The separation of parallel visual systems by disease processes.
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Animals↗
Biomedical subjects
G B Arden
Publications and source records attributed to G B Arden.
Selective magnocellular damage in melanoma-associated retinopathy: comparison with congenital stationary nightblindness.
Psychophysical methods for isolating and evaluating the function of specific neural pathways are used to characterize the visual losses in patients with melanoma-associated retinopathy (MAR). These are compared with those of congenital stationary nightblindness (CSNB), a condition which displays a similar grossly abnormal ERG and loss of rod function. In MAR patients achromatic contrast sensitivity was greatly reduced in the low spatial frequency range. Stimuli chosen to isolate the magnocellular pathway were seen badly, whereas stimuli signalled primarily by the midget of the parvocellular pathway (isoluminant red/green or achromatic high spatial frequencies) were seen normally. This selective loss was not found in patients with CSNB. In MAR there is a selective loss of function subserved by magnocellular cells coupled with preservation of function subserved by the midget type 1 parvocellular cells.
Adult↗
Visual field loss following vitrectomy for stage 2 and 3 macular holes.
AIM: To describe the phenomenon of peripheral field loss following routine pars plana vitrectomy for stage 2 and 3 full thickness macular hole and to investigate the underlying mechanism. METHODS: Five patients, who reported peripheral field defects after apparently uncomplicated vitrectomy, posterior cortical vitreous peeling, and perfluoropropane (C3F8) gas tamponade, were studied retrospectively with slit-lamp biomicroscopy, automated and kinetic perimetry, fundal fluorescein angiography, focal electroretinography (ERG), and colour contrast sensitivity (CCS) testing. RESULTS: All five patients, who were between 50 and 73 years of age, reported an inferotemporal field defect following resolution of the intraocular gas bubble. In all eyes, the scotomata encroached to within 20 degrees to 30 degrees of fixation and to within 5 degrees to 15 degrees of the blind spot. In one eye, a partial altitudinal component was evident. All scotomata subsequently remained stable and three eyes developed subtle segmental nasal disc pallor and nerve fibre loss corresponding to the field defect. CCS testing revealed absent colour contrast in the scotomatous area, in the presence of a preserved focal quadrantic flash ERG, compared with normal CCS protan thresholds and focal ERGs in unaffected quadrants, indicating preserved outer retinal function in the area of the scotoma. CONCLUSIONS: These observations support the hypothesis that field defects occur as a result of retinal nerve fibre layer damage. It is proposed, on the basis of intraoperative observations and other evidence, that the most likely site of nerve fibre damage is at the nasal portion of the optic nerve rim or peripapillary retina, probably due to traction during cortical vitreous peeling.
Aged↗
Chromosome 19q cone-rod retinal dystrophy. Ocular phenotype.
OBJECTIVE: To describe the phenotype in a family with dominantly inherited cone-rod dystrophy with chromosome assignment to a 19q locus, and to correlate this with current classifications of this retinal dystrophy. DESIGN: A detailed clinical examination including Goldmann perimetry was undertaken in all family members. Six members under the age of 30 years underwent dark-adapted electroretinography, color contrast-sensitivity measurement, dark-adapted static perimetry, and dark adaptometry. PATIENTS: The study included 34 affected and 22 unaffected patients in four generations of a pedigree that manifested autosomal dominant cone-rod retinal dystrophy linked to a chromosome 19q locus by genetic linkage analysis. RESULTS: Loss of visual acuity occurred in the first decade of life, onset of night blindness occurred after 20 years of age, and little visual function remained after the age of 50 years. Central and, later, peripheral retinal fundus changes were associated with central scotoma, pseudoaltitudinal field defects, and finally global loss of function. Psychophysical and electrophysiologic testing before the age of 26 years showed more marked loss of cone than rod function. CONCLUSIONS: The phenotype associated with this mutation does not fit well into previous subtypes of cone-rod dystrophy. Further studies will be needed to correlate specific genetic mutations in this group of conditions with the various clinical phenotypes.
Adolescent↗
Autosomal dominant pattern dystrophy of the retina associated with a 4-base pair insertion at codon 140 in the peripherin/RDS gene.
OBJECTIVE: To define the phenotype of a retinal dystrophy associated with a 4-base pair insertion at codon 140 of the peripherin/RDS gene. PATIENTS: Six affected members spanning two generations of a single family were examined. Five were studied in detail electrophysiologically and psychophysically. METHODS: Psychophysical testing included color vision testing, photopic and scotopic static threshold perimetry, and dark adaptometry. Electrophysiological testing included flash and pattern electroretinography, as well as electrooculography. RESULTS: Clinical findings ranged from subtle pigmentary changes at the level of the retinal pigment epithelium to more widespread pigmentary changes associated with choroidal neovascularization. Those with severe fundus changes exhibited greater abnormalities in psychophysical and electrophysiological testing than those with minimal fundus changes. CONCLUSIONS: This particular peripherin/RDS gene mutation is associated with dominantly inherited pattern dystrophy of the retina. The phenotypic expression is variable in a manner not explained by age.
Aged↗
Does occupational exposure to argon laser radiation decrease colour contrast sensitivity in UK ophthalmologists?
The objects of the study were to determine: (1) whether United Kingdom ophthalmologists who used argon lasers had the elevation of colour-contrast thresholds previously discovered and (2) whether other users of argon lasers showed any unusual loss of colour vision. A total of 1072 UK ophthalmologists filled in a questionnaire about their professional use of lasers, the length of time spent operating, and their out-of-doors activities. Their colour vision was then tested by a new sensitive system, and if any abnormality was detected, a clinical eye examination was performed. The results were as follows: (1) Colour vision testing was shown to be reliable. Any self-selection bias was excluded. Test-retest variability was small. Normal results did not change during the survey. (2) A number of men with high red-green thresholds were discovered. Some were aware of their congenital insensitivity. The frequency of all such defects was less than the known incidence of congenital colour deficiency in the male population. (3) Additionally a number of high tritan (blue-yellow) thresholds were encountered, some associated with reported diabetes and hypertension. In other cases of this type, undetected or unacknowledged systemic disease may be present. (4) After making allowance for all these incidental causes of loss of colour vision, and for the effect of age on colour vision (which is very small) only four of the sample were > 2 SD above normal. (5) However, the average blue-yellow thresholds of ophthalmologists were slightly and highly significantly raised compared with normal, in the first year of the survey. During the second and third years, the mean thresholds declined to normal. Similar but less significant findings were found for protan thresholds. It is concluded that the enhanced safety precautions recently introduced are associated with a recovery of colour vision in this population, demonstrating that any changes to individuals were reversible. Colour vision screening has proved able to detect mild ocular abnormalities due to systemic and congenital disease.
Adult↗
Quadrant analysis of peripheral colour contrast thresholds can be of significant value in the interpretation of minor visual field alterations in glaucoma suspects.
Peripheral colour contrast thresholds were investigated in glaucoma suspects with no or minor visual field alterations, determining the average colour contrast threshold at 12.5 degrees off axis. The technique was introduced as a rapid screening test for pre-glaucomatous visual loss. Using this 'ring' test, all definite glaucoma patients in the initial study had elevated colour contrast thresholds. In our experience, however, a substantial proportion of early glaucoma patients were found to have normal thresholds. The peripheral colour contrast threshold determined by the ring test is an average threshold in the entire annular zone at 12.5 degrees eccentricity. We therefore modified the test procedure without a major increase in test duration. An arcade subtending 45 degrees at 12.5 degrees eccentricity was used to determine colour contrast thresholds in four quadrants of the visual field separately ('quadrant' test). We present here the first results of this novel procedure, investigating peripheral colour contrast thresholds in glaucomatous patients. The quadrant test is shown to be more sensitive than the ring test in the detection of functional loss.
Adult↗
Autosomal dominant retinitis pigmentosa mapping to chromosome 7p exhibits variable expression.
The genetic locus causing autosomal dominant retinitis pigmentosa (adRP) has recently been mapped in a large English family to chromosome 7p. Eight affected members of this family were studied electrophysiologically and psychophysically with dark adapted static threshold perimetry and dark adaptometry. The phenotypes observed fell into three categories: minimally affected with no symptoms, and normal (or near normal) electrophysiology and psychophysics; moderately affected with mild symptoms, abnormal electroretinograms, and equal loss of rod and cone function in affected areas of the retina; and severely affected with extinguished electroretinograms and barely detectable dark adapted static threshold sensitivities. The mutation in the gene on 7p causing adRP in this family causes regional retinal dysfunction with greatly variable expressivity ranging from normal to profoundly abnormal in a manner not explained by age.
Adult↗
Pattern electroretinogram and peripheral colour contrast thresholds in ocular hypertension and glaucoma: comparison and correlation of results.
AIMS: Both pattern electroretinogram and peripheral colour contrast thresholds have been shown to be abnormal in glaucoma and ocular hypertension. This study evaluates each of these tests as tools for the early diagnosis of glaucoma, compares and contrasts the results, and examines the relation between the two tests in a large cohort of ocular hypertensive patients. METHODS: Transient and steady state pattern electroretinograms and peripheral colour contrast thresholds were performed in 45 normal, 37 glaucomatous, and 206 ocular hypertensive eyes. The results were analysed using receiver operating characteristic curves, together with evaluation of sensitivity and specificity of the tests. The relation between the two tests was examined by direct statistical correlation of the results. RESULTS: All tests showed high sensitivity and specificity for discriminating between normal and glaucomatous eyes. However, there was a significant difference between the two tests for the number of ocular hypertensives considered as abnormal. Forty per cent of ocular hypertensives had abnormal pattern electroretinogram compared with 30% with abnormal peripheral colour vision. Peripheral colour contrast thresholds showed a significant correlation with both transient and steady state pattern electroretinogram. CONCLUSION: Both of these tests have been shown to be promising new tools for the early detection of glaucoma but the number of ocular hypertensive patients showing abnormal results is rather higher than expected considering the natural history of the condition. Sensitivity in ocular hypertension may be increased by using a combination of both tests. The significant correlation between these psychophysical and electrophysiological tests is discussed.
Aged↗
Bimodal expressivity in dominant retinitis pigmentosa genetically linked to chromosome 19q.
A clinical, psychophysical, and electrophysiologic study was undertaken of two autosomal dominant retinitis pigmentosa pedigrees with a genetic mutation assigned to chromosome 19q by linkage analysis. Members with the abnormal haplotype were either symptomatic with adolescent onset nyctalopia, restricted visual fields, and non-detectable electroretinographic responses by 30 years of age, or asymptomatic with normal fundus appearance and minimal or no psychophysical or electroretinographic abnormalities. There was no correlation in the severity in parents and their offspring. Pedigree analysis suggested that although the offspring of parents with the genetic mutation were at 50% risk of having the genetic defect, the risk of being symptomatic during a working lifetime was only 31%. Such bimodal phenotypic expressivity in these particular pedigrees may be explained by a second, allelic genetic influence and may be a phenomenon unique to this genetic locus. Genetic counselling in families expressing this phenotype can only be based on haplotype analysis since clinical investigations, even in the most elderly, would not preclude the presence of the mutant gene.
Adult↗
Colour contrast sensitivity in patients with age-related Bruch's membrane changes.
Patients with bilateral drusen as a manifestation of early age-related macular degeneration (AMD) may have minor psychophysically detectable visual defects in the presence of normal visual acuity. In a variety of retinal diseases, one of the earliest changes in visual processing is an impairment of normal colour vision. This study was undertaken to evaluate colour vision deficits in patients with macular drusen and to determine whether changes in colour contrast sensitivity may occur over time. In a prospective study, colour vision in 84 eyes of 84 patients aged 55-84 years (mean, 68.89 +/- 6.23 years) with macular drusen and clear media was tested using a computer graphics technique. A total of 47 patients were reviewed annually for up to 2 years and measurements were obtained at annual intervals. Colour contrasts sensitivity along protan, deutan and tritan colour confusion lines was determined at a foveal and a parafoveal region. The sensitivity to all stimuli showed large variations between patients. The thresholds for foveal blue-colour contrast sensitivity were elevated and increased during the review period. In contrast, there was no significant change in sensitivity with time for red and green at the foveal or parafoveal region. Tritan threshold changes suggest that the SW cone-receptor population is more susceptible to damage associated with early age-related macular disease than are red or green cones. The results indicate that blue colour contrast sensitivity determined over time may serve as a measure to assess the progression of age-related maculopathy prior to the manifestation of atrophic or exudative macular lesions associated with visual loss.
Aged↗
Color contrast sensitivity and pattern electroretinographic findings after diode and argon laser photocoagulation in diabetic retinopathy.
The retinal depth at which photocoagulation is maximal varies with wavelength. We compared visual function of eyes undergoing photocoagulation by the near-infrared diode laser to the argon green laser. We treated 14 patients with diabetic retinopathy requiring bilateral panretinal photocoagulation with the diode laser on the right eye and the argon system on the left eye. Before and after treatment visual acuity, central and peripheral color contrast sensitivity, and pattern electroretinograms were recorded. No difference was noted in the clinical response or visual acuity outcome, but a tendency was observed for less decline in color contrast sensitivity and pattern electroretinogram recordings after diode laser photocoagulation. Although P values (.05 to .5) did not reach significance, a mean of 8.4 of 14 patients per test had better test results after diode laser treatment. Diode laser photocoagulation seems to be a viable alternative to argon laser treatment and may be a more gentle mode of treatment.
Adult↗
Visual thresholds to low-contrast pattern displacement, color contrast, and luminance contrast stimuli in Parkinson's disease.
We used the computerized Moorfield Vision System to demonstrate specific increases in various perceptual visual thresholds in idiopathic Parkinson's syndrome. Fifteen patients were compared to 13 age-matched normals. Motion detection was impaired maximally (2 p < 0.01 and better in two-tailed t test) at luminance contrasts of 3-7%. Stimulus was an achromatic vertical 4 cycles/degrees sine wave grating subtending 3 degrees x 2 degrees, centered 5 degrees in the nasal field and oscillating at 5 Hz. In addition, stationary color and luminance contrast thresholds were tested with flashed display of 5 degrees x 6 degrees random letters, which were presented for 200 ms (color) and 50 ms (achromatic). Color discrimination was impaired in the tritan axis only (2 p < 0.05 in two-tailed t test). All achromatic stimuli--luminance increments, decrements, and phase reversing stimuli--were equally well seen by patients and controls. We conclude that the dopaminergic deficit of retinal amacrine cells in Parkinson patients can be monitored by combined low-contrast and motion (displacement) stimuli. Future studies will determine if moving colored targets are more effective in discriminating patients from controls than are the achromatic gratings used in this work.
Aged↗
Gold foil electrodes: a two-center study of electrode reliability.
Using the routine techniques employed at our two centers for recording pattern electroretinograms and a variety of methods, we investigated the reliability of the gold foil electrode over repeated uses. We found no significant difference between the pattern electroretinograms recorded with new electrodes and those that had had such extensive use in patients that they were believed unsuitable for further clinical use. We therefore continue to recommend the gold foil electrode for repeated use.
Electrodes↗
An overview of the uses and abuses of electrodiagnosis in ophthalmology.
When to use electrodiagnostic procedures and clinical psychophysical procedures, and when not to. The importance of analysing unexplained loss of vision is emphasised.
Electrodiagnosis↗
Cutaneous melanoma-associated retinopathy.
PURPOSE: To define further the syndrome of cutaneous melanoma-associated retinopathy, of which only five affected patients have been reported previously. METHODS: Three men with melanoma-associated retinopathy were examined and studied electrophysiologically. Two were studied in detail psychophysically. RESULTS: Visual symptoms consisted of flickering black and white spots, shimmering patches of colors, and night blindness. The onset was acute and nonprogressive. Reduced amplitudes were observed in the flash electroretinographic b-wave and the pattern electroretinogram. Color vision, contrast sensitivity, and light- and dark-adapted perimetric sensitivities were abnormal. In one patient, the rate of dark adaptation was normal with elevated final cone and rod thresholds. CONCLUSIONS: Melanoma-associated retinopathy is a paraneoplastic syndrome distinct from cancer-associated retinopathy with a different visual prognosis. It may preferentially affect men.
Aged↗
Macular dystrophy associated with mutations at codon 172 in the human retinal degeneration slow gene.
BACKGROUND: Recently, mutations in the retinal degeneration slow (rds) gene which codes for peripherin-rds have been implicated as a cause of autosomal dominant retinitis pigmentosa. Because this gene is expressed in both rods and cones, mutations in the rds gene might be expected to cause degeneration affecting either the scotopic or photopic systems. Mutations at codon 172 of the rds gene have been identified in three families with autosomal dominantly inherited, progressive macular dystrophy. METHODS: Affected individuals underwent ophthalmic examination, scotopic perimetry, dark adaptometry, measurement of color-contrast sensitivity, and electroretinography to characterize the photoreceptor dysfunction. RESULTS: In all but one affected member, symptoms of progressive central visual loss developed in the third or fourth decade of life accompanied by central scotoma and well-demarcated atrophy of the retinal pigment epithelium and choriocapillaris of the macula. In general, cone and rod thresholds were elevated, and color-contrast sensitivity was absent in the central visual field. Peripherally, the scotopic sensitivities were normal, as was the recovery from bleach. Cone electroretinograms were diminished in amplitude, and delayed in all affected adults except one. Rod electroretinograms were normal or near normal in amplitude, and had normal implicit times. Affected asymptomatic children had macular changes, abnormal color-contrast sensitivity, and reduced pattern and cone electroretinograms. CONCLUSION: These results indicate that mutations in the rds gene can be expressed as a macular dystrophy, with evidence of primary cone dysfunction and preservation of peripheral rod function.
Adolescent↗
Electrophysiology and psychophysics in ocular hypertension and glaucoma: evidence for different pathomechanisms in early glaucoma.
It is not clear whether glaucomatous optic nerve damage is the end result of one pathological process or whether there are several mechanisms by which the final disease is manifest. The use of electrophysiological and psychophysical tests which measure the function of specific subdivisions of the visual pathways have been shown to be of use in the early diagnosis of glaucoma. In addition these results may help to elucidate the mechanisms of loss of visual function in patients with early glaucoma. One hundred and ninety-three patients with ocular hypertension (intraocular pressure > 24 mmHg, with normal visual fields and optic discs), 30 with glaucoma and 35 controls underwent pattern electroretinogram (PERG), peripheral colour contrast thresholds, motion detection thresholds (MDT) and Humphrey automated visual fields at the same visit. For each test there was a significant proportion of patients with abnormal results as has been found in previous studies of these techniques. However, there was a significant lack of correlation between the groups with only a small number of patients having abnormalities on more than one test. Of the patients demonstrating abnormal PERGs, 36% had abnormal colour contrast and 32% abnormal MDT, but only 15% were abnormal on both tests. Early glaucomatous damage may be focal or diffuse in nature. Similarly there may be preferential damage to ganglion cells subserving different visual functions or damage at different retinal layers. The results lend support to these hypotheses and give further evidence that more than one pathomechanism may be involved early in the glaucomatous process.
Color Perception↗