Pilot Study Comparing the Ocular Deviation Measures of Basic Intermittent Exotropia Using 2WIN-S and Prism Cover Test

Area of Science:

• Ophthalmology
• Pediatric Ophthalmology
• Strabismus Diagnosis

Background:

• Intermittent exotropia (IXT) is a common childhood strabismus.
• Measuring IXT is challenging due to fluctuating deviation and control.
• The prism cover test (PCT) is the gold standard but is examiner-dependent.

Purpose of the Study:

• To assess the 2WIN-S photoscreener's ability to quantify ocular deviation in basic IXT.
• To determine if the level of IXT control affects agreement with the PCT.
• To evaluate the clinical utility of the 2WIN-S for IXT measurement.

Main Methods:

• Nineteen children with basic IXT were included.
• Ocular deviation was measured using the 2WIN-S photoscreener and PCT.
• Control levels were graded, and data were analyzed using Bland-Altman plots.

Main Results:

• The 2WIN-S showed significantly lower deviation measurements compared to PCT (median difference 14.13 pd).
• Agreement between the two methods was poor across all deviation magnitudes.
• The 2WIN-S incorrectly reported orthophoria in five cases with significant IXT.

Conclusions:

• The 2WIN-S photoscreener is currently unreliable for quantifying basic IXT.
• Methodological or optical refinements are needed before clinical use.
• The device should not be used for IXT quantification without further improvements.