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Sensory factors are insufficient to define the ocular saccade goal in complex visual fields.

In most normal visual search situations, the environment is filled with a variety of stimuli, and selection among possible saccade targets is necessary. Current theories of visuomotor mechanisms must take into account not only the classical 'retinal error' input signal, but also perceptual and decisional factors as well as task-specific strategies adopted by the subjects. Experiments are reported in which eye movements are recorded in tasks requiring ocular saccades to be made onto target letters indicated by a peripherally visible mark or embedded within lines of homogeneous background letters. The results show how nonsensory factors interact with visual determinants in the preparation of the exploratory saccades. Expectations concerning the visibility of the sought-for target influence the spatial and temporal parameters of the eye movement which will be executed.

Attention↗

Relationship between retinal nerve fiber layer and visual field sensitivity as measured by optical coherence tomography in chiasmal compression.

PURPOSE: To investigate the spatial relationship between retinal nerve fiber layer (RNFL) thickness measured with optical coherence tomography (OCT) and visual field sensitivity (VFS) measured by standard automated perimetry (SAP) in chiasmal compression. METHODS: Twenty-six patients with chiasmal compression were enrolled. RNFL thickness was measured with the StratusOCT and VFS with SAP (Humphrey Field Analyzer; both from Carl Zeiss Meditec, Dublin, CA). Relationships between RNFL thickness (in clock hours, hemifields, and sectors) and VFS (zones were divided into hemifields, quadrants, and sectors based on a validated visual field map) expressed in a decibel scale and 1/lambert (L) were evaluated by linear and nonlinear regression. Coefficients of determination (R(2)) were calculated by using a multivariate model. RESULTS: Average RNFL thickness correlated strongly with pattern standard deviation (PSD; R = 0.622) and mean deviation (MD; R = 0.413). The four strongest correlations were between the 8 o'clock OCT position (temporal disc), with the temporal hemifield (R = -0.813), the superotemporal quadrant (R = -0.847), the inferotemporal quadrant (R = -0.855), and the field sector representing the papillomacular bundle (R = -0.809). Coefficients of determination improved significantly in all sectors when time since surgery was included in the regression model-most notably, average thickness and 1/L (R(2) = 0.35-0.49), the decibels (R(2) = 0.31-0.47), and the temporal sector (R(2) = 0.44-0.57). CONCLUSIONS: This is the first study to compare the structure-function correlation of RNFL measured by OCT with SAP in patients with chiasmal compression. RNFL is topographically related globally and sectorally to decreased SAP, with the temporal sectors showing the strongest correlations. The correlation between RNFL and VFS strengthens as the time from surgical intervention increases.

Adolescent↗

Intraocular pressure, cardiovascular risk variables, and visual field defects.

This study evaluates the associations of intraocular pressure with cardiovascular risk factors among 2433 participants in the Framingham Eye Study and the Framingham Heart Study. Persons with intraocular pressure greater than 21 mmHg in at least one eye had an increased prevalence of hypertension and diabetes; no association was found with cardiovascular disease. In multiple regression analysis, systolic blood pressure was the variable most related to intraocular pressure; vertical cup/disc ratio, diabetes, and ventricular rate were also independently related to intraocular pressure. About 6% of the variation in intraocular pressure was explained by these variables. Although blood pressure was associated with intraocular pressure in eyes without visual field defects, this association could not be detected in eyes with field defects; interaction tests found significant differences in the blood pressure-intraocular pressure relationships between visual field groups. Ratios of blood pressure to intraocular pressure were lower in eyes with visual field defects than in eyes without field defects.

Blood Pressure↗

Attention can be oriented to intermediate locations within the large area of the visual field.

The present study examined whether attention can be evenly distributed within the large area of the visual field. The stimulus was presented at one of four locations on the horizontal meridian (0 degrees, 10 degrees, 20 degrees, and 30 degrees to the right). In the Fixed Location condition, the stimulus appeared repeatedly at the same location. In the Random Location condition, the stimulus appeared at one of four locations as determined randomly with equal probability. Reaction times (RTs) in the Random Location condition were significantly longer than those in the Fixed Location condition at the 0 degrees and 30 degrees locations, while there were no significant differences at the 10 degrees and 20 degrees locations. The differences in the RT between conditions were significantly larger at the 0 degrees and 30 degrees locations than those at the 10 degrees and 20 degrees locations. These results suggest that attention was oriented to intermediate locations within the large area of the visual field.

Adult↗

Short-wavelength sensitive visual field loss in patients with clinically significant diabetic macular oedema.

The aim of the study was to compare the sensitivity of short-wavelength and conventional automated static threshold perimetry for the psychophysical detection of abnormality in patients with clinically significant diabetic macular oedema. The sample comprised 24 patients with clinically significant diabetic macular oedema (mean age 59.75 years, range 45-75 years). One eye of each patient was selected. Exclusion criteria included the presence of lenticular opacity. The sensitivity of the macular visual field of each patient was determined with programme 10-2 of the Humphrey Field Analyser on two occasions, using both short-wavelength and conventional stimulus parameters; the results of the second session were analysed to minimise learning effects. A pointwise horizontal hemifield asymmetry analysis was derived for short-wavelength perimetry (thereby negating the influence of pre-receptoral absorption); the pointwise pattern deviation probability plot was analysed for conventional perimetry. Abnormality was defined as 3 or more contiguous stimulus locations with negative asymmetries (short-wavelength) or reduced sensitivity values (conventional) that resulted in a statistical probability level of p less than 0.05. The fields of 8 patients were abnormal as assessed by conventional perimetry while all were classified as abnormal using short-wavelength perimetry. In the 8 patients who exhibited both abnormal conventional and abnormal short-wavelength perimetry results, the extent of field loss was generally greater using short-wavelength perimetry. The position of the localised field loss (i.e. as distinct from field loss that was generalised across the visual field) assessed by short-wavelength perimetry corresponded with the clinical mapping of the area of diabetic macular oedema but the extent of this loss was generally greater than that suggested by clinical assessment. Short-wavelength automated perimetry offers improved sensitivity for the psychophysical detection of clinically significant diabetic macular oedema.

Aged↗

Ocular perfusion pressure and visual field indice modifications induced by alpha-agonist compound (clonidine 0.125%, apraclonidine 1.0% and brimonidine 0.2%) topical administration. An acute study on primary open-angle glaucoma patients.

OBJECTIVE: The aim of this study was to verify the acute effects of alpha-adrenoreceptor agonist eyedrop administration on visual field parameters and ocular perfusion pressure (OPP) in patients affected by primary open-angle glaucoma. METHODS: A prospective, randomized double-blind study was carried out. Sixty-four glaucomatous subjects were enrolled in the clinical trial and subsequently separated into four study groups, of 16 patients each, to compare the systemic and ocular effects of placebo, clonidine 0.125%, apraclonidine 1.0% and brimonidine 0.2%. RESULTS: No significant variations in the ocular or systemic parameters were observed after placebo administration. All the alpha-adrenoreceptor agonist compounds induced a significant reduction of the intraocular pressure. Clonidine induced significant modifications of mean blood pressure, OPP and visual field indices. The acute administration of apraclonidine did not affect both mean blood pressure and OPP, but a worsening of the visual field was nevertheless recorded. The analyzed parameters did not significantly vary after brimonidine instillation. CONCLUSIONS: The present findings demonstrate that the lack of effects on the blood flow and the absence of vasomotor activity at the level of the posterior pole exhibited by brimonidine is related to its alpha-2 selectivity, as appears by comparing this compound with the other alpha-agonists available for the management of glaucoma.

Administration, Topical↗

The progress of the visual field in chronic simple glaucoma and ocular hypertension treated topically with pilocarpine or with timolol.

It is theoretically possible that the vascular effects of topical sympathetic beta-blocking therapy in chronic simple glaucoma (CSG) might tend to neutralise the beneficial effect of a reduced intraocular pressure on the preservation of the visual field. We therefore followed the progress of 422 right eyes and 420 left eyes of 483 patients with CSG and 119 right eyes and 132 left eyes of 151 patients with an original diagnosis of ocular hypertension (OH). These patients were observed for a minimum of one year and up to 13 years, being followed for an average of 5.1 years in the case of CSG and of 4.5 years in OH. The majority of eyes with CSG were treated topically with a miotic and 38% of these received beta blocking therapy in the form of topical timolol. It was concluded that despite suggestions that beta blockers might reduce vascular perfusion of the optic nerve head, which might in turn cause an adverse effect on the visual field progress, the results of this analysis showed that there was less mean deterioration of visual field in eyes treated with beta blocker plus miotic treatment compared with those on miotic therapy alone.

Administration, Topical↗

The detection of glaucomatous visual field defects by oculo-kinetic perimetry: which points are best for screening?

Oculo-kinetic perimetry (OKP) uses the patient's ocular movements to position a test stimulus in the visual field. By virtue of its simplicity and low cost, this test could be useful in the screening of glaucoma. The general purpose OKP chart, however, which tests 100 points in the central 25 degrees field, is too time-consuming for this purpose, taking approximately 4-7 minutes per eye. Accordingly, this study was performed to identify the points most likely to detect patients with glaucoma. Fifty-one eyes with glaucomatous visual field defects and 51 non-glaucomatous eyes of age matched individuals were tested by conventional and oculo-kinetic perimetry. At least one of only six points were missed by 82.4% of glaucomatous eyes and by 9.8% of nonglaucomatous eyes. These results, although falling short of the ideal efficiency, are comparable with data published by other research groups using computerised equipment and suggest that, with further development, a specialised OKP chart testing only a small number of points might be valuable in screening for glaucoma.

Adult↗

Visual field effects in the discrimination of sine-wave gratings.

The time needed to decide whether the second of two successively presented sinusoidal gratings was of a higher or lower spatial frequency than the first was measured for spatial frequencies of 1, 2, 4, 8, and 12 cycles per degree (cpd) presented in either the left visual field (LVF) or right visual field (RVF). A LVF advantage was found for discriminating within the low-spatial-frequency range (i.e., 1 and 2 cpd), whereas a RVF advantage was found for discriminating within the high-spatial-frequency range (i.e., 4-12 cpd). These findings support the conclusion that hemispheric asymmetries in the processing of gratings arise when comparisons are made between the output of spatial-frequency channels.

Adult↗

Variation in visual field measurements with an automated perimeter.

Using the Octopus automated perimeter, we conducted visual measurements on four separate occasions during a four-week period in six subjects with normal eyes. In 11 of 12 eyes, we found at least one point at which the threshold for light detection determined for that point showed a variance of more than 4 dB between tests. Thus, automated visual fields must be interpreted cautiously because an apparent pathologic change may only represent normal variation.

Adult↗

Automated perimetry detects visual field loss before manual Goldmann perimetry.

PURPOSE: To determine if automated perimetry detects visual field defects before manual Goldmann perimetry. METHODS: Subjects with ocular hypertension without field loss on detailed manual perimetry were followed prospectively with annual automated and manual perimetry. Subjects with field loss on manual perimetry were age-matched post hoc to subjects who did not have field loss. The automated fields 1 year before the development of field loss on manual perimetry were compared between the two groups. Subjects were recruited from ophthalmologists' offices, eye clinics, and a population-based glaucoma survey in the Baltimore area. Abnormal results detected on the Humphrey Field Analyzer were defined using the glaucoma hemifield test, mean defect, and corrected-pattern standard deviation. RESULTS: Forty subjects who had field loss during 8 years of follow-up were compared with 145 control subjects with ocular hypertension who did not have defects. Seventy-five percent of converters had abnormal results of the glaucoma hemifield test 1 year before field loss on manual perimetry, whereas 22% of controls had abnormal results of the glaucoma hemifield test (odds ratio, 13.4). The odds ratio of field loss developing on manual perimetry within 12 months was 3.3 for those with borderline results of the glaucoma hemifield test relative to the control subjects. The odds ratio was 6.0 for corrected-pattern standard deviation (P < 0.05) and 3.9 for mean deviation (P < 0.05). CONCLUSIONS: Those with field loss on manual perimetry were more likely to have had an abnormal automated field 1 year before conversion than those who did not convert. However, 22% of subjects in whom definitive field loss did not develop on manual perimetry during the study had abnormal automated fields at one visit and 15% had abnormal automated fields on two consecutive visits.

Aged↗

The complete pattern of ocular dominance stripes in the striate cortex and visual field of the macaque monkey.

Ocular dominance stripes in the striate cortex of a macaque monkey were labeled by autoradiography after injection of [3H]proline into one eye. The stripes were reconstructed on a representation of the flattened cortical surface by two independent techniques: one used computer graphics, and the other was the manual unfolding procedure of Van Essen and Maunsell (VanEssen, D. C., and J. H. R. Maunsell (1980) J. Comp. Neurol. 191: 255-281). The two reconstructions differed in many details of the pattern but were in agreement on its general features. As described in earlier studies, the stripes formed a system of parallel bands, with numerous branches and islands. They were roughly orthogonal to the V1/V2 border throughout the binocular segment of the cortex. In the lateral part of the operculum, where the fovea is represented, the stripes were less orderly than elsewhere. In the calcarine fissure the stripes ran directly across the striate cortex from its dorsal to its ventral margin. In the far periphery the stripes for the ipsilateral eye became progressively narrower, eventually fragmenting into small islands at the edge of the monocular segment. The overall periodicity (width of a left- plus right-eye pair of stripes) averaged 0.88 mm but decreased by a factor of about 2 from center to periphery. This decrease was not accounted for solely by shrinkage of the ipsilateral eye stripes. The flattened cortical reconstruction was transformed back into visual field coordinates, using information about visual field topography obtained from the detailed mapping study of Van Essen et al. (Van Essen, D.C., W.T. Newsome, and J.H.R. Maunsell (1984) Vision Res. 24: 429-448), as well as from more limited mapping done in the same monkey that was used for the reconstruction. In the transformed map, the stripes increased in width about 40-fold from the fovea to the far periphery. As deduced previously (LeVay, S., D. H. Hubel, and T. N. Wiesel (1975) J. Comp. Neurol. 159: 559-576; Hubel, D. H., and D. C., Freeman (1977) Brain Res. 122: 336-343), there were portions of the map in which the stripes followed curves approximating isoeccentricity lines, but this relationship was not very exact or consistent. The pattern of stripes appears to be more meaningfully related to the geometry of the cortical surface. This has significant implications for understanding the developmental mechanisms involved in stripe formation.

Animals↗

Static threshold visual field in glaucoma with the Fastpac algorithm of the Humphrey Field Analyser. Is the gain in examination time offset by any loss of information?

A new algorithm (Fastpac) has been designed to speed up full threshold tests with the Humphrey Field Analyser. We studied the utility of this algorithm by comparing central 24-2 threshold programs obtained with standard and Fastpac algorithms in 43 hypertensive or glaucomatous eyes. The Fastpac reduced testing time by 35% to 45%. In glaucomatous eyes, the time spared was inversely correlated with the degree of visual field impairment. Global indices were used to compare visual fields. Mean absolute differences in indices did not exceed 0.98 dB. Correlations between indices in glaucoma patients with standard and Fastpac strategy were respectively 0.99 and 0.98 for mean deviation and pattern standard deviation. The intra-test variability (short-term fluctuation) was slightly higher with Fastpac with a lower correlation between algorithms (r = 0.62). The use of Fastpac achieves a mean time reduction of 40% and does not significantly modify global indices obtained with the Humphrey perimeter in hypertensive and glaucomatous eyes.

Adult↗

Visual field global indices in patients with reversal of glaucomatous cupping after intraocular pressure reduction.

The authors investigated visual field changes in 28 eyes of 28 adult patients with early-to-moderate chronic open-angle glaucoma (COAG) in whom reversal of glaucomatous disc cupping was documented by computerized image analysis (Rodenstock Optic Nerve Head Analyzer) after intraocular pressure (IOP) reduction from 29.3 (+/- 5.9) to 19.4 (+/- 4.3) mmHg over 34.8 (+/- 24.8) weeks. Humphrey Statpac global indices (mean deviation and pattern standard deviation) improved in direct proportion to the magnitude of IOP reduction even after controlling for the possible influences of learning effect, short-term fluctuation, reliability, duration of IOP reduction, age, and pupil size. The mean visual field global indices (mean deviation and pattern standard deviation) improved in patients with IOP reduction of 40% or greater, in statistically significant contrast to no improvement of mean global indices with IOP reduction less than 35%. The beneficial effect of IOP reduction is apparent in COAG patients with topographical evidence of reversal of cupping.

Adult↗

Effects of concurrent memory load on visual-field differences in mental rotation.

Normal right-handers mentally rotated letters flashed in the left or right visual fields under different conditions of working-memory load. In Experiment 1, the subjects held patterns of eight dots or sequences of eight letters in working memory, and these conditions produced a progressively increasing right visual field (RVF) advantage in rate of mental rotation relative to a control condition in which there was no load. Experiment 2 confirmed the shift toward increasing RVF advantage with a load of eight digits relative to two control conditions, one in which there was no load and another in which the subjects recalled digits before carrying out the mental rotation on each trial. These results are discussed in terms of the priming of the hemispheres by the concurrent loading of working memory.

Adolescent↗

Losses of hemifield contrast sensitivity in patients with pituitary adenoma and normal visual acuity and visual field.

OBJECTIVE: To detect early losses of contrast sensitivity (CS) in patients with pituitary adenomas, before the occurrence of visual acuity and visual field defects. METHODS: CS has been evaluated in both hemifields of 28 patients with different kinds of pituitary adenoma (mainly intrasellar) and normal visual acuity and visual field, as well as in 15 age-matched controls. Two different stimuli were used: a coarse (0.3 c/deg) dynamic (10 Hz) grating and a finer (2 c/deg) static grating. RESULTS: On average, CS and/or hemifield asymmetry were reduced in patients, whereas perimetric sensitivity was normal. CS losses were more frequent for 2 c/deg static-, as compared with 0.3 c/deg, 10 Hz stimuli. However selective losses for either stimuli were also found. CS losses did not correlate with anatomical measurements (size, chiasm involvement) of tumors as established by MRI scans. CONCLUSIONS: CS evaluation may provide a simple and effective tool for early detection and monitoring of visual dysfunction in patients with pituitary adenoma. The lack of correlation between CS losses and chiasm involvement suggests causes different from chiasmal compression for visual dysfunction.

Adenoma↗

Visual field defects and other ophthalmological disturbances associated with vigabatrin.

Vigabatrin has been an important anticonvulsant drug for over 10 years with a reputation for high efficacy and excellent tolerability. However, since 1997, there have been over 25 reports in the literature of visual field defects attributable to the use of this agent. Most are case reports and many have only been reported as abstracts or posters or as letters or short communications. Only a small number of papers give details of patient characteristics. Typically, case reports detail ophthalmological tests such as visual acuity, funduscopic examination, integrity of colour vision, and the nature of the field cut. Many also include various electrophysiological tests which were performed in an attempt to further describe the nature of the visual changes. In order to shed light on the mechanism underlying these visual field changes, many investigators also tested various electrophysiological parameters. However, because electrophysiological testing requires considerable expertise on the part of the technician, this could be a source of variability in results and may also pose a challenge with data interpretation. The magnitude of the problem is difficult to assess. The manufacturer's estimate of incidence of visual field defects with vigabatrin was approximately 0.1%, but incidences estimated in the literature range from 6 to 30%. Since the majority of the published data are in case report form, proof of causation is also very difficult. Two papers that used proper scientific methodology to investigate this condition suggest that vigabatrin causes these changes; however, there needs to be further studies with larger populations to answer this question definitively. There is a lack of data on the dose-response characteristics of vigabatrin and the development of visual field defects. The only available data are reports of trends that implicate duration of therapy or cumulative dose. Perhaps the most important area to elucidate is whether or not the visual field defects are reversible. Data are scare on this subject, but we can hope that data will emerge as follow-up periods become more substantial. There is a need for more complete information regarding several aspects of the mechanistic basis of visual field defects associated with vigabatrin that will allow rational clinical decision making. The treatment choices, both pharmacological and nonpharmacological, for patients with refractory epilepsy have grown substantially in the last few years. Thus, it is doubtful that the clinical positioning of vigabatrin is likely to change in the future from that of a very valuable 'niche drug', with emphasis on paediatric usage.

Anticonvulsants↗