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At least 19 recordsLinked to original sources
PubMed1992

Central visual field, visual acuity, and sudden visual loss after glaucoma surgery.

The relationship between Snellen visual acuity and central visual field loss as determined by the Humphrey 10-degree test was examined in 96 glaucomatous eyes of 79 patients. The severity of the field defect was determined by the number of affected quadrants, defined as a sensitivity loss of at least 10 decibels from normal at the most central point of 1.4-degree eccentricity. The decrease in median acuity was gradual, one-half line per quadrant for one and two affected quadrants, and an additional one and one-half line to two lines for three and four quadrants. Loss of acuity was disproportionate when both temporal quadrants were affected. The major source of error was difficulty with fixation. One type, a prolonged fixation shift, was not related to short-term fixation losses. There was a significant correlation between acuity and foveal threshold over a wide range of both variables. Sudden visual loss from additional optic nerve damage was studied retrospectively in 96 eyes with advanced glaucoma and a central field defect. A frequency of 3% for any loss of visual acuity and a frequency of 1% for a loss to 20/200 or worse were noted. There were no apparent predictive factors.

Adult↗
PubMed1992

Simulation of a phosphene-based visual field: visual acuity in a pixelized vision system.

A visual prosthesis for the blind using electrical stimulation of the visual cortex will require the development of an array of electrodes. Passage of current through these electrodes is expected to create a visual image made up of a matrix of discrete phosphenes. The quality of the visual sense thus provided will be a function of many parameters, particularly the number of electrodes and their spacing. We are conducting a series of psychophysical experiments with a portable "phosphene" simulator to obtain estimates of suitable values for electrode number and spacing. The simulator consists of a small video camera and monitor worn by a normally sighted human subject. To simulate a discrete phosphene field, the monitor is masked by an opaque perforated film. The visual angle subtended by images from the masked monitor is 1.7 degrees or less, depending on the mask, and falls within the fovea of the subject. In the study presented here, we measured visual acuity as a function of the number of pixels and their spacing in the mask. Visual acuity was inversely proportional to pixel density, and trained subjects could achieve about 20/26 visual acuity with a 1024 pixel image. We conclude that 625 electrodes implanted in a 1 cm by 1 cm area near the foveal representation of the visual cortex should produce a phosphene image with a visual acuity of approximately 20/30. Such an acuity could provide useful restoration of functional vision for the profoundly blind.

Blindness↗
PubMed1987

Are there different methods of lexical access for words presented in the left and right visual fields?

Visual field differences can arise from hemispheric specializations or perceptual asymmetries. Deciding which of the two is responsible for a particular visual field difference is a recurrent problem for researchers concerned with lateral asymmetries. In the present paper, the difficulties involved in interpreting visual field asymmetries are discussed as they apply to the Young and Ellis (1985) research on the interactive effects of word length and visual hemifield on the recognition of English words. We show that one of their critical results disappears when small changes are made to their experimental procedure. Our data demonstrate that the visual field differences Young and Ellis reported were the result of preceptual asymmetries rather than different methods of lexical access in the two cerebral hemispheres.

Adolescent↗
PubMed1995

Aging effects for opponent mechanisms in the central visual field.

Visual field sensitivity measures were obtained for normal observers between the ages of 20 and 83 years, using test conditions in which detection has been shown to be mediated by opponent (chromatic) mechanisms (Size V target, 620 nm stimulus, 31.5 asb [10 cd/m2] white background). Average visual field sensitivity for opponent mechanisms decreased by approximately 0.6 dB per decade. This age-related sensitivity loss was smallest for the central 10 degrees visual field (0.5 dB per decade) and increased as a function of stimulus eccentricity (0.66 dB per decade for 20 to 30 degrees eccentricity), although the differences in aging effects for various eccentricities were not statistically significant. There were negligible differences in age-related sensitivity losses for opponent mechanisms in various quadrants of the visual field. These findings are generally similar to those obtained for standard automated perimetry, which uses a small white target on a white background. By comparison, short wave-length-sensitive mechanisms exhibit age-related losses that are more than twice as large, even after lenticular transmission losses are taken into account. These data provide a basis for distinguishing early disease-related losses from those related to normal aging.

Adult↗
PubMedDate not supplied

Mapping of VEPs and ERG responses to punctual stimulations in the visual field.

Visual field projection maps were obtained using retinal and cortical EP amplitude values. Single meridian investigations were also performed. Stimulation was done with punctual photic stimuli delivered by the LED perimeter built for the purpose. Schedule with 28 stimulation loci was adopted. The B wave of the average ERG and P100 component of the cortical VEP were measured. The maps were obtained by interpolation of amplitude values on a grid of 21 x 21 characters. By comparing the retinal and cortical visual field maps, conclusions regarding the normality of visual structures (peripheral or central) can be drawn. Our procedure adds to the previous data on visual field investigation (cynetic or static) important elements concerning vision electrophysiology.

Brain Mapping↗
PubMed2001

Perceived length in the central visual field: evidence for visual field asymmetries.

Visual performance for judging the length of a simultaneously presented pair of radial lines, reciprocally opposed by 180 degrees at a central fixation point, was assessed for 24 radial positions of test lines, for three viewing conditions (binocular, left and right monocular) and five different standard line sizes (1.43-7.13 degrees ). Generally, the results showed underestimation of the test line. Furthermore, clear visual field asymmetries were observed between the upper versus lower visual fields and the left versus right visual fields with greater underestimation for test lines presented in the lower and right visual fields. Also, asymmetries tended to be strongest along the 30 and 150 degrees radial orientations. Fourier analysis indicated that these asymmetries are mainly described by summing up the f0, f1, f2 and f5 components.

Adolescent↗
PubMed2005

[Changes of visual field and visual evoked potential in nasopharyngeal carcinoma patients after radiotherapy].

BACKGROUND & OBJECTIVE: Radiotherapy is the main treatment for nasopharyngeal carcinoma (NPC). The incidence of radiation-induced complications, especially radiation optic neuropathy (RON), increases along with prolonging survival time of the patients. This study was to investigate RON in NPC patients after irradiation by visual field and visual evoked potential (VEP) tests. METHODS: A total of 28 NPC patients, who underwent conventional external-beam irradiation, received visual field and VEP tests before irradiation, at the end of irradiation, and 5 years after irradiation. RESULTS: Thirty-four (60.7%) eyes in 21 patients developed pathological visual field; 15 (44.1%) of these 34 eyes occurred within 10-24 months after irradiation. Of the 34 eyes, 8 showed concentric visual field constriction; 6 showed bitemporal hemianopia; 8 showed local photosensitivity descend; 10 showed central or cecocentral scotoma; 2 showed scotoma enlargement. Forty-four (78.6%) eyes in 26 patients appeared VEP abnormity; 24 (54.5%) of these 44 eyes occurred within 14 months after irradiation. In small, medium, and large elements, VEP latencies were significantly longer within 1 year after irradiation than pre-irradiation (P < 0.001, P < 0.001, and P=0.001); VEP amplitudes were lower within 1 year after irradiation than pre-irradiation without significant difference (P=0.249, P=0.940, and P=0.450). One year after treatment, VEP latency delay maintained in each element (P=0.004, P < 0.001, P < 0.001); VEP amplitudes were decreased (P=0.002, P=0.189, P < 0.001). The incidence of pathologic visual field was significantly lower in patients received irradiation of < or =70 Gy than in patients received irradiation of > 70 Gy (50.0% vs. 77.3%, P=0.041). CONCLUSIONS: RON correlates to total irradiation dose. Pathologic visual field may indicate the position of RON.

Adult↗
PubMed2006

[How to assess the stability of glaucoma? Visual field].

Visual field results are subject to fluctuations in glaucoma and it is important to evaluate them to differentiate fluctuation and progression. Three visual fields are thus required for the determination of progression because of these short or long term fluctuations. During each measurement, some points are tested twice in order to assess short term fluctuation. Other fluctuations are simply due to technical difficulties like a change of position of the head from one examination to the next one. Learning effect is in fact the more important factor which may improve results. However some real long term fluctuations exist, mainly as a function of the general health of the patient. Progression of the visual field is usually assessed by subjective analysis of the fields with an evaluation of the intensity and the size of scotomas and a comparison of global indices. A more objective analysis can be obtain by the use of specific programs like the "Glaucoma Progression Analysis" with the Humphrey Perimeter or the "Progressor" with the Octopus Perimeter.

Disease Progression↗
PubMed1994

The topography of visual evoked response properties across the visual field.

Visual evoked potentials (VEPs) to luminance and pattern reversal stimulation were derived for a large number of small areas throughout the central visual field. In one study, the field was tested with a stimulus array consisting of 64 equal-area patches. Local response components were extracted by independent m-sequence modulation of the patches. Field topographies were compared between and within subjects using different electrode placements. The subject-dependent local variability observed in response characteristics is attributed to contributions from two or more cortical representations of the visual field and to inter-subject variations in gross cortical anatomy. The second study used luminance modulation of 56 patches across a 15 degrees field, scaled to activate approximately equal cortical areas in area V1. This produced many robust signals at all eccentricities. Bipolar and double differential ("1-dimensional Laplacian") signals were compared. The double differencing reduced contributions from distant or distributed sources, enhancing nearby current source activity, and greatly improved S/N for many stimulus locations. The high-resolution visual field maps demonstrated that clinical field testing using the VEP is not feasible because of effects of cortical convolutions on responses. However, the vast improvement in data quality and quantity make it a useful tool for VEP source localization and identification.

Brain↗
PubMed1989

Visual field versus visual evoked potentials in maculopathies and optic neuropathies.

Both kinetic and static visual fields and visual evoked potential (VEP) were tested in 52 patients with maculopathies and in 29 patients with axial optic neuropathies. The results of central static quantitative perimetry and pattern reversal VEP were compared. The amplitude and latency of P100 were correlated with the total loss of central visual threshold in maculopathies. While the P100 latency was not correlated with the total loss of the central visual threshold in neuropathies, their latency delay was more obvious than that in maculopathies. We arrived at the conclusion that both VEP and visual field are necessary for assessing function loss and reflecting different pathological mechanisms in macular and optic nerve diseases.

Adolescent↗
PubMed2002

The Advanced Glaucoma Intervention Study (AGIS): 12. Baseline risk factors for sustained loss of visual field and visual acuity in patients with advanced glaucoma.

PURPOSE: To examine the relationships between baseline risk factors and sustained decrease of visual field (SDVF) and sustained decrease of visual acuity (SDVA). DESIGN: Cohort study of participants in the Advanced Glaucoma Intervention Study (AGIS). METHODS: This multicenter study enrolled patients between 1988 and 1992 and followed them until 2001; 789 eyes of 591 patients with advanced glaucoma were randomly assigned to one of two surgical sequences, argon laser trabeculoplasty (ALT)-trabeculectomy-trabeculectomy (ATT) or trabeculectomy-ALT-trabeculectomy (TAT). This report is based on data from 747 eyes. Eyes were offered the next intervention in the sequence upon failure of the previous intervention. Failure was based on recurrent intraocular pressure elevation, visual field defect, and disk rim criteria. Study visits occurred every 6 months; potential follow-up ranged from 8 to 13 years. For each intervention sequence, Cox multiple regression analyses were used to examine the baseline characteristics for association with two vision outcomes: SDVF and SDVA. The magnitude of the association is measured by the hazard ratio (HR), where HR for binary variables is the relative change in the hazard (or risk) of the outcome in eyes with the factor divided by the hazard in eyes without the factor, and HR for continuous variables is the relative change in the hazard (or risk) of the outcome in eyes with a unit increase in the factor. RESULTS: Characteristics associated with increased SDVF risk in the ATT sequence are: less baseline visual field defect (hazard ratio [HR] = 0.86, P <.001, 95% CI = 0.82-0.90), male gender (HR = 2.23, P <.001, 1.54-3.23), and worse baseline visual acuity (HR = 0.96, P =.001, 0.94-0.98); in the TAT sequence: less baseline visual field defect (HR = 0.93, P =.001, 0.89-0.97) and diabetes (HR = 1.87, P =.007, 1.18-2.97). Characteristics associated with increased SDVA risk in both treatment sequences are better baseline acuity (ATT: HR = 1.05, P <.001, 1.02-1.09; TAT: HR = 1.06, P <.001, 1.03-1.08), older age (ATT: HR = 1.05, P =.001, 1.02-1.08; TAT: HR = 1.04, P =.002, 1.01-1.06), and less formal education (ATT: HR = 1.92, P =.001, 1.29-2.88; TAT: HR = 1.77, P =.002, 1.22-2.54). CONCLUSIONS: For SDVF, risk factors were better baseline visual field in both treatment sequences, male gender, and worse baseline visual acuity in the ATT sequence, and diabetes in the TAT sequence. For SDVA, risk factors in both treatment sequences were better baseline visual acuity, older age, and less formal education.

Aged↗
PubMed1980

Correlations between intraocular pressure, visual field and visual acuity, based on 11 years of observations of treated chronic glaucomas.

In a retrospective study of 114 patients under treatment for chronic glaucoma (81 without and 33 with visual field defect) over an 11-year period of observation, a highly significant correlation between intraocular pressure and progression of visual field defects could be demonstrated. This correlation could be shown for the visual field outer boundary in 81 eyes with ocular hypertension and for typical visual field defects in 33 eyes with chronic glaucoma. The relationship was, however, only significant when both the standard deviation of the annual intraocular pressure and the influence of cataract development upon visual acuity were considered. Quantitative analysis of the results of Goldmann perimetry was by planimetry and took into account only changes during the 11-year observation period.

Aged↗
PubMed1989

[Long-term follow-up of deterioration of the visual field in visual acuity in retinitis pigmentosa].

The first part of this presentation is devoted to the problem of determining the precise time of onset of retinitis pigmentosa (RP). For the purpose of this discussion we will stay with the definition of the beginning of RP as that date on which the decrease in dark adaptation is first noticed, rather than visual field loss, which is subject to even greater uncertainty. The cases selected demonstrate that the period between the first sign of night-blindness and a noticeable narrowing of the visual field can vary greatly. A latent period of slow progress is followed by marked decrease in visual function. In a third period the area loss proceeds linearly. The course of the disease was observed over periods of up to 16 years using the Goldmann perimeter. Several stages of visual field deterioration are presented over periods of up to 65 years. The mode of visual field loss depends on the diameter of the test objects employed.

Adult↗
PubMed2000

The advanced glaucoma intervention study, 6: effect of cataract on visual field and visual acuity. The AGIS Investigators.

OBJECTIVE: To investigate the effect of cataract on visual function and the role of cataract in explaining a race-treatment interaction in outcomes of glaucoma surgery. METHODS: The Advanced Glaucoma Intervention Study (AGIS) enrolled 332 black patients (451 eyes) and 249 white patients (325 eyes) with advanced glaucoma. Eyes were randomly assigned to an argon laser trabeculoplasty (ALT)-trabeculectomy-trabeculectomy sequence or a trabeculectomy-ALT-trabeculectomy sequence. From the AGIS experience with cataract surgery during follow-up, we estimated the expected change in visual function scores from before cataract surgery to after cataract surgery. Then, for eyes with cataract not removed, we used these estimates of expected change to adjust visual function scores for the presumed effects of cataract. In turn, we used the adjusted scores to obtain cataract-adjusted main outcome measures. MAIN OUTCOME MEASURES: Average percent of eyes with decrease of visual field (APDVF) and average percent of eyes with decrease of visual acuity (APDVA). RESULTS: Within the 2 months before cataract surgery, visual acuity was better in eyes of white patients than of black patients by an average of approximately 2 lines on the visual acuity test chart. Cataract surgery improved visual acuity and visual field defect scores, with the amounts of improvement greater when preoperative visual acuity was lower. Adjustments for cataract brought about the following relative reductions: for APDVF, a relative reduction of 5% to 11% in black patients and 9% to 11% in white patients; for APDVA, a relative reduction of 45% to 49% in black patients and 31% to 38% in white patients; and for the APDVF and APDVA race-treatment interactions, relative reductions of 25% and 45%, respectively. CONCLUSIONS: On average, visual function scores improved after cataract surgery. The findings of reduced race-treatment interactions after adjustment for cataract do not alter our earlier conclusion that the AGIS 7-year results support use of the ALT-trabeculectomy-trabeculectomy sequence for black patients and of the trabeculectomy-ALT-trabeculectomy sequence for white patients without life-threatening health problems. The choice of treatment should take into account individual patient characteristics and needs.

Adult↗
PubMed1994

[A.R.G.U.S. A model for an interactive visual field and visual pathway atlas].

A.R.G.U.S. is a data base that connects visual field defects directly with possible lesion sites that are presented graphically. By means of a touch screen or "mouse," scotomata can be depicted on a VDU, while on a second monitor the computer program simultaneously shows the resulting defects in the visual pathway. It is possible to page through different sections of the visual pathway; the lesion is probably located in the section where the affected fibers lie the closest to each other and where the non-affected fibers are the farthest apart. Additionally, the VDU depicting the visual pathway can show the surrounding anatomic structures in the form of brain sections. Even in these sections, lesions can be superimposed interactively; the resulting scotomata are simultaneously depicted on the "visual field VDU." Anatomic and functional details can be displayed by touching the structure of interest. If necessary, a video clip can be activated in the same way. New anatomic findings can be considered by modifying the course of the fibers of the visual pathway. This new technique is especially helpful in distributing comprehensive neuro-ophthalmological knowledge.

Artificial Intelligence↗
PubMed2000

Predicting binocular visual field sensitivity from monocular visual field results.

PURPOSE: To compare methods of predicting binocular visual field sensitivity of patients with glaucoma from monocular visual field data. METHODS: Monocular and binocular visual fields were obtained for 111 patients with varying degrees of glaucomatous damage in one or both eyes, using the Humphrey 30-2 full-threshold procedure. Four binocular sensitivity prediction models were evaluated: BEST EYE, predictions based on individual values for the most sensitive eye, defined by mean deviation (MD); AVERAGE EYE, predictions based on the average sensitivity between eyes at each visual field location; BEST LOCATION, predictions based on the highest sensitivity between eyes at each visual field location; and BINOCUIAR SUMMATION, predictions based on binocular summation of sensitivity between eyes at each location. Differences between actual and predicted binocular sensitivities were calculated for each model. RESULTS: The average difference between predicted and actual binocular sensitivities was close to zero for the BINOCULAR SUMMATION and BEST LOCATION models, with 95% of all predictions being within +/-3 dB of actual binocular sensitivities. The best eye (MD) prediction had an average error of 1.5 dB (95% confidence limits [CL], +/-3.7 dB). The average eye prediction was the poorest, with an average error of 3.7 dB (95% CL, +/-4.6 dB). CONCLUSIONS: The BINOCULAR SUMMATION and BEST LOCATION models provided better predictions of binocular visual field sensitivity than the other two models, with a statistically significant difference in performance. The small difference in performance between the BINOCULAR SUMMATION and BEST LOCATION models was not statistically significant. For evaluations of functional visual field influences on task performance, daily activities, and related quality-of-life issues, either the BINOCULAR SUMMATION or BEST LOCATION model provides good estimates of binocular visual field sensitivity.

Glaucoma↗
PubMed1985

Functional visual field of patients with visual field loss.

To assess the capability of perceiving forms in patients with visual field loss, a concept of functional visual field was introduced based on determinations of the time required for pattern recognition. Two series of stimulus patterns were made of Japanese syllabic hiragana characters drawn with black dots in the background of open circles of various sizes: the clear stimulus had only open circles in the background and the noisy stimulus had black dots scattered in the background. The stimuli were presented for various durations to 15 normal subjects and 25 patients with narrowed visual field; a correlation of the percentages of correct pattern recognition with the stimulus durations permitted calculations of the 50% recognition time. The recognition time was longer with the noisy than with the clear stimuli. The recognition time with a given stimulus size was longer in patients than in normal subjects. In 3 normal subjects the visual field was artificially narrowed and the recognition time was determined. The recognition time could be expressed by a power function of the ratio of the effective visual field diameter to the diameter of the stimulus pattern. On this basis the functional visual field size of a patient was defined as the size of the artificially narrowed visual field of the normal subject that required the same recognition time as that of the patient. The functional visual field of patients could be correlated with the area of the perimetric field with the V/4 target of Goldmann's projection perimeter. The concept of the functional visual field was found to be useful to express the patients' capability for pattern perception.

Adult↗