Validating the accuracy of an activity monitor in a visually impaired older population.

PURPOSE: Activity monitors have been used to objectively measure physical activity and its association with visual impairment in older adults. However, there is limited understanding of the accuracy of activity monitors in people with low vision. This study investigated the accuracy of an activity monitor compared with manual step counting in a low vision population and sought to find the most accurate placement location for the device. METHODS: We recruited 32 individuals aged 50 years and older with low vision. ActiGraph activity monitors were secured bilaterally on the wrists, ankles, and hips of each participant, who then walked a flat, linear course in their home at a comfortable pace for 4 min, using any necessary assistive device such as a long cane, support cane, or guide dog. Steps were counted using a hand-held tally counter. ActiGraph-measured step data from the 4-min period were downloaded using the standard and low frequency filters at 1 epoch s-1 through ActiLife. RESULTS: Of the 32 participants, 20 (63%) were female, median visual acuity was 1.48 logMAR (6/180 Snellen), average age was 73 (standard deviation, S.D., 9) years, average body mass index was 28.9 (S.D. 7.0) kg m-2 , and 47% of participants used an assistive device. Average distance for the test course was 10.9 (S.D. 3.4) m and participants completed an average of 368 (S.D. 68) steps during the 4 min. The number of steps recorded by the two, bilaterally-worn devices at each location were averaged. Ankle, hip, and wrist activity monitors detected 85% (interquartile range, IQR 76-94%), 56% (IQR 39-85%), and 56% (IQR 43-69%), respectively, of directly-observed steps when using the standard ActiGraph filter. Detected steps more closely matched directly observed steps for all placement sites when the low-frequency ActiGraph filter was applied: 101% (IQR 99-104%) at the ankle, 94% (IQR 85-101%) at the hip, and 83% (IQR 72-94%) at the wrist. Bland-Altman plots showed greater levels of agreement between ActiGraph-recorded and directly-observed steps at faster walking speeds. CONCLUSIONS: Our results demonstrate that the most accurate location of activity monitor placement is the ankle and that when using the low-frequency filter the level of agreement becomes more acceptable on the wrist and hip, in this population. Use of the low activity filter can help minimise inaccurate calculation of steps in people with low vision, particularly those who walk slowly.

Survey effect on use of eye care by older persons with correctable visual impairment.

PURPOSE: To assess changes in the pattern of eye care utilization among older Australians with correctable visual impairment, identified in an eye survey. METHODS: The Blue Mountains Eye Study (BMES) examined 3654 Australians aged >or= 49 years at baseline (BMES-I). Five-year follow-up examinations were attended by 2334 participants, 75.0% of survivors (BMES-II). Interviewers collected data on eye care utilization at each visit. Habitual (presenting) and best-corrected visual acuity were assessed using a LogMAR chart. Survey reports, including visual acuity and recommendations were sent to participants after each visit. Those with under-corrected refractive error were informed that they could benefit from a new distance prescription. Eye care utilization was compared before and after the BMES-I survey. RESULTS: Of 2152 participants with data from both examinations, 26 had non-correctable and 115 had correctable visual impairment at BMES-I. The proportion of the 115 participants with correctable visual impairment who reported seeing an eye care provider during the previous 2 years increased from 55% at BMES-I to 64% at BMES-II. Comparing the data collected at BMES-II with that at BMES-I, a higher proportion of reported optometric visits in the previous 5 years was evident for all participants regardless of their correctable visual impairment status. Among those with correctable visual impairment at BMES-I, 58% improved to no visual impairment at BMES-II, and the proportion who subsequently wore distance correction increased from 57% to 71%. CONCLUSIONS: We observed modest increases in eye care utilization by older persons after an eye survey, particularly those with correctable visual impairment.

Refractive status and the 5-year incidence of age-related maculopathy: the Blue Mountains Eye Study.

This study aimed to assess the longitudinal association between refraction and 5-year incident age-related maculopathy (ARM) in the Blue Mountains Eye Study population. The dataset included 3654 participants aged 49+ (82.4% of eligible) examined at baseline (1992-1994), and 2335 (75.1% of survivors) examined after 5 years. Retinal photograph grading followed the International ARM Classification. Incident ARM was assessed using a side-by-side comparison. Refraction was performed using autorefraction with subjective refinement. Spherical equivalent was calculated from spherical plus half the cylindrical power. After adjusting for age, sex and smoking, no association was found between baseline spherical equivalent and 5-year incident late or early ARM. Hyperopic right eyes had slightly higher incident rates for late (0.8%) and early (6.3%) ARM, compared with myopic (0.4% and 4.1%, respectively) or emmetropic (0.5% and 5.0%, respectively) right eyes. After multivariable adjustment, this study found no significant association between hyperopia and the 5-year incidence of late or early ARM. Left eyes or the combined data from both eyes had similar findings.

Increase in cataract surgery prevalence from 1992-1994 to 1997-2000: analysis of two population cross-sections.

BACKGROUND: Monitoring temporal changes in the demand for and provision of cataract surgery will be useful to health planners to meet resource needs and to estimate likely costs. The aim of this report was to compare the prevalence of cataract surgery in two population cross-sections of the Blue Mountains Eye Study (BMES), over an interval of around 6 years. METHODS: Cross-section I (n = 3654; mean age 66.2 years) consisted of BMES I participants (1992-1994). Cross-section II (n = 3509; mean age 66.7 years) consisted of BMES II (5-year) participants (n = 2335) plus persons who had moved into the area and age category since BMES I (n = 1174), so were newly eligible (1997-2000). Cataract surgery history was collected during interview and confirmed at examination. RESULTS: Over this 6-year period, there was a 32% increase in cataract surgery prevalence from 6.0% to 7.9%, or from 6.0% to 7.7% after age standardization. The increase in eye-specific prevalence was 43% (from 4.4% to 6.3%). It was more marked among persons aged 80+ years and for bilateral (from 12.3% to 19.9%) than unilateral surgery (from 10.7% to 11.8%). Best-corrected visual acuity (mean letters read correctly) after surgery (43 and 44 letters, respectively) was similar between cross-sections I and II. CONCLUSIONS: The findings from a representative older population confirm that prevalent cataract surgery has increased substantially over the average 6-year period, from 1992-1994 to 1997-2000.