accommodative convergence/accommodation ratio
Also written as: AC/A — accommodative convergence/accommodation ratio
The ratio of convergence response to accommodation stimulus, critical for diagnosing accommodative esotropia.
Full Definition
The accommodative convergence/accommodation (AC/A) ratio measures how much convergence occurs for each diopter of accommodation. A high AC/A ratio indicates that accommodation triggers excessive convergence, often leading to accommodative esotropia. This ratio is essential for determining appropriate treatment strategies, including the use of bifocals or cycloplegic agents. Normal AC/A ratios range from 3:1 to 5:1, while ratios above 6:1 are considered high and clinically significant.
Usage
Usage note: Always express as a ratio (e.g., 4:1) and specify measurement conditions (gradient vs. heterophoria method).
In Context
- "The patient's high accommodative convergence/accommodation ratio of 8:1 explained the intermittent esotropia during near tasks." — Clinical examination report
- "Bifocal prescription was indicated given the elevated AC/A ratio and near esotropia." — Treatment plan documentation