Non-linearity of the response accommodative convergence to accommodation ratio.

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Previous research indicates variability in the accommodative convergence to accommodation (AC/A) ratio across different accommodative stimuli.
• The AC/A ratio is a key measure in assessing binocular vision function and vergence system responses.

Purpose of the Study:

• To investigate if variations in accommodative inaccuracies contribute to the reported differences in stimulus AC/A ratio.
• To assess the response AC/A ratio across four distinct accommodative demands.

Main Methods:

• Twenty-three participants (aged 18-26) underwent testing.
• Heterophoria was measured at 4 meters using the modified Thorington technique.
• Accommodative response to -1.50D, -3.00D, -4.50D, and -6.00D lens stimuli was determined using an infrared autorefractor.

Main Results:

• A significant difference in response AC/A ratio was observed across varying minus lens accommodative demands (p < 0.001).
• Mean AC/A ratios increased with accommodative demand, ranging from 3.11 ± 1.29 (-1.50D) to 4.48 ± 1.56 (-6.00D).
• Myopic participants exhibited higher mean response AC/A ratios (4.88 ± 1.89) compared to non-myopes (3.61 ± 1.47, p = 0.045).

Conclusions:

• The response AC/A ratio demonstrated a trend of increasing with accommodative demand, lacking linearity across the tested stimuli.
• Significant intra-individual and inter-individual variability in response AC/A ratio was identified.
• Findings suggest accommodative inaccuracies may influence the AC/A ratio, impacting binocular vision assessment.