Abstract
Purpose::
To compare drusenoid maculopathy in non-human primates with age related macular degeneration in man and test the possible influence of caloric restriction.
Methods::
Funduscopic examination by indirect ophthalmoscopy, slit lamp biomicroscopy and fundus photography including fluorescein angiography have been performed on 121 male and female rhesus macaques of ages 10 to 39. Maculopathies were graded from 0 to 4 (0 = normal; 1 = 1-5 soft drusen; 2 = 6-15 drusen; 3 = more than 15 drusen and/or large confluent drusen; 4 = geographic atrophy or neovascularization). Fifty-three of the monkeys were maintained on a calorically restricted diet (30% lower than controls) and 68 on an approximately ad libitum diet. Other environmental factors were similar. Monkeys were maintained on this protocol for 2-15 years. The effects of age, sex and diet were examined by ANOVA and chi- square analyses. Some monkeys were euthanized because of terminal illness; others were euthanized at 10-30 years of age for experimental purposes. Retinas were examined by light and electron microscopy.
Results::
62% of rhesus monkeys had some form of drusenoid maculopathy. None had neovascularization. There was a significant age-related increase in prevalence and severity of the maculopathy (p =.0124). Females had a significantly higher prevalence and severity than males (p= .019). Calorically restricted females had a lower prevalence (62% versus 70%) and severity (0.64 versus 0.98) than controls but the difference was not significant. Some monkeys develop severe maculopathy in their 20s while others remain unaffected in their 30s. The pathology of the maculopathy resembles that of the human disease.
Conclusions::
Macaque drusenoid maculopathy is common and increases with age as in humans; however, the higher prevalence in female monkeys is not consistently found in humans. Caloric restriction may have a slight effect on its prevalence and severity, which further study of these colonies may clarify. A genetic factor seems apparent because despite similar environmental conditions, some monkeys are affected at early ages while some very old animals are drusen-free.
Keywords: age-related macular degeneration