A Ganzfeld contact lens electrode

Progressive cone dystrophy

Psychophysical, reflectometric, and electrophysiologic studies were done on four members of a dominant pedigree with progressive cone dystrophy. The two youngest individuals were asymptomatic at the initial examination, and none of the subjects complained of problems associated with night vision. Nevertheless, absent or grossly reduced cone-mediated electroretinographic (ERG) responses showed the widespread loss of cone function, and moderate elevations (less than 1 log unit) in absolute threshold together with reductions in rhodopsin levels in the mid-peripheral retina provided evidence of impairment of the rod system. The progressive nature of the disease was apparent from the case histories and the changes in visual performance that occurred on re-test after a 5-year interval. Moreover, the results of increment threshold measurements at several retinal loci suggested that peripheral cones may be affected earlier and more severely than those in the central retina.

A tricolor light source for stimulation and adaptation in electroretinography

A Ganzfeld light source, fitted on an electroretinogram contact lens, is described. The light source can provide blue, green, or red flashes with intensities over a range of 3.6 log units. It can also be used to provide a continuous light-adapting background in each of the above-mentioned colors, simultaneously presenting the possibility of emitting flashes. The control unit and the light source can be powered by a small battery pack.

Light distribution on the retina of a wide-angle theoretical eye

In a theoretical eye with spherical and aspheric surfaces, the retinal illumination is calculated if a Ganzfeld luminance field is used. The resulting retinal light distribution is nearly homogeneous over the whole retina. The homogeneity is not much influenced by the size of the optical surfaces. The corresponding retinal area and the luminous flux entering the eye are calculated as functions of the size of the visual field. The values of the length of the light path through the crystalline lens and of the angle of incidence on the retina are described as functions of the angle in the visual field.

Familial foveal retinoschisis associated with a rod-cone dystrophy

A brother and sister born of a consanguinous marriage had bilateral foveal retinoschisis and a generalized rod-cone dysfunction. This was associated with nyctalopia, hyperopia, minimal vitreous opacities in the sister, a paramacular tapetal sheen reflex, normal retinal vessels, an abnormal electroretinogram, and a normal electro-oculogram in the less affected brother. Foveal retinoschisis is not pathognomonic for x-chromosome-linked juvenile retinoschisis. It may be seen as a manifestation of a macular dystrophy or associated with a generalized tapetoretinal dystrophy.

A corneal electrode for patterned stimulus electroretinography

A corneal contact lens electrode employs a silver-coated hard contact lens placed onto a soft contact lens. The electrode is used without corneal anesthesia and has excellent optical characteristics that allow reliable and convenient recording of patterned electroretinograms.