Convergence accommodation to convergence CA/C ratio: convergence versus divergence.

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• The relationship between vergence and accommodation is crucial for clear binocular vision.
• The convergence accommodation to convergence (CA/C) ratio quantifies this relationship.
• Investigating the CA/C ratio under different vergence demands, such as convergence and divergence, is important for understanding visual function.

Purpose of the Study:

• To compare the CA/C ratio during prism-induced convergence (using base-out prisms) and divergence (using base-in prisms).
• To determine if the magnitude of the CA/C ratio differs between convergence and divergence conditions.

Main Methods:

• Eighteen participants with normal binocular vision were tested.
• Participants viewed a target at 40 cm and had their refractive status measured.
• Base-out (BO) and base-in (BI) prisms (5Δ and 10Δ) were used to induce convergence and divergence, respectively, while refractive error was measured.

Main Results:

• The mean CA/C ratios were similar for all prism conditions: 5Δ BO (0.108 D/Δ), 10Δ BO (0.110 D/Δ), 5Δ BI (0.100 D/Δ), and 10Δ BI (0.089 D/Δ).
• A two-factor repeated measures ANOVA revealed no statistically significant change in the CA/C ratio based on the level or direction of prism-induced vergence (p=0.649).

Conclusions:

• The induced change in accommodation due to manipulated vergence is comparable whether convergence or divergence is stimulated.
• The CA/C ratio is stable and does not significantly change with differing levels of prism-induced convergence or divergence.