What is Astigmatism? A complete guide

Astigmatism is a common vision condition caused by an uneven curve of the eye. Instead of being evenly shaped, the eye is more like a rugby ball. This causes light to focus incorrectly on the retina, leading to blurred or distorted vision.

Blurred or distorted vision, eye strain and fatigue (especially after reading or screen use), and headaches are all common symptoms.

Many people with mild astigmatism have no noticeable symptoms and often only detected during a routine eye test. Difficulty driving at night can be an early sign, particularly if headlights appear with star-like streaks.

Astigmatism is usually present from birth. Caused by a slight irregularity in the natural shape of the cornea or lens. The exact cause isn’t fully understood, but genetics play a significant role. Studies suggest it is 50 to 65% heritable, meaning it often runs in families.

It can also develop or change due to eye injury, conditions such as keratoconus, or certain types of eye surgery. For most people, it is simply a natural variation in eye shape rather than the result of lifestyle factors.

CYL (cylinder) is the field on your prescription that indicates the power of the astigmatism correction needed. If you have a CYL value, you have astigmatism. The number can be positive or negative. It indicates the lens power needed in a specific direction to correct the irregular curvature of your eye.

AXIS is always present alongside a CYL value and indicates the orientation of the astigmatism. It is measured in degrees from 1 to 180. The AXIS tells our lab technicians in which direction to position the cylindrical correction within the lens.

If your prescription has no CYL value (or shows 0.00), you do not have a measurable astigmatism correction. If you are unsure how to read your prescription visit our guide.

Yes. Prescription glasses are the most common and effective way to correct astigmatism. The lenses include cylinder and axis values that adjust for the eye’s uneven shape. Astigmatism can be corrected with single vision, bifocal or varifocal lenses.

Yes, in fact, this is very common. Many people have both short-sightedness (myopia) or long-sightedness (hyperopia) and astigmatism simultaneously.

When this is the case, the prescription addresses both conditions in the same lens. The SPH (sphere) value corrects the short or long-sightedness, while the CYL and AXIS values correct the astigmatism. A single pair of prescription glasses handles both corrections without any additional complexity during ordering.

Yes. You can buy glasses for astigmatism online in the UK at Direct Sight. The process is identical to ordering standard prescription glasses. Simply include your CYL and AXIS values when entering your prescription at checkout.

You will need a current prescription from a UK optometrist (dated within the last two years) that includes your SPH, CYL, AXIS, and PD values. Our optical team checks all prescriptions before glazing, and your glasses are produced at our UK laboratory in Amersham.

No, at Direct Sight, astigmatism glasses cost the same as standard prescription glasses. There is no additional charge for the astigmatism correction (CYL and AXIS values).

Our prescription glasses including astigmatism corrections start from £9.00 including single vision lenses, made at our UK facility.

Higher CYL values can contribute to lens thickness in a similar way to stronger spherical prescriptions. Optional upgrades for higher index 1.6 and 1.67 lenses are available to keep the lenses slimmer and lighter.

Astigmatism is diagnosed during a routine eye test by an optometrist. They assess how your eye focuses light and measure the curvature of your cornea.

Tests may include autorefraction (a machine estimate), manual refraction (checking vision through different lenses), and sometimes corneal topography (maps the eye’s surface). Many people with mild astigmatism are unaware they have it until a routine check.

The NHS recommends eye tests every two years for adults. More often if you have diabetes, glaucoma, or a family history of eye conditions.

For most people, astigmatism remains relatively stable after early adulthood. It may change slightly as part of the natural ageing process.

Significant or rapid changes in astigmatism can occasionally indicate an underlying condition such as keratoconus (progressive thinning of the cornea). This is why regular eye examinations are important. If you notice your vision changing noticeably between appointments, it is worth booking an earlier check with your optometrist.

Short-sightedness (myopia) means the eye focuses light in front of the retina rather than on it. This produces blurred vision for distant objects but clear vision close up. It is corrected with a spherical lens (a minus SPH value on the prescription).

Astigmatism means the cornea or lens is irregularly curved. This causes light to focus at multiple points rather than one, producing blurred or distorted vision at all distances. Corrected with a cylindrical lens (a CYL and AXIS value on the prescription).

The two conditions are independent but very commonly occur together. A single prescription lens can correct both simultaneously.