Abnormal Stereopsis Research Articles

Refractive error and abnormal stereopsis association with road traffic accidents in Saudi Arabian truck drivers.

To investigate the visual functions of truck drivers of the Kingdom of Saudi Arabia (KSA) in the region of Qassim and Dammam and to see if is there any association between these visual functions and self-reported road traffic accidents (RTA). It is a cross-sectional, descriptive study. LogMAR visual acuity, refractive error, color vision, stereopsis, and confrontation visual fields were measured in 300 truck drivers in the Qassim and Dammam regions of KSA. Driving-related history and incidence of RTA from the past 3 years, systemic history, and general eye compliance history were collected through a self-reporting questionnaire. Among 300 truck drivers examined, 54 (18.4%) subjects have a refractive error, 14 (4.7%) subjects have color vision deficiency, 37 (12.2%) subjects have abnormal stereo acuity, and none of them have confrontation visual field defect. RTA was reported in 25 (8.3%) subjects. The current study has found RTA is significantly associated with refractive error (P = 0.01) and abnormal stereopsis (P < 0.01). Systemic history revealed that 11% of the subjects had diabetes mellitus. The current study is the first to report on the visual functions of KSA truck drivers. Hence, the current study has found a significant association between visual functions and RTA among truck drivers, we recommend a comprehensive examination need to be part of issuing driver's licenses in KSA. More studies with larger samples from different regions of KSA are needed to extrapolate these findings.

Association between stereoacuity and simulated clinical performance among dental students: an exploratory investigation.

Dentistry is a profession that requires a high level of the hand-eye coordination. Although considerable attention has been put on dental students' manual dexterity, little emphasis was made on students' visual competency as a variable influencing their competency. In this study, we aimed to assess the association between dental students' stereopsis and their pre-clinical performance. Dental students (n=49) were required to perform the porcelain-fused-to-crown preparation for a lower first molar and an upper central incisor plastic teeth mounted on phantom heads. Performance was assessed by two faculty members based on two rubrics, which collectively included 11 assessment criteria. Afterward, students undertook a stereoacuity test using Randot stereotest. Stereopsis values greater than 40 arc/s were considered abnormal. A significant negative correlation was seen between stereopsis scores and students' grades for the upper incisor (p<0.01), but not for the lower molar. An association was also seen between abnormal stereopsis and students' poor performance in preparing the finish line of the incisor tooth (p=0.024). Abnormal stereopsis can impact dental students' performance, particularly when preparing teeth indirectly using a dental mirror. Dental educators should give attention to students' stereoacuity, in a manner similar to that given to students' manual dexterity.

Sufficiency of the BOT-2 short form to screen motor competency in preschool children with strabismus.

Strabismus is one of the most common visual disorders in children, with a reported prevalence of 2.48% in preschoolers. Additionally, up to 89.9% of preschool children with strabismus do not have normal stereopsis. Whether this lack of normal stereopsis affects the motor competency of preschool children with strabismus is unknown. The Bruininks-Oseretsky Test of Motor Proficiency Second Edition short form (BOT-2 SF) can be a useful tool for screening; however, its sufficiency as a diagnostic tool for children with various disorders is controversial. The aims of this study were thus to examine motor competency in preschool children with strabismus by using the BOT-2 and to evaluate the usefulness of the BOT-2 SF to identify those at risk for motor competency issues. Forty preschool children (aged 5-7 years) with strabismus were recruited, all of whom had abnormal stereopsis. The BOT-2 complete form (CF) was administered to all children. The BOT-2 CF was administered to all children. The scores of the BOT-2 SF were extracted from the relevant items of the BOT-2 CF for further analysis. The prevalence of children with strabismus who had below average performance in the composites of "Fine Manual Control", "Manual Coordination","Body Coordination", and "Strength and Agility" were 15%, 70%, 32.5%, and 5%, respectively, on the BOT-2 CF. Compared with these results, the sensitivity of the BOT-2 SF was 33.33% (95% CI = 7.49%-70.07%) and the specificity was 100% (95% CI = 88.78%-100%). Preschool children with strabismus had a high prevalence of impaired motor competency, especially in fine motor competency. The BOT-2 SF was not as sensitive in identifying motor difficulties in preschool children with strabismus. Therefore, the BOT-2 CF is recommended for evaluating motor proficiency in preschool children with strabismus.

Fixational eye movements and visual functions in amblyopia

Amblyopic patients have a constellation of visual function deficits including reduced visual acuity and contrast sensitivity, abnormal stereopsis, and increased fixation instability of fellow and amblyopic eye. The fixation instability arises from presence of nystagmus and altered physiologic fixation eye movements (FEMs). The purpose of the study is to examine the effects of presence of nystagmus on binocular and monocular functions of the fellow and amblyopic eye.

Clarifying the effect of refractive errors and stereopsis on traumatic dental injuries in childhood.

Visual acuity and stereopsis both play an important role in developing posture and balance in children. The aim of this study was to investigate whether children with traumatic dental injuries (TDI) have abnormal stereopsis, due to a reduction in visual acuity, compared to children with good dental health. A total of 140 participants (75 with traumatic dental injuries resulting from falls and crashes, and 65 age-matched controls without dental trauma) were enrolled in this prospective, cross-sectional study. The participants underwent complete dental and ophthalmologic examinations. After the ophthalmologic examination, the stereo acuities were assessed by a Titmus stereo test at 40cm. Titmus test scores were significantly worse in the TDI group (mean score 252.46±629.12seconds of arc) compared to the control group (mean score 56±27.39seconds of arc) (P<.05). The percentage of subjects with abnormal Titmus test scores was higher in the TDI group (28%) than in the control group (3.1%). The mean anisometropia value was 3.03±2.37 D and 0.55±0.41 D in the TDI group and the control group, respectively (P<.001). The severity of anisometropia correlated with the degree of stereopsis (r=.83, P<.01). The presence of abnormal stereopsis may lead to postural instability which can lead to traumatic dental injuries. The prevalence of abnormal stereopsis in children with TDI was higher than in children with good binocular vision and stereopsis.

Evaluation of visual deficits in different types of amblyopia at rural tertiary setup

Introduction: Amblyopia is defined as unilateral or bilateral dimness of vision caused by form vision deprivation and/or abnormal binocular interaction, is the most common cause of preventable monocular blindness and nearly all-amblyopic visual loss is reversible with timely detection and appropriate intervention. The conditions leading to functional amblyopia are well known and include strabismus, anisometropia, astigmatism, hypermetropia, cataract, and other forms of stimulus deprivation. Material &Method: The present hospital based cross sectional study has been carried out in Department of Ophthalmology at Acharya Vinoba Bhave Rural Hospital attached to Jawaharlal Nehru Medical College, Sawangi (Meghe), Wardha, a constituent of Datta Meghe Institute of Medical Sciences (Deemed University), Nagpur during the period from September 2012 to August 2014. 100 eyes of 91 patients having Amblyopia or amblyogenic factor (strabismus or anisometropia) in outdoor and indoor patients were selected for the study.All patients were enrolled in the study after due consideration of various exclusion criteria for selection. Results: The mean age of the study population was 15.00 ± 5.74 years, range 6-30 year. The present study found amblyopia to be more common in males than females. All the patients included in this study had one of the diagnoses from strabismic amblyopia, anisometropic amblyopia, isometropic amblyopia and stimulus deprivation amblyopia. Out of these maximum number of eyes was found to have anisometropic amblyopia (37%) and strabismic amblyopia (36%). Maximum numbers of eyes were seen with0.9-1.0 visual acuity (in LogMAR units).It was found to be highly significant in almost all except between strabismic and stimulus deprivation amblyopia; and between anisometropic and isometropic amblyopia.The present study found colour vision to be normal in all the various types of amblyopia. Most eyes were found to have hyperopic astigmatism/hyperopia (56%) followed by myopic astigmatism/myopia (31%) while mixed astigmatism was least common (13%). Maximum numbers of eyes were seen with 0.00 – 0.15 contrast sensitivity. 43% had normal while 57% had abnormal stereopsis. Conclusion: Amblyopia and associated strabismus can have devastating psychosocial and economic fallouts. Knowledge about the sub-types of amblyopia is important because the clinical presentations, management and outcomes of these different types are different. The data in the present study could be used to enhance screening efforts in an organized manner in those health-care groups which come in regular contact with infants and young children.

Abnormal stereopsis and reduced retinal sensitivity in patients with retinitis pigmentosa

The aim of the study was to evaluate retinal sensitivity and stereoacuity (SA) in retinitis pigmentosa (RP) patients. Twenty-six patients with RP were examined, mean age 36.4 ± 7.21 (SD)years old and best corrected visual acuity better than 0.15 logMAR. The control group (CG) included 25 healthy subjects matching the RP group by age and sex. Every patient and healthy control underwent a complete ophthalmologic examination: Titmus, Lang, TNO stereotests and microperimetry (MP-1) (Nidek Technologies). Results were subjected to factor analysis using Varimax rotation, and p values < 0.05 were considered statistically significant. With the Titmus stereotest, the mean SA was 136.52 ± 26.5(SD)arcsec in the RP group and 67.2 ± 11.5(SD) in CG; Lang SA was 391.39 ± 53.72(SD) in RP group and 1150 ± 33.4(SD) in CG; and TNO SA was 69.3 ± 14.39(SD) in the RP group and 15.97 ± 3.7(SD) in CG. Factor analysis showed significant correlation between visual acuity and SA (p = 0.0001) in RP group. MP-1 demonstrated that in RP patients, inter-ocular difference in retinal sensitivity and fixation stability was related to anomalous stereopsis (p values < 0.05). Progressive RP degeneration in the cone system could determine a significant impairment in the binocular vision due to anomalous inter-ocular retinal sensitivity and incomplete Panum's area utilization, causing an incongruent retinal localization. These findings suggest a possible reason why RP patients with a central retinal involvement, even if minimal, perceive a damaged stereoscopic perception that produces a severe disability.

Visual dysfunction in patients with idiopathic rapid eye movement sleep behavior disorder

ObjectiveVisual dysfunction is a common feature in α-synucleiopathies but rarely assessed in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD). The current study is set to investigate the comprehensive visual function in iRBD as compared to patients of Parkinson’s disease (PD) with RBD. MethodsEighty-three iRBD subjects diagnosed with polysomnograph (PSG), 52 early PD patients (Hoehn-Yahr stages<3) with RBD symptom prior to onset of motor symptoms and 79 healthy controls without RBD diagnosed based on RBD Questionnaire-Hong Kong (RBDQ-HK) were enrolled in this study. Visual function including color discrimination, stereopsis function, visual illusion (VI) or hallucination (VH) were assessed in addition to UPDRS, Purdue Pegboard test (PPT) and cognitive tests. ResultsAbnormal color discrimination and stereopsis were presented significantly higher in both iRBD and PD patients as compared to controls and more severe in PD than in iRBD. Color discrimination was decreased in all four color in PD patients but not green color in iRBD subjects. Stereopsis test was abnormal in both iRBD and PD, but the proportion of subjects with abnormal stereopsis was significantly higher in PD patients (69.6% vs 42%). Similar number of subjects with iRBD and PD were presented with illusion but only PD patients reported more hallucination. Changes of visual function were associated with age and cognition in both iRBD and PD subjects but was also affected independently by disease duration and clinical stage or fine motor function in PD. In addition, decreased fine motor function demonstrated by PPT was also observed in some iRBD subjects. ConclusionOur results demonstrated comprehensively that visual dysfunction was present in iRBD subjects similar but in a less degree of severity to PD patients, and associated with age, cognition and motor deficit. Whether or not it can be useful in predicting iRBD conversion to PD warrants further investigation.

Postural sway in patients with early Parkinson’s disease performing cognitive tasks while standing

ABSTRACTObjectives: We investigated postural sway in patients with early Parkinson’s disease (PD) to test the hypothesis that the postural control system was affected already at an early stage of PD. Moreover, we identified cases of dysfunction of stereopsis in PD patients.Methods: We examined 23 patients with early PD and 23 healthy, sex- and age-matched control subjects. Postural sway was measured with an accelerometer at the center of mass at the lower spine. Subjects were asked to stand quietly for 30 s under two usual conditions (eyes open and eyes closed) and two dual tasks conditions (eyes open with dual task, eyes closed with dual task). Stereopsis was assessed using the Titmus fly test.Results: In the usual conditions, no differences were found between the control group and PD group. With increasing task difficulty, PD patients showed an increase of RMS values of sway acceleration, compared to control subjects. These differences reached significance during cognitive task performance. PD patients showed larger JERK values with increasing difficulty of the sway task which also reached significance during cognitive task performance. Relative to controls, PD patients showed decreased stereopsis function. But, there were no statistically significant correlations between log seconds of arc of the Titmus test and JERK, even during cognitive task performance.Conclusion: Our results indicate that patients with early PD have subtle signs of postural instability when their attention is diverted or reduced. In addition, deficits of stereopsis may be common in early PD patients. StAbbreviations: ACC: Accelerometers; ANOVA: Analysis of variance; AP: Antero-posterior; COP: Center of pressure; EC: Eyes closed; ECDT: eyes closed with dual task; EO: Eyes open; EODT: Eyes open with dual task; GDS: Geriatric depression scale; JERK: Jerkiness of sway; ML: Medio-lateral; MMSE: Mini mental state examination; MoCA: Montreal cognitive assessment; PD: Parkinson’s disease; PDAbS: PD Patients with abnormal stereopsis; PDNrS: PD Patients with normal stereopsis; PIGD: Postural instability and gait disorder; RMS: Root mean square; UPDRS: Unified Parkinson’s disease rating scale.

Ocular Manifestations of Noonan Syndrome: A Prospective Clinical and Genetic Study of 25 Patients

To determine the full spectrum of ocular manifestations in patients with Noonan syndrome (NS). Prospective cross-sectional clinical and genetic study in a tertiary referral center. Twenty-five patients with NS (mean age, 14 years; range, 8 months-25 years) clinically diagnosed by validated criteria. All patients were examined by the same team following a detailed study protocol. Genetic analyses were performed in 23 patients. Ocular abnormalities of vision and refraction, external ocular features, ocular position and motility, anterior segment, posterior segment, and intraocular pressure. Ocular features of vision and refraction were amblyopia (32%), myopia (40%), and astigmatism (52%). External ocular features were epicanthic folds (84%), hypertelorism (68%), ptosis (56%), high upper eyelid crease (64%), lower eyelid retraction (60%), abnormal upward slanting palpebral fissures (36%), downward slanting palpebral fissures (32%), and lagophthalmos (28%). Orthoptic abnormalities included strabismus (40%), abnormal stereopsis (44%), and limited ocular motility (40%). Anterior segment abnormalities included prominent corneal nerves (72%) and posterior embryotoxon (32%). Additional ocular features were found, including nonglaucomatous optic disc excavation (20%), relatively low (<10 mmHg) intraocular pressure (22%), and optic nerve hypoplasia (4%). Mutations were established in 22 patients: 19 PTPN11 mutations (76%), 1 SOS1 mutation, 1 BRAF mutation, and 1 KRAS mutation. The patient with the highest number of prominent corneal nerves had an SOS1 mutation. The patient with the lowest visual acuity, associated with bilateral optic nerve hypoplasia, had a BRAF mutation. Patients with severe ptosis and nearly total absence of levator muscle function had PTPN11 mutations. All patients showed at least 3 ocular features (range, 3-13; mean, 7), including at least 1 external ocular feature in more than 95% of the patients. Noonan syndrome is a clinical diagnosis with multiple genetic bases associated with an extensive variety of congenital ocular abnormalities. Ocular features of NS are characterized by 1 or more developmental anomalies of the eyelids (involving the position, opening, and closure) associated with various other ocular abnormalities in childhood, including amblyopia, myopia, astigmatism, strabismus, limited ocular motility, prominent corneal nerves, and posterior embryotoxon.

Oculo-Visual Dysfunction in Parkinson's Disease.

This review describes the oculo-visual problems likely to be encountered in Parkinson’s disease (PD) with special reference to three questions: (1) are there visual symptoms characteristic of the prodromal phase of PD, (2) is PD dementia associated with specific visual changes, and (3) can visual symptoms help in the differential diagnosis of the parkinsonian syndromes, viz. PD, progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and corticobasal degeneration (CBD)? Oculo-visual dysfunction in PD can involve visual acuity, dynamic contrast sensitivity, colour discrimination, pupil reactivity, eye movement, motion perception, and visual processing speeds. In addition, disturbance of visuo-spatial orientation, facial recognition problems, and chronic visual hallucinations may be present. Prodromal features of PD may include autonomic system dysfunction potentially affecting pupil reactivity, abnormal colour vision, abnormal stereopsis associated with postural instability, defects in smooth pursuit eye movements, and deficits in visuo-motor adaptation, especially when accompanied by idiopathic rapid eye movement (REM) sleep behaviour disorder. PD dementia is associated with the exacerbation of many oculo-visual problems but those involving eye movements, visuo-spatial function, and visual hallucinations are most characteristic. Useful diagnostic features in differentiating the parkinsonian symptoms are the presence of visual hallucinations, visuo-spatial problems, and variation in saccadic eye movement dysfunction.

Visual function among commercial vehicle drivers in the central region of Ghana

AimTo determine the relationship between some visual functions: colour vision defects, abnormal stereopsis, visual acuity and the occurrence of road traffic accident (RTAs) among commercial vehicle drivers in the central region of Ghana, and to assess their knowledge of these anomalies. MethodA descriptive cross-sectional study employing a multi-stage random sampling approach was conducted in the major commercial towns within the central region of Ghana. Participants were taken through a comprehensive eye examination after the administration of a structured questionnaire. Results520 male commercial vehicle drivers were enrolled for this study with a mean age of 39.23years ±10.96 years and mean visual acuity of 0.02±0.08 logMAR. Protans were more likely to be involved in RTAs (χ2=6.194, p=0.034). However, there was no statistically significant association between abnormal stereopsis (OR=0.89 95% CI: 0.44–1.80, p=0.56), poor vision due to refractive error (χ2=3.090, p=0.388) and the occurrence of RTAs. While 86.9% were aware of abnormal stereopsis, only 45% were aware of colour vision defects. There was a statistically significant association between stereopsis anomaly and colour vision defect (r=0.371, p<0.005). ConclusionThe study found an association between protanopia and RTAs but none between stereopsis anomalies, refractive errors and the occurrence of RTAs. Drivers were less knowledgeable on colour vision defects as compared to stereopsis anomalies.

Many Faces of Parkinson's Disease: Non-Motor Symptoms of Parkinson's Disease.

Parkinson’s disease (PD) is a multi-systemic disorder that is characterized by a combination of motor and non-motor symptoms (NMS). The dopaminergic neurodegeneration of PD is involved in the genesis of NMS, but other conditions and side effects of levodopa are also associated with NMS. NMS can develop at all stage of PD and rapid eyeball movement sleep behavior disorder (RBD), constipation, depression, and olfactory dysfunction are considered prodromal signs of PD. Many NMS related with motor deficits and cognitive dysfunction. Some NMS including olfactory dysfunction, RBD and abnormal stereopsis are associated with presence of other NMS of PD. In addition, several NMS can be helpful to differentiate between idiopathic PD and other parkinsonian disorders. Early recognition and management of NMS in PD patients is important for preserving quality of life.

Nonmotor Symptoms and Cognitive Decline in de novo Parkinson's Disease.

Cognitive impairments are common in Parkinson's disease (PD). Despite its clinical importance, the development of dementia is still difficult to predict. In this study, we investigated the possible associations between non-motor symptoms and the risk of developing dementia within a 2-year observation period in PD. A total of 80 patients with PD participated in this study. Nonmotor symptoms (the Nonmotor Symptoms Questionnaire), PD status (Unified Parkinson's Disease Rating Scale), depression (Geriatric d Depression Scale or Montgomery-Asberg Depression Scale), stereopsis and severity of nonmotor symptoms (Non-motor symptoms scale) were assessed. Global cognitive function (Mini-Mental State Examination) were evaluated at baseline and 2 years later. Presence of depression, vivid dreaming, REM sleep behavior disorders, hyposmia, abnormal stereopsis, non-smoking and postural instability/ gait disturbance phenotype were associated with a significantly more rapid decline of Mini-Mental State Examination. Logistic regression analyses demonstrated that depression (odds ratio=13.895), abnormal stereopsis (odds ratio=10.729), vivid dreaming (odds ratio=4.16), REM sleep behavior disorders (odds ratio=5.353) and hyposmia (odds ratio=4.911) were significant independent predictors of dementia risk within 2 years. Postural instability/ gait disturbance phenotype and age >62 years were also independent predictors of dementia risk (odd ratio=38.333, odds ratio=10.625). We suggest that depression, vivid dreaming, REM sleep behavior disorders, hyposmia and abnormal stereopsis are closely associated with cognitive decline, and that presence of these nonmotor symptoms predict the subsequent development of Parkinson's disease dementia.

Stereopsis impairment is associated with decreased color perception and worse motor performance in Parkinson’s disease

BackgroundWe conducted this study is to investigate the correlation between stereopsis dysfunction and color perception, as well as whether stereopsis impairment is associated with motor dysfunction in patients with Parkinson’s disease (PD).MethodOur present study included 45 PD patients and 50 non-PD control patients attending the Movement Disorder Center at Xuanwu Hospital Capital Medical University in Beijing from July 2011 to November 2011. Neurologic evaluations and visual function assessments were conducted, and the results between two groups of patients were compared.ResultsWe found that the total error scores (TESs) and partial error scores (PESs) for red, green, blue and purple were all significantly higher in PD patients than in control patients. The limited grade on the FLY Stereo Acuity Test with LEA Symbols was significantly lower in PD patients than in control patients (P = 0.0001), whereas the percentage of abnormal stereopsis in PD patients was significantly higher than in control patients (42.2% vs. 12%; P = 0.001). Multiple linear regression analysis showed that PD patients with higher Hoehn and Yahr Scale stage, and those with decreased stereopsis had higher Unified Parkinson’s Disease Rating Scale (UPDRS) motor scores and worse motor function. Furthermore, our study demonstrates that the UPDRS motor scores and total average number of the Purdue Pegboard Test scores of PD patients were significantly improved when they had taken their medications, and the TESs and PESs for green were lower in when they were off their medications.ConclusionOur results provide more information on the underlying mechanisms of vision, motor and stereopsis impairments in PD patients.

Postural sway in idiopathic rapid eye movement sleep behavior disorder: A potential marker of prodromal Parkinson׳s disease

There is compelling evidence that postural instability occurs at very early clinical stages of Parkinson׳s disease (PD), making it tempting to speculate that changes in postural sway may even occur at a prodromal phase. Studies estimate that approximately half of patients with idiopathic rapid eye movement (REM) sleep behavior disorder (RBD) will eventually develop PD, so RBD may be an indicator of prodromal PD. This study was undertaken to investigate postural sway and its relation to stereopsis function in patients with RBD. We examined 24 patients with polysomnography-confirmed RBD and 23 healthy, sex-and age-matched control subjects. Postural sway was measured with an accelerometer at the center of mass at the lower spine. Subjects were asked to stand quietly for 30s under two usual conditions (eyes open and eyes closed) and three challenging conditions (eyes open with dual task, eyes closed with dual task, and tandem standing). Stereopsis was assessed using the Titmus fly test. RBD patients showed an increased variability of trunk acceleration and a decrease of smoothness of sway, compared to control subjects. These differences reached significance in the challenging conditions. RBD patients demonstrated significant impairment in stereopsis. There were statistically significant correlations between log seconds of arc of the Titmus test and some sway parameters within the RBD group. RBD patients with abnormal stereopsis showed a significant increase of JERK values compared to patients with normal stereopsis in the challenging conditions. Our results indicate that idiopathic RBD patients, especially with abnormal stereopsis, have subtle signs of postural instability under challenging conditions. Postural sway performance may serve as a biological marker for prodromal PD.

Influence of stereopsis and abnormal binocular vision on ocular and systemic discomfort while watching 3D television

To evaluate the degree of three-dimensional (3D) perception and ocular and systemic discomfort in patients with abnormal binocular vision (ABV), and their relationship to stereoacuity while watching a 3D television (TV). Patients with strabismus, amblyopia, or anisometropia older than 9 years were recruited for the ABV group (98 subjects). Normal volunteers were enrolled in the control group (32 subjects). Best-corrected visual acuity, refractive errors, angle of strabismus, and stereoacuity were measured. After watching 3D TV for 20 min, a survey was conducted to evaluate the degree of 3D perception, and ocular and systemic discomfort while watching 3D TV. One hundred and thirty subjects were enrolled in this study. The ABV group included 49 patients with strabismus, 22 with amblyopia, and 27 with anisometropia. The ABV group showed worse stereoacuity at near and distant fixation (P<0.001). Ocular and systemic discomfort was, however, not different between the two groups. Fifty-three subjects in the ABV group and all subjects in the control group showed good stereopsis (60 s of arc or better at near), and they reported more dizziness, headache, eye fatigue, and pain (P<0.05) than the other 45 subjects with decreased stereopsis. The subjects with good stereopsis in the ABV group felt more eye fatigue than those in the control group (P=0.031). The subjects with decreased stereopsis showed more difficulty with 3D perception (P<0.001). The subjects with abnormal stereopsis showed decreased 3D perception while watching 3D TV. However, ocular and systemic discomfort was more closely related to better stereopsis.

Stereopsis and extrastriate cortical atrophy in Parkinson’s disease

Among the various visuospatial dysfunctions, deficits of stereopsis could be associated with Parkinson's disease. We examined differences in regional gray matter volume between Parkinson's disease patients with normal stereopsis and with abnormal stereopsis to delineate the possible anatomical correlate of stereopsis. Stereopsis was assessed using the Titmus test in 35 drug-naive patients with Parkinson's disease. Voxel-based morphometry was utilized to assess regionally specific differences in gray matter volume between 16 patients with normal stereopsis and 19 patients with abnormal stereopsis. Patients with abnormal stereopsis had a significant gray matter volume reduction in the right extrastriate visual cortex compared with patients with normal stereopsis (P<0.05, corrected for multiple comparisons). Voxel values extracted from the significant cluster in group comparison were negatively correlated with log seconds of arc of the Titmus test (Spearman correlation, P<0.001). Our results suggest that deficits of stereopsis are associated with nondominant extrastriate cortical atrophy and that abnormal stereopsis implicates the cortical visual dysfunction as part of the nonmotor symptoms in Parkinson's disease.

The effect of sensory uncertainty due to amblyopia (lazy eye) on the planning and execution of visually-guided 3D reaching movements.

BackgroundImpairment of spatiotemporal visual processing in amblyopia has been studied extensively, but its effects on visuomotor tasks have rarely been examined. Here, we investigate how visual deficits in amblyopia affect motor planning and online control of visually-guided, unconstrained reaching movements.MethodsThirteen patients with mild amblyopia, 13 with severe amblyopia and 13 visually-normal participants were recruited. Participants reached and touched a visual target during binocular and monocular viewing. Motor planning was assessed by examining spatial variability of the trajectory at 50–100 ms after movement onset. Online control was assessed by examining the endpoint variability and by calculating the coefficient of determination (R2) which correlates the spatial position of the limb during the movement to endpoint position.ResultsPatients with amblyopia had reduced precision of the motor plan in all viewing conditions as evidenced by increased variability of the reach early in the trajectory. Endpoint precision was comparable between patients with mild amblyopia and control participants. Patients with severe amblyopia had reduced endpoint precision along azimuth and elevation during amblyopic eye viewing only, and along the depth axis in all viewing conditions. In addition, they had significantly higher R2 values at 70% of movement time along the elevation and depth axes during amblyopic eye viewing.ConclusionSensory uncertainty due to amblyopia leads to reduced precision of the motor plan. The ability to implement online corrections depends on the severity of the visual deficit, viewing condition, and the axis of the reaching movement. Patients with mild amblyopia used online control effectively to compensate for the reduced precision of the motor plan. In contrast, patients with severe amblyopia were not able to use online control as effectively to amend the limb trajectory especially along the depth axis, which could be due to their abnormal stereopsis.

Stereopsis in Drug Naïve Parkinson's Disease Patients

Motor deficits associated with Parkinson's disease (PD) have been well described, yet little attention has been paid to non-motor symptoms, especially cortical visual dysfunction. We investigated stereopsis, as well as the relationship between stereopsis and other cognitive function, in a sample of PD patients. We used Titmus stereotest plates for assessing stereopsis. Fifty-nine subjects (29 PD patients and 30 normal controls) were included in this study. The included patients underwent a neurological examination, clinical rating scale and neuropsychological tests. Drug naïve PD patients showed decreased stereopsis on the Titmus fly stereopsis test (Pearson χ2=23.80, p<0.001) compared to PD patients with normal stereopsis. The Hoehn-Yahr stages and Unified Parkinson's Disease Rating Scale motor scores were significantly higher in patients with PD with abnormal stereopsis than in patients with PD with normal stereopsis (p=0.026; p=0.046). The frequency of abnormal visual perception/constructive function was greater in patients with PD with abnormal stereopsis compared to patients with PD with normal stereopsis (Pearson χ2=5.11, p=0.024). These findings suggest that stereopsis deficits and visual perception/constructive dysfunction are common in de novo PD patients.