Untersuchungen über das binokulare Gesichtsfeld Schielender

Abstract

Sensory adaption, i.e. suppression and the status of retinal correspondence were examined with different methods using a special modification of the phase difference haploscope in 25 cases of eso- and 24 cases of exotropia. Three campimetric techniques were carried out:

• 1. Haploscopic perimetry with moving and stationary targets (isopter and profile perimetry),

• 2. suprathreshold haploscopic perimetry with a monocularly presented grid of 60 degrees in diameter (raster scotometry),

• 3. contemporaneous stimulation with different quality of images for both eyes as far as color, direction of contours and luminance are concerned (‘Anteil’ perimetry).

Size and reproducibility of the suppression scotomas were different with each method. The light sense of the squinting eye for stationary targets (profile perimetry) was not inhibited. However, form perception and localization of the stimulus were uncertain in those areas, were suppression was present with other methods.

A slowly moving target revealed a fixation point scotoma in most cases; however, its intensity and size were not reproducible.

Stable scotomas ot reproducible size were found with raster scotometry, i.e. presenting a not changing large grid pattern of 60 degrees.

Almost in all cases there was inhibition of those retinal areas of the deviated eye, which beared the same visual direction of the fovea of the fixing eye; i.e. around the fixation point no grid pattern was perceived. It was also possible to demonstrate a scotoma in the fixing eye of alternators. Its position in the binocular visual field was based on the visual direction of the fovea of the deviated eye.

With raster scotometry the unpatterned luminous field, to which the not examined eye was exposed, was once presented with equal intensity as the bright squares (100 asb), and once with the intensity of the dark lines of the grid presented to the tested eye. No difference was found in the size of the scotomas in both experimental conditions.

In most cases of esotropia with anomalous retinal correspondence (ARC) there was a circumscribed fixation point scotoma. On the other hand suppression affected much larger areas and showed a hemianopia-like character in exotropia and ARC. The scotomas were on the side of the not examined eye and extended up to the periphery. No stable inhibition could be determined in squinters with normal retinal correspondence.

With the ‘Anteil’ perimetry all patients with ARC split their binocular visual field in two parts of dominance in favour of those retinal areas, which provided the higher functions also under monocular conditions. Therefore using binocular perimetry with the test target visible to both eyes, two peaks of light sensitivity were found in cases with ARC.

Therefore, the following order can be set up concerning the likelihood of finding a steady suppression scotoma of one eye:

The shift of the visual direction of the deviated eye in cases of ARC, i.e. the angle of anomaly, has not been found to be the same in all retinal points. The scotomatous areas showed mainly smaller angles of anomaly as compared to the not suppressed areas in the binocular visual field.

This comparative study proves, that the usual clinical methods (isopter and profile p.erimetry) are not suitable for evaluation of suppression scotomas.

On the other hand, with the raster scotometry used in this study it was possible to find and reproduce the areas of suppression very easily. Also the extinction phenomenon (Aulhorn, 1967) can be very impressively demonstrated with this method.

Finally, the art of seeing with both eyes in a squinting subject is summarized and the possible neuronal mechanism of the sensory adaption phenomena in strabismus are discussed.