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At least 541 records · Page 30Linked to original sources

PubMed1993

The visual field indices in primary open-angle glaucoma.

PURPOSE: The distribution of sensitivity across the visual field, as determined by automated threshold static perimetry, can be summarized in terms of visual field indices. Such indices can be weighted for the variation in threshold at each eccentricity. The aims of this study were to determine the influence of the weighting factor, the relationship between the unweighted indices derived from Programs 30-2 and 24-2, and the relationship between the number of double determinations of threshold and the magnitude of the short-term fluctuation. METHODS: One visual field derived by Program 30-2 of the Humphrey Field Analyzer was selected from each of 60 consecutive patients with primary open-angle glaucoma. The first two fields from each individual patient were avoided. Unweighted visual field indices were calculated and compared with the Program 30-2 weighted indices using an assessment of agreement evaluated with respect to the 95% confidence limits of the population. RESULTS: The weighting function had no influence on the mean deviation, but it caused a slight reduction in the short-term fluctuation and an elevation in the pattern and corrected pattern standard deviations. There was little difference between the indices generated by Programs 30-2 and 24-2. The short-term fluctuation increased with an increase in the number of double determinations of threshold. CONCLUSIONS: The weighting function had little clinical influence on the visual field indices. The indices derived from Programs 30-2 and 24-2 were similar, and the short-term fluctuation would better reflect the intratest variability if all available double determinations of threshold were used to calculate the index.

Aged↗

PubMed1984

Visual field defects in ocular hypertension and glaucoma.

We measured visual fields using three unconventional test stimuli; sine-wave grating targets of 2 and 5 cycles/degree and a visual acuity target. Of 15 patients with ocular hypertension (OHT), eight had visual field defects for contrast sensitivity when tested with a sine-wave grating target of low spatial frequency; these patients had normal perimetric fields and normal fields for visual acuity. We hypothesize that the outer extremities of the largest dendritic trees of retinal ganglion cells become functionally ineffective in some patients with OHT and early glaucoma, possibly due to retinal ischemia, and as a result visual sensitivity to low spatial frequency gratings is reduced while visual acuity is spared. Since this hypothetical mechanism may be somewhat independent of the mechanism that causes ganglion cell loss, not all the contrast field defects in OHT would be expected to progress to glaucomatous field defects and be evident to clinical perimetry.

Aged↗

PubMed1999

[Concentric changes in the visual field associated with GABA-mimetic antiepileptic agents].

Bilateral visual field constriction has been recently reported in patients treated with vigabatrin. It has been considered that vigabatrin, a GABA agonist antiepileptic drug, was specifically responsible for this visual field defect. We present four observations sharing the same characteristics of chronic tunnel vision. Three patients had had vigabatrin but the fourth one received other antiepileptic drugs, progabide, an agonist of post-synaptic GABA receptors, and phenobarbital which interferes with GABA-A receptors. It is thus possible to hypothesize a retinal toxicity triggered by chronically increased GABA transmission. If this is confirmed, an accurate incidence of symptomatic and asymptomatic visual field constriction with GABA-mimetic drugs should be established, as well as the patients' profiles which are more at risk. Patients currently under this type of treatment should be checked by both manual and automatic perimetry every six months to one year.

Adult↗

PubMed1998

Variability in glaucomatous visual fields: implications for shared care schemes.

The purpose of this study was to establish the extent of variability in the visual fields of patients with glaucoma using a suprathreshold perimetric test strategy. The visual fields of 104 patients (126 eyes) were measured twice, on separate days, with a Henson CFA3000 central visual field analyser. All eyes had a diagnosis of glaucoma and had a minimum of three stimuli missed at 12 dB above their threshold estimate derived at the beginning of the first suprathreshold examination. The perimeter tested 132 locations within the central 25 degrees with a multiple stimulus suprathreshold strategy. Data were analysed on the basis of the difference in the number of recorded missed stimuli between the two visits. Large amounts of variability were found in the visual field results. Variability was largest when all levels of defect were included (> = 5 dB) and was found to be independent of the overall extent of loss. Results from the superior hemifield were found to be more variable than those from the inferior hemifield. The results highlight the problem of differentiating real change in visual field status from the enhanced variability seen in patients with glaucomatous visual field loss. The results from this study can be used to establish return-referral criteria for shared care schemes. The advantages of duplicate measures of the visual field are highlighted.

Glaucoma↗

PubMed2001

Visual field defects with vigabatrin: epidemiology and therapeutic implications.

Vigabatrin is an antiepileptic drug (AED) that acts as a selective irreversible inhibitor of gamma-aminobutyric acid (GABA) transaminase. In 1997, 3 cases of severe symptomatic and persistent visual field constriction associated with vigabatrin treatment were described. During 1997 to 1998, similar concentric visual field constrictions were described in patients with drug-resistant epilepsy who were receiving vigabatrin concurrently with other AEDs. However, a study of patients treated with vigabatrin monotherapy alone showed that there was a causal relationship between vigabatrin treatment and the specific bilateral concentric visual field constriction. The Marketing Authorisation Holders survey (involving 335 vigabatrin recipients aged >14 years) indicated that 31% of patients [95% confidence interval (CI) 26 to 36%] had a visual field defect attributable to vigabatrin, compared with a 0% incidence of visual field defects (upper 95% CI 3%) in an unexposed control group. Other studies in adults have given similar overall prevalences, with a total of 169 of 528 patients diagnosed with vigabatrin-associated field defects (32%, 95% CI 28 to 36%). Male gender seems to be associated with an increase in the relative risk of visual field loss of approximately 2-fold. The pattern of defect is typically a bilateral, absolute concentric constriction of the visual field, the severity of which varies from mild to severe. Data gathered so far suggest that the cumulative incidence increases rapidly during the first 2 years of treatment and within the first 2 kg of vigabatrin intake, stabilising at 3 years and after a total vigabatrin dose of 3 kg. The prevalence of vigabatrin-associated field defects seems to be lower in children, but there are also methodological problems and greater variability in the assessment of visual fields in children. There is particular concern that the increased risk of the visual field defects will outweigh the benefit of the drug in patients who could be controlled with other AEDs. Vigabatrin should currently be used only in combination with other AEDs for patients with resistant partial epilepsy when all other appropriate drug combinations have proved inadequate or have not been tolerated. Regular visual field testing should be performed before the start of treatment and at regular intervals during treatment. Patients with pre-existent visual field defects due to other causes should not be treated with vigabatrin. Currently, the benefits of treating infantile spasms with vigabatrin monotherapy seem to outweigh the risks, but further prospective studies and follow-up of children receiving treatment are needed to evaluate the place of vigabatrin in this indication.

Animals↗

PubMed1984

Microcomputer-based testing of proficiency with the visual field examination.

A system for computer-assisted instruction in performing ophthalmic visual field examinations is presented. The system is implemented on a microcomputer making use of specially developed algorithms to summarize the information contained in a visual field in a very compact, efficient manner and to determine cursor position relative to stored visual field landmarks. The computer program presents a challenging testing situation by using visual fields, based on those of actual patients, of differing degrees of complexity. It is particularly well suited for trainees as well as for the physicians and ophthalmic technicians who frequently perform this examination.

Computer-Assisted Instruction↗

PubMed1997

Isoluminance and chromatic motion perception throughout the visual field.

Isoluminance and chromatic motion perception for red/green gratings were measured throughout an 80 deg visual field. Generally, the red/green isoluminance values changed with increasing eccentricity, i.e., observers increased the red luminance contrast for a fixed green luminance contrast. Enlarging the target size (to compensate for the cone density changes with eccentricity) and decreasing the spatial frequency (to compensate for receptive field property changes with eccentricity) did not change the isoluminance values within the central 20 deg, but the isoluminance ratios decreased beyond 20 deg. Our manipulations did not entirely compensate for a given eccentricity, which implies the need for a post-receptoral scaling function for the perception of drifting chromatic stimuli. Further, the results for isoluminance show heterogeneity between the visual field meridians where the red to green luminance ratio tends to be greater in the superior visual field. In our present conditions, chromatic motion was always perceived (up to 40 deg of eccentricity), but sensitivity generally decreased with increasing eccentricity. The inferior visual field was found to be the most sensitive to chromatic motion. We propose that the lower visual field and not the superior visual field is specialized for colour motion information.

Color Perception↗

PubMed1999

Visual field defects associated with vigabatrin therapy.

OBJECTIVE: To estimate the prevalence of visual field defects in patients taking the anticonvulsant drug vigabatrin and to characterise the features of visual dysfunction found. METHODS: Thirty three unselected patients attending neurology and epilepsy clinics were identified as taking vigabatrin and asked to attend for neuro-ophthalmic evaluation. A control group of 16 patients with epilepsy unexposed to vigabatrin was also evaluated. Visual fields were examined by static perimetry using a Humphrey field analyser. Patients underwent detailed ophthalmic examination, various blood tests, and brain MRI where necessary. Visual evoked responses (VERs), electro-oculograms (EOGs), and electroretinograms (ERGs) were recorded. RESULTS: Of 31 assessable patients treated with vigabatrin, 16 (52%) had definitely abnormal visual fields, nine (29%) had fields that were inconclusive, four (13%) had normal fields, and two (6%) proved unable to cooperate with testing. In four patients some plausible cause was found for the field abnormality leaving 12 patients (39%) in whom a definite bilateral field defect was found, possibly caused by vigabatrin treatment. Of 16 control patients none had definitely abnormal fields, 12 (75%) had normal fields, and four (25%) had fields that were inconclusive. The field defects associated with vigabatrin treatment showed a characteristic pattern of concentric peripheral field loss with temporal and macular sparing. The VERs and ERGs were normal. The EOG Arden Index was reduced in patients taking vigabatrin, although this returned towards normal when vigabatrin was stopped, even in the presence of persistent field defects. Multifocal ERGs recorded in two patients were abnormal, showing marked reduction in amplitude of the peripheral focal ERG. CONCLUSIONS: Treatment with vigabatrin was associated with a high prevalence of peripheral visual field defects. This seemed to be the result of a toxic effect of vigabatrin on the retina and seemed to persist if the drug was withdrawn.

Adolescent↗

PubMed2006

Relative risk of progressive glaucomatous visual field loss in patients enrolled and not enrolled in a prospective longitudinal study.

OBJECTIVE: To establish the relative risk of progressive visual field loss in a sample of glaucomatous eyes enrolled in a prospective longitudinal study vs a matched sample of eyes not enrolled in a study. METHODS: The first visual field records of 66 glaucomatous eyes enrolled in a prospective longitudinal study (mean follow-up time, 3.4 years; mean number of visual field tests, 8.3) were matched to 66 eyes from patients not enrolled in a study (mean follow-up time, 3 years; mean number of visual field tests, 3.7). Eyes were matched on the basis of (1) time of enrollment, (2) length of follow-up, and (3) the extent and spatial pattern of visual field loss. Linear regression of global visual field indexes was used to measure change and the relative risk of progression was calculated for a series of progression criteria sample. RESULTS: The relative risk of progressive visual field loss was on average 368% (range, 209%-673%) higher in the eyes not enrolled in a prospective longitudinal study. CONCLUSION: Selection bias may reduce the risk of progressive visual field loss in patients enrolled in longitudinal studies.

Disease Progression↗

PubMed2004

Visual field changes after laser in situ keratomileusis in myopic eyes.

PURPOSE: To evaluate the effect of acute elevation of intraocular pressure (IOP) during laser in situ keratomileusis (LASIK) on the visual field in myopic eyes. SETTING: Istanbul University, Cerrahpassa Medical Faculty, Istanbul, Turkey. METHODS: Thirty-seven eyes of 37 patients were included in the study. The LASIK procedure was performed using the Hansatome microkeratome (Bausch & Lomb) and the Summit SVS Apex Plus 193 nm argon-fluoride excimer laser. Visual field testing was performed twice before LASIK and 1 day and 24 months after LASIK. Seventy-six points, 6 degrees apart, in the central visual field (Central 30-2) were tested for threshold sensitivity (Humphrey). The mean threshold sensitivity of baseline and post-LASIK visual field examinations was calculated in each patient. Seventy-six points of the Central 30-2 test were divided into 21 clusters corresponding to perimetric nerve-fiber bundles derived from Peridata software version 6.2a (Interzaag AG). The mean threshold sensitivity of each cluster and the visual field indices (mean deviation [MD] and corrected pattern standard deviation [CPSD]) in baseline and follow-up visual fields were compared using analysis of variance. RESULTS: The mean age of the 23 men and 14 women was 31.04 years +/- 6.55 (SD). The mean spherical equivalent refraction was -4.21 +/- 1.66 diopters (D) (range -2.25 to -6.75 D). The mean duration of suction was 42.29 +/- 29.06 seconds. The mean visual field sensitivity at baseline and the 2 follow-up examinations was 25.97 +/- 2.04 dB, 25.70 +/- 1.99 dB, and 27.17 +/- 1.68 dB, respectively (P =.181). There was no difference between preoperative and postoperative visual field clusters except in area 13. In area 13, threshold sensitivity was decreased at 1 day (P =.039) and at the preoperative level at 24 months. The MD of the visual fields was -3.53 +/- 1.67 dB, -3.61 +/- 2.91 dB, and -2.61 +/- 1.66 dB at the preoperative and 2 postoperative examinations, respectively (P =.495). The mean CPSD of the visual fields was 1.76 +/- 1.24 dB, 1.42 +/- 0.85 dB, and 1.74 +/- 0.86 dB, respectively (P =.680). CONCLUSION: Laser in situ keratomileusis did not cause visual field defects in mild to moderate myopic patients who had no risk factors that might render the optic nerve more vulnerable to damage.

Adult↗

PubMed1993

Visual field defects in normal-tension and high-tension glaucoma.

BACKGROUND: Differences in visual field characteristics between normal-tension glaucoma (NTG) and high-tension glaucoma (HTG) have not been established. This study re-examined the problem by pointwise between-group comparison of data obtained with the Humphrey 30-2 program. METHODS: Sixty-eight NTG cases with maximum intraocular pressure (IOP) of 21 mmHg or lower and 62 HTG cases with maximum IOP of 25 mmHg or greater with a mean deviation (STATPAC) greater than -10 decibels (dB) were included. Age, refraction, mean deviation, or sex ratio were matched between the two groups. Total deviation (STATPAC), the difference between the measured threshold and the age-corrected normal reference at each test point of the 30-2 program, was used for pointwise between-group comparisons. Another parameter, total deviation - mean total deviation, was introduced to normalize the total deviation by the overall visual field damage as an index of disease stage. Mean total deviation is the average of total deviations across the test field. Further, logistic discriminant analysis was applied to confirm that the difference at a questioned test point was due to the difference of disease type, but not disease stage, between the two groups. RESULTS: Comparison using total deviation and total deviation - mean total deviation gave similar results, which were collaborated by logistic discriminant analysis. For a given amount of visual field damage, an area just above the horizontal meridian was significantly more depressed in NTG, while HTG had significantly more diffuse visual field damage. CONCLUSION: Visual field defect of NTG differs from that of HTG, which may suggest that different regions of the optic disc are more susceptible to damage in NTG.

Adult↗

PubMed1996

The relationship between visual field size and electroretinogram amplitude in retinitis pigmentosa.

PURPOSE: To determine to what degree visual field size is correlated with electroretinogram (ERG) amplitude among patients with the common forms of retinitis pigmentosa (RP). METHODS: Visual field equivalent diameter to the V4e white test light of the Goldmann perimeter was correlated with log ERG amplitude elicited by 0.5 Hz or 30 Hz full-field flashes of white light. Primary analyses were conducted on data from 583 patients with the common forms of RP. Subset analyses were performed on data from patients with ERG responses with different ranges of amplitude to assess to what extent the correlation depends on ERG amplitude, as well as on data from patients of a given genetic type to determine whether the correlation depends on the mode of transmission. Data from patients with the rhodopsin, Pro23His mutation (n = 38) or with the rhodopsin, Pro347Leu mutation (n = 24) were analyzed to determine the correlation between visual field size and ERG amplitude for patients with the same mutation. RESULTS: Visual field size was significantly correlated with ERG amplitude for every comparison (P < or = 0.0003). Correlations generally were higher for ERGs elicited by 30 Hz flashes (r = 0.62 for the entire sample) than they were for those elicited by 0.5 Hz flashes (r = 0.53 for the entire sample). They were lower for truncated ranges of ERG amplitude, higher for patients with dominant or recessive disease than for patients with x-linked disease or for patients of all genetic types combined, and strong for patients with the same rhodopsin mutation (reaching a value of 0.87). CONCLUSIONS: Visual field size is significantly correlated with ERG amplitude for patients with RP. Correlation depends on the range of ERG amplitudes, the inheritance type, and, particularly, on whether the analysis is confined to a single gene mutation.

Adolescent↗

PubMed2006

Asymmetries and visual field summaries as predictors of glaucoma in the ocular hypertension treatment study.

PURPOSE: To evaluate whether baseline visual field data and asymmetries between eyes predict the onset of primary open-angle glaucoma (POAG) in Ocular Hypertension Treatment Study (OHTS) participants. METHODS: A new index, mean prognosis (MP), was designed for optimal combination of visual field thresholds, to discriminate between eyes that developed POAG from eyes that did not. Baseline intraocular pressure (IOP) in fellow eyes was used to construct measures of IOP asymmetry. Age-adjusted baseline thresholds were used to develop indicators of visual field asymmetry and summary measures of visual field defects. Marginal multivariate failure time models were constructed that relate the new index MP, IOP asymmetry, and visual field asymmetry to POAG onset for OHTS participants. RESULTS: The marginal multivariate failure time analysis showed that the MP index is significantly related to POAG onset (P < 0.0001) and appears to be a more highly significant predictor of POAG onset than either mean deviation (MD; P = 0.17) or pattern standard deviation (PSD; P = 0.046). A 1-mm Hg increase in IOP asymmetry between fellow eyes is associated with a 17% increase in risk for development of POAG. When threshold asymmetry between eyes existed, the eye with lower thresholds was at a 37% greater risk of development of POAG, and this feature was more predictive of POAG onset than the visual field index MD, though not as strong a predictor as PSD. CONCLUSIONS: The MP index, IOP asymmetry, and binocular test point asymmetry can assist in clinical evaluation of eyes at risk of development of POAG.

Antihypertensive Agents↗

PubMed2001

Distinguishing subregions of the human MT+ complex using visual fields and pursuit eye movements.

In humans, functional imaging studies have demonstrated a homologue of the macaque motion complex, MT+ [suggested to contain both middle temporal (MT) and medial superior temporal (MST)], in the ascending limb of the inferior temporal sulcus. In the macaque monkey, motion-sensitive areas MT and MST are adjacent in the superior temporal sulcus. Electrophysiological research has demonstrated that while MT receptive fields primarily encode the contralateral visual field, MST dorsal (MSTd) receptive fields extend well into the ipsilateral visual field. Additionally, macaque MST has been shown to receive extraretinal smooth-pursuit eye-movement signals, whereas MT does not. We used functional magnetic resonance imaging (fMRI) and the neural properties that had been observed in monkeys to distinguish putative human areas MT from MST. Optic flow stimuli placed in the full field, or contralateral field only, produced a large cluster of functional activation in our subjects consistent with previous reports of human area MT+. Ipsilateral optic flow stimuli limited to the peripheral retina produced activation only in an anterior subsection of the MT+ complex, likely corresponding to putative MSTd. During visual pursuit of a single target, a large portion of the MT+ complex was activated. However, during nonvisual pursuit, only the anterolateral portion of the MT+ complex was activated. This subsection of the MT+ cluster could correspond to putative MSTl (lateral). In summary, we observed three distinct subregions of the human MT+ complex that were arranged in a manner similar to that seen in the monkey.

Animals↗

PubMed1994

Technique for determining glaucomatous visual field progression by using animation graphics.

The first two visual field examinations of each of 16 glaucoma suspects and 16 glaucoma patients, who were followed up for a median of 7.46 years with seven examinations, were averaged. Three-dimensional color-coded images of the visual field were then generated. After correcting for test-retest variability, the images, as well as additional interpolated images, were aligned and presented in rapid succession to create an animation sequence. Five glaucoma specialists trained themselves to classify the visual fields as either progressing or not progressing. The interobserver and intraobserver agreement rates were then calculated. Perfect agreement (100% concordance) between the observers was obtained for 18 (56.3%) subjects, and at least 80% concordance was obtained for 27 (84.4%) subjects. Of the eight sequences that were repeated to test intraobserver agreement, four of the five observers had a value of at least 87.5%.

Adult↗

PubMed2004

Distant cortical locations of the upper and lower quadrants of the visual field represented by neurons with elongated and radially oriented receptive fields.

In our previous study of the cytoarchitectonic field 7 of cat cortex we had described neurons with extremely elongated receptive fields (RFs). The long axes of these RFs were oriented radially, towards the centre of the retina. These neurons represented only the lower contralateral part of visual field. They were surrounded from all sides by neurons with clearly different RF properties. We proposed that neurons with a similar radial organization and with RFs in the upper visual field also exist in the cortex but are localized in the area that was distant from the representation of the corresponding lower visual field. We expected to find these neurons in front of the representation of the upper visual field in areas V1, V2 and V3 (fields 17, 18 and 19), behind the central representation in area 21a. This cortical region was studied in five behaving cats. In all animals, neurons with radial RFs in the upper visual field were found in the expected location. As in the lower visual field, their RFs always spared the central visual field. Other RF properties of these neurons were also very similar to those found previously in the lower visual field. It became obvious that neurons with radial RFs are included into the fourth extrastriate crescent with complete contralateral representation. However, in the fourth crescent, RF properties in the central visual field differed significantly from those on the periphery. As a result, neurons with similar radial RFs in the upper and lower visual fields were located in the distant cortical regions, and were separated by the representation of the central visual field presented by the non-radial neurons of the cytoarchitectonic area 21a.

Action Potentials↗

PubMed1997

[Correlations between morphologic measurements of the optic disc using planimetric tests and changes in the visual field in patients with glaucoma].

PURPOSE: To evaluate the relationships between planimetrical measurements of the optic disc and visual field indices in primary open-angle glaucoma patients and glaucoma suspects. MATERIALS AND METHODS: Materials consisted of 64 patients (128 eyes) divided into two groups: glaucoma suspects without any treatment (30 patients, 60 eyes) and early open-angle glaucoma patients already medically treated (34 patients, 68 eyes). All the patients underwent the full, computerized, planimetrical analysis of the optic disc. A special attention was paid to the neuroretinal rim measurements. Visual field examination was performed with automated perimeter Octopus 101 using test dG2. Results were analysed with the use of "Interzeag Peridata" software. RESULTS: We found the statistically significant correlations between neuroretinal rim area and visual field parameters in the glaucoma group. The highest relationship concerned mean defect and compound index of the field. There were no such correlations in glaucoma suspects. Cup/disc ratio correlated more weakly with visual field than neuroretinal rim area. We also analysed mean and extreme values of the neuroretinal rim area in groups of different depth and configuration of visual field defects. CONCLUSIONS: Neuroretinal rim area is a more valuable planimetrical parameter in optic disc analysis than cup/disc ratio. It is also an important factor affecting the visual field, but probably not the only one. There is a significant correlation between visual field quantitative parameters and neuroretinal rim area in primary open-angle glaucoma patients, but in glaucoma suspects that is not true. Digital planimetry proved to be a valuable tool for optic disc biomorphometry and it seems to be an objective method for detecting development of structural changes in glaucoma.

Adolescent↗

PubMed1998

Transient visual field defects induced by transcranial magnetic stimulation over human occipital pole.

Transient visual field defects (VFDs) and phosphenes were induced in normal volunteers by means of transcranial magnetic stimulation (TMS) using a circular magnetic coil of 12.5 cm diameter placed with its lower rim 2-4 cm above the inion in the midline. Subjects had to detect small, bright dots presented randomly for 14 ms in one of 60 locations on a computer screen resulting in a plot of the central 9 degrees of the visual field. In 8 of 17 subjects, transient VFDs were inducible at peak magnetic field strenghts of 1.1-1.4 T. In the central 1-3 degrees, detection of targets was impaired in both the upper and lower visual field, whereas at 4-9 degrees large parts of only the lower visual field were affected with a sharp cut-off along the horizontal meridian. Targets at 1 degree in the lower field were affected with lower TMS intensities than corresponding locations in the upper or peripheral locations in the lower field. Detection of central targets was affected at more caudal stimulation sites than detection of peripheral targets. Phosphenes were elicitable in 14 of 17 subjects at clearly lower field strengths of 0.6-1.0 T. Many subjects perceived chromatophosphenes. From a discussion of the literature on patients with VFDs and the known topography of the human visual system, it is concluded that the transient VFDs at 1-3 degrees are probably due to stimulation of both striate cortex (V1) and extrastriate areas (V2/V3), while VFDs in the lower visual field at eccentricities 4-9 degrees are due to stimulation of V2/V3 but not V1.

Adult↗