Astigmatism – Symptoms and Causes
What Causes Eye Focus Problems
Astigmatism is a common vision condition. It causes blurry or distorted vision at all distances. Astigmatism occurs when the cornea or lens has an irregular shape.
This irregular shape prevents light from focusing properly on the retina. As a result, you may experience symptoms like eye strain, headaches, or difficulty seeing at night.
Astigmatism can also occur due to an injury to the eye. Some forms of eye surgery can also lead to astigmatism. Additionally, a family history of the condition may increase your risk of developing it.
How Refraction Errors Occur
Refraction errors happen when the eye cannot properly focus light. The eye has two main parts that bend light to create clear images:
- Cornea: The clear front surface of the eye and the tear film.
- Lens: A clear structure inside the eye that changes shape to focus on close objects.
In a normal eye, both the cornea and lens have smooth, round curves that bend incoming light equally. This creates a sharp, focused image on the retina at the back of the eye.
A refraction error occurs when either the cornea or lens has an uneven curve. One of these structures becomes more egg-shaped, instead of being perfectly round like a ball. This means the surface curves more steeply in one direction than another.
When light passes through an uneven surface, it bends differently in different directions. This creates two separate images that overlap, resulting in blurry vision. The blurriness might be more noticeable horizontally, vertically, or at an angle.
People can be born with refractive errors, or they may develop them after eye injuries, diseases, or surgeries. Despite common myths, these problems aren’t caused or made worse by reading in dim light, sitting too close to screens, or squinting.
There are two main types:
- Corneal refractive errors – when the cornea has mismatched curves.
- Lenticular refraction errors – when the lens has mismatched curves.
Both varieties result in comparable vision issues. These typically require correction with glasses, contact lenses, or sometimes surgery.
