Optician Training: What Is Prism?

– Hello and welcome back. Today, we are going to
start talking about prism. (upbeat music) Yesterday, not such a
good day in some ways. I shot this opening sequence,
I think 15 times in about six different ways, and I
just couldn’t get it right. So, I set it to the side,
shot the white board lesson, came back out here this morning and I’m gonna give it another try. And I think I got it. Insteada talkin’ and talkin’ and talkin’, I think I’m gonna let
this sum up this way. You will learn as much about prism that you need to in order
to be good about your job. Why would I say that? In my 20-plus years as an optician, working daily, hands on, busy practices, busy stores, I saw a prism maybe 100 times and that is out of thousands and thousands of jobs that I’ve seen over those years. I don’t know where I fall on the scale. You may work at a doctor’s office that does prism 9 out of
10 jobs, I don’t know. You may be at a doctor’s office or a store that never does it. Wherever you fall along that scale, is going to be what you
need to get out of this. And I’m gonna let it
just settle right there. We are gonna look at prism. They are wicked cool things. And we are gonna spend some time at the bench, just briefly. Then, we’re gonna hop over to our very good white board lesson. Remember, I shot it yesterday,
so I already know that. This is a 35 diopter ophthalmic prism. You can buy these online from
a company called Burnell. There is their address
right there for you. They’re not very expensive. If you could, I would get
maybe a 10, a 20 and a 30. If you’re struggling with
this, it certainly may help you grasp the concepts a little better. And they’re just plain
kind of fun to play with. Everything that we do
from this point forward is gonna work on one basic principle. And that is an image when
viewed through a prism is shifted towards the apex. Remember that our prism has
a base and it has an apex. Here is a black line. No magic here. If I move this prism over
my object, or my black line, you will see that it shifts
in appearance towards the apex of the lens. This 35 diopter prism is
quite strong, it’s why the effect is pretty dramatic. That’s it. That’s really about all
we needed to cover here on the bench. I want you to be the best
darn optician that you can. And I want you to truly
understand what it is that you’re doing and why
it is that you’re doing it. So for those of you that
are with me and want to take the baby steps and
build the foundation that you need to be the
best optician that you can, then just bear with me
for the next ten minutes. And we’re gonna get through it. This is how I think about this stuff. Everybody learns in a different way. That’s one of the keys to education. This stuff may work for you. It may not. If it does, fantastic. Let’s give it a try. In the perfect world, perfect scenario, this is how things work. You’ve got the sun and the
sun is pouring billions of rays of light down,
and it’s hitting objects like our little fire plug or fire hydrant, whatever you want to call it there. The rays of light reflect off objects and they hit somebody’s eye. Could be your eye, could be mine. And it ends up in your brain. Those rays of light, because
this eye is perfectly healthy, a great clear cornea, crystalline
lens, good vitreous humor, healthy retina, great optic nerve, no interpretation problems in the brain. All those reflect rays give
you everything that you need to understand that the
object that you’re looking at is in fact a fire hydrant. It’s in the right place, it’s
red, it’s about two feet tall, it has one, two, three, four openings. Everything looks great. There’s no visual acuity problem, there’s no refractive errors. Everything that I’m
going to be talking about for the next few minutes
is all based on the idea that we’ve got a healthy
eye, healthy brain, everything’s working just fine. What happens when I put a prism, that one that we were talking about
just a few moments ago over on the bench, and I place it between my healthy normal eye, my
perfectly working brain, and my object? What happens to that object
as it’s perceived by my brain over here, is that it
will appear to shift position towards the apex of my prism. What we just did on the
bench just a minute ago. If I call this a one
diopter prism, I can predict with pure and perfect
mathematical accuracy that my object, my viewing
point is going to shift from where it is to one. If I make that prism
a little bit stronger, and I say it’s a two, I can
predict with pure accuracy, predictability, that my object
will now shift that far. Let’s take it one step further of course, you can kind of see where this is going. If I make it a great big fat prism wedge, and I say it’s a three, I can predict that it will shift from here to here. It is the predictability of
that shift in relationship to viewing through the prism,
that shift towards the apex, that lets us move object around in the brain through the
eye for people that don’t have this perfect scenario going on. Now let’s talk about what happens when we have a problem between here and here. We no longer have the perfect situation. Our cornea is misshapen in some way, maybe too shallow, maybe too steep, maybe it’s astigmatic, maybe
it has two curves on it. Maybe our crystalline lens
is getting clouded over. Maybe our vitreous humor
is a little bit cloudy. Maybe there’s a problem,
a compromise somewhere in the fovea, the macula, the retina. Or perhaps our poor little brain up here, which has got so much going on, there’s so much between
here, and here, and here, and here, that can go wrong here. Sometimes I always
wonder how we see at all. But anyway. When I have a problem here,
and I’m looking at my object, my fire hydrant may
appear blurry, or fuzzy. It may seem distorted in some way. It may seem misshapen, particularly if I have a high astigmatism issue. To correct for that, so I
have this looking correct to my eye and my brain, obviously, we start using prescription lenses. The difference between
the prescription lens and these simple prism
lenses, is that we start playing with the shape,
the size, and the position. Remember our old friend
here, that very first lens that we looked at together? Remember that I can move this
around in front of my eye? I can place the power
where I need it to be. In order to get this sharp,
I start playing with the shape of the prisms, the size
of them, the position of them. These could become anything. If you stop and think about
it, it’s almost mind boggling. In sphere powers, you run in normal range, let’s say about plain O to
20 in both plus and minus. That’s about 40 times
quarter diopter steps. Cylinder you got about zero to 10. And you’ve got 180 possible
degrees of position. It’s mind boggling the variability
that we could have here. Plus lenses, astigmatic, a
little bit weaker in one part, a little bit stronger in that part. I could rotate the lens
around in front of the eye. I can fine tune this,
I can fine tune that, I can fine tune position, and
I can put in front of my eye, I can work my eye and my brain in concert, and I can get this to
look beautiful, sharp, crisp, clear, by using
prescription lenses. Now, what happens when it’s blurry, and it’s a little misshapen,
and oh man, it’s up here, when it shoulda been down here. Or worse, it’s down here
and shoulda been up here. What happens then? Prism. Astigmatism. I have two different powers on the lens. This one’s a little bit
weaker than this one. This one’s a little bit stronger. I can move my lens
around, I can fine tune, I can get it looking beautiful,
perfect, sharp, clear. But in order to move it
back up to where it belongs, I’m gonna add additional prism. That additional prism
wedge in the correct place, the correct power, will
allow me to also move it back to where I need it to be. So the combination of
these three, if you will, lets me fine tune this
to be in any position that I need it to so that
my eye sees it and my brain sees it in the right place,
looking the right way. Badump-bump-pa. Basic prism theory.


  1. Im a little confused , is the base or the top of the prism controls the position of the object ,cus from what I know the prism is described by it base!

  2. It's a good video, love the hands on examples and pictures. However, one thing I would say is no need to qualify your reasoning or statements unless necessary. It lengthens the video quite a bit. Thank you again for the upload.

  3. Great and informative video. Also great presented!
    Bare in mind that prism only works when using both eyes together. It does not work when the patient is blind in one eye or suffering from heterotropia .
    Thanks for sharing!

  4. I was hired as an optician at an early age and really only new there was a job that sounded very interesting and offered an opportunity to challenge myself and grow as a person wishing to enter the field of optics. It has taken much time and learning to even be comfortable to explain to a patient the complexities of an Rx, and I really had to take a moment to thank you for the time and methodology you have taken to teach your own personal experiences. Your videos have been very helpful.

  5. Hey! There is one point you did not point out, that is how to decide if BI should be on left or right eye. Or BD on left eye or BU on right eye should be applied. I found the answer, if BI is in the wrong eye, when you look at a pair of speakers playing music, it will appear the sound is not coming out of the speakers but somewhere next to it. Hence correct prism is perfected when sound and sight overlap is achieved and it is something I had to work out myself as a patient and ask the optometrist to make changes to the prescription until I had the BI perfect.

  6. I have cataract in my both eyes and Phoria(squint) problem as well, i had my left eye operated not one year ago but still that problem is here, will it be cured if i have my right eye operated too? Please help.

  7. I'm having a hard time reading prism in a lensometer if there are two directions. For example if it's 3 BO and 1.5 base up. The base out is fairly easy to read, but the 1.5 I just don't see or get. Can you help?

  8. I realize your videos are geared toward opticians, but as a consumer they are incredibly helpful. This video especially! I'm amazed by how complicated optics can be but yet there is legal, allowable margins of error! I've discovered I'm quite sensitive to things being just slightly off, needing to know how to explain what I require in terms opticians understand.

  9. I started off as a optometric tech after never being in optics ever. The place I work is very busy. They found me to be hard working and want to promote me to salesperson but I’ve only been in optics for 3 months and all this information is so much to take in at once. Really appreciate these videos because me knowing what they need will make me and my customer very happy and that’s what I want. Thank you for the time you put into these videos, you have helped me a lot!

  10. I'm learning so much! Thank you so much for doing these videos! I started 3 years ago at an optical having absolutely no knowledge of optical work or even receptionist work and I've been promoted to training optician! It is very difficult to me as someone who is not math brained at all but your videos are so helpful!

  11. I'm taking your online visionworks course and am so excited to become an optician. Unfortunately I cannot order the prism. Looks like they only sell to professionals

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