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PubMed2001

Visual disorders in children with brain lesions: 2. Visual impairment associated with cerebral palsy.

Disorders of visual function are a common finding in children with cerebral palsy. In some cases they are secondary to ophthalmologic abnormalities such as cataract or retinopathy, but more often they are due to damage of the central visual pathway. We review the literature on the prevalence and distribution of visual abnormalities in children with cerebral palsy and their relation to cognitive, motor and emotional development.

Cerebral Palsy↗

PubMed1998

Validation of the Warrington theory of visual processing and the Visual Object and Space Perception Battery.

Competing hypotheses regarding the nature of visual processing were examined using the performance of 111 healthy older persons on the Warrington and James (1990) Visual Object and Space Perception Battery (VOSP). Confirmatory factor analysis indicated that a two-factor model corresponding to the Warrington theory of object and space perception as discrete domains showed excellent congruence with the data, despite limitations in the VOSP space perception tests that may have resulted in underestimation of model fit. Moreover, compared to a unidimensional model of visual processing, the Warrington model demonstrated a superior fit to the data. These findings add to the bodies of evidence supporting a dissociation between object- and space-perception abilities and defining the construct validity of the VOSP battery.

Aged↗

PubMed1999

Visual search and visual target detection in patients with infarctions of the left or right posterior or the right middle brain artery.

We compared visual target detection and search performance of patient groups with infarctions of (1) the right middle brain artery (R-MBA) and with neglect; (2) the left posterior artery (L-PBA), (3) the right posterior artery (R-PBA), the latter two groups had contralesional hemianopias, or (4) with right hemisphere lesions without hemianopia or neglect. We found that: (1) The first three groups differed from the fourth (control) group in omissions. (2) The first three groups differed only in horizontal search but not in target detection. (3) No vertical search deficit was present for either group. (4) R-MBA patients found increasingly more targets in visual search from left to right, R-PBA patients had problems with the outermost contralesional column, L-PBA patients showed a generally slowed and more variable search pattern. Infarctions of left and R-PBA therefore resulted in different visual search patterns. The behavior of the patients with R-MBA is consistent with Kinsbourne's (1992) interactive inhibition theory of neglect.

Aged↗

PubMed2003

The development and validation of a questionnaire to assess visual symptoms/dysfunction and impact on quality of life in cataract patients: the Visual Symptoms and Quality of life (VSQ) Questionnaire.

The aim of the study was to develop a new questionnaire to assess visual symptoms/dysfunction and impact on vision-specific quality of life for those undergoing second eye cataract extraction. Items for the VSQ questionnaire were devised with reference to existing literature and following consultation with eye care experts (n = 18) and interviews with cataract patients (n = 40). Piloting work conducted with 53 patients indicated that the questionnaire was promising, with a high level of internal consistency, low levels of missing data and indications that it was responsive to surgery. A modified version of the questionnaire was completed by 105 patients having received 'early' surgery and 103 scheduled for routine surgery within a randomised controlled trial evaluating the effectiveness of second eye cataract surgery. Analyses showed that the internal consistency of both the visual symptoms/dysfunction and quality of life areas was high (Cronbach's alpha 0.82 and 0.83, respectively). Highly significant improvements were found for early surgery patients (p < 0.0001), with little change among routine surgery patients. Two final versions of the VSQ questionnaire have been produced for future use in assessing visual symptoms/dysfunction and impact on vision-specific quality of life: a scoreable short form and more detailed and sensitive long form.

Adult↗

PubMed1996

Rapid visual learning in neurones of the primate temporal visual cortex.

The human visual system can learn to recognize visual stimuli rapidly. For example, humans can accurately reconstruct meaningful objects out of fragmentary evidence, once they have seen the same object in its unambiguous form. The anterior temporal cortical areas of macaques contain some neurones with invariant visual responses which appear to provide a representation of complex patterns and objects, such as faces. Remarkably, these neurones show an enhancement of response after brief (e.g. 5 s) exposure to the unambiguous stimulus, an effect that appears to reflect the neural basis of the rapid perceptual learning seen in humans.

Animals↗

PubMedDate not supplied

Older persons' performance on auditory, visual, and auditory-visual presentations of the Edgerton and Danhauer Nonsense Syllable Test.

The speech sound discrimination abilities of 15 normal-hearing and 15 sensorineural hearing-impaired subjects between 55 and 65 years of age were assessed using videotaped presentations of the Nonsense Syllable Test (NST). Stimuli were presented in auditory (A), visual (V), and auditory-visual (AV) modes. All subjects received the stimuli in two trials for each presentation mode; hearing-impaired subjects were unaided for the first, and wore their own hearing aids for the second. Responses were transcribed phonemically and were scored by the phoneme method. Intra- and interjudge reliability was greater than 90%. Mean phoneme discrimination scores were plotted for each group across the three presentation modes. The results revealed that: both groups' performance improved from V to A to AV modes, but differences were apparent in the amount of increase across modes within each group; the NST differentiated between groups in the A and AV modes, but not in the V mode; the NST identified "poor" speechreaders in each group under both V and AV conditions; and consonant errors in the V mode formed seven homophenous categories based on place of articulation. The NST can be a useful screening test in auditory rehabilitation to distinguish those hearing-impaired persons who naturally take advantage of visual cues from those who do not.

Acoustic Stimulation↗

PubMed1986

Two modes of processing visual information: implications for assessing visual impairment.

The recognition of visual detail and the ability to orient spatially to visual stimuli are apparently subserved by distinct modes of processing, termed "focal" and "ambient," respectively. Current clinical techniques are well suited to evaluate aspects of focal vision, but do little to evaluate ambient visual functions. As a result, the impairment of ambient functions may be difficult to specify or may be overestimated. Implications for the development of assessment techniques for ambient functions are discussed.

Humans↗

PubMed1996

Changes in myopia, visual acuity, and psychological distress after biofeedback visual training.

The effects of auditory biofeedback training on myopia, visual acuity (VA), and psychological distress were evaluated in a controlled prospective study involving 55 mildly myopic (< or = -3.5 D) high school students. These myopes were divided into 2 groups, matched for age and dioptric defect: 33 were treated with visual training and 22 were not; 27 emmetropic subjects formed a further control group. Subjects were evaluated at the baseline (T0), at 10 weeks after the end of the treatment (T1), and after an interval of 12 months (T2) from the baseline for: (1) manifest and cycloplegic refraction, and the difference between them (cycloplegic tonus); (2) VA measured with a conventional optotype in all subjects, and also with a computer-generated optotype in the treated group; and (3) psychometric values and personality profile. At T2, myopia had significantly worsened both in the treated and in the control myopes; VA in the treated myopes appeared significantly improved when measured by the conventional optotype, but unchanged when measured by computer. Psychometric scores improved significantly in the treated myopes and in the emmetropic controls. Objectively the autorefractometer showed that 38% of the myopes had voluntary control of positive accommodation, i.e., the ability to increase spherical defect; no voluntary control of negative accommodation was observed. An increase in VA was associated with a significant increase in the foveation time (i.e., the period of time when the target is imaged on the fovea and the eye is motionless), and was partly attributable to a learning effect. In conclusion, biofeedback visual training had a positive effect on psychological distress and subjective VA improvement, but failed to reduce the existing myopia or delay its evolution.

Adolescent↗

PubMed1996

The Freiburg Visual Acuity test--automatic measurement of visual acuity.

The Freiburg Visual Acuity test is an automated procedure for self-administered measurement of visual acuity. Landolt-Cs are presented on a monitor in one of eight orientations. The subject presses one of eight buttons, which are spatially arranged on a response box according to the eight possible positions of the Landolt-Cs' gap. To estimate the acuity threshold, a best PEST (best Parameter Estimation by Sequential Testing) procedure is used in which a psychometric function having a constant slope on a logarithmic acuity scale is assumed. Measurement terminates after a fixed number of trials. With computer monitors, pixel-discreteness artifacts limit the presentation of small stimuli. By using anti-aliasing, i.e., smoothing of contours by multiple gray levels, the spatial resolution was improved by a factor of four. Thus, even the shape of small Landolt-Cs with oblique gaps is adequate and visual acuities from 5/80 (0.06) up to 5/1.4 (3.6) can be tested at a distance of 5 m.

Diagnosis, Computer-Assisted↗

PubMed2005

Coupling between visual evoked cerebral blood flow velocity responses and visual evoked potentials in migraneurs.

Neurovascular coupling may be altered in migraneurs. Therefore, visual evoked potentials (VEP) and visually evoked cerebral blood flow velocity responses (VEFR) were simultaneously recorded in 30 healthy controls and 30 migraneurs interictally using a checkerboard stimulus with visual contrasts of 1%, 10% and 100%. The VEFR were measured in the posterior cerebral artery using transcranial Doppler and VEP were recorded from occipital leads. We found an increase in VEFR and VEP in both the healthy and migraneur groups (P < 0.01). VEFR were significantly higher in migraneurs (P < 0.01), while VEP did not significantly differ between the groups (P > 0.05). Regression showed a significant association between VEP and VEFR in both healthy controls (r = 0.66, P < 0.01) and migraneurs (r = 0.63, P < 0.01). The regression coefficient of migraneurs (b = 0.88, SE = 0.08) was significantly higher than that of healthy controls (b = 0.55, SE = 0.07) (P = 0.04). We conclude that neurovascular coupling is increased in migraneurs interictally.

Adult↗

PubMed1990

Pattern reversal visual evoked potentials (VEP-PR) in migraine subjects with visual aura.

Twenty patients with migraine with visual aura, aged 19 to 55 years (2 men and 18 women) were studied by the method of Visual Evoked Potentials (VEP). The control group consisted of an equal number of healthy subjects, comparable for age and sex. The most important finding in our study is that migraine patients with visual prodromata have a significantly longer P100 latency than the subjects of control group. These modifications of the VEP-PR could indicate, as other investigators have pointed out, that there are some special metabolic conditions and abnormalities of neuromediators during and between attacks.

Adult↗

PubMed1998

Auditory-visual speech recognition by hearing-impaired subjects: consonant recognition, sentence recognition, and auditory-visual integration.

Factors leading to variability in auditory-visual (AV) speech recognition include the subject's ability to extract auditory (A) and visual (V) signal-related cues, the integration of A and V cues, and the use of phonological, syntactic, and semantic context. In this study, measures of A, V, and AV recognition of medial consonants in isolated nonsense syllables and of words in sentences were obtained in a group of 29 hearing-impaired subjects. The test materials were presented in a background of speech-shaped noise at 0-dB signal-to-noise ratio. Most subjects achieved substantial AV benefit for both sets of materials relative to A-alone recognition performance. However, there was considerable variability in AV speech recognition both in terms of the overall recognition score achieved and in the amount of audiovisual gain. To account for this variability, consonant confusions were analyzed in terms of phonetic features to determine the degree of redundancy between A and V sources of information. In addition, a measure of integration ability was derived for each subject using recently developed models of AV integration. The results indicated that (1) AV feature reception was determined primarily by visual place cues and auditory voicing + manner cues, (2) the ability to integrate A and V consonant cues varied significantly across subjects, with better integrators achieving more AV benefit, and (3) significant intra-modality correlations were found between consonant measures and sentence measures, with AV consonant scores accounting for approximately 54% of the variability observed for AV sentence recognition. Integration modeling results suggested that speechreading and AV integration training could be useful for some individuals, potentially providing as much as 26% improvement in AV consonant recognition.

Adult↗

PubMed2005

Causes of severe visual impairment and blindness in schools for visually handicapped children in Iran.

AIMS: This survey was conducted on children in schools for the blind in Tehran (from 2002 to 2003) to determine the causes of severe visual impairment and blindness and to identify preventable and treatable conditions. METHODS: The study was performed on 362 students at different grades in three schools for the blind. Patient sex, age, family history of blindness or low vision, visual acuity, causes of blindness, and treatable and preventable conditions were studied. RESULTS: Of the 362 cases, 210 (58%) were boys and 152 (42%) were girls. Mean age was 13.5 (SD 4) years. Severe visual loss was seen in 80.9%. Retinal diseases were the most common cause for low vision (51%); cataract, optic nerve atrophy, corneal and anterior segment diseases, glaucoma, anophthalmia, and globe malformations were other major causes of blindness. Treatable aetiologies and positive family history of blindness were seen in 25.7% and 36% of the patients, respectively. The incidence of preventable diseases, excluding familial disorders, was low. CONCLUSION: In addition to the prevention and treatment of some conditions, premarital genetic counselling and family planning control in families with inherited diseases could decrease the number of blind children in the future in Iran.

Adolescent↗

PubMed1978

Physiological consequences for the cat's visual cortex of effectively restricting early visual experience with oriented contours.

1. The early visual experience of nine cats was restricted to viewing horizontal or vertical lines inside opaque goggles. 2. When the kittens were 3-4 mo old, extracellular recordings were made in the primary visual cortex. To obtain a representative sample of cortical cells, units were studied at regularly spaced intervals along the course of electrode penetrations traveling oblique to the cortical surface. An automated assessment of preferred orientation using a computer-driven optical display was employed, and during the recording session the experimenters did not know which orientation(s) each animal had viewed in early life. 3. In the cats that viewed horizontal lines with one eye and vertical lines with the other during rearing, two major findings of previous workers (14) were confirmed. First, a majority of units were not selective for orientation. Second, units with preferred orientations near vertical tended to be activated exclusively by the eye that had viewed vertical, and likewise for horizontal. 4. In cats that viewed lines of the same orientation with both eyes during rearing, a substantially smaller proportion of units were selective for orientation; the preferred orientations of these units also tended to match the orientation to which the cats had been exposed. 5. Portions of some electrode penetrations showed an orderly arrangement of cells according to preferred orientation similar to that seen in normal cats, but with regions over which only nonselective cells were found. Many penetrations appeared less orderly. 6. The results are consistent with a role for early visual experience in maintaining the responsiveness and innate selectivity of cortical neurons, although they cannot entirely rule out the possibility that experience may alter or determine the preferred orientation of some cells.

Animals↗

PubMed1988

Evaluation of corrected loss variance as a visual field index. I. CLV exceeds RMS in discriminating between glaucoma-suspect patients with no loss of visual sensitivity and normal observers.

Octopus visual fields were compared for three groups of patients: (1) diagnosed glaucoma patients; (2) glaucoma-suspect patients, and (3) control observers. Four visual field indices were analyzed for each visual field: mean sensitivity, short-term fluctuation (root mean square), mean defect, and corrected loss variance. Among the four indices, corrected loss variance was the only index that discriminated the glaucoma-suspect group from the control group, while, as expected, the glaucoma group differed from the other two study groups for all four indices. These data support the view that corrected loss variance may provide highly sensitive information on which to base an early clinical diagnosis of glaucoma in patients who do not demonstrate traditional field loss.

Adult↗

PubMed2006

Visual acuities "hand motion" and "counting fingers" can be quantified with the freiburg visual acuity test.

PURPOSE: The visual acuity (VA) of patients with very low vision is classified using the semiquantitative scale "counting fingers" (CF), "hand motion" (HM), "light perception" (LP), and "no light perception." More quantitative measures would be desirable, especially for clinical studies. The results of clinical VA measurements, Early Treatment Diabetic Retinopathy Study (ETDRS) charts, and the Freiburg Visual Acuity Test (FrACT) were compared. The FrACT is a computerized visual acuity test that can present very large Landolt C optotypes when necessary. METHODS: Examined were 100 eyes of 100 patients with various eye diseases (e.g., diabetic retinopathy, ARMD), covering a range of VAs from LP to decimal 0.32. The FrACT optotypes were presented on a 17-inch LCD monitor with random orientation. After extensive training, two ETDRS and FrACT measurements were obtained. The testing distance was 50 or 100 cm. RESULTS: ETDRS and FrACT coincided closely for VA > or = 0.02 (n = 80). ETDRS measures were successfully obtainable down to CF (at 30 cm; test-retest averaged over all patients, coefficient of variation [CV](ETDRS) = 9% +/- 8%), and FrACT provided reproducible measurements down to HM (test-retest CV(FrACT) =12% +/- 11%). For CF (n = 6), both ETDRS and FrACT resulted in a mean VA of 0.014 +/- 0.003 (range, 0.01-0.02). The VA results of FrACT for HM (n = 12) were 0.005 +/- 0.002 (range, 0.003-0.009); the individual values were highly reproducible. No results were obtainable for LP (n = 2). CONCLUSIONS: The three acuity procedures concur above a VA of 0.02. The results suggest that the category CF at 30 cm can be replaced by 0.014, using ETDRS or FrACT. Using FrACT, one can even reproducibly quantify VA in the HM-range, yielding a mean VA of 0.005.

Adult↗

PubMed2006

Dynamic measures of visual function and their relationship to self-report of visual functioning.

PURPOSE: The purpose of this analysis was to determine whether dynamic measures of vision, such as dynamic acuity and motion threshold, are independently associated with self-reported difficulty in activities involving vision. METHODS: Data were used from the third round of the Salisbury Eye Evaluation (n = 1198), a longitudinal, population-based study of older adults. Multiple measures of visual function were tested, including dynamic acuity, motion threshold, visual acuity, contrast sensitivity, visual fields, and stereoacuity. Difficulty was assessed using the Activities of Daily Vision Scale (ADVS). Polytomous logistic regression procedures were used to determine log odds ratios for the dynamic measures of vision while adjusting for demographic, health, and other measures of vision. RESULTS: In fully adjusted models including other vision variables, worse dynamic acuity was associated with greater difficulty on the near-vision ADVS subscale (beta = 0.68, P < 0.01), but not with the overall ADVS or the far-vision or night-driving subscales (P > 0.05). Motion threshold was not associated with the overall ADVS or any of the subscales after controlling for other vision variables, although it was associated when no other vision variables were in the models. CONCLUSIONS: Motion threshold was not independently associated with any ADVS difficulty. Dynamic acuity was independently associated with self-reported difficulty with near-vision tasks only. Other studies should confirm this association. If confirmed, strategies to improve dynamic acuity could be developed to try to reduce difficulty with tasks involving near vision.

Aged↗

PubMed1994

Visual acuity, color vision, and visual search performance at sea.

Visual acuity and color vision were tested during a search and rescue exercise at sea. Fifty-seven watchkeepers searched for orange and yellow life rafts during daylight and for lighted and unlighted life rafts at night with night vision goggles. There were 588 individual watches of one hour each. Measures of wind, waves, and weather were used as covariates. Daytime percentage detection was positively correlated with low-contrast visual acuity and negatively correlated with error scores on Dvorine pseudoisochromatic plates and the Farnsworth color test. Performance was better during the first half-hour of the watch. Efficiency calculations show that color vision selective screening at one standard deviation above the mean would increase daylight search performance by 10% and that one standard deviation visual acuity selection screening would increase performance by 12%. There was no relationship between either acuity or color vision and life raft detection using night vision goggles.

Color Perception↗