A quantitative analysis method for comitant exotropia using video-oculography with alternate cover

Nohae Park, Byunggun Park, Minkyung Oh, Sunghyuk Moon, Myungmi Kim, Nohae Park, Byunggun Park, Minkyung Oh, Sunghyuk Moon, Myungmi Kim

Abstract

Background: The purpose of this study was to evaluate the efficacy of a quantitative analysis method for comitant exotropia using video-oculography (VOG) with alternate cover.

Methods: Thirty-four subjects with comitant exotropia were included. Two independent ophthalmologists measured the angle of ocular deviation using the alternate prism cover test (APCT). The video files and data of changes in ocular deviation during the alternate cover test were obtained using VOG. To verify the accuracy of VOG, the value obtained using VOG and the angle of a rotating model eye were compared, and a new linear equation was subsequently derived using these data. The calculated values obtained using VOG were compared with those obtained using the APCT.

Results: Rotation of the model eye and the values obtained using VOG demonstrated excellent positive correlation (R = 1.000; p < 0.001). A simple linear regression model was obtained: rotation of the model eye = 0.978 × value obtained using VOG for a model eye - 0.549. The 95% limit of agreement for inter-observer variability was ±4.63 prism diopters (PD) for APCT and that for test-retest variability was ±3.56 PD for the VOG test. The results of APCT and calculated VOG test demonstrated a strong positive correlation. Bland-Altman plots revealed no overall tendency for the calculated values obtained from VOG to differ from those obtained using APCT.

Conclusions: VOG with alternate cover is a non-invasive and accurate tool for quantitatively measuring and recording ocular deviation. In particular, it is independent of the proficiency of the examiner and, can therefore, be useful in the absence of skilled personnel.

Trial registration: ClinicalTrial.gov, NCT03119311 , Date of registration: 04/17/2017, Date of enrolment of the first participant to the trial: 04/25/2017.

Keywords: Alternate cover; Ocular deviation; Strabismus; Video-oculography.

Conflict of interest statement

Ethics approval and consent to participate

All aspects of the research protocol complied with the tenets of the Declarations of Helsinki and were approved by the Institutional Review Board of Inje University Busan Paik Hospital (Busan, Korea). Written informed consent was obtained from all parents or legal guardians; children and adolescent assent forms were also provided for children 7 years of age and older.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
The rotation of the model eye and the value obtained using video-oculography demonstrated excellent positive correlation (R = 1.000; p < 0.001) (rotation of model eye [degrees] = 0.978 × value obtained from video-oculography of the model eye [degrees] – 0.549; R2 = 0.999)
Fig. 2
Fig. 2
Interface of the video-oculography device. This image reveals the degree of movement of the eyeball in the form of a graph. The red line refers to the movement of the right eye, and the amount of change in the two points (in the circle) is represented by an angle in the square
Fig. 3
Fig. 3
Bland-Altman plots revealing interobserver variability and inter-visit variability for the alternate prism cover test (APCT) and test-retest variability for video-oculography with alternate cover. Upper and lower dotted lines represent the 95% limits of agreement. The half-width of the 95% limit of agreement measured of the interobserver variability (top left), inter-visit variability (top right) for APCT and test-retest variability (bottom) for video-oculography were 4.63 prism diopters (PD), 5.74 PD and 3.56 PD, respectively
Fig. 4
Fig. 4
Bland-Altman plot comparing the values obtained using the alternate prism cover test (APCT) and video-oculography (VOG) test. The Bland-Altman plot demonstrated consistent variability. The half-width of the 95% limit of agreement was ±5.05 prism diopters. There was no overall tendency for the values obtained using VOG to differ from those obtained using APCT
Fig. 5
Fig. 5
Scatter plot and Pearson correlation between values calculated using video-oculography (VOG) and the values obtained using the alternate prism cover test (APCT). The values calculated from VOG demonstrated a strong correlation with the values obtained using APCT (R = 0.934; p < 0.001)

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