Astigmatism is one of the most common refractive eye conditions, occurring in one form or another in 33% of people living in the US. But have you heard of Stigmatism? What do you know about these two eye conditions? In this article, we discuss stigmatism vs astigmatism, making sure to clear all misconceptions that arise from this discussion. We’ll also discuss symptoms and treatments. Enjoy!
What is stigmatism?
The thing is, there is no such thing as stigmatism. It's actually a misnomer for ASTIGMATISM. In the medical field, stigmatism is not recognized as an eye defect. We will talk about astigmatism shortly, but it's an eye defect resulting from an uneven cornea or eye lens. It also has several symptoms that we’ll discuss in this article. So, if you hear or read about stigmatism anywhere, you should be wary of that content, because it's medically incorrect.
What is astigmatism?
Now, let's talk about astigmatism. Astigmatism is a refractive defect that occurs when either the cornea or the lens of the eye has an irregular shape, leading to difficulty in focusing light evenly onto the retina. Our eyes have lenses that, although flexible, are approximately elliptical, with even curves all around. However, people with astigmatism have either lenses or corneas with uneven curves. This causes the light entering them to focus on more than one point on the retina, and at different angles. As a result, people with astigmatism suffer from blurred or distorted vision. Symptoms of astigmatism may include eyestrain, blurred vision, headaches, and difficulty seeing at night.
What is the cause of astigmatism?
Several factors can cause astigmatism, including injury, genetics, and surgery. As we already discussed astigmatism occurs because of an irregularly shaped cornea or eye lens, and it causes blurred vision, eyestrain, etc. As a hereditary condition, there’s a high probability that if a parent suffers from astigmatism, they can pass it on to their biological children. Injuries and eye trauma can also cause astigmatism if they affect the shape of the cornea. If, for whatever cause, your eyelids exert too much pressure on your cornea, it can also cause astigmatism.
Some complications after eye surgery can also cause astigmatism, as well as a medical condition called Keratoconus. Keratoconus is a condition in which the cornea bulges outward abnormally, forming a cone shape. This change in the cornea shape changes how light is focused as it passes through.
What does astigmatism do to your vision?
Your eyes have several parts, and they all work together for you to see. Light enters your eye through the cornea, moves through the lens (inside your eyes), and is focused on the retina. The cornea is the clear portion of the eye that you can see, while the retina is a layer at the back of the eyes. The retina changes the light into electrical signals sent to your brain through the optic nerve, and your brain interprets those signals into what you see.
However, if you have astigmatism, because one of either the lens or the cornea has an irregular shape, it bends the light entering your eyes more than necessary. As a result, the light isn’t focused on the retina properly, and only parts of the object will be in focus. It’s this uneven focus that causes your sight to look wavy or blurry. Astigmatism isn’t limited by distance and can affect both your near and distant vision.
Types of astigmatism
Astigmatism can be categorized into three different types based on the nature of the refractive errors in the eyes:
- Myopic Astigmatism: The principal meridians of the eye are nearsighted, which suggests a combination of myopia and astigmatism.
- Hyperopic Astigmatism: The principal meridians are farsighted, reflecting a blend of hyperopia and astigmatism.
- Mixed Astigmatism: Both nearsighted and farsighted errors are present in the principal meridians, with astigmatism being the primary refractive issue.
Astigmatism can also be described in terms of its source:
- Corneal Astigmatism: Involves defects in the cornea.
- Lenticular Astigmatism: Relates to defects in the eye's lens.
Finally, Astigmatism can be categorized based on the regularity of the principal meridians:
- Regular Astigmatism: Principal meridians are perpendicular, typically 90 degrees apart.
- Irregular Astigmatism: Principal meridians are not perpendicular, often caused by injuries, corneal scarring, or conditions like keratoconus—a long-term thinning of the cornea. Certain eye surgeries can also result in irregular astigmatism.
What are the common symptoms of astigmatism?
The range of symptoms associated with astigmatism spans from mild to severe, typically corresponding to the degree of irregularity in the eye's curvature. These symptoms include:
- Blurred or distorted vision at different distances, which is a key indicator of astigmatism.
- Difficulty focusing on fine details or small print, which suggests the need for an eye examination.
- Frequent eye strain or discomfort, especially following tasks that require visual concentration, such as reading or using digital devices.
- Headaches, often a result of straining the eyes to achieve clear vision.
- Squinting, a common reflex aimed at improving focus and the clarity of vision.
- Poor night vision.
- Seeing glare or halos around lights.
How to diagnose astigmatism?
The diagnosis of astigmatism requires a comprehensive eye examination, typically conducted by either an optometrist or ophthalmologist. This examination involves several key diagnostic procedures:
- Visual Acuity Test: This assesses the ability of each eye to recognize letters or symbols at a distance, providing insight into the level of vision clarity or impairment.
- Keratometry: This method focuses on measuring the curvature of the front surface of the cornea. It is essential for determining astigmatism's extent and devising corrective lens prescriptions.
- Refraction Test: Conducted to pinpoint the precise lens prescription needed to address any refractive errors, including astigmatism.
- Slit Lamp Exam: In this examination, a specialized microscope with a bright light is used to illuminate the eye. The eye care specialist adjusts the brightness and thickness of the light beam to examine different layers and components of the eye.
When should I have my eyes examined?
Regular eye exams are crucial for promptly identifying vision issues, and astigmatism isn’t exempt. The recommended frequency depends on age:
- Kids: Pediatricians should assess eyes at each well-child visit until school age, then every one to two years.
- Adults under 40: Every five to 10 years.
- Adults 40-54: Every two to four years.
- Adults 55 and older: Every one to three years.
If you wear glasses, contacts, or other visual aids, you may require more frequent check-ups. Also, those with diabetes should also have more frequent eye exams.
How to correct astigmatism?
The treatment for astigmatism centers on correcting the effect of the irregular curvature of the eye, or the curvature itself to improve vision clarity. Common treatments involve:
Eyeglasses or contact lenses are frequently used as the initial form of treatment for astigmatism. These specially designed lenses work to mitigate astigmatism by altering the path of light entering the eye.
Prescription lenses address refractive errors in both the cornea and lens of the eye. The American Academy of Ophthalmology notes that a typical astigmatism is usually correctable to 20/20 vision, although severe cases may not achieve normal vision. Irregular astigmatism, on the other hand, is often challenging to correct to 20/20 vision.
People opt for various contact lenses as an alternative to glasses for correcting astigmatism. They fall into one of three major categories:
- Gas Permeable Lenses: These are rigid lenses with a uniform shape that substitutes for the cornea's refractive effect. They typically offer sharper vision compared to softer toric lenses, but they may be less comfortable initially. However, they provide excellent correction and comfort over time. Some gas-permeable lenses also incorporate toric designs.
- Hybrid Lenses: Hybrid Lenses feature a rigid center for enhanced visual clarity and soft edges for added comfort. They offer a balance between the advantages of both rigid and soft lenses. Hybrid and gas-permeable lenses may require more time and expertise to find a precise fitting. These are factors to consider in your purchasing decisions.
Laser Eye Surgery:
Procedures like LASIK or PRK offer a lasting solution by permanently reshaping the cornea, providing an effective alternative to glasses or contacts for suitable candidates. Operations addressing cataracts and corneal reshaping, such as LASIK, can correct astigmatism. LASIK employs high-precision lasers to enhance corneal symmetry, offering a permanent correction for moderate astigmatism.
A surgeon can also implant a toric intraocular lens (IOL) during cataract removal to correct astigmatism. It's important to note that the cost of a toric IOL may be higher if not covered by health insurance, and candidates must weigh the permanent nature of the surgery.
This non-surgical approach involves wearing rigid contact lenses overnight to temporarily reshape the cornea, providing an alternative to surgery.
What is the difference between astigmatism and nearsightedness and farsightedness?
Astigmatism, nearsightedness (myopia), and farsightedness (hyperopia) are common refractive errors affecting vision. Astigmatism results from an irregular cornea or lens curvature, causing blurred vision at varying distances. Nearsightedness occurs when distant objects appear blurry because of the eyeball being too long. Farsightedness is the opposite, causing close-up objects to be blurry because the eyeball is too short. All three conditions can be corrected with glasses, contact lenses, or refractive surgery.
Is astigmatism hereditary?
Astigmatism often has a hereditary component, meaning it is a condition that can be passed down from biological parents to their children. Excessive pressure from eyelids on the cornea can also contribute to astigmatism.
While genetics plays a significant role in the development of astigmatism, other factors such as trauma, infection, and various eye conditions can also be potential causes.
Can I prevent astigmatism?
The exact cause of astigmatism remains unknown to doctors, and there is currently no known way to prevent it. Astigmatism can be present from birth, but it may also develop during childhood or early adulthood. Some individuals may also develop astigmatism following an eye injury or surgery.
How does astigmatism affect night driving?
Driving at night without correcting astigmatism can be challenging and risky. Astigmatism leads to the scattering of light in the eye instead of focusing it on a single point (the retina). For individuals with astigmatism, street and traffic lights may produce distracting glare, halos, or streaks, adversely affecting their experience and performance during night driving.
While astigmatism is a medical condition that can be corrected once you visit your eye care specialist, stigmatism is just a misnomer. A visit to your ophthalmologist as soon as you notice any changes in your vision can help remedy the situation as soon as possible. That way, you can continue with your daily activities with no inconvenience.
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