Concept: Visual field
A positivity advantage is known in emotional word recognition in that positive words are consistently processed faster and with fewer errors compared to emotionally neutral words. A similar advantage is not evident for negative words. Results of divided visual field studies, where stimuli are presented in either the left or right visual field and are initially processed by the contra-lateral brain hemisphere, point to a specificity of the language-dominant left hemisphere. The present study examined this effect by showing that the intake of caffeine further enhanced the recognition performance of positive, but not negative or neutral stimuli compared to a placebo control group. Because this effect was only present in the right visual field/left hemisphere condition, and based on the close link between caffeine intake and dopaminergic transmission, this result points to a dopaminergic explanation of the positivity advantage in emotional word recognition.
The purpose of this study was to evaluate the visual outcome of chronic occupational exposure to a mixture of organic solvents by measuring color discrimination, achromatic contrast sensitivity and visual fields in a group of gas station workers. We tested 25 workers (20 males) and 25 controls with no history of chronic exposure to solvents (10 males). All participants had normal ophthalmologic exams. Subjects had worked in gas stations on an average of 9.6 ± 6.2 years. Color vision was evaluated with the Lanthony D15d and Cambridge Colour Test (CCT). Visual field assessment consisted of white-on-white 24-2 automatic perimetry (Humphrey II-750i). Contrast sensitivity was measured for sinusoidal gratings of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0 and 20.0 cycles per degree (cpd). Results from both groups were compared using the Mann-Whitney U test. The number of errors in the D15d was higher for workers relative to controls (p<0.01). Their CCT color discrimination thresholds were elevated compared to the control group along the protan, deutan and tritan confusion axes (p<0.01), and their ellipse area and ellipticity were higher (p<0.01). Genetic analysis of subjects with very elevated color discrimination thresholds excluded congenital causes for the visual losses. Automated perimetry thresholds showed elevation in the 9°, 15° and 21° of eccentricity (p<0.01) and in MD and PSD indexes (p<0.01). Contrast sensitivity losses were found for all spatial frequencies measured (p<0.01) except for 0.5 cpd. Significant correlation was found between previous working years and deutan axis thresholds (rho = 0.59; p<0.05), indexes of the Lanthony D15d (rho=0.52; p<0.05), perimetry results in the fovea (rho= -0.51; p<0.05) and at 3, 9 and 15 degrees of eccentricity (rho= -0.46; p<0.05). Extensive and diffuse visual changes were found, suggesting that specific occupational limits should be created.
Variations in crowding, saccadic precision, and spatial localization reveal the shared topology of spatial vision
- Proceedings of the National Academy of Sciences of the United States of America
- Published about 1 year ago
Visual sensitivity varies across the visual field in several characteristic ways. For example, sensitivity declines sharply in peripheral (vs. foveal) vision and is typically worse in the upper (vs. lower) visual field. These variations can affect processes ranging from acuity and crowding (the deleterious effect of clutter on object recognition) to the precision of saccadic eye movements. Here we examine whether these variations can be attributed to a common source within the visual system. We first compared the size of crowding zones with the precision of saccades using an oriented clock target and two adjacent flanker elements. We report that both saccade precision and crowded-target reports vary idiosyncratically across the visual field with a strong correlation across tasks for all participants. Nevertheless, both group-level and trial-by-trial analyses reveal dissociations that exclude a common representation for the two processes. We therefore compared crowding with two measures of spatial localization: Landolt-C gap resolution and three-dot bisection. Here we observe similar idiosyncratic variations with strong interparticipant correlations across tasks despite considerably finer precision. Hierarchical regression analyses further show that variations in spatial precision account for much of the variation in crowding, including the correlation between crowding and saccades. Altogether, we demonstrate that crowding, spatial localization, and saccadic precision show clear dissociations, indicative of independent spatial representations, whilst nonetheless sharing idiosyncratic variations in spatial topology. We propose that these topological idiosyncrasies are established early in the visual system and inherited throughout later stages to affect a range of higher-level representations.
Transient monocular blindness and amaurosis fugax are umbrella terms describing a range of patterns of transient monocular visual field loss (TMVL). The incidence rises from ≈1.5/100,000 in the third decade of life to ≈32/100,000 in the seventh decade of life. We review the vascular supply of the retina that provides an anatomical basis for the types of TMVL and discuss the importance of collaterals between the external and internal carotid artery territories and related blood flow phenomena. Next, we address the semiology of TMVL, focusing on onset, pattern, trigger factors, duration, recovery, frequency-associated features such as headaches, and on tests that help with the important differential between embolic and non-embolic etiologies.
PURPOSE: To investigate the effect of the lateral decubitus position (LDP) on intraocular pressure (IOP) in glaucoma patients with asymmetric visual field loss. DESIGN: Prospective, cross-sectional study. PARTICIPANTS: Ninety-eight eyes of 49 consecutive bilateral glaucoma patients with asymmetric visual field loss, divided into better eye and worse eye groups for calculation of mean deviation. METHODS: Intraocular pressure was measured using a Goldmann applanation tonometer and rebound tonometer (Icare PRO; Icare Finland Oy, Helsinki, Finland) in each of the following positions: sitting, supine, right LDP, and left LDP. Visual field was examined using the Humphrey Field Analyzer (HFA II; Carl Zeiss Meditec, Dublin, CA). A questionnaire on the preferred lying position during sleep was administered to each of the patients. MAIN OUTCOME MEASURES: The IOPs measured by rebound tonometer for the better and worse eyes in each position were compared using paired t tests. Agreement between the Goldmann applanation tonometry and rebound tonometry results was assessed by a Bland-Altman plot. RESULTS: The IOPs of the better and worse eyes in the sitting position showed no significant difference (P<0.476). The IOP of the worse eye was significantly higher than that of the better eye in the supine position (16.8±3.0 mmHg vs. 15.1±1.8 mmHg; P<0.001). The IOPs of the worse and better eyes in their dependent LDP were 19.1±3.0 mmHg and 17.6±2.3 mmHg, respectively (change in IOP, 1.6±2.4 mmHg; P<0.001). Of the enrolled patients, 75.5% preferred the LDP, and 75.7% of these LDP-preferring patients preferred the worse eye dependent-LDP. The Bland-Altman plot comparing the Goldmann applanation tonometry and rebound tonometry readings showed reasonable agreement between the 2 methods (r(2)<0.001; P = 0.972). CONCLUSIONS: This study showed that IOP-elevation asymmetry in LDP is associated with asymmetric visual field loss in glaucoma patients. The LDP, habitually preferred by glaucoma patients, also may be associated with asymmetric visual field damage. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
PURPOSE: To explore the diagnostic performance of threshold visual field tests using subsets of the Swedish Interactive Threshold Algorithm (SITA) standard 24-2 test pattern in detecting early/moderate glaucomatous field loss. METHODS: Normal (Brusini stage 0, n=2344) and defective eyes (Brusini stage 2-3, n=2222) from a database of visual field tests (6696 eyes/3586 patients, SITA standard 24-2 algorithm) were selected and re-sampled using a bootstrap method. The positive predictive values (PPV) of each test location were calculated for the re-sampled datasets with a fail criteria of a single missed stimulus at a pattern deviation probability level of <0.01. Optimized test patterns started with the most frequent location of the maximum PPV in datasets. Eyes missing the location were removed and the PPV values of residual sample recalculated. The process was repeated until all defective eyes were detected. Receiver operating characteristic (ROC) curves were established for the PPV-optimized and five randomized patterns. Characteristics of visual field defects detected with subsets of optimized test pattern were established. RESULTS: With the PPV-optimized pattern, 95% of the field defects were detected with 30 locations and all with 43 locations. Areas under the ROC curve were greatest for the optimized pattern. With each increment in the number of test locations, the Mean Deviation of additionally detected eyes became more positive while Pattern Standard Deviation became less positive (p<0.001). CONCLUSIONS: Good diagnostic performance can be obtained with optimized subsets of the current 24-2 stimulus pattern that can provide substantial savings in test times.
Purpose. To report a case of scleral dislocation mimicking glaucoma progression. Methods. Interventional case report. Results. A 71-year-old man was referred for glaucoma surgery in his right eye because of perimetry defect progression and uncontrolled intraocular pressure despite maximal medical therapy. A scleral buckling procedure in his right eye was previously performed for rhegmatogenous retinal detachment. At the time of presentation, a visible protruded sponge buckle element was noted at ocular inspection, without any sign of infection. The buckle element was posteriorly in contact with the optic nerve and anteriorly protruding under intact conjunctiva. We eventually managed for its removal via upper eyelid orbitotomy. Visual field lesions were unchanged on every follow-up visit. Conclusions. This case report describes severe permanent optic nerve damage due to previous misdiagnosis of a rare complication of scleral buckling surgery. Our surgical solution appears to be a safe and successful approach for this ocular disorder, also able to stabilize visual function and interrupt disease progression.
BACKGROUND: The purpose of the study was to compare the monocular Humphrey Visual Field (HVF) with the binocular Humphrey Esterman Visual Field (HEVF) for determining whether subjects suffering from glaucoma fulfill the new medical requirements for possession of a Swedish driver’s license. METHODS: HVF SITA Fast 24-2 full threshold (monocularly) and HEVF (binocularly) tests were performed consecutively on the same day on 40 subjects with glaucomatous damage of varying degrees in both eyes. Assessment of results was constituted as either “passing” or “failing” score, according to the new medical requirements put into effect September 1, 2010 by the Swedish Transport Agency. RESULTS: Forty subjects were recruited and participated in the study. Sixteen subjects passed both tests, and sixteen subjects failed both tests. Eight subjects passed the HEFV but failed the HVF. There was a significant difference between HEVF and HVF (chi2, p=0.004). There were no subjects who passed the HVF, but failed the HEVF. CONCLUSIONS: The monocular visual field test (HVF) gave more specific information about the location and depth of the defects, and therefore is the overwhelming method of choice for use in diagnostics. The binocular visual field test (HEVF) seems not be as efficient as the HVF in finding visual field defects in glaucoma patients, and is therefore of doubtful use in evaluating visual capabilities in traffic situations.
Purpose: To investigate the clinical value of assessment of peripapillary retinal nerve fibre layer (RNFL) thickness with OCT in addition to the evaluation of retinal function measured by full-field electroretinography (ff-ERG) in patients with suspected vigabatrin (VGB)-attributed visual field defects. Methods: Visual fields from adult patients in our clinical follow-up program for VGB medication were analysed. Twelve patients with suspected VGB-attributed visual field defects were selected for the study. They were re-examined with computerized kinetic perimetry, ff-ERG and OCT (2D circle scan). Results: Constricted visual fields were found in all patients. Comparative analysis of ff-ERG parameters showed reduced b-wave amplitudes for the isolated and the combined rod and cone responses (p < 0.0001). The a-wave, reflecting photoreceptor activity, was reduced (p = 0.001), as well as the summed amplitude of oscillatory potentials (p = 0.029), corresponding to inner retinal function. OCT measurements demonstrated attenuation of the RNFL in nine of 12 patients, most frequently superiorly and/or inferiorly. No temporal attenuation was found. Significant positive correlations were found between the total averaged RNFL thickness, superior and inferior RNFL thickness and reduced ff-ERG parameters. Positive correlations were also found between RNFL thickness and isopter areas. Conclusion: OCT measurements can detect attenuation of the RNFL in patients exposed to VGB medication. RNFL thickness correlates with reduced ff-ERG parameters and isopter areas of constricted visual fields, indicating that VGB is retino-toxic on several levels, from photoreceptors to ganglion cells. The study also supports previous studies, suggesting that OCT measurement of the RNFL thickness may be of clinical value in monitoring patients on vigabatrin therapy.
Spontaneous intracranial hypotension (SIH) is a rare syndrome characterized by postural headache associated with a low cerebrospinal fluid pressure in the absence of dural puncture or penetrating trauma. Cranial magnetic resonance imaging (MRI) typically shows diffuse pachymeningeal gadolinium enhancement, subdural fluid collections, prominence of cerebral venous sinuses and brain descent. Visual signs and symptoms have been described infrequently in patients with SIH. These include third or sixth nerve palsy, superior nasal quadrantanopia and temporal hemianopia. We report a 34 year-old woman who presented with a two-year history of orthostatic headache, dizziness and transient visual obscurations. Campimetry showed a bilateral concentric visual field defect. She also described that intermittently a transparent fluid leaked out of her nose. She had no past history of trauma, sinus surgery or intracranial surgery. Cranial MRI was normal. Neuro-ophthalmological examination ruled out any other causes of concentric visual field defects. Lumbar puncture showed a cerebrospinal fluid (CSF) opening pressure of 9 cm H(2)O. Radioisotope cisternography suggested a dural leak at cribiform plate. The cribiform plate region was repaired endoscopically with improvement of all symptoms. One year later she remains asymptomatic and the visual field defects have improved.