Researchers initially thought that clinical vergence testing correlated with the oculomotor demands of 3D viewing, considering it is the only component of routine clinical ocular motility testing that presents a visual experience; however, new data suggests that’s not the case.

The study tested the phoropter prism vergence limits of clear and single vision at 40cm in 47 binocular young adults. In separate sessions, the researchers tested, in a 3D display, the analogous 40cm vergence limits for smooth vergence and jump vergence. The mean smooth divergence limit was less in the 3D display (9.8Δ) than in the phoropter (12.8Δ), and most smooth convergence limits were much larger in the 3D display than in the phoropter, reaching the 35Δ limit of the 3D display without blur or diplopia in 24 subjects. The study concluded that clinicians cannot measure smooth vergence ranges in a clinical setting and assume that they are the same in 3D viewing.

It also found that the mode of depth shift—smooth vs. jump—might affect vergence range in a 3D setting.

The researchers believe that today’s children (whose developing visual systems are still developing) are at in increased risk of 3D-induced accommodation/convergence mismatch because they are more likely to use near 3D display, such as handheld 3D gaming devices. This could cause maldevelopment of binocular vision and/or ocular motility.

Although their study did not clarify the relationship between clear and single vision and visual comfort for 3D viewing, the researchers believe doctors should not use clinical vergence measurements under the assumption that they are also measuring vergence ranges in 3D viewing.

McCormack GL, Hogan KM. Clear and single binocular vision in near 3D displays. Optom Vis Sci. October 31, 2019. [Epub ahead of print].