Function of the Normal Macula

How much do you know about your macula? This tiny part of the eye plays a huge role in things we do every day. We rely on our macula to recognize faces up close, read, drive, and engage in hobbies like sewing, painting and model-building. That’s because the macula gives us the ability to clearly see what is in our direct line of sight, including fine details.

Preeti Subramanian, PhD, Director of Vision Programs at BrightFocus Foundation, provides a closer look at how a healthy macula functions, and what happens when it stops working normally as seen in age-related macular degeneration (AMD).

What are the major parts of the macula, and what are the jobs of each of these structures?

The macula is a pinhead-sized area in the center of the retina at the back of the eye. An even tinier dimple in the center of the macula is called the fovea.

The macula is a bit like a cake with several layers—despite the fact it’s so thin. Near the top is a layer of light-sensitive cells called photoreceptors, which turn light into electrical signals. The two major types of photoreceptors are called rods and cones. Rods and cones send their electrical messages along the optic nerve to the brain, which creates the images we see.

The rods can detect very low levels of light. According to Dr. Subramanian, the rods do two main jobs: letting us see in dim light, and at our sides and up and down without moving our head. (This side vision is known as peripheral vision.)

We have fewer cones than rods. “Cones allow us to see color and sharp detail,” Dr. Subramanian explained. The fovea—that dip in the middle of the macula—is the area with the highest concentration of cones. This is why the fovea is essential for seeing crisp detail and accurate color.

Getting back to the layer cake. Now, think of a building with several floors. Under the rods and cones is a sheet of cells called the retinal pigmented epithelium. It’s part garbage disposal, part recycling plant, and part food delivery system. “The retinal epithelium protects and nourishes the retina,” Dr. Subramanian said. It also reuses parts of worn-out rods and cones and gets rid of waste.

Directly underneath the retinal epithelium is Bruch’s membrane. It supports the retina and keeps blood vessels from growing into the upper layers—like the fabric gardeners use to keep weeds from popping up. The next floor down is the choroid layer, which contains the plumbing—blood vessels that carry nutrients to the retina.

Watch a Video: The Macula

What goes wrong when someone starts to develop age-related macular degeneration?

“Typically, AMD starts with changes in the retinal pigmented epithelium cells,” Dr. Subramanian said. This layer of cells begins to malfunction and can no longer clear away waste properly. As a result, clumps of waste products and fats called drusen form underneath the RPE, and above Bruch’s membrane. Drusen are a key feature of the dry form of AMD. Over time, the changes that occur in dry AMD can damage and kill cells in the retinal epithelium. This, in turn, can affect the photoreceptors and other structures in the eye, eventually leading to vision loss.

“In the early stages of dry AMD, the drusen don’t cause any noticeable symptoms,” Dr. Subramanian said. However, “an optometrist or ophthalmologist can detect drusen by examining the back of your eye with specialized tests,” she added. As the drusen grow larger, the central part of your vision may become blurry.

In wet AMD, fragile blood vessels start growing under the macula. “These abnormal blood vessels can leak fluid,” noted Dr. Subramanian. The fluid buildup can make straight lines look wavy and lead to rapid loss of central vision.

What can I do to keep my macula as healthy as possible?

• First of all, if you smoke, stop. Smoking is a major risk factor for AMD, and quitting can significantly reduce your chances of developing the disease,” Dr. Subramanian said.
• Many things that are good for your heart are also good for your macula. This includes keeping chronic conditions like high blood pressure, diabetes, and high cholesterol as well-controlled as possible.
• Regular exercise is another heart-healthy activity that protects the macula. It helps maintain a healthy weight and dampens inflammation—both factors that benefit eye health.
• Long-term exposure to the ultraviolet (UV) rays in sunlight appears to increase AMD risk. “Wear a wide-brimmed hat and 100-percent UV-blocking sunglasses when you go outdoors to help protect your eyes,” Dr. Subramanian advised.
• Eat a wide range of antioxidant-rich foods. For instance, lutein and zeaxanthin are known to play an important role in macular health,” Dr. Subramanian explained. These nutrients are found in dark leafy greens (such as spinach and kale), and yellow and orange fruits and vegetables. Eating fish high in omega-3 fatty acids—such as salmon and tuna—has also been linked to lower AMD risk. Find tasty healthy vision recipes here.
• Finally, “be sure to get a complete eye exam every 1–2 years to check for early changes in the macula,” Dr. Subramanian emphasized.

Summary

While we can’t change our age, small daily choices can help safeguard our macular health for a lifetime. Quit smoking. Enjoy a healthy diet, including foods packed with antioxidants like lutein and zeaxanthin. Commit to regular exercise. Shield your eyes from UV when you go outdoors. And make routine eye exams a priority. Regular checkups are crucial for detecting potential issues early and preserving your vision.