The optician says I have astigmatism — is it serious?

The word does a lot of unnecessary frightening. Patients come to me having heard “astigmatism” at the optical shop and wondering whether something is wrong inside their eye. So let me say it plainly: astigmatism is not a disease. It is simply a description of the shape of your eye, and for the great majority of people it is nothing more than a detail in their spectacle prescription.

What astigmatism actually is

Think of the clear front window of the eye, the cornea. In a perfectly regular eye, it is curved like the surface of a football, equally round in every direction, so light focuses to a single clean point.

In an eye with astigmatism, the cornea is curved a little more steeply in one direction than the other, more like the side of a rugby ball. Light entering the eye then focuses at two slightly different points instead of one, and the result is a mild smearing or shadowing of the image, at all distances, not just far away.

That is the whole story. It is a shape, present usually from birth, often running in families, and roughly as common as having a particular nose shape. Most people have at least a small amount. It does not mean the eye is weak, diseased, or wearing out, and ordinary reading, screen use and “eye strain” do not cause it or worsen it.

How it is corrected

Glasses correct astigmatism completely. The lens is ground with a compensating curve, called a cylinder, which is the “cyl” number you see on your prescription. When you first wear a cylinder correction, or when the axis changes, the world can look subtly tilted for a few days. That is your brain adjusting, and it settles.

Contact lenses work well too. Regular soft lenses correct small amounts, and toric contact lenses, which are shaped to sit in a fixed orientation on the eye, correct larger amounts. Our contact lens clinic fits these routinely. Astigmatism is also correctable with laser surgery in suitable eyes; if you are curious about that route, the LASIK page explains who is a good candidate.

Why astigmatism matters at cataract surgery

Here is the part many people only discover in their sixties. When we remove a cataract, we replace the cloudy natural lens with an artificial lens, an IOL. A standard IOL corrects the main power of the eye but not the astigmatism, so a person with significant corneal astigmatism would still need glasses for clear distance vision afterwards.

For those eyes we use a toric IOL, a lens with the astigmatism correction built into it, aligned precisely inside the eye during cataract surgery. Done well, it means the astigmatism you have carried all your life is corrected in the same ten-minute operation that removes the cataract. This is one of the genuine quiet advances of modern cataract surgery, and it is why we measure the cornea so carefully before choosing a lens. I have set out the choices in detail on our lens options page.

So if you have astigmatism and a cataract is developing, do mention the astigmatism when we plan your surgery. It changes the lens we choose, and it is measured, not guessed.

When astigmatism deserves closer attention

There is one situation where I do want to see a patient promptly. Ordinary astigmatism is stable, the number stays roughly the same for decades. If astigmatism is increasing steadily, especially in a teenager or young adult, or if the axis keeps shifting and no pair of glasses ever seems quite right, we examine the cornea more closely.

Occasionally that pattern points to keratoconus, a condition in which the cornea gradually thins and steepens into a cone shape. It is uncommon, it is not caused by the astigmatism itself, and caught early it can be stabilised. The test is a painless corneal map called topography, done in a few minutes. Frequent eye rubbing, strong allergies and a family history are the things that raise my suspicion.

That is the honest scope of concern: not astigmatism itself, but astigmatism that keeps changing.

The short answer

A stable cylinder number on your prescription is a shape to be corrected, not a condition to be feared. Wear the correction, enjoy the sharpness, and let us re-check it at your routine examination. And if your number has been climbing year after year, come in and let me look at the cornea properly.

If you have astigmatism and a cataract is on the horizon, see our lens options or message us on WhatsApp. I measure every eye myself before we choose the lens together.