Degrees Radius Research Articles

How wide should you view to fight? Establishing the size of the visual field necessary for grip fighting in judo

ABSTRACT Peripheral vision is often considered vital in (combat) sports, yet most experimental paradigms (e.g., eye tracking) ignore peripheral information or struggle to make inferences about the role of peripheral vision in an in-situ performance environment. This study aimed to determine where visual information is located in the peripheral field during an in-situ combat sports task. Eight advanced judokas competed in grip-fighting exchanges while wearing a mobile eye-tracker to locate gaze direction. Three-dimensional position data of the head and hands were tracked using a VICON motion capture system. Gaze analysis through automatic feature detection showed that participants predominantly fixated on their opponent’s chest. Kinematic data were used to calculate the angles between the opponent’s hands and the gaze-anchor point on the chest of the opponent. Results revealed a nonlinear relationship between visual field (VF) size and visibility of the hands, with athletes needing a VF of at least 30–40 degrees radius to simultaneously monitor both hands of the opponent most of the time. These findings hold implications for the regulation of Paralympic judo for athletes with vision impairment, suggesting that a less severe degree of impairment should be required to qualify than the current criterion of 20 degrees radius.

Clusterix 2.0: a virtual observatory tool to estimate cluster membership probability

ABSTRACT Clusterix 2.0 is a web-based, Virtual Observatory compliant, interactive tool for the determination of membership probabilities in stellar clusters based on proper-motion data using a fully non-parametric method. In an area occupied by a cluster, the frequency function is made up of two contributions: cluster and field stars. The tool performs an empirical determination of the frequency functions from the vector point diagram without relying on any previous assumption about their profiles. Clusterix 2.0 allows us to search the appropriate spatial areas in an interactive way until an optimal separation of the two populations is obtained. Several parameters can be adjusted to make the calculation computationally feasible without interfering with the quality of the results. The system offers the possibility to query different catalogues, such as Gaia, or upload a user’s own data. The results of the membership determination can be sent via Simple Application Messaging Protocol (SAMP) to Virtual Observatory (VO) tools such as Tool for OPerations on Catalogues And Tables (TOPCAT). We apply Clusterix 2.0 to several open clusters with different properties and environments to show the capabilities of the tool: an area of five degrees radius around NGC 2682 (M67), an old, well-known cluster; a young cluster NGC 2516 with a striking elongated structure extended up to four degrees; NGC 1750 and NGC 1758, a pair of partly overlapping clusters; the area of NGC 1817, where we confirm a little-known cluster, Juchert 23; and an area with many clusters, where we disentangle two overlapping clusters situated where only one was previously known: Ruprecht 26 and the new Clusterix 1.

First Space and Kinematical Analysis of Newly Discovered Southern UFMGs Clusters with Gaia

The work on the kinematical parameters and spatial shape structure have been performed with Gaia DR2 astrometry data of the new recently southern discovered open clusters; UFMG 1, UFMG 2, and UFMG 3 in the vicinity (1.3 degrees radius) of the rarely studied NGC 5999. The apexes positions with AD-diagram method are computed for about 107, 168, 98, and 154 members of these star clusters, respectively, our calculated values of apex coordinates, seems like: (A, D) = (102.40 +/- 1.02 & -4.60 +/- 0.47; NGC 5999), (96.69 +/- 1.10 & -0.58 +/- 0.045; UFMG 1), (97.47 +/- 1.09 & 1.56 +/- 0.051; UFMG 2), and (98.65 +/- 1.12 & -0.26 +/- 0.060; UFMG 3). On the other hand, Velocity Ellipsoid Parameters VEPs for those are also computed; e.g. space velocities due to Galactic coordinates, dispersion velocities (sigma_1, sigma_2, sigma_3) due to matrix elements for all ij, projected distances (X_sun, Y_sun, Z_sun) on the plane disc, and the Solar elements (S_sun, l_A, b_A). According to an approximation of spatial and kinematical shape, UFMGs and NGC 5999 seem to have a spatial difference in their space locations but they appear to have formed in the same region of the Galactic disc. The total cumulative mass MC; including total number of main-sequence NMS and non-main-sequence Nnon-MS of these clusters also evaluated here with a second-order polynomial of mass-luminosity relation in order to get clusters tidal radii (pc). Finally, we concluded that NGC 5999, UFMG 1, and UFMG 2 are dynamically relaxed (i.e. tau >> 1), and the fourth one in non-relaxed.

Red supergiants and the past of Cygnus OB2

Context. Red supergiants are the evolved descendants of massive stars with initial masses between 7 and 40 M-circle dot. Their brightness makes them easily detectable in the near infrared, making them useful probes of star formation that occurred several tens of Myr ago. Aims. We investigate the past star formation history of Cygnus OB2, the nearest very massive OB association, using red supergiants as a probe. Our aim is to confirm the evidence, found by previous studies, that star formation in the Cygnus OB2 region started long before the latest burst that gave rise to the dense aggregate of early O-type stars that dominate the appearance of the association at present. Methods. Near-infrared star counts in the Cygnus region reveal moderate evidence for a peak in the areal density of bright, reddened stars approximately coincident with Cygnus OB2. A total of 11 sources are found within a circle of 1 degrees radius centered on the association, of which 4 are non-supergiants based on existing observations. Near-infrared spectroscopy is presented of the remaining seven candidates, including four that have been already classified as M supergiants in the literature. Results. We confirm the presence of seven red supergiants in the region and argue that they are probably physically associated with Cygnus OB2. Their location is roughly coincident with that of the older population identified by previous studies, supporting the scenario in which the main star formation activity in the association has been shifting toward higher Galactic longitudes with time. Their luminosities are compared with the predictions of evolutionary tracks with and without rotation to estimate the mass of their progenitors and ages. In this way, we confirm that massive star formation was already taking place in the area of Cygnus OB2 over 20 Myr ago, and we estimate that the star formation rate in the latest 6 Myr represents a six-fold increase over the massive star formation rate at the time when the progenitors of the current red supergiants were formed. Conclusions. The Cygnus OB2 association has a history of star formation extending into the past for at least about 20 Myr, probably dovetailing with the general history of star formation in the region that gave rise to other associations like the neighboring Cygnus OB9. The sustained massive star formation history also argues for a long lifetime of the giant molecular complex from which Cygnus OB2 formed, whose remnants constitute the present-day Cygnus X complex.

Recent results from telescope array

The Telescope Array (TA) is an experiment to observe Ultra-High Energy Cosmic Rays (UHECRs). TA's recent results, the energy spectrum and anisotropy based on the 6-year surface array data, and the primary composition obtained from the shower maximum Xmax are reported. The spectrum demonstrates a clear dip and cutoff. The shape of the spectrum is well described by the energy loss of extra-galactic protons interacting with the cosmic microwave background (CMB). Above the cutoff, a medium-scale (20 degrees radius) flux enhancement was observed near the Ursa-Major. A chance probability of creating this hotspot from the isotropic flux is 4.0 sigma. The measured Xmax is consistent with the primary being proton or light nuclei for energies 10^18.2 eV - 10^19.2 eV.

A search for weak or complex magnetic fields in the B3V star Herculis

We obtained 128 high signal-to-noise ratio Stokes $V$ spectra of the B3V star $\iota$~Her on 5 consecutive nights in 2012 with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope, with the aim of searching for the presence of weak and/or complex magnetic fields. Least-Squares Deconvolution mean profiles were computed from individual spectra, averaged over individual nights and over the entire run. No Zeeman signatures are detected in any of the profiles. The longitudinal magnetic field in the grand average profile was measured to be $-0.24 \pm 0.32 $ G, as compared to $-0.22 \pm 0.32$ G in the null profile. Our observations therefore provide no evidence for the presence of Zeeman signatures analogous to those observed in the A0V star Vega by Lignieres et al. (2009). We interpret these observations in three ways. First, we compare the LSD profiles with synthetic Stokes $V$ profiles corresponding to organised (dipolar) magnetic fields, for which we find an upper limit of about 8~G on the polar strength of any surface dipole present. Secondly, we compare the grand average profile with calculations corresponding to the random magnetic spot topologies of Kochukhov & Sudnik (2013), inferring that spots, if present, of 2 degrees radius with strengths of 2-4 G and a filling factor of 50% should have been detected in our data. Finally, we compare the observations with synthetic $V$ profiles corresponding to the surface magnetic maps of Vega (Petit et al. 2010) computed for the spectral characteristics of $\iota$ Her. We conclude that while it is unlikely we would have detected a magnetic field identical to Vega's, we would have likely detected one with a peak strength of about 30 G, i.e. approximately four times as strong as that of Vega.

Clinical Results for Minimally Invasive Locked Plating of Proximal Humerus Fractures

To describe the minimally invasive treatment of fractures of the proximal humerus using the Non-Contact-Bridging (NCB) plate. The system allows secondary locking of screws to the plate with a locking cap and polyaxial (30 degrees radius) screw placement. Prospective cohort study. University Level I trauma center. Fifty-four patients with unstable fractures of the proximal humerus. Minimal anterolateral acromial approach to the proximal humerus, percutaneous fracture reduction, and minimally invasive application of the NCB plate. Constant Score and radiologic follow-up (anteroposterior and transscapular). Visual Analog Scale for subjective evaluation of pain and function. After 17 months, the average Constant Score was 66.8 points (87% of the age- and sex-related normal values). Implant-related complications (plate impingement, screw perforation into the glenohumeral joint, loosening of screws) occurred in nine cases (17%). The rate of avascular necrosis was low (5.5%) and no cases of nonunion were seen. The effectiveness of the NCB is similar to other published methods of treatment for fractures of the proximal humerus and potentially provides a less invasive option for this problem. Complication rates and functional outcome in this series are comparable to the literature. An important factor in this technique is the process of percutaneous fracture reduction. The NCB plate is suitable for both a minimally invasive technique or standard open reduction and internal fixation through a deltopectoral approach; the surgeon must decide which approach is best for each particular fracture pattern and should be comfortable with both techniques.

Relationships between clinical measures of visual function and anatomic changes associated with bevacizumab treatment for choroidal neovascularization in age-related macular degeneration

This pilot study was undertaken to examine the relationships between clinical measures of visual function and anatomic changes occurring in the eyes treated with bevacizumab for choroidal neovascularization (CNV) due to age-related macular degeneration (AMD). A retrospective review was conducted for 50 eyes that had been treated with at least three injections of bevicizumab for CNV due to AMD, and followed for at least 6 months. Vision outcomes included best-corrected ETDRS chart acuity, scored by best-line read (ETDRS line) and by total letters read (ETDRS letter), and two measures obtained from central acuity perimetry with 98% Michelson contrast targets, the best acuity within 6 degrees of fixation (BA6 degrees ), and global macular acuity (GMA), representing a weighted average of the acuities thresholded at all intercepts within a 10 degrees radius of fixation. Assessment of anatomic outcomes included fibrosis, atrophy, and subretinal hemorrhage grading on fundus photography, CNV size, pigment epithelial detachment (PED) size and grading of CNV leakage on fluorescein angiography, and central retinal PED, and subretinal fluid (SRF) thickness on optical coherence tomography. Logistic regression analysis showed an association between the vision outcomes of EDTRS letter and BA6 degrees with the change in SRF thickness (R (2): 0.47 and 0.35, respectively). The outcome of the vision measurement of GMA was associated with the change in SRF thickness, in CNV thickness, and in CNV fibrosis grade (R (2): 0.34). No association was noted between the outcomes of ETDRS line with the change in any anatomic outcomes. Acuity perimetry outcomes in this study seemed to offer improved understanding of the relationship between the vision outcomes and the measured anatomic changes. It seemed that neither ocular coherence tomography nor fluorescein angiography alone offered sufficient morphologic markers for prediction of functional outcomes.

Parafoveal letter recognition at reduced contrast in normal aging and in patients with risk factors for AMD

Patients with early age-related maculopathy (ARM) do not necessarily show obvious morphological signs or functional impairment. Many have good visual acuity, yet complain of decreased visual performance. The aim of this study was to investigate the aging effects on performance of parafoveal letter recognition at reduced contrast, and defects caused by early ARM and normal fellow eyes of patients with unilateral age-related macular degeneration (nfAMD). Testing of the central visual field (8 degrees radius) was performed by the Macular Mapping Test (MMT) using recognition of letters in 40 parafoveal target locations at four contrast levels (5, 10, 25 and 100%). Effects of aging were investigated in 64 healthy subjects aged 23 to 76 years (CTRL). In addition, 39 eyes (minimum visual acuity of 0.63;20/30) from 39 patients with either no visible signs of ARM, while the fellow eye had advanced age-related macular degeneration (nfAMD; n = 12), or early signs of ARM (eARM; n = 27) were examined. Performance was expressed summarily as a "field score" (FS). Performance in the MMT begins to decline linearly with age in normal subjects from the age of 50 and 54 years on, at 5% and 10% contrast respectively. The differentiation between patients and CTRLs was enhanced if FS at 5% was analyzed along with FS at 10% contrast. In 8/12 patients from group nfAMD and in 18/27 from group eARM, the FS was statistically significantly lower than in the CTRL group in at least one of the lower contrast levels. Using parafoveal test locations, a recognition task and diminished contrast increases the chance of early detection of functional defects due to eARM or nfAMD and can differentiate them from those due to aging alone.

Cognitive and Vision Loss Affects the Topography of the Attentional Visual Field

The attentional visual field (AVF), which describes a person's ability to divide attention and extract visual information from the visual field (VF) within a glance, has been shown to be a good predictor of driving performance. Despite this, very little is known about the shape of the AVF and the factors that affect it. The purposes of this study were to describe the AVF in a large sample of older drivers and identify demographic, cognitive, and vision factors associated with AVF performance and shape. Registered drivers between 67 and 87 years of age, residing in Greater Salisbury, Maryland, were recruited to participate in the study. Participants underwent a battery of visual and cognitive assessments and completed various questionnaires for demographics, medical history, and history of depression. The AVF was assessed using a divided-attention protocol within the central 20 degrees radius along the four principal meridians. The shape of the AVF was classified as either symmetric or one of two asymmetric shape profiles. Symmetrically shaped AVFs were found in just 34% of participants. AVF performance was significantly better along the horizontal (15.3 degrees ) than the vertical (11.3 degrees ) meridian (P < 0.05). After adjusting for AVF area, we found that poorer cognitive and vision performance was associated with a symmetric AVF shape. Overall AVF extent was predicted by vision and cognitive measures as well as various demographic factors. Good vision and cognitive ability appear to be associated with having an asymmetric as opposed to a symmetric AVF shape profile.

Visual Field Loss Increases the Risk of Falls in Older Adults: The Salisbury Eye Evaluation

Falls are a serious and preventable problem in older adults. Impaired vision has been linked to risk of falls; however, the impact of deficits in specific components of vision on the risk of falls is not well known. Data on falls for up to 20 months were provided by 2375 individuals participating in the Salisbury Eye Evaluation (SEE). Visual acuity, contrast sensitivity, visual field, and stereoacuity were tested by using standard measures. To aid in the assessment, each participant recorded falls on a calendar that was sent every month to the SEE clinic. beta-Binomial regression analysis was used. Worse visual field scores were associated with the risk of falling (OR = 1.08 for a 10-point loss of points, 95% CI 1.03-1.13). When both central (</= 20 degrees radius) and peripheral visual fields were in the same model, only the peripheral visual field was associated with falls (OR = 1.06, 95% CI 1.01-1.10). Visual acuity, contrast sensitivity, and stereoacuity were not associated with falls after adjustment for demographic and health variables. Visual field loss is the primary vision component that increases the risk of falls. This finding highlights the importance of visual field deficits in the risk of falls and supports other findings on decrements in mobility and increased risk of bumping with worsening visual field function. Persons with visual field loss may benefit from mobility training to reduce the risk of falling.

The Third VLBA Calibrator Survey: VCS3

This paper presents the third extension to the Very Large Baseline Array (VLBA) Calibrator Survey, containing 360 new sources not previously observed with very long baseline interferometry (VLBI). The survey, based on three 24 hour VLBA observing sessions, fills the areas on the sky above declination -45 degrees where the calibrator density is less than one source within a 4 degrees radius disk at any given direction. The positions were derived from astrometric analysis of the group delays determined at 2.3 and 8.6 GHz frequency bands using the Calc/Solve software package. The VCS3 catalogue of source positions, plots of correlated flux density versus the length of projected baseline, contour plots and fits files of naturally weighted CLEAN images as well as calibrated visibility function files are available on the Web at http://gemini.gsfc.nasa.gov/vcs3

The ellipsoidal corrections to the topographic geoid effects

The topographic effects by Stokes’ formula are typically considered for a spherical approximation of sea level. For more precise determination of the geoid, sea level is better approximated by an ellipsoid, which justifies the consideration of the ellipsoidal corrections of topographic effects for improved geoid solutions. The aim of this study is to estimate the ellipsoidal effects of the combined topographic correction (direct plus indirect topographic effects) and the downward continuation effect. It is concluded that the ellipsoidal correction to the combined topographic effect on the geoid height is far less than 1 mm. On the contrary, the ellipsoidal correction to the effect of downward continuation of gravity anomaly to sea level may be significant at the 1-cm level in mountainous regions. Nevertheless, if Stokes’ formula is modified and the integration of gravity anomalies is limited to a cap of a few degrees radius around the computation point, nor this effect is likely to be significant.

Association of visual field loss and mobility performance in older adults: Salisbury Eye Evaluation Study.

To determine the association between visual field loss and orientation and mobility (O&M) performance in a population-based sample of older adults and to identify the specific regions of the visual field that are most strongly associated with O&M performance. A population-based sample of 1504 persons between the ages of 72 to 92 was enrolled in the third round of Salisbury Eye Evaluation. Monocular visual fields (60 degrees radius) were tested with the 81-point, single intensity (24 dB) screening test strategy on the Humphrey Field Analyzer. Binocular visual fields were estimated from a combination of the monocular fields. The number of points missed was calculated for the overall visual field and for 3 non-overlapping regions: central (< or = 20 degrees radius), upper- and lower-peripheral visual fields. Orientation and mobility performance was evaluated by walking speed, number of bumps, and number of orientation errors on a circuitous, 32.8-m course seeded with obstacles. Log-linear regressions and linear regressions, adjusting for age, gender, body mass, height, cognitive and general health status, were performed. Loss in the overall visual field was associated with an increase in the number of bumps and decrease in walking speed. Visual field loss was not associated with the number of orientation errors. Out of the three visual field sub-regions that we tested, in terms of percentage of loss, the central and lower peripheral regions showed comparable decrements in walking speed and the central region was most strongly associated with number of bumps. The loss in visual field, which occurs with aging, is associated with a decline in mobility performance. Walking speed decreases, and the number of bumps into obstacles increases, with decreases in the visual field. The number of orientation errors is not associated with the loss in visual field that occurs with aging.

Examining visual field defects in the paediatric population exposed to vigabatrin.

The antiepileptic drug, vigabatrin, has been linked to a specific pattern of visual field loss. The majority of studies have not included the paediatric population due to difficulties assessing visual field function. This is a particular problem as vigabatrin is effective against infantile spasms. A field-specific visual evoked potential was developed which consisted of a central stimulus (0-5 degrees radius) and a peripheral stimulus (30-60 degrees radius). Both stimuli consist of black and white checks which increase in size with eccentricity. Responses are recorded from occipital electrodes O2 and O1 referred to frontal electrode Fz. Electroretinograms and perimetry was performed were possible as a comparison. Thirty-nine children with epilepsy treated with vigabatrin aged from 3 to 15 years were included in the study; 35/39 children complied with the field-specific VEP, 26/39 complied with the ERG and 11/39 performed perimetry. Of these results, 18 children had normal ERG responses and eight had abnormal response. Visual field testing revealed four children had abnormal and seven had abnormal visual field results. The Field-specific VEP identified three of four abnormal perimetry results and six of seven normal perimetry results, giving a sensitivity of 75% and a specificity of 85.7%. When comparing perimetry results with the ERG parameters only the 30-Hz flicker amplitude, with a cut-off amplitude below 70 microV, gave a useful sensitivity of 75% and a specificity of 71%. The field-specific VEP is a useful alternative method that is both well tolerated by young children and gives a reliable indication of likely peripheral visual field loss associated with vigabatrin. The defect appears to have a similar prevalence in children as it does in adults.

Pattern-onset stimulation boosts central multifocal VEP responses.

Multifocal visual evoked potentials (VEP) allow one to assess whether stimulation at specific visual field locations elicits cortical activity; it might therefore enable us to conduct objective visual field perimetry. However, due to the cortical folding, which differs markedly between subjects, a particular electroencephalogram generator may fail to project signal on some recording electrodes. This may lead to false alarms for potential scotomata. Here we compare pattern-reversal and pattern-onset stimulation in their efficacy to activate the visual cortex and recorded mfVEPs to 60 locations comprising a visual field of 44 degrees diameter. We report three main findings: (1) Pattern-onset compared to pattern-reversal enhances the amplitude by 30% for stimulation of the central visual field (<10 degrees radius), while evoking 30% less response in the periphery (>15 degrees ). (2) Although pattern-onset and pattern-reversal responses differ markedly in their eccentricity dependence, they have a similar topographical distribution. (3) By combining both stimuli, the number of false positives was reduced to less than 1.5% of the visual field locations tested. We conclude that pattern-onset and pattern-reversal activate identical visual cortical areas but target different neural mechanisms within these areas. Furthermore, pattern-onset stimulation greatly increases the sensitivity of the mfVEP to assess the cortical representation of the central 10 degrees of the visual field.

Latency of the pupil light reflex: sample rate, stimulus intensity, and variation in normal subjects.

To investigate the clinical usefulness of the latency of the pupil light reflex by optimizing its measurement, characterizing its variability, and determining the sensitivity of pupil latency as a function of stimulus input in normal subjects. Computerized binocular infrared pupillography was performed in 14 eyes of seven healthy subjects. Pupils were recorded simultaneously at 60 and 1000 Hz. Each eye was alternatively stimulated eight times for 50 ms every 2.5 seconds, increasing by 0.5 log units over a 2.0-log-unit range. To determine intersubject and intereye variability, 98 eyes of 49 healthy subjects were recorded at 60 Hz over a 3.0-log-unit range (15 degrees radius stimulation, four repetitions at each intensity). Accuracy and resolution of latency were limited by the number of light reflexes used to estimate the average latency and were significantly affected by sampling rate when the number of reflexes recorded was fewer than four. Binocular recording and interpolation of the 60-Hz recording to 300 Hz added resolution to the latency. Biological variability contributed more to interindividual variability than did measurement variability. The range of intereye afferent asymmetry of latency in normal subjects was only between 8.3 and 35 ms-less with brighter stimulus intensity. An optimal method for determination of the onset of the pupil light reflex was devised that consisted of filtering, interpolation of pupil recordings, and analysis of the first and second derivative of the pupil movement. Most of the variability in latency as a function of intensity in normal subjects was due to interindividual variation and latency was well matched between the two eyes of the subjects.

National Registry for the Blind in Israel: Estimation of prevalence and incidence rates and causes of blindness

OBJECTIVE To describe the population registered as blind in Israel and estimate the prevalence and incidence of blindness, by age, sex and the causes of blindness. METHODS Israel has maintained a Registry for the Blind since 1987. Patients are identified by ophthalmologists and registered if they have a visual acuity of =0.05 (20/400) or a visual field of <20 degrees radius in their better eye. The Registry consists of all eligible citizens living in Israel at the time of registration. This report includes prevalence data on 18,891 persons enrolled in the Registry from 1987–1999 and still alive and living in Israel in 1999, and incidence data on 2,511 persons newly registered in 1999. Data were collected on visual acuity and visual field loss, cause of blindness, and patient demographics. RESULTS In 1999, the estimated prevalence rate of blindness nation-wide was 0.31% and the estimated incidence rate was 0.037%. The major causes of blindness in the complete Registry were age related macular degeneration (AMD) and glaucoma (14%), followed by diabetic retinopathy (11%), cataract and myopic maculopathy (10%), and optic atrophy (8.4%). The leading causes of newly diagnosed blindness were age-related macular degeneration (AMD) (20%), glaucoma (14%), diabetic retinopathy (12%), myopic maculopathy (11%), and optic atrophy and cataract (10%). CONCLUSIONS Israel has one of the few nationwide blindness registries in the world. The prevalence and incidence of blindness in Israel appear to be comparable to other western countries Comparisons are difficult because of different definitions of blindness, age distributions, and the uniqueness of the Israeli Registry.

Paleomagnetic pole positions and pole reversals of Mars

The paleomagnetic pole positions of Mars obtained by modeling 10 small‐size, isolated magnetic anomalies show considerable clustering, 7 out of 10 are within a circle of 30 degrees radius centered at (230E, 25N). The directions of the magnetization of some nearby source bodies differ by ∼180 degrees and both north and south poles are found in the cluster, suggesting the magnetic pole reversals of Mars.

Cause-specific prevalence of bilateral visual impairment in Victoria, Australia

To study the cause-specific prevalence of eye diseases causing bilateral visual impairment in Australian adults. Two-site, population-based cross-sectional study. Participants were aged 40 years and older and resident in their homes at the time of recruitment for the study. The study was conducted during 1992 through 1996. The study uses a cluster stratified random sample of 4744 participants from two cohorts, urban, and rural Victoria. Participants completed a standardized interview and eye examination, including presenting and best-corrected visual acuity, visual fields, and dilated ocular examination. The major cause of vision loss was identified for all participants found to be visually impaired. Population-based prevalence estimates are weighted to reflect the age and gender distribution of the two cohorts in Victoria. Visual impairment was defined by four levels of severity on the basis of best-corrected visual acuity or visual field: <6/18 > or =6/60 and/or <20 degrees > or =10 degrees radius field, moderate vision impairment; severe vision impairment, <6/60 > or =3/60 and/or <10 degrees > or =5 degrees radius field; and profound vision impairment <3/60 and/or <5 degrees radius field. In addition, less-than-legal driving vision, <6/12 > or =6/18, and/or homonymous hemianopia were defined as mild vision impairment. In Australia, legal blindness includes severe and profound vision impairment. The population-weighted prevalence of diseases causing less-than-legal driving or worse impairment in the better eye was 42.48/1000 (95% confidence interval [CI], 30.11, 54.86). Uncorrected refractive error was the most frequent cause of bilateral vision impairment, 24.68/1000 (95% CI, 16.12, 33.25), followed by age-related macular degeneration (AMD), 3.86/1000 (95% CI, 2.17, 5.55); other retinal diseases, 2.91/1000 (95% CI, 0.74, 5.08); other disorders, 2.80/1000 (95% CI, 1.17, 4.43); cataract, 2.57/1000 (95% CI, 1.38, 3.76); glaucoma, 2.32/1000 (95% CI, 0.72, 3.92); neuro-ophthalmic disorders, 1.80/1000 (95% CI, 0, 4.11); and diabetic retinopathy, 1.53/1000 (95% CI, 0.71, 2.36). The prevalence of legal blindness was 5.30/1000 (95% CI, 3.24, 7.36). Although not significantly different, the causes of legal blindness were uncorrected refractive errors, AMD, glaucoma, other retinal conditions, and other diseases. Significant reduction of visual impairment may be attained with the application of current knowledge in refractive errors, diabetes mellitus, cataract, and glaucoma. Although easily preventable, uncorrected refractive error remains a major cause of vision impairment.