Introduction
Age-Related Macular Degeneration (AMD) is a prevalent eye condition that affects the macula (degenerative disorder), the central part of the retina responsible for sharp, central vision. It is the leading cause of vision loss among older adults in developed countries. As life expectancy increases globally, the incidence of AMD is expected to rise, making it a significant public health concern. AMD is also called age-related maculopathy or senile macular degeneration with specific clinical findings including drusen (yellowish bodies) and retinal pigment endothelial atrophy or changes as early stage and impaired vision as late changes.Types of Age-Related Macular Degeneration
There are two main types of AMD:- Dry AMD (Non-Neovascular or Atrophic AMD): Dry or Geographic AMD accounts for approximately 80-90% of all AMD cases. It is characterized by the accumulation of drusen (yellowish deposits) in the macula, leading to the gradual breakdown of light-sensitive cells and thinning of the macular tissue. This results in a slow and progressive loss of central vision.
- Wet AMD (Neovascular or Exudative AMD): Wet AMD constitutes approximately 10-15% of AMD cases but is responsible for the majority of severe vision loss cases. It is described by the growth of bizarre blood vessels beneath the retina. These vessels can leak blood and fluid, leading to rapid damage and scarring of the macula.
Risk Factors for Age-Related Macular Degeneration
- Age: AMD is primarily an age-related condition, and the risk increases significantly after age 60.
- Genetics: A family history of AMD can predispose individuals to the disease. Specific genes, such as the complement factor H (CFH) and ARMS2/HTRA1 genes, have been associated with an increased risk of AMD.
- Smoking: Cigarette smoking is a modifiable risk factor strongly linked to the development and progression of AMD.
- Race and ethnicity: AMD is more common among Caucasians, particularly those of Northern European descent.
- Cardiovascular disease: Hypertension, high cholesterol, and heart disease have been associated with an increased risk of AMD.
- Obesity: Excess body weight and a high body mass index (BMI) are linked to a higher risk of AMD.
- Sunlight exposure: Long-term exposure to ultraviolet (UV) light may contribute to the development of AMD.
- Gender: AMD is slightly more common in women than in men.
Symptoms of Age-Related Macular Degeneration
The early stages of AMD may not present noticeable symptoms, which is why regular eye examinations are crucial, especially for individuals over 50. As the condition progresses, the following symptoms may be observed:- Blurred or distorted vision: Straight lines may appear wavy or crooked, and central vision becomes increasingly blurry.
- Dark or empty spots: A blind spot may develop in the centre of the visual field, making it difficult to read, drive, or recognize faces.
- Decreased colour perception: Colors may seem less vivid or faded.
- Difficulty adjusting to changes in lighting: Adapting to different light levels becomes challenging.
Diagnosis of AMD
- Comprehensive Eye Examination: An ophthalmologist or optometrist will conduct a thorough eye examination, including visual acuity tests, dilated eye exams, and evaluation of the retina.
- Amsler Grid Test: This test helps identify any central vision distortion. The patient is asked to focus on a grid of horizontal and vertical lines and report any missing or distorted areas.
- Optical Coherence Tomography (OCT): This non-invasive imaging test provides detailed cross-sectional images of the retina, allowing for the identification of retinal thickness and any fluid or blood leakage.
- Fluorescein Angiography: In cases of suspected wet AMD, a fluorescein dye is injected into the arm, which travels to the retina. Photographs are taken as the dye passes through the blood vessels, highlighting any leakage or abnormal vessels.
Treatment options for AMD
Dry AMD:- Antioxidant Vitamins and Minerals: Studies like the Age-Related Eye Disease Study (AREDS) and AREDS2 have shown that high-dose antioxidant supplements (vitamin C, vitamin E, beta-carotene, zinc, and copper) can slow the progression of intermediate to advanced dry AMD in some cases.
- Lifestyle Changes: Quitting smoking, maintaining a healthy diet, managing cardiovascular risk factors, and protecting the eyes from UV light are essential to managing dry AMD.
- Low Vision Aids: Devices such as magnifiers, telescopic lenses, and reading guides can help individuals with visual impairment due to AMD make the most of their remaining vision.
- Anti-VEGF Therapy: Currently, the most effective treatment for wet AMD involves intravitreal injections of anti-vascular endothelial growth factor (VEGF) drugs. These medications block the growth of abnormal blood vessels and reduce leakage, stabilizing or improving vision in many patients.
- Photodynamic Therapy (PDT): PDT is a laser-based treatment that uses a light-activated drug to target and destroy abnormal blood vessels in the retina.
- Combination Therapy: Some cases may benefit from a combination of anti-VEGF therapy and PDT.
- Laser Therapy: Although less commonly used today due to the success of anti-VEGF drugs, laser therapy may be considered for specific cases of wet AMD.
- Stem Cell Therapy: Ongoing research explores the potential of stem cell therapy to regenerate damaged retinal cells and improve vision in individuals with AMD.
- Gene Therapy: Scientists are investigating gene therapy techniques to target and correct genetic mutations associated with AMD.
- Artificial Vision Devices: Advancements in technology have led to the development of visual prosthetics that may restore some vision in individuals with severe vision loss due to AMD.