Macular degeneration is caused by:
**Core Concept**
Macular degeneration is a leading cause of vision loss in older adults, characterized by the deterioration of the macula, a region in the retina responsible for central vision. This condition involves complex interactions between genetic, environmental, and lifestyle factors.
**Why the Correct Answer is Right**
The correct answer is **A. Vascular endothelial growth factor (VEGF)**. VEGF plays a crucial role in the pathogenesis of macular degeneration. In this condition, the growth of new, fragile blood vessels (neovascularization) in the retina leads to leakage and scarring, causing vision loss. VEGF promotes angiogenesis by binding to its receptors on endothelial cells, stimulating their proliferation and migration. The increased expression of VEGF in the retina contributes to the progression of macular degeneration.
**Why Each Wrong Option is Incorrect**
**Option B:** This option is incorrect because while **age-related changes** contribute to the development of macular degeneration, they are not the primary cause. Aging is a risk factor, but it is not the underlying mechanism.
**Option C:** This option is incorrect because **hypertension** is a risk factor for macular degeneration, but it is not the direct cause. High blood pressure can lead to vascular damage and increase the risk of developing macular degeneration, but it is not the primary mechanism.
**Clinical Pearl / High-Yield Fact**
The **"AREDS" formula**, which includes antioxidants such as vitamin C, vitamin E, lutein, and zeaxanthin, has been shown to slow the progression of macular degeneration. This formula is often recommended for patients with intermediate or advanced macular degeneration.
**Correct Answer: A. Vascular endothelial growth factor (VEGF)**