My eye glass prescription calls for 24 prisms, can anyone tell me how they work to correct double vision?

Question

After being in a head on collision I developed double vision within a month. My Dr. prescribed prisms to correct the problem and for the first few years I went from 11 to 24 prisms. Now my vision has stablised to a large extent, but I would like to know how they work. Thank you.

Answer 1

24 is impressive, and it's going to make your glasses very thick, unless it's done with "stick-on" Fresnel lenses, which some what reduce best vision.

Prisms do not change the focus of a lens, but shift an image laterally, vertically or diagonally as required, so that if your eyes will not line up, the images will.
Suppose a right eye tended to look 5 degrees to the right of its partner. What the left eye saw as straight ahead, the right eye would see as 5 degrees to the left of straight ahead: double vision. (draw it on paper if it helps)
a prism shifting the image 5 degrees would let the right eye agree with the left as to what "looked " straight ahead, *even though the eyes were not straighter than before*.

In practice the prisms do not *usually* have to be in front of the non-straight eye, as long as the total amount of prism is appropriate and, for appearance, often half the prism is placed in each eye, to produce the same total effect.

If you still have some double vison or eyestrain, even with best prisms, consider and consult as to whether a back-up pair of glasses with one side frosted or blacked out might not be restful for occasional use. Experiment with a folded piece of paper to cover one eye if you like...
There is no risk of doing harm.
(optometrist, retired)

Answer 2

Our nurse is close, but no cigar. Prisms don't make the eye muscles do anything, they simply displace the images you see with each eye to make them fuse together as one, to alleviate double vision problems. OD and OS are always used...just as much as ever on optical prescriptions. But, the part about the visual acuity not necessarily being affected by the need for a prism is correct.

Answer 3

Please be sure to ask your optometrist or ophthalmologist to split the prism...12 diopters per lens. This way you won't be stuck with an ultra thick lens on one side. The splitting of prisms will balance the weight of the eyewear.

Answer 4

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