The main idea is that the NRA endpoint marks the limit of the binocular system’s ability to maintain single, clear vision as relative accommodative/vergence demand increases. You’re testing how far the eyes can relax accommodation (and the corresponding vergence) before fusion or clarity breaks down. The best description is that the endpoint is reached when accommodation can no longer stay clear (blur) or vergence can no longer stay aligned (diplopia). In other words, you stop the test at the first sign that the system can’t maintain fusion or sharpness, which defines the NRA limit. Depth perception isn’t the metric used here, and you don’t stop at perfect fusion or at a fixed amount like 1 diopter of demand.

The TV trainer is a passive form of anti-suppression therapy. It works by presenting binocular stimuli on a screen through filters so that both eyes participate in the viewing, encouraging the brain to fuse the images while the patient simply fixates and attends. There’s no requirement for active, physically demanding tasks or rapid, purposeful eye movements; the therapy relies on sensory input and binocular fusion, not on motor training. The idea is to reduce suppression by making fusion the natural outcome of viewing, rather than teaching the eyes to perform specific rapid or strenuous actions.

When using plus lenses, they reduce the amount of accommodation the eyes need for a near target by providing part of the focusing power. To keep accommodative therapy effective, you want to challenge the system without overloading it. Moving the target closer increases the demand on accommodation and vergence, but the plus lenses cushion that demand, allowing a controlled, tolerable challenge. This pairing helps improve accommodation and convergence responses over time while keeping the exercise comfortable. Increasing the working distance would lessen the demand too much and make therapy less effective, and using minus lenses would raise demand in a way that plus lenses aren’t meant to balance.

Near point of convergence shows how close a binocular target can come before the eyes can no longer fuse it into a single image. It tests the vergence system’s ability to converge the eyes together as a target moves toward the face, which also depends on accommodation. In healthy adults, the break point—where single vision is lost—typically falls around 6 to 10 centimeters from the eyes. Shorter break distances mean the eyes can converge more strongly and maintain fusion at closer distances, which is generally a sign of robust vergence control. Longer break distances suggest weaker convergence and can be a clue toward convergence insufficiency or related near-vision symptoms. The exact numbers can vary somewhat with how the test is performed, the target used, and individual factors, but 6–10 cm is the commonly cited normative range.