What is the main stimulus that initiates accommodative vergence?

• A. Proximal Cue
• B. Retinal disparity
• C. Blur
• D. Accommodative Demand

Answer: (C)

Blur is the main trigger for accommodative vergence because it tells the visual system that the image needs clarity, prompting the eyes to increase accommodation to bring the image into focus. The accommodation response then drives convergence through the accommodative vergence link (the AC/A relationship). In other words, clearing blur initiates the focusing effort, and that focusing effort pulls the eyes inward to maintain single, clear vision at near.

Disparity drives a separate, fusional form of vergence once images are already formed, helping to fine-tune alignment, but it isn’t the initiating signal for accommodative vergence. Proximal cues and perceived distance can modulate vergence to some extent, yet the immediate trigger for the accommodative pathway remains blur-driven accommodation. The amount of accommodation required to focus on the target (accommodative demand) describes the task, not the starting cue.