Astigmatism

Astigmatism occurs when the curve of the cornea is asymmetric so that it looks more like a rugby ball than a football. This produces multiple points of light focus and results in a blurred image.

In most cases, astigmatism is a natural variation. On some occasions astigmatism may be a sign of changes in the cornea that may require further tests.

To diagnose and examine astigmatism, we will perform the following tests:

• Refraction test
• Ocular examination
• A dilated fundus examination to check the health of the eye and retina
• A special scan that precisely measures the amount of corneal astigmatism

To correct astigmatism, patients must wear glasses or contact lenses.

However, to achieve the best visual outcomes without glasses or contact lenses, astigmatism can also be corrected at the time of cataract surgery or with refractive lens exchange with a choice of toric lens implants.

The most appropriate treatment option for you will depend on several factors, such as your:

• Spectacle prescription
• Age
• Job
• Hobbies
• Any existing eye conditions or issues
• The findings from your clinical examination
• The results of any further tests or corneal scans

Can I still have a lens replacement operation if I have astigmatism?

Yes, it is possible to correct astigmatism with a toric lens implant. This can be done with either a monofocal or multifocal lens implant.

Can cataract surgery make my astigmatism worse?

It is possible for astigmatism to increase after a cataract operation. This could result in blurred vision unless you wear glasses.

To minimise this risk, the cataract operation may be planned so that any induced change in astigmatism is kept to a minimum.

Furthermore, if the change in astigmatism is likely to be significant, then a toric lens implant may be recommended in order to optimise the visual outcome.

The tests that are performed before surgery will help your surgeon make the most appropriate recommendation.

I’ve already had a cataract operation but still have astigmatism and need to use my glasses all the time. Can this be treated?

Yes, it is possible to treat residual astigmatism.

The options include laser vision correction or a toric piggyback lens implant.

Depending on your individual circumstances, it may be possible to use a multifocal toric piggyback lens implant to treat astigmatism and provide improved reading vision without glasses.

Astigmatism: A tale of Two Patients

Patient 1 received cataract surgery with another surgeon at a different clinic. They had 2.5 dioptres of astigmatism before cataract surgery, but left with 4 dioptres after cataract surgery.

This left the patient with poor vision unless they wore glasses with a strong astigmatic prescription at all times.

The patient came to Prof Muhtaseb for help. He informed the patient of the benefits and risks of the various surgical means that could help to correct the residual astigmatism.

Patient 2 consulted Prof Muhtaseb about cataracts. She had 1 dioptre of astigmatism in her glasses. Prof Muhtaseb calculated the likely outcome with and without a toric lens implant using the latest technology for measuring the eye and calculating the best lens implant.

Taking into account the amount and direction of the astigmatism from the corneal measurements, and the effect of surgery on the corneal shape, Prof Muhtaseb recommended a toric lens implant with 2.75 dioptres of toric astigmatic correction. The patients post-operative result was excellent with zero astigmatism in each eye and sharply focused distance vision.

These cases illustrate the importance of accounting for the magnitude and direction of astigmatism before surgery – measuring the eye with very accurate devices, understanding the effect of surgery on the eye, using the most accurate formulae to model the post-operative outcome, and tailoring the lens implant choice to each individual eye. Every eye is different, and each patient should expect a tailored surgical plan for each eye.

This is Prof Muhtaseb’s standard of care.