Laser eye surgery can correct many forms of astigmatism by changing the shape of the cornea so light focuses more evenly. However, suitability is not determined by the glasses prescription alone. It depends on the type, amount and stability of the astigmatism, corneal shape and thickness, eye health, age and visual needs. LASIK, PRK and lenticule-based procedures may all be considered, depending on assessment.

What is astigmatism?

Astigmatism is a focusing error commonly caused by the cornea being less spherical than normal. Rather than curving evenly like half a basketball, it is steeper in one direction than the other, more like the curve of a football. This causes light to focus at more than one point, which can make vision appear blurred or distorted at both distance and near. It can occur on its own or in combination with short-sightedness or long-sightedness.

Most regular corneal astigmatism can be measured consistently and may fall within the treatment range of modern laser systems. Irregular astigmatism is less predictable and may be associated with corneal disease, previous surgery or injury. Depending on the underlying cause and corneal measurements, patients with irregular astigmatism may make laser vision correction unsuitable.

How do the laser procedures compare?

LASIK reshapes the cornea beneath a thin flap. PRK reshapes the surface after the outer layer is removed and allowed to regrow. Lenticule-based procedures reshape the cornea by removing a small piece of tissue through a small opening.

Each approach can treat selected combinations of short-sightedness and astigmatism. Treatment ranges, recovery patterns and suitability criteria differ. No single procedure is appropriate for every eye, and glasses or toric contact lenses remain non-surgical alternatives. Lens-based correction may also be considered in selected circumstances.

What determines suitability?

A glasses prescription tells us how much correction is required, but it does not show whether the cornea can be safely and predictably reshaped. A refractive assessment therefore looks beyond the prescription and considers:

• whether the prescription has remained stable
• whether the astigmatism is regular or irregular
• the thickness, shape and structural integrity of the cornea
• the quality of the tear film and the health of the eye’s surface
• age-related changes in reading vision
• the patient’s visual requirements and expectations.

Corneal mapping provides a detailed picture of the cornea’s curvature and symmetry. This is particularly important because two people can have the same glasses prescription but very different corneal measurements and therefore may not have the same treatment options.

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Limitations and risks

Laser vision correction aims to reduce dependence on glasses or contact lenses; it does not guarantee complete freedom from them. A small amount of astigmatism may remain, and under-correction, over-correction or later changes in prescription can occur.

Laser treatment changes the shape of the cornea, but it does not stop the natural ageing of the eye. Reading glasses may therefore still be required as near focus changes with age.

Possible effects include temporary discomfort, dry-eye symptoms, glare, halos and fluctuations in vision. Less common complications can include infection, inflammation, weakening of the cornea or the need for further treatment. The likelihood and significance of these risks depend on the condition of the eye and the procedure being considered.

What to consider

Laser eye surgery can correct many forms of astigmatism, but not every type of astigmatism or every cornea is suitable for laser treatment. The appropriate option depends on more than the number written on a glasses prescription.

Dr Peter Sumich has expertise in refractive eye surgery, including laser vision correction, at Hunter Street Eye Specialists in Parramatta. A comprehensive refractive assessment can determine whether laser vision correction, lens-based treatment or a non-surgical option may be appropriate.

Learn more here , or contact us at online or via phone at 02 9635 0663.

This article provides general information only and is not a substitute for personalised medical advice. Read our full disclaimer here