Age-related eye disease and cognitive function

Objectif: Évaluer la relation entre la fonction cognitive chez les personnes âgées atteintes de dégénérescence maculaire reliée à l’âge (DMLA), de glaucome ou de dystrophie cornéenne de Fuchs et les comparer avec les personnes âgées n’ayant pas de maladie oculaire. Devis: Étude transversale de population hospitalière. Participants: 420 participants (113 avec la DMLA, 66 avec la dystrophie cornéenne de Fuchs, 130 avec le glaucome et 111 témoins). Méthodes: Nous avons recruté les patients à partir de la clinique d’ophtalmologie de l’Hôpital Maisonneuve-Rosemont (Montréal, Canada) de septembre 2009 à septembre 2013. Les patients atteints de la DMLA ou de la maladie de Fuchs ont une acuité visuelle inférieure à 20/40 dans les deux yeux, tandis que les patients avec du glaucome ont un champ visuel dans le pire œil inférieur ou égal à -4dB. Les patients contrôles, qui ont été recrutés à partir des mêmes cliniques, ont une acuité visuelle et un champ visuel normaux. Nous avons colligé des données concernant la fonction cognitive à partir du test Mini-Mental State Exam (MMSE)-version aveugle. Pour mesurer la fonction visuelle, nous avons mesuré l’acuité visuelle, la sensibilité au contraste et le champ visuel. Nous avons également révisé le dossier médical. Pour les analyses statistiques, nous avons utilisé la régression linéaire. Critère de jugement principal: MMSE-version aveugle. Résultats: Les trois maladies oculaires ont été associées à une limitation de la cognition. Le score de MMSE-version aveugle se situe de 0.7 à 0.8 unités plus basses par rapport au groupe contrôle. Comparativement aux contrôles, les patients avec maladies oculaires ont eu un score moyen diminué (P < 0.05). Le niveau d’éducation élevé est associé à une meilleure cognition (P < 0.001). Conclusions: Nos résultats suggèrent que les maladies oculaires sont associées à une diminution de la fonction cognitive chez les personnes âgées. De futures études sont nécessaires pour évaluer l’impact des maladies oculaires sur le déclin cognitif chez cette population pour pouvoir envisager des interventions ciblées qui pourraient les aider à maintenir leur indépendance le plus longtemps possible.

Sensibilidad al contraste y percepción de color en pacientes con lentes intraoculares amarillos : estudio de corte transversal

El presente estudio descriptivo de corte transversal, comparó la percepción de color (Test de Farnsworth-100 y de Ishihara) y la sensibilidad al contraste en un grupo de 35 ojos con implantes de lentes intraoculares claros esféricos y otro grupo de 35 ojos con LIOs amarillos esféricos, para evaluar las diferencias entre tener o no el filtro de luz azul. Adicionalmente, después de un examen oftalmológico completo en el ojo a estudiar, se realizaron preguntas de satisfacción POP para evaluar el resultado subjetivo del procedimiento. Todos los pacientes tenían más de 3 meses POP. No se encontraron diferencias estadísticamente significativas en las pruebas de percepción de color que sugirieran que las alteraciones correspondían al filtro de luz azul, y aunque los pacientes con los LIOs amarillos lograron un mejor desempeño en la prueba de sensibilidad al contraste al analizarlos estadísticamente, clínicamente esto no parece tener importancia. La satisfacción general en ambos grupos tuvo una gran puntuación, y dentro de las molestias referidas más frecuentemente y que estaban presentes desde el procedimiento, se encontraban ardor ocular, lagrimeo y dificultad para ver de cerca sin corrección. Según estudios en modelos animales, hay evidencia que sugiere que los LIOs amarillos, al compararlos con LIOs claros, protegen de mejor manera la retina una vez el cristalino se ha retirado. Según este y otros estudios publicados a la fecha, la agudeza visual, sensibilidad al contraste y percepción de color no varían de manera importante entre ambos tipos de lentes en la población general.

Visual processing of concentric sine-wave gratings in adolescents and adults

The aim of this study was to compare the contrast visual processing of concentric sinusoidal gratings stimuli between adolescents and adults. The study included 20 volunteers divided into two groups: 10 adolescents aged 13-19 years (M=16.5, SD=1.65) and 10 adults aged 20-26 years (M=21.8, SD=2.04). In order to measure the contrast sensitivity at spatial frequencies of 0.6, 2.5, 5 and 20 degrees of visual angle (cpd), it was used the psychophysical method of two alternative forced choice (2AFC). A One Way ANOVA performance showed a significant difference in the comparison between groups: F [(4, 237)=3.74, p<.05]. The post-hoc Tukey HSD showed a significant difference between the frequencies of 0.6 (p <.05) and 20 cpd (p<.05). Thus, the results showed that the visual perception behaves differently with regard to the sensory mechanisms that render the contrast towards adolescents and adults. These results are useful to better characterize and comprehend human vision development.

Glaucoma and on-road driving performance

PURPOSE. To investigate the on-road driving performance of patients with glaucoma.

METHODS. The sample comprised 20 patients with glaucoma and 20 subjects with normal vision, all licensed drivers, matched for age and sex. Driving performance was tested over a 10-km route incorporating 55 standardized maneuvers and skills through residential and business districts of Halifax, Nova Scotia, Canada. Testing was conducted by a professional driving instructor and assessed by an occupational therapist certified in driver rehabilitation, masked to participant group membership and level of vision. Main outcome measures were total number of satisfactory maneuvers and skills, overall rating, and incidence of at-fault critical interventions (application of the dual brake and/or steering override by the driving instructor to prevent a potentially unsafe maneuver). Measures of visual function included visual acuity, contrast sensitivity, and visual fields (Humphrey Field Analyzer; Carl Zeiss Meditec, Inc., Dublin, CA; mean deviation [MD] and binocular Esterman points).

RESULTS. There was no significant difference between patients with glaucoma (mean MD = −1.7 dB [SD 2.2] and −6.5 dB [SD 4.9], better and worse eyes, respectively) and control subjects in total satisfactory maneuvers and skills (P = 0.65), or overall rating (P = 0.60). However, 12 (60%) patients with glaucoma had one or more at-fault critical interventions, compared with 4 (20%) control subjects (odds ratio = 6.00, 95% CI, 1.46–24.69; higher still after adjustment for age, sex, medications and driving exposure), the predominant reason being failure to see and yield to a pedestrian. In the glaucoma group, worse-eye MD was associated with the overall rating of driving (r = 0.66, P = 0.002).

CONCLUSIONS. This sample of patients with glaucoma with slight to moderate visual field impairment performed many real-world driving maneuvers safely. However, they were six times as likely as subjects with normal vision to have a driving instructor intervene for reasons suggesting difficulty with detection of peripheral obstacles and hazards and reaction to unexpected events.

Risk of falls and motor vehicle collisions in glaucoma

PURPOSE. To investigate the risk of falls and motor vehicle collisions (MVCs) in patients with glaucoma.

METHODS. The sample comprised 48 patients with glaucoma (mean visual field mean deviation [MD] in the better eye = −3.9 dB; 5.1 dB SD) and 47 age-matched normal control subjects, who were recruited from a university-based hospital eye care clinic and are enrolled in an ongoing prospective study of risk factors for falls, risk factors for MVCs, and on-road driving performance in glaucoma. Main outcome measures at baseline were previous self-reported falls and MVCs, and police-reported MVCs. Demographic and medical data were obtained. In addition, functional independence in daily living, physical activity level and balance were assessed. Clinical vision measures included visual acuity, contrast sensitivity, standard automated perimetry, useful field of view (UFOV), and stereopsis. Analyses of falls and MVCs were adjusted to account for the possible confounding effects of demographic characteristics, medications, and visual field impairment. MVC analyses were also adjusted for kilometers driven per week.

RESULTS. There were no significant differences between patients with glaucoma and control subjects with respect to number of systemic medical conditions, body mass index, functional independence, and physical activity level (P > 0.10). At baseline, 40 (83%) patients with glaucoma and 44 (94%) control subjects were driving. Compared with control subjects, patients with glaucoma were over three times more likely to have fallen in the previous year (odds ratio [OR]adjusted = 3.71; 95% CI, 1.14–12.05), over six times more likely to have been involved in one or more MVCs in the previous 5 years (ORadjusted = 6.62; 95% CI, 1.40–31.23), and more likely to have been at fault (ORadjusted = 12.44; 95% CI, 1.08–143.99). The strongest risk factor for MVCs in patients with glaucoma was impaired UFOV selective attention (ORadjusted = 10.29; 95% CI, 1.10–96.62; for selective attention >350 ms compared with ≤350 ms).

CONCLUSIONS. There is an increased risk of falls and MVCs in patients with glaucoma.

Effects of task lighting on visual function in age-related macular degeneration

The purpose was to investigate the effects of the spectral power distribution (SPD) and illuminance of task lighting on visual function in age-related macular degeneration (ARMD) compared to normal healthy eyes. Twenty-eight subjects with ARMD and 18 age-matched normal subjects were studied. The effects on visual function were determined for four common task light sources: standard pearl coat incandescent (SP), daylight blue incandescent (DL), warm white fluorescent (WW) and cool white fluorescent (CW). Apart from a small, statistically significant improvement in contrast sensitivity with DL compared to SP lighting (0.5 dB, p = 0.01), there were no significant effects of SPD on other visual functions and no differences in the effects for subjects with ARMD and those with normal vision. Thus, for task lighting typically used in low vision rehabilitation, the SPD would seem to be of minimal clinical importance to visual function. However, increasing the task illuminance had a greater effect on visual function, in particular for subjects with ARMD (p < 0.01). For an increase in illuminance from 300 to 3000 lux, the mean increase in contrast sensitivity and near visual acuity was 1.5 dB and 0.13 log MAR, respectively. Although this effect is not large, we suggest that it is clinically relevant and supports the provision of additional task illuminance as an important part of low vision rehabilitation for patients with ARMD.

Relationship between vision impairment and ability to perform activities of daily living

Purpose: To determine the relationship between clinical measures of vision impairment and the ability to perform activities of daily living (ADLs).

Methods: One hundred and twenty subjects with low vision from a variety of causes participated in the study. Vision impairment was assessed under binocular conditions by measuring distance visual acuity, near word acuity, Melbourne Edge Test contrast sensitivity, Pelli–Robson Chart contrast sensitivity and visual fields. The ADL performance was assessed using the Melbourne Low Vision ADL Index (MLVAI), which is in part an observed performance assessment of instrumental ADLs and in part a self-report assessment of basic self-care ADLs.

Results: All vision measures had a high, statistically significant correlation with MLVAI total score. Near word acuity, had the strongest correlation (rs=−0.86, p < 0.001), followed by Melbourne Edge Test contrast sensitivity (rs=0.80, p < 0.001). Visual field had the weakest correlation (rs=0.56, p < 0.001). Together, age, near word acuity, Melbourne Edge Test contrast sensitivity and visual field accounted for 82.2% (adjusted R2, p < 0.001) of the variance in MLVAI total score. All correlations obtained were higher for the observed performance assessment of instrumental ADLs than for the self-report assessment of basic self-care ADLs.

Conclusions: Clinical vision impairment measures are highly correlated with capacity to perform ADLs, as measured by the MLVAI.

A weighted version of the Melbourne low-vision ADL index : a measure of disability impact

Objective. To develop a version of the Melbourne Low-Vision ADL Index that measures the personal impact of disability in activities of daily living (ADL's). Also, to determine the relationship between clinical measures of vision impairment and disability impact.

Methods. The Melbourne Low-Vision ADL Index (MLVAI) is a desk-based clinical assessment of disability in ADL's. Ability to perform each item is rated on a five-level descriptive scale from zero to four. In this study, the original version of the MLVAI was modified to measure disability impact. The simple modification involved weighting each item by the importance of that item to the person being tested. Importance was also rated on a five-level scale from zero to four. The validity and reliability of the Weighted Melbourne Low-Vision ADL Index (MLVAIW) was determined for 97 vision-impaired subjects in a cross-sectional study.

Results. Cronbach's alpha coefficient indicated an internal reliability of 0.94, and an intraclass correlation coefficient indicated an overall reliability of 0.88. The standard error of measurement was 24.7 points (out of a possible score of 400). There was a statistically significant difference in test scores between normal subjects and vision-impaired subjects. All vision measures had a high, statistically significant correlation with MLVAIW score. Near-word acuity had the strongest correlation (rs = 0.78, p < 0.001), followed by Melbourne Edge Test contrast sensitivity (rs = -0.72, p < 0.001). Visual field had the weakest correlation (rs = -0.52, p < 0.001). The best predictive model of MLVAIW score incorporated the variables age, near-word acuity, and visual field. Together, these variables accounted for 65.1% of the variance in MLVAIW score.

Conclusions. The MLVAI is highly valid and reliable when weighted by a scale that reflects the personal importance of ADL's. The MLVAIW can provide information over and above that obtained with the usual clinical vision measures and may be used to assess low-vision patients and to measure low-vision rehabilitation outcomes. It is suggested that the assessment of disability using the original MLVAI and the assessment of the impact of disability using the MLVAIW should be kept separate to facilitate the clear interpretation of the outcomes of low-vision rehabilitation.

Mobility of people with retinitis pigmentosa as a function of vision and psychological variables

We investigated the mobility performance of subjects with retinitis pigmentosa (RP) as a function of clinical measures of residual vision and psychological variables. We found a highly significant correlation between clinical measures of residual vision and mobility. Pelli-Robson contrast sensitivity and residual visual field together explained 64% of the variance in mobility performance in an indoor shopping mall. We suggest a simple new clinical method of scoring the visual field for predicting mobility performance, the RP Concentric Field Rating. The RP Concentric Field Rating alone explained 60% of the variance in mobility performance. In spite of expectations derived from reading the recent literature, we did not find a significant correlation between psychological variables and mobility performance in a group of subjects with RP.

Comparison of functional mobility performance with clinical vision measures in simulated Retinitis Pigmentosa

Simulations of retinitis pigmentosa (RP) under various conditions of retinal illuminance were designed and investigated in order that they might be used in the mobility training of clients with early RP. Goggles incorporating a 2.5 neutral density (ND) filter with a 0.5-mm diameter pinhole were found to be a potentially useful simulation device for this purpose. This investigation also compared mobility performance with clinical vision measures under photopic, mesopic, and scotopic conditions of retinal illuminance. Although none of the clinical vision measures we used was entirely predictive of mobility performance, some measures were better predictors than others. For a severe constriction of the visual field and decreasing retinal illuminance, both edge contrast sensitivity and visual acuity, measured outdoors, accounted for a greater proportion of the variance in mobility performance than did low contrast visual acuity measured under the same circumstances. The same clinical vision measures, taken in-doors, were of no value in predicting outdoor mobility performance.

Synchrotron microComputed tomography of the mature bovine dentinoenamel junction

The mature dentinoenamel junction (DEJ) is viewed by some investigators and the current authors, not as a fossilized, sharp transition between enamel and dentin, but as a relatively broad structural transition zone including the mantle dentin and the inner aprismatic enamel. In this study, the DEJ structure in bovine incisors was studied with synchrotron microComputed Tomography (microCT) using small cubes cut parallel to the tooth surface. The reconstructions revealed a zone of highly variable punctate contrast between bulk dentin and enamel; the mean linear attenuation coefficients and their standard deviations demonstrated that this zone averaged less mineral than dentin or enamel but had more highly variable structure than either. The region with the punctuate contrast is, therefore, the mantle dentin. The thickness of the mantle dentin seen in a typical data set was about 30 mu m, and the mantle dentin-enamel interface deviated +/- 15 mu m from the average plane over a distance of 520 mu m. In the highest resolution data (similar to 1.5 mu m isotropic voxels, volume elements), tubules in the dentin could be discerned in the vicinity of the DEJ. Contrast sensitivity was high enough to detect differences in mineral content between near-surface and near-DEJ volumes of the enamel. Reconstructions before and after two cubes were compressed to failure revealed cracks formed only in the enamel and did not propagate across the mantle dentin, regardless of whether loading was parallel to or perpendicular to the DEJ. (C) 2007 Elsevier B.V. All rights reserved.

Diferenças sensoriais e motoras entre jovens e idosos: contribuição somatossensorial no controle postural

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Quantitative analysis of mineral content in enamel using synchrotron microtomography and microhardness analysis. - art. no. 631824

Synchrotron microtomography is a tool to quantify the mineralization of dental tissues as well as microhardness analysis, since they provide adequate precision and contrast sensitivity. This study evaluates synchrotron microtomography and microhardness analysis for quantifying the mineral content of bovine enamel. Fifty enamel blocks were submitted individually for 5 days to a pH-cycling model at 37 degrees C and remained in the remineralizing solution for 2 days. The blocks were treated twice daily for 1 min with NaF dentifrices (Placebo, 275, 550, 1,100 mu g F/g and Crest (R)) diluted in deionized water. Surface microhardness changes (%SMH) and mineral loss (Delta Z) were then calculated. Synchrotron microtomography was also used to measure total mineral lost (SMM). Pearson's correlation (p < 0.05) was used to determine the relationship between different methods of analysis and dose-response between treatments. Dentifrice fluoride concentration and %SMH and Delta Z were correlated (p < 0.05). There was a positive relationship (p < 0.05) when comparing SMM vs. Delta Z; a negative relationship (p < 0.05) was found for %SMH vs. SMM and %SMH vs. Delta Z. Based on the results of this study, it was possible to conclude that synchrotron microtomography provides the best spatial resolution and contrast sensitivity for quantifying mineral gradients.

Alterações sensoriais e motoras associadas ao envelhecimento e controle postural de idosos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeitos da atividade física no controle postural e capacidade funcional de idosos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)