal topographic data was imported from it to the iASSORT software (ASSORT Pty. Ltd), which allowed the calculation of ORA and TD.


RESULTS
Mean magnitude of the ORA was 3.23 ± 2.38, 1.16 ± 0.50 and 0.79 ± 0.43 D in the keratoconus, subclinical keratoconus and control groups, respectively (p < 0.001). Mean magnitude of the TD was 9.04 ± 8.08, 2.69 ± 2.42 and 0.89 ± 0.50 D in the keratoconus, subclinical keratoconus and control groups, respectively (p < 0.001). Good diagnostic performance of ORA (cutoff point: 1.21 D, sensitivity 83.7 %, specificity 87.1 %) and TD (cutoff point: 1.64 D, sensitivity 93.3 %, specificity 92.1 %) was found for the detection of keratoconus. The diagnostic ability of these parameters for the detection of subclinical keratoconus was more limited (ORA: cutoff 1.17 D, sensitivity 60.0 %, specificity 84.2 %; TD: cutoff 1.29 D, sensitivity 80.0 %, specificity 80.2 %).


CONCLUSIONS
The vector parameters ORA and TD are able to discriminate with good levels of precision between keratoconus and healthy corneas. For the detection of subclinical keratoconus, only TD seems to be valid.
Ocular Surface and Cornea Unit, Department of Ophthalmology, Oftalmar, Hospital Internacional Medimar, C/Padre Arrupe, 20, 03016, Alicante, Spain. david.pinyero@ua.es.|Foundation for the Visual Quality FUNCAVIS, Fundación para la Calidad Visual, Alicante, Spain. david.pinyero@ua.es.|Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain. david.pinyero@ua.es.
David P
DP
Piñero
Ocular Surface and Cornea Unit, Department of Ophthalmology, Oftalmar, Hospital Internacional Medimar, C/Padre Arrupe, 20, 03016, Alicante, Spain.|Foundation for the Visual Quality FUNCAVIS, Fundación para la Calidad Visual, Alicante, Spain.
Rafael J
RJ
Pérez-Cambrodí
Ocular Surface and Cornea Unit, Department of Ophthalmology, Oftalmar, Hospital Internacional Medimar, C/Padre Arrupe, 20, 03016, Alicante, Spain.
Roberto
R
Soto-Negro
Ocular Surface and Cornea Unit, Department of Ophthalmology, Oftalmar, Hospital Internacional Medimar, C/Padre Arrupe, 20, 03016, Alicante, Spain.
Pedro
P
Ruiz-Fortes
Ocular Surface and Cornea Unit, Department of Ophthalmology, Oftalmar, Hospital Internacional Medimar, C/Padre Arrupe, 20, 03016, Alicante, Spain.
Alberto
A
Artola
D000293:Adolescent; D000328:Adult; D000368:Aged; D001251:Astigmatism / Q000175:diagnosis* / Q000503:physiopathology; D001699:Biometry; D002648:Child; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis* / Q000503:physiopathology; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult
Corneal astigmatism; Corneal topography; Keratoconus; Ocular residual astigmatism; Topography disparity