Astigmatism is a common vision condition that affects how clearly you see at all distances. Many people have some degree of astigmatism, which can cause vision to appear blurred or distorted. The good news is that it can be easily diagnosed and effectively managed through glasses, contact lenses, or corrective procedures such as laser vision correction.

What is Astigmatism?

Astigmatism occurs when the front surface of the eye (the cornea) or the internal lens has an irregular curve. Instead of being evenly rounded like a basketball, it is shaped more like a rugby ball. This irregular shape prevents light from focusing evenly on the retina, the light-sensitive tissue at the back of the eye, leading to blurred or distorted vision.

What Causes Astigmatism?

Astigmatism is usually caused by natural variations in the shape of the eye, but it can also develop after eye injury, surgery, or certain conditions.

Common causes include:

• Inherited corneal shape: many people are born with a naturally oval-shaped cornea.
• Eye injury or surgery: changes in the cornea after trauma or a procedure can cause irregular curvature.
• Keratoconus: a progressive condition where the cornea becomes thinner and cone-shaped, increasing astigmatism.
• Lens changes with age: sometimes the internal lens develops uneven curvature over time.

Symptoms of Astigmatism

Astigmatism symptoms can vary depending on its severity. Common signs include:

• Blurred or distorted vision: objects at any distance may appear stretched or shadowed.
• Eye strain or discomfort: squinting to focus can cause tired or sore eyes.
• Headaches: often linked to eye strain or prolonged effort to see clearly.
• Difficulty seeing at night: lights may appear streaked or have glare.
• Frequent changes in prescription: vision clarity can fluctuate over time.

How Astigmatism Affects Your Vision

When light entering the eye doesn’t focus evenly on the retina, it creates multiple focal points instead of one. This can make straight lines appear slightly tilted or wavy, and fine details harder to distinguish. People with uncorrected astigmatism often describe their vision as slightly “off-centre” or shadowed around objects.

Types of Astigmatism

Astigmatism can occur in different parts of the eye and in different orientations.

Main types include:

• Corneal astigmatism: caused by an irregular curvature of the cornea.
• Lenticular astigmatism: caused by uneven curvature of the eye’s internal lens.

By orientation:

• With-the-rule astigmatism: the cornea is steeper vertically.
• Against-the-rule astigmatism: the cornea is steeper horizontally.
• Oblique astigmatism: the steepest curve lies at an angle between vertical and horizontal.

Diagnosing Astigmatism

Astigmatism is detected during a comprehensive eye examination.

Diagnostic tests may include:

• Refraction test: measures how light bends as it enters your eye.
• Keratometry: assesses the curvature of the cornea.
• Corneal topography: maps the corneal surface to detect irregularities.
• Autorefraction: uses computerised instruments to calculate prescription strength.

These tests help your ophthalmologist determine the degree and type of astigmatism and guide the best correction approach.

Treatment Options for Astigmatism

Treatment depends on the severity of the astigmatism and your individual vision needs.

Common options include:

• Glasses: simple and effective for mild to moderate astigmatism.
• Contact lenses: toric lenses are designed to correct the uneven curvature of the eye.
• Laser vision correction (LASIK, PRK, or SMILE®): reshapes the cornea to allow light to focus more precisely.
• Refractive lens exchange (RLE): replaces the natural lens with an artificial one in certain cases.

Each option has benefits and considerations. Glasses are non-invasive and easy to update, while laser vision correction offers a longer-term reduction in dependence on glasses or contact lenses. Suitability is assessed individually during a detailed consultation.

Prevention and When to See an Eye Specialist

Astigmatism cannot always be prevented, as it often develops naturally, but maintaining regular eye checks helps ensure early detection and management. If you notice blurred vision, headaches, or eyestrain, it’s worth booking an eye examination.

Seeing an ophthalmologist or optometrist can help confirm whether astigmatism is affecting your vision and the appropriate steps to correct it.