Fitting prisms - base out - Resource Library - Sheffield Children's NHS Foundation Trust

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.

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.

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Disclaimer

Please note: this is a generic information sheet relating to care at Sheffield Children’s NHS FT. These details may not 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 this information has been translated into another language from English, efforts have been made to maintain accuracy, but there may still be some translation errors. If you are unsure about any of the guidance in this resource or have specific questions about how it relates to your child, always ask your healthcare professional for further advice.

Eye Department Children, parents and carers Strategies Article

Resource number: EYE69

Resource Type: Article

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

Fitting prisms – base out

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