Kazutaka Kani

Retinal sensitivity and spatial summation in the foveal and parafoveal regions

Retinal sensitivity and the critical area of the spatial summation in the foveal and parafoveal regions were investigated by using a fundus-controlled perimeter to monitor accurately a subjects fundus picture and target position on the retina. The first experiment showed that retinal sensitivity and the critical area change continuously from fovea to periphery and that the diameter of the critical area is a linear function of retinal eccentricity. In the second experiment, this linear relationship was verified by another method.

Fundus Controlled Perimetry

New instrument for fundus controlled perimetry was presented. This instrument is composed of an infrared television ophthalmoscope, cathode ray tube for test object, background and fixation target. The light passes through the central part of the pupil. Perimetry was carried out by the instrument in normal subjects and in some clinical cases.

Eye movement analysis system using fundus images

Abstract This paper describes a precise eye movement analysis system that incorporates an infra-red television (fundus) camera and utilizes image processing techniques. Using this method, we can measure vertical and horizontal eye position and target position as a function of time. This system uses a two level hierarchical searching method to detect the papilla quickly. The first level gives a rough estimate of papillary position by detecting the papillary area with a mask operation (differential-like operation). The second level detects papillary position precisely by a correlation method. Finally, the paper describes experimental results of measuring eye movement in horizontal and vertical directions.

Characteristics of two systems of human vision using fundus perimetry

Electrophysiological studies confirmed two different cells, X- and Y-cells, underlying the visual system in primates. Furthermore, psycho-physical studies suggest existence of these two cells in human vision. However, these psycho-physical studies had many methodological and technical difficulties, and were not suitable for clinical application. In this study we applied the fundus perimeter to examine the spatial and temporal properties of the two different cells in human vision. The results were as follows: 1. The diameter of receptive field increased with retinal eccentricities from the fovea in both cells. 2. The diameter of the receptive field of Y-cells is always about three times the size of the receptive fields of X-cells at various retinal loci. 2. These results are in agreement with the properties of the receptive field in primate’s vision reported by electrophysiological and anatomical studies.

A New Automatic Perimeter

A new automatic perimeter has been developed. Light emitting diodes are mounted in a hemispheric dome and are controlled by a micro-computer. This perimeter has 8 topographical suprathreshold static programs and 4 threshold programs.

Spatial Summation in the Foveal and Parafoveal Region

Spatial summation effects have been studied in several retinal loci between 0° and 10° from fovea in normal and abnormal subjects using fundus controlled perimetry. Results of spatial summation were as follows: in normal subjects, spatial summation curves have two asymptotes — one shows complete spatial summation and the other shows no summation; in the fovea of amblyopic eye, spatial summation curves represent abnormal gradient with small target; in the eye of optic neuritis patient, spatial summation curves utterly lack the region of complete spatial summation immediately after the visual acuity returned to normal. These results suggest that our new instrument applied to evaluation of visual field in clinical practice is also available for analysis of human abnormal vision function in relation to pathogenesis.

FUNDUS CONTROLLED PERIMETRY IN OPTIC NEUROPATHY

Fundus controlled perimetry was carried out observing the fundus by means of an infrared television funduscopy in cases of optic neuropathy, such as Leber’s disease, infantile dominant optic atrophy, multiple sclerosis and optic atrophy of unknown origin, in which six cases were treated with craniotomy. Isopters were drawn on the fundus picture by means of static perimetry. The isopters showed very complicated shape compared with those obtained by conventional perimeters. High sensitive areas appeared at the fovea and/or at the retina along the superior and inferior temporal retinal vessels about 5 or 15 degrees apart from the disc in the recovery period of the disease. There was a correlation between the foveal sensitivity and the visual acuity.

Lateral Inhibition in the Fovea and Parafoveal Regions

Lateral inhibition in the light sense was investigated by using a fundus controlled perimeter to monitor simultaneously the fundus picture and stimulus location on the retina in four subjects.

A new numerical representation of the visual field in cases of chiasmal tumor

We have developed a new numerical representation of the visual field, in which the visual field is shown by the equation of retinal ganglion cell count multiplied by retinal sensitivity. This representation also presents the visual field defects directly in relation to the visual cortex. The relationship between the visual field defects shown in this representation and various neuroradiological factors were studied in case of chiasmal tumor using multivariate analysis. The preoperative visual field was found to be influenced significantly by the shape of the tumor, the presence A1 (A1 portion of anterior cerebral artery) elevation, and the depth of the sella turcica; the postoperative visual field was influenced by the depth of the sella turcica and by the height and transverse diameter of the tumor.