Comparison of methods for determining the AC/A ratio in accommodative esotropia

Area of Science:

• Ophthalmology
• Optometry
• Binocular Vision

Background:

• The accommodative convergence/accommodation (AC/A) ratio is crucial for understanding binocular vision disorders.
• Clinical assessment of a high AC/A ratio typically involves the gradient method and the distance/near disparity method.
• Discrepancies exist between these methods and even within variations of the gradient method.

Purpose of the Study:

• To compare the diagnostic frequency of a high AC/A ratio using the gradient method (with +3.00 and -3.00 lenses) versus the distance/near disparity method.
• To evaluate potential variability in AC/A ratio measurements obtained with the gradient method using different lens powers.

Main Methods:

• Prospective study of 45 patients diagnosed with high AC/A ratio esotropia via the distance/near disparity method.
• AC/A ratio assessed using the gradient method with +3.00 lenses for near and -3.00 lenses for distance.
• Measurements were conducted with full spectacle correction and cycloplegic refraction, fixating on an accommodative target.

Main Results:

• The distance/near disparity method identified a high AC/A ratio in all 45 patients.
• The gradient method classified 16 (36%) patients as having a high AC/A ratio.
• Twenty-three patients (51%) showed differing AC/A ratio classifications between the gradient method's plus and minus lens assessments.

Conclusions:

• The distance/near disparity method appears more sensitive for diagnosing high AC/A ratios compared to the gradient method.
• The gradient method demonstrated variability in AC/A ratio measurements when using plus versus minus lenses.
• Further research is needed to clarify the gradient method's utility in patients without significant distance/near disparity.