What options do you have if you have high amounts of astigmatism? In this post, we’ll look at what astigmatism is, what causes it, and what can be done to correct it.
What is astigmatism?
Many people have astigmatism, but few understand it. Astigmatism is an irregularity of the cornea or the lens, a common refractive error that makes up about 13 percent of all refractive errors of the eye.
Many doctors will describe it as your eye being shaped more like a football than a baseball. In an eye without astigmatism, the cornea and lens have a round shape enabling the focus of sharp light rays on the retina. If you have astigmatism, the light rays do not bend properly upon entering the eye causing the light rays to fall in front of or behind the retina.
Astigmatism may cause blurry vision, eye strain, headaches, eye discomfort, and commonly, halo or glare around car lights or streetlights.
Astigmatism is measured as a numeric diopter value. Even though you may have some astigmatism, it may or may not be visually significant. Glasses can correct all amounts of astigmatism, while contacts are more limited. Most lens manufacturers make contacts in -2.25D or less.
If you have more severe astigmatism, you will need a lens with an extended range of astigmatism—a toric contact lens. Most doctors would consider an astigmatism of -3.00 or greater to be high.
What is the cause of astigmatism?
Despite much research, the exact cause of astigmatism is unknown. It is thought to be a combination of genetic and mechanical reasons. The mechanical cause would be due to interactions of the cornea, eyelids, and/or extraocular muscles.
A high amount of astigmatism tends to run in families and in certain populations of people. There are also some studies that show the amount changes with age. Babies are born with high amounts that should decrease as they get older. Young adults tend to have low amounts of astigmatism (under 1.00D). In adults older than 40, the astigmatism tends to move from horizontally across the cornea to vertically which may be due to a loss in eyelid muscle tone that comes with age.
You can also develop astigmatism from an eye disease, injury, eye condition, or after surgery. Corneal inflammation due to dry eye, a pterygium, and keratoconus are common eye conditions that cause changes in astigmatism. For this reason, if you have dry eye, your doctor prefers to treat it prior to your glasses/contact lens exam.
What options exist for correcting high amounts of astigmatism?
The options for correcting high astigmatism depend on the specific amount of astigmatism, the reason for the astigmatism, and how it is distributed on your cornea.
Glasses are typically the first method recommended for correcting astigmatism. With regular astigmatism, vision is typically crisp, and clear through glasses lenses. However, if your astigmatism is due to keratoconus, a condition in which the cornea bulges outward, you are unlikely to achieve clear vision through glasses and a doctor will recommend contact lenses. If you do have a high amount of astigmatism, digital, high-index lenses are best for achieving optimal vision.
There are now more contact lens options for patients with high amounts of astigmatism. In the past, soft lenses would move around on the eye causing vision to fluctuate. Previous lenses were old technology, less breathable, had thicker edges, and became dry very quickly.
CooperVision Biofinity XR Toric
Biofinity XR Toric is the best contact lens for high amounts of astigmatism. The lens is available for up to -5.75D of astigmatism. The lens is comfortable and allows oxygen to the eye. Compared to past lenses, the vision is stable and does not fluctuate much with blinking.
Bausch & Lomb Ultra Toric
The Ultra Toric is a great lens for moderate amounts of astigmatism. The lens is available for patients with astigmatism ranging from 0.75 to -2.75D. Like the Biofinity product, it is a silicone hydrogel lens, enabling it to be breathable, and comfortable, resulting in less end-of-day dryness.
Both the Ultra and Biofinity brands are available in multifocal options for patients over 40 who need distance, near, and astigmatism correction. The range of astigmatism powers is a little more limited, but both brands are good options for patients who may not be successful with monovision contact lenses and do not want to wear readers.
Scleral lenses are often the best choice for patients with keratoconus. Scleral lenses are designed specifically for your eyes. They may also be recommended for dry eyes, patients with irregular astigmatism after LASIK surgery, and patients with high amounts of astigmatism.
Scleral lenses bridge over your cornea and sit on the white part of the eye providing the most comfortable, clear vision. The lack of lens movement combined with the clarity of lens material, has made scleral lenses the best option on the market for patients with high amounts of astigmatism.
A refractive surgery, like LASIK, is an approach to correct severe astigmatism. Laser technology may give the surgeon the ability to correct up to -6.00D. Often with a high amount of astigmatism, the surgeon may have to correct part of the astigmatism and an enhancement may be needed. The success of refractive surgery depends upon the regularity of the astigmatism and your specific corneas. If your astigmatism is due to a condition like keratoconus, refractive surgery is not an option.
An intraocular lens exchange surgery can be a great way to correct high amounts of astigmatism. Toric intraocular lenses (IOL) and implantable collamer lenses (ICL) are available for patients over and under 40. Though the lenses are different, the procedure is similar. If you have been diagnosed with cataracts, toric IOLs are a great option. They are available from 1.5D to 6.0D of astigmatism.
Although having a high amount of astigmatism can be frustrating, more options exist for vision correction than ever before. Technology has improved significantly, and eye doctors are able to provide patients with healthier options to achieve crisp vision.