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Prescriptions & Eye Tests
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 several 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.
A prescription for wearing glasses cannot be used to purchase contact lenses as additional tests and measurements are needed to find the right lenses for you.
How much does it cost for contact lens exam?
The cost for a contact lens exam varies, depending on certain conditions and where you go to get the exam.
The NHS provides free eye tests for those who qualify. Otherwise, the average cost of a contact lens exam is £25.
How often do you need to have an eye exam? Why?
The health of your eyes is essential, and it is usually recommended that you visit an optician for an eye test every two years unless advised otherwise. Some may be advised to have more regular eye exams. This can be dependent on your age and medical history.
For those who wear contact lenses, eye exams may be required every six months.
Whether you experience any symptoms or not, eye exams are essential as they can pick up early signs of problems and detect underlying health issues such as diabetes, high blood pressure and multiple sclerosis.
Eye tests will also show you whether your vision can be further enhanced and improved upon with contact lenses or prescription glasses.
In regard to driving, eye tests are critical to determining whether your vision meets the legal standards to drive.
Do you need to get your eyes measured for contacts?
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.
Every eye is unique, which means that your contact lenses will be unique to you too. To do this, the optician will need to measure your eyes to get the right fit.
Contact lenses come in a range of sizes and the size prescribed to you will also depend on your preference of contact lenses and which type of lens you require.
What to expect during a contact lens fitting?
Firstly, you'll be asked a few questions about your lifestyle and preferences for contact lenses. Whether you'd prefer to wear daily disposable contact lenses, two weekly, monthly or yearly lenses, 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. They will also need to evaluate your tear film and the surface of your eye.
Cornea
Using a keratometer, your optician can 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 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 put in contact lenses and remove them safely.
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 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 guide on how to read a contact lens prescription.
