Eye exams for contact lenses

Different to a standard eye exam, an eye exam for contact lenses is an additional step that you must take if you want to wear contacts.

Whereas a comprehensive eye exam includes a test of your visual acuity (using an eye chart), determines your prescription strengths, and checks for a number of eye conditions including glaucoma, your contact lens eye exam includes more specialised testing designed to judge which lenses you need and how your eyes will interact with them.

Are eye exams for contact lenses the same as eye exams for glasses?

No. An eye exam for a contact lens wearer, or someone who wants to wear contacts, is also different compared to an eye exam for glasses.

You’ll need to undergo a contact lens fitting to determine the ideal lenses for you and whether there are any conditions or issues you need to be aware of while wearing contacts.

What to expect during a contact lens fitting

Firstly, you’ll be asked a few questions about your lifestyle and preferences for contact lenses, so your optician will be able to find the most suitable type of contacts for you.

After this, the optician will then need to take the measurements of your cornea, pupil and iris, as well as evaluating your tear film and the surface of your eye.

Cornea

Using a keratometer, your optician is able to analyse how light reflects off your cornea, therefore measuring the curvature of your eye and identifying the base curve and diameter of lens that you’ll need.

In some instances, to gain more specific details about the surface of your eye, a corneal topographer will be used. This is either done by beaming circular patterns of light into your eyes, generating a digital surface map of your eyes, or by wavefront measurements designed to analyse how your eye focuses on light.

Pupil and iris

This one’s a bit simpler, with your optician only needing to use a ruler or card to measure the size of your pupil.

In some cases, an automated machine will be used for a more precise reading, and can also be used to measure the size of your iris.

Tear film

This is done to assess the stability of your tear film and to discover if you’re susceptible to dry eyes. A small strip of paper is placed underneath your eyelid, and is left there for five minutes while you close your eyes.

After this time, your optician will inspect how much of the paper has been moistened and will be able to tell you if regular occurrences of dry eyes are something you need to worry about. This way they’ll be able to prescribe you lenses that have been designed for those with sensitive eyes, or find out if your eyes aren’t suitable for contact lens wear in general. Another common test is called the ‘tear break up time’, which involves tracking the time it takes for the tears to break its smoothness before blinking.

The contact lens fitting

You’ll need to demonstrate to your optician that you’re able to put your contacts in and take them out properly. They’ll talk you through the whole process, while you can also read up on our guide on how to safely apply and remove your lenses.

After you’re successful and you’re wearing your contact lenses, you’ll need to wear them in front of the optician for a few minutes or so, until they sit comfortably in place and any initial tearing has disappeared.

A biomicroscope (slit lamp) will also be used to evaluate how the lens sits on your eye and observe its movement as your eyes move. This can also be used in follow-up eye exams to identify any impact the contact lenses may have had on your eyes.

After you have your prescription

Once you’ve found lenses that fit comfortably and ensure clear vision, your optician will write your contact lens prescription. This contains your required base curve, diameter and power, as well as any cylinder, axis, additional power or other important information.

It’s worth remembering that it is your legal right in the UK to own a copy of your own prescription and you are not obliged to buy your contact lenses from your optician. You can buy your contact lenses from any licensed high street retailer or online contact lens retailer.

To find out more about your contact lens prescription, what the individual figures mean, and which lenses you’ll need, take a look at our helpful prescription guide.

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