Clinical and subclinical ophthalmic findings with retinol deficiency.

BACKGROUND: Patients at risk for retinol deficiency in developed countries include those with hepatic dysfunction and malabsorption states. Symptoms of retinol deficiency may go unrecognized or unreported. METHODS: The authors describe 15 patients with hepatic dysfunction, two of whom had procedures that would predispose to malabsorption and were ophthalmologically symptomatic of retinol depletion. The other 13 patients were ophthalmologically asymptomatic liver transplant candidates examined prospectively for subclinical evidence of retinol deficiency. Combined laboratory analysis, Schirmer's testing, conjunctival impression cytology, and electroretinography were performed. RESULTS: Twelve of 15 patients had serum retinol levels below the lower limit of normal. Aqueous tear production was reduced in 7 of 14 patients. Abnormal conjunctival morphology was noted in 6 of 12 patients. Electroretinograms were abnormal in the two patients who were visually symptomatic and in seven of nine patients who were ophthalmologically asymptomatic. CONCLUSION: Subclinical, physiologically significant retinol deficiency may be a frequent and unrecognized problem among patients with hepatic dysfunction.

Digoxin toxicity. Recognizing the varied visual presentations.

We report three cases of digoxin toxicity presenting with decreased visual acuity, unaccompanied by the classic visual symptom of xanthopsia. Visual function improved and symptoms diminished upon lowering of blood digoxin level. Electroretinographic (ERG) abnormalities in the first case were suggestive of a cone deficit, which supports recent electrodiagnostic and labeled tracer studies implicating retinal dysfunction in the pathogenesis of digoxin toxicity. The second patient presented with visual symptoms exclusively. Evaluation of the third case was hampered by advanced retinitis pigmentosa and the presentation was complicated by a syncopal episode. Digoxin toxicity is a potentially life-threatening condition. Ophthalmologists and neurologists may be the first physicians consulted. It must be considered in the differential diagnosis in patients with otherwise unexplained visual loss.

Profound papilledema due to cryptococcal meningitis in acquired immunodeficiency syndrome: successful treatment with fluconazole.

Although cryptococcal meningitis is a frequent infection in patients with AIDS, papilledema is rarely reported. We have reported a case of profound papilledema associated with cryptococcal meningitis in a patient with AIDS. After treatment failure with amphotericin B, the patient was successfully treated with fluconazole, and the papilledema resolved.

Response properties of horizontal cells and photoreceptor cells in the retina of the tree squirrel, Sciurus carolinensis.

A new experimental preparation for intracellular recording from mammalian retinal neurons has been established. This is the arterially perfused eyecup preparation of the tree squirrel, Sciurus carolinensis. Two horizontal cell types have been recorded in this preparation. These cell types differ in their response waveforms. Type 1 horizontal cells appear to receive input only from cones, whereas type 2 horizontal cells receive mixed rod-cone input. Sciurus horizontal cells have receptive-field sizes smaller than those of horizontal cells in other mammalian and nonmammalian species. Recordings from a second class of cells in the outer retina of the squirrel reveal receptive-field properties considerably different from those of squirrel horizontal cells and similar to those of photoreceptor cells in other species. On the basis of these receptive-field properties, recording depth, and spectral response characteristics, we conclude that these recordings were from cone-photoreceptor cells. These recordings from squirrel cones are the first demonstration of mammalian photoreceptor response amplitudes and receptive-field interactions comparable with those demonstrated for nonmammalian species.

The arterially perfused eyecup of the tree squirrel, Sciurus carolinensis: a preparation for intracellular recording from mammalian retinal neurons.

The arterially perfused eyecup of the Eastern gray squirrel, Sciurus carolinensis, has been developed for the study of mammalian retinal neurons by the technique of intracellular recording. Particular emphasis is placed in this report on the development of a convenient perfusion chamber. The choice of this animal and the reason for choosing the arterially perfused open eyecup are also discussed. Intracellular recordings were made from all major types of neurons in the squirrel retina. Data are presented here from ganglion cells and bipolar cells.

Horizontal cells of the turtle retina. I. Light microscopy of Golgi preparations.

In Golgi preparations of turtle retina, four types of horizontal cells were observed and their morphological characteristics determined in vertical thick sections, whole mount preparations, and reconstructions from serial 1-micrometer sections. H1 consists of a nucleated, stellate cell body (H1CB) and an irregular, tuberous axon terminal (H1AT) connected by a slender axon. Both parts of these cells make contact with receptor cells. H1CB's appear to correspond to "L2-type cells" while H1AT's correspond to "L1-type cells" described in the physiological literature. H2 and H3 are axonless stellate cells which are similar to one another in vertical profile and may occasionally appear similar in horizontal view. In general, the dendritic tree is more densely branched and the density of receptor cell contacts is higher for H2 than for H3. H2-type cells may correspond to "R/G C-type cells." H4 is also an axonless stellate cell type which is smaller than H2 or H3 at equivalent retinal locations. The dendritic fields of H1CB's vary widely, but systematically, in size and shape over the retina. Their size is inversely related to receptor cell density, and the shape of the dendritic tree varies from roughly circular in the central area to elliptical in the periphery of the retina.

Horizontal cells of the turtle retina. II. Analysis of interconnections between photoreceptor cells and horizontal cells by light microscopy.

Criteria were established whereby the chief and accessory members of double cones, red-, green-, and blue-sensitive single cones, and rods could be distinguished from one another in 1-micrometer sections through the retinas of Pseudemys scripta elegans and Chelydra serpentina. Criteria included the presence of absence of an oil droplet, the size, color, and radial position of the oil droplet, the size and shape of the inner and outer segments, and the shape orientation of the connection between the perikaryon and synaptic terminal of each receptor cell. Using these criteria, the color-specific interconnections between horizontal cells and receptor cells were analyzed using 1-micrometer serial sections through Golgi-stained examples of horizontal cells of each type. The results of this analysis are: (a) H1 cells bodies contact both the red- and green-sensitive members of double cones, as well as red- and green-sensitive single cones. (b) H1 axon terminals contact only the red-sensitive chief members of double cones, red-sensitive single cones, and rods. (c) H2-type cells contact only green- and blue-sensitive single cones. (d) H3-type cells contact only blue-sensitive single cones. (e) H4-type cells contact only the green-sensitive accessory members of double cones. With the exception of H1 cell bodies, all horizontal cells generally contacted every appropriate receptor cell type within their receptive field. A model for the generation of complex horizontal cell light responses is proposed and discussed.

Goldfish retina: functional polarization of cone horizontal cell dendrites and synapses.

In serial electron micrographs we observed that dendrites of goldfish cone horizontal cells are either central or lateral in ribbon synaptic triads, depending on cone and horizontal cell type. The chromatic properties of cone horizontal cell responses may be explained if the cone horizontal cells act as interneurons, receiving from cones through their central processes but acting on cones through their lateral processes.