The Normal Accommodative Convergence/Accommodation (AC/A) Ratio.

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• The Accommodative Convergence (PD)/Accommodation ratio (AC/A) is a critical clinical measure.
• Standardized AC/A ratio values are widely accepted in clinical practice.

Purpose of the Study:

• To measure the AC/A ratio in a cohort of visually normal participants.
• To compare AC/A ratios obtained using common clinical methods.

Main Methods:

• Fifty visually normal subjects participated in the study.
• AC/A ratios were measured using four methods: distance gradient (DG), near gradient (NG), synoptophore gradient (SG), and heterophoria (H).

Main Results:

• Median AC/A ratios varied significantly across methods: NG (2.0), DG (1.0), SG (1.0), and H (5.0).
• Statistically significant differences were found between most method pairs (p < 0.05), except DG vs. SG.
• Lens power toleration and latent deviation influenced AC/A ratios in specific methods.

Conclusions:

• AC/A ratios in this cohort were lower than historical norms for gradient methods.
• Different clinical methods yield non-interchangeable AC/A values.
• A universal normal range for AC/A ratios should not be applied across all measurement techniques.