Eye Lens (Crystalline Lens)

What is the eye lens?

The lens of the eye is similar to the lens of a camera. It’s the part that focuses and transmits light to the back, where sensors convert it into visual data. The lens is a clear, curved structure that’s embedded deep within your eye (or camera). It absorbs light and bends it to converge at a single point behind it. This focuses the light for the sensors at the back — whether that’s camera film, digital sensors or, in your eye, the retina.

What is the function of the eye lens?

The eye lens absorbs, focuses and directs incoming light to the retina, the light-sensitive tissue in the back of your eye. It changes its shape automatically to focus on objects at different distances. It can make itself flatter or rounder to bend incoming light from different distances toward a single point. This is how it fine-tunes your focus. The lens provides about 30% of your eye’s focus; your cornea provides the other 70%.

Where is the eye lens located?

The lens of the eye sits just behind your pupil, which is the dark spot in the middle of your iris, the colored part of your eye. The pupil is an opening that lets light into your eye. The iris controls the size of the opening and the amount of light coming in. Light passes through your pupil to the eye lens, which focuses it onto the retina behind it. This makes your eye lens the second-to-last layer in your eye.

What are the components of the eye lens?

The eye lens is wrapped in a transparent, elastic capsule. Small, elastic fibers called zonules suspend the lens from the ciliary body above and below it. The ciliary body is a muscular membrane that sits behind your iris. Ciliary muscles help adjust the shape of the lens. When they contract, the zonules actually relax, allowing the lens to become rounder. This is how you focus on something close up.

What is the eye lens made of?

The lens of your eye is made up of structural proteins called crystallins. This is why it’s sometimes called the “crystalline lens.” It has the highest concentration of proteins of almost any tissue in your body. These specialized proteins give the lens its transparency and focusing power. Mature crystallins have no nucleus or organelles — they lose them as they mature. This adds to their clarity and transparency.

But having no nucleus or organelles also prevents the cells from reproducing. This means they don’t “turn over,” as most of your body’s cells do. The cells arrange themselves in concentric layers, like tree rings. Throughout your life, new cells continue to grow at the outer edges of the circle, while the older cells compress toward the center. Eventually, the older cells at the center begin to show wear and tear.

What common conditions or disorders affect the lens of the eye?

Aging and environmental factors like sunlight eventually take their toll on your eye lens, particularly the older crystallin cells in the center. When these cells start to break down, they lose some of their transparency and become cloudy. This is what age-related cataracts are. As eye lenses age, they also become less flexible and less able to change shape to focus on objects close-up. This is what age-related presbyopia is.

What are the symptoms of a problem with your eye lens?

Cataracts (cloudy spots on your eye lens) make your vision blurry or foggy. You might feel like you’re viewing the world through a dirty window. They often start in one spot and then spread. From the outside, they make your pupil, the dark spot in your eye, look cloudy, more like gray or white than black. (Babies can be born with cataracts related to genetic disorders, and this is one way to recognize them.)

When your lens starts to become less flexible and lose its focusing ability, you’ll start to have trouble focusing on things close-up. Presbyopia is essentially farsightedness (hyperopia) that happens with aging. You might find yourself holding reading materials farther away from you to read. Or you might just notice that your eyes get tired from reading or doing close work more easily than they used to.

How do healthcare providers treat eye lens issues?

Like other common refractive errors, you can correct presbyopia in a variety of ways, including:

• Eyeglasses.
• Contact lenses.
• Eye drops.
• Vision correction surgery.

Your eye care specialist can walk you through the different options and which ones might work best for you. You might benefit from different treatments over time, as aging continues to affect your vision.

Cataract surgery is the only treatment for cataracts. During this common procedure, a surgeon removes your clouded eye lens and replaces it with a new, artificial lens (intraocular lens, or IOL).

Surgeons can also replace your eye lens with an IOL before you develop a cataract to correct refractive errors like myopia, hyperopia or presbyopia. In this case, it’s called refractive lens exchange.

How can I take care of my eye lenses?

While age-related wear and tear on your eye lenses is inevitable, taking care of your eyes can help delay the process and minimize the damage. That means protecting your eyes from UV rays with sunglasses and avoiding environmental pollutants as much as possible, particularly smoking and secondhand smoke. Having diabetes can increase your risk of cataracts. Managing it well can help reduce that risk.

A note from Cleveland Clinic

The lens of your eye is a unique structure that’s crucial for seeing clearly. Over time, the cells in your eye lens can start to wear out and lose some of their focusing ability. You might notice your vision becoming cloudy or your focus becoming strained as you age. Regular eye health checkups can help you keep track of the wear and tear on your eye lens. Your provider can offer treatments to help recover your vision.