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PubMed1988

Experimentally induced visual projections into auditory thalamus and cortex.

Retinal cells have been induced to project into the medial geniculate nucleus, the principal auditory thalamic nucleus, in newborn ferrets by reduction of targets of retinal axons in one hemisphere and creation of alternative terminal space for these fibers in the auditory thalamus. Many cells in the medial geniculate nucleus are then visually driven, have large receptive fields, and receive input from retinal ganglion cells with small somata and slow conduction velocities. Visual cells with long conduction latencies and large contralateral receptive fields can also be recorded in primary auditory cortex. Some visual cells in auditory cortex are direction selective or have oriented receptive fields that resemble those of complex cells in primary visual cortex. Thus, functional visual projections can be routed into nonvisual structures in higher mammals, suggesting that the modality of a sensory thalamic nucleus or cortical area may be specified by its inputs during development.

Afferent Pathways↗

PubMed1989

[Effect of carteolol and timolol eyedrops on the pressure tolerance of the optic nerve head].

In a planned, randomized, double blind study ocular perfusion pressures were measured before and after a 3-day regimen of 2% carteolol hydrochloride or 0.5% timolol maleate. A pressure tolerance test was also carried out. The results of this test revealed the critical pressure: it is the artificially increased intraocular pressure at which the visual function (monitored by visually evoked cortical potentials) is reduced to 20% of its initial value. The ocular perfusion pressures are affected by both drugs. They are more clearly reduced by carteolol than by timolol. The critical pressure is affected by both drugs too. After application of carteolol, the critical pressure is clearly lower than after application of timolol. The difference is statistically significant (p less than 0.05).

Adaptation, Physiological↗

PubMed2006

Spatial localization in visual impairment.

PURPOSE: To investigate self-reported difficulties experienced by visually impaired subjects in real-world tasks requiring judgment of space and distance and to determine whether laboratory measures of spatial localization predict self-reported difficulty with spatial tasks better than traditional measures of visual function, such as visual acuity and contrast sensitivity. METHODS: Forty-two subjects with visual impairment participated. The Spatial Localization Questionnaire (SLQ) was developed to investigate self-reported spatial localization difficulties, and subjects answered the questionnaire as part of the study. Subjects also completed a variety of clinical vision tests (visual acuity, contrast sensitivity, stereo acuity, and reading speed) and laboratory vision tests (vernier acuity, bisection acuity, and visual direction). RESULTS: The SLQ was found to have good validity. Several significant correlations were found between the Rasch analysis ability scores for the questionnaire and the clinical and laboratory vision tests. Using stepwise regression analysis, we found that vernier acuity and contrast sensitivity accounted for 42% of the variance in the Rasch scores (P < 0.001). CONCLUSIONS: The findings indicate that certain subjects with visual impairment have difficulty with real-world spatial tasks, as indicated by the SLQ. Of note, these difficulties were better predicted by vernier acuity (a resolution test) and contrast sensitivity, rather than vernier or bisection bias, which measure localization.

Adult↗

PubMed2006

Sweep visual evoked potential grating acuity thresholds paradoxically improve in low-luminance conditions in children with cortical visual impairment.

PURPOSE: Children with cortical or cerebral visual impairment (CVI) often experience photophobia. In a study conducted to test whether this clinical phenomenon affects visual function, the sweep visual evoked potential (VEP) was used to evaluate cortical responses to grating stimuli in two luminance conditions: low and normal. METHODS: Twenty children (age range, 7 months to 4 years 10 months) with CVI and 17 age-matched control subjects were examined. Testing conditions consisted of a swept grating stimulus shown against a normal background luminance (109 cd/m2) and against a low-luminance background (20 cd/m2). Thresholds in these two luminance conditions were compared. Response amplitudes across the spatial frequency domain were also compared. RESULTS: Children with CVI paradoxically have improved grating acuity thresholds when the stimulus is shown using a low-luminance background (P=0.006). Response amplitudes are also increased in low luminance. In control children, luminance had no significant effect on response amplitudes or thresholds. CONCLUSIONS: Increased luminance causes a worsening of acuity thresholds in children with CVI. Response amplitudes are also diminished in normal luminance. This finding has implications for optimal viewing and learning conditions for children with CVI.

Blindness, Cortical↗

PubMed2005

Relationship between visual field loss and contrast threshold elevation in glaucoma.

BACKGROUND: There is a considerable body of literature which indicates that contrast thresholds for the detection of sinusoidal grating patterns are abnormally high in glaucoma, though just how these elevations are related to the location of visual field loss remains unknown. Our aim, therefore, has been to determine the relationship between contrast threshold elevation and visual field loss in corresponding regions of the peripheral visual field in glaucoma patients. METHODS: Contrast thresholds were measured in arcuate regions of the superior, inferior, nasal and temporal visual field in response to laser interference fringes presented in the Maxwellian view. The display consisted of vertical green stationary laser interference fringes of spatial frequency 1.0 c deg(-1) which appeared in a rotatable viewing area in the form of a truncated quadrant extending from 10 to 20 degrees from fixation which was marked with a central fixation light. Results were obtained from 36 normal control subjects in order to provide a normal reference for 21 glaucoma patients and 5 OHT (ocular hypertensive) patients for whom full clinical data, including Friedmann visual fields, had been obtained. RESULTS: Abnormally high contrast thresholds were identified in 20 out of 21 glaucoma patients and in 2 out of 5 OHT patients when compared with the 95% upper prediction limit for normal values from one eye of the 36 normal age-matched control subjects. Additionally, inter-ocular differences in contrast threshold were also abnormally high in 18 out of 20 glaucoma patients who had vision in both eyes compared with the 95% upper prediction limit. Correspondence between abnormally high contrast thresholds and visual field loss in the truncated quadrants was significant in 5 patients, borderline in 4 patients and absent in 9 patients. CONCLUSION: While the glaucoma patients tested in our study invariably had abnormally high contrast thresholds in one or more of the truncated quadrants in at least one eye, reasonable correspondence with the location of the visual field loss only occurred in half the patients studied. Hence, while contrast threshold elevations are indicative of glaucomatous damage to vision, they are providing a different assessment of visual function from conventional visual field tests.

Adult↗

PubMed2006

Explicit criteria for prioritization of cataract surgery.

BACKGROUND: Consensus techniques have been used previously to create explicit criteria to prioritize cataract extraction; however, the appropriateness of the intervention was not included explicitly in previous studies. We developed a prioritization tool for cataract extraction according to the RAND method. METHODS: Criteria were developed using a modified Delphi panel judgment process. A panel of 11 ophthalmologists was assembled. Ratings were analyzed regarding the level of agreement among panelists. We studied the effect of all variables on the final panel score using general linear and logistic regression models. Priority scoring systems were developed by means of optimal scaling and general linear models. The explicit criteria developed were summarized by means of regression tree analysis. RESULTS: Eight variables were considered to create the indications. Of the 310 indications that the panel evaluated, 22.6% were considered high priority, 52.3% intermediate priority, and 25.2% low priority. Agreement was reached for 31.9% of the indications and disagreement for 0.3%. Logistic regression and general linear models showed that the preoperative visual acuity of the cataractous eye, visual function, and anticipated visual acuity postoperatively were the most influential variables. Alternative and simple scoring systems were obtained by optimal scaling and general linear models where the previous variables were also the most important. The decision tree also shows the importance of the previous variables and the appropriateness of the intervention. CONCLUSION: Our results showed acceptable validity as an evaluation and management tool for prioritizing cataract extraction. It also provides easy algorithms for use in clinical practice.

Activities of Daily Living↗

PubMed2002

Retinal Vessel Analysis--new possibilities.

Retinal Vessel Analysis is a new technique to assess behavior of large retinal vessels based on diameter measurements. The Retinal Vessel Analyzer (RVA) measures continuously on-line obtaining data in relation to time and local position. Possible analysis tools include (a) Time Course Analysis of physiological, pathological, or therapy induced changes; (b) Local Course Analysis to recognize local narrow or wide vessel segments along the vessel; (c) Vasomotoric Analysis to determine vasomotions and blood pressure related diameter changes; (d) Functional Analysis to examine dynamic behavior e.g. the ability to autoregulate and (e) Functional Imaging to visualize functional parameters of vessels in single vessel segments. RVA is thus able to recognize and study different autoregulation mechanisms.

Fluorescein Angiography↗

PubMed1974

Phase relationships of alpha rhythm in man.

Stationary phase relationships of human scalp EEGs in the frequency range of the alpha rhythm were examined by the method of cross-spectral analysis. EEGs were recorded from midsaggital points equally spaced on the scalp in normal and blind adults. Cross-spectral analysis was applied to one- or three-minute records and to successive q0-second records. The generalized component, which usually formed a dominant peak in the EEG spectra, showed a gradual phase advance toward the frontal region but seldom reached 180 degrees, and the phase shift at intermediate points was not linearly related to the distance between them. A parallel relation was confirmed between the increase in the inter-regional phase difference and the decrease in the coherence value. A variety of phase differences was noticed for the more localized subordinate component, and the angles of this component ranged more broadly than with the generalized dominant component. Phase relations of the alpha rhythm in the blind were similar to those of the localized component in normal subjects. Thus, in respect to inter-regional relationships in the antero-posterior direction, the alpha rhythms were classified into at least two types, one closely related to the visual function and the other depending upon some functions other than visual. Effectiveness of the cross-spectral analysis on phase relations of the EEG was discussed in comparison with other methods.

Adolescent↗

PubMed2000

Bilateral occipital lobe stroke with inferior altitudinal defects.

BACKGROUND: Cerebrovascular disease is the most common cause of neurological disability in Western countries. Patients who survive cerebrovascular accidents exclusive to the occipital lobe often have no significant neurological deficits other than visual-field loss. Visual-field defects from occipital lobe stroke typically include congruous homonymous hemianopsias or quadranopsias, with or without macular sparing. CASE REPORT: A 61-year-old white man came to us with symptoms of sudden loss of vision and difficulty reading. Visual-field testing revealed a bilateral inferior altitudinal defect with normal optic nerve and fundus appearance in both eyes. On radiological examination, he was found to have had a bioccipital lobe cerebrovascular accident secondary to complete occlusion of the left vertebral artery. An embolic event causing the artery occlusion, in combination with bilaterally compromised cerebellar and posterior cerebral arteries, presumably caused the bilateral stroke. After appropriate medical and neurological consultation, optometric management consisted of maximizing the patient's remaining vision with a prismatic spectacle correction. DISCUSSION/CONCLUSION: Patients with infarction exclusive to the occipital lobe typically have no other neurological deficits except visual-field loss and are often easier to manage than patients with infarctions to other areas of the cerebral cortex or multiple infarctions. Visual-field loss from occipital lobe damage can be successfully managed with optical systems and/or visual rehabilitation. Factors related to management include location and extent of visual-field damage, functional visual needs, and both personal and health concerns of the patient. A discussion is presented on cerebrovascular disease, occipital lobe infarction, imaging techniques, and visual rehabilitation.

Diagnosis, Differential↗

PubMed2001

Visual performance of rigid gas permeable contact lenses in patients with corneal opacity.

PURPOSE: To evaluate the visual performance of rigid gas permeable (RGP) contact lenses in patients with nebular and nebulo-macular corneal opacity and correlate the improvement in visual acuity with other visual parameters. METHODS: In a prospective study, visual performance of RGP contact lenses was evaluated in eyes with corneal opacity involving the pupillary area. The baseline visual acuity and other visual parameters with glasses were compared with those recorded with RGP contact lenses. The visual functions evaluated were visual acuity, contrast sensitivity, glare acuity, and mesopic vision. Binocular status with RGP contact lenses was assessed. All patients were followed up for 3 months. RESULTS: Twenty-eight eyes (26 patients) with nebular or nebulo-macular corneal opacity were included in this study. All eyes (100%) achieved significantly better visual performance with RGP contact lenses than with glasses (P< 0.0020). Visual acuity of 6/9 or better was achieved in 50% of patients with RGP contact lenses compared to none with glasses. RGP contact lenses improved the visual acuity by 0.27 decimals over the baseline value with glasses, butthe improvement for mesopic vision and glare acuity was significantly lower at 0.15 and 0.06 decimals respectively. Similarly, contrast sensitivity did not improve to the same extent as visual acuity. Stereopsis was present only in patients with best corrected visual acuity of 6/9 or better with RGP lenses. CONCLUSION: RGP contact lenses improved the visual acuity and other visual performance in patients with reduced vision due to nebular or nebulo-macular corneal opacity. However, contrast sensitivity, glare acuity, and mesopic vision did not improve to the same extent as visual acuity.

Adolescent↗

PubMed1992

[Surgical decompression of the optic nerve in intracanal injuries. Indications and results].

Fifteen patients with traumatic optic neuropathy (anatomical section excluded) underwent surgical anterior decompression of the optic nerve, via the trans ethmoid-sphenoid approach. Improvement of visual function assessed by visual acuity and visual field measurements, was obtained in 10 patients. Results remained stable for a follow-up period of at least 6 months. There was a delay of several weeks before improvement in some of the patients. Thus a long follow-up period seems recommended. Trans ethmoid-sphenoid optic nerve decompression is a reliable procedure with low morbidity, and represents a promising therapy for indirect injuries of the optic nerve.

Adolescent↗

PubMed1989

[The treatment of retinal vein thrombosis by puncture of the anterior chamber].

Repeated anterior chamber punctures in patients with old (more than one month) retinal vein thrombosis allowed to achieve a rise of visual acuity in 10 of 15 patients. In remote terms (after four months) further improvement of visual functions was recorded, visual acuity increased by 0.3-0.6 in 8 of 15 patients. In the process of treatment, no complications were observed. Repeated anterior chamber punctures can be recommended as a method of choice for treatment of this pathology.

Anterior Chamber↗

PubMed1989

[The symptom of congestive optic disks in the benign intracranial hypertension syndrome].

Observations over 28 patients with benign intracranial hypertension, aged from 15 to 50 years, of them 25 women and 3 men, have shown that among possible etiologic factors of benign intracranial hypertension there appeared to be pregnancy in 19 women, respiratory infection--in 3 patients, climacterium--in 2, hypothyrosis--in 2, galactorrhea-amenorrhea--in 1, mild craniocerebral trauma--in 1; 75% of patients had excessive body mass. Among main symptoms of benign intracranial hypertension there were head pains (100%), congestive optic discs (100%), rise of csf pressure (87.5%), nausea and vomiting (80%). In a part of patients there was obnubilation (7), nystagmus (4), damage of the abducent nerve (4), retro-orbital pains (3), transient disturbances of visual functions (fall of visual acuity in 5, defects of visual field in 5). In I woman amaurosis in both eyes remained. The duration of the disease varied from 2 months to 2 years. In 3 women there were recurrences of benign intracranial hypertension.

Adolescent↗

PubMed1982

Optic atrophy induced by vincristine.

Bilateral optic atrophy developed in a 15-year-old patient receiving concomitant neuraxis radiation therapy and weekly vincristine sulfate for medulloblastoma. Other neurologic manifestations that have been associated with vincristine therapy, including inappropriate secretion of antidiuretic hormone, hypertension, confusion, and a severe peripheral neuropathy, were also observed. Neither increased intracranial pressure nor active tumor was identified. Recovery of visual function followed discontinuation of vincristine. Other neurotoxicities also reversed with drug withdrawal. Visual loss occurring in a patient receiving vincristine should alert the physician to the possibility that the process is drug related. This complication may be more likely in patients receiving concomitant or previous cranial radiation therapy. Other central neurotoxicities of vincristine may also be accentuated by neuraxis radiation. It is recommended that vincristine be discontinued in this situation if an aggressive search for a structural anatomic lesion in the optic mechanism is unrevealing, as the prognosis for recovery of visual function appears excellent.

Adolescent↗

PubMed1994

[Biological effects on premature neonates of a milk formula enriched with alpha-linolenic acid: a multicenter study].

Nervous tissues and the retina are rich in docosahexaenoic acid [DHA, C22: 6(n-3)], an essential fatty acid which is the product of the elongation and desaturation of alpha-linolenic acid [alpha-LnA, C18:3(n-3)]. Lower plasma and membrane DHA levels as well as impaired nervous function (psychomotor development, visual disturbances) have been observed in premature babies receiving standard milk products compared to breast-fed babies and have been related to the lack of long-chain (> C20) fatty acids in these products. In the present study, we have investigated whether it is possible to increase the plasma and erythrocyte DHA level in premature infants by giving them a milk formula enriched in alpha-LnA (1.95% vs 0.55%). Results showed that, after 15 days of feeding, alpha-LnA supplementation significantly increased plasma DHA availability [2.20 vs 1.54% (p < 0.0001) in the plasma phospholipids] and increased DHA level in erythrocyte membranes [3.02 vs 2.54% (n.s.) in the red blood cell phosphatidylethanolamines]. At the LA/alpha-LnA ratio used (6/1), there was only a limited impact on the n-6 pathway which was reflected in a slight decrease in the arachidonic acid (AA) of the plasma phospholipids [6.88 vs 7.53% (p < 0.05) after 15 days]. Furthermore, the AA content of the red blood cell phosphatidylethanolamines was perfectly preserved even after a mean period of 4-5 weeks of feeding [(15.70 vs 14.86% (n.s)]. The observed enhancement in fatty acids of the n-3 series calls for a prospective study investigating whether these improvements are associated with changes in the kinetics of psychomotor development and in the visual function of enriched-formula-fed versus breast-fed babies.

Humans↗

PubMed1998

[Correctional aspects of anisometropia in railway machine operators].

The authors assessed occupationally significant visual functions in anisometropy varying in type and degree. Disorders of occupationally significant visual functions depend reliably on anisometropy degree. Correction of anisometropy with recovered vision and binocular functions restores all parameters of night and color vision. Optic and operative correction of anisometropy could be used for rehabilitation of railway machine operators with long length of service. The article provides recommendations to use intraocular lenses for artiphakia in railway machine operators.

Anisometropia↗

PubMed1992

Magnetic resonance imaging mapping of brain function. Human visual cortex.

Magnetic resonance imaging (MRI) studies of human brain activity are described. Task-induced changes in brain cognitive state were measured using high-speed MRI techniques sensitive to changes in cerebral blood volume (CBV), blood flow (CBF), and blood oxygenation. These techniques were used to generate the first functional MRI maps of human task activation, by using a visual stimulus paradigm. The methodology of MRI brain mapping and results from the investigation of the functional organization and frequency response of human primary visual cortex (V1) are presented.

Brain Mapping↗

PubMed2005

Forward genetic analysis of visual behavior in zebrafish.

The visual system converts the distribution and wavelengths of photons entering the eye into patterns of neuronal activity, which then drive motor and endocrine behavioral responses. The gene products important for visual processing by a living and behaving vertebrate animal have not been identified in an unbiased fashion. Likewise, the genes that affect development of the nervous system to shape visual function later in life are largely unknown. Here we have set out to close this gap in our understanding by using a forward genetic approach in zebrafish. Moving stimuli evoke two innate reflexes in zebrafish larvae, the optomotor and the optokinetic response, providing two rapid and quantitative tests to assess visual function in wild-type (WT) and mutant animals. These behavioral assays were used in a high-throughput screen, encompassing over half a million fish. In almost 2,000 F2 families mutagenized with ethylnitrosourea, we discovered 53 recessive mutations in 41 genes. These new mutations have generated a broad spectrum of phenotypes, which vary in specificity and severity, but can be placed into only a handful of classes. Developmental phenotypes include complete absence or abnormal morphogenesis of photoreceptors, and deficits in ganglion cell differentiation or axon targeting. Other mutations evidently leave neuronal circuits intact, but disrupt phototransduction, light adaptation, or behavior-specific responses. Almost all of the mutants are morphologically indistinguishable from WT, and many survive to adulthood. Genetic linkage mapping and initial molecular analyses show that our approach was effective in identifying genes with functions specific to the visual system. This collection of zebrafish behavioral mutants provides a novel resource for the study of normal vision and its genetic disorders.

Animals↗

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