Binocularity in comitant strabismus: II. Objective evaluation with visual evoked responses

Abstract

Campos (1982a) reported on his psychophysical studies on the binocularity of patients with comitant strabismus. With binocular visual field techniques, it was possible to show that patients with small-angle eso- and exotropia exhibit a binocular vision, without suppression of the deviated eye. In the present paper visual electrophysiology is used objectively these findings and to provide more insight in the problem. First, the studies on binocularity in normals and strabismics, done by using visual evoked responses (VER) are reviewed. This type of investigation is relatively new and the results of the literature are still conflicting. Then personal results of the authors are reported. It is shown that with VER it is possible to objectively assess the presence of anomalous binocular vision (ABV) sustained by anomalous retinal correspondence (ARC) in small-angle strabismus. In patients with large angle deviations this type of binocularity is absent. A correlation between psychophysical and electrophysiological data is provided. Lastly a simple method is described for differentiating the binocularity of normals from that of Strabismics with ARC. This method is based on the recording of binocular VER with the anteposition in front of the fixing eye of neutral filters of increasing density.

Incremental binocular amplitude of the pattern visual evoked potential during the first five months of life: electrophysiological evidence of the development of binocularity

“…Depending on spatial and temporal parameters of the stimulus absence of summation (B/lVl = 1) is sometimes demonstrable as is, although very uncommonly, inhibition (B/1VI < 1) (Apkarian et al, 1981), Notwithstanding these last two limitations, the binocular increment of VEP amplitude has been widely used to objectively study binocular vision in suprathreshold conditions of stimulation (Cobb et al, 1967;Lawwill and Biersdorf, 1968;Mackay, 1968;Martin, 1970;Spekreijse et al, 1972;Harter et al, 1974;Tyler and Kaitz, 1977;Amigo et al, 1978;Ellenberger and Shuttlesworth, 1978;Srebro, 1978;Wanger and Nillson, 1978;Lennerstrand, 1978;Hoepner, 1980;Jacobson and Lennerstrand, 1981). Recent electrophysiological data are consistent with the opinion that VEP binocular summation is the electrophysiological counterpart of sensorial fusion (Campos and Chiesi, 1983). In fact, VEP summation has been found both in subjects with normal binocular vision and in strabismic patients with so-called "anomalous binocular vision" (Bagolini, 1976a(Bagolini, , 1976b, whereas it was not demonstrable in subjects with suppression or diplopia.…”

Distance judgement in comitant strabismus with anomalous retinal correspondence

“…Nevertheless a better distance perception was obtained in a binocular condition. Therefore, monocular clues can be excluded for explaining these results, which can be attributed to a binocular cortical integration (Campos and Chiesi, 1983).…”

“…Anomalous binocular vision has been examined with campimetric techniques (Campos, 1982) and has been confirmed objectively by means of visual evoked responses (Campos and Chiesi, 1983). Esotropic patients with large suppression scotomas of the deviated eye do not take advantage of this type of binocularity.…”

Visual evoked potentials during suppression in exotropic and esotropic strabismics: strabismic suppression objectified

“…Dissociation can be introduced easily under test circumstances. However, without some form of dissociation between the eyes, suppression cannot be measured [3,4,7,8,16]. A strabismic suppression scotoma is an area of reduced sensitivity to stimuli in the deviating eye under binocular viewing conditions.…”