Percentage of population with prism

[Daniel Cunningham]

Hello:

I teach the labs for the optical programs at NAIT in Edmonton, Alberta, Canada. I was teaching the students how to verify single vision prescriptions with prism, when one student mentioned that he had never seen a prescription with prism before. Several other students said the same thing. One student asked, How many people have prescriptions with prism in them?

The director of the program steered me here to get an answer.

So . . . what percentage of the population has a prescription with prism?

Thanks.

Daniel

[gemstone]

Just a Guess,
1.5 %. Prescribed

20% and rising undesired. (Due to all the amateur labs coupled with all the despensers that don't check or know how to.)

[EyeFitWell]

Our Doc prescribes it a fair amount, sometimes at powers so weak that the lab could completely leave it off and pass ANSI standards. (.25 per eye).
IMO, prism is:
1. Not well understood by Opticians and Lab Technicians (or at least those I've worked with)
2. Most likely to come back from the lab missed, forgotten, or just plain wrong.

I'd say gemstone is on the money. I also think many people wear it b/c their lab made a mistake that no one caught.

[HarryChiling]

I would say:

5-7% prescribed prism
30-35% yoked prism (progressives)
1-2% slab-off (this is considered prism)
a ton of unwanted prism (especially in children)

This would be my best guesstimates for the figures that you ask for. As mentioned previously most opticians don't have a firm understanding of prism or it's consequences. Most opticians don't understand that an off PD creates prism. and that to check for horizontal prism you must have an accurate PD taken from the patient and not from the glasses (or previous glasses).

Also most labs use prism everyday to grind the optical centers in the correct place, they might not understand how it is applied but they do use it daily. If your lab consistently misses prism you need a new lab.

[For-Life]

It has to be lower for precribed. I would say under 1 percent.

[Dave Nelson]

Depends on whose prescribing, but I would say 1 to 2 % on average. We used to have an optometrist nearby we nicknamed "Dr. Prism" since he prescribed prism 75% of the time.

[Jubilee]

We do have a lot of rx's that require prism. I myself have some BO prism in my glasses.

We have a lot of 1/2 Diopter increments, and some in lower powers.. however we have many patients that when they come in and we make their lenses, and the only change is the 1/2 diopter and 2 degrees of axis, they are impressed with how much clearer everything is.

I would probably guesstimate that we have 15% of patients wearing prescribed prism.

Cassandra

[HarryChiling]

I just thought, it must be odd that we see so many prescribed prism, but when I asked my doctor she said the same, 5-7%. She did also point out that we have a higher concentration of orthoptists and stribismus specialist in the area.

We have also built ourselves up as a niche practice that can handle most difficult Rx's on the first try and have them done in record times. I often surface high Rx's (-13.00 - -21.00) with next day service, it has built us a reputation in our area.

[mike.elmes]

Hello:

I teach the labs for the optical programs at NAIT in Edmonton, Alberta, Canada. I was teaching the students how to verify single vision prescriptions with prism, when one student mentioned that he had never seen a prescription with prism before. Several other students said the same thing. One student asked, How many people have prescriptions with prism in them?

The director of the program steered me here to get an answer.

So . . . what percentage of the population has a prescription with prism?

Thanks.
Daniel Hi Dan!! Great to see a fellow Optician from Edmonton here. Rocky and I are in Bonnie Doon Mall....This forum is a great resource.

[Barry Santini]

How many people have prescriptions with prism in them?
Thanks.

Daniel

As many people as have their PDs mis-measured:
1. Taking/using binocular rather than monocular PDs
2. Assuming the premise of the visual axis and the corneal reflection is generally representative, then those dispensers using PD rulers rather than CRPs.
3. Those that give myopes face form, or hyperopes little or reverse face form. Check the wrap calculator.
4. Not to mention SV pupil heights
5. And oh holies: What about thinning prism in progressives?

Barry