Search

Using clinical and electrophysiologic measures, we evaluated the visual pathway of patients who had multiple sclerosis, 20/20 Snellen acuity, and no history of optic neuritis. Delayed latencies were found in the transient visual evoked potentials (VEPs) of 38% of the patients, and interocular latency differences were abnormal in 67%. Contrast VEPs were abnormal in 4.6%. Psychophysical determinations of contrast sensitivity were abnormal in 78%. Only 17% of the patients had dyschrornatopsia, 36% had afferent pupillary abnormalities, and 59% had optic nerve pallor or nerve fiber layer loss. Psychophysical contrast evaluations and VEP studies were superior to other clinical evaluations in demonstrating visual dysfunction in these patients.

Focal electroretinograms (FERG), pattern electroretinograms (PERG), and visual evoked potentials (VEP) were studied in a group of 30 aphakic patients with cystoid macular oedema (ACME). When compared with a control group of age-matched aphakics, 35% of patients were found to have abnormal FERG responses and 53%--over half of whom had normal FERG responses--showed abnormal PERG amplitudes. Although most of the patients had associated optic disc leakage, VEP latencies were normal in 26 out of 30. These results may explain the more severe visual loss seen in some ACME patients where the ophthalmologically visible retinal changes do not seem sufficient to explain such reduction in vision.

Purpose: The authors examined electrophysiologic and psychophysical measures of retinal function in patients infected with human immunodeficiency virus (HIV) at different stages of infection, including patients with cytomegalovirus retinitis (CMVR). Methods: All patients had complete ophthalmologic examinations. Rod-mediated psychophysical thresholds were measured using a modified two-color dark-adapted perimetry technique. Rod-dominated full field flash electroretinograms (ERGs) were obtained as a function of flash intensity, followed by cone-dominated ERGs. The 26 patients infected with HIV (26 eyes) were categorized into three groups. Six patients were infected with HIV but had not progressed to acquired immunodeficiency syndrome (AIDS), and 14 had AIDS. Six patients had CMVR with less than 10% of the retina involved. The data were compared with results from age-similar control subjects. Results: Psychophysical thresholds as a function of retinal eccentricity were elevated for each of the three stages of HIV infection. The group of patients with CMVR had the greatest amount of threshold elevation and threshold elevation increased with retinal eccentricity. In addition, all three patient groups had abnormal electroretinographic findings. Patients with CMVR were affected more severely on all measures than were the other HIV-infected groups. Conclusions: Results reveal that a diffuse functional retinal pathology exists in eyes with the funduscopic appearance of localized peripheral CMVR. Additionally, patients infected with HIV, including those without cotton wool spots, may have abnormal retinal function.

Electroretinograms to high-intensity flashes were obtained to determine the extent of rod and cone photoreceptor and postreceptor dysfunction in patients with primary open-angle glaucoma.Full-field flash electroretinograms were obtained using brief high-intensity flashes. Dark-adapted (rod-dominated) and light-adapted (cone-dominated) electroretinogram responses were recorded to a "white" light as a function of flash intensity. The a-wave data were fitted with a model based on photopigment transduction to obtain values for the parameters of log Rmax (the maximum response) and log S (sensitivity). Oscillatory potentials were measured to the cone-dominated high-intensity flashes. Standard clinical 30 Hz flicker electroretinogram responses were recorded using a Grass photostimulator.Analysis of rod and cone a-wave data showed that log Rmax and log S values were within the normal range in nearly all of the patients. For some patients, oscillatory potentials were delayed beyond the normal range.Our results provide little evidence for widespread photoreceptor abnormalities in primary open-angle glaucoma.

The field of electrodiagnostics is rapidly expanding. Improved computing power has expanded our ability to control stimuli and to analyze the biologic signals elicited by them. Similar trends are also affecting other areas ranging from biochemistry and genetics to imaging of the retina and brain. Natural, fertile areas of study are the overlap of these factors. Thus, we had invited papers by Aina Puce and Paul Sieving directed toward structure and function relationships in the cortex and retina. Additionally, we had several sessions related to imaging and electrophysiology.

Estuarine crabs usually show hatching periodicities closely synchronized with tidal, lunar, or solar day periodicities. To define their timing, we monitored hatching activity either directly (by observing females during hatching) or indirectly (by measuring larval densities during nocturnal ebbing tides). Larval densities in the Newport River, at a site (Beaufort) near the ocean, revealed two patterns. Intertidal species (Uca spp., Panopeus herbstii) showed highest densities twice monthly, during the spring tides. Subtidal species (Neopanope spp., three pinnotherids, the blue crab Callinectes sapidus) showed larval densities which, on the average, were similar during all ebbing tides. We speculate upon the selection pressures that may have shaped these differences and propose a hypothesis to explain why the patterns are adaptive. Fiddler crabs were used to determine when, in relation to high tide (HT), hatching occurred. Most larval release in the laboratory and under field conditions occurred within 1 h after HT. To determine what environmental cue might synchronize semimonthly hatching rhythms in fiddler crabs, we compared the timing of larval release at two local sites where tidal amplitude pattern was identical but HT time differed each night by an average of 1.92 h. The results suggested that fiddler crabs respond to tidal amplitude and not the time interval between HT and the onset of darkness.