When people reach their forties and beyond, their close-up vision begins to deteriorate. For many people, increasing the font size on their phone or increasing the brightness on their computer is the only way to read some text.
Presbyopia is a condition that affects approximately 128 million people in the United States and over a billion people worldwide.
The US Food and Drug Administration approved a new eye drop medication to treat presbyopia in late 2021. As an optometrist, I was skeptical at first.
Prior to the introduction of these Vuity eye drops, people had to rely on glasses, contacts, or surgery to treat presbyopia. However, 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 eyes focus
To produce a clear image, many parts of the human eye interact with incoming light.
The cornea, the clear outer layer that initially bends light, is the first thing light hits. The light then passes through the iris and pupil, which can shrink or expand to allow more or less light into the eye. It then passes through the lens, which bends the light even more and precisely focuses it on the retina's center. Finally, the light signal is transmitted to the optic nerve at the back of the eye, where it is interpreted by the brain as an image.
To produce a clear image, your eyes must adjust to the distance of an object. To focus on objects close to your face, your eyes take three major steps: your eyes point toward the object, your lenses change shape, and your pupils constrict.
When you direct your gaze toward something of interest, a small muscle in the eye contracts, changing the shape of the lens and making it thicker. The light bends more as it passes through a thicker lens. Simultaneously, your pupils constrict to block some of the incoming light from other distant objects.
The rays of light at the center of the image are what provide a clear image when light bounces off an object and enters your eye. Constricting the pupil helps to sharpen the image of close objects by blocking scattering light.
You can simulate this process by using your cellphone's camera. To begin, aim the camera at something in the distance. Then, insert your thumb into the image, about 6 inches away. Your thumb will be blurry at first, but as the camera's lens changes shape, it will come into focus.
Presbyopia stiffens the lens in the eye, and when a person can't bend their lens as easily, they can't focus incoming light on the correct part of the retina, resulting in blurry images.
What is presbyopia ?
Presbyopia is the inability of the eyes to focus on close objects, resulting in blurry images. It starts in the 40s and continues until the age of 60.
Researchers know that age is the primary cause of presbyopia, but there is still debate about the mechanical causes.
According to one theory, as lenses age, they become heavier and are less able to change shape as easily. Another theory holds that the muscles that pull on the lens weaken with age. I believe presbyopia is caused by a combination of both.
Whatever the cause, the result is that when looking at close objects, people's eyes are no longer able to bend incoming light enough to direct it at the center of the retina. Instead, the light is focused behind the retina, resulting in blurry vision.
How the eye drops work
To focus on close objects, the lens changes shape and the pupil shrinks. Because presbyopia limits the lens's ability to change shape, these eye drops compensate by making the pupil smaller.
The amount of light scatter is reduced when the pupil is constricted. This causes light entering the eye to be more concentrated on the retina, resulting in a wider range of distances where objects are in focus and allowing people to see both close and far objects clearly.
It takes about 15 minutes for the active ingredient, pilocarpine, to begin working after you place the drops in your eyes. Pilocarpine is a medication that was discovered in the late 1800s and can treat conditions such as glaucoma and ocular hypertension. The effect on pupils lasts about six hours.
Less light enters the eye when the pupils are smaller. While this isn't an issue during the day when there's a lot of sunlight, it can make it difficult to see in low-lighting conditions. Aside from these drawbacks, the drops' most common side effects are headache and red eyes.
Making the pupil smaller and allowing less light into the eye increases depth of field, making closer objects appear in focus – as shown in diagram an above – versus a larger pupil and narrower depth of field, as shown in diagram b.
Presbyopia in the future
Vuity is currently approved for use in both eyes once daily. A bottle will cost around $80, will require a prescription, and will last almost a month if used daily. It could be an excellent alternative or supplement to glasses or surgery for some people.
While Vuity may be the first FDA-approved eye drops for the treatment of presbyopia, researchers are looking into a variety of other options. Some researchers are working on eye drops containing nonsteroidal anti-inflammatory drugs to help constrict the pupil – similar to Vuity.
Other research groups are looking into drops that soften and lighten the lens to make it easier to focus. Finally, preliminary findings indicate that pulsed electrostimulation 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 a variety of potential solutions to this universal condition of aging. For the time being, Vuity is an innovative option that may be worth discussing with your eye doctor.