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PubMed1989

Monocular motion sensing, binocular motion perception.

The two-process account of motion perception and its binocular organization were addressed in experiments on apparent movement (AM) with three types of grating: sinusoidal; random bar width; and square-wave with missing fundamental (MF). Monocular MF gratings sampled four times per cycle of drift always appeared to move backwards. Here AM was unrelated to the spatial appearance of the pattern, and followed the motion of the dominant spatial frequency component (the third harmonic). We take this reversed AM to be characteristic of "short-range" motion sensors. It did not occur dichoptically, implying that the direction-selective mechanism of motion sensors is purely monocular. AM was seen with dichoptic presentation for all three types of grating. Performance improved with the length of the stimulus sequence, as predicted by probability summation. This result reconciles previous positive and negative findings on dichoptic AM. The perceived direction of dichoptic AM was consistent with polarity-selective matching of features over time (the "long-range process"). The most telling effect supporting feature-matching in dichoptic motion was that dichoptic MF motion reversed direction with a change in the visible features of the pattern (induced by changes in contrast and pulse duration); monocular apparent motion did not. Two routes from spatial frequency channels to the perception of object motion are discussed.

Contrast Sensitivity↗
PubMed1989

Spatial properties of disparity pooling in human stereo vision.

The spatial limits of disparity averaging were investigated using Julesz random dot stereograms with two different depth planes. Such stimuli could be perceived as two separate surfaces, one of which was seen through the transparent veil of the other, but under some conditions the depth of information provided by the two surfaces was pooled and the resulting surface was seen at the average of the local disparities. Two types of model are considered for disparity averaging. In the first, disparity averaging occurs as a consequence of attraction/repulsion effects in the disparity domain or as an interpolation process working on a dense depth map of the image. In the second, disparity averaging is seen as a consequence of monocular spatial filtering of the left and right eye images prior to binocular combination.

Depth Perception↗
PubMed1989

Manipulating stereopsis and vergence in an outdoor setting: moon, sky and horizon.

A simple stimulus generator has been constructed that permits a small illuminated target to be seen with variable inter-ocular disparity, when superimposed upon the binocular view of an outdoor landscape. This device was applied to several questions involving perception of size, distance and orientation, with the following results: (1) when the apparent distance to an "artificial moon", as perceived through stereopsis, is decreased by about 50-fold (from near horizon to about 60 m), its apparent size is reduced by only a miniscule amount (8% on average); hence, the moon illusion is probably not due to compensation--conscious or subconscious--for its apparent distance; (2) those changes in apparent size known as convergence micropsia vary as a function of the visual surround; for a vergence change of 1 deg, greater perceived change in size of a small target arises when a landscape is seen nearby than with empty sky as surround; (3) when a target is shown somewhat above the horizon against an empty sky, it must be viewed with divergence of the visual axes (image positions for "hyper-infinite" distance), in order to be perceived as vertically above objects on the skyline; this effect implies a strong backward tilt to the apparent vertical and probably reflects an attempt to "null out" the perceptual consequences of the convergence that typically occurs during downward saccades.

Depth Perception↗
PubMed1988

Perceptual asymmetries in left- and right-handers for cartoon and real faces.

We examined 40 left-handers and 40 right-handers on two free-vision tests of face processing. A chimeric face composed of a smiling half-face joined to either a neutral half-face (real faces) or a sad half-face (cartoon faces) and its mirror image were presented on each trial. Subjects judged which chimeric face looked happier, the one with the smile to the left or the one with the smile to the right. Right-handers, but not left-handers, had a highly significant leftward attentional bias, since chimeras with the smile to the left were judged happier than those with the smile to the right. The cartoon- and real-face tasks did not differ in the mean perceptual asymmetries they elicited. However, correlations between attentional-asymmetry scores for the two tasks, although high for both left- and right-handers, were significantly smaller than task reliabilities. Thus, the cartoon- and real-face tasks overlap to a major extent in the lateralized processes they measure, but to a lesser extent, they also index different lateralized processes.

Adult↗
PubMed1986

Age related changes in visual acuity.

Longitudinal visual acuity assessments of men, and cross-sectional assessments of men and women in the Baltimore Longitudinal Study of Aging are presented. The longitudinal data relate presenting far, uncorrected far, presenting near and uncorrected near visual acuities to age. The cross-sectional data relate presenting far acuity to age. The prevalence of cataract, glaucoma and retinal pathologies are reported for the longitudinal sample at the time of their last vision test. The effect of visual pathologies in general, and cataract in particular, upon presenting far visual acuity was examined. The longitudinal data are consistent with cross-sectional data from previously published reports. Older persons who were free from specific visual pathologies exhibited an age-related decline in presenting far acuity as did those with documented visual pathologies. Despite the demonstrated loss in acuity with age, the majority of persons maintain at least fair acuity (20/40 or better) into their 80's.

Adult↗
PubMed2004

Development of an instrument to assess vision-related quality of life in young children.

PURPOSE: Quality of life (QOL) instruments are increasingly utilized in ophthalmological research. Measuring vision-related QOL in young children is complicated by constantly evolving abilities related to normal growth and development. Our aim was to develop vision-related QOL instruments for children in different age ranges <==7 years, and to provide initial validation of these instruments. DESIGN: Cross-sectional study. METHODS SETTING: Multicenter. PATIENTS: 773 pediatric patients (age <==7 years) with a wide range of ophthalmological diagnoses. PROCEDURE: Questionnaire. A 61-item prototype instrument with a wide variety of items was applied to 403 consecutive patients. The usefulness of items was evaluated as a function of age in order to derive two age-group specific instruments and to find the age limit dividing the age groups. Thus, age-specific versions of a Children's Visual Function Questionnaire (CVFQ) were defined for ages <3 years and >/=3 years, and applied to a convenience sample of patients. OUTCOME: Subscale scores. Factor analysis helped identify underlying dimensions of the data, and corresponding subscales were defined. Validation was provided by examining the internal consistency reliability and by exploring the associations between scores and clinical characteristics. RESULTS: Subscales for General health, General vision, Competence, Personality, Family impact, and Treatment were defined, with internal consistency reliabilities ranging from 0.60 to 0.86. The association between subscales scores and age was weak, whereas strong correlations were found with the level of visual impairment and type of visual diagnosis. CONCLUSION: The CVFQ assesses the impact of visual impairment on children and their families, and is expected to become a useful tool for the pediatric vision research community.

Child↗
PubMed2004

Effect of blue staining of expandable hydrophilic intraocular lenses on contrast sensitivity and glare vision.

PURPOSE: To evaluate the effect of trypan blue staining of expandable hydrophilic acrylic intraocular lenses (IOLs) on contrast sensitivity and glare. SETTING: Department of Ophthalmology, Federal University, and Oculistas Associados, Rio de Janeiro, Brazil. METHODS: Phacoemulsification with expandable hydrophilic IOL implantation was performed in 19 eyes. Group 1 (stained group) consisted of 12 eyes with the IOL unintentionally stained by trypan blue 0.1% solution during surgery; Group 2 (unstained group) consisted of 7 eyes with IOLs that were not stained because trypan blue was not used during surgery. The eyes were examined postoperatively for Snellen best corrected visual acuity (BCVA), contrast sensitivity BCVA, and glare vision. The examiners were masked to whether the IOL was stained by trypan blue. Inclusion criteria included a BCVA of 20/30 or better 1 month postoperatively. Patients who had other ocular pathology or previous ocular surgery were excluded from the study. RESULTS: The mean postoperative BCVA was 20/24 in the stained group and 20/23 in the unstained group (P =.73). The mean contrast sensitivity visual acuity was 20/31 in the stained group and 20/26 in unstained group (P =.10). The mean glare visual acuity was 20/75 and 20/33, respectively (P =.03). CONCLUSIONS: Patients with expandable hydrophilic acrylic IOLs stained with trypan blue performed significantly worse on a glare vision test than patients whose IOLs were not stained. Cataract surgeons should avoid using trypan blue with this IOL type.

Acrylic Resins↗
PubMed2004

EEG and postural correlates of mild traumatic brain injury in athletes.

Mild traumatic brain injury (MTBI), or concussion, is one of the least understood injuries facing the neuroscience and sports medicine community today. The notion of transient dysfunction and rapid symptom resolution is misleading since symptom resolution is not indicative of injury resolution. Our working hypothesis is that there are residual postural and EEG abnormalities in concussed individuals that could be reliably assessed using appropriate research methodology. This paper presents combined postural and electroencephalographic (EEG) findings suggesting the persistent functional deficits in athletes suffering from MTBI. Twelve concussed athletes and twelve normal controls participated in the study. There was a decrease in EEG power in all bandwidths studied in concussed subjects, especially in standing postures. This was accompanied by sustained postural instability especially under the no vision testing condition. Overall, this study demonstrated the presence of long-term functional abnormalities in individuals suffering from mild traumatic brain injury.

Adolescent↗
PubMed2004

Prevalence and risk indicators of visual impairment and blindness in Latinos: the Los Angeles Latino Eye Study.

OBJECTIVE: To determine the age- and gender-specific prevalence and risk indicators of visual impairment and blindness in urban Latinos 40 years and older. DESIGN: Population-based cross-sectional study. PARTICIPANTS: Six thousand three hundred fifty-seven Latinos 40 years and older from 6 census tracts in Los Angeles, California. METHODS: Of the 6357 study participants, 6122 underwent a complete ophthalmologic examination at the clinical center, including measurement of best-corrected distance visual acuity (VA) using a standard Early Treatment Diabetic Retinopathy Study protocol. Age- and gender-specific prevalence of visual impairment and blindness were contrasted using Mantel-Haenszel procedures. Sociodemographic and clinical risk indicators of visual impairment were explored using stepwise logistic regression. MAIN OUTCOME MEASURES: Prevalence and odds ratios for risk indicators of visual impairment and blindness. RESULTS: The overall prevalence for visual impairment (best-corrected VA of <==20/40 in the better eye) was 3.0% (n = 182) (range, 0.9% [40-49 years]-27.8% [>/=80 years]). The overall prevalence for blindness (best-corrected VA of <==20/200 in the better eye) was 0.4% (n = 26) (range, 0.2% [40-49 years]-4.2% [>/=80 years]). Visual impairment increased with age (P<0.0001) and was greater in women (P = 0.02). Independent risk indicators (odds ratio [95% confidence interval]) for visual impairment were age 70-79 years (2.8 [1.3-5.8]) or >/=80 years (8.7 [3.9-19.6]), history of ocular disease (3.2 [2.1-4.8]), being unemployed (3.3 [1.7-6.3]), diabetes (2.2 [1.5-3.2]), and being separated/divorced (1.8 [1.0-3.1]) or widowed (2.8 [1.8-4.4]). Participants with >/=12 years of education (0.5 [0.3-0.8]) were less likely to be visually impaired. CONCLUSIONS: Rates of visual impairment and blindness in Latinos are high, especially in older individuals. Better education and employment are likely to decrease the burden of visual impairment in Latinos.

Adult↗
PubMed2006

Relation of visual function to retinal nerve fiber layer thickness in multiple sclerosis.

PURPOSE: To examine the relation of visual function to retinal nerve fiber layer (RNFL) thickness as a structural biomarker for axonal loss in multiple sclerosis (MS), and to compare RNFL thickness among MS eyes with a history of acute optic neuritis (MS ON eyes), MS eyes without an optic neuritis history (MS non-ON eyes), and disease-free control eyes. DESIGN: Cross-sectional study. PARTICIPANTS: Patients with MS (n = 90; 180 eyes) and disease-free controls (n = 36; 72 eyes). METHODS: Retinal never fiber layer thickness was measured using optical coherence tomography (OCT; fast RNFL thickness software protocol). Vision testing was performed for each eye and binocularly before OCT scanning using measures previously shown to capture dysfunction in MS patients: (1) low-contrast letter acuity (Sloan charts, 2.5% and 1.25% contrast levels at 2 m) and (2) contrast sensitivity (Pelli-Robson chart at 1 m). Visual acuity (retroilluminated Early Treatment Diabetic Retinopathy charts at 3.2 m) was also measured, and protocol refractions were performed. MAIN OUTCOME MEASURES: Retinal nerve fiber layer thickness measured by OCT, and visual function test results. RESULTS: Although median Snellen acuity equivalents were better than 20/20 in both groups, RNFL thickness was reduced significantly among eyes of MS patients (92 mum) versus controls (105 mum) (P<0.001) and particularly was reduced in MS ON eyes (85 mum; P<0.001; accounting for age and adjusting for within-patient intereye correlations). Lower visual function scores were associated with reduced average overall RNFL thickness in MS eyes; for every 1-line decrease in low-contrast letter acuity or contrast sensitivity score, the mean RNFL thickness decreased by 4 mum. CONCLUSIONS: Scores for low-contrast letter acuity and contrast sensitivity correlate well with RNFL thickness as a structural biomarker, supporting validity for these visual function tests as secondary clinical outcome measures for MS trials. These results also suggest a role for ocular imaging techniques such as OCT in trials that examine neuroprotective and other disease-modifying therapies. Although eyes with a history of acute optic neuritis demonstrate the greatest reductions in RNFL thickness, MS non-ON eyes have less RNFL thickness than controls, suggesting the occurrence of chronic axonal loss separate from acute attacks in MS patients.

Acute Disease↗
PubMed2006

Lens opacities associated with performance-based and self-assessed visual functions.

OBJECTIVE: To investigate the relationship of lens opacities to performance-based and self-assessed visual function in persons free of other ocular comorbidities. DESIGN: Cross-sectional cohort study. PARTICIPANTS: Beaver Dam Eye Study participants. METHODS: Lens photographs were taken and graded by protocols for age-related lens opacities. During the study evaluation, best-corrected visual acuity, near vision, and contrast sensitivity (performance-based visual functions) were measured. Questions were asked about visual function in particular settings (self-assessed visual functions). RESULTS: After the exclusion of other ocular comorbidities, performance-based visual functions were associated significantly (P< or =0.001 for each association) with severity of lens opacities, including relatively early lens opacities. Self-assessed visual functions were associated less consistently with severity of lens opacities (P<0.02 for all). In age-stratified analyses, there were fewer significant associations of self-assessed visual functions with severity of lens opacities for persons younger than 65 years than for persons 65 or older. CONCLUSIONS: Lens opacities across the range of severities were associated with measurable decreases in visual functions; the associations, especially for self-assessed functions, tended to be greater at older ages. It is likely that successful measures to decrease the severity of lens opacities will have a greater impact on older persons.

Aged↗
PubMed2006

Enhanced visual experiences and seeing hardware for reduced vision: a pilot study.

BACKGROUND: Persons with vision loss may have limited ability to experience visual arts and difficulty navigating unfamiliar environments. The Center for Advanced Visual Studies at Massachusetts Institute of Technology developed a Retinal Imaging Machine Vision System (RIMVS) "seeing machine" to project "word-images" onto the retina and permit navigation through virtual architectural environments. METHODS: Ten subjects with visual acuity < or = 20/70 in the better-seeing eye were recruited. Subjects viewed word-images that were projected on the retina of the better-seeing eye and asked to interpret the images. Subsequently, they were asked to recall as many images as possible. Participants also practiced navigation through a computer-modeled building that was projected onto the retina. A survey elicited subject response to the RIMVS. RESULTS: Six subjects correctly interpreted all 10 word-images; no subject interpreted fewer than 8 correctly. Seven subjects felt that the word images afforded easy recall, and 7 subjects responded that the technology might assist subsequent navigation in unfamiliar environments. CONCLUSIONS: Responses reflect a general interest and potential with the RIMVS. Further studies are warranted to explore the value of the RIMVS as a tool to enable visually compromised persons to experience and appreciate visual arts and as a navigation aid.

Adult↗
PubMed2006

A prospective study of the EYEPORT vision training system.

BACKGROUND: The purpose of this study was to determine if vision training with the EYEPORT system affects vision and reading performance. (Subsequent to this study, the "E.Y.E." has been renamed "EYEPORT") METHODS: College students with normal vision (n = 31) participated in a blind, crossover study to assess within-subject and between-group effects of EYEPORT training. Half the subjects initially underwent training (10 minutes per day, 6 days a week for 3 weeks), and then crossed over to the no-train control condition (3 weeks); the other half underwent the reverse sequence. Vision and reading performance were assessed at baseline, 3 weeks, and 6 weeks. RESULTS: Multivariate analyses (Hotelling's T2) found small improvements in vergence and accommodative facility, reading performance, and stereopsis response time after EYEPORT training (P < 0.025). Enhancements in reading performance and vergence facility were still present 3 weeks after cessation of training (P < 0.001). CONCLUSIONS: The EYEPORT training system shows potential to enhance visual performance and reading ability. Studies are underway to assess its efficacy in symptomatic populations.

Accommodation, Ocular↗
PubMed2004

Early improvements in vision after fractionated stereotactic radiotherapy for primary optic nerve sheath meningioma.

BACKGROUND AND PURPOSE: To report on the efficacy and follow-up of 23 patients with primary optic nerve sheath meningioma (ONSM) with fractionated stereotactic conformal radiotherapy (SCRT). PATIENTS AND METHODS: Between 1996 and 2003, 23 patients ( = 23 eyes) with ONSM were treated. Indications for primary stereotactic radiotherapy were tumour progression documented by imaging or symptoms (loss of vision, pain). All patients received SCRT with a median dose of 50.4Gy in 6 weeks. RESULTS: After a median follow-up of 20 months (1-68 months) a 95% (21 of 22) visual control was seen: vision improved in 16 patients and remained stable in 5. For 13/16 patients improvement was documented already within 1-3 months after SCRT. Vision became worse in one patient. An improvement of pain was observed after radiotherapy in 6 patients as well as of proptosis in 1 patient. For 1 patient pain was persistent after SCRT. In one patient 4 years after SCRT a radiation retinitis and vitreous haemorrhage was seen. CONCLUSIONS: Fractionated stereotactic radiotherapy improves vision, often shortly after treatment, and is thus a viable treatment option for this tumour entity.

Adolescent↗