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PubMed1993

An evaluation of clusters in the glaucomatous visual field.

We used a statistical cluster analysis to analyze patterns of loss in 76 visual fields with typical glaucomatous defects to identify natural groupings of test locations in the visual field. Eleven clusters in the Octopus Program G1 (Interzeag, Inc., Northboro, Massachusetts) visual field were thus defined. In a separate population of 70 early glaucomatous and 70 age-matched normal visual fields, the local mean defects within these clusters and the global mean defect were calculated to assess their relative abilities to discriminate between the two groups. The 11 clustered mean defects collectively had a sensitivity of 90% and a specificity of 93%; the global mean defect had a sensitivity of 81% and a specificity of 91%. Additionally, we examined the long-term fluctuation clusters of test locations compared to the long-term fluctuation of individual test locations. Four hundred ten visual fields of 93 clinically stable eyes of 67 patients with glaucoma, as well as 210 visual fields of 105 eyes of 105 normal subjects were studied. In the stable glaucoma group, mean fluctuation of clustered test locations was 3.5 dB2, and mean fluctuation of individual test locations was 7.0 dB2. In the normal group, the respective values were 0.6 dB2 and 1.8 dB2. Cluster analysis was effective in detecting localized loss and in dampening long-term fluctuation. We studied the use of clusters in distinguishing normal from glaucomatous as well as stable from deteriorating visual fields.

Adult↗

PubMed2003

Correlation analysis of visual field thresholds and scanning laser ophthalmoscopic optic nerve head measurements in glaucoma.

In a cross-sectional study of 50 consecutive primary open-angle glaucoma cases, full threshold 30-2 visual fields on Humphrey Visual Field Analyser were correlated to stereometric parameters obtained using a scanning laser ophthalmoscope (HRT II). The strength of linear correlation between the stereometric parameters and visual thresholds was used to generate a correspondence map between the optic disc and the visual field. Rim/disc area ratio and cup/disc area ratio correlated with the visual thresholds at the highest number of points in the visual fields. Thresholds at superior hemifield locations correlated best with the rim/disc area ratio and cup/disc area ratio in the inferonasal sector and the ones in the inferior hemifield correlated best with the rim/disc area ratio and cup/disc area ratio in the superotemporal sector. Optic disc parameters correlated better with inferior field locations and non-edge points than superior field locations and edge points. The data indicate that rim/disc area ratio and cup/disc area ratio measurements on HRT II have a good correlation with visual field damage seen on automated visual fields.

Adult↗

PubMed1992

A comparison of five methods for estimating general glaucomatous visual field depression.

The separation of local and diffuse visual field loss is important for evaluating the nature and extent of glaucomatous visual field damage. Here, five automated methods for estimating diffuse loss in glaucomatous visual fields (as measured with the Octopus G1 program) are compared. Four are taken from the published literature, and one is introduced in this investigation. It is shown that the new index (here called diffuse loss) provides the best agreement with a value determined using a more empirical approach.

Glaucoma↗

PubMed1990

The effect of jogging on visual field indices.

The Humphrey 30-2 visual field was examined 9 times before and after an 8-km jog in one subject, whose contrast sensitivity had been found to improve after jogging. The mean deviation improved statistically significantly suggesting better sensitivity of the visual system after jogging. Our results suggest that in some individuals physical exercise influences the factors which lie behind the visual field long-term fluctuation.

Contrast Sensitivity↗

PubMed1998

Multifocal topographic visual evoked potential: improving objective detection of local visual field defects.

PURPOSE: To investigate the relationships between the pattern stimulation of different parts of the visual field (up to 25 degrees of eccentricity), the electrode position, and the cortical response to improve objective detection of local visual field defects. METHODS: The human visual evoked potential (VEP) was assessed using multifocal pseudorandomly alternated pattern stimuli that were cortically scaled in size. Monopolar and bipolar electrode positions were used. The visual field was investigated up to 26 degrees of eccentricity. Twelve normal subjects and seven subjects with visual field defects of different nature were studied. RESULTS: Although the monopolar response is heavily biased toward the lower hemifield, bipolar leads overlying the active occipital cortex (straddling the inion) demonstrate good signals from all areas of the visual field tested. The amplitude is almost equal for the averaged upper and lower hemifields, but the polarity is opposite, causing partial cancellation of the full-field VEP. The degree of cancellation depends mainly on latency differences between the vertical hemifields. The bipolar VEP corresponded well with Humphrey visual field defects, and it showed a loss of signal in the scotoma area. CONCLUSIONS: The multifocal VEP demonstrates good correspondence with the topography of the visual field. Recording with occipital bipolar electrode placement is superior to standard monopolar recording. To avoid a full-field cancellation effect, a separate evaluation of upper and lower hemifields should be used for the best assessment of retinocortical pathways. This technique represents a significant step toward the possible application of the multifocal VEP to objective detection of local defects in the visual field.

Adult↗

PubMed2004

Full-field ERG, multifocal ERG and multifocal VEP in patients with retinitis pigmentosa and residual central visual fields.

PURPOSE: To evaluate (with three different electrophysiological methods) the residual retinal function in a selected group of patients with retinitis pigmentosa and remaining small central visual fields. METHODS: Fourteen patients from several different genetic subgroups, who had been followed with visual acuity and visual field testing for periods up to 32 years, were examined. Ophthalmological examination included full-field electroretinography (ERG), multifocal electroretinography (mfERG) and multifocal visual evoked potential (mfVEP). RESULTS: The ERGs were severely reduced in all patients. The mfERGs demonstrated the residual central retinal function in five of the patients. The mfVEPs showed measurable amplitudes centrally in most of the patients. The follow-up examinations demonstrated the slowly progressive course of the disease with preservation or only slight further loss of visual fields over a period of 7-32 years. CONCLUSION: Patients with retinitis pigmentosa may not always follow the typical natural course with progressive loss of visual fields, which may in some patients remain unaffected over several decades. Multifocal ERG and mfVEP may be clinically useful for evaluating remaining visual function in these patients.

Adult↗

PubMed1999

Visual field defects after temporal lobe resection: a prospective quantitative analysis.

OBJECTIVE: To evaluate and quantify prospectively visual field changes in patients undergoing temporal lobe resections for intractable epilepsy. BACKGROUND: Visual field abnormalities occur after temporal lobe resections for epilepsy; however, we have not encountered published reports using automated static visual field analysis. METHODS: Humphrey visual fields (program 30-2) were obtained before and after partial temporal lobe resection in 32 consecutive patients with intractable epilepsy. A quantitative point-by-point analysis was made in the affected superior quadrant, and the defects were averaged for the whole patient group. RESULTS: Thirty-one patients developed a visual field defect, but none was aware of the defect. The points nearest fixation were relatively spared. The defects were greatest in the sector closest to the vertical meridian in the eye ipsilateral to the resection. The ipsilateral and contralateral mean field defects also differed in both topography and depth. A significant correlation was found between the extent of lateral temporal lobe resection and the degree of the defect in the contralateral eye. CONCLUSIONS: There are differences in the shape and depth of the ipsilateral and the contralateral field defects not previously reported. These findings demonstrate that certain fibers from the ipsilateral eye travel more anteriorly and laterally in Meyer's loop, and support the hypothesis that visual field defects due to anterior retrogeniculate lesions are relatively incongruous because of anatomic differences in the afferent pathways. Automated perimetry is a sensitive method of evaluating and quantifying visual field defects.

Adolescent↗

PubMed1979

Correlation of CAT scan and visual field defects in vascular lesions of the posterior visual pathways.

Thirty-nine patients with various types of isolated homonymous hemianopias resulting from ischaemic lesions in the posterior parts of the cerebral hemisphere was examined by CAT scanning. Most had localised low density lesions withing the distribution of the posterior cerebral artery. The location of the lesion (deduced from a separate anatomical study of postmortem brain cut in the plane of the CAT scanner) was correlated with visual field defects. Lesions giving rise to quadrantic defects were smaller than those causing total hemianopias; lower quadrantic defects tended to occur in superior cuts and vice versa. Macular sparing was associated with survival of the occipital pole in some instances. Bilateral cases had a higher prevalence of associated defects.

Adult↗

PubMed1989

Assessing the utility of reliability indices for automated visual fields. Testing ocular hypertensives.

Monocular (right eye) visual fields were recorded with the Humphrey Visual Field Analyzer (30-2 Program) at baseline as well as 6 and 12 months later in 120 patients with established ocular hypertension. Indices of field reliability (fixation loss, less than 20%; false-positives and false-negatives, less than 33%) and field sensitivity (mean deviation [MD] and pattern standard deviation [PSD]) were examined. At baseline, 35% of patients exhibited low reliability (LR) fields, a figure which decreased to approximately 25% at 6 and 12 months, respectively. During this period, over 50% of patients produced at least one LR field, whereas 8.3% were unable to produce even one reliable field. Exhibition of a LR field appeared to be independent of patient age. Fixation errors, the major cause of LR fields, decreased by approximately 10% over the 12-month period; most patients had between 20 and 32% fixation errors. The incidence of significant defects identified by PSD was greater than that for MD; this was true for both reliable and LR fields. It is suggested that increasing the fixation loss criteria for assessing patient reliability to a 33% cutoff might substantially increase the percentage of fields graded reliable with minimal effect on the sensitivity or specificity of the test.

Adult↗

PubMed1992

Effect of mydriasis on visual field area in retinitis pigmentosa.

PURPOSE: The effect of mydriasis on Goldmann visual field area in patients with retinitis pigmentosa has not been suitably defined. The aim of this study is to determine whether visual field area in these patients varies with pharmacologic mydriasis. METHODS: Fifteen adult patients with retinitis pigmentosa were studied prospectively. Goldmann visual fields with II4e and V4e isopters were obtained in both eyes before and after full pharmacologic mydriasis of the right eye. The isopter areas were quantified and analyzed to determine the effect of mydriasis on visual field area. RESULTS: The difference in the right eye isopter areas was compared with the difference in the left eye isopter areas using paired t tests, where the differences were computed from areas obtained before and after dilation of the right eye. Mydriasis had no significant effect on the visual field in terms of isopter area difference (II4e, P = 0.87; V4e, P = 0.45) and percent change in isopter area (II4e, P = 0.81; V4e, P = 0.24). CONCLUSION: Pharmacologic mydriasis had no appreciable effect on the Goldmann visual field area in a selected group of patients with retinitis pigmentosa. These findings suggest that visual fields of such patients obtained in the dilated or undilated state can be meaningfully compared.

Adult↗

PubMed2003

Three-dimensional electric field visualization utilizing electric-field-induced second-harmonic generation in nematic liquid crystals.

An electric-field-induced second-harmonic-generation signal in a nematic liquid crystal is used to map the electric field in an integrated-circuit-like sample. Since the electric-field-induced second-harmonic-generation signal intensity exhibits a strong dependence on the polarization of the incident laser beam, both the amplitude and the orientation of the electric field vectors can be measured. Combined with scanning second-harmonic-generation microscopy, three-dimensional electric field distribution can be easily visualized with high spatial resolution of the order of 1 microm.

Journal Article↗

PubMed1993

Sectorization of the central 30 degrees visual field in glaucoma.

PURPOSE: To determine an optimal sector pattern of the central 30 degrees visual field in glaucoma by mathematically analyzing the visual field data of primary open-angle glaucoma (POAG) without any assumption such as the retinal nerve fiber layer anatomy. METHODS: One hundred three visual fields of the 30-2 program of the Humphrey Field Analyzer obtained from 103 POAG patients of early to moderately advanced stage were included. Based on the interpoint correlation of deviation of the measured threshold value from the age-corrected normal reference value (total deviation, STATPAC), test points of the 30-2 program were mathematically clustered using the VARCLUS procedure, a new clustering algorithm developed by the SAS Institute. The sector value, which summarizes the visual field performance of the clustered test points (sector), also was calculated. RESULTS: The 30 degrees central visual field was divided into 15 sectors consisting of at least 3 points. The distribution of sectors was compatible with the projection of nerve fiber layers. There was no sector extending over the horizontal meridian, but the sector pattern was not completely symmetrical around it. Linear regression analysis of the sector values against the mean deviation (STATPAC) suggested that the index is useful in following visual field performance of each sector. CONCLUSION: The sector pattern and sector values obtained were considered useful in studying the visual field data of glaucoma.

Algorithms↗

PubMed2002

Quantification of interpoint topographic correlations of threshold values in glaucomatous visual fields.

PURPOSE: The authors sought to quantify neighboring and distant interpoint correlations of threshold values within the visual field in patients with glaucoma. METHODS: Visual fields of patients with confirmed or suspected glaucoma were analyzed (n = 255). One eye per patient was included. Patients were examined using the 32 program of the Octopus 1-2-3. Linear regression analysis among each of the locations and the rest of the points of the visual field was performed, and the correlation coefficient was calculated. The degree of correlation was categorized as high (r(2) > 0.66), moderate (0.66 > or = r(2) > 0.33), or low (r(2) < or = 0.33). The standard error of threshold estimation was calculated. RESULTS: Most locations of the visual field had high and moderate correlations with neighboring points and with distant locations corresponding to the same nerve fiber bundle. Locations of the visual field had low correlations with those of the opposite hemifield, with the exception of locations temporal to the blind spot. The standard error of threshold estimation increased from 0.6 to 0.9 dB with an r(2) reduction of 0.1. CONCLUSION: Locations of the visual field have highest interpoint correlation with neighboring points and with distant points in areas corresponding to the distribution of the retinal nerve fiber layer. The quantification of interpoint correlations may be useful in the design and interpretation of visual field tests in patients with glaucoma.

Female↗

PubMed1997

Automatic detection of glaucomatous visual field progression with neural networks.

OBJECTIVE: To evaluate computerized neural networks to determine visual field progression in patients with glaucoma. METHODS: Two hundred thirty-three series of Octopus G1 visual fields of 181 patients with glaucoma were collected. Each series was composed of 4 or more reliable visual fields from patients who had previously undergone automated perimetry. The visual fields were independently evaluated in a masked fashion by 3 experienced observers (K.N.-M, M.W., and J.C.) and were judged to show progression based on the agreement of 2 observers. The stable and progressed series were matched for mean defect at baseline. The threshold data were submitted to a back propagation neural network that was trained to classify each series as stable or progressed. Two thirds of the data were used for the training and the remaining one third to test the performance of the network. This was repeated 3 times to classify all of the series (changing the training and test series). RESULTS: Fifty-nine series of visual fields showed progression and 151 were judged stable. Neural network sensitivity was 73% and specificity was 88% (threshold for progression = 0.5). The concordance of the neural network with the observers was good (0.50 < or = kappa > or = 0.64). CONCLUSIONS: A neural network can be trained to recognize visual field progression in good concordance with experienced observers. Neural networks may be used to aid the physician in the evaluation of glaucomatous visual field progression.

Aged↗

PubMed2002

The effect of ocular dominance on visual field testing.

PURPOSE: During standard automated perimetry (SAP), some patients experience visual disturbances in the tested eye while the other eye is covered with an opaque occluder. It is possible that a binocular interaction producing an inhibitory response in the nonoccluded eye, such as rivalry or Ganzfeld blankout, may be the causative factor, particularly when the dominant eye is occluded. The objective of this experiment was to determine whether subjective visual disturbances occurring during conventional perimetric test conditions were related to ocular dominance and to investigate the effect of these disturbances on measurements made during threshold visual field analysis. METHOD: Ocular dominance was determined by questioning and objective testing on 55 normal subjects. Each subject underwent program 24-2 Full Threshold SAP on a Humphrey Field Analyzer, and an opaque black patch was used to occlude the nontested eye. After testing, patients were asked to report symptoms of visual disturbance characteristic of rivalry or blankout, and the relationship between ocular dominance and visual disturbances was investigated. To determine whether symptoms of rivalry or blankout had affected visual field quantification, comparisons of short-term fluctuation, mean deviation, and false-negative errors were performed between eyes with and without visual disturbances. RESULTS: A total of 24 of 55 subjects reported visual disturbances consistent with rivalry or blankout (44%). Sixteen subjects complained of the phenomenon in one eye, and eight complained of the phenomenon in both eyes. Of the 16 experiencing disturbances in one eye only, nine cases occurred during occlusion of the dominant eye. The association between ocular dominance and visual disturbances was not found to be significant (p > 0.10). No significant differences in short-term fluctuation (p = 0.78), mean deviation (p = 0.64), or false-negative errors (p = 0.10) were found between eyes with and without visual disturbances. CONCLUSIONS: Patients undergoing standard automated perimetry with opaque patch occlusion of the nontested eye often experience visual disturbances consistent with rivalry or blankout, although these disturbances do not cause increased within-test variability or reduced sensitivity as quantified by visual field global indices. In terms of summary visual field indices, ocular dominance does not appear to affect visual field test results.

Adult↗

PubMed1978

Visual field representation in the newborn rabbit's cortex.

The representation of the visual field in the newborn rabbit's visual cortex appears on about the 10th day after the animal's birth coinciding with the time of its eye opening. Initially the visual response is obtained from a small anterolateral segment of the visual area of the cortex representing a few degrees of the extreme nasal vision of the animal. Even at this early stage, the visually responsive area of the rabbit's cortex seems to organize into V1 and V2 with the binocular response confined to V1 only. By the 15th day after the animal's birth, the visually responsive area in the newborn rabbit extends medially and posteriorly over the cortex, representing more of the animal's temporal and superior visual fields. By this time the binocular response is established over a narrow zone of the animal's visual cortex, representing a few degrees of the nasal visual field, on either side of the boundary between V1 and V2. Between the 16th and 17th day after the rabbit's birth, the cortical representation of the animal's visual field extends medially to the margin of the fissura sagittalis lateralis and caudally to the posterior pole of the hemisphere. In this visually responsive area of the cortex, the band-shaped visual field of the newborn rabbit is asymmetrically represented.

Animals↗

PubMed1993

The effect of lens opacity on the resolution visual field in normal subjects.

The sensitivity of the visual field declines with age. The density of the crystalline lens increases with age and may be partly responsible for the decline in sensitivity. To determine whether lens opacity influences the mean threshold of the visual field, 82 normal subjects were enrolled. All had their lens opacity measured with the Interzeag Lens Opacity Meter 701 and the visual field assessed with the Ring Resolution Perimeter. Lens opacity was highly correlated with age, while mean visual field threshold was also correlated with age but showed much greater variation. Multiple regression failed to show any influence of lens opacity measurements on the mean field threshold after age had been accounted for.

Adult↗

PubMed1999

Pattern of early visual field loss in HIV-infected patients.

OBJECTIVE: To determine the topographic pattern of visual field loss, if any, and its relationship to the stage of disease in human immunodeficiency virus-positive patients without infectious retinopathy. METHODS: A total of 151 eyes from 81 alert and cooperative patients with human immunodeficiency virus were evaluated with visual field testing. Results were analyzed relative to the associated underlying nerve fiber layer patterns associated with retinal ganglion cell axons as they traverse the retina to the optic nerve. The stage of visual field loss was analyzed relative to the length of survival using Kaplan-Meier survival analysis. RESULTS: No correlation of CD4 cell count with visual field mean defect (r2 = 0.23) or corrected pattern standard deviation (r2 = 0.00) was found. A pattern of visual field loss, consistent with sparing of the papillomacular bundles and associated with damage primarily to the inferior retina external to the posterior pole, was found. Survival analysis indicated a significant difference in time of survival between individuals with normal visual fields and those with a diffuse visual field loss, with a trend to less survival with increasing field loss severity. CONCLUSIONS: These results are consistent with disease at the level of the optic nerve. The relationship of stage of visual field loss to survival has important implications for early detection of field loss and appropriate therapeutic intervention to maintain function and quality of life.

Adult↗