What distinguishes stimulus AC/A from response AC/A?

What distinguishes stimulus AC/A from response AC/A?

• A. Stimulus AC/A uses actual accommodative response; response AC/A uses accommodative stimulus
• B. Stimulus AC/A uses the accommodative stimulus; response AC/A uses the actual accommodative response
• C. Stimulus AC/A uses near phoria; response AC/A uses far phoria
• D. Stimulus AC/A is independent of accommodation; response AC/A depends on accommodation

Answer: (B)

Understanding the difference between accommodative stimulus and accommodative response in the AC/A ratio is what this is about. The stimulus version uses the accommodative stimulus—the dioptric demand imposed by the target's distance—so it asks how much convergence occurs for that imposed amount of accommodation. The response version uses the actual accommodative response—the real amount of accommodation the eye achieves. If the target demands 2.50 D but the eye only accommodates 1.50 D, the stimulus-based calculation would relate convergence to 2.50 D, while the response-based calculation relates convergence to 1.50 D. That’s why using the accommodative stimulus in one case and the actual accommodative response in the other is the key distinction.

Understanding the difference between accommodative stimulus and accommodative response in the AC/A ratio is what this is about. The stimulus version uses the accommodative stimulus—the dioptric demand imposed by the target's distance—so it asks how much convergence occurs for that imposed amount of accommodation. The response version uses the actual accommodative response—the real amount of accommodation the eye achieves. If the target demands 2.50 D but the eye only accommodates 1.50 D, the stimulus-based calculation would relate convergence to 2.50 D, while the response-based calculation relates convergence to 1.50 D. That’s why using the accommodative stimulus in one case and the actual accommodative response in the other is the key distinction.