14-year incidence of age-related maculopathy and cause-specific prevalence of visual impairment and blindness in a Caucasian population: the Copenhagen City Eye Study


Helena Buch MD
Department of Ophthalmology,
National University Hospital
Blegdamsvej 9
DK-2100 Copenhagen
Tel: + 45 35 55 35 86
Fax: + 45 35 45 22 90
Email: hbh@dadlnet.dk

Visual impairment and blindness cause important functional and social limitations. Thus, prevention of visual loss is the major goal of the eye care delivery system. Previous studies have reported that visual disability occurs more frequently with increasing age and that age-related maculopathy (ARM) is the prevailing cause among elderly white individuals. Because the elderly population represents the fastest growing segment of the Danish population and because increasing longevity is not associated with a life free of disabilities, the need for eye treatment and low vision rehabilitation will increase. Descriptive and analytic epidemiological information is therefore important to determine the level of ophthalmologic health care and social support needed. Epidemiological studies of Danish patients registered with severe irreversible eye diseases, have contributed to prevalence and incidence data on visual loss and the related causes. Yet, studies based on registries only provide data on the frequency of certification of irreversible severe visual loss and not on the prevalence or incidence of disease. In addition, many aspects of ARM need further clarification, including its longterm incidence, associated risk factors, and relationship to survival. In Denmark, no population-based study has addressed these questions. However, recently a unique opportunity arose to fill this gap in a population-based study of Danes.

The goals of this study were, firstly, to gain knowledge about the prevalence and causes of visual impairment and blindness among adult Danes (Buch et al. 2001a, 2001b, 2004) and, secondly, to elucidate the 14-year incidence of ARM and visual loss, the risk factors for development of ARM, and the association between ARM and survival (Buch et al. 2005a, 2005b, 2005c) in an urban Scandinavian population. Thus, the thesis is divided into two main sections.

The body of the thesis is based on two subsamples of the Copenhagen City Heart Study (CCHS), a population-based cohort study that initially included a random population sample of almost 20, 000 people. The first subsample comprised 1000 individuals aged 60–80 years from the CCHS population who were studied twice over a mean time interval of 14.5 years (range 12.6–16.1 years) to determine the prevalence (Buch et al. 2001a, 2001b) and incidence rates (Buch et al. 2005a) of visual impairment and blindness among elderly Danes, using standardized clinical and grading procedures. The second subsample comprised 9980 individuals aged 20–84 years from the CCHS population who were studied to determine cause-specific prevalence rates of visual loss over a wide age range using a validated questionnaire method (Buch et al. 2004).

Section I, which is based on three previous papers (Buch et al. 2001a, 2001b, 2004), aims to characterize the prevalence and causes of visual impairment and blindness among adult Danes. The prevalence of visual loss rose significantly with age (Buch et al. (2001a, 2001b, 2004). The age-standardized prevalence rates of visual impairment and blindness for persons aged 20–64 years were 0.2% and 0.1%, respectively, when using the national criteria (Buch et al. 2004). However, the age-standardized prevalence rates of visual impairment and blindness for persons aged 65–80 years were 3.9% and 1.1%, respectively, using similar criteria (Buch et al. 2001a, 2001b). The distribution of the causes of visual loss varied by age. The most important contributors to poor vision that developed before the age of 65 years were optic neuropathy, diabetic retinopathy, retinitis pigmentosa, excessive myopia and other retinal diseases (Buch et al. 2004). However, late ARM and cataract were found to be the primary causes of the increase in the age-related prevalence of visual loss after 60 years of age and late ARM was the major cause of blindness (Buch et al. 2001a, 2001b, 2004).

Section II is also based on three papers (Buch et al. 2005a, 2005b, 2005c). This section describes the longterm incidence of ARM and visual loss, the associated risk factors and survival. The cumulative 14-year incidence of early and late ARM in either eye were 37.8% and 16.9%, respectively (Buch et al. 2005a). The cumulative incidence of exudative ARM in either eye was 12.0% and that of pure geographic atrophy was 4.9%, and the rates increased with age (p < 0.01). The cumulative 14-year incidences of visual impairment or legal blindness in the better eye were 16.7% and 5.1%, respectively, and those of visual impairment or legal blindness from late ARM were 6.0% and 3.4%, respectively. Late ARM, the leading cause, resulted in 66.7% of all blindness. The presence of severe drusen, large drusen and pigmentary abnormalities were predictors of progression to late ARM and associated visual loss. A correlation was also found between age, cataract, family history, alcohol consumption, and the apolipoproteins A1 and B and the 14-year incidence of ARM (Buch et al. 2005b). Additionally we analysed the association between ARM and survival, because 60.9% of the participants in the baseline study had died (Buch et al. 2005c). The results of this study strongly suggest that the life expectancy of women with ARM is shorter than that of women without ARM because ARM was significantly (relative risk 1.59, 95% confidence interval 1.23–2.07) associated with a 59% increase in mortality in women but not in men.

These data may mirror the actual occurrence of vision loss and ARM in the Danish population, and it is hoped that they may assist health care planners prepare for the future eye care needs of the general population.

The full Thesis is available from: http://www.blackwell-synergy.com/toc/aos/83/thesis