primary deviation
The measured strabismus angle when the normal (preferred) eye is fixating and the paretic or amblyopic eye is deviated.
Full Definition
Primary deviation refers to the angle of strabismus measured when the patient fixates with their preferred or normal eye, while the fellow eye assumes a deviated position. This measurement represents the baseline misalignment and is typically smaller than the secondary deviation in paralytic strabismus cases. Primary deviation is the standard measurement used for surgical planning and monitoring treatment progress. In non-paralytic strabismus, primary and secondary deviations are usually equal, helping distinguish between paralytic and non-paralytic causes of eye misalignment.
Usage
Usage note: Always specify which eye is fixating and distinguish from secondary deviation measurements.
In Context
- "The primary deviation measured 25 prism diopters of right esotropia with the left eye fixating." — Strabismus measurement documentation
- "Equal primary and secondary deviations supported the diagnosis of non-paralytic esotropia." — Differential diagnosis reasoning