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Biomedical subjects

S G Jacobson

Publications and source records attributed to S G Jacobson.

At least 109 records · Page 6Linked to original sources
PubMed1991

Relatively enhanced S cone function in the Goldmann-Favre syndrome.

Using electrophysiologic and psychophysical tests that measure rod, midspectral, and S (blue) cone function, we studied four patients with the Goldmann-Favre syndrome, an autosomal recessive vitreoretinal degeneration. With spectral electroretinography, the predominant signal was from the S cones. With dark-adapted perimetry, all patients had severely reduced rod sensitivities and subnormal midspectral cone sensitivities. With S cone perimetry, the patients had normal or subnormal S cone function. Sensitivity differences between S and midspectral cones were significantly different from normal; there was relatively higher sensitivity to S cones compared to midspectral cones throughout the visual field. This relationship of dysfunctional cone mechanisms in the Goldmann-Favre syndrome is similar to that in the enhanced S cone syndrome, a recently identified retinal degeneration with S cone hypersensitivity. The results suggest that the Goldmann-Favre and the enhanced S cone syndromes are linked by a common pattern of retinal dysfunction.

Adult↗
PubMed1991

The distribution and kinetics of visual pigments in the owl monkey retina.

An imaging fundus reflectometer has been used to study the distribution and regeneration of visual pigments in the retina of the owl monkey, Aotes trivirgatus. Measurements were made over an area of retina from 10 degrees nasal to 30 degrees temporal on the horizontal meridian, and from 5 degrees inferior to 30 degrees superior on the vertical meridian. The measured density differences vary with retinal location, with values in the central retina higher than those in more peripheral regions. The area of high density differences is roughly circular, with the highest values (approximately 0.3 log units) centred on or near the area centralis. Spectral measurements are consistent with a rod visual pigment absorbing maximally at about 518 nm, and indicate that the contribution of cone pigments to the imaging fundus reflectometer (IFR) data is negligible everywhere within the retinal area studied. The distribution of density differences is shown to correlate well with anatomical data for receptor and ganglion cell populations. Bleaching the visual pigment with brief intense lights leads to the extensive formation of the long-lived photoproduct metarhodopsin 3. Complete regeneration of rhodopsin following a full bleaching exposure (whether of brief or extended duration) takes more than 60 min and the time course of its recovery cannot be described accurately by first order kinetics.

Animals↗
PubMed1990

Diagnostic clinical findings of a new syndrome with night blindness, maculopathy, and enhanced S cone sensitivity.

We studied eight patients who had night blindness, maculopathy (often cystoid), degenerative changes in the region of the vascular arcades, relatively mild visual field loss, and an unusual but characteristic electroretinogram. The dark-adapted electroretinogram showed no response to low-intensity stimuli that normally activate the rods, but large, slow responses to high-intensity stimuli. These large, slow waveforms persisted without change under light adaptation, and showed a striking mismatch to photopically balanced short and long wavelength stimuli (with sensitivity much greater to short than long wave-lengths). Since there is evidence from other studies that the electroretinogram and psychophysical responses represent hypersensitivity of short wavelength-sensitive (S or blue) cones, we propose that this disorder be called the enhanced S cone syndrome. There can be different degrees of severity in this syndrome, and progression appears to be slow.

Adolescent↗
PubMed1990

Patterns of rod and cone dysfunction in Bardet-Biedl syndrome.

We studied visual function in 16 patients with the Bardet-Biedl syndrome. Visual acuity, kinetic perimetry, and electroretinography results indicated a severe loss of central and peripheral vision and rod and cone function by the second or third decade of life. Light- and dark-adapted static perimetry in patients 10 to 15 years of age with early involvement showed a parallel and marked loss of rod and cone sensitivity across the visual field. Patients with more advanced disease and no measurable peripheral visual field showed different patterns of central visual dysfunction: an island of only cone function centered in a bull's-eye lesion; patches of rod function surrounding geographic atrophy; or a central island of excellent rod sensitivity but severely impaired cones. In the two least-affected patients, a 13-year-old boy and the asymptomatic 45-year-old sibling of a patient, there were more rod than cone abnormalities as determined by electroretinography and static perimetry.

Adolescent↗
PubMed1990

Photoreceptor rosettes with blue cone opsin immunoreactivity in retinitis pigmentosa.

Immunocytochemistry has rarely been performed on donor retinas from patients with retinitis pigmentosa (RP), due to routine storage of tissues in fixatives that reduce or destroy antigenicity. The authors have developed a method to circumvent this problem and report light and electron microscopic histopathology and immunocytochemistry of an unusual retina from a 76-year-old man with multiplex RP. The retina shows loss of photoreceptors throughout (particularly rods), shortened foveal cone outer segments, and displaced photoreceptors in rosettes and tubules, an atypical pattern for RP. Antigenicity was recovered in this retina by treatment with sodium borohydride, and 17 antigens normally found in retina are present with expected distribution, although many cells have abnormal morphology. Most cone outer segments are immunoreactive with anti-blue but not anti-red/green cone opsin, whereas blue cone sensitivity is preferentially lost in many cases of RP. Psychophysical testing of the patient's sister, who has the same retinal disease, showed reduced rod and red/green cone sensitivities. This was consistent with the diminished numbers and size of rods and red/green cones found by immunocytochemistry in her brother's retina. The sister did not show blue cone hypersensitivity characteristic of a recently described retinal degeneration known as the "enhanced S cone syndrome."

Aged↗
PubMed1990

[Modification of an automated perimeter for dark- and light-adapted perimetry].

A modified automated projection static perimeter which can measure thresholds with lights of three different wavelengths in light-adapted as well as in dark adapted state is described. With the modifications described, this instrument can evaluate relative states of rod and cone mechanisms respectively within the visual field range of 72 degrees. These modifications also enable dark-adapted two-color static perimetry quantitatively across the visual field including profile measurement. Results obtained from normal subjects with these techniques permit assessment of the sensitivity in dark and light and also determination of photoreceptor mediation in the dark. These techniques can evaluate rod and cone dysfunctions separately unlike other retinal function tests, and may show that different mechanisms even in one clinical entity of retinal dystrophies, as well as retinal degenerations, can be demonstrated.

Adaptation, Ocular↗
PubMed1990

SWS (blue) cone hypersensitivity in a newly identified retinal degeneration.

Photoreceptor-mediated mechanisms were studied in patients with a recently identified retinopathy typified by night blindness, cystoid maculopathy, and similar scotopic and photopic electroretinograms (ERGs). Dark-adapted spectral sensitivity functions were only partly explained as composites of rod and cone curves shifted to lower sensitivities; there was unusually high sensitivity from 400-460 nm. A rod mechanism, reduced in sensitivity by at least 3 log units, was detectable with dark adaptometry. No measurable rhodopsin was found with fundus reflectometry. Light-adapted spectral sensitivities were subnormal for wavelengths greater than 500 nm but supernormal from 420-460 nm. On a yellow adapting field, the supernormal spectrum approximated that of the short-wavelength-sensitive (SWS) cone system. With spectral ERGs, two mechanisms were demonstrated. Dark- and light-adapted ERGs to green, orange-yellow, and red stimuli had similar waveforms and coincident intensity-response functions on a photopic intensity axis. ERGs to blue and blue-green stimuli were similar, and intensity-response functions coincided on a SWS cone intensity axis. Patients varied in the degree to which rod and midspectral cone function were decreased and SWS cone function was increased.

Adolescent↗
PubMed1989

Cone-rod dystrophy. Phenotypic diversity by retinal function testing.

Three patterns of visual dysfunction were identified in patients with autosomal recessive or simplex cone-rod dystrophy using rod and cone electroretinography and light- and dark-adapted static threshold perimetry. In the first pattern, there was a central rod and cone scotoma with eccentric fixation, mild peripheral retinal dysfunction equally affecting rod and cone systems, and slow progression. The second pattern, which was relatively more severe, also showed a central rod and cone scotoma and eccentric fixation; however, there was more cone than rod dysfunction detected by electroretinography, and function was lost in the peripheral visual field before it was lost in the midperipheral field. A third pattern, which was rapidly progressive, showed central unsteady fixation and no measurable cone function. Patches of rod function were retained in the central and inferotemporal regions of the visual field. Most of the patients studied fit within the three patterns and the patterns were consistent within families.

Adolescent↗
PubMed1989

Evaluation of eyes with stage-5 retinopathy of prematurity.

Recent advances in vitreous microsurgical techniques described by Machemer, Charles, Hirose, Trese, de Juan, and others have resulted in successful anatomical reattachment of eyes with stage-5 retinopathy of prematurity (ROP). Such eyes had previously been classified as inoperable. Although nearly 50% of eyes achieve an anatomical reattachment of the posterior retina, from 10% to 30% of the reattached eyes reported to date have no light perception. Infants with stage-5 ROP in both eyes may be quite difficult to evaluate preoperatively, particularly with regard to visual function and the configuration of the retinal detachment. Protocols for obtaining a bright flash visually evoked potential (VEP) and standardized echography have been developed to determine the following: 1. Objective evidence of visual function in one or both eyes 2. The configuration and characteristics of the retinal detachment It is hoped that such prospective evaluation will help to identify those eyes with the best prognosis for both visual anatomical success.

Evoked Potentials, Visual↗
PubMed1989

Interocular asymmetry of visual function in heterozygotes of X-linked retinitis pigmentosa.

Heterozygotes of X-linked retinitis pigmentosa were studied with full field rod and cone electroretinography and light adapted kinetic perimetry. Twelve parameters from the electroretinograms (ERGs) and two parameters from the kinetic visual fields of both eyes of 22 heterozygotes were measured and statistical comparisons made with results from female control subjects. Rod and cone ERG amplitude parameters were significantly lower and cone timing delayed in the heterozygotes. Most of the ERG parameters that were abnormal in measured value also showed significantly greater interocular differences compared with controls. Kinetic visual fields with both V-4e and I-4e test targets were smaller in heterozygotes than in controls. Only with the I-4e target, however, were interocular differences significantly larger in the heterozygotes. For the I-4e target and many of the ERG parameters, using the interocular difference in conjunction with the measured parameter value from a single eye significantly increased the efficacy of discrimination between heterozygotes and controls; for some ERG parameters, the interocular difference alone provided the best separation of the two groups.

Adolescent↗
PubMed1989

Rhodopsin levels and retinal function in cats during recovery from vitamin A deficiency.

Extended vitamin A deficiency in the cat led to an abnormal appearance in the tapetal fundus with the formation of a dark brown streak centered on the area centralis. At this time rod sensitivity, as measured by the b-wave of the electroretinogram, was reduced by more than two log units; the level of rod visual pigment was reduced by about 90% throughout the paracentral retinal region and was essentially absent from the area centralis. Following oral supplementation with vitamin A there was a rapid partial recovery of both rhodopsin levels and rod sensitivity. Further recovery continued over more than 18 days to levels that were not substantially below normal. This recovery was absent from the area centralis, in which measured visual pigment levels remained very low. In supplemented cats, the brown color in the fundus faded but there remained a small hyper-reflective zone at the area centralis. Morphological examination of the central retina in a supplemented cat showed an outer nuclear layer reduced to one or two rows in the small zone with low rhodopsin levels. Cone but not rod photoreceptors were present in this zone and they appeared to lack outer segments. During recovery, the increase in rod sensitivity was approximately linearly related to the recovery of rhodopsin levels. Thus, in these conditions reduction in sensitivity resulting from previous vitamin A deficiency was limited by the ability of the photoreceptors to absorb incident quanta. The time course of the recovery of rhodopsin and sensitivity suggests that at least two processes were involved. The faster of these may be the regeneration of rhodopsin from existing opsin molecules in the outer segments, while the slower may depend on the renewal of the outer segments themselves.

Animals↗
PubMed1989

Rhodopsin levels and rod-mediated function in Abyssinian cats with hereditary retinal degeneration.

Abyssinian cats with different stages of a slowly progressive autosomal recessively-inherited retinal degeneration were studied with imaging fundus reflectometry (IFR) and electroretinography (ERG). Maps of the visual pigment distribution were made in an area of retina extending from the posterior pole to the midperiphery. Rhodopsin levels in the midperipheral retina of a 6-month-old affected cat (stage of suspected disease) were reduced about 20% relative to the mean normal value. The same cat, tested at 2.5 yr of age (now moderately advanced stage), showed a 60% reduction. A 3-yr-old affected cat (also moderately advanced) had a reduction in rhodopsin of about 60%. There was no measurable rhodopsin in a 7-yr-old affected cat (advanced stage). Rhodopsin regeneration kinetics at the different stages of disease were found to be similar to those of normal cats. The rod ERG b-wave threshold in the 6-month-old cat was elevated by 0.26 log units; at 2.5 yr of age, the threshold was elevated by 0.48 log units. A 0.34 log units threshold elevation was found in the 3-yr-old cat. There was no detectable ERG in the 7-yr-old cat. The relationship between the rod ERG threshold elevations and the rhodopsin levels was close to that expected if the dysfunction was caused by decreased quantal absorption.

Animals↗
PubMed1989

The spectral reflectance of the nerve fiber layer of the macaque retina.

This paper reports the first quantitative measurements of the reflectance spectrum of the nerve fiber layer (NFL) of the retina. An arcuate defect in the NFL of two macaque monkeys was produced by photocoagulating a small spot near the optic disc. Imaging fundus reflectometry at 8 wavelengths was then used to measure the fundal reflectances in the defect and in the intact NFL. The reflectance of the NFL alone was determined by subtracting the reflectance of the bare fundus in the defect from the reflectance of the adjoining fundus with intact NFL. The reflectance data were corrected for the transmission of the ocular media with published values of the density of monkey cornea and lens. Lens absorption was measured from Purkinje images and differed little from the published values. The NFL reflectance can be characterized by a spectrum that has the same shape at all points along an arcuate region of the NFL but decreases in absolute reflectance as the thickness of the NFL decreases. The reflectance changes little between 680 and 560 nm, but rises as lambda-n from 560 to 460 nm, where n = 2.5-3.1. The data reported here begin to provide a quantitative understanding of empirically determined methods for enhancing the visibility of the NFL and have implications for retinal densitometry.

Animals↗
PubMed1988

Rod and cone psychophysics and electroretinography: methods for comparison in retinal degenerations.

Methods have been developed to compare full field rod and cone electroretinograms with results of rod and cone static perimetric measurements across the visual field. In a limited number of patients with retinal degeneration, including two subtypes of retinitis pigmentosa, there were close relationships between electroretinographic and psychophysical parameters. Maximum b-wave amplitude and visual field area were highly correlated, as were electroretinographic and perimetric measures of sensitivity loss. Future application of the methods to large numbers of patients with typical retinitis pigmentosa may help elucidate different mechanisms of retinal degeneration.

Adult↗
PubMed1988

Visual function and rhodopsin levels in humans with vitamin A deficiency.

Details of rod and cone dysfunction in vitamin A deficiency have been studied in two subjects with primary biliary cirrhosis and one with Crohn's disease, all of whom presented with symptoms of night blindness. Visual function in the mid-peripheral retina was monitored with two-color adaptometry and rhodopsin levels were measured by fundus reflectometry. Initially all three subjects had no measurable rod function and delayed cone adaptation. In one case the dark-adapted cone threshold was also elevated. Oral supplementation with vitamin A restored visual function to normal within 8 days in all subjects. During supplementation, cone function was restored more rapidly than that of rods, though the pattern of recovery was similar for each receptor type. Final thresholds improved first, though the rates at which they were reached were abnormally slow. As recovery continued, adaptation kinetics returned to normal. When rod adaptation was delayed, the regeneration of rhodopsin was also abnormally slow. When rod final threshold was 2 log units higher than normal, rhodopsin regeneration was incomplete, reaching about 70% of the normal level. The initial stages of visual dysfunction during onset of vitamin A deficiency were studied in one subject, and were found to mirror the pattern seen during recovery: rod adaptation was initially slower than normal, but reached completion. Cone adaptation remained normal until rod function was almost absent.

Adult↗
PubMed1988

Morphological findings in retinitis pigmentosa with early diffuse rod dysfunction.

The retina from the postmortem donor eye of a 64-year-old man with advanced autosomal dominant retinitis pigmentosa (RP) was studied with light and electron microscopy. Two children of the donor were tested with two-color, dark-adapted static perimetry and found to have Type 1 or D-type RP, the psychophysical subtype with early onset of severe rod dysfunction diffusely affecting the entire retina. In the macula of the donor retina, rods and cones were clustered in irregularly shaped patches, in association with pigmented retinal pigmented epithelial cells. Only cones in the middle of these patches possessed outer segments, and these were poorly organized. Of the few photoreceptors remaining outside of the macula, those in the superior retina had well-formed terminals and appeared to be rods. Rods were also observed superior to the disk and in the temporal mid-periphery. The few photoreceptors remaining in the inferior retina were also rod-like, but had less well-formed terminals. The retinal pigmented epithelium was relatively normal near surviving photoreceptors, but was depigmented, had thinned, or was absent in regions of photoreceptor dropout. These findings represent the first reported morphology of the retina from an eye donor with known psychophysical subtype of RP.

Adult↗