Biomedical subjects

G Haegerstrom-Portnoy

Publications and source records attributed to G Haegerstrom-Portnoy.

At least 19 recordsLinked to original sources

PubMed2001

The Smith-Kettlewell Institute (SKI) longitudinal study of vision function and its impact among the elderly: an overview.

We present an overview of a multifaceted longitudinal study of vision function and its interaction with daily activities, health, and well-being among 900 persons aged 58 to 102 years at the first visit. Standard vision measures as well as nonconventional tests designed to assess visual performance under the nonideal conditions encountered in everyday life were used. Here we summarize a few of the findings to date, with an emphasis on a direct comparison of declines in different aspects of vision function with age. The rates of declines with advancing age vary widely for the different vision functions. Also described is the reading performance of the sample and its association with some of the vision measures. Furthermore, we describe some of the associations between vision test scores and extensive longitudinal health and functioning data collected by the Buck Center for Research in Aging. Findings show that many older people with good acuity are effectively visually impaired in performing everyday tasks involving low and changing light levels, stereopsis, glare, and low contrast. We also found that vision under nonideal conditions cannot be predicted from standard acuity on an individual basis.

Activities of Daily Living↗

PubMed2000

Ocular contributions to age-related loss in coarse stereopsis.

PURPOSE: To determine the basis for the dramatic decline in coarse stereopsis that occurs with age. METHODS: The Frisby test was used to assess stereopsis in a large sample of randomly selected persons over the age of 58 years. A number of other vision functions were also assessed in the same persons. The data were used to address the question of whether the decline in stereopsis reflects age-related alterations in cortical stereopsis mechanisms themselves (e.g., disparity detectors) or a degradation of the signal reaching the cortex as a result of alterations in earlier visual components. Two of three vision measures were binocular and thus reflect predominantly the function of the better eye. RESULTS: We find, as many others have reported, that even very coarse stereopsis declines dramatically with age. Despite not having separately assessed each eye, we find that among those selected to have good ocular function there was no significant decline in coarse stereopsis with age. CONCLUSION: These findings suggest that the enormous decline in coarse stereopsis with age can be accounted for by alterations in early stages of vision processing.

Aged↗

PubMed2000

The relation between visual acuity and other spatial vision measures.

PURPOSE: To examine to what extent measurement of standard visual acuity allows prediction of other spatial vision measures on an individual basis when high correlations exist between visual acuity and the other measures. METHODS: A series of spatial vision functions were measured in a sample of 900 community-dwelling older observers. Regression analysis was performed, and correlation coefficients were calculated between standard high-contrast visual acuity and other spatial vision measures including contrast sensitivity, low-contrast acuity, low-contrast low-luminance acuity (SKILL card), and disability glare acuity. RESULTS: All measures were highly and significantly correlated with standard visual acuity (r = 0.68 to 0.91). Despite the high correlations, many predictions of the other spatial vision measures from the correlation with standard acuity fell considerably outside of acceptable ranges determined by repeatability. The influence of the range of values in correlations is emphasized. CONCLUSIONS: Other spatial vision measures cannot be predicted on an individual basis from visual acuity despite high and significant correlations between the measures.

Aged↗

PubMed1999

Rods induce transient tritanopia in blue cone monochromats.

Transient tritanopia is a cone-cone post-receptoral interaction between short-wavelength (S) cones and medium (M) and long (L) wavelength cones. Blue cone monochromats have rods and S cones of normal sensitivity but lack functional M/L cones. All blue cone monochromats tested (n = 8) show significant amounts of transient tritanopia mediated by rods. Attempts to find a similar rod-S cone interaction while silencing the L/M cones in normals yielded only a small amount of S cone sensitivity loss. The results suggest an exaggerated influence of rods on the S cone pathway in the retina of blue cone monochromats.

Adaptation, Ocular↗

PubMed1999

Forever young: visual functions not affected or minimally affected by aging: a review.

Six visual functions, once developed to adult levels of performance, have been noted to exhibit little or no alteration with aging (also see Appendix, Note 1). Those selected for more substantial discussions in this article are: (a) the Stiles-Crawford effect of the first kind (SCE-I), also known as the "directional sensitivity of the retina"; (b) specific vernier acuity paradigms (including alignment of two lines one with the other, and two- and three-point vernier alignment tasks); and (c) color vision-related perceptual constancies. Each of these functions has rather different origins in the visual system. The SCE incorporates optical waveguide photoreceptor properties and has both physical and physiological origins; vernier acuity (one of the hyperacuities) is largely the result of neural data processing mechanisms; and the color vision-related effects have their origins in retinal neural processes. Descriptions of additional visual functions minimally affected by age are presented as well. This recent research raises many questions. How can these visual responses be so stable, when so many other visual responses show decrements with aging? What does it mean if anomalous responses within the more stable functions are encountered in individuals? Can these age-resistant functions be employed to help sustain other functions in aging individuals? Are such relatively invariant functions limited to the visual system? Because of the stability of the reported responses with aging, these same relationships can be used as test controls for other studies of aging, and as benchmarks to distinguish between "normal" aging and disease processes.

Aged↗

PubMed1999

Seeing into old age: vision function beyond acuity.

PURPOSE: To provide a comprehensive description of vision function beyond acuity in older individuals. METHODS: A sample of 900 individuals between the ages of 58 and 102 years (mean age of 75.5) was binocularly tested wearing habitual correction on a battery of psychophysical tests including high and low contrast acuity, low contrast low luminance acuity, disability glare, contrast sensitivity, color vision, stereoacuity, recovery from glare, and attentional visual fields. RESULTS: High contrast acuity is reasonably well maintained on average, even into very old ages. Spatial vision measures under conditions of reduced contrast or luminance, or glare reveal significant impairment in a large portion of the aged. Many older individuals also have greatly reduced stereopsis, poor color discrimination, and severely restricted peripheral fields under conditions of divided attention. A single exponential function relating performance to age fits all spatial vision data sets. The function for individual spatial measures lies at different positions along the age scale. The derived aging function with a time constant of approximately 15 years also fits results from other recent aging studies of acuity and contrast sensitivity. CONCLUSIONS: Standard visual acuity underestimates the degree of vision function loss suffered by many older individuals under the nonoptimal viewing conditions encountered in daily life. All spatial vision functions show a similar rate of decline with age of the population, but the age at which decline begins varies among measures.

Aged↗

PubMed1998

Topography of the multifocal electroretinogram.

The functional topography of the human retina was characterized using the multifocal electroretinogram (ERG), with particular attention to the form of the decline in response with retinal eccentricity. Population response variability was examined and compared to standard full field ERG variability. Burian-Allen contact lens electrodes were used to record the cone multifocal ERG from 50 young eyes (28.3 years +/-5.9 years). Responses were recorded in 8 min from 103 retinal locations within the central +/-22 degrees. The spatial distribution of local responses showed an exponential fall-off with eccentricity. The exponential slope parameter was highly similar across individuals. Excluding responses to the central element, the fall off with eccentricity approximated a power function with an exponent of -0.6, which compares to the -0.74 exponent for the human cone density profile. The inter-individual variance in response density is greatest at the central fovea, reducing towards more peripheral locations. The logarithm of response density, however, shows approximately equal variance across eccentricity, making log density a more appropriate way to view response topography. The population range (+/-2 S.D.) of response density is 0.42 log unit, similar to that of standardized ganzfeld electroretinography. The response exponential decay provides a potentially useful addition to element-by-element comparison, in deciding whether an eye's response is within normal limits.

Adult↗

PubMed1997

The SKILL Card. An acuity test of reduced luminance and contrast. Smith-Kettlewell Institute Low Luminance.

PURPOSE: To design and evaluate a new vision test that combines low contrast and reduced illumination to stress the visual system and be sensitive to subtle alterations in function. METHODS: A simple new clinical test, the Smith-Kettlewell Institute Low Luminance (SKILL) Card, is designed to measure spatial vision under conditions of reduced contrast and luminance using normal office lighting. The SKILL Card consists of two near acuity charts mounted back to back. One side has a chart with black letters on a dark gray background designed to simulate reduced contrast and luminance conditions. The other side has a high-contrast, black-on-white letter chart. The SKILL score is the acuity loss (number of letters) between the light and dark sides. RESULTS: Age norms for a large normal population have been established and show that test scores increase with age, particularly after age 50. Repeatability is as good as that of standard Snellen acuity. The SKILL score is affected minimally by blur, but it is affected by large variations in light level. SKILL scores are sensitive to the presence of visual disease such as "recovered" optic neuritis. CONCLUSIONS: The SKILL card allows quick, reliable measurement of the effect of reduced luminance and contrast on acuity SKILL scores are not correlated with other vision measures in patients with optic neuritis, which shows that the SKILL card measures a different dimension of vision function than existing clinical tests.

Adult↗

PubMed1997

Color vision defect type and spatial vision in the optic neuritis treatment trial.

PURPOSE: To describe the types of color vision defects present in the acute phase of the disease and 6 months into recovery in the 438 participants of the Optic Neuritis Treatment Trial. METHODS: Patients meeting strict eligibility criteria were seen within 8 days of the onset of symptoms and then at regular follow-up visits. At the first and 6-month visits (and subsequent annual visits), spatial vision (acuity, contrast sensitivity), visual fields, and color vision were measured. Farnsworth-Munsell 100-hue tests were scored by a variant of the method of quadrant analysis described by Smith et al (Am J Ophthalmol. 1985; 100:176-182). RESULTS: Most persons show mixed red-green (RG) and blue-yellow (BY) color defects (one type predominating, accompanied by a lesser defect of the other type). BY defects tend to be slightly more common in the acute phase of the disease, with slightly more RG defects at 6 months. Persons may shift defect type over time. Defect type was not related to any of the spatial vision measures at either test time or to treatment group; however, severity of color defect was related to both spatial vision measures and treatment group. CONCLUSIONS: Contrary to common clinical wisdom, optic neuritis is not characterized by selective RG defects. Color defect type cannot be used for differential diagnosis of optic neuritis.

Acute Disease↗

PubMed1996

Mechanisms underlying the detection of increments in parafoveal retina.

It is well established that the spectral sensitivity under photopic conditions varies across the human retina. We investigate the mechanisms underlying these spectral changes. Through the use of color appearance, flicker sensitivity, additivity, discrimination at threshold and modeling, we show that the changes in spectral sensitivity on a photopic white background across parafoveal retina are consistent with shifts in cone weightings to (L-M) and (M-L) chromatic channels. This two channel model, developed to account for foveal spectral sensitivity curves (Sperling & Harwerth, 1971 Science, 172, 180-184), provides a better description of parafoveal data than both a single color channel upper envelope model (comprised of a single red-green opponent channel and an achromatic mechanism) and a vector model (combining a red-green opponent channel with an achromatic component). Thus while the two channel model ([L-M] and [M-L]) of foveal color vision is generalizable to the parafovea, simple models with a unitary red/green process are not. Although the two channel model can accurately fit parafoveal spectral sensitivity curves without it, a small contribution from a luminance mechanism might improve the ability of the two channel model to account for threshold discrimination and additivity data.

Color Perception↗

PubMed1996

Clinical vision characteristics of the congenital achromatopsias. I. Visual acuity, refractive error, and binocular status.

Visual acuity, refractive error, and binocular status were determined in 43 autosomal recessive (AR) and 15 X-linked (XL) congenital achromats. The achromats were classified by color matching and spectral sensitivity data. Large interindividual variation in refractive error and visual acuity was present within each achromat group (complete AR, incomplete AR, and XL). However, the number of individuals with significant interocular acuity differences is very small. Most XLs are myopic; ARs show a wide range of refractive error from high myopia to high hyperopia. Acuity of the AR and XL groups was very similar. With-the-rule astigmatism of large amount is very common in achromats, particularly ARs. There is a close association between strabismus and interocular acuity differences in the ARs, with the fixating eye having better than average acuity. The large overlap of acuity and refractive error of XL and AR achromats suggests that these measures are less useful for differential diagnosis than generally indicated by the clinical literature.

Adolescent↗

PubMed1996

Clinical vision characteristics of the congenital achromatopsias. II. Color vision.

Twelve X-linked (XL) achromats and 43 autosomal recessive (AR) achromats were tested using the Farnsworth D-15, Nagel anomaloscope, Sloan achromatopsia test, and Berson test using standard procedures. All of the tests identify achromatopsia, but very few differentially diagnose the various types. AR achromats were subclassified as complete (rods only) or incomplete (residual cone function present) by additional psychophysical testing. Complete and incomplete ARs do not perform differently on any clinical color vision measure, indicating that (1) rods predominantly mediate vision in both groups and (2) these tests are not useful for distinguishing between the groups. Both groups show considerable interindividual variation on all measures. Only one of the measures, the Berson test, designed to distinguish XLs from ARs, does so reliably. XLs and ARs do not differ significantly on the Nagel anomaloscope or most of the Sloan plates. The confusion angles of the D-15 do differ for the two groups, but the variability in each group makes the measure unreliable for classifying individuals. The Berson test is recommended to distinguish the XL from AR achromats.

Adolescent↗

PubMed1996

Optimum parameters for short-wavelength automated perimetry.

PURPOSE: To determine the optimum parameters for short-wavelength automated perimetry (SWAP) and to recommend these for standardization of the procedure. METHODS: We used a variety of stimulus and background configurations to determine the optimum background spectral distribution and luminance, and the optimum target spectral distribution, maximum luminance, and duration. We measured threshold versus intensity curves to determine which combination provided (a) the greatest isolation of the short-wavelength sensitive mechanisms and (b) the largest dynamic range for perimetry. We also evaluated the effect of lens absorption and cataract on these two factors. RESULTS: A broad-band yellow background at 100 candela/m2 with a narrow-band 440-nm (27-nm half-bandwidth), 1.8 degrees diameter (Goldmann size V) stimulus presented for 200 ms was optimum at all retinal eccentricities. Specific recommendations for how to modify existing perimeters are given. CONCLUSION: Agreement regarding the optimum parameters for SWAP should lead to standardization of the test that will facilitate comparison of results from different centers. Normative data can be collected at several sites and incorporated into statistical analysis packages currently available with various perimeters. This will greatly improve the clinical utility of this test.

Aged↗

PubMed1994

S-cone sensitivity in unilateral aphakia.

BACKGROUND: Exposure to ultraviolet radiation (UVR) and blue light has been shown to cause retinal damage in animals. In humans, it has been argued that the loss of short-wavelength (S) cone sensitivity during normal aging may be related to chronic light exposure. METHODS: We measured sensitivity to blue and yellow lights presented on bright yellow backgrounds at several retinal eccentricities in both eyes of an observer with long-standing unilateral aphakia. RESULTS: For yellow lights, where media absorption is not a major factor, there was a 2-fold loss in sensitivity of long (L) and medium (M) wavelength cone mechanisms in the aphakic eye relative to the phakic eye. For blue lights detected by S-cones, there was a 10-fold loss of S-cone mechanism sensitivity in the aphakic eye, after differences in ocular media density were taken into account. CONCLUSIONS: Our findings strongly support the hypothesis that chronic exposure to short wavelength radiation impairs S-cone function.

Adult↗

PubMed1994

Foveal vision function before and after fluorescein angiography.

PURPOSE: Fluorescein angiography is routinely used in ophthalmologic practice with minimal changes in vision reported by the patient after the procedure. Recent animal work has suggested that fluorescein may be cytotoxic in the presence of light and may cause retinal damage. The authors examined whether any changes occur in foveal vision function after fluorescein angiography. METHODS: A battery of tests of vision function--including visual acuity, contrast sensitivity, color vision, and two-color increment thresholds designed to isolate individual cone pathways--was administered before and 48 hours after fluorescein angiography to a group of 10 patients with good visual acuity. RESULTS: Most of the patients showed significant abnormalities with the nonstandard tests; however, no significant changes in central vision function were found 48 hours after fluorescein angiography. CONCLUSION: Even sensitive vision tests show no measurable effect of fluorescein angiography on foveal vision function in eyes with significant disease.

Adult↗

PubMed1993

New procedures for evaluating vision functions of special populations.

Research over the last few decades has demonstrated the rapid development of vision function that occurs in infancy with near-adult levels reached before the age of 1 year. This period of rapid development coincides with the period of maximum sensitivity to insult. These facts emphasize the importance of effective screening techniques for visual disorders. Off-axis photorefraction is described as a new and effective screening technique for detection of refractive errors, media opacities, and strabismus. Separate from screening, a significant need exists for optometric vision evaluations in special populations. Normal infants, developmentally delayed or multi-handicapped children and adults, and cognitively impaired adults are examples of special populations who are difficult to examine with standard optometric techniques. New procedures for measuring visual acuity, contrast sensitivity, color vision, and stereopsis using behavioral or electrophysiological measures are described. Advantages and disadvantages of the different techniques are discussed.

Color Perception↗

PubMed1990

LWS cone effects on rod threshold and saturation in achromats with residual cone function.

Rod saturation on flashed and steady red backgrounds was investigated in normals and three achromats, two of whom were found to have some residual cone function. LWS cones selectively reduce the background level at which rod saturation occurs and elevate rod thresholds at flashed background levels well below saturation. Both of these LWS cone actions are also present in eyes with greatly reduced LWS cone function. In normal eyes LWS cones also elevate rod thresholds on steady backgrounds. We thus conclude that LWS cones influence rods through different mechanisms under transient (flashed) and steady-state background stimulation and that the increase in rod visual sensitivity observed during prolonged presentation of a background is due to a time-dependent reduction of LWS cone influence on rods. Finally, the finding that rod-cone interactions of the same magnitude found in normals can be seen in individuals where the cones' ability to mediate vision is severely reduced suggests the rod saturation paradigm as a sensitive technique for revealing residual LWS cone function.

Adaptation, Ocular↗

PubMed1990

Spatial sensitization in the short wavelength sensitive pathways under dichoptic viewing conditions.

Spatial sensitization (Westheimer) functions were measured under conditions that isolated the short wavelength sensitive pathways. The variable diameter pedestal and the test probe were either presented to the same eye (monoptic presentation) or to different eyes (dichoptic presentation). The most significant new finding was that a dichoptically presented, small, blue pedestal caused threshold elevations of about 1-2 long units for an S cone detected probe. However, a large pedestal caused little or no change in threshold. This result contrasts with previous results using white light stimuli, which showed that steadily presented dichoptic pedestals caused little or no threshold change. Furthermore, we show there is little masking when the probe is detected by the isolated M or L cone pathways. These data thus demonstrate a binocular, size dependent interaction revealed only when S cones detect the probe.

Contrast Sensitivity↗