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Ophthalmic & Physiological Optics : the... Mar 2014(1) To devise a model-based method for estimating the probabilities of binocular fusion, interocular suppression and diplopia from psychophysical judgements, (2) To map... (Review)
Review
PURPOSE
(1) To devise a model-based method for estimating the probabilities of binocular fusion, interocular suppression and diplopia from psychophysical judgements, (2) To map out the way fusion, suppression and diplopia vary with binocular disparity and blur of single edges shown to each eye, (3) To compare the binocular interactions found for edges of the same vs opposite contrast polarity.
METHODS
Test images were single, horizontal, Gaussian-blurred edges, with blur B = 1-32 min arc, and vertical disparity 0-8.B, shown for 200 ms. In the main experiment, observers reported whether they saw one central edge, one offset edge, or two edges. We argue that the relation between these three response categories and the three perceptual states (fusion, suppression, diplopia) is indirect and likely to be distorted by positional noise and criterion effects, and so we developed a descriptive, probabilistic model to estimate both the perceptual states and the noise/criterion parameters from the data.
RESULTS
(1) Using simulated data, we validated the model-based method by showing that it recovered fairly accurately the disparity ranges for fusion and suppression, (2) The disparity range for fusion (Panum's limit) increased greatly with blur, in line with previous studies. The disparity range for suppression was similar to the fusion limit at large blurs, but two or three times the fusion limit at small blurs. This meant that diplopia was much more prevalent at larger blurs, (3) Diplopia was much more frequent when the two edges had opposite contrast polarity. A formal comparison of models indicated that fusion occurs for same, but not opposite, polarities. Probability of suppression was greater for unequal contrasts, and it was always the lower-contrast edge that was suppressed.
CONCLUSIONS
Our model-based data analysis offers a useful tool for probing binocular fusion and suppression psychophysically. The disparity range for fusion increased with edge blur but fell short of complete scale-invariance. The disparity range for suppression also increased with blur but was not close to scale-invariance. Single vision occurs through fusion, but also beyond the fusion range, through suppression. Thus suppression can serve as a mechanism for extending single vision to larger disparities, but mainly for sharper edges where the fusion range is small (5-10 min arc). For large blurs the fusion range is so much larger that no such extension may be needed.
Topics: Diplopia; Humans; Psychophysics; Vision Disparity; Vision, Binocular
PubMed: 24476421
DOI: 10.1111/opo.12108 -
Optometry and Vision Science : Official... Jan 2022We know the prevalence of traumatic brain injury (TBI)-related vision impairment and ocular injury symptoms. Lacking is an understanding of health care utilization to...
SIGNIFICANCE
We know the prevalence of traumatic brain injury (TBI)-related vision impairment and ocular injury symptoms. Lacking is an understanding of health care utilization to treat these symptoms. Utilization knowledge is important to structuring access to treatment, identifying clinical training needs, and providing evidence of the effectiveness of treatment.
PURPOSE
This article reports rehabilitation, glasses/contacts, and imaging/photography/video recommendations made by optometrists and ophthalmologists as part of the Department of Veterans Affairs-mandated Performance of Traumatic Brain Injury Specific Ocular Health and Visual Functioning Examination administered to veterans with TBI at Department of Veterans Affairs polytrauma specialty facilities.
METHODS
Using a retrospective design, natural language processing, and descriptive and regression statistics, data were analyzed for 2458 Operation Enduring Freedom/Operation Iraqi Freedom veterans who were administered the mandated examination between 2008 and 2017.
RESULTS
Of the 2458 veterans, vision rehabilitation was recommended for 24%, glasses/contacts were recommended for 57%, and further imaging/photography/video testing was recommended for 58%. Using key words in the referral, we determined that 37% of veterans were referred to blind rehabilitation, 16% to occupational therapy, and 3% to low-vision clinics. More than 50% of the referrals could have been treated by blind rehabilitation, occupational therapy, or low-vision clinics. Rehabilitation referrals were significantly associated with younger age, floaters, photosensitivity, double vision, visual field and balance deficits, dizziness, and difficulty reading. In comparison, prescriptions for glasses and contacts were associated with older age, photosensitivity, blurred vision, decreased visual field and night vision, difficulty reading, and dry eye. Imaging/photography/video testing was associated with floaters, photosensitivity, and headache.
CONCLUSIONS
Findings delineate service delivery models available to veterans with TBI-related vision impairment. The challenge these data address is the lack of clear paths from diagnosis of TBI to identification of vision dysfunction deficits to specialized vision rehabilitation, and finally to community reintegration and community based-vision rehabilitation.
Topics: Afghan Campaign 2001-; Brain Injuries, Traumatic; Humans; Retrospective Studies; United States; Veterans; Vision Disorders
PubMed: 34882607
DOI: 10.1097/OPX.0000000000001828 -
Advances in Clinical and Experimental... Feb 2022During coronavirus disease 2019 (COVID-19) pandemic, students were obliged to switch to online learning. Nevertheless, a long time spent in front of the screens is one...
BACKGROUND
During coronavirus disease 2019 (COVID-19) pandemic, students were obliged to switch to online learning. Nevertheless, a long time spent in front of the screens is one of the risk factors of dry eye disease (DED).
OBJECTIVES
To evaluate ocular symptoms typical for DED presented by Polish students during online learning and entertainment before and during the pandemic, as well as to assess the prevalence of these symptoms.
MATERIAL AND METHODS
The original questionnaire was distributed online via social media (Facebook) to Polish students in November 2020. Three hundred sixty-eight anonymous questionnaires were collected and statistically analyzed.
RESULTS
During the pandemic, online learning and screen entertainment time extended on average by 4 h and 40 min, respectively. Only 8% of students admitted to having no ocular symptoms and 77% reported the exacerbation in previous ocular complaints. Reported symptoms included pain/discomfort of the eyes, itchiness, dryness, red eyes, feeling gritty particles under eyelids, and blurred vision. Actions such as using eye drops, having breaks from studying to have distant vision, consultation with an ophthalmologist, using warm and cold compresses, or none of these were undertaken by 45%, 42%, 8%, 7%, and 19% of students, respectively. Nonmedical students reported worsening of previous symptoms more often than medical students (p < 0.05). A correlation was observed between the number of new/intensified symptoms and the change in screen learning time (r = 0.17, p < 0.05).
CONCLUSION
Eye complaints are prevalent in the population of students. During the pandemic these symptoms intensified, which may have been caused by the extension of the screen time. There is a need for better education on ocular hygiene to improve visual clarity and awareness of risk factors of DED.
Topics: COVID-19; Dry Eye Syndromes; Humans; Pandemics; SARS-CoV-2; Students, Medical
PubMed: 35077035
DOI: 10.17219/acem/144199 -
Translational Vision Science &... Oct 2021The aim of the current study was to develop and validate an automated contrast sensitivity (CS) test using a live- detection of optokinetic nystagmus (OKN) and an...
PURPOSE
The aim of the current study was to develop and validate an automated contrast sensitivity (CS) test using a live- detection of optokinetic nystagmus (OKN) and an adaptive psychometric procedure. In addition, the study sought to replicate the known effect of defocus on CS for the OKN-based measurements in emmetropic participants.
METHODS
Fifteen participants viewed a horizontally moving grating while their eyes were tracked with an infra-red (IR) eye-tracker. To simulate the clinical conditions of the CS measurements, the participants were stimulated monocularly as the left eye was occluded by an IR filter. The horizontal eye position was continuously analyzed for OKN responses, and the stimulus contrast was changed by an adaptive psychometric method depending on the outcome. Furthermore, the newly proposed OKN live-detection was verified against an offline analysis and an expert-observer judgement. The OKN-based CS was measured for six spatial frequencies at normal vision and three levels of defocus using spherical convex lenses.
RESULTS
The newly proposed OKN live-detection method showed a sufficient detection performance for implementation of adaptive procedures, and the detection rate is similar or better compared to offline detection methods. Spatial frequency and defocus had a significant effect on the OKN-based CS (P < 0.0001 for both).
CONCLUSIONS
The current study presents a novel method to measure motion CS in an automated way, combining the real-time detection of OKN and an adaptive psychometric procedure. Furthermore, the known effect of defocus on CS was successfully replicated with the newly developed tool.
TRANSLATIONAL RELEVANCE
OKN-based CS is a novel approach to assess spatial vision, which is sensitive to subtle effects of defocus, allowing use with nonverbal patients and infants. Furthermore, the newly developed tool may improve the performance of such measurements.
Topics: Contrast Sensitivity; Humans; Nystagmus, Optokinetic; Vision Disorders; Vision Tests; Vision, Ocular
PubMed: 34614164
DOI: 10.1167/tvst.10.12.12 -
Academic Radiology Sep 2022To assess the magnitude and determinants of computer vision syndrome (CVS) among radiologists in Saudi Arabia using a reliable and validated survey instrument.
RATIONALE AND OBJECTIVES
To assess the magnitude and determinants of computer vision syndrome (CVS) among radiologists in Saudi Arabia using a reliable and validated survey instrument.
MATERIALS AND METHODS
This nationwide cross-sectional web-based survey took place in April 2021 and included all radiologists and radiology residents residing practicing in Saudi Arabia. We used the reliable and validated CVS questionnaire. Univariate and multivariate analyses were carried out using nonparametric methods. The CVS score was correlated with different demographic- and health-related variables. The Mann-Whitney U test and Kruskal-Wallis test were used to determine if there was a statistically significant difference between subgroups.
RESULTS
The survey was completed by 416 participants. The prevalence of CVS was 65.4% (95% CI: 60.8-70.0). The median CVS score was 7.5 (interquartile range: 4.0; 12.0). Mild CVS was observed in 188 participants (69.1%), moderate CVS was observed in 69 (25.4%), and severe CVS was observed in 15 (5.5%). The most common symptoms perceived by participants were headache (72.1%), dryness (70.7%), burning (63.7%), blurred vision (56.3%), and increased sensitivity to light (55.5%). Multinomial regression analysis suggested that female sex (p < 0.001), work as a general radiologist (p = 0.05), and the use of eyeglasses (p = 0.001) were significant predictors of CVS.
CONCLUSION
The prevalence of CVS among radiologists in our study was high. Local and international societies need to establish and implement legislative and preventive measures to ensure the safety and ocular and visual health of radiologists.
Topics: Computers; Cross-Sectional Studies; Female; Humans; Radiologists; Saudi Arabia; Syndrome
PubMed: 34836777
DOI: 10.1016/j.acra.2021.10.023 -
Journal of Medical Case Reports Sep 2023Myasthenia gravis is an autoimmune condition affecting the neuromuscular junction and causing muscle weakness along with fatigue (myasthenia). When the clinical...
BACKGROUND
Myasthenia gravis is an autoimmune condition affecting the neuromuscular junction and causing muscle weakness along with fatigue (myasthenia). When the clinical manifestations of myasthenia gravis are isolated to the eye muscles, only causing weak eye movements, it is referred to as ocular myasthenia gravis, which can mimic a 1 and ½ syndrome.
CASE PRESENTATION
An African-American female in her fifties with past medical history of hypertension presented to our outpatient clinic with complaints of blurred vision for two weeks. Her symptoms were associated with facial discomfort and a generalized headache. On physical examination upon her initial presentation, there was demonstratable swelling of the left upper eyelid with drooping. Her extraocular movements revealed defects with the abduction and adduction of the right eye, and the left eye would not adduct, although the outward movement was normal. The left eye failed to lift/elevate completely when looking upwards, a pseudo 1 and ½ syndrome. A positive Cogan lid twitch was also noticed. Imaging of the brain and orbit ruled out central causes. Diagnosis of ocular myasthenia gravis was made in accordance with positive anti-acetylcholine receptor antibodies. With 120 mg pyridostigmine oral dose, the patient experienced improvement subjectively and objectively, and the patient was discharged on oral pyridostigmine and prednisone. Six months later, with prednisone having been tapered off, the patient developed a myasthenic crisis and was treated with plasmapheresis and intravenous immunoglobulins. After recovering from the myasthenic crisis, efgartigimod infusions were instituted, which helped our patient restore normal life.
CONCLUSION
Our patient who presented with "blurred vision" was discovered to have binocular diplopia due to significant dysconjugate eye movements. After diligently ruling out central etiologies, we concluded that her presentation was due to a peripheral etiology. Her serologies and her presentation helped confirm a diagnosis of ocular myasthenia gravis. Also, as in most cases, our patient also progressed to develop generalized myasthenia gravis while on pyridostigmine. Efgartigimod infusions instituted after our patient recovered from a myasthenic crisis have helped her restore a normal life.
Topics: Female; Humans; Diplopia; Pyridostigmine Bromide; Prednisone; Vision Disorders; Myasthenia Gravis; Muscle Weakness
PubMed: 37679826
DOI: 10.1186/s13256-023-04089-4 -
Iranian Journal of Parasitology 2022Ocular toxocariasis in humans is caused by infection with larvae of species, which are common ascarid roundworms of mammals, kept in close proximity to human. Four...
Ocular toxocariasis in humans is caused by infection with larvae of species, which are common ascarid roundworms of mammals, kept in close proximity to human. Four cases with a history of contact with dogs and cats and blurred vision and visual impairment over periods of variable duration were examined. We screened patients diagnosed with ocular larva migrans syndrome between March and June 2021 at the Ophthalmology clinics affiliated with Alborz University of Medical Sciences, Karaj, Iran. Detailed demographics, clinical characteristics, and fundus photography were recorded. Anti- antibodies in the sera and vitreous fluid detected by ELIZA. Complete recovery in all four patients was achieved following treatment with oral albendazole. The diagnosis of ocular toxocariasis can be challenging, because both the condition is relatively uncommon and its presentation varies from patient to patient. There are lots of differential diagnoses like retinoblastoma, therefore correct, quick diagnosis, and treatment is very important.
PubMed: 36046564
DOI: 10.18502/ijpa.v17i1.9034 -
Industrial Health 2016Various amines, such as triethylamine and N,N-dimethylethylamine, have been reported to cause glaucopsia in workers employed in epoxy, foundry, and polyurethane foam... (Review)
Review
Various amines, such as triethylamine and N,N-dimethylethylamine, have been reported to cause glaucopsia in workers employed in epoxy, foundry, and polyurethane foam industries. This symptom has been related to corneal edema and vesicular collection of fluid within the corneal subepithelial cells. Exposure to amine vapors for 30 min to several hours leads to blurring of vision, a blue-grey appearance of objects, and halos around lights, that are probably reversible. Concentration-effect relationships have been established. The visual disturbance is considered a nuisance, as it could cause onsite accidents, impair work efficiency, and create difficulties in driving back home. Occupational exposure limits have been established for some amines, but there is shortage of criteria. Volatility factors, such as vapor pressure, should be considered in industrial settings to prevent human ocular risks, while trying to reduce levels of hazardous amines in the atmosphere.
Topics: Air Pollutants, Occupational; Amines; Corneal Edema; Humans; Metallurgy; Occupational Exposure; Polyurethanes; Vision Disorders
PubMed: 26538000
DOI: 10.2486/indhealth.2015-0071 -
Australian Journal of General Practice Aug 2019Ocular dysfunction, including eye movement defects, has been documented in up to 69% of patients with concussion. However, standard sports-related concussion assessment...
BACKGROUND
Ocular dysfunction, including eye movement defects, has been documented in up to 69% of patients with concussion. However, standard sports-related concussion assessment protocols do not typically include any clinical examination of the ocular system.
OBJECTIVE
The aim of this article is to inform general practitioners (GPs) about ocular defects associated with concussion, identify test procedures and highlight the important role of GPs within the concussion paradigm.
DISCUSSION
Ocular dysfunction that commonly occurs with concussion includes abnormalities of accommodation, convergence, saccades and smooth pursuits. This may cause blurred vision, double vision, ocular pain and difficulty with close work. Symptoms can severely affect daily work, school or play activities. Patients complaining of extended ocular symptoms following concussion should be referred to an ophthalmologist for a complete ocular assessment.
Topics: Accommodation, Ocular; Brain Concussion; Humans; Oculomotor Muscles; Physical Examination; Saccades; Vision Disorders
PubMed: 31370123
DOI: 10.31128/AJGP-03-19-4876 -
Medical Journal, Armed Forces India Jul 2016Computer and visual display terminals have become an essential part of modern lifestyle. The use of these devices has made our life simple in household work as well as... (Review)
Review
Computer and visual display terminals have become an essential part of modern lifestyle. The use of these devices has made our life simple in household work as well as in offices. However the prolonged use of these devices is not without any complication. Computer and visual display terminals syndrome is a constellation of symptoms ocular as well as extraocular associated with prolonged use of visual display terminals. This syndrome is gaining importance in this modern era because of the widespread use of technologies in day-to-day life. It is associated with asthenopic symptoms, visual blurring, dry eyes, musculoskeletal symptoms such as neck pain, back pain, shoulder pain, carpal tunnel syndrome, psychosocial factors, venous thromboembolism, shoulder tendonitis, and elbow epicondylitis. Proper identification of symptoms and causative factors are necessary for the accurate diagnosis and management. This article focuses on the various aspects of the computer vision display terminals syndrome described in the previous literature. Further research is needed for the better understanding of the complex pathophysiology and management.
PubMed: 27546968
DOI: 10.1016/j.mjafi.2016.03.016