By: Anna Kiesewetter
For many of us, a chart of shrinking alphabet letters—known as the Snellen chart—is an all-too-familiar sight. When we see these charts, we line up in front of them and alternate between covering our left and right eyes, trying to determine the smallest set of letters we can correctly distinguish. This is a common occurrence for young children in many states, as most elementary schoolers have their vision tested annually at school. It is an important process, as children of this age are in a key developmental period, one where most instances of myopia begin to show up. Of course, some may be wondering: what exactly is myopia, and why do our eyes need to be tested for it?
Myopia is the medical term for nearsightedness, a condition in which it is difficult for a person to see faraway objects. Those with myopia are able to see nearby objects with greater clarity, hence the term ‘nearsightedness.’ Nearsightedness typically develops during childhood and worsens during adolescence while the eyes are still developing. Its symptoms include blurred vision (especially viewing faraway objects), headaches from eyestrain, and impaired night vision. Nearsightedness is typically corrected using prescription glasses, contact lenses, or refractive surgery such as Laser-Assisted In Situ Keratomileusis (LASIK).
However, not all cases of myopia are equal; some may be worse than others. In fact, when one’s level of nearsightedness reaches -6 dioptres (D) or greater spherical correction, their severe eye condition is no longer labelled as myopia. It is instead known as high myopia. This condition affects 9.8% of the global population and is particularly prevalent in young adults in both eastern and southeast Asian countries. There are two primary ways one can obtain high myopia. In some cases, high myopia is inherited as a genetic condition. However, more commonly, individuals develop it. Myopia is a progressive condition, meaning that it can get worse over time. As such, the development of high myopia in younger individuals is often a concern. After all, the eyes of young individuals are still developing, and as a result, the power, or level, of myopia can increase significantly as they grow. High myopia is often developed through high exposure to blue light as well as other long-term tasks that require high focus and result in eye strain.
While high myopia on its own does not necessarily lead to blindness, the condition can increase the risk factors for several serious conditions which sometimes lead to blindness. Such conditions include glaucoma, cataracts, and retinal detachment.
Glaucoma refers to a group of eye conditions in which the optic nerve is damaged in response to too much eye pressure and/or a buildup of the eye’s fluid, which is called aqueous humor. It involves slow vision loss as neural messages have difficulty moving to the brain. Glaucoma can cause blindness, and certain types of glaucoma, such as angle-closure glaucoma, are considered to be emergency conditions, as they involve severe eye pain. Having high myopia increases the risk of glaucoma by 50%, so it’s very important to have your eyes checked for signs of glaucoma at your eye exams, particularly if you have high myopia.
Cataracts involve a clouding of the lens in the eyes. The lens is the part of the eye that focuses light waves and sends them to the retina. Since the retina is normally clear, this clouding can result in one experiencing blurred vision, faded color, and a halo viewed around lights. Cataracts generally develop slowly and become more severe over time. The risk of getting cataracts is increased by 17% in patients with high myopia, so, once again, patients with high myopia should have their vision checked for cataracts, especially as they get older.
Having high myopia additionally increases the risk of retinal detachment by 5-6 times. Our retinas are the part of our eyes that transduce visual sensations, or light waves, into neural signals sent along the optic nerve to the brain for processing. People with nearsightedness have longer eyes, which is known as axial elongation, as well as a degenerate vitreous, the gel-like fluid within our eyes. These conditions stretch the retina, increasing the risk of retinal tears and subsequent detachment. Warning signs of retinal detachment include sudden floaters, flashes of light, or shadows over the visual field. If you experience any of these symptoms, especially if you have high myopia, get emergency care right away to prevent retinal detachment and potential blinding.
It’s important to have your eyes checked regularly, especially if you have high myopia. Right now, with virtual learning increasing our screen time and putting a great amount of strain on our eyes, it’s more important than ever that we take care of our vision. Participating in annual eye exams with those charts of shrinking letters is a necessary step to ensure that you’re watching out for the risks of these potentially debilitating eye conditions.
What Did You Learn?
1. What is the retina? What are the symptoms of retinal detachment?
The retina is the part of the eye that transduces visual images into neural signals that are sent along the optic nerve to be processed in the brain. Symptoms of retinal detachment include sudden floaters, flashes of light, or shadows covering the visual field. If you experience any of these symptoms, see a doctor right away.
2. How can we monitor the state of our vision?
It’s important to get annual check-ups with a licensed eye doctor. They can run tests and look at your eyes to check for myopia as well as chronic conditions like glaucoma, cataracts, and risk of retinal detachment. This will help you keep track of your vision and mitigate any potential signs of these chronic conditions early on.