Infantile ET is typically a large angle deviation greater than how many prism diopters?

• A. 20 pd
• B. 30 pd
• C. 40 pd
• D. 50 pd

Answer: (C)

Infantile esotropia presents in infancy with a constant, inward turning of the eyes that is unusually large. In exam-style definitions, a “large-angle” infantile esotropia is typically taken as a deviation exceeding 40 prism diopters. This threshold helps distinguish it from smaller-angle esotropias that are more likely related to refractive issues or other etiologies. A deviation around 40 PD or more reflects the substantial misalignment characteristic of infantile ET and explains why such cases often require early surgical alignment to improve binocular function. While deviations near 20–30 PD are still significant, they do not fit the typical large-angle Infantile ET cutoff; 50 PD is possible but the conventional threshold cited is 40 PD.