Under open-loop conditions, what is expected when lenses are added regarding fusional vergence?

Under open-loop conditions, what is expected when lenses are added regarding fusional vergence?

• A. Under closed-loop conditions, fusional reserves are not utilized.
• B. Open loop conditions maximize fusional vergence stress.
• C. Closed loop conditions show no change in vergence demands.
• D. In OPEN LOOP conditions, there is no stimulus to fuse, so there is no stress on NFV or PFV.

Answer: (D)

Open-loop conditions remove the need to fuse the two images. There’s no disparity cue or feedback driving the eyes to align, so adding lenses doesn’t create a stimulus to fuse. Without that fusion demand, the fusional vergence system isn’t stressed, so neither negative fusional vergence nor positive fusional vergence reserves are engaged. In contrast, under closed-loop conditions, a fusional demand would arise from the disparity created by misalignment and lens changes, triggering NFV or PFV. So the expected outcome in open-loop with lenses is that there’s no stimulus to fuse and no stress on NFV or PFV.

Open-loop conditions remove the need to fuse the two images. There’s no disparity cue or feedback driving the eyes to align, so adding lenses doesn’t create a stimulus to fuse. Without that fusion demand, the fusional vergence system isn’t stressed, so neither negative fusional vergence nor positive fusional vergence reserves are engaged. In contrast, under closed-loop conditions, a fusional demand would arise from the disparity created by misalignment and lens changes, triggering NFV or PFV. So the expected outcome in open-loop with lenses is that there’s no stimulus to fuse and no stress on NFV or PFV.