Elsevier

Ophthalmology

Volume 110, Issue 1, January 2003, Pages 41-50
Ophthalmology

Regular article
Five-year change in visual acuity and incidence of visual impairment: the Blue Mountains Eye Study

https://doi.org/10.1016/S0161-6420(02)01295-2Get rights and content

Abstract

Purpose

To describe the 5-year change in visual acuity and the incidence of visual impairment in a population-based cohort.

Design

Population-based epidemiologic study.

Participants

Of the 3654 participants of the Blue Mountains Eye Study (BMES I) baseline examination (aged 49 years+ during 1992–1994), 2335 were reexamined during the 5-year follow-up examinations from 1997 to 1999 (BMES II), and 543 persons had died since BMES I.

Methods

Visual acuity was measured using a logarithm of the minimum angle of resolution chart in both eyes separately before and after standardized refraction. Pupils were dilated and a detailed examination was performed.

Main outcome measures

Visual impairment, after best refractive correction, was defined as any (visual acuity ≤20/40; ≤41 letters) and severe (visual acuity ≤20/200; 0–5 letters) in keeping with the Beaver Dam Eye Study. Incident binocular visual impairment was defined as visual acuity ≤20/40 in both eyes at follow-up, where visual acuity was >20/40 in both eyes at baseline. Incident binocular severe visual impairment was defined as visual acuity ≤20/200 in both eyes at follow-up, where visual acuity was >20/200 in both eyes at baseline. The incidence for three other levels of visual impairment is also given: <20/40, <20/70, and <20/200. Monocular visual impairment was defined as impairment in one eye only at follow-up, where both eyes were unimpaired at baseline. Incident doubling and halving of the visual angle were calculated.

Results

Incidence rates for visual impairment increased significantly with age. Any incident impairment ≤20/40 occurred binocularly in 41 persons (1.9%) and monocularly in 150 persons (7.1%). Severe incident impairment ≤20/200 occurred binocularly in 3 persons (0.1%) and monocularly in 44 persons (2.1%). Incident impairment <20/40 occurred binocularly in 37 persons (1.7%) and monocularly in 134 persons (6.3%). Impairment <20/70 occurred binocularly in 15 persons (0.7%) and monocularly in 84 persons (3.8%). Impairment <20/200 occurred binocularly in 3 persons (0.1%) and monocularly in 44 persons (1.9%). Women consistently had a higher incidence of visual impairment than men, although this was often not statistically significant after adjusting for age. Increasing age was a strong predictor of visual impairment.

Conclusions

This study has documented the 5-year incidence and causes of visual impairment in an older Australian population.

Section snippets

Population

The BMES is a population-based survey of vision and common eye diseases in an urban population aged 49 years or older residing in two postal codes of the Blue Mountains region, west of Sydney, Australia. A previous report from the study explained the reasons for selecting, and the methods used to identify, the target population and described the population.21 To summarize, study personnel conducted a door-to-door census from November to December 1991 for the first postcode area and from March

Results

The mean age of participants at baseline was 64.5 years. The mean follow-up period for the 2335 BMES II participants was 5.1 years (minimum, 3.0 years; maximum, 7.8 years). Women accounted for 57.5% of subjects. Table 1 shows the baseline characteristics of participants.

Discussion

Incident figures from this report can be used to project the number of incident cases of visual impairment within the Australian population. By using population estimates for the year 2001 from the Australian Bureau of Statistics26 with our incident visual impairment figures, we estimate that in 5 years approximately 94,700 persons will develop visual impairment <20/40 in both eyes; these persons will no longer be able to obtain a driver’s license based on the current visual acuity criterion.

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    Manuscript no. 210694.

    Supported by the Australian National Health & Medical Research Council, Canberra, Australia.

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