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PubMed1987

Scanning the visual field without eye movements--a sex difference.

Subjects identified the location of a briefly exposed target pattern in the presence of five other patterns. Right-handed females, but not males, exhibited a significantly higher error rate in correctly localizing the target pattern when it was in the left visual field, particularly for the left parafoveal region. This unexpected distribution of errors as a function of target location can be accounted for by a sequential (serial) mechanism which scans the visual field. Since the exposure time was too brief for eye movements to have occurred, the results must reflect an internal scan of the neural representation of the information retained in the visual system following the brief stimulus presentation.

Adult↗

PubMed1989

Spectral sensitivity, absolute threshold, and visual field of two tick species, Hyalomma dromedarii and Amblyomma variegatum.

1. The spectral sensitivity in the wavelength range of 340-750 nm was determined by both a behavioral approach based on spontaneous positive phototaxis and the electroretinogram (ERG). 2. Concerning phototaxis the camel tick, Hyalomma dromedarii, showed two sensitivity maxima, one in the UV range (ca. 380 nm) and another in the blue-green range (ca. 500 nm). At higher intensities the relative sensitivity was more pronounced in the UV and at lower intensities more pronounced in the blue-green (reverse Purkinje shift). In the tropical bont tick, Amblyomma variegatum, there was a single sensitivity maximum in the blue range (ca. 480 nm). 3. In the ERG there was a maximum in the blue range (ca. 470 nm) in both species and a weak secondary maximum in the UV in Hyalomma. 4. The absolute sensitivity was very high. The threshold irradiance of phototaxis was as low as 5.2 x 10(6) photons.s-1.cm-2 in Hyalomma and 5.2 x 10(8) photons.s-1.cm-2 in Amblyomma. 5. When the eyes of Hyalomma were covered, the threshold irradiance was still very low, namely 5.2 x 10(8) photons.s-1.cm-2, indicating high absolute sensitivity of the extraretinal photoreceptors. 6. The visual field of the eyes was determined by ERG measurements. In both species the optical axis of each eye, i.e., the center of the visual field, was directed somewhat to the side and above the horizon. In Hyalomma this direction was 35 degrees to the long axis of the animal and 30 degrees above the horizon for natural body posture during walking. In Amblyomma the corresponding angles were 39 degrees and 33 degrees, respectively. The size of the field (at 50% sensitivity) in Hyalomma was relatively small, namely 14 degrees in the horizontal and 25 degrees in the vertical direction, compared with that of Amblyomma with 43 degrees and 49 degrees, respectively. 7. This is the first demonstration in ticks of spectral and absolute sensitivity by the behavioral approach and of the visual field by ERG. The results suggest that tick eyes possess features of both spider eyes and insect ocelli.

Animals↗

PubMed1980

Location of early glaucomatous visual field defects.

A study of 50 eyes with chronic open-angle glaucoma and early visual field defects showed superior defects to be twice as common as inferior defects. The superior defects tended to be closer to fixation than the inferior defects.

Glaucoma↗

PubMed1997

Visual-field measurements and driving eligibility.

BACKGROUND: A 50-year-old black man with an ocular history of open-angle glaucoma was seen for a vision rehabilitation examination, with goals of improving his vision for work and determining his eligibility for driving. He was referred to the clinic through state services for the visually impaired. METHODS: A low-vision evaluation was performed and baseline information was obtained, including distance- and near-visual acuities, visual fields, and subjective refraction. This information was used to determine if he was eligible for services and if any low-vision devices would benefit him. RESULTS: The patient demonstrated moderately decreased visual acuity in the right eye (6/15) and very reduced visual acuity in the left eye (6/120). His visual fields varied depending on the test performed, ranging from 85 degrees to 140 degrees horizontal diameter. He was able to remove his spectacles and perform near tasks quite well. CONCLUSIONS: The patient was counseled that if he used one of the field tests he could qualify for services, but if he chose the other test he would qualify for driving and not qualify for services. The ramifications of using different field tests and understanding their parameters when assessing eligibility for services and benefits can be significant.

Automobile Driving↗

PubMed1979

The nasal step in normal and glaucomatous visual fields.

We used an original method of kinetic and static analysis to examine the nasal visual field. When the nasal step is less than 4 degrees wide and its depth is less than 0.5 log units it may be merely a physiological sign of the anatomic and functional asymmetry of the retina. Sometimes it is an artifact. The nasal step can also be a glaucomatous defect. In this case it is often an early sign and it is wider than 4 degrees and its depth is greater than 0.5 log units. Because of its typical shape and invariable location it is easy to discover by kinetic perimetry and easy to check by static perimetry. If it is an early glaucomatous defect, it can be reversed. In practice the nasal step is an early and characteristic glaucomatous field defect like the isolated scotomas in the Bjerrum area, and it is easily detected and can be used as a sensitive marker in the follow up of glaucomatous damage.

Glaucoma↗

PubMed1998

A model for quantitative assessment of visual field changes in primary open-angle glaucoma with a computerized perimeter DICON TKS 4000.

PURPOSE: To evaluate the feasibility of using the grading algorithm utilized by the Advanced Glaucoma Intervention Study (AGIS) on a Humphrey Field Analyser with program 9 (76/30 degrees Threshold Grid) of a computerized perimeter DICON TKS 4000 and find whether the obtained score can be used to determine the stage of glaucoma. METHODS: Computerized perimetry was performed on 205 eyes with proven or suspected glaucoma. Visual field changes were assessed first subjectively, and then with the scoring method used in AGIS: the size, depth, and location of the visual field defects, and the nasal step were determined using a stencil and then the final score was calculated. RESULTS: Of 205 eyes examined 79 had perimetric changes. These were allocated subjectively into four groups corresponding to four stages of glaucoma: initial, evoluted, advanced and terminal. The mean scores for each group were calculated. There was a statistically significant correlation between the score and the stage of glaucoma. The mean scores for the first 3 stages differed significantly from each other. For stages 3 and 4 the difference was not statistically significant. CONCLUSION: The AGIS scoring method, developed originally for program 30-2 of the Humphrey Field Analyzer, can be applied with the 30 degrees Threshold Grid program of DICON TKS 4000 Perimeter for objective assessment of the glaucoma stage.

Feasibility Studies↗

PubMed1979

Sex and visual field effects on accuracy and decision making when subjects classify male and female faces.

Male and female subjects classified tachistoscopically presented slide photographs of faces as male or female. In Experiments I and II presentation was at random to the right or left visual hemifield. Two different signal detection procedures demonstrated that accuracy for both visual fields is equivalent in females and that males show a marked right-field advantage. A third experiment showed that this field advantage is preserved for males when presentation right or left is by blocks of trials suggesting that the left hemisphere is specialized for classification tasks. Results also showed that optimization in signal detection tasks may be lateralized for both males and females though males optimize more poorly than females in the left visual field. The data are taken to demonstrate equipotentiality of hemispheric functioning in females and stronger hemispheric lateralization in males.

Adolescent↗

PubMed1995

The statistical interpretation of blue-on-yellow visual field loss.

PURPOSE: To evaluate short-wavelength-sensitive perimetry in the detection of glaucomatous field loss. METHODS: The sample consisted of 27 normal subjects, 24 patients with primary open angle glaucoma (POAG), and 27 patients with ocular hypertension (OHT). Blue-on-yellow (B-Y) and standard (W-W) perimetry was undertaken with a modified Humphrey Field Analyzer 640 on one eye of each subject and patient. The B-Y data were corrected for individual ocular media absorption. Results were compared to an age-matched normal database of 50 subjects (age range, 60 to 82 years; mean age, 70.0 years; SD, 6.4 years). Visual field indices and total and pattern deviation probability maps were calculated for both W-W and B-Y fields. RESULTS: The B-Y normal database exhibited increased between-subject variability compared to the W-W normal database (P < 0.001). The greater variability increased with the increase in eccentricity (P < 0.001) and with the increase in age (P = 0.032). All patients with POAG exhibited B-Y field loss; 11 demonstrated greater B-Y loss than the corresponding W-W field. In advanced POAG, the B-Y and the W-W fields were similar. Twenty-five of the 27 normal subjects exhibited normal B-Y fields. Five of the 27 patients with OHT manifested B-Y focal abnormality and a normal W-W field: in two, W-W focal loss subsequently developed. CONCLUSIONS: Short-wavelength-sensitive perimetry can identify visual field loss before that detected by W-W perimetry. However, the increased between-subject variability necessitates stringent statistical analysis in the definition of abnormality.

Aged↗

PubMed1989

Effects of location and form cuing on the allocation of attention in the visual field.

Two experiments were conducted which tested the effect of two different types of cues on the allocation of attention in the visual field. Subjects responded to a target appearing either 6.5 degrees to the right or to the left of fixation in a field filled with small randomly positioned line segments. The target form was either a circle or diamond in which a horizontal or vertical line segment was positioned. Subjects made a speeded discrimination response on the basis of the orientation of this line segment. In the first experiment, there was always one target at each trial. In the second experiment, both circle and diamond were presented left or right of fixation simultaneously whereby the line segment only appeared in one of the forms. In different conditions, the most likely target location (left or right) and form (circle or diamond) were cued. Control conditions served as a baseline for determining costs and benefits. Reaction time measures showed that the validity of the location cue resulted in both costs and benefits, whereas the validity of the form cue had no such effects. The results cannot be reconciled with the claim of zoom lens theories that spatial attention can switch between different modes of operations. They are also at odds with theories that claim that attention has no spatial locus. The results are consistent with a simple spotlight theory in which spatial attention involves selecting a particular restricted area of the visual field for which the perceptual efficiency is enhanced.

Attention↗

PubMed1990

The effect of refractive blur on the visual field using the ring perimeter.

To determine the effect of optically induced blur on the visual field measured with high pass spatially filtered targets, 10 normal subjects had field examinations with 0 diopter + 1.00 diopter or + 2.00 diopter of overcorrection in the cyclopleged state. All subjects showed a significant loss of sensitivity when defocussed, but not with pupil dilation. Mean thresholds for the central field rose from 4.79 +/- 0.68 dB (Mean +/- SD) with the image focussed and pupil dilated, to 7.16 +/- 0.72 dB with two diopters of image blur (P less than 0.001). The effects of defocussing did not differ significantly between the central and peripheral parts of the field. The great influence of defocussing the image on sensitivity should be considered during clinical perimetry as the 2.37 dB decline shown would place the group's mean sensitivity below the fifth percentile for age corrected normals.

Adult↗

PubMed1988

Visual field influence on manual roll and pitch stabilization.

Human control performance in nulling perceived tilt angles was investigated for combinations of pseduo-random vestibular disturbances and different waveforms of low frequency wide visual field motions. For both roll and pitch axes, subjects tilted the trainer in which they were seated in the direction of field rotation. This visual bias was much stronger for pitch backwards with upward field rotation. Frequency response analysis showed the dominance of visual cues at low frequencies (below 0.06 Hz) and the reliance on vestibular information in the high frequency range for both axes. Models suggest that operator balancing responses at high frequencies are mainly processed by the semicircular canals rather than the otolith organs. The results also suggest that the subject tends to rely less on the otolith organs for pitch perception than for roll.

Adult↗

PubMed1987

Use of a modified binocular visual field to assess cyclodiplopia.

The patient who notes binocular diplopia may indicate that horizontal, vertical, or cyclorotary components are present. Although the single binocular visual field provides an indication of the area which is free of horizontal and vertical diplopia, it does not assess cyclorotary diplopia. A simple modification of the single binocular visual field which allows determination of the clinical significance of the cyclorotary component of diplopia is presented. Reproducible information is easily obtained, assisting in patient follow-up and management.

Adolescent↗

PubMed2003

Relationship between postural change of the intraocular pressure and visual field loss in primary open-angle glaucoma.

PURPOSE: To determine the relationship between the postural changes of the intraocular pressure and the visual field loss in patients with primary open-angle glaucoma. METHODS: Eleven normal subjects and 11 patients with primary open-angle glaucoma were studied. Intraocular pressure was measured in both the sitting and the supine positions. Visual fields were measured with automated perimetry. RESULTS: When patients moved from a sitting to supine position, the intraocular pressure increased by an average of 3.1 +/- 0.4 mm Hg (mean +/- SEM) in normal subjects and 4.0 +/- 0.2 mm Hg in patients with primary open-angle glaucoma. There was a significant difference between the normal subjects and patients with primary open-angle glaucoma (P = 0.049). Intraocular pressure increased by 4.4 +/- 0.3 mm Hg (P = 0.02) in the worse eye for mean deviation and 3.6 +/- 0.3 mm Hg (P = 0.38) in the better eye for mean deviation. There was no significant difference in intraocular pressure in the sitting position between both groups. CONCLUSIONS: The greatest difference in intraocular pressure between the sitting and supine positions was observed in the worse eye of patients with primary open-angle glaucoma. This result suggests that damage to the optic nerve in primary open-angle glaucoma might occur when patients are asleep in the supine position.

Case-Control Studies↗

PubMed1984

Comparison of manual Goldmann and automated static visual fields using the Dicon 2000 perimeter in the detection of chiasmal tumors.

We report that changes in the program (software) operating an automated perimeter (hardware) remarkably improved its ability to produce interpretable diagnostic information. A group of 11 postoperative patients with pituitary adenomas and other chiasmal tumors having stable visual field defects demonstrated by manual kinetic and suprathreshold Goldmann perimetry were re-examined with automated suprathreshold static perimetry performed by the Dicon model 2000 perimeter. During the study a program for two-zone (central and peripheral), three-level suprathreshold static perimetry became available. With optimum test administration and interpretation, the Dicon 2000 perimeter with the two-zone, three-level suprathreshold program can at least equal the performance of an experienced perimetrist using manual Goldmann kinetic and selective static perimetry in the detection of visual field defects resulting from chiasmal tumors. The two-zone, three-level suprathreshold suprathreshold program was superior to a single zone, one-level programs in examining this population.

Adenoma↗

PubMed1986

Optokinetic nystagmus in patients with defects of the central visual field.

Optokinetic nystagmus (OKN) was studied in patients with central visual field defects. Apart from a classic OKN, an inverted nystagmus was observed in some cases. A prerequisite for eliciting this paradoxic OKN was that the attention of the subject was directed to the field defect. Although other factors seem to be co-determining, a central mechanism is thought to process the visual information according to spatial-selective attention.

Adult↗

PubMed1975

Visual fields and electroretinography following extensive photocoagulation.

Twenty-four patients with proliferative or preproliferative diabetic retinopathy underwent extensive argon laser photocoagulation in one eye. Detailed central and peripheral visual-field examinations and electroretinography were performed before treatment, and at intervals after treatment. Visual field changes were as follows: (1) eight patients had only mild to moderate constriction of all isopters, (2) 11 had discrete scotomata in addition, (3) two had prominent nerve-fiber-bundle defects, (4) three had severe constriction of all isopters, save (in two) that to the largest peripheral test object. Electroretinographic b-wave amplitudes were reduced an average of 40% to white test flashes. Blue test flashes showed an even larger reduction of the rod response. This suggests the receptors in approximately 40% of the retinal area are destroyed by such extensive photocoagulation, covering predominantly that part of the retina that has the highest concentration of rods.

Adult↗

PubMed1997

Which method of flicker perimetry is most effective for detection of glaucomatous visual field loss?

PURPOSE: The authors compared the efficacy of two different forms of flicker perimetry: temporal modulation perimetry (TMP), which measures contrast thresholds for a fixed temporal frequency, and critical flicker frequency (CFF), which measures the highest frequency for which flicker is detected at a fixed contrast. METHODS: The authors compared 16 patients with early to moderate glaucomatous visual field loss with 16 age-matched normal controls. Flicker stimuli consisted of 2 degrees diameter targets of 2 seconds in duration, presented in 44 locations throughout the central 30 degrees visual field. Flicker was presented within a cosine envelope to avoid temporal transients. For TMP, contrast sensitivity thresholds were measured for 8-Hz sinusoidal flicker; CFF thresholds were measured for a stimulus of 100% contrast. RESULTS: The results indicate that TMP and CFF produced similar test-retest reliability in normals. CFF had slightly better reliability in glaucoma patients. Receiver operating characteristic analysis revealed that TMP could provide better separation of normals and glaucoma patients than did CFF. Similar findings were obtained when the thresholds for both procedures were converted to Z scores. CONCLUSIONS: Both methods of flicker perimetry testing provide acceptable test-retest reliability, and both can distinguish normal subjects from glaucoma patients. However, TMP is more effective in separating normal subjects from glaucoma patients than CFF, suggesting that TMP is the method of choice for detecting glaucomatous damage using flicker perimetry.

Aged↗

PubMed1993

Comparison of the oculokinetic perimetry glaucoma screener with two types of visual field analyser.

We compared the accuracy and testing time of a new 26-point central visual field glaucoma screening device, the oculokinetic perimetry (OKP) screener, with the results obtained with the Friedmann field analyser standard program (phase 1) and the Humphrey field analyser 40-point screening program (phase 2). Seventy-three eyes of 73 subjects were tested in phase 1, and 142 eyes of 75 subjects in phase 2. The study population comprised patients with eyes that were ocularly normal and patients with eyes showing early cataract, posterior vitreous detachment, established chronic open-angle glaucoma or ocular hypertension. The OKP glaucoma screener demonstrated a sector concordance rate of 95% in phase 1 and 93% in phase 2. The OKP screener was three to four times more rapid in execution than the standard device. We feel that the OKP glaucoma screener is ideally suited for use by physicians in a family practice setting.

Adolescent↗