Validity and Reliability of 2 Cirrus Optical Coherence Tomography Procedures for Measuring Objective Ocular Torsion.

Purpose: Torsional eye position by the disc-fovea angle (DFA) is a relevant objective parameter in vertical strabismus. DFA measurement with optical coherence tomography (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 2 undescribed Cirrus high-definition OCT (HD-OCT; Carl Zeiss Meditec) methods that offer clinical advantages for measuring objective cycloposition in normal patients compared with Spectralis spectral-domain OCT (Heidelberg Engineering) and the reference method.

Design: Prospective validity and reliability analysis.

Methods: Objective 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 spectral-domain 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 3 times for each method and the patient was repositioned and realigned between captures. Posterior manual quantification was made by 2 observers with external protractor software for the fundus and cube methods.

Results: The 3 OCT methods showed and excellent agreement with fundus photography (ICC 0.83-0.84) with no significant differences comparing mean values (P = .36 for fundus-FoDi, P = .09 for fundus-line, and P = .09 for fundus-cube). Absolute differences between methods were 1.5°. All methods showed excellent reliability (ICC 0.92 for FoDi, 0.91 for line, 0.92 for cube, and 0.91 for fundus). The minimal detectable change was lower than 3° and the absolute difference between repeated measurements was 1° for all methods. Interrater reliability was excellent for methods requiring manual quantification (ICC 0.98 for cube, ICC 0.94 for fundus).

Conclusions: Measurement 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.