Visual midline gauge validity and repeatability: Comparison to a current clinical method.

SIGNIFICANCE: Visual midline shifts are thought to occur post-stroke and be a risk factor for falls. This study investigates a new method for quantifying visual midline shifts, a first step toward developing greater understanding of visual midline shift. PURPOSE: This study standardized the parameters of a novel visual midline gauge, compared the results with the current clinical method, and presents normative data and repeatability of both methods. METHODS: Ninety-three participants without neurological or ocular problems were recruited in Canada and Hong Kong. In experiment 1, horizontal and vertical visual midlines were measured using the gauge for two speeds and two repositioning methods. In experiment 2, visual midline was measured for three distances using a target speed and repositioning method chosen based on the first experiment. Visual midlines were also measured using the current clinical method during both visits. RESULTS: There were no significant effects of age, speed, study location, or repositioning method on visual midline positions (all p>0.05). For the horizontal direction, measurements at 25 cm were different from those at 50 (p=0.03) and 100 cm (p=0.001). For the vertical direction, there was no such effect. The measurements were found to be repeatable to within approximately 3°. In both visits, there were significant correlations between measurements using the visual midline gauge and the clinical method for the vertical direction (all p<.001) but not for the horizontal direction (all p>0.05). CONCLUSIONS: The measurement of visual midline is tolerant of differences in target speed, testing method, and age of the participants, and the visual midline gauge measurements are repeatable.

Comparing paediatric optometric vision care in Canada over a 14-year period.

PURPOSE: In Canada, teaching in paediatric eye care has increased in the past decade both within the optometry curriculum and as continuing education to optometrists. Paediatric vision care guidelines have also been established by North American optometric associations. This study examined whether this exposure was associated with changes in paediatric eye care in Canada over a 14-year period. METHODS: Canadian optometrists were invited to participate in an anonymous 35-item survey in 2007 and 2021. The surveys sought to investigate optometrist's recommendations for first eye examinations, the number of paediatric patients seen in a typical week and preparedness to provide eye examinations to children. Response frequencies were determined for each survey item. RESULTS: Across Canada, 133/1000 (13.3%) and 261/~6419 (~4.1%) optometrists responded to the survey in 2007 and 2021, respectively. No significant difference was found in the number of years practicing, days per week in practice and total number of patients seen per week. The modal age optometrists recommended children be seen for their first eye examination changed from 3-4 years in 2007 (53%) to 6-12 months in 2021 (61%). In 2007, 87% of respondents provided eye examinations to children <2 years, increasing to 94% in 2021 (p = 0.02). Despite a reduction in the recommended age between the two survey years, the most frequent age children were seen for their first eye examination was 3-4 years (30% in both surveys) and the most common age seen in a typical week remained unchanged (4-6 years-56% 2007; 66% 2021). CONCLUSION: Although optometrists' willingness to provide paediatric eye care increased over the past 14 years, the number of children seen in a typical week did not change. Barriers to determine why more children are not being seen at an earlier age need to be investigated.

Can older adults' balance and mobility improve with visual attention training?

PURPOSE: We hypothesize that training older adults with a structured visual attention task will result in improved balance and mobility, potentially reducing their risk for falls. METHODS: Healthy older adults aged 70 + took part in the study (mean age 80.3 ± 6 years). In this randomised control trial (NCT02030743), 15 participants were randomly assigned to a visual attention training group and 15 to a control group. Visual attention training was undertaken twice a week (45 min sessions) for 3 weeks (= six sessions) using versions of a selective attention useful field of view test and attended field of view test. The outcome measures were postural sway using a force plate, the Mini-Balance Evaluation Systems Test, the One-Legged Stance test, the 5 Meter Walking test, the Sit to Stand test, the Timed Up and Go test without and with a concurrent cognitive task. RESULTS: There was a greater improvement in visual attention after training in the intervention group compared to the control group (p < 0.01). However, a mixed ANOVA (2× groups, 2× visit) showed no main effect of visit or group or any interaction for any of the force plate parameters. T tests of the changes over time between the intervention group and the control groups for the other balance and mobility assessment tools showed no improvement after the visual attention training. CONCLUSION: It was found that there was no improvement in either mobility or balance after the visual attention training and no difference between the intervention and the control groups.

Development and validation of Visual Impairment as a Risk for Falls Questionnaire.

Purpose: visual impairment is associated with an increased risk of falls, yet eye care professionals are infrequently members of falls prevention clinics. The aim of this preliminary study was to validate a newly created Visual Impairment as a Risk for Falls Questionnaire intended to be used by those professionals not involved in eye care. Methods: about 53 participants with various visual impairments known to be associated with falls and 33 participants with normal sight were contacted within 4 months of a full oculo-visual assessment and were asked the questions from the current questionnaire pertaining to their visual function. A retrospective file review was undertaken and the sensitivity and specificity of participants' responses were calculated compared to the actual vision impairment based on the findings from their visual assessment. Results: the question regarding ability to read was included to identify people with central vision loss, a risk factor for falling. It was found to have sensitivity of 74% and specificity of 87%. Both sensitivity and specificity improved when participants with cognitive impairment were excluded. The question on recognising facial features gave sensitivity of 73% and specificity of 97% for this subgroup. However, questions related to impairments in stereopsis and peripheral fields were not useful. Conclusion: the study demonstrates that several questions of the new questionnaire are useful; however, further testing with a larger population is needed to fully validate the questionnaire for use by health care professionals.

Prevalence of vision loss among hospital in-patients; a risk factor for falls?

PURPOSE: Despite poor vision being a risk factor for falls, current hospital policies and practices often do not include a vision assessment at patient admission or in the hospital's incident reporting system when a fall occurs. Our purpose was to document the prevalence of vision loss in hospital general medicine units to increase awareness of poor vision as a potential risk factor for falls that occur within the hospital, and inform future preventative practice. METHODS: This cross-sectional study took place in medicine units of an acute care hospital. Participants were adult in-patients. Visual acuity (VA), contrast sensitivity and stereoacuity were measured, and patients were screened for field loss, extinction and neglect. RESULTS: 115 participants took part (average age 67 ± 17, 48% female). Overall, 89% had a visual impairment defined as being outside the age-norms for one or more vision measure, 62% had low vision, and 36% had vision loss equivalent to legal blindness [VA equal to or poorer than 1.0 logMAR (6/60, 20/200) or ≥10x below age-norms]. There was a considerable discrepancy between the prevalence of low vision and the percentage of patients who reported an ocular diagnosis that would result in visual loss (30%). Ten patients fell during the study period, and of these 100% had visual impairment, 90% had low vision and 60% had vision loss equivalent to legal blindness, which compares to 58%, 22% and 9% for non-fallers. Similar high prevalences were found in those whose reason for admission to the hospital was a fall (92%, 63% and 33% respectively). CONCLUSIONS: Vision loss has a high prevalence among patients in hospital medicine units, and is higher still among those who fall. Since vision loss may be a contributing factor to falls that occur in hospitals, implementing an assessment of vision at hospital admission would be useful to alert staff to those patients who are at risk for falls due to poor vision, so that preventative measures can be applied.

Binocular Vision Disorders and Visual Attention: Associations With Balance and Mobility in Older Adults.

Understanding which aspects of vision are related to falls is important. We examine the associations between tests of balance, mobility, fear of falling (FES-1) and aspects of vision in 72 adults aged 70+. Balance and mobility were examined using the One Legged Stance test (OLST), the Sit to Stand test (STST) and the 5 Meter Walking test (5MWT). Visual measures included visual acuity (VA), contrast sensitivity, stereoacuity, binocular vision (BV) measurements, Useful field of View (UFV) and Attended Field of View (AFOV). Reduced performance on the OLST and the STST was significantly correlated with abnormal BV and poorer intermediate VA. Poorer function on the 5MWT and the FES-I was also predicted by poor intermediate VA and poorer performance on the OLST, STST and the 5MWT was associated with UFV errors. The results are of high importance as many BV disorders are treatable and visual attention is trainable.

A Standardized Arabic Reading Acuity Chart: The Balsam Alabdulkader-Leat Chart.

PURPOSE: The aim of this study was to develop and validate the first standardized Arabic continuous text near-visual-acuity chart, the Balsam Alabdulkader-Leat (BAL) chart. METHODS: Three versions of the BAL chart were created from previously validated sentences. Reading acuity (RA) and reading speed in standard-length words per minute (SLWPM) were measured for three versions of the BAL chart and three English charts (MNREAD, Colenbrander, and Radner) for 86 bilingual adults with normal vision aged 15 to 59 years. The RA and SLWPM were compared using analysis of variance. To analyze agreement between the charts, Bland-Altman plots were used. Normal visual acuity (0.00 logMAR [log minimum angle of resolution]) was calibrated for the BAL chart with linear regression analysis. RESULTS: Average RAs for BAL1, BAL2, and BAL3 were 0.62, 0.64 and 0.65 log-point print, respectively, which were statistically significantly different (repeated-measures analysis of variance, P < .05), but not considered clinically significant. The coefficients of agreement for RA between the BAL charts were 0.054 (between 1 and 2), 0.061 (between 2 and 3), and 0.059 (between 1 and 3). Linear regression between the average RA for the BAL chart and the MNREAD and Radner charts showed that 0.7 log-point size at 40 cm is equivalent to 0.00 logMAR, and the new BAL chart was labeled accordingly. Mean SLWPM for the BAL charts was 201, 195, and 195 SLWPM, respectively, and for the Colenbrander, MNREAD, and Radner charts was 146, 171, and 146, respectively. The coefficients of agreement for log-SLWPM between BAL1 and BAL2, BAL2 and BAL3, and BAL1 and BAL3 were 0.063, 0.064, and 0.057 log-SLWPM, respectively. CONCLUSIONS: The BAL chart showed high interchart agreement. It is recommended for accurate near performance measures in Arabic for both research and clinical settings.

Visual Acuity and Contrast Sensitivity Development in Children: Sweep Visually Evoked Potential and Psychophysics.

PURPOSE: The purpose of this study was to investigate the development of visual acuity (VA) and contrast sensitivity in children as measured with objective (sweep visually evoked potential) and subjective, psychophysical techniques, including signal detection theory (SDT), which attempts to control for differences in criterion or behavior between adults and children. Furthermore, this study examines the possibility of applying SDT methods with children. METHODS: Visual acuity and contrast thresholds were measured in 12 children 6 to 7 years old, 10 children 8 to 9 years old, 10 children 10 to 12 years old, and 16 adults. For sweep visually evoked potential measurements, spatial frequency was swept from 1 to 40 cpd to measure VA, and contrast of sine-wave gratings (1 or 8 cpd) was swept from 0.33 to 30% to measure contrast thresholds. For psychophysical measurements, VA and contrast thresholds (1 or 8 cpd) were measured using a temporal two-alternative forced-choice staircase procedure and also with a yes-no SDT procedure. Optotype (logMAR [log of the minimum angle of resolution]) VA was also measured. RESULTS: The results of the various procedures were in agreement showing that there are age-related changes in threshold values and logMAR VA after the age of 6 years and that these visual functions do not become adult-like until the age of 8 to 9 years at the earliest. It was also found that children can participate in SDT procedures and do show differences in criterion compared with adults in psychophysical testing. CONCLUSIONS: These findings confirm a slightly later development of VA and contrast sensitivity (8 years or older) and indicate the importance of using SDT or forced-choice procedures in any developmental study to attempt to overcome the effect of criterion in children.

A Proposed Model for Integrated Low-Vision Rehabilitation Services in Canada.

PURPOSE: The provision and funding of low-vision rehabilitation (LVR) are very variable across Canada. Quebec is well served by 14 government-funded rehabilitation centers. In most provinces, there are no such multidisciplinary services-optometrists offer LVR from their offices to a greater or lesser degree or undertake assessments in centers run by CNIB (formerly Canadian National Institute for the Blind). No integrated model for LVR exists across Canada. This document proposes such a model, which focuses on the profession of optometry, but may also be applicable to ophthalmology. METHODS: This article describes different models of LV provision, the evidence for their relative effectiveness, the current situation in Canada, including the variability between areas and the need to increase referrals to LVR, and the current international consensus for LV provision. With the projected increase in people with LV, a generally accepted LV model for Canada is required to improve patient care. RESULTS: It has become recognized in the global community that a tiered system may be required to provide for patients who range in their visual rehabilitation needs and geographic locations. The proposed LVR model includes three levels: 1. Screening/recognition of a potential patient with LV followed by appropriate triage. All optometrists should be involved at this level. 2. Management of the patient with minimum visual impairment/disability. This level of LVR can take place in a local optometry office with a minimal of extra equipment or devices. Level 3: Comprehensive LVR for patients with more vision loss and greater disabilities. Level 3 requires collaboration with other professionals, and three mechanisms are proposed by this which may take place. CONCLUSIONS: The proposed model is expected to be useful for future education, policy decisions, and collaboration in Canada, and it may also be of interest for the development of LV services in other countries.

Value of Routine Eye Examinations in Asymptomatic Patients.

PURPOSE: To determine if routine eye examinations in asymptomatic patients result in spectacle prescription change, new critical diagnosis, or new management of existing conditions. We also investigate whether age and time between assessments (assessment interval) impact detection rates. METHODS: The Waterloo Eye Study (WatES) database was created from a retrospective file review of 6397 patients seen at the University of Waterloo Optometry Clinic. Significant changes since the previous assessment (significant change) were defined as a change in spectacle prescription, presence of a new critical diagnosis, or a new management. Significant change, assessment interval, and age were extracted from the database for all asymptomatic patients presenting for a routine eye examination. The frequency of patients with significant change and the median assessment interval were determined for different age groups. RESULTS: Of 2656 asymptomatic patients, 1078 (41%) patients had spectacle prescription changes, 434 (16%) patients had new critical diagnoses, 809 (31%) patients had new managements, and 1535 (58%) patients had at least one of these (significant change). Median assessment intervals were 2.9 and 2.8 years for age groups 40 to <65 years and 20 to <40 years, respectively, approximately 1.5 years for patients 7 to <20, and between 1 and 1.5 years for patients <7 or >64. Controlling for assessment interval and sex, increasing age was associated with having a significant change (OR = 1.03, 95% CI 1.029-1.037). Similarly, controlling for age and sex, increased assessment interval was associated with having a significant change (OR = 1.06, 95% CI 1.02-1.11). CONCLUSIONS: In asymptomatic patients, comprehensive routine optometric eye examinations detect a significant number of new eye conditions and/or result in management changes. The number detected increases with age and assessment interval.

Improving the legibility of prescription medication labels for older adults and adults with visual impairment.

OBJECTIVES: Most current prescription labels fail to meet print guidelines, especially in print size. We therefore compared the legibility of current prescription medication labels against the legibility of prototype labels, based on current guidelines for legibility. METHOD: Sample medication labels were obtained from pharmacies, and prototype medication labels were developed according to legibility guidelines from nongovernmental organizations and pharmacy organizations. Three groups of participants, consisting of older adults with normal vision, older adults with visual impairment and younger adults with visual impairment (total N = 71) took part. Participants were asked to read and rank the labels. Reading speed and accuracy were determined. RESULTS: Accuracies were high (75%-100%), and there were no significant differences between samples or prototypes or between groups. Prototypes, however, were read faster than samples (p < 0.001). Subjectively, participants preferred the largest print option (p < 0.001) and instructions with the numbers written in highlighted uppercase words (p < 0.001). DISCUSSION: The results indicate that improvements to the label would include larger print size, a consistent layout with left justification and using upper case with highlighting for emphasis of the numbers in the instructions.

Low-vision service provision by optometrists: a Canadian nationwide survey.

PURPOSE: To document the degree to which Canadian optometrists are involved in the provision of low-vision (LV) care and their referral patterns. To investigate the barriers to providing optometric low-vision services (LVS). METHODS: Practicing optometrists across Canada were randomly sampled and invited to participate in a questionnaire that included questions on personal profile, primary practice profile, levels of LV care offered, patterns of referral, and barriers to provision of LV care. Questions included a combination of multiple choice and open-ended formats, and included hypothetical cases. RESULTS: A total of 459 optometrists responded (response rate, 24.8%). Optometrists estimated that 1% (range, 0 to 100%) of their patients were LV patients yet also estimated that 10% of their patients had acuity equal to or worse than 20/40. Thirty-five percent of respondents indicated that their primary practice offered LV care, 75.6% would manage a patient with minimum disability and simple goals themselves, whereas 10.7% would manage a patient with more than minimal visual disability who needed more specialized LV devices (e.g., telescopes, electronic aids, and custom-designed microscopes); 84.3% of optometrists would assess for basic magnification and lighting in a hypothetical patient with early age-related macular degeneration, whereas 15% would undertake full LV rehabilitation in advanced age-related macular degeneration. Optometrists commonly referred to CNIB (formerly the Canadian National Institute for the Blind), yet only 10.7% of respondents almost always received a written report after referral. Those who would not undertake LV assessment stated that they lacked the knowledge, equipment, or experience; that LV assessment is too time consuming; and that the cost is too prohibitive. CONCLUSIONS: This is the first comprehensive study of LVS provision by optometrists in Canada. In order for optometrists to become more involved in LVS, there is a need for more LV education, provincial health coverage of optometric LVS, and better collaboration communication between LV providers.

Measuring Infant Visual Acuity with Gaze Tracker Monitored Visual Fixation.

PURPOSE: To validate a method of measuring grating acuity with remote gaze tracking (GT) against a current clinical test of visual acuity (VA), the Teller Acuity Cards (TACs), as part of the development of an automated VA test for infants. METHODS: Visual acuity for computer-generated horizontal square-wave gratings was determined from relative fixation time on a grating area compared with the background. In experiment 1, binocular VA was based on eye movements with a GT in 15 uncorrected myopic adults and compared with VA measured with subjective responses with the same stimuli and with the TACs. In experiment 2, binocular VA was determined in 19 typically developing infants aged 3 to 11 months on two visits with both the GT and TACs. RESULTS: In adults, the mean difference between VA measured by the GT and TACs was 0.01 log cycles per degree (cpd) and the 95% limits of agreement were 0.11. One hundred percent of GT VA results were within 0.5 octave of the TACs' VAs. The mean difference between the GT and TACs for infants was 0.17 log cpd on both the first and second visit (95% limits of agreement, 0.42 and 0.47, respectively). The mean difference between test and retest for infant GT VA was 0.06 log cpd, and limits of agreement for repeatability were 0.48 log cpd. In infants, both the TACs and the GT had a reliability of 89% within less than or equal to 1 octave between visits. Gaze tracking VA improved with age and is in agreement with published norms. CONCLUSIONS: The agreement between the TACs and GT in adults and infants validates the method of measuring grating acuity with the remote GT. These results demonstrate its potential for an automated test of infant VA.

The legibility of prescription medication labelling in Canada: Moving from pharmacy-centred to patient-centred labels.

INTRODUCTION: The legibility of medication labelling is a concern for all Canadians, because poor or illegible labelling may lead to miscommunication of medication information and poor patient outcomes. There are currently few guidelines and no regulations regarding print standards on medication labels. This study analyzed sample prescription labels from Ontario, Canada, and compared them with print legibility guidelines (both generic and specific to medication labels). METHODS: Cluster sampling was used to randomly select a total of 45 pharmacies in the tri-cities of Kitchener, Waterloo and Cambridge. Pharmacies were asked to supply a regular label with a hypothetical prescription. The print characteristics of patient-critical information were compared against the recommendations for prescription labels by pharmaceutical and health organizations and for print accessibility by nongovernmental organizations. RESULTS: More than 90% of labels followed the guidelines for font style, contrast, print colour and nonglossy paper. However, only 44% of the medication instructions met the minimum guideline of 12-point print size, and none of the drug or patient names met this standard. Only 5% of the labels were judged to make the best use of space, and 51% used left alignment. None of the instructions were in sentence case, as is recommended. DISCUSSION: We found discrepancies between guidelines and current labels in print size, justification, spacing and methods of emphasis. CONCLUSION: Improvements in pharmacy labelling are possible without moving to new technologies or changing the size of labels and would be expected to enhance patient outcomes.

Status of Vision and Eye Care Among Patients in Rehabilitation Hospital Units: A Cross-Sectional Study.

OBJECTIVES: The prevalence of vision disorders is high among geriatric and hospital inpatient populations, yet they often go undetected, resulting in consequences such as falls or prolonged recovery time. A needs assessment study was conducted to investigate levels of vision and the potential prevalence of unmanaged/undiagnosed ocular disorders among adult inpatients in a hospital-based rehabilitation unit. DESIGN: Cross-sectional study. SETTING & PARTICIPANTS: Inpatient rehabilitation units of an acute care hospital system in Ontario, Canada. Adults (n = 112) in a hospital inpatient rehabilitation unit participated from October 2018 to February 2019. METHODS: Participants were surveyed regarding their demographic, ocular, and medical data and spectacle wear. Visual acuity, contrast sensitivity, visual fields, and stereoacuity plus the spectacle condition were directly assessed. RESULTS: The majority (75%) were found to have reduced habitual vision while in hospital. Nearly 60% of participants reported at least some difficulty reading a newspaper or distinguishing a face or were "not happy with their vision." This was despite 80% of participants reporting that they had an eye care practitioner and 70% that they had an eye examination within the last 2 years. More than half (51.8%) of the participants received the recommendation to follow up with their eye care practitioner on discharge from the hospital. CONCLUSIONS AND IMPLICATIONS: Reduced vision and vision disorders has a high prevalence among hospital patients in rehabilitation units and should be evaluated at or soon after hospital intake. By incorporating vision screening tools, necessary precautions may be taken to avoid possible falls and promote recovery.

Measuring recognition visual acuity in young children - testability with the Waterloo Differential Acuity Test (WatDAT).

CLINICAL RELEVANCE: Visual acuity measurement is important for the detection and monitoring of eye disorders. Developing accurate and sensitive visual acuity tests suitable for young children is therefore desirable. BACKGROUND: Recognition or form visual acuity (VA), which is measured with matching in children aged 3 years and up, is more sensitive for detecting visual deficits compared to resolution VA. The Waterloo Differential Acuity Test (WatDAT) is a proposed recognition VA test using the concept of identifying the "odd one out" among distractors. The WatDAT is expected to be cognitively easier than matching tests and therefore may be used in younger children. The purpose of this study is to investigate the testability of the WatDAT paradigm in children aged 12-36 months, and to determine the optimum format and number of distractors. METHODS: Fifty-one typically-developing children aged 12-36 months participated in the study. Data for Patti Pics (PP) and Face targets (FT) were collected for formats with 3, 4 and 5 distractors. The targets were presented binocularly on a computer touch screen at 30 cm. The task was to touch the face among identical non-faces or a house among circles. Following initial training, there were 5 presentations for each distractor format. Testability was defined as correctly identifying at least 4/5 presentations and was also determined for uncrowded PP symbols using matching. RESULTS: Of participants aged 18-36 months, 87% could perform the WatDAT PP targets with 3 distractors compared to 68% for the FT, while 48% could perform matching with PP. The testability for FT increased to 85% for children ≥22 months. Younger children showed lower testability. For the 3 distractor format, PP targets gave 9% testability in children 12 to <18 months, and FT gave a testability of 16% in children 12 to <22 months. CONCLUSION: WatDAT testability is higher than matching VA tests. This indicates that the newly developed WatDAT has potential for measuring recognition VA in children 18 months and older.

Validation of the Waterloo Differential Visual Acuity Test (WatDAT) and Comparison With Existing Pediatric Tests of Visual Acuity.

Purpose: The new Waterloo Differential Acuity Test (WatDAT) is designed to allow recognition visual acuity (VA) measurement in children before they can typically undertake matching tests. The study purpose was to validate WatDAT in adults with normal and reduced VA. Methods: Eighty adults (18 to <40 years of age) participated (32 normal VA, 12 reduced VA, and 36 simulated reduced VA). Monocular VA was measured on two occasions in random order for WatDAT (versions with 3 and 5 distractors for Faces and Patti Pics house among circles), Lea Symbols, Kay Pictures and Patti Pics matching tests, Teller Acuity Cards, Cardiff Acuity Test, and Early Treatment Diabetic Retinopathy Study (ETDRS) letter chart. Pediatric tests were validated against ETDRS using limits of agreement (LoA), sensitivity, and specificity. The LoA for repeatability were also determined. Results: WatDAT showed minimal bias compared with ETDRS, and LoAs, which were similar to pediatric matching tests (0.241-0.250). Both preferential looking tests showed higher bias and LoAs than ETDRS. Matching tests showed good agreement with ETDRS, except for Kay Pictures and Lea Uncrowded test, which overestimated VA. WatDAT showed high sensitivity (>0.96) and specificity (>0.79), which improved with criterion adjustment and were significantly higher than for the preferential looking tests. LoA for repeatability for WatDAT 3 Faces and WatDAT 5 Faces were comparable with the ETDRS. Conclusions: WatDAT demonstrates good agreement and repeatability compared with the gold-standard ETDRS letter chart, and performed better than preferential looking tests, the alternative until a child can undertake a matching VA test. Translational Relevance: Good validity of the Waterloo Differential Acuity Test was demonstrated in adults as a first step to showing its potential for detecting childhood visual disorders.

Effects of sweep VEP parameters on visual acuity and contrast thresholds in children and adults.

BACKGROUND: There are many parameters that may impact the thresholds obtained with sweep visually evoked potentials (sVEP), yet a number of these parameters have not been systematically studied, and there is no recognised standard for sVEP recording. In this study, the effects of electrode placement, temporal frequency, sweep direction, presence of a fixation target, stimulus area, and sweep duration on visual acuity (VA) and contrast thresholds of the sVEP were investigated. Additionally, the effect of these parameters on the number of viable threshold readings obtained from five active electrodes was investigated. METHODS: Participants were six children (aged 6-8 years) and six adults (aged 17-30 years) with normal vision. Binocular sVEP VA and contrast thresholds were measured for two electrode placements (ISCEV and PowerDiva) of five active electrodes, three temporal frequencies (6, 7.5, and 10 Hz), two sweep directions (low to high and high to low), presence or absence of a fixation target, three stimulus areas, and three sweep durations. RESULTS: There were differences between adults and children with respect to visual acuity, the adults having better VA than the children (p = 0.033 in experiment 2). Overall, there were more viable readings at 7.5 Hz than at either 10 or 6 Hz (p = 0.0014 for VA and 0.001 for contrast thresholds). The adults performed better (in terms of viable readings) with the fixation target than without it (p = 0.04). The smallest stimulus size used gave rise to fewer viable readings in both adults and children (p = 0.022 for VA and 0.0001 for contrast thresholds). The other parameters (electrode placement, sweep direction and sweep duration) did not give rise to significant differences. CONCLUSIONS: A temporal frequency of 7.5 Hz, a stimulus area of 4° or larger for VA and 10° or larger for contrast thresholds, and the use of a fixation target gave more viable readings, and may be indicated for future application. Consideration of the number of viable readings showed more differences between parameters than the actual thresholds, and it is suggested that more readings presumably would yield more reliable threshold measurements.

Prescribing for hyperopia in childhood and teenage by academic optometrists.

PURPOSE: The purpose of this study was to examine the prescribing patterns of academic optometrists for infants, children, and teenagers with hyperopia and the factors that affected the decision to prescribe. A comparison was made to published guidelines for prescribing for hyperopia in children. METHODS: The Waterloo Eye Study (WatES) database is a database of all patients attending the Primary Care Clinic or the Pediatric Clinic at the School of Optometry, University of Waterloo, between February 2007 and January 2008. Records for 698 patients aged from birth to 19 years with hyperopia but without strabismus or significant anisometropia were extracted. They were analyzed to determine the factors that predicted whether a child was prescribed spectacles and the 50% prescribing points for hyperopia and astigmatism according to age. RESULTS: Univariate analysis showed that the level of hyperopia, astigmatism, age, distance, and near phoria and presence of symptoms were associated with the prescription of spectacles (p < 0.05). Multivariate analysis showed that the prescription of spectacles was predicted by age, highest sphere (either right or left eye), highest cylinder, the presence of symptoms, and distance phoria. Among 0 to 3 year olds, all the children with 5 D or more of hyperopia had been prescribed spectacles. Among the 4 to 6 year olds, this point was 3.25 D; and for the 7 to 19 year olds, it was 2.25 D. The levels at which 50% of the population had been prescribed spectacles was 3.7, 1.8, and 1.1 D for the 0 to 3 year olds, 4 to 6 year olds, and 7 to 19 year olds, respectively. There was frequently a difference between the refraction and the prescription such that the younger children, in particular, were often under corrected for both hyperopia and astigmatism. CONCLUSIONS: The optometrists in this academic setting appear to follow the available optometric guidelines for prescribing for hyperopia. They tend to prescribe for lower levels of hyperopia than U.S. ophthalmologists.

Towards developing a test of global motion for use with Paralympic athletes.

The Paralympic classification system for visual impairment only assesses static visual acuity and static visual field despite many Paralympic sports being dynamic in nature. As a first step towards determining whether motion perception tests should be used in Paralympic classification, we assessed whether motion coherence thresholds could be measured when visual acuity or visual fields were impaired at levels consistent with the current Paralympic classification criteria. Visual acuity and visual field impairments corresponding to Paralympic classification criteria were simulated in normally sighted individuals and motion coherence thresholds were measured. Mild-to-moderate visual acuity impairments had no effect on motion coherence thresholds. The most severe Paralympic class of acuity impairment (≥2.6 logMAR) significantly elevated thresholds. A trend towards superior motion coherence thresholds in the peripheral visual field compared to the central visual field was also present. Global motion perception appears to be measurable under simulated visual impairments that are consistent with the Paralympic classification. Poorer global motion perception was found for visual acuities >2.6 logMAR and visual fields <10° in diameter. Further research is needed to investigate the relationship between global motion perception and sports performance in athletes with real visual impairment.