Source: The conversation
When people reach the age of 40 and beyond, their foreground vision begins to worsen. 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 United States and more than a billion people worldwide.
In late 2021, the U.S. Food and Drug Administration approved a new drug with eye drops to treat presbyopia. As an optometrist, I was initially skeptical. Before the release of these eye drops, called Vuity, people would need glasses, contact lenses, or eye surgery to relieve presbyopia. But after learning how these eye drops work, I recognized that for many people they could offer an easier and safer way to see it clearly again.
How the eyes focus
Many parts of the human eye interact with incoming light to produce a clear image.
The first thing that strikes the light is the cornea, the transparent outer layer that initially bends the light. The light then passes through the iris and pupil, which can shrink or grow to allow more or less light to enter the inside of the eye. It then travels through the lens, which further bends the light and focuses it precisely in the center of the retina. Finally, the light signal is transferred to the optic nerve in the back of the eye, so that the brain can interpret it as an image.
To produce a clear image, your eyes must be adjusted to the distance of an object. Your eyes take three main steps to focus on objects close to your face: your eyes point to the object you want to look at, your lenses change shape, and your pupils contract.
Once you look at what interests you, a small muscle in the eye contracts, which changes the shape of the lens to make it thicker. The thicker the lens, the more light it bends as it passes through it. At the same time, your students are restricted from blocking some of the light entering other objects in the distance.
When light bounces off an object and enters your eye, the center rays of light are the ones that provide a clear picture. Blocking scattered light by restricting the pupil helps to improve the image of nearby objects.
You can simulate this process with a 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 away. Your thumb will start to blur, but as the camera lens changes shape, your thumb will focus.
What is presbyopia?
Presbyopia is the inability of the eyes to focus on nearby objects, resulting in blurred images. It starts when people are 40 years old and progresses until it flattens out at age 60.
Researchers know that age is the main driver of presbyopia, but there is an ongoing debate about the root causes of mechanics.
One theory suggests that as lenses age, they become heavier and cannot change shape as easily. Another theory suggests that the muscle that stretches the lens becomes weaker with age. I suspect presbyopia is probably due to a combination of both. Regardless of the cause, the result is that when looking at nearby objects, people’s eyes are no longer able to bend the light that enters enough to direct it to the center of the retina. Instead, light is focused in a place behind the retina, resulting in blurred vision.
How eye drops work
Remember that there are two main things an eye does to focus on nearby objects: 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.
Pupil restriction reduces the amount of light scattering. This allows the light entering the eye to focus better on the retina, creating a wider range of distances where objects are focused and allowing people to see objects near and far clearly.
Once the drops are in the eyes, the active ingredient, pilocarpine, takes about 15 minutes to start working. Pilocarpine is a drug that was first discovered in the late 19th century and can treat conditions such as glaucoma and high blood pressure. The effect on students lasts about six hours.
Smaller pupils cause less light to enter the eye. While this is not a problem during the day when it is very sunny, it can cause difficulty seeing in low light conditions. Aside from these drawbacks, the most common side effects of gout are headaches and red eyes.
Presbyopia in the future
Vuity is currently approved for use once a day in each eye. A bottle will cost about $ 80, require a prescription, and last almost a month if used daily. For some people, it could be a great alternative or complement to glasses or surgery.
While Vuity may be the first FDA-approved eye drop to treat presbyopia, researchers are studying a number of other approaches. Some are developing eye drops that include nonsteroidal anti-inflammatory drugs to help shrink the pupil, similar to Vuity. Other teams are studying drops that soften and reduce the weight of the lens to make it easier to focus. Finally, some early research has shown that pulsed electrostimulation of the eye muscles can help strengthen them and improve people’s ability to bend their lenses.
The future of presbyopia treatment is exciting, as researchers are working on many potential ways to overcome this universal condition of old age. For now, Vuity, while not a magical cure for everyone with presbyopia, is an innovative option and may be worth asking your ophthalmologist.
About this research news in visual neuroscience and pharmacology
Author: Robert Bittner
Source: The conversation
Contact: Robert Bittner – The Conversation
jomag: The image is in the public domain