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At least 1,423 records · Page 79Linked to original sources
PubMed2002

Monochromatic aberrations of human eyes in the horizontal visual field.

We measured the monochromatic aberrations of five subjects' right eyes both temporally and nasally out to 40 degrees from fixation. We used a Hartmann-Shack sensor with modifications to equipment and software to enable off-axis measurements. Results were standardized for 6-mm pupils. There was considerable variation among subjects in the pattern of aberrations. Aberrations were generally greater in the nasal visual field than in the temporal visual field; in the case of third-order aberrations, this was true for all subjects. The contribution of third-order Zernike aberrations to the root-mean-square aberration increased up to four times from the center to the edge of the field, but the contribution of fourth- to sixth-order Zernike aberrations varied little across the visual field. Results were similar to those of a previous investigation using laser ray tracing and were of the order of those predicted by Navarro's finite schematic eye.

Comment↗
PubMed2006

Correlations between retinal nerve fiber layer and visual field in eyes with nonarteritic anterior ischemic optic neuropathy.

PURPOSE: To evaluate correlations between retinal nerve fiber layer (RNFL) thickness with visual field (VF) sensitivities in eyes with nonartertic anterior ischemic optic neuropathy (NAION). DESIGN: Case-control study in an academic, institutional setting. METHODS: One eye from 21 patients with NAION and 32 healthy participants were included in this prospective study. Humphrey visual field (HVF) sensitivities were obtained from standard achromatic HVF test (24-2 SITA). RNFL was measured with scanning laser polarimetry (SLP, GDx-VCC) and optical coherence tomography (OCT, StratusOCT). Correlations were evaluated between RNFL and sensitivities from global, hemifields, and regional locations of the VF pertinent to the RNFL distribution. A total of 15 NAION eyes had inferior altitudinal HVF defects, and their global and regional RNFL was compared with that of control eyes. The main outcome measure was correlation between HVF sensitivities and RNFL. RESULTS: Correlations of global, hemifield, and sectorial HVF sensitivities with RNFL were greater when RNFL was measured with OCT than with SLP, except for nasal and inferonasal sectors. RNFL thickness was far lower in the hemiretinas corresponding to the relative unaffected hemifield in eyes with altitudinal VF defect compared with controls. CONCLUSIONS: In patients with NAION, RNFL measured by OCT provided better correlation to HVF changes than SLP did. Both instruments showed decreased RNFL in NAION eyes with altitudinal VF defects compared with control eyes, demonstrating loss of RNFL even in sectors of the optic disk that corresponded to relatively unaffected hemifield, suggesting greater damage beyond the extent estimated by VF methods.

Arteritis↗
PubMed1997

Asymmetries in the normal short-wavelength visual field: implications for short-wavelength automated perimetry.

PURPOSE: To quantify short-wavelength sensitivity in normal eyes by hemifield location, eccentricity, and age. METHODS: We measured achromatic and short-wavelength thresholds across visual fields covering a radius of 21 degrees of visual angle in 115 normal eyes in subjects aged 17 to 77 years and out to 30 degrees of eccentricity in an additional 57 eyes in subjects aged 22 to 80 years. RESULTS: Results indicated significantly greater sensitivity for the inferior visual field compared with the superior field (P = .001). The amount of asymmetry increased with eccentricity (P = .001) but not with age (P = .357). A temporonasal field asymmetry was noted at the most eccentric points of the 30-degree field (P = .001) but not at 21 degrees (P = .821). CONCLUSIONS: In addition to increasing our understanding of normal retinal function, these results have implications for basic research in comparison with results of studies using different retinal locations to assess short-wavelength sensitivity and for clinical practice, where short-wavelength sensitivity is used to diagnose and manage a number of diseases, including glaucoma, diabetic retinopathy, and acquired immunodeficiency syndrome (AIDS)-related vision loss.

Adolescent↗
PubMed1996

Visual field defects in esotropic cats: a developmental consequence of the squint.

In nine adult cats with surgically induced esotropia (squint-angle ranging between 8 degrees and 32 degrees), the extent of binocular and monocular visual fields was behaviourally assessed by the food-perimetry method. Results indicate that: (1) The extention of both the nasal and the temporal hemifield of the esotropic eye is narrowed. (2) Field losses are largest in the cats with severe esotropia (> 15 degrees); yet the relationship between rate of impairment scored in each animal and individual angles of squint is not linear. (3) In the cats with severe esotropia, the visual field of the non-deviated eye is also narrowed. (4) We suggest that field deficits reflect a stop in the developmental expansion of the immature visual field as a consequence of ocular misalignment.

Animals↗
PubMedDate not supplied

The retinal ganglion cell distribution and the representation of the visual field in area 17 of the owl monkey, Aotus trivirgatus.

The distribution of ganglion cells and displaced amacrine cells was determined in whole-mounted Aotus retinae. In contrast to diurnal simians, Aotus has only a rudimentary fovea. Ganglion cell density decreases towards the periphery at approximately the same rate along all meridians, but is 1.2-1.8 times higher in the nasal periphery when compared to temporal region at the same eccentricities. The total number of ganglion cells varied from 421,500 to 508,700. Ganglion cell density peaked at 15,000/mm2 at 0.25 mm dorsal to the fovea. The displaced amacrine cells have a shallow density gradient, their peak density in the central region is about 1500-2000/mm2 and their total number varied from 315,900 to 482,800. Comparison between ganglion cell density and areal cortical magnification factor for the primary visual cortex, area 17, shows that there is not a simple proportional representation of the ganglion cell distribution. There is an overrepresentation of the central 10 deg of the visual field in the visual cortex. The present results for Aotus and the results of a similar analysis of data from other primates indicate that the overrepresentation of the central visual field is a general feature of the visual system of primates.

Animals↗
PubMed2002

Information processing of pictograms and the visual field difference.

The main purpose was to investigate how we process pictograms and to examine the effects of learning on visual field differences when participants overlearn the meaning of each pictogram. 15 students were required to judge whether the referent of each symbol was either larger or smaller than the referent of the standard stimulus (Test 1). Several days later the same task was conducted (Test 2). Although a right visual field advantage was observed in Test 1, it was not apparent at Test 2 after participants had studied the pictogram list repeatedly. These results suggest that pictograms might be processed in much the same way as other ordinary verbal stimuli at a very early stage of learning. Participants could, however, comprehend the pictograms by employing a kind of imagery processing after they were familiar with the symbols.

Adolescent↗
PubMed2001

Compensatory visual field training for patients with hemianopia after stroke.

Twenty-one patients with hemianopia received 4 weeks of compensatory visual field training. Detection of and reaction time to visual stimuli were measured with eyes fixating (condition A) and with use of exploratory eye movements (condition B) before and after training. Twenty-three healthy individuals served as control subjects for measurements of parameters during both conditions. Patients with hemianopia to either side showed a marked improvement of detection and reaction time during condition B, but minimum or no change during condition A. Improvements were maintained 8 months after training. Activity of daily living skills also improved in all patients. The size of scotoma on computerized perimetry, in contrast, remained unchanged. Training improved detection of and reaction to visual stimuli without restitution of the visual field defect.

Activities of Daily Living↗
PubMed1993

[Glaucoma-like disc without increased intraocular pressure or visual field loss and early stage normal-tension glaucoma disc].

The optic disc topography of 11 eyes of 11 glaucoma-like discs without increased intraocular pressure or visual field loss was compared with that of 11 eyes of 11 relative early stage normal-tension glaucomas. There were no statistically significant differences between the two groups in terms of optic disc parameters measured with a Rodenstock Optic Nerve Head Analyzer Plus, except that the inferior quadrant of the neuroretinal rim area of the normal-tension glaucoma discs was significantly smaller than that of the glaucoma-like discs. Also, in the Humphrey automated visual field, only the superior part of the Total Deviation score of normal-tension glaucoma eyes corresponding to the inferior disc changes was significantly lower than that of glaucoma-like discs. When the data of the two groups were pooled, the inferior quadrant of the neuroretinal rim area significantly correlated with the visual field loss in the group of eyes with a rim area smaller than 0.198 mm2. These results seem to suggest that some of the glaucoma-like discs might be early normal-tension glaucoma.

Female↗
PubMed1982

Visual field defects in obstructive hydrocephalus.

Four cases are described in which visual field defects followed enlargement of the third ventricle. Three were due to aqueduct stenosis while in one case a left cerebellar hemisphere tumour was discovered. The visual field defects comprised a unilateral scotoma, bilateral scotomata and, in two patients, incongruous bitemporal hemianopia.

Adult↗
PubMedDate not supplied

Influence of nifedipine on the visual fields of patients with optic-nerve-head diseases.

Calcium-channel blockers have long been employed in coronary disease, and recent investigations have indicated their efficacy in improving the visual field in low-tension glaucoma or presumed vasospasm, possibly by enhancing ocular circulation. We evaluated the short-term influence of a typical calcium-channel blocker, nifedipine, on 59 patients with visual-field defects, some with optic-nerve-head pathology (n = 38) and some with normal-appearing optic nerve heads (n = 21). On the average, a statistically significant improvement of 1.2 dB was observed. Different types of patients, however, behaved quite differently. The younger the patient, the greater the improvement. Patients with normal optic nerve heads improved by 1.54 dB, whereas patients with optic-nerve-head excavation improved by only 0.66 dB. No response was observed in patients with anterior ischemic neuropathy. Marked deterioration was noted in one glaucoma patient with low systemic blood pressure. The visual-field changes were observed in the scotomatous and non-scotomatous areas. Thus, the calcium-channel blocker nifedipine can be effective in some selected diseases whose pathogenesis probably involves vascular dysregulation though it may even be contraindicated in others.

Glaucoma↗
PubMed2002

Visual field defects in non-functioning pituitary adenomas.

PURPOSE: To report the prevalence and pattern of visual field loss in non-functioning pituitary adenomas and to study the relationship between the tumour size and severity of field defects. METHODS: Ninety-three patients with histologically confirmed pituitary adenomas, non-functional on hormonal assessment, underwent a complete ophthalmic assessment and automated perimetry using the HFA 30-2 programme. Defects with quadrantanopic or hemianopic characteristics, defined using criteria on the threshold/pattern deviation plots were considered typical. Typical defects were graded as mild, moderate and severe. All other defects were considered atypical. A neuroradiologist measured tumour size on a CT or MRI Scan. The Chi-square test for trend was used to test association of tumour volume with severity of typical defects. RESULTS: Eighty-eight (94.6%) of the 93 patients had a field defect. Typical field defects were seen in 69 (74.2%) patients and atypical in 19 (20.4%). A severe typical defect involving at least 3 quadrants in one or both eyes was the most common (24 patients or 25.80%). All 31 patients (33.3%) with a tumour size greater than 20 cc had field defects. Severity of field defect increased with tumour volume (Chi-square test for trends significant p = 0.0096). CONCLUSIONS: Field defects occurred in 95% of patients with non-functioning pituitary macroadenoma. A severe visual field loss involving at least 3 quadrants in one or both eyes was the most common. 20% of patients had atypical field defects. Severity of field defects increased with tumour volume.

Adenoma↗
PubMed1987

[Study of early glaucomatous visual field defects with the automatic perimeter Topcon SBP-1000. Comparative study with the Octopus 201 perimeter].

The automatic perimeter TOPCON SBP-1000 uses light emitting diodes (LED's) for stimulus generation and thus completely differs from the projection type perimeter OCTOPUS 201. In order to get some first idea about the capabilities of the TOPCON SBP-1000 22 eyes of 18 patients with early glaucomatous visual field defects were examined both with the glaucoma program/TOPCON SBP-1000 and program 31/OCTOPUS 201. Field defects were divided into three groups according to the total loss (program DELTA/OCTOPUS 201): group I with a total loss of 0 dB, group II with a total loss of 1-200 dB, group III with a total loss greater than 200 dB. Evaluation and comparison of visual field results is done after discussing the most important technical parameters and fundamental aspects of methods and strategies using the total percentage of "normal" test points, "small relative defects", "deep relative defects" and "absolute defects". We could show that specificity and sensitivity for the detection of earliest field defects are quite equal both in the TOPCON SBP-1000 and in the OCTOPUS 201. Concerning the detection of more pronounced visual field defects the TOPCON-perimeter has a somewhat smaller sensitivity as a result of the different definition of the category "normal"; at the same time there is a tendency for showing up more "absolute defects" instead of "deep relative defects". Technical parameters and strategies are discussed critically taking into consideration the practical experience obtained during this first routine testing.

Adult↗
PubMed1990

The effects of fixation and restricted visual field on vection-induced motion sickness.

Approximately 60% of healthy human subjects experience motion sickness when exposed to a rotating optokinetic drum. The purpose of the present study was to determine the effects of certain visual factors on susceptibility to motion sickness. Vection data (illusory self-motion), horizontal eye movement recordings, subjective motion sickness report, and a measure of gastric myoelectric activity (electrogastrogram, EGG) were obtained from 45 subjects, who were randomly divided into the following three groups: a control group that observed the entire visual field with no fixation, a group that fixated on a central target, and a third group that had a visual field restricted to 15 degrees. The experimental session was divided into the following three 12-min periods: baseline, drum rotation, and recovery. The results showed that fixation greatly reduced nystagmus and slightly reduced vection. The restricted visual field slightly reduced nystagmus and greatly reduced vection. Both of these manipulations significantly reduced symptoms of motion sickness and tachyarrhythmia, the abnormal gastric myoelectric activity that usually accompanies nausea.

Electromyography↗
PubMed2002

[Visual field disturbances in epileptic patients treated with vigabatrin (sevril)].

Vigabatrin, one of the newer anti-epileptic drugs (AED), whose effect is mediated via elevated levels of brain GABA, has proved to be effective in drug resistant partial seizures and infantile spasms. Recently, visual field constriction was found in up to 30% of adults, whereas information for the pediatric age group is sparse. We examined 24 visually-asymptomatic children, ages 3.5-18 years, treated for 3.01.6 years at doses of 25-90 mg/kg. These children underwent an ophthalmologic examination, visual evoked potentials, electroretinogram and when possible, perimetry. Over half of the children had at least one abnormal test and 11/17, who were able to undergo perimetric studies, had symmetrical, nasal visual field constriction. In view of the gravity and prevalence of visual field constriction, use of the AED vigabatrin should be weighed against its clinical benefits.

Anticonvulsants↗
PubMed1976

Near-field visual acuity of pigeons: effects of head location and stimulus luminance.

Two pigeons were trained to discriminate a grating stimulus from a blank stimulus of equivalent luminance in a three-key chamber. The stimuli and blanks were presented behind a transparent center key. The procedure was a conditional discrimination in which pecks on the left key were reinforced if the blank had been present behind the center key and pecks on the right key were reinforced if the grating had been present behind the center key. The spatial frequency of the stimuli was varied in each session from four to 29.5 lines per millimeter in accordance with a variation of the method of constant stimuli. The number of lines per millimeter that the subjects could discriminate at threshold was determined from psychometric functions. Data were collected at five values of stimulus luminance ranging from--0.07 to 3.29 log cd/m2. The distance from the stimulus to the anterior nodal point of the eye, which was determined from measurements taken from high-speed motion-picture photographs of three additional pigeons and published intraocular measurements, was 62.0 mm. This distance and the grating detection thresholds were used to calculate the visual acuity of the birds at each level of luminance. Acuity improved with increasing luminance to a peak value of 0.52, which corresponds to a visual angle of 1.92 min, at a luminance of 2.33 log cd/m2. Further increase in luminance produced a small decline in acuity.

Accommodation, Ocular↗