Fourteen‐year incidence of age‐related maculopathy and cause‐specific prevalence of visual impairment and blindness in a Caucasian population: the Copenhagen City Eye Study
Authors: Buch Helena 
Published: April 2005

The purpose of this PhD thesis was to analyse: (1) the prevalence and causes of visual impairment and blindness among adult Danes (papers I–III); (2) the 14‐year incidence of age‐related maculopathy (ARM) (paper IV); (3) the 14‐year incidence of visual loss with special attention to ARM (paper IV); (4) the risk factors for development of ARM (papers IV and V); and (5) the association between ARM and survival (paper VI). The studies were based on data from the Copenhagen City Heart Study (CCHS), the baseline eye study conducted by Troels Vinding MD, and the follow‐up eye study conducted by Helena Buch MD. The CCHS is a population‐based cohort study that included initially a random population sample of almost 20 000 people. This cohort includes the basis population of the Copenhagen City Eye Study, which includes two subsamples: (1) 1000 individuals between the ages of 60–80 years from the second CCHS population who were studied twice with a mean time interval of 14.5 years (range, 12.6–16.1 years) to determine the prevalence (papers I and II) and incidence rates (papers IV–VI) among elderly Danes, based on standardized clinical and grading procedures; and (2) 9980 individuals aged 20–84 years from the third CCHS population who were studied to determine cause‐specific prevalence rates of visual loss with a wide age range based on a validated questionnaire‐response method (paper III).

(1) The prevalence of visual loss rose significantly with age. Using the national criteria, the age‐standardized prevalence rates of visual impairment and blindness for people aged 20–64 years were 0.21% and 0.10%, respectively. However, for people aged 65–80 years the age‐standardized prevalence rates of visual impairment and blindness were 3.89% and 1.14%, respectively. The distributions of the causes of visual loss varied by age. The most important contributors to poor vision occurring before the age of 65 years were optic neuropathy, diabetic retinopathy, retinitis pigmentosa, excessive myopia and other retinal diseases. After the age of 64 years, late ARM and cataract were the primary causes of the age‐related increase in the prevalence of visual loss. Late ARM was the major cause of prevalent blindness. The potential impact of therapeutic intervention is great; when the causes of visual impairment and blindness were grouped for Danish people aged 20–84 years, 29% had the potential for improved vision via surgical intervention, and 15% had potentially preventable eye diseases.

(2) The cumulative 14‐year incidence of early and late ARM in either eye was 37.8% and 16.9%, respectively. 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).

(3) 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 incident blindness.

(4) Our findings indicate that severe drusen type, large drusen and pigmentary abnormalities were predictors for progression to late ARM and associated visual loss. Additionally, a direct correlation was found between age, cataract, family history, alcohol consumption and the apolipoproteins A1 and B and the 14‐year incidence of ARM.

(5) Finally, the association between ARM and survival was analysed, because 60.9% of the participants of the baseline study had died. When adjusting for survival‐related factors, ARM was statistically significant, associated with 59% increased mortality in women but not in men.

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