Many people have heard of astigmatism but aren’t quite sure what it means and what causes it. Astigmatism is a very common disorder that can be easily corrected. The main symptom of astigmatism is usually blurry vision. In this article, we will talk about the two types of astigmatism and its causes, along with available treatment options. We will also answer the question of whether or not diabetes can cause astigmatism.
Brinton Vision is the premier vision correction center in the St. Louis area. To learn more about the treatments we offer for astigmatism, visit our website to take the Self-Test or call now to schedule your Brinton Vision Ocular Analysis.
What is astigmatism?
Blurred vision is the primary sign of astigmatism, and most people have some degree of astigmatism, even if they don’t notice it. An individual with astigmatism has an irregularly curved cornea, which often has one half that is flatter than the other and occasionally one that is steeper than it should be.
Images become distorted when light rays enter the eye because they do not concentrate properly on the retina. Astigmatism, which develops in the eye’s posterior segment behind the cornea, can be brought on by a lens that is irregularly shaped.
Both children and adults can have astigmatism, which is pretty common and not contagious. It is typically congenital—present at birth—but it can sometimes arise following an operation on the eye or an eye injury. Astigmatism is a member of a class of vision issues known as refractive errors. Refractive errors include myopia (near-sightedness), hypermetropia (far-sightedness), and presbyopia (aging of the eye’s lens).
A refractive error occurs when the eye’s shape does not correctly bend light, which causes a blurry image and diminished visual perception. To see clearly, light must be correctly bent (refracted) by the lens and the cornea before it reaches the retina.
According to a study conducted by researchers at the National Eye Institute, approximately half of all Americans aged 20 and older have refractive errors.
What are the two main types of astigmatism?
The two most common types of astigmatism are corneal astigmatism and lenticular astigmatism. In corneal astigmatism, the cornea has an irregular shape and is not spherical or has an uneven form, such as an egg or rugby ball. This is the most common cause of astigmatism, which impairs vision in close-up and distance situations. Although surgical treatments are available for those who want to stop wearing glasses or contacts, this form of astigmatism is often treated with corrective lenses.
Lenticular astigmatism refers to the distortion of the eye’s natural lens. Most of the time, when the lenticular lens is distorted, the cornea still has a normal shape. Although lenticular astigmatism is less frequent than regular corneal astigmatism, both can result in blurry or distorted vision. Treatment for this kind of astigmatism frequently requires surgery.
What causes astigmatism?
Corneal astigmatism
The tissue covering the front of the eye is called the cornea, and it is transparent and clear. In addition to focussing and transferring light into the eye, it shields the eye from injury and infection. To properly bend (refract) light as it enters the eye, the cornea must be perfectly curved.
The retina senses light at the rear of the eye and receives an imperfect image if the cornea is not exactly round, meaning that one half is flatter or steeper than the other. This is because the light that strikes the cornea will not refract properly. Astigmatism in that eye will cause blurred or distorted vision for the person.
Instead of a perfect sphere shape, people with astigmatism typically have an oblong-shaped (oval-shaped) cornea. The light rays will focus on two locations in the retina instead of simply one if the cornea is curved like an oblong.
Scientists don’t know why some people are born with improperly curved corneas. According to some studies, if one or both parents have astigmatism, the likelihood of the infant developing it is increased.
In comparison to other babies, premature babies and newborns with low body weight are more likely to develop astigmatism. Astigmatism may result from specific surgeries or eye injuries that leave the cornea scarred. Astigmatism can also be brought on by keratoconus, a degenerative condition of the eye in which the cornea gradually thins and assumes a more conical shape.
Lenticular astigmatism
Though similar to corneal astigmatism, in lenticular astigmatism, the issue exists in the lens instead of the cornea. Images are imperfectly transmitted to the retina because the lens’s curvature varies rather than being perfectly round. The cornea of most people with lenticular astigmatism is regularly shaped; the only imperfection is in the lens’s curvature.
Because high blood sugar levels can cause the lens to change shape, lenticular astigmatism is a common complication in people with diabetes. The condition often progresses slowly and is typically identified during the beginning phase of diabetic treatment. When diabetes is treated, and blood glucose levels return to more normal ranges, the curvature of the lens will likewise return to normal; many people will experience this as an increase in their hypermetropia (long-sightedness). Patients should wait at least a month after starting their diabetes treatment for the lens to stabilize before getting their eyes assessed for glasses.
What are the symptoms of astigmatism?
The main signs and symptoms of astigmatism include:
- Vision that is blurry or distorted at all distances.
- Photophobia (sensitivity to light)
- Headaches
- Excessive squinting
- The need to constantly close the eyes
- Eye strain – more common when the eye is forced to focus for extended periods of time, such as while reading from a book or a computer screen
How do ophthalmologists diagnose astigmatism?
An ophthalmologist or optometrist may use the following tools and eye tests to examine the eyes in order to diagnose astigmatism:
Visual acuity test – requires reading letters on a chart where on each line, the letters get progressively smaller
Astigmatic dial – This diagram displays a collection of lines that together form a semicircle. The lines will be visible to people with excellent vision, while those with astigmatism will notice some lines more clearly than others.
Keratometer – also referred to as an Ophthalmometer. The light that is reflected from the cornea’s surface is measured using this instrument. It can determine the degree of aberrant corneal curvature and quantifies the radius of corneal curvature.
Keratoscope – commonly referred to as Placido’s disk is a tool used to study corneal reflex. It is marked with lines or circles and projects rings onto the cornea using light. It determines the differences in curvature by measuring the distance between the rings, which then determines the degree of astigmatism. A keratoscope with a video attachment is known as a videokeratoscope.
Regular eye exams to monitor eye health and check for refractive errors such as astigmatism are important. Doctors advise having a thorough eye exam for children at age four and then yearly until they are 16 years old. Adults should get their eyes checked every two to three years.
What are the treatments available for astigmatism?
Like with other refractive errors, astigmatism is often corrected by either refractive surgery or corrective lenses (some treatments can require a combination of both).
Treatment for astigmatism with corrective lenses: Prescription eyeglasses and contact lenses are the simplest way to correct a refractive error like astigmatism. Soft Toric lenses are frequently chosen when it comes to contact lenses. However, gas-permeable contact lenses might also be a viable choice given the astigmatism-related irregular shape of the cornea. They are stiff lenses that keep their shape inside the eye, forcing the cornea to alter its shape to one that is uniform across all angles.
Refractive surgeries like LASIK and PRK can be used to treat astigmatism by adjusting the cornea’s asymmetrical shape. These treatments are safe, effective, and minimally invasive, and they frequently come with the extra advantage of correcting eyesight without the need for eyeglasses or contact lenses. It’s important to remember that while LASIK can fix corneal astigmatism, it cannot treat lenticular astigmatism. Lenticular astigmatism can be treated with Custom Lens Replacement which is also known as refractive lens exchange (RLE). It is similar to cataract surgery, where the native lens of the eye is removed and replaced with an intraocular lens (IOL). This procedure also has the added benefit in that the new IOL cannot develop cataracts.
Corneal cross-linking is the suggested course of treatment for astigmatism caused by keratoconus or corneal ectasia.
Another technique for treating astigmatism functions somewhat like a cross between corrective lenses and refractive surgery. To gradually reshape the cornea and enhance vision, orthokeratology includes wearing a series of stiff contact lenses at night. But unlike refractive eye surgery, the reshaping is temporary; thus, if the patient quits using the lenses, the cornea could gradually revert to its irregular shape.
What is diabetic eye disease?
People with diabetes may experience various eye issues known as diabetic eye disease. These conditions include glaucoma, cataracts, diabetic macular edema, diabetic retinopathy, and proliferative diabetic retinopathy.
Diabetes can damage your eyes over time, resulting in blurry vision or even blindness. However, by managing your diabetes, you can take steps to prevent diabetic eye disease from occurring or to stop it from getting worse.
The best approaches to control your diabetes and maintain the health of your eyes are to:
- Control blood sugar, blood pressure, and cholesterol
- Stop smoking
- Yearly dilated eye examinations
Although your eyes may appear to be in good health, the only way to be sure is to get a thorough, dilated eye exam.
When damage first occurs, there are frequently no early indicators of diabetic eye diseases or vision loss. For example, diabetes doubles your risk for glaucoma, which can damage your optic nerve and can lead to vision loss and blindness if not treated early. Your eye doctor can diagnose and treat eye problems such as these early—often before significant vision loss might occur—with the help of a complete eye exam.
In summary, diabetes can cause lenticular astigmatism, which can lead to visual impairment. Routine eye exams and diabetes management are important to help minimize any vision problems associated with lenticular astigmatism. Brinton Vision offers custom lens replacement, which may be a good treatment option for lenticular astigmatism. To learn more about the vision correction procedures we offer, or to schedule your Brinton Vision Ocular Analysis, call our office now or visit our website to learn more. We want everyone to live a life free from the worry of vision problems, and we are here to help you achieve the visual freedom you desire.
Read the next article in this series: 5 Things You Need to Know About Having Astigmatism