Degrees Of Visual Field Research Articles

Relation between relative afferent pupillary defect and suprathreshold automated perimetry

The purpose of this study was to test for correlation between relative afferent pupillary defect (RAPD) and visual acuity, central differential light threshold and visual field defect measured by suprasthreshold automated grid perimetry. In 98 patients with optic neuropathies of different origin (inflammatory, ischemic, or compressive) in addition to a standard ophthalmological examination, static perimetry of the 30 degrees visual field with a dense grid of test spots, including measurement of the central differential light sensitivity, was done by means of the Tübingen Automated Perimeter. RAPD was tested using the swinging flashlight test quantified with neutral density filters. Visual acuity and central differential light sensitivity correlated only weakly with the RAPD. The visual field showed a better correlation (coeff. of corr. for all patients 0.58, for patients with optic neuritis 0.64. for patients with AION 0.53 and for patients with compressive neuropathies 0.84). One test spot not seen in perimetry corresponded to an RAPD of about 0.01 log-units. The results confirm those from previous studies obtained by threshold perimetry. The RAPD is a good parameter for the severity of an optic nerve lesion, especially of compressive origin.

Diagnostic value of short-wavelength automated perimetry.

Short-wavelength automated perimetry (SWAP) uses a bright yellow background and a large blue stimulus to isolate and measure the sensitivity of short-wavelength-sensitive mechanisms throughout the central 30 degrees visual field. After more than 8 years of cross-sectional and longitudinal studies of patients with early glaucoma, ocular hypertensive patients, and age-matched control subjects, SWAP has been shown to be a sensitive indicator of early damage and progression of loss in glaucoma. It is now available as an optional visual test procedure for routine clinical use on the most widely distributed automated perimeter. Recent investigations have been directed toward refinement and standardization of the technique, as well as toward the influence of other clinical factors (ocular media opacities, macular pigment, statistical interpretation, and related issues) on SWAP. This paper provides a brief overview of current research on SWAP as a clinical diagnostic test procedure.

Aging Effects for Opponent Mechanisms in the Central Visual Field

Visual field sensitivity measures were obtained for normal observers between the ages of 20 and 83 years, using test conditions in which detection has been shown to be mediated by opponent (chromatic) mechanisms (Size V target, 620 nm stimulus, 31.5 asb [10 cd/m2] white background). Average visual field sensitivity for opponent mechanisms decreased by approximately 0.6 dB per decade. This age-related sensitivity loss was smallest for the central 10 degrees visual field (0.5 dB per decade) and increased as a function of stimulus eccentricity (0.66 dB per decade for 20 to 30 degrees eccentricity), although the differences in aging effects for various eccentricities were not statistically significant. There were negligible differences in age-related sensitivity losses for opponent mechanisms in various quadrants of the visual field. These findings are generally similar to those obtained for standard automated perimetry, which uses a small white target on a white background. By comparison, short wave-length-sensitive mechanisms exhibit age-related losses that are more than twice as large, even after lenticular transmission losses are taken into account. These data provide a basis for distinguishing early disease-related losses from those related to normal aging.

Short-Wavelength Automated Perimetry in Low-, Medium-, and High-Risk Ocular Hypertensive Eyes

To examine the relationship between the prevalence of short-wavelength sensitivity losses in the central 30 degrees visual field and risk factors for development of glaucomatous visual field loss in ocular hypertension. A modified Humphrey Field Analyzer was used to perform standard automated perimetry and short-wavelength automated perimetry (SWAP), which is a technique that isolates the activity of short-wavelength-sensitive ("blue") mechanisms. In addition, an assessment of the risk of developing glaucomatous visual field loss was determined, based on a validated model that utilized intraocular pressure, a family history of glaucoma, age, and the vertical cup-to-disc ratio. Both eyes of 232 ocular hypertensive patients were examined and compared with results from an age-matched control group of normal subjects. Both ocular hypertensive patients and normal subjects had to have normal visual fields on standard automated perimetry, good visual acuity, and no evidence of other ocular or neurologic disease or surgery. Intraocular pressure in the ocular hypertensive patients was 21 mm Hg or greater OU (without medication), and it was less than 20 mm Hg OU in normal control subjects. Less than 10% of the low-risk ocular hypertensive eyes had a SWAP deficit, as compared with 20% of the moderate-risk and 33% of the high-risk ocular hypertensive eyes. Intraocular pressure and a family history of glaucoma showed no meaningful relationship with the prevalence of SWAP deficits, but both age and the vertical cup-to-disc ratio demonstrated a strong association with the SWAP abnormalities. The SWAP results that were found in the ocular hypertensive eyes were associated with other risk factors that have been reported to be predictive of the development of glaucomatous visual field loss, especially the vertical cup-to-disc ratio and age. These findings support the notion that the SWAP deficits represent early glaucomatous damage and may be related to early changes that occur at the optic nerve head.

Quantitative analysis of changes of automated perimetric thresholds after pupillary dilation and induced myopia in normal subjects.

We quantitatively analyzed the changes of the (retinal) threshold sensitivities between normal status and dilated emmetropic status, and between dilated emmetropic status and -1.0D induced myopic status. Three consecutive visual field examinations by Humphrey Field Analyzer C-30-2 threshold test and STATPAC program were performed in 36 eyes of 21 normal subjects who ranged in age from 23 to 40 years. The results were as follows: 1) There was a statistically significant decrease (0.87 +/- 0.91dB)in the mean threshold sensitivity within the central 30 degrees at the dilated emmetropic status (27.90dB) as compared with the normal status (28.77dB)(p = 0.0001). 2) There was a statistically significant decrease(0.99 +/- 0.61dB) at -1.0D induced myopic status(26.91dB) as compared with the dilated emmetropic status(27.90dB)(p = 0.0001). 3) After dilation, the mean threshold sensitivity between 20 and 30 degrees of field showed statistically significant decrease as compared with those within the central 20 degrees of visual field(p < 0.05). In case of -1.0D induced myopia, there were uniform decreases in the mean threshold sensitivities within the central 30 degrees of visual field (p > 0.05). Therefore, we emphasize the importance of consistent pupillary size and correct refractive state in performing the serial automated visual field tests.

Arthroscopic visual field mapping at the periphery of the medical meniscus: A comparison of different portal approaches

The posteromedial compartment, particularly the posterior horn of the medial meniscus, has been shown by many investigators to be a common source of diagnostic errors in knee arthroscopy when access is limited to anterior portals. To better understand the anatomical basis of this apparent technical limitation, we quantified the visible versus the "blind" zones of the posteromedial meniscal periphery present when using the following arthroscopic approaches in six fresh knee specimens: (a) direct anteromedial frontal view with a 30 degrees arthroscope (AM-30 degrees); (b) anterolateral portal, 30 degrees arthroscope, transnotch view (AL-30 degrees); (c) anterolateral portal, 70 degrees arthroscope, transnotch view (AL-70 degrees); (d) central portal, 70 degrees arthroscope, transnotch view (C-70 degrees); and (e) posteromedial portal, 30 degrees arthroscope, direct rear view (PM-30 degrees). The AM-30 degrees approach visualized only the anterior 50% or less of the total superior meniscosynovial junction length, in all knees. The AL-30 degrees, C-70 degrees, AL-70 degrees, and PM-30 degrees portal approaches visualized the posteriormost 16.4%, 24.2%, 31.6%, and 54.9% of the upper meniscal rim, respectively. In conjunction with the AM-30 degrees visual field, the PM-30 degrees approach provided the most complete overall visualization of the superior meniscosynovial junction, leaving a mean blind zone of only 8.4% (12 mm) between the anterior and posterior visual fields. The AL-30 degrees, C-70 degrees, and AL-70 degrees approaches left significantly greater portions (means of 47%, 39.1%, and 31.7%, respectively) of the meniscal rim universalized.

Nerve Fiber Layer Defects with Normal Visual Fields: Do Normal Optic Disc and Normal Visual Field Indicate Absence of Glaucomatous Abnormality?

When the optic disc has normal appearance with no abnormalities in routine automated perimetry, the subject is not considered to have glaucoma. The purpose of this study is to show how such patients may have localized retinal nerve fiber layer defects with corresponding functional abnormality. The authors selected eight eyes of eight patients who had a localized retinal nerve fiber layer defect extending within a few degrees from fovea but in whom the optic disc appearance and Humphrey 30-2 visual fields were normal. Of the eight patients, three had positive family history of glaucoma, two had suspected retinal nerve fiber layer abnormality in routine eye examination, two had increased intraocular pressure (IOP), and one had advanced low-tension glaucoma in one eye with a normal fellow eye. The authors examined the central 10 degrees visual field with 1 degree resolution using Humphrey perimeter and the Ring and Centring programs of the high-pass resolution perimeter. A central field defect corresponding to retinal nerve fiber layer defect was found in six of eight patients: in both 10 degrees Humphrey field and Centring programs (2 eyes), in Humphrey only (2 eyes), and in Centring only (2 eyes). The results indicate that retinal nerve fiber layer photographs are helpful in diagnosing glaucoma because early glaucomatous abnormalities cannot be excluded without nerve fiber layer photography. Currently available routine perimetric examination programs do not always detect very early functional damage.

Sectorization of the Central 30° Visual Field in Glaucoma

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. 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. 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. The sector pattern and sector values obtained were considered useful in studying the visual field data of glaucoma.

Increased sensitivity with decreased numbers of test points and decreased test field size in automated perimetry of normal subjects.

Mean sensitivity (MS) was compared among programs with different numbers of test points and different test field sizes with an automated perimeter in normal subjects. The programs tested were designed by the program Sargon. Within a 10-degree visual field the MS was significantly higher with fewer test points and with a smaller test field size. The MS between 10 and 25-degree fields increased under the same conditions. Increased MS was found with decreased numbers of test points and decreased test field size within 25 degrees in automated perimetry of normal subjects.

Influence of Amblyopia on High-Pass Resolution Perimetry

Seventeen subjects with amblyopia due to strabismus and anisometropia were examined using high-pass resolution perimetry. In addition to the standard technique, testing the 5-30 degrees visual field, an optional program testing the central 4 degrees visual field was used. Threshold elevation was confined to the central 4 degrees visual field and strongly correlated with visual acuity, expressed as minimum angle of resolution. Standard high-pass resolution perimetry did not reveal any significant abnormalities in the amblyopic subjects. In conclusion, the technique is useful for the diagnosis of ocular or neurologic disorders also in subjects with a high degree of amblyopia.

The visual field in chronic simple glaucoma and ocular hypertension; its character, progress, relationship to the level of intraocular pressure and response to treatment.

Nine hundred and twenty-nine patients with chronic simple glaucoma or ocular hypertension were followed for one to thirteen years using the King's College Hospital glaucoma data base. The 30 degree visual field was divided into twelve clinical zones. The field sensitivity and its change as measured by the mean differential threshold both in these zones and overall was followed to determine the pattern and progress of field loss in eyes diagnosed initially as chronic simple glaucoma or ocular hypertension. The findings were related to other similar analyses in which the mean differential threshold in chronic glaucoma was found to correlate significantly with the initial intraocular pressure and its progress with the mean follow-up intraocular pressure under treatment. Inferences were drawn regarding the nature of chronic simple glaucoma and ocular hypertension and their management.

A differential diagnostic test for optic neuritis

A temporary lowering of body temperature by means of cold drinks, tried on a group of 18 patients with acute optic neuritis, led in 14 cases to a significant improvement in the 30 degree visual field, which the authors tested with the Octopus 201 automatic perimeter. In a group of 11 patients (17 eyes) who had previously had optic neuritis an improvement in the visual field was only seen in 8 eyes; in the other 9 eyes there was a deterioration. A slight deterioration in the 30 degree visual field after lowering body temperature was demonstrated in a group of 7 patients (12 eyes) with various diseases of the optic nerve as well as in 5 other healthy subjects. The temporary improvement in the patients with acute optic neuritis was probably caused by a reversible increase in the conductivity of the demyelinated nerve fibers as a result of lowering body temperature.

Topography of the afferent connectivity of area 17 in the macaque monkey: a double-labelling study.

The various structures afferent to area 17 (or V1) of the macaque monkey have widely differing retinotopic organizations. It is likely that these differences are reflected in the topographic organizations of the projections from these structures to area V1. We have investigated this issue by placing side-by-side injections of two retrograde fluorescent tracers, fast blue and diamidino yellow, in V1. By examining the extent of mixing of the two populations of singly labelled cells and the presence of doubly labelled cells, in different structures, we have characterized the topography of each projection in terms of the size of its axonal arborization and the amount of convergence and divergence. The afferents from the lateral geniculate nucleus (LGN) and from the pulvinar are organized in a point-to-point fashion. The maximum extent of axonal arborization of these afferents is 0.5 mm and these projections demonstrate little scatter (i.e., neighboring LGN neurons project to adjacent regions of V1). The other two subcortical structures examined, the claustrum and the intralaminar nuclei, demonstrate a much larger scatter and wider axonal arborizations in their projections to V1 than do the LGN and pulvinar. Two-dimensional reconstructions were made of the distribution of labelled neurons in extrastriate cortical areas. Using the separation between patches of labelled cells and transitions in myelin-stained sections, we have identified seven separate cortical regions containing labelled cells. Two of these can be identified as area V2 and the middle temporal visual area (MT). Three other regions correspond to areas V3, V3A and V4t. Finally, two more regions of labelling have been distinguished that belong to area V4. These results demonstrate that, at least within the central 6 degrees of visual field, all the presently known extrastriate visual cortical areas project to V1. This result is interesting in view of the fact that only a few extrastriate cortical areas are reported to receive afferents from V1. Three groups of cortical areas can be distinguished on the basis of the characteristics of their cortical connections to V1. The first group contains area V2, V3, and the posterior region of V4. These areas project to V1 with infra- as well as supragranular layer neurons and show limited axonal arborization and scatter in the projection. The second group consists of two regions of labelling in the superior temporal sulcus corresponding to V4t and MT and another on the annectant gyrus (V3A). These regions contain almost exclusively infragranular labelling and show wide axonal arborization and scatter in their projections to V1.(ABSTRACT TRUNCATED AT 400 WORDS)

Driver Behavior at Intersections: An Analysis of Accident Related Variables

An intersection driving simulation was created by providing research participants with a video display of approaching intersections in a 120 degree visual field. Six groups were formed according to age and sex. All participants viewed 14 different intersections containing varied traffic control devices. Individual workload was assessed in three response modes: performance, subjective, and physiological. A MANOVA was performed on six dependent variables in the 3 (age) X 2 (sex) design. Results indicate significant main effects for both age and sex.

The cortical magnification factor and photopic vision.

Summary1. The concept of a topographical representation of sensory surfaces on the mammalian cerebral cortex is now well established. Furthermore, there is claimed an expanded representation for those sensory surfaces associated with behavioural specializations.2. In the case of the visual system, the field of view associated with the retina is projected on to the striate cortex, with the central fovea or point of most acute vision occupying a disproportionately large area of representation.3. The term ‘cortical magnification factor’, denoted by M, has been introduced to indicate, for a given eccentricity and meridian, the linear distance in mm along the primary visual cortex concerned with each degree of visual field.4. The quantitative accuracy of this function subsequently has been improved and a relationship established between cortical magnification and visual acuity in man.5. On the basis of spatio‐temporal investigations across the visual field under levels of photopic adaptation, visual scientists have utilized retino‐cortical magnification to reconcile aspects of structure and function in the human visual system.

The representation of the visual field in parvicellular and magnocellular layers of the lateral geniculate nucleus in the macaque monkey.

Two-dimensional maps of individual layers of the dorsal lateral geniculate nucleus (LGN) in the macaque monkey were constructed and used as a basis for comparing laminar size, shape, and topographic organization. Topographical data from the electrophysiological investigation of the LGN by Malpeli and Baker ('75) were displayed on maps of all six layers. As known from previous studies, there is a significant over-representation of central vision in the LGN. Unexpectedly, though, the visual representation is anisotropic over portions of most LGN layers. That is, the linear magnification factor (millimeters along the laminar surface per degree of visual field) is not equal for all directions from a given point in the visual field. Moreover, the visual representations in the parvicellular and magnocellular divisions of the LGN differ both in their emphasis on central vision and in their anisotropies. To determine the degree of individual variability, laminar maps were prepared from the LGN of seven other hemispheres. The shapes of laminar maps varied considerably between LGNs, from nearly circular to highly elliptical, but the surface area was relatively constant for each layer. Topographical organization, determined by mapping the optic disc representation on the LGN laminae and by labeling from anterograde and retrograde tracer injections in striate cortex, showed significant individual variability. Interestingly, the visual representations in the LGN and striate cortex are topologically inverted with respect to one another. This indicates that the establishment of geniculocortical connections involves a systematic crossing-over of fibers. Information on cell densities and magnification factors in striate cortex obtained from other studies was compared to the results of the present study in order to estimate ratios of cortical neurons to LGN neurons at different eccentricities. The total number of cortical neurons per LGN neuron is about 130 on average, but it extends over approximately a tenfold range, from less than 100 in the far periphery to nearly 1,000 in the fovea. The estimated number of cells in layers 4A and 4C beta per parvicellular layer neuron is smaller and extends over a slightly narrower range, from 30 to 240, whereas the number of layer 4C alpha neurons per magnocellular neuron varies more widely, from about 45 to 7,000.

Programs SARGON and DELTA: two new principles for the automated analysis of the visual field.

The new Octopus programs SARGON and DELTA are described. The SARGON program makes possible the arbitrary distribution of a maximum number of 66 test locations with a resolution of up to 0.2 degrees across the 60 degrees visual field. Eighty user-defined self-created programs can be permanently stored and recalled later at will from the program diskette.. The program DELTA evaluates perimetric examination results with the aid of a series of statistical tests and investigates whether the data base is sufficient to assume a significant deviation, or alternatively, whether a visual field defect can be explained simply by spontaneous fluctuations or if a true pathologic defect should be assumed at a particular level of significance. Furthermore, the program tests changes in the visual field as a function of time for their statistical significance.

Visual deficits and recovery following monocular lid closure in a prosimian primate

The behavioral consequences of long-term monocular lid closure in 6 deprived and 2 normal prosimian primates (Galago crassicaudatus) were examined using a visual field perimetry technique and a variety of visuomotor tests. Deprived galagos had their right lid sutured either within 8 (n = 4) or 38 (n = 2) days postpartum and were reared under these conditions for at least 8 months. Normal galagos responded briskly on all visuomotor tests including tracking, response to visual threat, ability to descend from a platform, and obstacle avoidance. Perimetry tests of these animals showed that the visual field with both eyes open was 180 degrees while each eye tested individually had a 135 degrees field. Deprived galagos tested with their experienced eye exhibited normal visuomotor behavior and normal visual fields. Following reverse suture all deprived animals behaved initially as if blind on all tests. Over the next 4-8 weeks these animals showed some limited recovery on the visuomotor tasks. Tests of perimetry indicated that by the end of four weeks of testing, vision was limited to the deprived monocular segment where it remained stable to the end of the testing period. With both eyes open, deprived galagos exhibited a normal 180 degrees visual field. Curiously, however, when stimuli were introduced simultaneously in corresponding points in both monocular segments of the field, the majority of orienting responses of deprived subjects favored the right deprived eye. Under similar testing conditions one normal subject favored its right eye and the other its left eye. The reversibility of monocular deprivation was explored further either by extending the period of forced use of the deprived eye in one animal or by removing the non-deprived eye in another animal. No further improvement in visual field perimetry was seen following a longer period of forced use of the deprived eye. In contrast, a substantial increase in the visual field could be demonstrated one month following removal of the originally experienced eye: the deprived eye field expanded to include the entire 90 degrees ipsilateral hemifield. The contralateral field of the deprived eye, however, continued to remain blind even after one year. These behavioral results suggest that although the original binocular competitive disadvantage suffered by the deprived eye during development is relatively permanent, it can partially be ameliorated by late removal of the non-deprived eye.

The Alteration in Static Perimeter Thresholds Caused by the Prismatic Effect of Ophthalmic Lenses

Contrast sensitivity for target I (3.24/diameter) of the 30 cm radius Goldmann perimeter was measured along the horizontal meridian to 50 degrees eccentricity in 5 subjects. Background luminance was 10.0 cd/m2 and stimulus duration was 130±4 ms. Using this data and the ophthalmic lens prismatic effects to be presented in another paper, the alteration in static perimetric sensitivity caused by spectacle lens prismatic effects was estimated. For spectacle lenses with powers between -6 D and + 10 D, the maximum sensitivity alteration was only 0.30 log units (+10 D, 25 degrees temporal) for a 14 mm vertex distance. As the experiment used conditions producing maximum visual field sensitivity gradients, and hence the maximum alteration in sensitivity caused by prismatic effects, prismatic effects of corrective ophthalmic lenses can be ignored within the central 30 degrees - 40 degrees visual field during static perimetry for lens powers less than ± 10 D.

Effects of the number and form of stimuli on visual search in the pigeon.

Pigeons' pecks at small luminous forms on a large display field were photoelectrically recorded. Pecks to target (S+) forms were reinforced with food; pecks to distractor (S-) forms produced a short time-out. The speed and accuracy of search for a target declined as the number of distractors increased to a maximum of 15. Search was further impaired when the distractors were quite similar to the target. However, search was unaffected by a change in the number of potential targets (memory set size) from one to two, nor was it clearly affected by the use of several different distractor forms instead of a single repeated form. Search was swift over a large (50 degrees) visual field, in the apparent absence of substantial head and eye movements.