When your vision gets worse, it’s easy to think of it as one problem: your eyesight is going.
But poor vision isn’t caused by just one thing.
Two people can walk into an eye surgeon’s office with the exact same complaint—”My vision is blurry and I want to see better”—and need completely different treatments.
A 30-year-old who has worn contact lenses for years may be an excellent candidate for LASIK. A 60-year-old with changing vision may be better suited to lens replacement.
The key is understanding which part of the eye is causing the problem.
I’m Dr. Scott Spector, an eye surgeon, and I like to simplify the eye by thinking about it like a car. There are windshield problems and engine problems.
The “Windshield”: Your Cornea and Tear Film
Start at the front of the eye.
The cornea is the clear dome covering the front of your eye. A thin layer of tears, called the tear film, covers it every time you blink.
Together, they form the optical surface of your eye and provide much of its focusing power.
There are two common problems here.
An Unstable Tear Film
If the tear film breaks up too quickly, your vision may fluctuate.
You might notice that things become blurry throughout the day and then sharpen after you blink. Symptoms may also be worse after hours of screen use, reading, driving, or sitting near a fan or air vent.
This is a surface problem—and there are several ways to treat it, including artificial tears, prescription medications, eyelid treatments, and, in appropriate patients, procedures such as punctal plugs.
The Shape of the Cornea
The cornea also needs to have the right shape.
If its curvature doesn’t match the length of your eye, light won’t focus precisely on the retina. This can result in nearsightedness, farsightedness, or astigmatism.
Glasses and contact lenses correct these problems by changing how light enters the eye.
But in some patients, we can change the shape of the cornea itself.
The “Engine”: Your Natural Lens
Behind the iris is the natural lens of your eye.
When you’re young, this lens is clear and flexible. As you age, it gradually becomes stiffer and eventually may become cloudy.
The loss of flexibility is responsible for presbyopia, which is why most people eventually need reading glasses.
As the lens becomes cloudy, it develops a cataract.
You may notice increasing glare, difficulty driving at night, needing more light to read, or vision that isn’t as sharp as it once was even with glasses.
These are different from a corneal or tear-film problem because the source is inside the eye.
There Is One More Part to Consider
At the back of the eye is the retina, along with the optic nerve that carries visual information to the brain.
Problems involving the retina or optic nerve are different from the refractive problems discussed above. They may require medical treatment rather than glasses or refractive surgery.
Changes such as a new blind spot, distorted straight lines, sudden vision loss, flashes, or a sudden increase in floaters should be evaluated promptly by an eye-care professional.
For most people who simply need vision correction, however, the problem is related to the optical system at the front or middle of the eye.
So How Do We Fix Poor Vision?
Once we know what’s causing the problem, the treatment becomes much easier to understand.
If It’s the Tear Film
We treat the surface of the eye.
Depending on the cause, that might involve lifestyle changes, artificial tears, prescription medications, eyelid treatment, or other procedures.
The goal is to create a healthier, more stable optical surface.
If It’s the Cornea
For an appropriate younger patient, we may be able to reshape the cornea with LASIK or PRK.
The laser changes the curvature of the cornea so that light focuses more precisely on the retina.
Not everyone is a candidate. Corneal thickness, shape, prescription, ocular health, age, and other factors all need to be considered.
For patients who aren’t good candidates for corneal laser surgery, another option may be an implantable lens.
If It’s the Natural Lens
When the natural lens has developed significant age-related changes, lens replacement surgery may be the better approach.
The natural lens is removed and replaced with an artificial intraocular lens.
Modern lens options can be selected based on the patient’s prescription, eye anatomy, lifestyle, and visual goals. For some patients, this can significantly reduce their dependence on glasses.
Why Age Matters
Consider the two patients from the beginning.
The 30-year-old has a clear, flexible natural lens that’s still doing its job. If the cornea is healthy and the patient is a good candidate, reshaping the cornea with LASIK or PRK may make sense.
The 60-year-old is different.
The natural lens is already undergoing age-related changes. In that situation, simply reshaping the cornea may correct today’s prescription without addressing what is happening to the lens.
For some patients, lens replacement can address both the refractive error and the aging natural lens at the same time.
That doesn’t mean everyone over a certain age needs lens surgery, or that younger patients can’t have other options. It means that age is one piece of a much larger picture.
Don’t Just Ask, “What’s My Prescription?”
The next time you have an eye examination, don’t just ask what your glasses prescription is.
Ask:
“Which part of my eye is causing my prescription?”
Is it primarily the cornea? The natural lens? The tear film? Or is there another issue?
The answer can tell you much more about what your future options might be.
That’s why a comprehensive evaluation is so important. The right procedure can’t be chosen from a prescription alone. Your eyes need to be measured and evaluated as a whole.
The Bottom Line
Your eyes aren’t simply “getting worse.”
Something specific is happening, and identifying where that problem is occurring is the first step toward understanding what can be done about it.
For some people, the answer is treating the tear film.
For others, it’s correcting the shape of the cornea
