Validity and reliability of two Cirrus HD-OCT procedures for measuring objective ocular torsion.

PurposeTorsional eye position by the disc-fovea angle (DFA) is a relevant objective parameter in vertical strabismus. DFA measurement with OCT has proven to be a good alternative to the gold standard measurement in fundus photography. Our study aims to analyze the validity and reliability of two undescribed Cirrus HD-OCT methods that offer clinical advantages for measuring objective cycloposition in normal patients compared to the Spectralis SD-OCT and the reference method.DesignProspective validity and reliability analysis.MethodsObjective cycloposition by means of the DFA was measured in the right eyes of 59 binocularly normal individuals attending the ophthalmology service of a medical institution. DFA was obtained by fundus photography (gold standard), FoDi software of Spectralis SD-OCT, HD 1 Line scan of Cirrus HD-OCT and Macular Cube of Cirrus HD-OCT (Fundus, FoDi, Line and Cube methods, respectively). Measurements were performed three times for each method and the patient was repositioned and realigned between captures. For Fundus and Cube methods posterior manual quantification was made by two observers with external protractor software.ResultsThe three OCT methods showed and excellent agreement with the fundus photography (ICC 0.83 to 0.84) with no significant differences comparing mean values (p = 0.36 for Fundus-FoDi, p = 0.09 for Fundus-Line, p = 0.09 for Fundus–Cube). Absolute differences between methods were 1.5 degrees. All methods showed an excellent reliability (ICC 0.92 for FoDi, 0.91 for Line, 0.92 for Cube, 0.91 for Fundus). Minimal detectable change was lower than 3 degrees and the absolute difference between repeated measurements was 1 degree for all methods. Interrater reliability was excellent for methods requiring manual quantification (ICC 0.98 for Cube, ICC 0.94 for Fundus).ConclusionsMeasurement of the DFA by Cirrus HD-OCT methods in normal patients was a valid and reliable alternative for the cycloposition assessment. Among the methods, the Cirrus OCT HD 1 Line improved clinical performance due to the simplicity and speed of measurement, with no need to export the image for quantification.