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PubMed2004

Visual-visual nonidentity matching assessment: a worthwhile addition to the assessment of basic learning abilities test.

The Assessment of Basic Learning Abilities test (ABLA) is a useful tool for choosing appropriate training tasks for persons with developmental disabilities. This test assesses the ease or difficulty with which persons are able to learn six hierarchically positioned discrimination tasks. A visual-visual nonidentity matching prototype task was examined to assess its (a). relation to the ABLA hierarchy, (b). predictive validity, and (c). test-retest reliability. Results from 23 participants with developmental disabilities suggest that visual-visual nonidentity matching is a worthwhile addition to the ABLA test and is positioned in the ABLA hierarchy above Level 4 (visual-visual identity matching) and below Level 6 (auditory-visual discrimination). The prototype visual-visual nonidentity matching task also demonstrated high predictive validity and test-retest reliability.

Adult↗
PubMed1998

Visual identity matching and auditory-visual matching: a procedural note.

After preliminary computerized training on visual-visual identity matching, a 5-year-old boy with autism (Sam) was given visual-visual and auditory-visual matching-to-sample tests with new stimuli. He did well in matching dictated name samples to 20 pictures, 26 printed upper case letters, and 9 single-digit numbers. In matching the visual stimuli (pictures, letters, or numbers) to themselves, however, he did not perform well. We then increased the number of picture comparisons per trial from two to three. In tests after this three-comparison training, Sam correctly matched on 95% of the original 20-stimulus, four-comparison, identity-matching test trials. He went on to demonstrate accurate identity matching of the numbers, letters, and new pictures. In identity-matching tests on the table top, he performed poorly until the stimulus array was made to resemble the stimulus arrangement on the computer. These findings showed that seemingly small procedural changes can influence performance and demonstrated that successful auditory-visual matching does not guarantee proficiency in visual-visual identity matching.

Auditory Perception↗
PubMed1988

Are visual-perceptual and visual-motor skills separate abilities?

This study explored the independence of visual-perceptual and visual-motor abilities. Scores on the Motor-free Visual Perception Test were correlated by Pearson's method with scores on tests that weight the visual-perceptual, motor, and visual-motor components differently. Small but significant correlations were found between the Motor-free Visual Perception Test and tests of visual-motor integration, but there was no relationship between the motor-free test and tests of motor ability. These findings support the premise that tests of visual perception, visual-motor integration, and motor ability measure different skills.

Child↗
PubMed2000

A comparison of visual acuity, predictability, and visual function outcomes after intracorneal ring segments and laser in situ keratomileusis.

PURPOSE: To compare correction of low myopia by intrastromal corneal ring segments (ICRS) and by laser in situ keratomileusis (LASIK) with respect to early visual recovery and refractive outcomes. METHODS: Eighty-two eyes implanted with ICRS in a phase III study for US Food and Drug Administration review were matched with 133 eyes treated with LASIK by criteria of age (> 18 years, < 65 years), preoperative myopia (-1.00 to -3.50 diopters [D]), astigmatism (< or = 1.00 D), single treatment, and attempted full correction. Examinations were performed preoperatively and postoperatively at days 1 and 7 and months 1 and 3. Visual acuity and manifest refraction data were collected retrospectively. Visual function scores were assigned, and summarized results were compared. RESULTS: Uncorrected visual acuity was 20/20 or better at day 1 in 24% of eyes (20/82) after ICRS and in 55% of eyes (73/133) after LASIK, and at month 3 in 75% of eyes (58/77) after ICRS and in 67% of eyes (84/126) after LASIK. Spherical equivalent refraction at month 3 was within +/- 1.00 D of intended correction in 99% of eyes (76/77) after ICRS and in 96% of eyes (121/126) after LASIK. Excellent visual function scores were noted at month 3 in 90% of eyes (69/77) after ICRS and in 78% of eyes (98/126) after LASIK. CONCLUSION: Patients treated with LASIK showed better uncorrected visual acuity immediately following surgery; however, beyond 1 month, patients treated with ICRS achieved better uncorrected visual acuity that continued to improve with time. Visual function scores indicate that ICRS eyes see at higher levels of uncorrected visual acuity than LASIK eyes do with the same refractive error. The ICRS and LASIK were comparable in the correction of mild myopia.

Cornea↗
PubMed2005

[The influrence of visual acuity and contrast sensitivity on subjective evaluation of visual function before and after cataract surgery].

PURPOSE: To assess the influence of visual acuity and contrast sensitivity on subjective evaluation of visual function investigated by means of questionnaires in patients before and after cataract surgery. METHODS: Visual acuity was tested on Snellen projection optotypes and logMAR optotype chart with Landolt rings, contrast sensitivity was tested on Pelli-Robson chart. The questionnaire included Visual Functioning Index VF-14, Cataract Symptom Score and Global Measures of Vision--self-reported trouble and satisfaction with vision. 37 cataract patients were examined, including completing the questionnaire, 1 day before and 7 weeks after the surgery. RESULTS: Most patients (65%) suffer from moderate troubles with their vision and are moderately dissatisfied (51%) before cataract surgery. After the surgery, a majority of patients have no troubles (51%) and are very satisfied (54%). Visual acuity (VA) correlates only with VF-14, namely only VA of non-operated eye (p < 0.01), binocular VA before (p < 0.001) and after surgery (p < 0.05). Contrast sensitivity (of non-operated eye, operated eye, binocular) correlates with more subjective parameters (VF-14, self-reported trouble and satisfaction with vision), namely both before and after the surgery (p < 0.05, p < 0.01, p < 0.001). CONCLUSION: After cataract surgery, visual acuity, contrast sensitivity and subjective parameters of visual functions significantly improve. Subjective parameters correlate more with contrast sensitivity then with visual acuity. Contrast sensitivity is more related than visual acuity to real world in patients with cataract.

Aged↗
PubMed1990

Molecular and morphological changes in the cat lateral geniculate nucleus and visual cortex induced by visual deprivation are revealed by monoclonal antibodies Cat-304 and Cat-301.

Monoclonal antibody Cat-301 recognizes a surface-associated proteoglycan on subsets of neurons in the mammalian CNS (Hockfield and McKay, 1983). The expression of Cat-301 immunoreactivity on Y cells in the cat LGN is sharply reduced by early visual deprivation (Sur et al., 1988). We employed an immunosuppression strategy (Hockfield, 1987) to further study alterations in the expression of experience-dependent molecules. Newborn BALB/c mice were injected with LGN from dark-reared cats to induce a suppression of the immune response to antigens expressed in visually deprived animals. These mice were then immunized with LGN from normal cats to elicit an immune response to antigens with an expression dependent on normal early visual experience. This strategy permitted the generation of monoclonal antibody Cat-304, which recognizes a surface-associated antigen on neuronal cell bodies and proximal dendrites, and which appears histologically identical to Cat-301. Further analyses show that Cat-304 and Cat-301 recognize different epitopes on the same 680-kDa chondroitin sulfate proteoglycan. We examined the effects of early visual deprivation on Cat-304 immunoreactivity in the LGN and visual cortex of cats. In LGN from normal cats, Cat-304 labels neurons in layers A, A1, and C, in interlaminar zones, and in the medial interlaminar nucleus. In LGN from dark-reared cats, the number of antibody-positive neurons is markedly reduced, and the cross-sectional area of the remaining positive neurons is smaller than normal. In cortical area 17 of normally reared cats, Cat 304-positive neurons are densely distributed in 2 bands, in layers IV and V/VI. Labeled neurons are also present in layers II and III. In area 17 of dark-reared cats, the number of antibody-positive neurons is reduced. The reduction in the number of labeled neurons is most pronounced in layers II/III and V/VI. Antibody-positive neurons are smaller in all cortical layers of dark-reared cats. The changes in the expression of Cat-301 immunoreactivity in dark-reared visual cortex and LGN are identical to those of Cat-304. The laminar differences in the effect of dark rearing on Cat-301 and Cat-304 expression in the visual cortex provides support for the suggestion that layer IV of cortical area 17 may be less susceptible to prolongation of plasticity by dark rearing than layers II/III and V/VI. Further, the biochemical and histological studies reported provide evidence that early visual experience regulates protein expression in the cat LGN and visual cortex.

Animals↗
PubMed1997

Visual vestibular interaction in the dynamic visual acuity test during voluntary head rotation.

BACKGROUND: Although intact vestibular function is indispensable to maintaining spatial orientation, no good screening tests of vestibular function are implemented in the aviation community. High frequency voluntary head rotation was selected as a vestibular stimulus to isolate the vestibulo-ocular reflex (VOR) from visual influence. METHOD: A dynamic visual acuity test that incorporates voluntary head rotation was evaluated as a potential vestibular function screening tool: 27 normal subjects performed voluntary sinusoidal head rotation at frequencies from 0.7-4 Hz under 3 different visual conditions: visually-enhanced VOR, normal VOR, and visually suppressed VOR. Standardized Bailey-Lovie chart letters were presented on a computer monitor in front of the subject, who then was asked to read the letters while rotating his head horizontally. The electro-oculogram and dynamic visual acuity score were recorded and analyzed. RESULTS: There was no significant difference in gain or phase shift among 3 visual conditions in the frequency range 2.8-4 Hz. The dynamic visual acuity score shifted less than 0.3 log MAR at frequencies under 2.0 Hz. CONCLUSION: The dynamic visual acuity test at frequencies around 2 Hz can be recommended for evaluating vestibular function.

Adult↗
PubMed1999

Distance and near visual acuity, contrast sensitivity, and visual fields of 10-year-old children.

OBJECTIVE: To measure monocular distance visual acuity, near visual acuity, contrast sensitivity, and visual field extent in full-term, 10-year-old children tested according to the protocol used to test 10-year-old preterm children in the Cryotherapy for Retinopathy of Prematurity study. SUBJECTS AND METHODS: Subjects were 106 healthy, full-term children, 9.8 to 10.9 years of age, who had no ocular abnormalities other than ametropia. All were tested monocularly using Early Treatment and Diabetic Retinopathy Study distance and near visual acuity charts and Pelli-Robson contrast sensitivity charts, with refractive error corrected according to Cryotherapy for Retinopathy of Prematurity study criteria. Goldmann perimetry was tested without correction using the V-4-e and III-4-e stimuli along 8 meridia. A standard pediatric eye examination was performed on each subject. RESULTS: Mean (SD) distance visual acuity was 20/19.6 OD (0.082 log unit [lu]) and mean near visual acuity was 20/19.5 OD (0.100 lu). Mean (SD) contrast sensitivity was 1.69 OD (0.12 lu), with a mean (SD) of 36.4 (2.2) letters read. Visual field extent was larger for the V-4-e stimulus than for the III-4-e stimulus. CONCLUSIONS: The results provide the first monocular normative data from a large sample of 10-year-old children tested with Early Treatment and Diabetic Retinopathy Study distance and near visual acuity charts and the Pelli-Robson contrast sensitivity charts, and add to the literature on Goldmann perimetry in children.

Child↗
PubMed1991

Detection of hidden visual loss in multiple sclerosis. A comparison of pattern-reversal visual evoked potentials and contrast sensitivity.

The detection of hidden visual loss is important in establishing the diagnosis of multiple sclerosis, especially in patients who have neurologic symptoms of the disease. Both visual evoked potentials and contrast sensitivity have been used for this purpose. We compared the sensitivities of pattern-reversal visual evoked potentials and contrast sensitivity, measured with the Vistech VCTS 6500 chart, in detecting hidden visual loss in 18 patients with multiple sclerosis whose visual acuity was correctable to 20/20 (6/6) or better in the examined eye. Thirteen patients had delayed visual evoked potential latencies. An additional four patients had reduced P100 amplitudes without prolonged latencies. Nine patients had abnormal contrast sensitivity. The visual evoked potential was more sensitive than contrast sensitivity at detecting hidden visual loss in patients with multiple sclerosis (p less than 0.01).

Adult↗
PubMed1986

The influence of visual field disorders on visual identification tasks.

Visual identification of shapes, figures, objects and faces was tested in a group of 26 patients with homonymous field defects due to unilateral "posterior" brain damage. In addition, a search test was used for evaluation of the effect of visual field loss on visual information acquisition. Of the patients, 5 performed entirely normally, i.e. errorless and within age-matched time limits, in all tests. The majority of patients (n = 15) also performed correctly but required significantly more time than normals. In contrast, 6 patients showed a rather specific impairment in visual identification tasks. It is argued that visual field loss per se does not impair visual identification but may affect visual search and, thus, information acquisition. Visual identification may be impaired, however, if brain damage involves the inferotemporal cortex.

Adult↗
PubMed1980

The organization of the visual hyperstriatum in the domestic chick. I. Topology and topography of the visual projection.

The organization of the visual projection to the hyperstriatum, or Wulst, in the domestic chick has been investigated using extracellular recording with microelectrodes. The entire visual field of the contralateral eye projects retinotopically into the Wulst. The superior and inferior margins of the visual field are represented, respectively, in the posterior and anterior regions of the visual projection area. The projection of the nasal and temporal margins of the visual field is more complex, the superior and inferior parts of the temporal hemi-field being represented in the superficial and deep regions of the Wulst respectively, with an intervening projection of the nasal hemi-field at an intermediate depth. Visually responsive units appear to be restricted to the accessory hyperstriatum (HA) and possibly also to a narrow, medial region of the intercalated nucleus (HIS). Visual-evoked activity was never detected in the dorsal hyperstriatum (HD) or ventral hyperstriatum (HV). The organization found in the chick is discussed in relation to the previous physiological and anatomical findings of other workers in the visual Wulst of the pigeon and the owl.

Animals↗
PubMed1993

Visual object agnosia, prosopagnosia, achromatopsia, loss of visual imagery, and autobiographical amnesia following recovery from cortical blindness: case M.H.

A number of higher visual deficits accompanied by severe retrograde autobiographical memory loss following bilateral medial occipital infarctions are described in case M.H. Assessment of M.H.'s visual object agnosia and prospagnosia suggested that he was unable to integrate the elements of a percept to form a meaningful whole. This deficit may occur at the level the percept is encoded into the visual buffer and inspected. M.H. also describes a loss of visual memories, and it is hypothesized that this may similarly be a result of an inability to integrate the elements of the visual representation (e.g. of an object or face) following its generation from long-term visual memory store into the visual buffer. M.H.'s retrograde autobiographical memory loss is postulated to be a consequence of the severe impoverishment of episodic memories that must occur when events originally stored multimodally, must be recalled without any visual component.

Adult↗
PubMed2001

Cause-specific prevalence of bilateral visual impairment in Victoria, Australia: the Visual Impairment Project.

PURPOSE: To study the cause-specific prevalence of eye diseases causing bilateral visual impairment in Australian adults. DESIGN: Two-site, population-based cross-sectional study. PARTICIPANTS: Participants were aged 40 years and older and resident in their homes at the time of recruitment for the study. The study was conducted during 1992 through 1996. METHODS: The study uses a cluster stratified random sample of 4744 participants from two cohorts, urban, and rural Victoria. Participants completed a standardized interview and eye examination, including presenting and best-corrected visual acuity, visual fields, and dilated ocular examination. The major cause of vision loss was identified for all participants found to be visually impaired. Population-based prevalence estimates are weighted to reflect the age and gender distribution of the two cohorts in Victoria. MAIN OUTCOME MEASURES: Visual impairment was defined by four levels of severity on the basis of best-corrected visual acuity or visual field: <6/18 > or =6/60 and/or <20 degrees > or =10 degrees radius field, moderate vision impairment; severe vision impairment, <6/60 > or =3/60 and/or <10 degrees > or =5 degrees radius field; and profound vision impairment <3/60 and/or <5 degrees radius field. In addition, less-than-legal driving vision, <6/12 > or =6/18, and/or homonymous hemianopia were defined as mild vision impairment. In Australia, legal blindness includes severe and profound vision impairment. RESULTS: The population-weighted prevalence of diseases causing less-than-legal driving or worse impairment in the better eye was 42.48/1000 (95% confidence interval [CI], 30.11, 54.86). Uncorrected refractive error was the most frequent cause of bilateral vision impairment, 24.68/1000 (95% CI, 16.12, 33.25), followed by age-related macular degeneration (AMD), 3.86/1000 (95% CI, 2.17, 5.55); other retinal diseases, 2.91/1000 (95% CI, 0.74, 5.08); other disorders, 2.80/1000 (95% CI, 1.17, 4.43); cataract, 2.57/1000 (95% CI, 1.38, 3.76); glaucoma, 2.32/1000 (95% CI, 0.72, 3.92); neuro-ophthalmic disorders, 1.80/1000 (95% CI, 0, 4.11); and diabetic retinopathy, 1.53/1000 (95% CI, 0.71, 2.36). The prevalence of legal blindness was 5.30/1000 (95% CI, 3.24, 7.36). Although not significantly different, the causes of legal blindness were uncorrected refractive errors, AMD, glaucoma, other retinal conditions, and other diseases. CONCLUSIONS: Significant reduction of visual impairment may be attained with the application of current knowledge in refractive errors, diabetes mellitus, cataract, and glaucoma. Although easily preventable, uncorrected refractive error remains a major cause of vision impairment.

Adult↗
PubMedDate not supplied

Visual aftereffects and the consequences of visual system lesions on their perception in the rhesus monkey.

This study examined the consequences of visual system lesions on visual aftereffects produced by achromatic stimuli of various luminance contrasts and chromatic stimuli of various wavelength compositions. The effects of repeated exposure to such adapting stimuli were assessed using probes whose luminance contrast and wavelength composition were systematically varied using both detection and discrimination paradigms. Interocular tests revealed that both peripheral and central mechanisms contribute to the visual aftereffects produced by the adapting stimulus arrays used in this study. Contrary to the hypothesis according to which the midget system of the retina is the conveyor of visual afterimages, we found that blocking this system with lesions of parvocellular lateral geniculate nucleus, through which the midget cells make their way to the striate cortex in primates, did not eliminate the visual aftereffects. It appears therefore that the parasol system of the retina, which courses through the magnocellular layers of the lateral geniculate nucleus to cortex, can convey the necessary signals for the generation of visual aftereffects. Lesions of areas V4 and MT did not have significant effects on the visual aftereffects studied suggesting that the central factors that contribute to the visual aftereffects occur either already in area V1 or are conveyed to higher centers through regions other than areas V4 and MT.

Adaptation, Ocular↗
PubMed1988

[Behavior of visual acuity, visual fields and contrast sensitivity in simulated cataract].

Visual acuity, contrast sensitivity, and visual fields were examined with and without occluders both in a group of healthy subjects and in a group of patients with field defects (mostly caused by glaucoma). The various results were compared with one another as well as with the results obtained from a group of cataract patients examined before and after surgery. The results confirm clinical experience: visual acuity enables some conclusions to be drawn on the degree and progression of opacity of a lens. The changes in contrast sensitivity and in the visual field, however, represent rather the quality of the visual degradation. Contrast sensitivity and diffuse alterations in the visual field have similar progression patterns. The alterations in contrast sensitivity are more pronounced at higher frequency levels. The contrast sensitivity test can be recommended as a simple and complementary functional test, particularly on cataract patients with severe complaints and relatively good visual acuity. The results of occlusive experiments afford some practical conclusions which enhance knowledge and differentiation of visual field changes induced by cataract and glaucoma. These conclusions can provide a basis for further and more detailed investigations.

Adult↗
PubMed1991

Flashed pattern-induced activity in the visual system: I. The short latency evoked response recorded from the cat visual cortex.

Previous methods for estimating visual acuity have used the visual evoked response conventionally the late visual evoked response components or the steady-state potential. The present experiments were undertaken to evaluate the possible use of short latency flashed pattern evoked responses in estimating pattern dependent activity in the cat visual system. Recordings were made from the skull bone and the dura above the primary visual cortex and intracortically. The visual evoked responses to patterned (checks) and non-patterned light flashes of high intensity and short duration were recorded. The visual evoked response activity recorded from the cortical surface had an onset latency of 14-15 ms. The initial positive-negative potential sequences of the responses were similar for patterned and non-patterned stimuli, however a difference was recorded from 35-40 ms after stimulus. The smallest check size which separated a pattern from a non-pattern VER was in the order of 10 min of arc. The results indicate that the short-latency cortical VER may be used to estimate visual resolution.

Animals↗
PubMed1987

Are flash-evoked visual potentials useful for intraoperative monitoring of visual pathway function?

Flash-evoked visual potentials (VEPs) recorded from the scalp were used in a series of 35 patients with tumors along the visual pathway: 3 orbital tumors, 25 perisellar tumors, 4 intraventricular tumors, and 3 occipital lesions. Preoperatively, various combinations of impaired visual fields and visual acuity were observed in over 90% of the patients. A postoperative decrease in visual function was observed in 3 cases. Of the 25 perisellar lesions, 13 were operated through a standard frontotemporal craniotomy and 12 were operated through a transnasal-transsphenoidal approach. VEPs were highly susceptible to volatile anesthetics, and there was a significant incidence of spontaneous latency increases and amplitude decreases in a large number of patients. There was an unacceptably high number of cases with significant VEP alteration occurring without concomitant visual function change. During trepanation or the transnasal approach, a reversible potential loss was observed in 11 patients, a profoundly altered wave form was seen in 8 cases, and a loss of single peaks was observed in 15 patients. During dissection of the tumor, a reversible potential loss or a potential with unidentifiable peaks was found in 25 cases; however, the VEPs recovered during closure or in the recovery room. There was no correlation between intraoperative VEP changes and the postoperative changes in visual function. In only 1 patient with an insignificant postoperative decrease in visual acuity from 0.4 to 0.3 was there a concomitant intraoperative potential loss. The major conclusion of our findings is that light-emitting diode flash-evoked VEPs demonstrate intraoperative changes that appear too early and too prominently to be caused solely by manipulation of the optic pathways.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2006

Enduring critical period plasticity visualized by transcranial flavoprotein imaging in mouse primary visual cortex.

Experience-dependent plasticity in the visual cortex was investigated using transcranial flavoprotein fluorescence imaging in mice anesthetized with urethane. On- and off-responses in the primary visual cortex were elicited by visual stimuli. Fluorescence responses and field potentials elicited by grating patterns decreased similarly as contrasts of visual stimuli were reduced. Fluorescence responses also decreased as spatial frequency of grating stimuli increased. Compared with intrinsic signal imaging in the same mice, fluorescence imaging showed faster responses with approximately 10 times larger signal changes. Retinotopic maps in the primary visual cortex and area LM were constructed using fluorescence imaging. After monocular deprivation (MD) of 4 d starting from postnatal day 28 (P28), deprived eye responses were suppressed compared with nondeprived eye responses in the binocular zone but not in the monocular zone. Imaging faithfully recapitulated a critical period for plasticity with maximal effects of MD observed around P28 and not in adulthood even under urethane anesthesia. Visual responses were compared before and after MD in the same mice, in which the skull was covered with clear acrylic dental resin. Deprived eye responses decreased after MD, whereas nondeprived eye responses increased. Effects of MD during a critical period were tested 2 weeks after reopening of the deprived eye. Significant ocular dominance plasticity was observed in responses elicited by moving grating patterns, but no long-lasting effect was found in visual responses elicited by light-emitting diode light stimuli. The present results indicate that transcranial flavoprotein fluorescence imaging is a powerful tool for investigating experience-dependent plasticity in the mouse visual cortex.

Animals↗