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PubMed2002

[Correlation between changes in the nerve fiber layer and examination of the visual field using automatic perimetry in diagnosing primary open angle glaucoma].

PURPOSE: To analyse the correlation between changes in the nerve fiber layer and the appearance of defects in the visual field in primary open angle glaucoma (POAG). MATERIAL: and methods: Digital image processing of the nerve fiber layer and examination of the visual field (30-2 Humphrey) was performed in 450 patients. The conditions for obtaining the digital images are presented. RESULTS: Defects of the nerve fiber layer were evaluated qualitatively and quantitatively using automatic perimetry and the correlation was estimated. The results are discussed. CONCLUSION: Examination of patients suspected of having POAG is much more precise when using both techniques performed the same day. Thus it will be possible to save time for: early diagnosis, monitoring the treatment, limiting the progression of glaucoma.

Adult↗
PubMed1992

Retention of central visual field in retinitis pigmentosa.

According to Kanski, roughly one in four patients with retinitis pigmentosa retains visual acuity adequate for reading, although the electroretinogram may be extinguished and the visual field constricted to 2 to 3 degrees (whether diameter or radius is not stated). Under the age of 20 years, an acuity as poor as 6/60 is relatively uncommon, whereas over the age of 50 years such an acuity becomes common. Heckenlively comments that by the end of the 4th decade of life, most males with X-linked retinitis pigmentosa have vision reduced to hand motion or light perception. Women tend to be less severely affected than men: in a study by Bird, only 3 of 48 female heterozygotes had an acuity of less than 6/9, whereas only 8 of 28 hemizygous males had an acuity of 6/9 or better. I thought it would be instructive to analyze the visual field data for a female patient who, although she had suffered considerable loss of peripheral vision, is continuing to function visually quite well.

Adult↗
PubMed1992

[Documentation of glaucomatous visual field defects in threshold and suprathreshold perimetry].

In contrast to normal subjects, the individual stimulus threshold for differential light sensitivity (DLS) in glaucoma patients fluctuates considerably. The sensitivity and the size of the defect are correlated: with a higher individual stimulus threshold, i.e. when sensitivity deteriorates, the number of defects decreases. Conversely, when the individual stimulus threshold drops, i.e. when sensitivity improves, the number of defects recorded increases. The trend is the same with extensive Grade 3 defects. This correlation between sensitivity and defect size means that the number and depth of individual defects change constantly, due to the fluctuation of the individual stimulus threshold. In follow-up examinations test positions with permanent defects (a defects) can be distinguished from those where defects have been detected several times, but not permanently (b defects) and, respectively, only once in 2 1/2 years (c defects). Defects must therefore be classified not only according to depth, but also according to behaviour at individual test positions. Such a classification can be accomplished by tabulating all newly numbered test positions and the defects identified there. After 5 visual field examinations the defects are then classified as a, b, or c defects. They are then identified by colour symbols and transferred to a test position chart representing a synopsis of 5 visual fields. The chart not only permits exact topographical analysis but also furnishes information on certain structural features of the glaucomatous visual field: stable nuclear areas of a defects surrounded by fluctuating peripheral defects (b defects) or concomitant c defects. After a further 1 1/2-2 years, 5 more follow-ups are summarized, classified and transferred to a follow-up test position chart. Comparison of these two test position charts furnishes information of major prognostic value.

Aged↗
PubMed2001

Comparison of visual field defects between primary open-angle glaucoma and chronic primary angle-closure glaucoma in the early or moderate stage of the disease.

The visual field data (Humphrey C24-2) of early to moderate stage glaucoma between primary open-angle glaucoma (POAG) and chronic primary angle-closure glaucoma (PACG) patients was compared. Eleven POAG (11 eyes) and 14 chronic PACG patients (14 eyes) were matched with respect to age, sex, and disease severity. Although the mean deviation, pattern standard deviation, and short-term fluctuation were similar between the two groups, the mean corrected pattern standard deviation was higher in the POAG patients (p=0.048). When the numeric pattern deviation data (STATPAC II) was used for point-wise between-group comparisons, more depressed paracentral points were found in POAG patients. Different patterns were identified in visual field damages between the chronic PACG and POAG patients. The chronic PACG patients showed more generalized field loss than the POAG patients.

Aged↗
PubMed1986

Similarities between the visual fields of ocular hypertensive and normal eyes.

We tested 136 well-documented ocular hypertensive eyes with no visual field abnormalities on detailed manual perimetry using the C-30-2 program of the Humphrey Visual Field Analyzer. The results were compared with those of 274 age-matched normal eyes. No significant differences in threshold sensitivity were found between ocular hypertensive and normal eyes at any of the 76 points tested in the central 30 degrees. In the ocular hypertensive eyes, the presence of nerve fiber layer defects, especially diffuse atrophy, was associated with depressed threshold values. Threshold values were not associated with the size of the cup-disc ratio, level of intraocular pressure, or time since diagnosis of ocular hypertension.

Humans↗
PubMed2001

Fighting from the right side of the brain: left visual field preference during aggression in free-ranging male tree lizards (Urosaurus ornatus).

In a field study on male tree lizards (Urosaurus ornatus), we tested the hypothesis that aggression is lateralized, and predicted that resident males should preferentially use the left-visual field (LVF)/right hemisphere in aggressive interactions with other males. This prediction was based on results for a small but taxonomically diverse number of vertebrates indicating a left-eye preference/ right hemisphere specialization for aggression. Many lizards use postural displays to signal aggression and lateral eye placement prevents binocular vision of such displays. The fullshow is an aggressive display that is typically performed with the body held perpendicular to that of the opponent. We staged male-male encounters by introducing stimulus males to free-ranging males (hereafter called focal males), and then recorded both the focal male's behavior and the visual field that he used to view the intruder while performing fullshow displays. When intruders were introduced in the right visual field (RVF), focal males were equally likely to use either the LVF or RVF to perform their first fullshow. However, in these RVF introductions focal males were more likely to turn and use the LVF if the intruder was smaller. In contrast to RVF introductions, in LVF introductions focal males were significantly more likely than expected by chance to continue to use the LVF to view the intruder when performing the first fullshow. Furthermore, if focal males performed their first fullshow with the intruder in their LVF, they subsequently gave more aggressive displays than focal males that performed their first display with the intruder in their RVF. Additionally, charge (a highly aggressive behavior that usually leads to direct physical contact and a bite) was significantly more likely to occur while the LVF was being used to view the opponent. These results are consistent with the hypothesis that aggression is lateralized to the right hemisphere. This study is one of only a few examples of laterality of brain function demonstrated in a free-ranging vertebrate.

Aggression↗
PubMed1979

An analysis of visual acuity, visual fields, and disk cupping in childhood glaucoma.

We analyzed the long-term functional results in 102 eyes of 59 patients with childhood glaucoma with specific reference to the pattern of optic nerve damage. Optic disk photography and quantitative perimetry were used to judge the degree of damage that had been sustained. There was a predilection for initial visual field damage in the arcuate area, followed by further arcuate and nasal field loss, similar to the pattern of visual field loss seen in adult glaucoma. In children, as in adults, neural tissue appeared to be lost preferentially at the vertical disk poles. The selective pattern of glaucomatous optic nerve damage seemed not to depend upon the age of the optic nerve structures. In contrast to adult eyes, the scleral canal in children apparently enlarges with high IOP. Thus, disk cup size increase in children could occur from neural tissue loss, from scleral canal enlargement, or from a combination of the two processes.

Adolescent↗
PubMed2002

Left-right and upper-lower visual field asymmetries for face matching, letter naming, and lexical decision.

The relation between left-right and upper-lower visual field (VF) asymmetries was examined for face matching, letter naming, and lexical decision. Stimuli were flashed in the VF quadrants. Face matching resulted in a lower left and upper right VF advantage. Letter-naming resulted in a distinct upper-right VF advantage. For lexical decision, no upper/lower asymmetries were found. Words were processed faster in the right than in the left VF, while nonwords were processed equally fast in both VFs. The results are discussed in terms of hypothesized structural connections of the lower versus upper visual field to dorsal versus ventral visual pathways and in terms of attentional mechanisms related to the processing of visual information in the VF quadrants.

Adult↗
PubMed1990

Computer-assisted evaluation of visual fields.

A computer program is described which provides statements in normal prose about the outcome of automated visual field examinations as well as hints concerning possible alternative interpretations and artifacts, if present. The program is intended as an aid to ophthalmologists being trained to evaluate critically visual fields. The limits of the applicability of this program are discussed.

Data Interpretation, Statistical↗
PubMedDate not supplied

[Visual field changes secondary to vigabatrin treatment].

INTRODUCTION: Vigabatrin is an effective antiepileptic drug for treatment of partial crises with or without generalization. It acts by increasing GABA levels by irreversible inhibition of the enzyme GABA-transaminase. In recent years there have been several reports published on the appearance of alterations of the visual fields of patients treated with this drug. OBJECTIVE: To study the prevalence and characteristics of the visual field changes associated with vigabatrin treatment in an adult epilepsy clinic. PATIENTS AND METHODS: Ophthalmological examination, consisting of questions about eye symptoms, study of the fundus oculi, Humphrey-type campimetry, protocol 30-2, visual evoked potentials and electroretinogram were done on a group of 10 patients on long-term vigabatrin treatment. RESULTS: Six of the ten patients (60%) had campimetric alterations, which were serious in two cases (20%). Only the two patients with severe field defects complained of sight changes when questioned and their complaints were mainly of repeatedly bumping into things. In two patients (20%) there was pallor of the optic nerve. In both cases, the patients with severe field defects showed alterations on the electroretinogram. Visual evoked potentials were normal in all cases. CONCLUSIONS: There is a very high prevalence of visual field defects in patients on long-term treatment with vigabatrin. Clinical ophthalmological signs are not usually seen until advanced stages. Pallor of the optic nerve was seen in a group of patients. It is very important that serial campimetric studies are done for early detection of such alterations.

4-Aminobutyrate Transaminase↗
PubMedDate not supplied

Sensitivity to full-field visual movement compatible with head rotation: variations with eye-in-head position.

Variations in velocity detection thresholds for full-field visual rotation about various axes are compatible with a simple channel-based system for coding the axis and velocity of the rotation (Harris & Lott, 1995). The present paper looks at the frame of reference for this system. The head-centered, craniotopic reference system and the retinal-based, retinotopic reference systems were separated by using eccentric eye positions. We measured the threshold for detecting full-field visual rotation about a selection of axes in the sagittal plane with the eyes held either 22 1/2 degs up, straight ahead or 22 1/2 degs down in the head. The characteristic features of the variation in detection thresholds did not stay stable in craniotopic coordinates but moved with the eyes and were constant in retinotopic coordinates. This suggests that the coding of head rotation by the visual system is in retinotopic coordinates.

Adult↗
PubMed1985

Critical flicker fusion and double flash discrimination in different parts of the visual field.

The temporal sensitivity of the visual system was investigated in fifteen healthy subjects by determining the critical flicker fusion frequency (CFF) and the performance in a double flash discrimination (DFD) task. Measurements were obtained using a small test light of 2.5 degrees diameter in the fovea and at eight different perifoveal retinal locations along the horizontal and vertical meridians. Statistically significant differences were found for both the CFF and the DFD task showing a higher temporal sensitivity of the nasal and upper than the temporal and lower retinal areas. The functional significance of the findings is discussed and related to electrophysiological and behavioral data which describe a functional superiority of the upper over the lower hemiretinal system.

Adult↗
PubMed1992

Association of reliability with reproducibility of the glaucomatous visual field.

We studied 207 glaucoma patients (207 eyes) who had two successive visual tests on the Humphrey Field Analyzer to determine the association of unreliability (> 10% incidence of a missed catch trial test) with threshold variation. We found that in patients where one visual field showed > 30% false negative or positive errors, and the other visual field also was unreliable, a significant increase in the variance of the mean defect existed from reliable patients (p < 0.05). Of patients who had only one of two visual fields which was unreliable (from false negative errors), only those with marked glaucomatous visual field loss (< -15 dB depth of defect) showed a greater variance in mean defect between examinations over reliable patients (p < 0.05). In total, 41 patients (19.8%) had unreliable visual fields associated with statistically increased threshold variation. This study suggests that patient reliability should be considered when interpreting changes in threshold between automated visual field examinations.

Aged↗
PubMed1989

Binocular depth perception, visual acuity and visual fields in cats following neonatal section of the optic chiasm.

We studied the role of the transcallosal pathway in stereopsis by measuring binocular and monocular depth perception in two cats that had undergone section of the optic chiasm at the age of 21 d. To ensure that the surgery did not impair vision to the extent that depth perception could not be evaluated, visual acuity and visual fields were also measured. In both of the chiasm-sectioned animals the visual fields were reduced and the visual acuity was substantially lower than in normal cats, with a maximum of about 2 cyc deg-1. Binocular depth thresholds of the chiasm-sectioned cats were worse than those of the normal cat but were better than their own monocular thresholds. These results suggest that the chiasm-sectioned animals were still able to use binocular cues to judge depth and indicate that the indirect pathway through the corpus callosum is sufficient to mediate binocular depth perception.

Depth Perception↗
PubMed1991

Effects on driving performance of visual field defects: a driving simulator study.

To elucidate the possible traffic safety risks induced by visual field defects, a method was developed based on a driving simulator. The capacity to detect stimuli of different sizes appearing in 24 different positions on the screen in front of the driver was measured. Two groups of normal subjects and a number of subjects with different visual field defects were studied. In the groups of normals, the median reaction times were fairly homogenous. There was a slight difference between central and peripheral stimuli, which was somewhat larger for the older subjects. Among the subjects with field defects, the individual variations were very dominant. Very few of these showed a capacity to compensate for their deficiency. In order to gain insight into possible compensatory mechanisms of these persons, eye movement recordings were made. The results indicate that the visual search pattern may be of importance in this respect. Some comparisons with respect to detection capacity were also made with one-eyed subjects and with optically generated field restrictions (spectacles and spectacle frames).

Adult↗
PubMedDate not supplied

Image quality and visual performance in the peripheral visual field following photorefractive keratectomy.

PURPOSE: A theoretical and experimental study was performed to assess the possible effects of photorefractive keratectomy (PRK) on retinal image quality and thresholds in the peripheral visual field. METHODS: Simple optical calculations suggest that although the quality of the retinal image at the fovea of the postoperative PRK eye may be comparable to that in an emmetropic eye, images in the peripheral field may be markedly worse, since peripheral ray bundles may pass partly through ablated and partly through unablated cornea, giving a simultaneous-vision bifocal effect. This would be expected to create an annular zone of confusion, so that light from two different directions in object space arrives at the same point on the retina. The position of this zone and its width are a function of the ablation zone geometry, the attempted correction, and the pupil diameter, but the major effects typically occur at field angles between about 40 degrees and 60 degrees. To explore this effect, Goldmann static quantitative perimetry was carried out along the 0 degree to 180 degrees meridian in six patients who had undergone myopic PRK and eight emmetropes. RESULTS: The results showed that thresholds for the PRK group at field angles from 40 degrees to 60 degrees were significantly higher than those of the emmetropic group (P < .01). These findings arise because the retinal images in the peripheral field of originally myopic, postoperative PRK patients are, in general, significantly degraded in comparison with those of emmetropes. CONCLUSION: Although under photopic conditions, retinal image quality close to the visual axis in patients who have been corrected by PRK is similar to that in emmetropes, it may be markedly worse in the peripheral visual field.

Adult↗
PubMed2003

Visual field anisotropy revealed by perceptual filling-in.

Four experiments were performed to investigate how the time required for perceptual filling-in varies with the position of the target in the visual field. Conventional studies have revealed that filling-in is facilitated by a target with greater eccentricity, while no systematic studies have examined the effect of polar angle. Experiment 1 examined the effect of polar angle when the target and surround differed in luminance. Filling-in was facilitated as the target position changed from the horizontal to the vertical meridian. This dependency was more prominent in the upper field than in the lower, although no asymmetry was found between the left and right visual fields. These features were observed in both monocular and binocular viewing. These results were replicated in a modified stimulus configuration, in which the surround was a circular region concentric with the target (Experiment 2). Moreover, it was confirmed that the asymmetry was not due to fluctuation in the retinal image (i.e., eye movement) (Experiment 3). Finally, Experiment 4 examined whether this anisotropy was observed when two differently oriented gratings were presented in the target and surround regions. Again, filling-in was facilitated for a target close to the vertical meridian, irrespective of the relationship between the target and surround orientations. The underlying mechanism of this anisotropy is discussed from the viewpoints of cortical magnification and neural connections in the visual cortex.

Analysis of Variance↗
PubMed2002

Optical coherence tomography measurement of nerve fiber layer thickness and the likelihood of a visual field defect.

PURPOSE: To determine if optical coherence tomography (OCT) measurements of nerve fiber layer (NFL) thickness can be used to predict the presence of visual field defects (VFD) associated with glaucoma. DESIGN: Quota-sampled, cross-sectional study. METHODS: Retrospective study of OCT NFL thickness measurements in 276 eyes of 276 subjects. All persons received OCT NFL thickness analysis; 136 eyes underwent frequency-doubling technology (FDT) perimetry; and 140 eyes underwent Swedish interactive threshold algorithm (SITA) perimetry. We defined a parameter called NFL(50), which is the NFL thickness value at which there was a 50% likelihood of a VFD with either SITA or FDT perimetry. We evaluated the use of NFL(50). RESULTS: The mean NFL thickness with (n = 68) and without (n = 68) a VFD in the FDT group was 93.2 microm +/- 22.6 and 108.4 microm +/- 14.1, respectively. The mean NFL thickness with (n = 70) and without (n = 70) a VFD in the SITA group was 78.9 microm +/- 24.8 and 103.0 microm +/- 18.0, respectively. The FDT mean NFL(50) value was 98.5 microm. The SITA mean NFL(50) value was 87.0 microm. The area under the receiver operator characteristic (AROC) curve for mean NFL was 0.73, and the positive predictive value (PPV) for FDT mean NFL(50) was 72.2%. For SITA mean NFL, the AROC was 0.79 and the PPV for NFL(50) was 77.2%. CONCLUSION: Nerve fiber layer thickness analysis using OCT may be clinically useful in identifying subjects who have visual field loss. However, the PPV suggests that OCT may need higher resolution and better reproducibility to enhance its sensitivity and specificity for population screening.

Adult↗