Variations in accommodation and convergence responses in a minimally controlled photorefractive setting

Area of Science:

• Ophthalmology
• Vision Science
• Optometry

Background:

• Accommodation and convergence are crucial for clear binocular vision.
• Accurate measurement of the accommodative convergence/accommodation (AC/A) ratio is important for diagnosing and managing binocular vision disorders.
• Conventional clinical measures may have limitations in certain populations, such as infants.

Purpose of the Study:

• To evaluate a remote haploscopic photorefractor for assessing accommodation and convergence.
• To determine heterophoria and AC/A ratios in normal, non-clinical adult subjects.
• To compare measurements from the remote photorefractor with conventional clinical methods.

Main Methods:

• Twenty-one healthy adult subjects participated.
• Responses were measured using a remote haploscopic photorefractor with text and picture targets.
• Prism cover test responses were compared under occluded and unoccluded conditions.

Main Results:

• Binocular vergences were appropriate for target demands despite low luminance.
• Accommodation showed greater lag at high and low accommodative demands.
• Occlusion reduced vergence and accommodation, particularly with a picture target.
• Normal mean AC/A ratios were observed, but with significant individual variability.

Conclusions:

• The remote photorefractor provided comparable mean accommodation, vergence, and AC/A values to existing data.
• Accommodation accuracy was frequently compromised by occlusion in naïve subjects at low light levels.
• Accommodative convergence may contribute less to the near reflex than previously thought, with other cues playing a larger role.