Quantitative Measurement of Inferior Oblique Muscle Overaction using Photographs of the Cardinal Positions of Gaze

Abstract

 

Purpose

 

To measure the amount of inferior oblique muscle overaction (IOOA) using photographs of the cardinal positions of gaze.

 

Methods

 

Photographs were obtained in the nine cardinal positions of gaze and the images were processed using Photoshop. The images were analyzed using the Image J program to measure the amount of IOOA. The amount of IOOA was defined as the angle formed by the intersection between a horizontal line and the tangent line which corresponds to direction of ocular movement.

 

Results

 

We analyzed photographs of 102 eyes with primary IOOA and 40 eyes with secondary IOOA. The mean degrees of IOOA were 10.5±9.1°, 16.8±7.8°, 24.3±8.8°, and 40±12.2° in the grade +1 (n=29), +2(n=76), +3(n=34), and+4(n=3) group respectively (P < 0.001, ANOVA, Turkey’s test). The degree of IOOA showed good correlation with the clinical 4-step grading scale (R = 0.549, P < 0.001) and with hypertropia in the adducted position (R = 0.294, P = 0.001).

 

Conclusions

 

A modified limbus test using photographs of the cardinal positions can be used to measure the amount of IOOA quantitatively, and this technique showed excellent agreement with the standard grade scale. This objective method is an accurate and reliable tool for measuring IOOA with minimal observer dependency.

 

 

 

Keywords: 723 strabismus: diagnosis and detection • 524 eye movements: recording techniques • 550 imaging/image analysis: clinical