Canadian Optometric Low Vision: Predictive Factors and Regional Comparisons

Purpose: To investigate the regional differences in low vision (LV) provision across Canada and to identify predictive factors for the provision of more extensive low vision services (LVS). Methods: Practising optometrists across Canada were invited to participate in a questionnaire that investigated personal and practice demographics, levels of LVS offered, patterns of referrals and barriers to provision of LVS. Results: 459 optometrists responded. Predictive factors for providing more extensive LVS included: optometrists with >15 years of practice, having a local LV optometrist/ophthalmologist within one day’s travel, not having a multi-disciplinary LV clinic within one-day’s travel, working in a practice in a population of <50,000, and having 2+ optometrists in the same practice. Regional differences were found in the following variables: the presence of an optometrist offering LVS within the respondent’s primary practice, referral criteria, the type of LV provider receiving the referral, and the perceived quality of LVS. Conclusions: LVS are provided differently across Canada and the availability of government-funded LVS appeared to enhance optometric referrals to multidisciplinary low vision clinics. Optometrists who were in a group practice setting, who had practiced for >15 years and who worked in a less populated area were more likely to provide more extensive LVS

Guide de pratique clinique 2020 de l’ACO : Réadaptation optométrique de la basse vision Sommaire

Le Guide de pratique clinique en basse vision a pour but d’aider les optométristes canadiens à fournir des soins optimaux de réadaptation aux patients atteints de déficience visuelle. Le Guide de pratique est fondé sur les meilleures données probantes disponibles, interprétées par un groupe d’experts. Le groupe de rédaction est composé d’optométristes du milieu universitaire et de la pratique privée, représentant diverses régions du Canada. Le Guide de pratique aidera les optométristes à identifier les patients qui ont besoin d’une réadaptation de la basse vision. Il recommande une évaluation et une prise en charge appropriées

Role of Primary Care Optometrists in the Assessment and Management of Patients with Traumatic Brain Injuries in Canada

Traumatic brain injury (TBI) results from a strong blow or jolt to the head that disrupts the normal function of the brain.1 The severity of a TBI can range from mild to severe, depending on the patient’s mental status, con-sciousness level and amnesia following the injury. The annual incidence of TBI in North America and Europe is conservatively estimated to be ap-proximately 600/100,000.2,3 This translates to at least 200,000 TBI cases in Canada every year. According to the Centers for Disease Control and Prevention, and the Canadian Institute for Health Information, the leading cause of TBIs that result in hospital admission is falls (35%-45%), followed by motor vehicle accidents (17%-36%), collision-related events (struck by or against) (10-17%) and assaults (9-10%).4,5 Head injuries are more common in the 0- to 19-year age group, followed by those who are aged 60+. Males are more highly represented in every age group than females. However, it should be noted that the demographics of patients who present in an op-tometrist’s office may differ from those based on hospital admissions [...

Generic and customised digital image enhancement filters for the visually impaired

AbstractThis study compares the effectiveness of various image enhancement filters for improving the perceived visibility of coloured digital natural images for people with visual impairment. Generic filters were compared with Peli’s adaptive enhancement and adaptive thresholding and custom-devised filters based on each subject’s contrast sensitivity loss. Subjects with low vision made within filter rankings followed by between filter ratings. In general, subjects preferred filters with lower gains. Unsharp masking resulted in a significant increase in perceived visibility for some image types (p⩽0.05) while Peli’s adaptive enhancement, edge enhancement and histogram equalization resulted in borderline improvements. Adaptive thresholding and the custom devised filter did not result in overall improvements in perceived visibility

Suprathreshold contrast matching in maculopathy

PURPOSE. To compare suprathreshold contrast perception among three groups of participants with maculopathy (atrophic age-related macular degeneration [ARMD], exudative ARMD, and juvenile macular dystrophy [JMD]) and to compare suprathreshold contrast matching between controls and subjects with maculopathy. METHODS. Three groups of subjects with macular disorders (13 atrophic ARMD, 14 exudative ARMD, and 8 JMD) and one group of control subjects (15 subjects 50 years and older) participated. Contrast sensitivity (CS) up to 8.53 cycles per degree (cpd) was measured with a temporal two-alternative forced-choice staircase procedure. Suprathreshold contrast matching was measured using a method of limits. A 0.58 cpd sine-wave grating was the standard; the subject was asked to match the contrast of gratings of different spatial frequencies. RESULTS. Subjects with maculopathy showed marked deficits of contrast threshold. Suprathreshold contrast constancy was shown, though deficits were observed in absolute matches compared with control subjects. The slopes of matched contrast against standard contrast for the subjects with maculopathy were significantly different from those for the controls, and these differences were in the direction that implies compensation for differences in thresholds. There were no significant differences among the three groups of subjects with maculopathy. CONCLUSIONS. In this study, the authors observed a degree of contrast constancy in subjects with maculopathy, though there were still deficits compared with control subjects. This is discussed in terms of gain of the visual system adjusting to compensate for CS losses (though incompletely) or contrast overconstancy, present in normal peripheral vision, which helps to compensate for CS loss. (Invest Ophthalmol Vis Sci

Canadian clinical guidelines for periodic eye examinations in children aged 0-5 years: Have we got it right?

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Reading in children with low vision

There have been numerous and extensive studies into the visual requirements for reading in adults with low vision. There are far fewer studies involving children with low vision. This article compares the studies on children which do exist with the findings in adults. Acuity reserve (magnification), contrast reserve and visual field requirements are considered. We also review the literature which compares the efficacy of large print with optical magnification for children. From the few studies that exist, there are indications that the requirements for children are not the same as for adults. Therefore, we suggest that one cannot directly apply the results from adults to children and that there is a gap in the literature (and therefore our understanding) of the visual requirements for reading in children

Quantitative assessment of perceived visibility enhancement with image processing for single face images: a preliminary study

PURPOSE. To develop a method to quantitatively assess the visibility enhancement of single face images gained with digital filters for people with maculopathy. To apply this method to obtaining preliminary results of visibility enhancement with subjectively preferred filters for people with maculopathy. METHODS. Six subjects with normal vision and two with maculopathy were required to recognize seven facial expressions of single face images with different display durations of 2 seconds, 1 second, and 0.73 second. As a result, four facial expressions (anger, disgust, fear, and sadness) and a display duration of 0.73 second were chosen to measure single face image visibility enhancement with subjectively preferred digital filters. Finally, nine subjects with maculopathy viewed 30 images with four facial expressions that were either unfiltered or filtered with subjectively preferred digital filters. Each subject was required to identify the facial expression in a fouralternative, forced-choice paradigm. The errors with original and filtered images were calculated. RESULTS. The method with four facial expressions and display duration of 0.73 second prevented a ceiling effect. The nine subjects with maculopathy made significantly fewer errors with the filtered images than with the original ones images (P ϭ 0.004). CONCLUSIONS. The developed method was effective in objective (quantitative) measurement of the enhancement in image visibility with digital filtering for people with maculopathy. There is a measurable improvement in facial expression recognition with subjectively preferred filters. The facial expression recognition task developed and validated in the present study is recommended as a method to be used in future studies of enhancement of face images. (Invest Ophthalmol Vis Sci

Visual impairment and the useful field of vision

The aim of this study was to measure the useful field of vision (UFoV) in people with visual impairment and to compare results with clinical measures of vision. UFoV, visual acuity, contrast sensitivity and visual fields were measured in 36 participants with low vision and 22 age-matched controls in two age groups. For both the low vision and control groups the presence of distractors (cluttered field) increased the error rates on our UFoV measure but there was no significant effect of the presence of a central task (divided attention). Participants with low vision made more errors on UFoV than did controls, but this difference disappeared once their visual field defects were accounted for. By multiple regression analysis, age, visual fields and contrast sensitivity were shown to predict the different UFoV scores. As for observers with normal vision, standard clinical visual field tests may not fully describe the difficulties that may be encountered by people with visual impairment undertaking tasks in the cluttered environments and multiple demands of everday life

Effect of age and pop out distracter on attended field of view

Purpose: To investigate the functional field of view (FFOV) of younger and older individuals using the attended field of view (AFOV), a method which allows for eye and head movement. The impact of a pop out distracter and a dual task on the FFOV measure was also investigated. Methods: Nine young adult (25 ± 6 years) and 9 older participants (72 ± 4 years) took part in the experiment. The AFOV test involved the binocular detection and localization of a white target (Landolt-C) in a field of 24 white rings (distracters). The further AFOV tests were modified to include the presence of a pop out distracter, a dual task condition, and a combination of the two. Results: Older observers had lower viewing efficiency (log [1/presentation time]) in all conditions (pooled mean across conditions: older: 0.05 ± 0.02; younger: 0.48 ± 0.04) than the younger group. The addition of dual or a pop out distracter did not affect the older group (mean difference ∼104 ± 150 ms and ∼124 ± 122 ms respectively) but the additional pop out distracter reduced the efficiency of the younger group for targets near fixation (mean difference ∼68 ± 35 ms). Conclusion: Better viewing efficiency was observed in younger individuals compared to older individuals. Difficulty in disregarding irrelevant stimuli and thereby resorting to inefficient search strategy is proposed as the reason for the differences. The finding that both older and younger individuals are not affected significantly by the presence of the irrelevant pop out distracter has implications in situations such as driving or hazard avoidance. In such scenarios, search performance is likely not impaired beyond what is found with distracters (visual clutter) in the environment