Drusen are yellow deposits of lipids and proteins that accumulate as cellular waste material under the retina, the light-sensitive tissue at the back of the eye. While the presence of some drusen is a normal part of aging for many adults over 50, they can also indicate an underlying issue. Most people with these deposits experience no symptoms, and their presence is discovered during a routine eye examination.
Types and Locations of Drusen
Drusen are classified into two types: hard and soft. Hard drusen are small, well-defined, and spread out from one another. Their presence is common with age and they are considered low risk, as this type does not cause vision problems.
Soft drusen are larger with less distinct borders and can cluster and merge, forming significant deposits under the retina. The presence of numerous soft drusen is more concerning because they are closely associated with age-related eye conditions and can disrupt the overlying retinal tissue.
Drusen are also categorized by location. They most often form under the macula, the central part of the retina, and are known as macular drusen. A different type, optic nerve head drusen, can form on the optic nerve. These deposits are made of protein and calcium salts, are not related to aging, and can appear in children. Optic nerve drusen are a separate condition and do not carry the same implications as macular drusen.
The Link to Macular Degeneration
The primary concern with drusen is their strong association with age-related macular degeneration (AMD), a leading cause of vision loss in people over 50. While a few small, hard drusen are a normal part of aging, numerous large, soft drusen indicate an increased risk for AMD. The presence of many soft drusen is a hallmark sign of early or intermediate dry AMD.
These deposits accumulate between the retinal pigment epithelium (RPE) and a layer called the Bruch’s membrane. The RPE nourishes the retina’s light-sensing photoreceptor cells. The buildup of soft drusen disrupts this support, leading to damage and degeneration of these cells in the macula, which can cause hazy or distorted central vision.
Large, soft drusen signify dry AMD and elevate the risk of the disease progressing to its more severe form, wet AMD. In wet AMD, abnormal blood vessels grow underneath the retina and can leak fluid and blood, causing rapid central vision loss. Monitoring the size and number of drusen is an important part of assessing a person’s risk for vision-altering disease.
Causes and Risk Factors
The formation of drusen is linked to aging. As the eye gets older, its metabolic processes become less efficient, slowing the clearance of cellular debris from beneath the retina. This allows the lipids and proteins that form drusen to accumulate. While age is the primary driver, other factors increase the risk of developing the soft type associated with AMD.
Genetics plays a significant role, as a family history of AMD suggests a higher predisposition to developing drusen. Lifestyle factors are also implicated, and smoking is a well-established risk factor that accelerates the development and progression of AMD.
Other health conditions contribute to the risk. Cardiovascular disease, high blood pressure, and abnormal cholesterol levels are linked to a higher likelihood of drusen formation. These issues can affect the small blood vessels that nourish the eye, impairing waste clearance. Nutrition is also a factor, as diets low in certain antioxidants may contribute to the process.
Diagnosis and Management
Drusen are detected during a comprehensive dilated eye exam, where an eye doctor can view the retina and identify the yellow deposits. If significant drusen are found, further imaging may be used. Optical Coherence Tomography (OCT) is a non-invasive test that provides high-resolution, cross-sectional images of the retina. This allows a doctor to assess the size and location of drusen and their impact on retinal layers.
There is no direct treatment to remove drusen. Management focuses on reducing the risk of progression to advanced AMD through regular eye exams, which are necessary to track changes in the number or size of the deposits.
For individuals with intermediate dry AMD, specific nutritional supplements may be recommended. The Age-Related Eye Disease Studies (AREDS and AREDS2) identified a formula of vitamins and minerals that can lower the risk of progression to advanced AMD. Lifestyle modifications like quitting smoking, eating a diet rich in leafy greens, and managing cardiovascular health are also important.