New eye drops could help older people see better

Summary: By the time most of us reach our 40s, our near vision begins to decline and we develop presbyopia. A new eye drop called Vuity claims to relieve symptoms of presbyopia, giving people clearer vision without the need for glasses or surgery. Researchers are investigating the potential benefits of taking Vuity for people with presbyopia.

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When people get into their 40s and older, their close-up vision begins to deteriorate. For many people, increasing the font size on a phone or maximizing brightness on a computer is the only way to read some text.

This condition is known as presbyopia and affects approximately 128 million people in the US and over a billion people worldwide.

In late 2021, the U.S. Food and Drug Administration approved a new eye drop drug to treat presbyopia. As an optometrist, I was skeptical at first. Prior to dispensing these eye drops — called Vuity — people would require either glasses, contact lenses, or eye surgery to relieve presbyopia. But after learning how these eye drops work, I realized that they could provide an easier and safer way for many people to see clearly again.

How to focus eyes

Many parts of the human eye interact with incoming light to produce a clear image.

The first thing that light hits is the cornea, the clear outer layer that initially bends light. Then the light passes through the iris and pupil, which can shrink or grow to let more or less light into the eye. It then travels through the lens, which bends the light further and focuses exactly on the center of the retina. Finally, the light signal is transmitted to the optic nerve at the back of the eye so that the brain can interpret it as an image.

To get a clear view, your eyes have to adjust to the distance from an object. Your eyes take three important steps to focus on objects close to your face: your eyes point at the object you want to look at, your lenses change shape, and your pupils constrict.

Once you focus your gaze on what you are interested in, a small muscle in the eye contracts, changing the shape of the lens to make it thicker. The thicker the lens, the more the light bends as it passes through it. At the same time, your pupils constrict to block some of the incoming light from other distant objects.

When light bounces off an object and enters your eye, the light rays in the center provide a clear image. By blocking the scattered light by constricting the pupil, the image of nearby objects becomes sharper.

You can simulate this process with a camera on your mobile phone. Point the camera at something in the distance first. Then move your thumb in the image and hold it about 6 inches (15 cm) away from you. Your thumb starts out blurry, but as the camera’s lens changes shape, your thumb comes into focus.

What is presbyopia?

Presbyopia is the inability of the eyes to focus on near objects, resulting in blurry images. It starts when people are in their 40s and progresses until it reaches a plateau around age 60.

Researchers know that age is the leading cause of presbyopia, but there is an ongoing debate about the mechanical causes underlying it.

One theory suggests that as lenses get older, they get heavier and don’t change shape as easily. Another theory suggests that the muscle that pulls on the lens weakens with age. I suspect that presbyopia probably occurs due to a combination of both. Whatever the cause, the result is that when looking at objects up close, people’s eyes are no longer able to bend incoming light enough to focus it toward the center of the retina. Instead, the light is focused on a spot behind the retina, resulting in blurry vision.

How the eye drops work

Remember that there are two main things an eye does to focus on near objects: the lens changes shape and the pupil shrinks. Because presbyopia limits the lens’ ability to change shape, these eye drops compensate by causing the pupil to shrink.

Nearly all people begin to develop blurred vision in their 40s or 50s. Image is in the public domain

By constricting the pupil, the amount of light scattering is reduced. This allows the light entering the eye to be better concentrated on the retina, creating a wider range of distances where objects are in focus and people can see objects near and far clearly.

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Once you put the drops in your eyes, it takes about 15 minutes for the active ingredient, pilocarpine, to start working. Pilocarpine is a drug first discovered in the late 1800s that can treat conditions such as glaucoma and ocular hypertension. The effect on students lasts for about six hours.

Smaller pupils allow less light to enter the eye. While this isn’t a problem during the day when there’s a lot of sun, it can cause vision problems in low light. Aside from these drawbacks, the most common side effects of the drops are headaches and red eyes.

Presbyopia in the future

Vuity is currently approved for once-daily use in each eye. A bottle costs about $80, requires a prescription, and lasts nearly a month if used daily. For some people, it can be a great alternative or addition to glasses or surgery.

While Vuity may be the first FDA-approved eye drops to treat presbyopia, researchers are studying a number of other approaches. Some are developing eye drops containing nonsteroidal anti-inflammatory drugs to help constrict the pupil — just like with Vuity. Other teams are studying drops that soften the lens and reduce its weight for easier focusing. Finally, some early research has shown that pulsed electrical stimulation of eye muscles can help strengthen them and improve people’s ability to bend their lenses.

The future of presbyopia treatment is exciting as researchers work on many possible ways to overcome this universal condition of old age. For now, Vuity—while not a panacea for everyone with presbyopia—is an innovative option and may be worth asking your eye doctor.

About this research news on visual neuroscience and pharmacology

Writer: Robert Bittner
Source: The conversation
Contact: Robert Bittner – The Conversation
lmagician: The image is in the public domain

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