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Your eye may look smooth and uniform, but it could have subtle dips and valleys. Those shape shifts can change the way light moves through your eye, and that could reduce your visual acuity. Major alterations in eye shape are known as higher order aberrations (HOAs). They can lead to bothersome vision difficulties your doctor can't fix with glasses or contact lenses.
Your vision issues may be affected by:
- Dry eyes.
- LASIK surgery.
- Cataract surgery.
Working with a talented doctor is critical. Planning done before any eye surgery and therapies given for dry eye can ensure that you see as clearly as possible despite the presence of HOAs.
How Aberrations Alter Vision
Your eye is a delicate organ that is designed to focus light on a tiny area of cells near the optic nerve. HOAs alter focusing power, and that can lead to bothersome symptoms your doctor can't fix with glasses.
Look closely at a pencil on your desk. You can see that implement because your eyes take in the light around it, and that image moves through the eye and is pointed at the macula. The tighter the beam is focused on the macula, the crisper the image will seem to you.
Higher order aberrations change the way light moves. A few strands of light will point near, but not on, the macula.
Researchers writing in The Optometrist say that people with HOAs can still read, knit, and do close work. They can also see items at a distance. But they can struggle with:
- Light vision.
- Haloes around bright lights.
- Blurred images.
Traditional vision solutions, like glasses and contacts, correct for problems shared by every cell in the eye. For example, prescription glasses for nearsightedness put a powerful lens in front of the entire eye, so the focusing power of the whole organ is changed.
HOAs touch only one small part of the eye. A lens made for the entire organ will not fix the problem. In fact, it might make the issues feel even more noticeable.
Instead, doctors must determine what's causing the HOA. In some cases, they can correct it with simple solutions.
Symptoms of High Order Aberrations
Individuals with larger pupils are more likely to develop high-order aberrations (HOA) than people with normal or smaller pupils. But in some instances, higher order aberrations occur together with other eye conditions, including first-order abnormalities. The mix-up of symptoms might make the diagnosis of HOA tricky.
The common signs and symptoms associated with higher order aberrations include:
- Double vision or diplopia
- Poor night vision
- Starburst effect
- Ghost images
- Rings around objects (halos)
- Blurry images
There are more than 60 types of HOAs, and they manifest in different ways. The highly specific symptoms of high order aberrations make diagnosis and treatment difficult.
Treatment for HOA
Because high order aberrations result primarily from defects in eye structure such as tissue scarring, ocular misshapenness and cataracts, surgery is one of the treatment options currently used. Intraocular lenses and glasses can also correct the conditions.
Wavefront LASIK is one of the leading surgical interventions in correcting HOAs. First, the doctor uses an aberrometer to reflect light on your eye and capture its model or contour in detail. The detailed map of your eye is then entered into a computerized laser system to help modify the shape of your eye through LASIK surgery.
Apart from correcting high order visual abnormalities, wavefront LASIK reduces the risk of glare, diplopia, and other distortions that often occur following refractive eye surgeries.
Can Dry Eyes Make Them Worse?
Each time we blink, we add nutrition and protection to our eyes. If we do not blink often enough or our tears are thin or otherwise ineffective, our eyes are unprotected, and that can make HOAs worse.
Think of higher order aberrations as ridges and valleys on the surface of the eye. A lack of tears could lead to:
- Pulling. Tight, dry tissues tend to shrink. Deepening gaps can form when tissues are not plump.
- Clumping. Dry tissues stick together, leading to more hills and lumps on the eye's surface.
- Tearing. Micro-sized tears form when there is not enough fluid to keep the eye lubricated. Those can heal as valleys or ridges.
Eyedrops can work wonders. Researchers writing in the Journal of Ophthalmology report that two weeks of treatment with lubricating eye drops lead to a measurable decrease in HOAs in those with dry eyes.
Your doctor can measure tear production with a simple, in-office test. If your eyes are dry, eyedrops can be part of your daily routine. In time, your eyes could heal enough to make your HOAs easier to ignore.
Can LASIK Surgery Make Them Worse?
LASIK will not make higher order aberrations of the eye worse if you choose an experienced surgeon who uses the latest technology.
Traditional LASIK without pre-surgical mapping can make higher order aberrations worse, especially in people with nearsightedness. But newer procedures are customized, and they can help your doctor correct some HOAs.
The American Academy of Ophthalmology reports that HOAs can potentially increase after this type of surgery, especially in people with nearsightedness. In fact, the more nearsighted you are, the more likely you will have an HOA after the procedure, the organization says.
Waveform LASIK is different. Here, doctors use a tool to create a map of the eye's surface. Then, they follow that topography during your surgery. In some cases, doctors can determine where an HOA is located and shave off tiny bits of tissue to make its impact disappear.
When this technology was introduced in the 2000s, researchers got excited. In an article in Ocular Surgery News, an expert expressed his hope that this surgery would lead to "super-normal visual acuity." That has not happened quite yet.
Experienced doctors using this technology can reduce HOAs. That is why it's crucial for you to talk with your surgeon before you schedule LASIK. Make sure you are working with someone who understands your eyes and your needs, so you will get advanced care that leads to better vision.
Can Cataract Surgery Make Them Worse?
Cataract surgery involves replacing a lens that sits inside the eye. There are many different types of lenses for your doctor to choose from, and some can make an HOA harder to ignore.
Some lenses used in cataract surgery scatter focal points. A lens like this helps you to use different parts of the eye, so you can focus on things both near and far without slipping glasses on and off. These lenses can seem ideal for someone who wants a glasses-free future, but if you have an HOA, they could be a poor choice for you.
Consider this: A lens with a key focal point could sit beneath your HOA. When that happens, that spot will always produce a blurry image. If this is the portion of the lens you planned to use for distance vision, this could be frustrating.
Doctors writing in the journal Investigative Ophthalmology and Visual Science say it's crucial for patients to have waveform testing before cataract surgery, so their doctors will know where HOAs are and can make a good lens recommendation. Without that test, you may not have the data you need to choose the right lens solution.
Higher Order Aberrations vs. Lower Order Aberrations
Aberration refers to any deviation in the normal vision and can be either lower or higher order. The lower order aberrations are more common. They make up 85 percent of vision issues.
LOAs include myopia, farsightedness, astigmatism, and presbyopia. On the other hand, the higher order aberrations like trefoil, coma and spherical aberrations are largely undiagnosed and untreated. HOAs have a more nuanced eyeball distortion than the first-order aberrations.
Higher and lower order distortions can occur simultaneously. Both respond to surgical treatment and other forms of management, such as contact lenses and eyeglasses.
Talk With Your Doctor
It's important to talk with your doctor before any kind of surgery. But if you've been living with blurred, uncomfortable, or unusual vision for years, it's especially important to be clear with your doctor.
Talk about your:
- Symptoms. Do you see better or worse in low light? What happens when you drive? Do you have blurry patches, or is your entire visual field askew?
- Expectations. Will you be satisfied with slightly better vision, or do you hope for perfection?
- Concerns. What worries you about the solution your doctor proposes? What would make you feel better?
- History. What have you tried in the past, and how did that help or harm your eyes?
Together, you and your doctor can find a solution that is right for you and your eyes.
How to Reduce Higher-Order Aberrations. (May 2014). The Ophthalmologist.
Changes of Corneal Wavefront Aberrations in Patients After Treatment With Artificial Lubricants. (February 2016). Journal of Ophthalmology.
Higher-Order Aberrations. American Academy of Ophthalmology.
Wavefront-Guided LASIK Can Decrease Aberrations and Increase Visual Acuity. (2000). Ocular Surgery News.
Incidence and Type of Higher Order Corneal Aberrations in the Cataract Population. (June 2013). Investigative Ophthalmology and Visual Science.
Higher-Order Aberrations in Myopic Eyes. (January 2010). NCBI.
Higher-Order Aberrations. (March 2019). All About Vision.