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Purpose: Morphological retinal changes combined with functional evidence implicate hypoxia in the pathogenesis of age-related macular degeneration (AMD). However, the role of hypoxia in the scotopic threshold deficit reported in AMD has not been investigated. This study compared scotopic thresholds in participants with early and intermediate AMD recorded under conditions of systemic hypoxia, hyperoxia and normoxia.\ud \ud Materials and Methods: Over two sessions scotopic thresholds were measured with participants breathing 21% and 60% oxygen (n = 12 early AMD, n = 11 age-similar controls) or 21% and 14% oxygen (n = 16 early AMD, n = 20 age-similar controls). Thresholds were measured using a 'white', annular 12 degrees stimulus, using a QUEST procedure.\ud \ud Results: There was no statistically significant change in scotopic thresholds within the AMD or control group when breathing the hyperoxic gas mixture (60% oxygen) or the hypoxic gas mixture (14% oxygen) when compared to the normoxic condition (21% oxygen). There was also no statistically significant difference in scotopic thresholds between groups under the hyperoxic or hypoxic gas conditions. The difference between groups under the normoxic condition was not statistically significant for the hyperoxia study (p = .70), but did reach significance in the hypoxia study (p = .05).\ud \ud Conclusion: This study provided no evidence that breathing that breathing 14% or 60% oxygen altered scotopic thresholds in those with early AMD when compared to controls. However, the lack of elevated scotopic thresholds in the AMD group of the hyperoxia study is of note, as it is unlikely that hyperoxia would reduce thresholds which were not significantly raised at baseline, regardless of whether hypoxia was a factor in the disease pathogenesis. The findings of this study do not rule out a role for hypoxia in early AMD, but this needs to be assessed in future experiments using measures that differ significantly between people with AMD and controls.

Purpose: The purpose of this study was to undertake a systematic literature review on how vision enhancements, implemented using head-mounted displays (HMDs), can improve mobility, orientation, and associated aspects of visual function in people with low vision.\ud\udMethods: The databases Medline, Chinl, Scopus, and Web of Science were searched for potentially relevant studies. Publications from all years until November 2018 were identified based on predefined inclusion and exclusion criteria. The data were tabulated and synthesized to produce a systematic review.\ud\udResults: The search identified 28 relevant papers describing the performance of vision enhancement techniques on mobility and associated visual tasks. Simplifying visual scenes improved obstacle detection and object recognition but decreased walking speed. Minification techniques increased the size of the visual field by 3 to 5 times and improved visual search performance. However, the impact of minification on mobility has not been studied extensively. Clinical trials with commercially available devices recorded poor results relative to conventional aids.\ud\udConclusions: The effects of current vision enhancements using HMDs are mixed. They appear to reduce mobility efficiency but improved obstacle detection and object recognition. The review highlights the lack of controlled studies with robust study designs. To support the evidence base, well-designed trials with larger sample sizes that represent different types of impairments and real-life scenarios are required. Future work should focus on identifying the needs of people with different types of vision impairment and providing targeted enhancements.\ud\udTranslational Relevance: This literature review examines the evidence regarding the ability of HMD technology to improve mobility in people with sight loss.

Purpose: To assess the topographic relationship between the photopic negative response (PhNR) and retinal ganglion cell distribution in healthy individuals. \ud \ud Method: Data was recorded from 16 healthy participants. The amplitude of PhNRs obtained in response to focal long duration (250 ms) and brief flash (5 ms), red (660 nm) on blue (469 nm) stimuli of increasing size (5° - full field) were measured. The number of retinal ganglion cell receptive fields (RGCf) in each stimulus area was established from the literature and regression analysis used to determine the relationships between: PhNR amplitude and number of RGCfs stimulated, PhNR density and the RGCf density and response per RGCf as a function of eccentricity.\ud \ud Results: The overall amplitude of the PhNR increased with stimulus size and the response density declined from ∼0.1 μV/deg in the macular region to ∼0.003 μV/deg approximately 45° from the fovea. Contrary to expectations, the relationship between the PhNR and number of RGCf was nonlinear, the response from more eccentric neurons being about three times greater than those in the macular region.\ud \ud Conclusions: Although the amplitude of the PhNR broadly maps on to the topographic distribution of RGCf the increase in PhNR amplitude with increasing eccentricity is only partly explained by RGCf numbers. Increases in the PhNR amplitude may be due to topographic variations in the contributions from other non-RGC neurons, as well as eccentricity-related morphologic and physiologic differences in RGCs.

Microperimetry is a novel technique for assessing visual function that appears particularly suitable for age-related macular degeneration (AMD). Compared with standard automated perimetry, microperimetry offers several unique features. It simultaneously images the fundus, incorporates an eye-tracking system to correct the stimulus location for fixation loss, and identifies any preferred retinal loci. We identified 52 articles that met the inclusion criteria for a systematic review of microperimetry in the assessment of visual function in AMD. We discuss microperimetry and AMD in relation to disease severity, structural imaging outcomes, other measures of visual function, and evaluation of the efficacy of surgical and/or medical therapies in clinical trials. The evidence for the use of microperimetry in the functional assessment of AMD is encouraging. Disruptions of the ellipsoid zone band and retinal pigment epithelium are clearly associated with reduced differential light sensitivity despite the maintenance of good visual acuity. Reduced differential light sensitivity is also associated with outer segment thinning and retinal pigment epithelium thickening in early AMD and with both a thickening and a thinning of the whole retina in choroidal neovascularization. Microperimetry, however, lacks the robust diffuse and focal loss age-corrected probability analyses associated with standard automated perimetry, and the technique is currently limited by this omission.

PURPOSE: To evaluate the inter-session repeatability of the Colour Assessment and Diagnosis (CAD) test and a novel 14-Hz flicker test in a population of healthy participants in order to provide benchmark data for their use as functional biomarkers for age-related macular degeneration (AMD). METHODS: Visual function was assessed using both techniques in 30 healthy adults (mean age 36.3 ± 14.1 years) on 2 separate days. Inter-session repeatability of RG and YB CAD thresholds and 14-Hz flicker thresholds was assessed by determining their coefficient of repeatability (CoR). RESULTS: The CoR was calculated to be 0.39 CAD units (17.0%) for RG thresholds, 0.43 CAD units (31.1%) for YB thresholds and 0.015 (53.4%) for 14-Hz flicker contrast thresholds. On average, thresholds improved by 4.72% (RG), 6.33% (YB) and 13.3% (14-Hz flicker) between visits 1 and 2, suggesting a small but consistent learning effect. The CoR for all parameters was relatively small compared to the mean thresholds obtained (RG: mean 2.27 ± 4.58, CoR 0.39; YB: mean 1.37 ± 0.55, CoR 0.43; 14-Hz flicker: mean 0.028 ± 0.01, CoR 0.015). CONCLUSIONS: This study has described the repeatability of the CAD and 14-Hz flicker tests. The data can help clinicians decide if the results from repeated measures are of clinical significance. Despite pre-test training, there was some evidence of a learning effect. Therefore, clinical trials using these techniques should ensure training is sufficient to minimize these effects.

Purpose: The “traffic light” color designation of differential light sensitivity used in a number of microperimeters does not encompass the conventional Total and Pattern Deviation probability analyses adopted by standard automated perimetry. We determined whether the color designation is indicative of abnormality as represented by the “gold standard” Pattern Deviation probability analysis. Methods: Total and Pattern Deviation probability levels, using two different methods, were derived at each of 40 stimulus locations, within 7° eccentricity, from 66 ocular healthy individuals (66 eyes) who had undergone microperimetry with the Macular Integrity Assessment microperimeter. The probability levels were applied to the corresponding fields from each of 45 individuals (45 eyes) with age-related macular degeneration (AMD) and evaluated in relation to the color designation. Results: Sensitivities designated in orange encompassed the entire range of Pattern Deviation probability levels (from normal to P ≤ 1%). Those designated in green were mostly normal; those in red/black generally corresponded to the ≤1% probability level. Conclusions: The green and the red/black designations are generally indicative of normal and abnormal probability values, respectively. The orange designation encompassed all probability outcomes and should not be relied upon for visual field interpretation. The evidence base indicates replacement of the color designation of sensitivity in AMD by Total Deviation and Pattern Deviation analyses. Translational Relevance: The use of Total and Pattern Deviation probability analyses is not universal in all microperimeters, and the derivation of these values indicates that color coding will lead to errors in evaluating visual field loss.

Background\ud This study aimed to identify the pre-adapting light intensity that generated the maximum separation in the parameters of dark adaptation between participants with early age-related macular degeneration (AMD) and healthy control participants in the minimum recording time.\ud \ud Methods\ud Cone dark adaptation was monitored in 10 participants with early AMD and 10 age-matched controls after exposure to three pre-adapting light intensities, using an achromatic annulus (12° radius) centred on the fovea. Threshold recovery data were modelled, and the time constant of cone recovery (τ), final cone threshold, and time to rod-cone-break (RCB) were determined. The diagnostic potential of these parameters at all pre-adapting intensities was evaluated by constructing receiver operating characteristic (ROC) curves.\ud \ud Results\ud There were significant differences between those with early AMD and healthy controls in cone τ and time to RCB (p < 0.05) at all pre-adapting ‘bleaching’ intensities. ROC curves showed that the diagnostic potential of dark adaptometry was high following exposure to all three pre-adapting intensities, generating an area under the curve in excess of 0.87 ± 0.08 for cone τ and time to RCB for all conditions.\ud \ud Conclusions\ud Dark adaptation was shown to be highly diagnostic for early AMD across a range of pre-adapting light intensities, and therefore, the lower pre-adapting intensities evaluated in this study may be used to expedite dark adaptation measurement in the clinic without compromising the integrity of the data obtained. This study reinforces the suggestion that cone and rod dark adaptation are good candidate biomarkers for early AMD.

Purpose\ud \ud To systematically assess the literature on psychosocial interventions to improve mental health (i.e. depression, anxiety, mental fatigue, loneliness, psychological stress and psychological well-being) in visually impaired adults (≥18 years).\ud \ud \ud Methods\ud \ud The databases Medline, Embase and Psychinfo were searched for relevant studies, which were categorised into randomised controlled trials (RCTs), non-RCTs and before and after comparisons (BA). The Cochrane Collaboration Risk of Bias Tool was used to assess study quality. Standardised mean differences (SMD) were calculated to quantitatively summarise the outcomes of the RCTs and non-RCTs in a meta-analysis. Meta-regression was used to explore sources of heterogeneity in the data.\ud \ud Results\ud \ud The search identified 27 papers (published between 1981 and 2015), describing the outcomes of 22 different studies (14 RCTs, four non-RCTs, and four BAs). Pooled analyses showed that interventions significantly reduced depressive symptoms (SMD −0.30, 95% confidence interval (CI) −0.60 to −0.01), while effects on anxiety symptoms, mental fatigue, psychological stress and psychological well-being were non-significant. Meta-regression analyses showed homogeneity in effect sizes across a range of intervention, population, and study characteristics. Only a higher age of participants was associated with less effective results on depressive symptoms (b = 0.03, 95% CI 0.01 to 0.05), psychological stress (b = 0.07, 95% CI 0.01 to 0.13) and psychological well-being (b = −0.03, 95% CI −0.05 to 0.01). However, after removing a clear outlier the overall effect on depressive symptoms and the influence of age on depressive symptoms and psychological stress were no longer significant, while the influence of age on psychological well-being remained.\ud \ud \ud Conclusions\ud \ud There is currently only limited evidence for the effectiveness of psychosocial interventions in the field of low vision. More well-designed trials are needed with specific attention for interventions tailored to the needs of elderly patients.

The purpose of the study was to identify the educational, social and leisure activities and issues that matter to school children and young people with a visual impairment and to compare their lifestyle with fully sighted counterparts. Thirteen focus groups were conducted and the groups were stratified by age, gender, visual status and school location (urban and non-urban). The sessions were audio taped, transcribed verbatim, coded using NVivo software and a qualitative data analysis was carried out to identify the main themes. Eighty-one children and young people aged between 5–18 years participated in the focus groups; 34 were visually impaired (22 boys) and 47 were fully sighted (24 boys). In total, 121 different daily living activities important to children and young people were discussed in the focus groups. Results suggested that children and young people with a visual impairment have similar lifestyles to their fully sighted counterparts but are more restricted in some specific activities. The children and young people also reported that sometimes these restrictions were imposed by those supporting them rather than their own abilities. This information provided an in-depth understanding of the impact of visual impairment in school-aged children and young people. © 2012, SAGE Publications. All rights reserved. Refereed/Peer-reviewed

Purpose. Following exposure to a bright light that bleaches a significant portion of photopigment, the eyes take several minutes to regain sensitivity. This slow process, known as dark adaptation, is impaired in patients with age-related macular degeneration and is an important candidate biomarker for this disease. The aim of this study was to evaluate the effect of age on cone dark adaptation. Methods. Data were obtained from 41 healthy adults aged between 20 and 83 years. Pupils were dilated and 96% of cone photopigment was “bleached,” before threshold was monitored continuously for 5 min in the dark, using a 4° diameter achromatic spot centered on the fovea. Threshold recovery data were modeled, and the time constant of cone recovery ([tau]), initial cone thresholds, and final cone thresholds were determined. Regression analysis was used to determine the relationship between age and cone dark adaptation parameters. Results. Cone [tau] increased by 16.4 s/decade of life, indicating a progressive slowing of dark adaptation with increasing age. This change in cone [tau] throughout adulthood was significant (p < 0.0005). There was no significant relationship between increasing age and initial cone threshold (p = 0.84) or final cone threshold (p = 0.82). Conclusions. Our results provide evidence for age-related slowing of cone dark adaptation after a full bleach in healthy adults, which is likely to contribute to visual difficulties when moving from bright to dim photopic light levels. We propose that the sensitivity and specificity of cone [tau] as a biomarker for early age-related macular disease could be improved by taking into account the significant age-related decline in this parameter.

Background: The ERG photostress test assesses the recovery of the focal 41 Hz ERG following exposure to a bright light that bleaches a significant proportion of photopigment. The aims of this study were: 1) to compare the repeatability of the ERG photostress test recovery time constant following long and short duration light exposure, and 2) to determine the effect of age on the ERG photostress test recovery time constant.\ud \ud Methods: Focal 41 Hz ERGs were recorded from 23 participants (age range 20–71 years) at 20-second intervals for 5 minutes following either a short-duration (photoflash) or long-duration (equilibrium) light exposure. After a 5-minute wash-out period, the procedure was repeated using the second bleach modality. The time constant of cone recovery was determined by fitting an exponential model to the amplitude recovery data. The whole procedure was repeated on a second occasion. The co-efficient of repeatability (CoR) was calculated for each bleaching technique. The relationship between the time constant of recovery and age was investigated (Pearson’s correlation coefficient).\ud \ud Results: The time constant of recovery following an equilibrium bleach was more repeatable than recovery following a photoflash (CoR = 85s and 184s respectively). Eight trials (from seven participants) failed to show a reduction in amplitude following the photoflash, suggesting that a blink or fixation loss had occurred. All participants were reliably light-adapted by the equilibrium bleach. For the equilibrium bleach data, the time constant of recovery increased with age at a rate of 27 seconds per decade.\ud \ud Conclusions: The equilibrium bleach was more reliable and repeatable than the photoflash. Increasing participant age was shown to result in a lengthening of the recovery time constant, of a magnitude comparable to previously published psychophysical data.

Aims: To determine if there was a significant difference between user-centred and clinical outcomes in people with low vision who attended a new community-based low vision service (CLVS) or the hospital-based low vision service (HBLV). Methods: A prospective controlled before and after study. Participants were recruited from the CLVS (n=343; 96 male, 247 female; median age 82 years) and from the HLVS (n=145; 55 male, 90 female; median age 80 years). The primary outcome measure was change (baseline to 3 months) in visual disability as evaluated by the seven-item National Eye Institute-Visual Function Questionnaire (NEI-VFQ). Secondary outcome measures included: use of low vision aids, satisfaction with the service provided and change in near visual acuity before and after the provision of low vision aids. Results: There were no significant differences in user-centred and clinical outcome measures between the CLVS and HLVS. Self-reported visual disability was significantly reduced after low vision service intervention for participants in both groups by 0.46 and 0.57 logits in the HLVS and CLVS, respectively. Conclusion: This study provides strong evidence that CLVS and HLVS are effective methods of service provision in Wales.

Aims: To develop and validate a short questionnaire to assess self-reported visual ability in children and young people with a visual impairment. Methods: A list of 121 items was generated from 13 focus groups with children and young people with and without a visual impairment. A long 89-item questionnaire was piloted with 45 visually impaired children and young people using face-to-face interviews. Rasch analysis was used to analyse the response category function and to facilitate item removal ensuring a valid unidimensional scale. The validity and reliability of the short questionnaire were assessed on a group of 109 visually impaired children (58.7% boys; median age 13 years) using Rasch analysis and intraclass correlation coefficient (ICC). Results: The final 25-item questionnaire has good validity and reliability as demonstrated by a person separation index of 2.28 and reliability coefficient of 0.84. The items are well targeted to the subjects with a mean difference of −0.40 logit between item and person means, and an ICC of 0.89 demonstrates good temporal stability. Conclusion: The Cardiff Visual Ability Questionnaire for Children (CVAQC) is a short, psychometrically robust and a self-reported instrument that works to form a unidimensional scale for the assessment of the visual ability in children and young people with a visual impairment. Refereed/Peer-reviewed

Aim: The aim of this study was to determine whether the new, primary care based, Welsh Low Vision Service (WLVS) improved access to low vision services in Wales and was effective. Method: The impact of the WLVS was determined by measuring the number of low vision appointments; travel time to the nearest service provider; and waiting times for low vision services for 1 year before, and for 1 year after, its establishment. Change in self-report visual function (using the 7 item NEI-VFQ), near visual acuity, patient satisfaction and use of low vision aids were used to determine the effectiveness of the service. Results: Following instigation of the WLVS, the number of low vision assessments increased by 51.7%, the waiting time decreased from more than 6 months to less than 2 months for the majority of people, and journey time to the nearest service provider reduced for 80% of people. Visual disability scores improved significantly (p < 0.001) by 0.79 logits and 97.42% patients found the service helpful. Conclusions: The extension of low vision rehabilitation services into primary care identified a considerable unmet burden of need as evidenced by the substantial increase in the number of low vision assessments provided in Wales. The new service is effective and exhibits improved access.

Purpose To present a new approach for evaluating intraocular lenses (IOLs) for retinal protection from age-related lipofuscin accumulation–mediated phototoxicity. Setting Alcon Laboratories Inc., Fort Worth, Texas, USA, and Cardiff University, Cardiff, United Kingdom. Methods Age-related lipofuscin accumulation–mediated action spectra for retinal phototoxicity in an aphakic eye were created for this evaluation. Transmission curves for 6 IOLs and for cornea and spectral radiant power distribution for sunlight and 2 lamps were used. Pseudophakic action spectra and retinal phototoxicity for 3 wavelength ranges and 3 ages were computed. The percentage protection of each IOL was computed as the reduction in phototoxicity relative to the aphakic eye. Results Retinal phototoxicity increased 3.66 times from the third to ninth decade of age. The comparative retinal phototoxicity and retinal protection provided by IOLs were dependent on the light source and range of wavelength; however, unlike phototoxicity, retinal protection was independent of age. The 420 to 480 nm range was the most useful for discriminating protection by IOLs. Conclusions Retinal phototoxicity significantly increased with age; however, the retinal protection by IOLs was independent of age. The interaction between the transmission curve of IOLs and light sources required inclusion of widely used lamps besides sunlight for evaluation of IOLs. For the 420 to 480 nm wavelength range, the 3 light sources clearly discriminated the protection provided by IOLs. The AcrySof Natural IOL (Alcon) provided the highest protection consistently for the tested light sources.

Purpose. Patient anxiety has been shown to be detrimental to many aspects of primary healthcare consultations. However, to date, the subject has received minimal attention within optometric practice. Therefore, the purpose of this study was to evaluate patient anxiety during a commonly conducted type of optometric examination, namely a contact lens fit. Methods. Forty participants (15 male, 25 female; mean age 28.3 ± 9.5) underwent a full contact lens fitting consultation. Skin conductance was recorded continuously to measure participant arousal; the physiological correlate of anxiety. A short form of the Speilberger state anxiety scale was also completed by participants before and after the contact lens fit. Results. Skin conductance analysis identified arousal levels peak during history and symptoms, contact lens insertion and removal and practitioner advice. The Wilcoxen test identified a significant reduction in participant anxiety measured with the shortened Speilberger state anxiety scale after the consultation. Conclusions. Patient arousal levels fluctuate in a characteristic way throughout the contact lens fitting examination. Peak arousal levels occur during periods of ‘communicative interaction’ between the patient and the optometrist. Since anxiety is associated with poor attention, this suggests that optometrists should not assume that patients remember what they are told during the consultation. Furthermore, patient anxiety is significantly reduced after the examination, which may indicate that patient anxiety is moderated by experience.

Purpose. To describe a short, functional visual disability instrument capable of measuring the outcomes of a government funded country-wide multicenter low vision service in Wales and to determine if postal implementation might lead to response bias. Methods. Seven items from the National Eye Institute Visual Function Questionnaire (NEI VFQ), which have previously been shown to be responsive to low vision service intervention, were incorporated into a postal questionnaire which was given to patients before they attended the all Wales Low Vision Service. Rasch analysis was used to describe the instrument's psychometric properties. Results. Rasch analysis of 490 completed questionnaires showed that all seven questions worked together to form a unidimensional scale. By combining the first two response categories, category utilization and targeting was improved. There were no significant differences in the age (p = 0.29), gender (p = 0.75), distance binocular Visual Acuity (VA; p = 0.86), living situation (p = 0.34) or prevalence of macular degeneration (p = 0.31) between those who returned a completed questionnaire and those who did not. Conclusions. The seven-item National Eye Institute Visual Function Questionnaire is an appropriate and precise outcome measure that is acceptable to patients and easy to administer. It measures aspects of near, reading, and distance visual disability that have been shown to be amenable to low vision service provision and, therefore, it should be highly responsive to this intervention and facilitate inter-service assessment. We found no evidence to suggest that postal implementation results in response bias. The instrument is an appropriate measure of patient based outcomes for a large-scale, multicenter low vision service.

Purpose. Patient anxiety has been shown to be detrimental to many aspects of healthcare outcomes. To date, there is no method of evaluating anxiety in optometric practice. Therefore, the purpose of this study was the content development of a questionnaire to measure optometric patient anxiety. Such a tool will have both clinical and research application; allowing the identification of anxious patients in practice and as a method to establish the success of anxiety reducing interventions. Methods. Selection of initial items was based on patient interviews, literature review, and focus group feedback. The initial 30-item Optometric Patient Anxiety Scale was piloted on 148 patients in optometric practice. Rasch analysis was used to analyze response category operation and to facilitate item removal to ensure a valid and unidimensional scale. Test-retest reliability (test-retest time, 2 weeks) was measured on 59 young adults to test the stability of the measure with time. Results. Rasch analysis identified disordering of category thresholds and underutilization of the end-response category. Therefore, categories were merged to a three response solution. Item reduction was principally driven by infit and outfit statistics. The items in the final 10-item scale all had good infit and outfit values (infit: 0.80–1.20, outfit: 0.7–1.3), good person separation (>2) and high person and item reliability coefficients, 0.84 and 0.88, respectively. Test-retest reliability also demonstrated good stability of the measure with time (intraclass correlation; ICC = 0.85). Conclusions. The Optometric Patient Anxiety Scale is the first questionnaire to measure patient anxiety specific to optometric practice. The scale was developed using Rasch analysis to ensure that all the items work together to form a valid unidimensional interval scale.

Purpose To assess the effect of ADOA on the ON and OFF components of the photopic negative response (PhNR). Methods Twelve participants from 6 families with OPA1 ADOA and 16 age matched controls were recruited. Electrophysiological assessment involved long flash focal (20o) and full field ERGs using red flash (664 nm, 250 msec, 55 cd/m2, 2 Hz) on a rod saturating blue background (454 nm, 100 scot cd/m2); and brief xenon flash ERGs using red filter (Lee Filter “Terry Red”, max 300 µs flash duration, 1.69 cd.s.m-2, 4 Hz) over a continuous rod saturating blue background (Schott Glass Filter BG28, 206 scot cd/m2). Amplitudes (from peak and baseline to fixed time point) and implicit times of the ERG components were analysed. Results Mean amplitude (peak to fixed time) of the focal PhNR-ON were significantly (p

The scotopic ERG recorded in response to a focal stimulus has a double b-wave. The first wave results from direct focal stimulation of the retina, and the second originates in the peripheral retina in response to scattered light. The aim of this study was to assess two possible protocols for the isolation of the focal rod response, namely 'Subtraction' and 'Background Adaptation' techniques. The Subtraction technique involved the recording of a full-field response, which matched the b-wave elicited by intraocular light scatter, and the subtraction of this full-field response from the initial trace to isolate the focal component. In the Background Adaptation technique an adapting surround was used to suppress the response from the peripheral retina. Focal rod responses were isolated with both techniques. However, the Background Adaptation technique was found to more reliably elicit a focal response with a measurable a-wave, and was also considerably less time consuming than the Subtraction technique.

The development of effective means of assessing visual function in retinal disease holds the key to improved understanding of pathogenesis, and better monitoring of treatment outcomes. In diseases such as age-related macular degeneration, in which the primary locus of dysfunction is the outer retina, tests which provide a direct measure of the functional integrity of the photoreceptor/retinal pigment epithelium (RPE) complex are of great importance. Recovery of retinal function following adaptation to a bright light requires the healthy function of photoreceptors, RPE, Bruch's membrane and choroidal circulation, making an assessment of this recovery a potentially useful clinical tool. However, current techniques are either subjective in nature, or are influenced by post-retinal processing of visual information. This report describes a novel technique, the 'Dynamic Focal Cone Electro-retinogram (ERG)', which allows direct, objective assessment of the recovery of macular function following photopigment bleach. A series of 41 Hz ERGs was recorded, and ERG amplitude was plotted as a function of time following cessation of the bleach. Normative data was collected from 10 healthy subjects. For all subjects, there was no measurable ERG immediately after the bleach, but the amplitude had returned to a pre-bleach level within 4 min. The amplitude recovery data were adequately described both by an exponential recovery function and by a model based on a rate-limited recovery process. We conclude that this technique provides a clinically applicable, objective measure of outer retinal recovery.

Although anxiety is a well-established obstacle to the delivery of effective health care, there have been no attempts to measure it in the optometric consulting room. In this paper, we introduce physiological and psychological techniques that may be used to evaluate anxiety and arousal in the consulting room and present data from a small group of patients attending for a routine eye examination. Specifically, arousal was assessed before, during, and after the examination by measuring skin conductance in five patients. Anxiety was evaluated using the State-Trait Anxiety Inventory. Our data confirm the ability of these techniques to quantify arousal and anxiety in the optometric consulting room and reveal a previously unknown but important facet of the eye examination. We conclude that these techniques are suitable for use in further experimental work and may be used to identify factors capable of reducing anxiety in the optometric consulting room.

The photostress test is a simple clinical technique that can differentiate between retinal and post-retinal disease. Unfortunately a wide range of normal results have been reported in the literature and it is perhaps for this reason that the test has been little used by clinicians. The purpose of this investigation was to evaluate the effect of photostress technique, age, ametropia, pupil size and acuity on photostress recovery time (PSRT) in normal subjects. Photostress recovery time was measured in 50 healthy subjects whose ages ranged from 21 to 69 using three clinically applicable techniques and a reference technique designed to bleach a consistent amount of photopigment. The agreement between each clinical technique and the reference technique was determined. Mean photostress recovery time differed for each of the techniques studied. Analysis of the data obtained with the reference and the best clinical technique showed that age was the only factor that had a significant effect on PSRT. The best clinical technique involves exposing the eye to the light from the direct ophthalmoscope for 30 s and measuring the time taken for acuity to return to within one line of pre-bleach acuity. Photostress recovery time increases with age but is independent of pupil size, ametropia and visual acuity.

In the UK, low vision rehabilitation is delivered by a wide variety of providers with different strategies being used to integrate services from health, social care and the voluntary sector. In order to capture the current diversity of service provision the Low vision Service Model Evaluation (LOVSME) project aimed to profile selected low vision services using published standards for service delivery as a guide. Seven geographically and organizationally varied low-vision services across England were chosen for their diversity and all agreed to participate. A series of questionnaires and follow-up visits were undertaken to obtain a comprehensive description of each service, including the staff workloads and the cost of providing the service. In this paper the strengths of each model of delivery are discussed, and examples of good practice identified. As a result of the project, an Assessment Framework tool has been developed that aims to help other service providers evaluate different aspects of their own service to identify any gaps in existing service provision, and will act as a benchmark for future service development.

Background Age-related macular degeneration (AMD) is the leading cause of blindness among older adults in the developed world. The only treatments currently available, such as ranibizumab injections, are for neovascular AMD, which accounts for only 10 to 15% of people with the condition. Hypoxia has been implicated as one of the primary causes of AMD, and is most acute at night when the retina is most metabolically active. By increasing light levels at night, the metabolic requirements of the retina and hence the hypoxia will be considerably reduced. This trial seeks to determine whether wearing a light mask that emits a dim, green light during the night can prevent the progression of early AMD. Methods/design ALight is a Phase I/IIa, multicentre, randomized controlled trial. Sixty participants (55 to 88 years old) with early AMD in one eye and neovascular AMD (nAMD) in the fellow eye will be recruited from nAMD clinics. They will be randomized (in the ratio 1:1), either to receive the intervention or to be in the untreated control group, stratified according to risk of disease progression. An additional 40 participants with healthy retinal appearance, or early AMD only, will be recruited for a baseline cross-sectional analysis. The intervention is an eye mask that emits a dim green light to illuminate the retina through closed eyelids at night. This is designed to reduce the metabolic activity of the retina, thereby reducing the potential risk of hypoxia. Participants will wear the mask every night for 12 months. Ophthalmologists carrying out monthly assessments will be masked to the treatment group, but participants will be aware of their treatment group. The primary outcome measure is the proportion of people who show disease progression during the trial period in the eye with early AMD. A co-primary outcome measure is the rate of retinal adaptation. As this is a trial of a CE-marked device for an off-label indication, a further main aim of this trial is to assess safety of the mask in the cohort of participants with AMD. Trial registration International Standard Randomised Controlled Trials Register: ISRCTN82148651

The focal cone electroretinogram is a sensitive marker for macular disease, but have we unlocked its full potential? Typically assessment of waveform parameters is subjective and focuses on a small number of locations (e.g. the a-wave). This study evaluated the discriminatory and diagnostic potential of 4 conventional and 15 novel, objectively determined, parameters in patients with early Age-related Macular Degeneration. Focal cone electroretinograms were recorded in 54 participants with early Age-related Macular Degeneration (72.9±8.2 years) and 54 healthy controls (69±7.7 years). Conventional a and b wave amplitudes and implicit times were measured and compared to novel parameters derived from both the 1st and 2nd derivatives and the frequency-domain power spectrum of the electroretinogram.Statistically significant differences between groups were shown for all conventional parameters, the majority of 1st and 2nd derivative parameters and the power spectrum at 25 and 30 Hz. Receiver operating characteristics showed that both conventional and 1st and 2nd derivative implicit times had provided the best diagnostic potential. A regression model showed a small improvement over any individual parameter investigated. The non-conventional parameters enhanced the objective evaluation of the focal electroretinogram, especially when the amplitude was low. Furthermore, the novel parameters described here allow the implicit time of the electroretinogram to be probed at points other than the peaks of the a and b waves. Consequently these novel analysis techniques could prove valuable in future electrophysiological investigation, detection and monitoring of Age-related Macular Degeneration.

Purpose The global prevalence of age-related macular degeneration and associated central vision loss is rising. Central vision loss hinders the performance of many activities of daily living. Adaptive strategies such as eccentric viewing and steady eye strategy may be used to compensate for central vision loss. In order to establish the potential of these rehabilitation strategies, this systematic review evaluates current literature regarding the effectiveness of eccentric viewing and steady eye strategy training in people with central vision loss. Results The search strategies identified 2605 publications, 36 of which met the inclusion criteria for the review, but only three of which were randomised controlled trials. This literature shows that eccentric viewing and steady eye strategy training can improve near visual acuity, reading speed, and performance of activities of daily living in people with central vision loss. However, there was insufficient literature to establish a relationship between training and distance visual acuity or quality of life. There is no conclusive evidence to show that a particular model of eccentric viewing training is superior to another, little clear evidence of a relationship between participant characteristics and training outcomes and no data regarding the cost effectiveness of training. Conclusion This report highlights the need for further robust research to establish the true potential and cost effectiveness of eccentric viewing and steady eye strategy training as a rehabilitation strategy for individuals with central vision loss.

Purpose: Dark adaptometry is an important clinical tool for the diagnosis of a range of conditions, including age-related macular degeneration (AMD). In order to identify the most robust, clinically applicable technique for the measurement of cone dark adaptation, the repeatability and agreement of four psychophysical methods were assessed.\ud \ud Methods: Data were obtained from 31 healthy adults on two occasions, using four psychophysical methods. Participants’ pupils were dilated and 96% of cone photopigment was bleached before threshold was monitored in the dark using one of the techniques, selected at random. This procedure was repeated for each of the remaining methods.\ud \ud An exponential recovery function was fitted to all threshold recovery data. The co-efficient of repeatability (CoR) was calculated to assess the repeatability of the methods and a repeated measures analysis of variance (ANOVA) was used to compare mean recovery parameters.\ud \ud Results: All four methods demonstrated a similar level of inter-session repeatability for measurement of cone recovery, yielding CoRs between 1.18 and 1.56 minutes. There were no statistically significant differences in estimates of mean time constant of cone recovery (cone τ) between the four methods (p = 0.488), however significant differences initial and final cone thresholds were reported (p < 0.005).\ud \ud Conclusions: All of the techniques were capable of monitoring the rapid changes in visual threshold that occur during cone dark adaptation and the repeatability of the techniques was similar. This indicates that, despite the respective advantages and disadvantages of these psychophysical techniques, all four methods would be suitable for measuring cone dark adaptation in clinical practice.

Contact lenses can be worn in a variety of environmental conditions and do not increase the wearers risk of injury. In many situations they offer significant corneal protection. Currently firefighters are prohibited from using contact lenses. To evaluate whether contact lenses are a safe form of visual correction 50 firefighters were fitted, and examined after 1, 4 and 10 months of contact lens wear. Twenty-nine were fitted with soft contact lenses, and 21 with rigid gas permeable contact lenses. Statistically significant increase in lid sulcus hyperaemia was found in both the SCL and RGPCL groups (P < 0.01, P = 0.02, respectively), as well as an increase in hyperaemia of the vertical quadrant of the bulbar conjunctivae (P = 0.01, P = 0.02, respectively). In addition the RGPCL group showed a statistically significant increase in hyperaemia of the lateral portion of the bulbar conjunctivae (P < 0.01), consistent with exposure epitheliopathy. The SCL group showed statistically significant increase in corneal staining in the vertical quadrant for all visits (P = 0.02, P = 0.01, P = 0.02 for all visits, respectively), indicative of lens dehydration. These findings although clinically significant are not unique to firefighting, and are found within a "normal" population of contact lens wearers. In conjunction with questionnaire data (Owen et all, 1996) we conclude that soft contact lenses can be worn safely by firefighters without additional risk.

The use of contact lenses by firefighters is currently prohibited. However, many firefighters may benefit from this form of visual correction, without predisposing themselves to additional risk. Visual benefits gained by contact lens wear may increase a firefighter's safety. To determine if it is safe to allow firefighters to use contact lenses 29 were fitted with soft contact lenses and 21 with rigid gas permeable contact lenses. Questionnaires were completed prior to fitting, after 1, 4 and 10 months of contact lens wear. Both soft contact lens (SCL) wearers, and rigid gas permeable contact lens (RGPCL) wearers showed a statistically significant reduction in the frequency with which they experienced irritable foreign bodies and irritant fumes in the eyes, compared to not wearing contact lenses. Firefighters felt that their performance on the fireground had been improved by the use of contact lenses. SCL wearers also benefited from a reduction in the frequency with which they experienced watery eyes and ocular discomfort. There were significantly fewer problems encountered with SCL wearers than RGPCL wearers. The frequency with which firefighters experienced lenses falling out, lens displacement, watery eyes, ocular discomfort, and operational difficulties was significantly less for the SCL group than the RGPCL group. SCL appear to offer considerable benefits for firefighters with refractive error, but their use cannot be sanctioned without assessment of their effect on the ocular adnexa.

When a spectacle wearer enters a warm environment after having been in a cooler one, his/her spectacles may 'mist up' due to the formation of condensation on the lens surface. Both the physical properties of the spectacle lens and a number of environmental factors determine how long spectacles take to demist. The relative misting performance of crown glass, CR39 and polycarbonate spectacle lenses were assessed using a novel technique. A box in which the environmental conditions could be controlled was used first to cool the lens and then to warm it. This change in temperature caused condensation to form on the lens surface. By projecting the image of a grating through the lens onto a linear array of photodiodes it was possible to measure the contrast transmission of the spectacle lens as it demisted. Each lens type misted and demisted in a characteristic way. The polycarbonate lens demisted more rapidly than the CR39 lens which, in turn, demisted more rapidly than the glass lens. This indicates that polycarbonate spectacle lenses should be used in conditions where the adverse effects of spectacle misting need to be minimised.

Despite the fact that firefighting has been shown to be a visually demanding occupation, the present visual standards for firefighters prohibit the use of spectacles or contact lenses operationally. To determine the proportion of the UK fire service currently using spectacles and contact lenses, and how many may benefit from optical correction, a questionnaire was distributed. This contained 30 questions and was sent to 1550 firefighters. The data from 1064 returned questionnaires have been analysed. The results show that approximately 20% of those serving in the fire service have used an optical correction at some time in their lives. When not working, approximately 6% of firefighters wear spectacles for distance vision and 15% wear them for reading. Only 0.4% of firefighters use contact lenses. Half of this contact lens wearing group use their lenses while on operational duty. In total, approximately 2% of firefighters use an optical correction for operational duties. The results indicate that a high visual standard at the time of entry into an occupation cannot guarantee good vision throughout an individual's career. In addition, an estimated 11 000 firefighters in the UK, who have spectacles or contact lenses, do not use them for operational duties. The present visual standards prevent this group of firefighters from obtaining their optimal visual performance at work.

Purpose. Despite widespread agreement that dark adaptation is abnormal in age-related maculopathy (ARM), the optimal retinal location for detection of this deficit is unclear. We quantified the diagnostic potential of cone dark adaptation as a function of retinal eccentricity and compared this with the diagnostic potential of the time to the rod-cone-break (RCB). Methods. Cone dark adaptation was monitored after an 80% cone photopigment bleach in 10 subjects with ARM and 10 age-matched controls, using four achromatic annuli (0.5, 2, 7, and 12° radius) centered on the fovea. Threshold recovery data were modeled and the time constant of cone recovery (τ), final cone threshold, and time to RCB were determined. Diagnostic potential was evaluated by constructing receiver operating characteristic curves for these parameters. Results. Cone τ was significantly longer for the ARM group at 2, 7, and 12°. The greatest difference between groups was observed at 12° from fixation. At this location, the mean τ was 3.49 (±2.02) min and 0.64 (±0.38) min for ARM and control subjects, respectively (p = 0.002), and time to RCB was 17.68 (±5.37) min and 9.05 (±2.11) min for ARM and control subjects, respectively (p = 0.001). Correspondingly, receiver operating characteristic curves showed that the diagnostic potential of dark adaptometry is greatest for stimuli presented 12° from fixation; for cone τ, the area under the curve = 0.99 ± 0.02 and for time to RCB, area under the curve = 0.96 ± 0.04. Conclusions. This study has shown cone-mediated dark adaptation to be significantly impaired in ARM. Our results provide compelling evidence in support of the diagnostic potential of cone dark adaptation and the use of annular stimuli at 12°. The observation that cone τ is highly diagnostic at this eccentricity is significant clinically because this parameter may be quantified within a few minutes.

Purpose: To compare retinal thickness and choroidal thickness at increasing retinal eccentricity in individuals with early age-related macular degeneration (AMD) and in healthy controls using enhanced choroidal penetration, 3-dimensional optical coherence tomography at 1060 nm.\ud \ud Design: Cross-sectional study.\ud \ud Methods: Individuals with early AMD (n = 16; mean age, 71.6 ± 8.5 years) and a comparison group of healthy controls (n = 16; 67.6 ± 5.4 years) were recruited. Three-dimensional (20 degrees × 20 degrees) long-wavelength optical coherence tomography (1060 nm) images (approximately 8-μm axial resolution; 47 000 A scans/second, centered on the fovea) were obtained from all participants after pupil dilation. Retinal thickness was measured between the inner limiting membrane and the retinal pigment epithelium. Choroidal thickness was measured between the retinal pigment epithelium and the choroid–scleral interface. Thickness measurements were obtained subfoveally and at 0.5-mm intervals to a maximum of 2.0 mm nasally, temporally, superiorly, and inferiorly. The main outcome measures were retinal and choroidal thickness (measured in micrometers) at different eccentricities on vertical and horizontal meridians.\ud \ud Results: Mean retinal thickness was reduced significantly in the group of participants with early AMD compared with the control group at multiple locations within 2.0 mm of the fovea. This difference was most significant at the fovea, where the mean retinal thickness of the early AMD group was 179 ± 27 μm and that of the control group was 202 ± 18 μm (P = .008). There was no significant difference in choroidal thickness between groups at any location.\ud \ud Conclusions: Retinal thickness is reduced in early AMD, but choroidal thickness seems to be unaffected by the early disease process.

To assess the inter-session repeatability of the Goldmann-Weekers adaptometer for the measurement of cone dark adaptation in a population of healthy subjects. Data were obtained from 31 healthy adults (mean age 21.5 ± 2.5) on 2 days. At each visit, pupils were dilated and a 96% bleach of cone photopigment was administered to the test eye before threshold was monitored continuously for 5 min in the dark using the Goldmann-Weekers adaptometer. A single exponential function was fitted to the threshold recovery data on a least squares basis. The coefficient of repeatability (CoR) was calculated to assess the repeatability of the time constant of recovery (τ), initial threshold and final threshold. Cone dark adaptation functions were successfully recorded from all subjects on both visits. The CoR was 79.48 s for τ, 0.71 log cdm(-2) for the initial threshold, and 0.58 log cdm(-2) for the final threshold. Paired samples t-tests showed that there were no significant differences between visits for any of the parameters assesed. Although the Goldmann-Weekers adaptometer was capable of monitoring the rapid changes in threshold that occur during cone dark adaptation, the CoR for τ was relatively large compared to the mean recovery time constants (126.48 ± 40.33 and 119.94 ± 33.25 s at the first and second visits, respectively). This indicates that the Goldmann-Weekers adaptometer is unlikely to be a useful instrument to chart changes in an individual's vision over time.

Age is known to affect sensitivity to retinal motion. However, little is known about how age might affect sensitivity to motion during pursuit. We therefore investigated direction discrimination and speed discrimination when moving stimuli were either fixated or pursued. Our experiments showed: (1) age influences direction discrimination at slow speeds but has little affect on speed discrimination; (2) the faster eye movements made in the pursuit conditions produced poorer direction discrimination at slower speeds, and poorer speed discrimination at all speeds; (3) regardless of eye-movement condition, observers always combined retinal and extra-retinal motion signals to make their judgements. Our results support the idea that performance in these tasks is limited by the internal noise associated with retinal and extra-retinal motion signals, both of which feed into a stage responsible for estimating head-centred motion. Imprecise eye movement, or later noise introduced at the combination stage, could not explain the results.

The registration process was established to ensure that appropriate support was provided to those who needed it, but are the current visual acuity guidelines for registration fit for purpose? The Blind Person's Act (1920) and the National Assistance Act (1948) developed a method of identifying people who had a sight impairment and providing local authority funded rehabilitation services for them. Later, low-vision rehabilitation services were established in the Hospital Eye Service,1 and now the hospital and local authority services should work together to provide holistic support for people losing their sight.2 A report funded and published by the Thomas Pocklington Trust3 on an analysis of people using an “open-access” rehabilitation service in Wales4 suggests that the registration guidance is no longer fit for purpose. This large data set (n=5817) provides a unique insight into registration because it includes a large number of people who are not registered but who have a sight impairment and are using rehabilitation services.

Purpose. Patient anxiety has been shown to be detrimental to healthcare consultations and their outcomes. To date, little is known about the causes of patient anxiety in optometric practice. Therefore, the purpose of this study was to identify the predictors of state anxiety for patients attending optometric consultations. Methods. Three hundred sixty six participants (127 male, 239 female; mean age, 54.5; SD ± 18.0) took part in the study. Each participant completed a preconsultation questionnaire including established measures of “state” anxiety, “trait” anxiety, study specific outcome expectancies, and biographical data. Multiple linear regression analysis was used to identify which variables predict state anxiety. Results. Multiple linear regression analysis showed that the heightened trait anxiety, expecting “bad news” and being a non-spectacle wearer are independent predictors of increased state anxiety. R2 was 0.33, i.e., the regression model explained 33% of the variance. Conclusions. This is the first time that the predictors of state anxiety in optometric practice have been identified. Optometrists should recognize that patients who are “anxious types,” who may be expecting “bad news” and who do not wear spectacles may be more anxious.

Purpose. Low patient satisfaction is problematic within optometric practice. However, to date, it is not known how patient anxiety affects this patient variable. Therefore, the purpose of this study was to determine whether patients who report higher levels of preexamination anxiety have lower levels of satisfaction postconsultation. Methods. Optometric patient anxiety and patient satisfaction were measured using self-report questionnaires. A total of 197 participants (82 males, 115 females; mean age 57.1 ± 18.6) completed the Optometric Patient Anxiety Scale before their eye examination. The Rapport subscale (extracted from the Medical Interview Satisfaction Scale) was completed after the eye examination. Results. Validity of the Optometric Patient Anxiety Scale and Rapport subscale for this population was confirmed with Rasch analysis and item estimates calculated. Linear regression identified a significant relationship between optometric anxiety and satisfaction (p < 0.01). Conclusions. This is the first time that a relationship between preconsultation patient anxiety and postconsultation satisfaction has been documented within optometric practice. This indicates that if patient optometric anxiety can be reduced, there may be an improvement in patient satisfaction.

Purpose To demonstrate acquisition and analysis methods for depth-resolved observation of slow retinal physiology induced changes in infrared backscatter in vivo. Methods A dark-adapted human was briefly subjected to a localized photobleach. For 20 min before and 30 min after the stimulus, volumetric optical coherence tomograms were collected partially overlapping the bleached region. Tomograms were segmented into retinal layers by a newly described algorithm exploiting information in adjacent B-scans. En face fundus images extracted from major intraretinal layers were laterally registered manually. Time series summarizing the observed backscatter in selected layers for the bleached and unbleached areas are shown with a variety of corrections and normalizations applied: tomograms were corrected for inherent sensitivity roll-off, and the ratio between other layers and an assumed unchanging layer (retinal pigment epithelium), as well as the ratio of the stimulated area to the unstimulated area, were calculated. Results Adjacent B-scan information allows a simpler segmentation algorithm to be used. Sensitivity roll-off correction reduces signal variability due to eye motion. After normalizations, the signal correlated with the stimulus appears strongest at the photoreceptor inner-outer segment junction. Conclusions Demonstrated methods manage data complexity and reduce uncorrelated signal variability. This single trial warrants further investigation of intrinsic optical signals to observe slow physiologic responses.

PURPOSE. To evaluate the diagnostic potential of the electroretinogram (ERG) photostress test and the focal cone ERG in age-related maculopathy (ARM).\ud \ud METHODS. The cohort comprised 31 patients with ARM and 27 age-matched control subjects. The ERG photostress test was used to monitor cone adaptation after intense light adaptation. Focal 41- and 5-Hz cone ERGs were recorded monocularly (central 20°) to assess steady state retinal function. Univariate analysis identified electrophysiological parameters that differed between groups, and receiver operating characteristic (ROC) curves were constructed to assess their diagnostic potential. Logistic regression analysis determined the diagnostic potential of a model incorporating several independent predictors of ARM.\ud \ud RESULTS. The rate of recovery of the ERG photostress test was reduced (recovery was slower) in subjects with ARM. The parameter exhibited good diagnostic potential (P = 0.002, area under ROC curve = 0.74). The implicit times of the 5-Hz (a-wave, P = 0.002; b-wave, P < 0.001) and the 41-Hz (P < 0.001) focal cone ERGs were increased, and the 41-Hz focal cone ERG amplitude (P = 0.003) and focal to full-field amplitude ratio (P = 0.001) were reduced in the ARM group. Logistic regression analysis identified three independent predictors of ARM, including the rate of recovery of the ERG photostress test.\ud \ud CONCLUSIONS. Early ARM has a marked effect on the kinetics of cone adaptation. The clinical application of the ERG photostress test increases the sensitivity and specificity of a model for the diagnosis of ARM. Improved assessment of the functional integrity of the central retina will facilitate early diagnosis and evaluation of therapeutic interventions.

Purpose. To explore the associations between anisometropia and spherical ametropia, astigmatism, age, and sex. Method. Associations between the prevalence and magnitude of anisometropia with age, sex, spherical power, and cylindrical power, were assessed in a group of 90,884 subjects attending optometry practices in the United Kingdom. Logistic regression models were used to assess the independent contribution of each explanatory variable. Results. Logistic regression analyses that included all subjects or just those aged 20 to 40 years showed that spherical ametropia and astigmatism were independently associated with anisometropia (myopes, P < 1.0E–61; hyperopes, P < 1.0E–11). Anisometropia was relatively stable between the ages of 20 and 40 years, but then became more common with age, in myopes from the age of 40 years onward (P < 0.003) and in hyperopes from the age of 70 years onward (P < 1.0E–6). Sex was not associated with anisometropia to a clinically significant extent. Conclusions. This is the first study to show an independent association between anisometropia and both spherical ametropia and astigmatism. The results also suggest that the previously noted increased prevalence of anisometropia with age occurs later in hyperopes than in myopes, once other covariates have been controlled for. However, it could not be ruled out that this latter effect was due to clinical selection bias in our sample. The findings suggest that research projects involving the recruitment of highly ametropic subjects, such as those investigating the genetics of refractive error, may benefit by avoiding the use of stringent inclusion criteria for anisometropia, because otherwise a large proportion of the relevant population will be excluded.

Failure of the service in Wales was perhaps best reflected in the inadequate number of low vision assessments People in Wales with impaired vision have recently benefited from the arrival of a new nationwide community based low vision service. Undoubtedly, this is a dramatic and welcome development for all those with untreatable sight loss, not just those registered blind or partially sighted. But what has motivated the Welsh Assembly to take this radical step? One reason is that visual impairment in Wales, like the rest of the United Kingdom, is reaching epidemic proportions. Since 1982, the number of people in the United Kingdom registered blind and partially sighted1 has almost doubled and now stands at 359 000.2–4 However, the registers are known to underestimate the number with untreatable sight loss by a factor of twofold to threefold and so there may be more than 1 000 000 people in the United Kingdom with untreatable low vision.5,6 This estimate is supported by a recent Medical Research Council trial that has established that one in five people over the age of 75 have a binocular visual acuity below 6/12.7 In many parts of Wales, the combined prevalence of registerable visual impairment (that is, both blind and partial sight registrations) now exceeds 2%.8 The magnitude of the problem will undoubtedly increase because most sight threatening eye disease is age related and the number of people aged 60 and over is projected to increase by 57% over the next 30 years.9 Another reason for the Welsh Assembly’s decision is that the …

AIMS To substantiate the claim that low vision aids reduce the degree of disability associated with visual impairment. METHODS An observational study of vision, ocular pathology, age, sex, and reading ability in new referrals to a low vision clinic. Reading ability was assessed both with the patients' own spectacles and with an appropriate low vision aid. RESULTS The reading performance and biographical characteristics of new referrals to a low vision clinic were recorded. Data were collected for 168 people over a 6 month period. Upon arrival at the clinic the mean functional visual acuity equated to 6/36 and 77% of patients were unable to read newsprint (N8). After a low vision assessment and provision of a suitable low vision aid 88% of new patients were able to read N8 or smaller text. CONCLUSIONS The degree of visual impairment observed in new referrals to a low vision clinic is sufficient to prevent the majority from performing many daily tasks. Low vision aids are an effective means of providing visual rehabilitation, helping almost nine out of 10 patients with impaired vision to read.