A 78-year-old white woman presents with loss of central vision that has gradually worsened over the past 6 months. Fully independent before, she can no longer drive and has difficulty with activities of daily living. Her peripheral vision remains normal. Funduscopic examination reveals macular depigmentation and drusen (yellowish-colored subretinal deposits on the macula) (Figure 25-1). She is diagnosed with dry, age-related macular degeneration. After her physician discusses the available information about antioxidants and therapeutic options, she decides to start antioxidants and see an ophthalmologist to discuss laser, surgical, or medical treatments.
Intermediate, dry, age-related macular degeneration with macular depigmentation and drusen (yellowish-colored subretinal deposits on the macula). This patient has central vision distortion. (Reproduced with permission from Paul D. Comeau.)
Age-related macular degeneration (AMD) causes central vision loss in elderly patients. The pathophysiology of AMD is incompletely understood, but involves chronic changes in the retina and retinal pigment epithelium mediated by environmental and genetic factors. AMD is diagnosed by ophthalmoscopic detection of drusen. Healthy lifestyle decreases the risk of development and progression of AMD. Refer patients to an ophthalmologist to evaluate for intravitreal injections, laser photocoagulation or photodynamic therapy, or surgery.
AMD is the leading cause of irreversible vision loss in the industrialized world.
Globally, AMD is estimated to affect 196 million persons by 2020 and 228 million persons by 2040.1
Prevalence is higher in Europeans (12.3%) than in Asians (7.4%) or Africans (7.5%).1
Annual incidence of late AMD in American whites is 3.5 per 1000 persons ≥50 years of age and approximately quadruples per decade in age.2
Smoking increases risk in women (relative risk [RR] 2.5 for current smokers; 2.0 for former smokers).3
AMD aggregates in families, but the specific genetic and familial risk factors are not clear.3
ETIOLOGY AND PATHOPHYSIOLOGY
AMD affects central but not peripheral vision. Environment and genetic attributes increase risk of these pathologic changes with aging.4
Oxidative stress from the buildup of free oxygen radicals causes retinal pigment epithelial (RPE) injury.
RPE injury evokes a chronic inflammatory response. The complement system is involved, and specific polymorphisms of complement genes are associated with advanced disease and progression.4
RPE injury/inflammation forms an abnormal extracellular matrix (ECM), which alters diffusion of nutrients to the retina and RPE.
The abnormal ECM and diffusion leads to retinal atrophy and new vessel growth.
For late AMD, strong risk factors are age, current cigarette smoking, previous cataract surgery (replaced lens provides less eye protection from sunlight), and family history of AMD.
Moderate risk factors include higher body mass index, history of cardiovascular disease, hypertension, ...