[Phase haploscopy and characteristics of stereoscopic perception in strabismic patients]

To identify the frequency range of alternating presentation of the left and right images that allow stereoscopic perception in strabismic patients.

The study included 34 patients aged 10-15 years with residual microdeviation or unstable strabismus angle that were put in the first group, and 32 second (control) group patients of similar age. The study subjects were presented 20 various stereograms created by J. Ninio under conditions of phase haploscopy.

The majority of the study patients were able to perceive depth with simple linear stereoscopic images. However, these patients had higher frequency threshold (F_min) than control subjects and, in contrast, appeared to have an upper limit of alternation frequency (F_max). Thus, for each patient with strabismus, the values of F_min and F_max limited the frequency range where stereopsis was possible. Simple linear stereoscopic images had the widest range (7.6±0.6 Hz for F_min and 33.6±0.9 Hz for F_max). Smaller range (9.9±1.1 Hz for F_min and 23.3±1.2 Hz for F_max) was identified for stereograms depicting slanted surfaces. Fewer patients with strabismus achieved stereopsis with complex random-dot stereograms within a narrow range of high alternation frequencies (16.1±1.1 Hz for F_min and 25.2±2.1 Hz for F_max).

The study revealed that even patients with pathologies of binocular vision can perceive specific stereograms when presented with alternating stimuli. This opens prospects for further research on methods of recovering and developing binocular vision function in strabismic patients.