Myopia (nearsightedness) and astigmatism are the two most common refractive errors, meaning they both cause blurry vision because light doesn’t focus correctly on the retina. They often occur together. In one clinical study of 370 myopic patients, 77.3% also had astigmatism. Despite that overlap, they blur your vision in different ways and for different reasons.
How Myopia Works
In a normally shaped eye, light passes through the cornea and lens and lands precisely on the retina at the back of the eye. In myopia, the eyeball is slightly too long from front to back, or the cornea curves too steeply, so light converges in front of the retina instead of on it. The result: close objects look sharp, but anything at a distance appears blurry.
The global prevalence of myopia has surged from about 23% of the population in 2000 to an estimated 34% in 2020, and projections suggest it will reach 50% by 2050. Among children and adolescents specifically, prevalence climbed from 24.3% in 1990 to 35.8% in 2023. Much of this increase tracks with lifestyle shifts: more time on screens, less time outdoors. Outdoor light exposure at least five days a week is one of the most well-established protectors against myopia progression in kids, while extended screen use shows a dose-dependent relationship with worsening nearsightedness.
How Astigmatism Works
Astigmatism has a different root cause. Instead of the cornea (or sometimes the internal lens) being shaped like a basketball with one uniform curve, it’s shaped more like an egg or a football, with one meridian curving more steeply than the other. Because light bends differently through these two mismatched curves, it creates two focal points instead of one. Those two images overlap, producing vision that’s blurry, shadowed, or slightly doubled.
A key distinction: myopia only blurs distant objects, while astigmatism blurs vision at all distances. You can have mild astigmatism without noticing it, or enough that reading, driving, and everything in between looks soft or distorted.
Symptoms Compared
The hallmark of myopia is blurry distance vision. You might squint at road signs, struggle to read a whiteboard, or find yourself holding your phone closer than other people do. Frequent prescription changes, especially during childhood, are another telltale sign.
Astigmatism shares some of those symptoms but adds its own signature. Vision may appear ghosted or shadowed rather than simply out of focus. You might notice halos or streaks around lights at night. Headaches and eyestrain after prolonged close-up work are common because your eye is constantly trying to compensate for the uneven focus. Some people with astigmatism also experience double vision in one eye alone, something myopia on its own doesn’t cause.
Both conditions cause squinting and headaches, so the overlap in everyday symptoms is real. An eye exam is the only reliable way to tell which one you have, or whether you have both.
Reading Your Prescription
Your glasses or contact lens prescription actually spells out whether you have myopia, astigmatism, or both. The three key numbers are sphere, cylinder, and axis.
- Sphere (SPH): This is the lens power that corrects myopia or farsightedness. A minus sign means nearsighted; a plus sign means farsighted. The higher the number, the stronger the correction you need.
- Cylinder (CYL): This measures how much astigmatism you have. If this box is empty, you don’t have astigmatism. The number reflects the difference in curvature between the steepest and flattest meridians of your cornea.
- Axis: A number between 1 and 180 degrees that indicates the angle of your astigmatism on the cornea. It tells the lab which direction to orient the corrective curve in your lens.
So if your prescription reads -3.00 for sphere and -1.25 for cylinder, you have moderate myopia and mild astigmatism.
Correction Options
Standard spherical lenses correct myopia by spreading light rays so they focus farther back, landing on the retina. Astigmatism requires a different lens shape called a toric lens, which has two different powers built in at right angles to compensate for the cornea’s uneven curvature.
For people with both conditions, toric lenses handle everything in one lens. Research comparing toric and spherical contact lenses in people with myopia and low astigmatism found that patients achieved better visual sharpness with toric lenses, and 71% preferred them over spherical lenses. That said, people with very small amounts of astigmatism (around 0.50 diopters or less) can sometimes get by with a standard spherical lens using an averaged-out prescription.
Laser eye surgery is another option. LASIK can correct up to about 12 diopters of myopia and up to 6 diopters of astigmatism. A newer procedure called SMILE is approved for up to 10 diopters of myopia with up to 3 diopters of astigmatism. Both procedures reshape the cornea to redirect how light enters the eye, and they can treat myopia and astigmatism simultaneously.
Why Having Both Matters
Having myopia and astigmatism together doesn’t just mean two problems stacked on top of each other. It changes how your correction is approached. A purely spherical correction will leave residual blur from the astigmatism, which is why accurate measurement of both components matters for getting the sharpest possible vision. If you’ve ever felt like your glasses “almost” work but something still seems off, uncorrected or under-corrected astigmatism is a common reason.
Long-Term Risks of High Myopia
Astigmatism on its own doesn’t carry significant long-term risks to eye health. Myopia does, particularly at higher levels. High myopia (typically defined as a prescription beyond -6.00 diopters) stretches the eyeball and thins the retina, raising the risk of several serious conditions: retinal detachment, macular degeneration specific to myopia, and splitting of the retinal layers.
These structural changes also increase the likelihood of developing glaucoma. In a large global study, people with retinal complications from high myopia had roughly 1.75 times the adjusted odds of developing open-angle glaucoma compared to those without such complications. Certain complications carried even higher risk: retinal splitting tripled the odds, and myopia-related macular degeneration nearly tripled them as well.
This is why controlling myopia progression in children, through outdoor time, specialized contact lenses, or low-dose eye drops, has become a growing priority in eye care. The goal isn’t just clearer vision now but reducing the structural damage that accumulates over decades in highly myopic eyes.