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PubMed1989

Static threshold asymmetry in early glaucomatous visual field loss.

Ten normal subjects underwent static threshold visual field testing of both eyes with the Humphrey perimeter, with one eye tested twice. The mean sensitivity of the field seemed virtually identical in the two eyes, with the average difference between the right and left eyes (0.65 decibels [dB]) being no greater than the testing error as reflected in the difference between the same eye tested twice (0.7 dB). The authors provide the mathematical basis for recognizing that a right eye-left eye difference in mean sensitivity might be abnormal. Additional information is needed about the variance of the right eye-left eye difference in the population at large, but present information suggests that a 2-dB difference may be meaningful on a single examination. A 1.5-dB difference is statistically significant if confirmed on a second test, and a difference as small as 1 dB may be meaningful if shown consistently in a series of four examinations. In all cases, nonglaucomatous causes of field abnormality needs to be ruled out, and the generalized asymmetry is most meaningful if it is consistent with asymmetry of cupping or intraocular pressure. Several cases are reported in which a mild (1 dB) generalized depression of the visual field is the only recognizable abnormality in the visual field in eyes with early glaucoma.

Adult↗

PubMed1983

Effect of eye rotation on visual-field map onto superior colliculus and visual cortex.

We used multiunit recording to assess the effect of rotating one eye approximately 90 degrees at about the time of normal eye opening. Rotation of the eye did not alter the topography of the retinal maps onto visual cortex or superior colliculus. The intorted eye drove cells at most recording points in the contralateral visual cortex and superior colliculus. In its ipsilateral colliculus the intorted eye drove cells at about 10% of the recording points; that is, the temporal retina of this eye was quite ineffective in driving collicular cells. In its ipsilateral cortex the intorted eye drove cells at about 30% of the recording sites. The unoperated eye drove cells at all locations in both colliculus and cortex on both sides of the brain. The effects of extorsion were studied only in the superior colliculus. Extorsion and intorsion produced similar results except that extorsion produced a less severe deficit in the ability of the temporal retina to drive cells in its ipsilateral colliculus. Cutting all the extraocular muscles without eye rotation was studied only in the colliculus and produced results similar to those produced by intorsion and extorsion. However, the temporal retina of the operated eye was more effective after muscle cut alone than after intorsion or extorsion. Forcing the animal to use the rotated right eye alone on alternate days during the first 3 mo of life did not decrease the deficits. Almost all recording sites in the right colliculus were driven only by the unoperated left eye. If the left eye was sutured when the right eye was rotated, only the right eye drove cells in the left colliculus, but the two eyes were about equally effective in the right colliculus; however, rather few sites in the right colliculus were binocularly driven. We conclude that both extraocular muscle section and eye rotation reduce the effectiveness of the uncrossed input from the operated eye to the superior colliculus and visual cortex. The effects on the superior colliculus are, however, greater.

Animals↗

PubMed1982

[Topography of early glaucomatous visual field defects in computerized perimetry].

A total of 301 visual fields of 215 glaucoma patients exhibiting early glaucomatous field loss up to Stage II according to Aulhorn were investigated to determine the frequency distribution of absolute and relative defects at the 73 test points of Program 31 of the Octopus computer perimeter. The following results were obtained: (1) The frequency of absolute and relative defects was higher in the upper half of the visual field; (2) The frequency of both absolute and relative defects increased from 6 to 30 degrees eccentricity in the upper visual field, predominantly in the upper nasal quadrant, whereas in the temporal lower quadrant there were less absolute defects but equally frequent relative defects; (3) Defects in the nasal quadrant and above the horizontal meridian are most frequent (between 18 and 30 degrees absolute, between 12 and 30 degrees relative), while temporally of the blind spot and below the horizontal meridian they are quite rare; (4) In the upper half of the field, defects are closer to the fixation point and blind spot; the area between blind spot and macula largely free of defects. --In 71 eyes of 69 patients a similar frequency distribution was found with the Competer computer perimeter (test field 15-20 degrees eccentricity) giving good correlation with the Octopus results. --In 301 eyes of 215 patients with early glaucomatous defects the four test points in the region of the blind spot were evaluated and compared with the results of 121 eyes of 71 patients with ocular hypertension and no field changes. It appears highly probable that an increase in the size of the blind spot is associated with the incidence of field defects. --The distribution of early glaucomatous field defects in 214 eyes revealed a combination of paracentral scotomata with peripheral defects in 75.2%, exclusively peripheral scotomata in 19.6% and exclusively paracentral scotomata in 5.1%. The significance of the results with regard to the pathophysiology of glaucomatous visual field loss is discussed.

Computers↗

PubMed2000

Visual field asymmetries in attention and learning.

It has been suggested that attentional resolution is greater in the lower than in the upper visual field. As there is no corresponding asymmetry between the areas in the primary visual cortex where the input from upper and lower visual fields is processed, an 'attentional filter' has been proposed to act in one or more higher visual cortical areas in order to constrict the availability of visual information to the level of awareness. To investigate this, a visual search array was presented to the entire visual field and reaction times from upper and lower visual fields compared. In a second experiment, subjects were trained in detecting targets in different visual fields. There was no significant difference between reaction times for targets presented in either upper or lower visual fields when the array was presented to the entire visual field. However, when the array was restricted to either the upper or lower visual fields, reaction times were significantly slower for detection in the upper visual field.

Adolescent↗

PubMed2006

The divided visual field paradigm: methodological considerations.

The divided visual field methodology has been used to examine a wide variety of lateralised processes. When conducting such studies it is important to employ a number of strict controls in order to maximise the effectiveness of the paradigm for examining the processing of stimuli by each hemisphere. The use of these controls is discussed in this paper. The following issues are discussed: selection of participants; methods of fixation control; presenting stimuli unilaterally; methods of responding; and measures that can be taken. The use of the divided visual field paradigm to examine interhemispheric cooperation is also discussed. Employing the recommended controls provides an effective and relatively easy method of examining the role of each hemisphere in the processing of stimuli.

Brain↗

PubMed2006

Vigabatrin-attributable visual field defects in patients with intractable partial epilepsy.

INTRODUCTION: Vigabatrin (VGB) is implicated to cause visual field defects. We estimated the prevalence, described the characteristics and investigated the risk factors of VGB-attributable visual field defects. METHODS: Patients with intractable partial epilepsy under VGB add-on treatment received static perimetric examinations. Visual field charts were reviewed and interpreted using a three-grade system. Clinical features and therapeutic courses were analyzed for possible risk factors. RESULTS: Visual field defects in at least one eye were detected in 27 (79%) of 34 patients. In the subgroup of 27 patients with both eyes reliably tested, 16 (59%) had bilateral defect, among whom seven were severely involved and showed nasally dominant, crescent or concentric defect. Five patients had unilateral visual field defects. Four out of the 27 affected patients reported blurred vision. No statistically significant differences were noted between patients with and without visual field defects in terms of gender, age, duration or etiology of the epilepsy, and duration, maximum daily dose, or cumulative dose of VGB. CONCLUSIONS: There was a high prevalence of VGB-attributable visual field defects. No risk factors could be identified. Routine initial and regular follow-up of visual field examination, especially that focusing within a range of central fixation to 60 degrees, should be performed in patients on VGB.

Adult↗

PubMed1983

The Peritest automatic perimeter in screening for glaucomatous visual field defects.

The ability of the Peritest to screen for glaucomatous defects of the visual field was studied by using this automatic perimeter to examine the visual fields of 69 eyes with chronic open-angle glaucoma and 46 normal eyes after manual perimetry had been performed. The Peritest correctly identified 62 (90%) of the glaucomatous eyes as having visual field abnormalities; the other 7 eyes (10%) had false-positive results. Of the 46 normal eyes, 36 (78%) were correctly identified as having normal visual fields; the other 10 eyes (22%) were incorrectly identified as having visual field abnormalities. Thus, the overall rate with which eyes were correctly classified as having normal or abnormal visual fields was 85%, and the rate with which fields were falsely identified as having glaucomatous abnormalities was 15%.

Computers↗

PubMed1993

On the interdependency between attentional biases and visual field effects with bilateral presentations of stimuli.

Previous research indicates that bilateral presentations of visual stimuli yield greater visual field differences than unilateral ones. Although this fact has generally been interpreted by reference to functional models of hemispheric specialization, an alternative explanation has been offered, which suggests that it is artifactually caused by an attentional bias (AB). Indeed, consistent positive correlations between the direction of ABs and that of visual field effects have been reported. However, this relationship remains uncertain since different tasks, presented at different moments, have been used in order to document it. We report on a bilateral presentation task which controlled this potential discrepancy by mixing trials measuring ABs with those assessing visual field effects. We showed that, in a group of dextrals, the direction of the visual field effect is intimately correlated with that of the AB; subjects with a right AB showed a right visual field advantage, whereas subjects with a left AB showed a left visual field advantage; moreover, subjects with no overall AB did not show any visual field advantage. The results of this experiment confirm the fact that the formally reported correlations between the direction of ABs and visual field effects are determined by individual differences in ABs rather than by the task being used to assess them. This observation points to the necessity for further research on variables affecting the between-subjects variability in ABs with the use of bilateral presentations of visual stimuli.

Adult↗

PubMed1990

Aphakic visual fields by automated perimetry.

Accurate testing of the visual field of aphakic patients is demanding due to the optical distortion induced by high plus corrective lenses. This testing procedure can be improved by using an aspheric contact lens instead of a full-aperture loose trial lens. We found that the contact lens enhances the ability of the pattern-deviation printout of the Statpac analysis to identify glaucomatous visual field abnormalities in program 30-2 of the Humphrey Visual Field Analyzer.

Aged↗

PubMed2003

Corneal thickness as a risk factor for visual field loss in patients with preperimetric glaucomatous optic neuropathy.

PURPOSE: To determine whether central corneal thickness (CCT) is a risk factor for visual field loss development among patients diagnosed with preperimetric glaucomatous optic neuropathy (GON). DESIGN: Observational cohort study. METHODS: The study included 98 eyes of 98 patients with GON, with a mean follow-up time of 4.3 +/- 2.7 years. Diagnosis of GON was based on masked assessment of optic disk stereophotographs. All patients had normal standard automated perimetry visual fields at baseline. Criteria for visual field abnormality were derived from a prior study. Several clinical factors (CCT, intraocular pressure, vertical cup-to-disk ratio, refraction, age, gender, family history of glaucoma, high blood pressure, cardiovascular disease, and migraine) were investigated to ascertain whether there is an association with development of repeatable visual field loss. Cox proportional hazards models were used to obtain hazard ratios (HR) and identify factors that predicted which individuals developed glaucomatous visual field loss during the follow-up period. RESULTS: Thirty-four patients (35%) developed repeatable visual field abnormality during follow-up. In multivariate analysis, risk factors that predicted the development of visual field loss were a thinner CCT (adjusted HR = 1.62/40 microm thinner; P =.023; 95% confidence interval [CI]: 1.07-2.45), higher baseline intraocular pressure (adjusted HR = 1.07/mm Hg; P =.022; 95% CI: 1.01-1.14), and larger baseline vertical cup-to-disk ratio (adjusted HR = 1.63/0.1 larger; P =.009; 95% CI: 1.13-2.35). The mean +/- standard deviation CCT of GON patients who developed visual field loss was 543 +/- 36 microm compared with 565 +/- 35 microm of those who did not develop visual field abnormalities (P =.005, Student t test). CONCLUSIONS: Central corneal thickness is a risk factor for development of visual field loss among patients diagnosed with preperimetric GON. It is important to consider CCT when establishing target intraocular pressure of patients with GON.

Cohort Studies↗

PubMed1989

Judging the reflection of misoriented patterns in the right and left visual fields.

The reported study demonstrates that performance asymmetries between normal or reflected letters presented in the right and left visual field favors the right visual field when stimulus patterns are blocked and rotated 90 degrees clockwise and favors the left visual field when they are blocked and rotated 90 degrees counterclockwise. When stimuli are rotated, the orientations of the patterns define a coordinate system that is independent of upright. It is suggested that our results are due to subjects sampling the different areas in the visual field relative to this coordinate system. The right visual field was given priority when the patterns were oriented so their "tops" were pointing rightward and the left visual field was given priority when the patterns were oriented so their tops were pointing leftward. Neither differences in the stimulus image on the retina in the two rotated conditions, eye movements, nor direct access to one hemisphere or the other could account for these effects.

Adult↗

PubMed2001

Glaucoma surgery with or without adjunctive antiproliferatives in normal tension glaucoma: 2 Visual field progression.

BACKGROUND: Reduction of intraocular pressure by 20-30% with glaucoma drainage surgery slows disease progression in normal tension glaucoma (NTG). It is not clear whether adjunctive antiproliferative agents are necessary or safe in eyes at low risk for scarring. METHOD: 61 eyes of 61 white patients with NTG who had undergone a primary guarded fistulising procedure were reviewed. 20 eyes had no antiproliferatives (nil), 29 had peroperative 5-fluorouracil (5-FU), and 12 had peroperative mitomycin C (MMC). Pointwise linear regression analysis (PROGRESSOR for Windows software) was applied to their visual field series starting with the first visual field following surgery and adding subsequent visual fields one at a time. Progression of visual field loss was defined as the appearance of a regression slope 1 dB per year or more with a significance of p<0.01 at one or more visual field locations which remained consistent with the addition of two of three successive visual fields. Time updated covariate analysis was used to determine the relation between variables that changed with time, such as IOP, and the risk of progression. RESULTS: The median percentage IOP reduction was 24.4 for the nil group, 38.0 for the 5-FU group, and 47.5 for the MMC group (p=0.001). There was a statistically significant relation between percentage change in IOP and risk of visual field progression in the subsequent 6 month period for all patients analysed as one group, hazard ratio = -0.021 (p=0.002). There was a statistically significantly increase in the risk of visual field progression for the MMC group compared with the 5-FU group, hazard ratio = 1.51 (p=0.02). CONCLUSION: In NTG patients, the IOP reduction produced by drainage surgery reduces the risk that visual field progression may be reduced after drainage surgery; this is related to the level of IOP reduction. The percentage drop in IOP during a given time is related to the risk of subsequent visual field progression. However, the use of MMC is associated with a greater risk of visual field progression despite a greater fall in IOP. This visual field deterioration may be related to the functional loss produced by late postoperative complications which have been reported at a higher rate in this group. The use of adjunctive perioperative 5-FU should maintain a suitable target IOP with preservation of visual function without the additional complications and associated visual deterioration seen with adjunctive MMC.

Aged↗

PubMed2006

Structure-function relationships in the human visual system using DTI, fMRI and visual field testing: pre- and post-operative assessments in patients with anterior visual pathway compression.

The focus of this project is to improve our understanding of the relationships between brain structure and function in patients presenting with anterior visual pathway compression using functional MRI (fMRI), visual field(VF) maps and diffusion tensor imaging (DTI). Significant visual loss can occur when large pituitary lesions compress the optic chiasm. Surgical resection of these lesions decompresses the chiasm and can lead to visual recovery. In this preliminary study, we selected patients presenting with slowly progressive visual loss secondary to a compressive pituitary region mass. Using preoperative DTI data, we reconstructed white matter projections of the optic radiations and demonstrated a structural correlation with functional vision as quantified by formal visual field mapping and fMRI. The structural data generated through a fiber tracking algorithm may represent a potentially powerful tool to better understand functional visual deficits in patients with anterior visual pathway compression. Furthermore, we believe that specific patterns in preoperative DTI data may predict the likelihood of postoperative visual recovery in a select group of patients.

Brain↗

PubMed2002

Is visual field constriction in epilepsy patients treated with vigabatrin reversible?

OBJECTIVE: To evaluate the reversibility of vigabatrin associated visual field constriction. BACKGROUND: Visual field constriction (VFC) occurs in approximately 40 % of epilepsy patients under treatment with vigabatrin (VGB). There is still controversy about whether VGB-associated VFC is reversible. From a cross-sectional study there is evidence that VFC does not reverse three to six months after stopping VGB treatment. So far, there are no long term studies on this subject. METHODS: We performed a follow-up study on 15 epilepsy patients (eight women, seven men, median age 45 (21-58) years) with VGB-associated VFC but otherwise normal ophthalmological examination. Kinetic and static perimetry was performed one and two years after VFC was diagnosed (baseline examination). Visual field size at first and at second year-follow-up was compared with the baseline examination. Because discontinuation of VGB-treatment was dependant on clinical needs, patients either stopped VGB treatment before or after VFC was diagnosed. In a small group of patients VGB treatment was continued despite of VFC. RESULTS: There was no statistically significant difference in visual field size comparing baseline values with first year and second year follow-up examinations either in patients who stopped VGB treatment (n = 11) or in patients who continued VGB treatment on a reduced dosage (n = 4). CONCLUSION: Although our data are based on a relatively small group of patients there is evidence that VFC resulting from VGB treatment is not reversible in epilepsy patients after stopping the drug.

Adult↗

PubMed2002

Homonymous visual field defects and stroke in an older population.

PURPOSE: The objective of the present study was to describe the prevalence of homonymous visual field defects in a defined older urban population and associations with self-reported stroke. METHODS: Homonymous visual field defects were assessed from screening automated visual field tests of both eyes in 3654 persons aged > or =49 years who were participating in the Blue Mountains Eye Study. This represented 82.4% of eligible residents from a defined area west of Sydney, Australia. A detailed eye examination was performed, and the medical history was taken. Masked grading of visual fields was used to classify the presence of homonymous visual field defects. RESULTS: Homonymous visual field defects were found in 25 persons (prevalence 0.8%, 95% CI 0.5% to 1.1%). Stroke history was reported by 194 participants (5.3%, 95% CI 4.6% to 6.1%). A strong relationship was found between homonymous visual field defects and history of stroke, age-, and sex-adjusted odds ratio (OR) 23.4 (95% CI 9.9 to 55.7). Homonymous field defects were present in 8.3% of all persons who reported experiencing a stroke. Among those with homonymous field defects, 52% reported a history of stroke. Only 2 of 10 persons (20%) with homonymous field defects without a history of stroke reported having stopped driving, whereas 6 of 9 (67%) reporting stroke had stopped driving (P=0.07). Increasing age (OR 1.4 per decade, 95% CI 1.2 to 1.8) was significantly associated with homonymous visual field defects, with adjustment for sex, whereas a history of hypertension (OR 2.7, 95% CI 1.2 to 6.1), diabetes (OR 2.1, 95% CI 1.4 to 3.2), and renal impairment (OR 2.8, 95% CI 1.0 to 8.1) also was associated, with adjustment for age and sex. CONCLUSIONS: This study provides accurate prevalence data for homonymous visual field defects in an older population. About half the participants did not report stroke.

Age Distribution↗

PubMed2002

Topographical analysis of the onset VEP in the detection of paracentral visual field defects.

Transient visual evoked potentials (VEP) were recorded simultaneously from 16 electrodes evenly placed over posterior scalp locations covering the occipital, posterior parietal and temporal areas. Interhemispheric amplitude difference of the N70 deflection was established across 6 homologous lateral electrode pairs in 15 normal controls and 32 patients with chiasmatic or retrochiasmatic cerebral lesions. Twenty-three of these had known homonymous or bitemporal field defects while 9 had normal fields on routine perimetry. Significant interhemispheric asymmetry of any single electrode pair occurred in 55% of the 32 patients with known pathology, while the cumulative yield of all electrode pairs was over 80 percent. The diagnostic yield of individual electrode pairs was significantly different: the electrode pair placed over the temporo-parietal junction detected the highest number of abnormalities. The cumulative abnormality taken over all lateral electrode pairs could be described with a curve well fitted with a probability summation function. It is inferred that the contribution of several independent generator sources is reflected in the N70 of the pattern onset VEP. The results suggest that multichannel recording of the interhemispheric amplitude distribution of the N70 of the onset VEP is useful for the evaluation of paracentral visual field defects.

Adult↗

PubMed2006

Development and validation of a computerized expert system for evaluation of automated visual fields from the Ischemic Optic Neuropathy Decompression Trial.

BACKGROUND: The objective of this report is to describe the methods used to develop and validate a computerized system to analyze Humphrey visual fields obtained from patients with non-arteritic anterior ischemic optic neuropathy (NAION) and enrolled in the Ischemic Optic Neuropathy Decompression Trial (IONDT). The IONDT was a multicenter study that included randomized and non-randomized patients with newly diagnosed NAION in the study eye. At baseline, randomized eyes had visual acuity of 20/64 or worse and non-randomized eyes had visual acuity of better than 20/64 or were associated with patients refusing randomization. Visual fields were measured before treatment using the Humphrey Field Analyzer with the 24-2 program, foveal threshold, and size III stimulus. METHODS: We used visual fields from 189 non-IONDT eyes with NAION to develop the computerized classification system. Six neuro-ophthalmologists ("expert panel") described definitions for visual field patterns defects using 19 visual fields representing a range of pattern defect types. The expert panel then used 120 visual fields, classified using these definitions, to refine the rules, generating revised definitions for 13 visual field pattern defects and 3 levels of severity. These definitions were incorporated into a rule-based computerized classification system run on Excel(R) software. The computerized classification system was used to categorize visual field defects for an additional 95 NAION visual fields, and the expert panel was asked to independently classify the new fields and subsequently whether they agreed with the computer classification. To account for test variability over time, we derived an adjustment factor from the pooled short term fluctuation. We examined change in defects with and without adjustment in visual fields of study participants who demonstrated a visual acuity decrease within 30 days of NAION onset (progressive NAION). RESULTS: Despite an agreed upon set of rules, there was not good agreement among the expert panel when their independent visual classifications were compared. A majority did concur with the computer classification for 91 of 95 visual fields. Remaining classification discrepancies could not be resolved without modifying existing definitions. Without using the adjustment factor, visual fields of 63.6% (14/22) patients with progressive NAION and no central defect, and all (7/7) patients with a paracentral defect, worsened within 30 days of NAION onset. After applying the adjustment factor, the visual fields of the same patients with no initial central defect and 5/7 of the patients with a paracentral defect were seen to worsen. CONCLUSION: The IONDT developed a rule-based computerized system that consistently defines pattern and severity of visual fields of NAION patients for use in a research setting.

Automation↗

PubMed1997

Visual field enlargement by neuropsychological training of a hemianopsia patient.

A 58-year old hemianopsia patient was submitted to a two-fold neuropsychological training in order to enhance visual functions in the affected part of his visual field. At first, the visual field was measured perimetrically, to serve as a starting measurement with which after-measurements could be compared. Then, the first training was started: the border area between the intact and the defect visual field was being stimulated by small light spots. The training consisted of repetitive detection threshold measurements. After 27 one-hour sessions, the visual field was being measured again. The visual field appeared to have been enlarged 5 to 12 degrees in the direction of the affected hemifield and contrast-sensitivity thresholds to have been decreased almost at every point in the stimulus-array. Then, a second training started; an eye-movement training. Again, the border area, now shifted outwards, was stimulated. This time, the stimulus concerned a short presentation of light (< 200 msec.) after which the subject, to the best of his abilities had to make an eye-movement to the perceived stimulus-site. Also, he had to categorize the quality of his perception as well as the direction in which the stimulus was thought to be perceived. After 30 sessions, the visual field appeared to have 'grown' just a little bit more, but this seems not to be a significant enlargement. More important, the number of detected stimuli in the supposed 'blind' area had increased, as had the accuracy of the localization of the stimuli. Preliminary results of the detection training of a second subject, also 58 years of age, are presented. Finally, planned actions are discussed.

Eye Movements↗