Faculty Bibliography

Five of nine patients with Apert's syndrome (acrocephalosyndactyly) showed an associated hypopigmentation of hair, skin, and eyes. The hair color of these five patients ranged from light brown to blond, the skin was pale, and the irides hazel or blue. Iris transillumination and hypopigmentation of the fundus were present and associated with absent or diffuse foveal reflexes. Unlike most forms of classic oculocutaneous albinism, however, there was good visual acuity and no pendular nystagmus. The evidence indicated that the lack of pigmentation associated with the characteristic skeletal anomalies of Apert's syndrome resulted from a disturbance of independent, genetically related, processes occurring at a common point in gestation

The hereditary choroidal dystrophies are divided into (1) geographic choroidal dystrophies (central areolar, peripapillary, generalised), (2) gyrate atrophy, and (3) choroideremia. Each of these disorders is discussed with regard to mode of inheritance, age of onset, symptoms, fundus appearance, and visual function testing. A typical case history of each disorder is presented together with fluorescein angiography, and the fluorescein angiographic findings are related to our present understanding of these diseases. Fluorescein angiography was found to be most helpful in diagnosing the early cases, by confirming the absence of the choriocapillaris, and in demonstrating either a local or general abnormality. The role of fluorescein angiography in understanding the aetiology of choroidan dystrophies is discussed

Two patients had fundus albipunctatus, one of the variants of congenital stationary night blindness. Neither the white dots in the retinas of these patients nor the retarded course of dark adaptation characteristically associated with the disease could be attributed to vitamin A deficiency or raised oxalate levels since both substances were present in normal amounts. Fluorescin angiography showed multiple discrete lesions in the pigment epithelium not coincident with the ophthalmoscopically visible changes. Since the pigment epithelium is the storage site for bleached visual pigment, these findings suggest abnormalities that underlie the major functional deficit in this disease, that is, the slow recovery of retinal sensitivity

Electrical responses from the skate retina will only follow flicker up to frequencies of 5 hertz when intensities are below rod saturation. At greater luminances, the eye responds to rates as high as 30 hertz. As a result, a plot of critical flicker fusion as a function of intensity is a double branched curve. It seems that prolonged stimulation of skate rods, at high intensities, permits them to change their temporal response characteristics so that they follow high frequencies much as cones do in the duplex retina.

Electrical potentials were recorded from different levels within the skate retina. Comparing the adaptive properties of the various responses revealed that the isolated receptor potential and the S-potential always exhibited similar changes in sensitivity, and that the b-wave and ganglion-cell thresholds acted in concert. However, the two sets of responses behaved differently under certain conditions. For example, a dimly iluminated background that had no measurable effect on the senitivities of either of the distal responses, raised significantly the thresholds of both the b-wave and the ganglion cell responses. In addition, the rate of recovery during the early, "neural" phase of dark adaptation was significantly faster for the receptor and S-potentials than for the b-wave or ganglion cell discharge. These results indicate that there is an adaptive ("network") mechanism in the retina which can influence significantly b-wave and gaglion cell activity and which behaves independently of the receptors and horizontal cells. We conclude that visual adaptation in the skate retina is regulated by a combination of receptoral and network mechanisms.