Frequently Asked Questions
Select a question below to find the answer
If your prescription for spectacles or contact lenses is out of date is it recommended that you have an examination, before ordering spectacles or up dating your contact lenses. The examination is not just to check your prescription in terms of numbers, but also checks the health of your eyes and the problems that can be caused by long term contact lens wear. This is very important to make sure you have the best care when it comes to your ocular health.
If you are a contact lens wearer it is almost essential that you also have a pair of spectacles as a back up. If there is any reason you cannot wear your lenses, such as an infection, then you will need to have a pair of spectacles to do your daily tasks, such as driving. Most contact lens wearers will also have spectacles and in some European countries it is illegal to not have a back up pair of spectacles in your car (but not in the UK at present). If you cannot wear your lenses and have a complicated prescription you may have to wait longer for your spectacles to be made, meaning you have nothing that will correct your vision for a period of time.
Your spectacle and contact lens prescription are always different, as the contact lenses sit directly on your eye, so are usually weaker in power. The spectacles sit on you nose, with a gap from your eye to the back of the lens. This gap is called the back vertex distance and changes the numbers on your prescription, making it read slightly different to your contact lenses.
There are two different ways to write a prescription, one is called ‘in minus cyl’ and the other is called ‘in plus cyl’, this means that two prescriptions can look totally different, but when transposed by a qualified Optician it can be exactly the same. Some Optometrists write their prescriptions using one method and others can write them using the other method.
The majority of the general public will have some degree of astigmatism in their prescription. This is where the eye, instead of being completely spherical like a football, can be more rugby ball shaped. It is not something to worry about and the Optometrist will assess the degree of astigmatism in your examination and this will form part of the final prescription to correct your vision.