You can download this information in a printable pdf format by clicking on the link below.
What is a Fresnel prism and why use it
The Orthoptist has applied a Fresnel prism to your glasses.
Most common reasons are to stop or improve double vision (diplopia) but it may be used alongside eye exercises which you have been given by your orthoptist or to predict the outcome of squint surgery.
What are the benefits of a Fresnel prism?
- Relieves double vision
- Easy to change prism strength as your eye condition changes
- Less expensive option before having the prisms incorporated into your glasses, where possible
What are the disadvantages of a Fresnel prism?
- Prisms may cause slight blurring of your vision, due to the lines on the plastic
- They have to be fitted onto a glasses lens, however, if you do not need glasses to correct your eyesight, a pair can be made up with plain lenses
- It will become permanently stained by smoking
How do I clean my prism?
It is not usually necessary to remove the prism from your glasses to clean it, just wipe it with a lens cloth. If the Fresnel prism becomes too dirty it can be removed and cleaned with a soft toothbrush and soapy water and reapplied.
If your prism falls off you can:
- place the glasses lens under a gentle stream of water, to dampen the surface
- place the flat side of the Fresnel prism’s plastic onto the glasses lens and push out any air bubbles
- any excess water can be blotted away and allowed to dry
- it is essential that the prism is refitted in the correct orientation on the correct lens otherwise you may notice a worsening of your double vision
If your double vision recurs or changes between appointments or you have problems with the prism please telephone the numbers below.