(ORDO NEWS) — When people are in their 40s or older, their near vision begins to deteriorate. For many people, increasing the font size on a phone or maximizing the brightness on a computer is the only way to read text.
This condition is known as presbyopia and affects about 128 million people in the US and more than a billion people worldwide.
In late 2021, the US Food and Drug Administration approved a new drug in the form of eye drops to treat presbyopia. As an optometrist, I was initially skeptical.
Before these eye drops, called Vuity, people needed either glasses or contact lenses or eye surgery to relieve presbyopia. But after studying how these eye drops work, I realized that for many people they can offer an easier and safer way to see clearly again.
How the eyes are focused
Many parts of the human eye interact with incoming light to produce a sharp image.
The first thing light hits is the cornea, the transparent outer layer that initially deflects the light. The light then passes through the iris and pupil, which may shrink or enlarge to let more or less light into the eye.
It then passes through the lens, which bends the light even more and focuses it precisely on the center of the retina. Finally, the light signal is sent to the optic nerve at the back of the eye for the brain to interpret as an image.
To get a clear image, the eyes must adjust to how far away the object is. To focus on objects close to the face, the eyes perform three basic actions: the gaze is directed to the object you want to look at, the lenses change shape, and the pupils constrict.
When you look at an object of interest, a small muscle in the eye contracts, which changes the shape of the lens, making 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 objects in the distance.
When light bounces off an object and hits the eye, the light rays in the center create a sharp image. Blocking stray light by constricting the pupil helps to make close objects appear clearer.
You can simulate this process using the camera on your mobile phone. First, point the camera at something in the distance. Then move your thumb over the image, keeping it about 6 inches apart. At first, the finger will be blurry, but as the camera lens changes shape, the finger will come into focus.
What is presbyopia?
Presbyopia is the inability of the eyes to focus on close objects, resulting in blurry images. It begins at the age of 40 and progresses until it reaches a plateau around the age of 60.
Researchers know that age is a major factor in the development of presbyopia, but debate continues about the mechanical causes underlying it.
According to one theory, lenses become heavier with age and cannot change shape as easily. Another theory suggests that the muscles that pull on the lens become weaker with age. I suspect presbyopia is most likely due to a combination of both.
Regardless of the cause, the result is that when looking at close objects, the human eye is no longer able to bend the incoming light enough to direct it to the center of the retina. Instead, the light is focused behind the retina, resulting in blurry vision.
How eye drops work
Remember that in order to focus on close objects, the eye does two main things: the lens changes shape, and the pupil becomes smaller. Because presbyopia limits the ability of the lens to change shape, these eye drops compensate by causing the pupil to shrink.
Constriction of the pupil reduces the scattering of light. Thus, the light entering the eye is better concentrated on the retina, which creates a wider range of distances at which objects are in focus, and allows people to see both near and far objects clearly.
After you put the drops in your eyes, the active substance pilocarpine begins to act in about 15 minutes. Pilocarpine is a drug first discovered in the late 1800s that can treat conditions such as glaucoma and ocular hypertension. The effect on the pupils lasts about six hours.
Smaller pupils mean less light enters the eye. Although this is not a problem during the day when there is a lot of sun, it can cause vision problems in low light conditions. Apart from these drawbacks, the most common side effects of the drops are headache and eye redness.
Presbyopia in the future
Vuity is currently approved for once daily use in each eye. The bottle costs about $80, requires a prescription, and lasts almost a month with daily use. For some people, this can be a great alternative or addition to glasses or surgery.
While Vuity may be the first FDA-approved eye drops for treating presbyopia, researchers are exploring a number of other approaches. Some of them are developing eye drops that include non-steroidal anti-inflammatory drugs that help constrict the pupil – similar to Vuity.
Other teams are studying droplets that soften and reduce lens weight to make focusing easier. Finally, some early research has shown that pulsed electrical stimulation of the eye muscles can help strengthen them and improve people’s ability to bend lenses. Talk
The future of presbyopia treatment is very exciting as researchers work on many potential ways to overcome this universal condition of old age. For now, Vuity – while not a magic cure for all people with presbyopia – is an innovative option that you might want to ask your ophthalmologist about.
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