Looking for something?

Find it in our extensive resource library!

Smart Filters

  • Reset
  • Services

  • Who it's for

  • What it’s about

  • Format

View: 58

Download: 1

Fitting prisms – base out

It is important that you fit your prism in the correct orientation so please check the prism for where it is marked ‘BASE‘.

Photograph of prism with 'base' written on the bottom left

In your case the prism needs to be positioned BASE OUT. This means that the part marked BASE needs to be positioned towards the arm of the glasses. You can also hold the prism up to see which side is the base.

Diagram of side view of prism, as a series of triangles facing the same direction and 'base' written on the right

Side view of prism

If you feel the prism, there is a rough side and a smooth side. The smooth side needs to be positioned against the inside of the glasses.

Photograph of drawing on prism the shape of glasses to size

Using a felt tip pen or a biro, mark the prism to the size of the glasses frame, then remove the prism and cut to size. It will cut easily using a small pair of scissors.

Photograph of cutting prism to size and shape of glasses

You then need to put a small amount of water onto the inside of the clean glasses lens and press the smooth side of the prism down onto the water. You will be able to slide the prism around into place until it is dry. Once dry, it will be fixed well on to the lens.

Photograph of water on glasses to fit prism and move into place  Photograph of prism on glasses

If you need any further help please call the department on 0114 271 7468 and we can talk you through the process.

Is something missing from this resource that you think should be included? Please let us know

Contact us


Please note this is a generic information sheet relating to care at Sheffield Children’s. The details in this resource may not necessarily reflect treatment at other hospitals. This information is not intended as a substitute for professional medical care. Always follow your healthcare professionals’ instructions. If this resource relates to medicines, please read it alongside the medicine manufacturer’s patient information leaflet. If you have specific questions about how this resource relates to your child, please ask your doctor.

Resource number: EYE69

Resource Type: Article

How useful did you find this resource?*

If you need any further help please call the department on 0114 271 7468 and we can talk you through the process.


Western Bank
S10 2TH

United Kingdom

Switchboard: 0114 271 7000

Interesting Facts

We’ve got a special MRI scanner just for teddies so children can see what it’s like before they have a scan.

Help to transform our extraordinary hospital into something even better.

Sheffield Children's@SheffChildrens
“I moved to Sheffield to do my nursing degree – and stayed ever since!” Meet Nicola, one of our Advanced Nurse Pra… https://t.co/rmRUz6UJS0

As of 6 July 2022 everyone (colleagues, patients and families) must wear a mask. This applies to all spaces across. all sitesMore information on how we are keeping you safe is available here.

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.