An eye test explained

Optician and customer looking through a tonometer

A routine eye test can be very useful to check your sight, any changes in your vision, and detect underlying health problems or conditions. It normally involves a general check-up and conversation about your vision, followed by a series of tests, with a trained professional optician. Although, each examination will differ depending on individual needs and eye health, and usually takes no longer than 20 minutes.

If you do want to make the switch from glasses to contact lenses, you'll need to book a contact lens fitting. After this fitting, you'll be given a prescription, which differs from your glasses prescription, and you can make your first contact lens order online from us.

It's important to always remember that in an eye exam, there's no right or wrong answer. You need to say exactly what you're seeing. So, don't feel bad if you can't read the letters on the board. Honesty is key to help your optician ensure that they're providing you with the best possible solutions to help aid your vision.

What happens during an eye test?

The first stage normally involves a pre-test, which can be carried out by the optical assistant or your optician. They'll begin by asking you a series of questions to know more about your lifestyle and the history of your eyes - if you've been having any problems with your eyes at all or if you've had issues with your general health recently.

Some of the questions they might ask you are:

  • Do you take any medication?
  • Do you already have a prescription? And if so, do you already wear glasses?
  • Do you have any eye problems or genetic health history, such as glaucoma?
  • Do you have any issues or concerns with your current vision?

You'll then be asked to read from an eye chart with a number of letters on it. This may be the classic type or a projected version. The optometrist will often cover one eye at a time to root out any discrepancies between the left eye and the right eye.

Once this assessment is carried out, there are a few tests, with the following tools that your optician will use:

The tonometer

The non-contact tonometer is used to test the pressure inside of each eye. This tool sends several small puffs of air against each eye, which slightly flattens the front part of the eye (the cornea). The length of time it takes to flatten the cornea is then converted into an accurate measurement of the pressure inside the eye. While this might feel a little funny, it's an important test. High pressure can be an indicator of the early stages of glaucoma, which could be sight-threatening.

Optician using an ophthalmoscope on a customer

The autorefractor

An autorefractor, which looks like an old computer, is used to find out how well your eyes focus and can be very useful in determining an approximation of your prescriptions. You'll simply be asked to focus on an image or point of light. The optometrist will then ensure your eye is in full view of the machine and take a quick measurement.

The ophthalmoscope

An ophthalmoscope is a handheld tool that the optometrist will use to clearly see inside your eye. A light will be shone into your eye, allowing the optometrist to see into your pupil to the back of your eye known as the fundus. You may be asked to put in eye drops before this test in order to widen your pupils, but this is pretty uncommon.

The slit lamp

This tool is particularly important for contact lens wearers. A powerful illuminated microscope is used to examine the outer surface of your eyes, allowing the optometrist to check how well your contact lenses are fitting or for any abnormalities or scratches to your cornea.

Optician reading off a snellen chart with a customer

Why should I book an eye test?

No matter how old you are or how healthy you feel, it's always important to receive regular eye examinations from a qualified eye care professional. Like we've said, a sight test is certainly a good way to find out if your vision could be improved, but a thorough eye examination will also serve as a health check for any eye conditions. In fact, opticians can spot certain illnesses not directly related to the eyes, or help detect serious problems, which usually develop over time.

How often should I get my eyes tested?

This can vary from person to person, but most optometrists recommend taking a thorough eye test with your optician every 2 years. However, patients who are over 60, should get their eyes tested more frequently (every 12 months or so), as they're more at risk, and a test can catch any health problems. It's also best for younger children, under 16, to get their eyes tested annually, as a child's vision changes rapidly during the early stages of their lives.

How much is an eye test?

Prices can vary with eye tests and some high street opticians offer free examinations or discounted ones, funded by the NHS if you're 60 or over, or in full-time education. But before you book your appointment online, make sure to check if you qualify for a voucher and that your eye test will be free, with no extra charges. Whether you're getting a Specsavers eye test or a Boots eye test, you can check if you're entitled to a free NHS eye test on the NHS website, or give your optician a ring to find out more.

Our exclusive eye health package with David Clulow

Customer looking through a tonometer

As the vision and eye health of our customers is paramount, we've teamed up with the top-notch optician, David Clulow, to offer you a premium in-person eye test and contact lens check-up (worth £50) for just £25. That's half price and what most opticians charge for a standard eye test! Each service takes 25 minutes (50 minutes in total), ensuring a thorough check without wasting your time or money.

Plus, you can enjoy access to aftercare, expert advice and David Clulow's fantastic range of designer reading glasses and sunglasses by brands like Ray-Ban and Prada. Just put in your postcode to see where your nearest store is.

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What problems can be detected in an eye test?

Your optician's assessment will involve looking for signs and symptoms of eye diseases or other medical conditions, including:

  • Difficulties focusing: Children may not be able to focus properly due to developmental issues while adults may experience a decline in their focus as a result of their advancing age.
  • Refractive errors: Astigmatism, hyperopia (long-sightedness) and myopia (short-sightedness) are some common refractive errors that can be detected during a test. These conditions are easily corrected with eyeglasses or contact lenses. In severe cases, surgery using the latest technology may be an option.
  • Strabismus: Sometimes described as 'crossed' or 'turned' eyes, strabismus is detected by assessing whether the eyes are aligned correctly. Patients with this condition may be unable to judge the depth of the visual field correctly.
  • Amblyopia: Often a result of strabismus (a condition in which the eyes don't properly align with each other when looking at an object), amblyopia (a lazy eye) can cause permanent impairment in vision. In patients with this condition, the brain will effectively 'close down' the image from the affected or weaker eye. A common solution is to place a patch over the stronger or correctly aligned eye for periods of time.
  • Eye teaming problems: Effective vision relies on the two eyes working jointly and in cases where this does not happen the patient may suffer headaches, difficulty reading or eye strain.
  • Diseases of the eye: Many common diseases of the eye are asymptomatic in the early stages but can be identified during a regular eye examination. Earlier detection increases the likelihood of treating the diseases and reducing the probability of irreversible loss of vision. Examples of the diseases an optician will assess you for include glaucoma and diabetes.

What treatment will I receive?

After an examination, your optometrist will advise you on the next steps. This can include a prescription for glasses or contact lenses for any vision problems that can be easily corrected. You may also be advised to try some vision therapy, sometimes known as vision training, which will help to build your eye coordination and control. Very occasionally you might be asked to see your GP or an eye specialist if there is some further investigation or treatment required. If no problems are found with your eyesight, then you may find the only requirement is to return in another couple of years for a regular check-up.

What about online eye tests?

Extremely convenient, online eye tests are an easy and quick way to carry out a basic evaluation of your eyesight from home. Just by accessing a test on your computer or phone, you can examine your visual acuity, refractive errors, and even use the results to renew an expired spectacle prescription or contact lens prescription. However, an online eye test is only a preliminary assessment, and it can't check the health of your eyes unlike an in-person examination with a trained professional optician.

Need more help or advice?

For personalised advice on anything to do with contact lenses and eye health use our live chat, call our friendly customer support team on 020 7768 5000 in the UK or on 1 800 870 0741 in the US or email They're available Monday - Friday 8:00 - 21:00, and Saturday - Sunday 8:00 - 18:00.