so you've had your eyes examined and you've got your prescription but all you
really see is just a bunch of numbers in this video we're gonna have a closer
look at your glasses prescription and I'll help you to understand what it really
means once and for all. I'm Martin Oguzie and this is Martin's Eye Tips, thank you for
joining me. On this channel we're all about bringing you eye care tips, how to
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reminded every time I release a new video. So today this video is all about
your glasses prescription and we're gonna get straight into that right now
so for this video if you've got your glasses prescription to hand I suggest
you pull that out right now and then you can follow along as we go through the
boxes in the prescription. So this is what a prescription for glasses will
look like, now because it's personalized to you it must have your name on it and
be signed by the prescribing optometrist who will also have their practice
details on the prescription as well and also have some other detail on there as
well like the Recall time for your next examination and then it may or may not
have a pupil distance measurement. Now the PD or pupil distance measurement
is not usually mandatory so this may or may not be on the prescription as well
because really it's expected that whoever dispenses your glasses will make
this measurement at the time of dispensing themselves. Now your
prescription will always be separated into the right eye and the left eye,
now here in the United Kingdom where I live and work it's a nice and simple;
each eye's labelled right eye and left eye or 'R' and 'L'. Now in other parts
of the world rather than saying right and left it may say OD and OS and these
are Latin abbreviations for the word oculus Dexter for OD which simply means
right eye and also oculus sinister which means the left eye so a little bit
confusing but that's basically what it means so wherever you are in the world
you have a section for right side and a
section for the left iron measurement step so looking at the columns that
you'll find in the prescription the first box is usually the sphere which is
often abbreviated to SPH the sphere box is a lens power measurement that tells
us whether you have nearsightedness or farsightedness it's worth noting that
all lens powers are measured in units that we call diopters and this is often
denoted with a capital 'D' and the sphere power may be a plus positive number or
it could also be a minus negative number. If it's a positive plus power that
indicates that you have farsightedness which is also called hyperopia if it's a
negative minus power than indicates that you have nearsightedness which is also
called myopia. Now the larger the number after the plus or the minus sphere is an
indication of how nearsighted you are or how farsighted you are. The next two
boxes are the cylinder and the axis, the cylinders often abbreviated as just the
CYL and these two numbers go hand-in-hand so whenever you see the
cell and the axis present in your prescription this indicates that you
have astigmatism now from a fuller explanation of what astigmatism is you
can check out a video that I made previously on the eye astigmatism
explained and that's in the top right corner just over there. Now the CYL is
usually a negative number and is a measure of the power needed to correct
your astigmatism the higher the number is the more astigmatism you have now the
axis on the other hand is not our power measurement but rather its location
measurement and tells us in degrees where the laboratory needs to position
your CYL in order to line up with your astigmatism and to correct it and the
axis can be any number between 0 degrees to 180 degrees. Now in a more detailed
prescription report you may also find a box for prism and prism base and a prism
is an optical power that is worked into the lens to treat people with double
vision or eye coordination problems and it helps eliminate double vision and,
prism power is measured in Prism Diopters and the base is really just
a location where we want to put the base of that prism and that can be up down
left and right. Now most people never need a prism so they'll never see
anything written in the prism or the base box and the other number that is
common to finding a prescription is called the ADD. Now the ADD is usually an
additional reading power that we add on top of your distance prescription and
that combination makes up the glasses that you need for reading. The ADD can
also be an intermediate ADD and that's a power that we give to correct distances
in between your reading and your Farsight so this for example could be
for computer use or if it could be for any other hobbies that you may have in
between distances as well and this distance is worked out precisely and
then the intermediate ADD that helps you to have clear focus for that distance.
Now the reading ad is quite common for us all to experience from about the age
of 40 to 45 manual focusing just starts to fail and we start to the need this
additional focusing help close up now that happens regardless of whether or
not you choose to wear reading glasses that process still happens and it's a
process that we call Presbyopia you can find out more about that in a previous
video that I made just by clicking the link in the top right corner and that
will take you to that video and that there really is the essentials of
understanding your glasses prescription. Now for my Peace Of Mind Point; now if
you recently picked up your glasses prescription and your concern because it
looks drastically different to what you might have had previously then it may
not be anything to worry about at all now I could just be because of a process
that we call transposition which means that your prescription I can have one of
two forms that are identical and produce identical vision to the individual
looking through so the way to know whether the difference could be due to
transposition is to have a look at the CYL box and make sure that they're the
same sign. So either they both should be minus or they both should be plus. If one's
Plus on one's minus you know that they've been transposed differently. So why do we
transpose lenses in the first place well have a look at these two prescriptions
here and you'll see that they look drastically different but they're
actually the same prescription just once
converted to one form with the plus CYL and do the one is converted to the same
prescription with a negative CYL. Now you do got some Optometrists from the previous
generations that were using the plus CYL form that still continued to do so
and that may be why you may go to one practice and they're writing in plus and
another practice the writing in negative. Now there is an advantage to having the
two forms and one example could be that for example a lab who's making up your
glasses they may choose one form over the other because it may help to hide
the edge thickness of your prescription so; if you're somebody who is quite a
high prescription then you may find that in for example the plus form or the
negative form in my determine where the sides of your lenses are thicker or
whether the top on the bottom are thicker now often it can look
cosmetically better if we put the thickness on the top and bottom
rather than the sides it's because people see the size more than they do
the top on bottom so that's one advantage and allows your optometrist
and your practice to be able to choose one form or the other just for that
cosmetic benefit. So the bottom line is if you are do find a big difference
between your prescription from one visit to another particularly if you've been
to one practice in one year and to a different practice in another year then
the first thing you want to do is to be able to have a look at the the
CYL and make sure that they are both plus or both minus so; check that out first
before being overly concerned. Now for my Tip Of The Day... so my tip today is
just a little bit of guidance to help you to have a look at your prescription
and get an idea and indication of how that level of prescription will impact
your vision on the eye test chart so as a general rule of thumb if you are
nearsighted then every - 0.25 of prescription power that you've got will
lose you about one line on the eye test chart, so for example if you are - 1.00
then you can expect to be around about four lines above the 20/20 (US Chart)or the 6/6 (UK chart)
so if you're farsighted and
you're under the age of 40 the good news is that you're gonna be able to
compensate for your prescription a lot more and absorb a lot more farsightedness
before he starts to significantly impact your vision and you may find that you
might need about a +1.00 in prescription before you lose about a
line on the high test chart for people who are farsighted and about the age of
60 then you'll find that again every +0.25 will probably lose about a line on
a test chart as well so if you are about +1.00 then you'll find again you'll
probably be about four lines above the 6/6 or the 20/20 vision line. Now if
you've got astigmatism then ask an impact that rule of thumb I mean that it
may not work out quite as I've described but yeah that's just a general rule of
thumb that may be of help for people who want to have a quick look at their
prescription and get a rough indication of how that's going to impact them on
the eye test chart. My Question For You today is how's your prescription being a
problem to understand let me know in the comment section below if you want to
learn more about astigmatism then you can hit the link over here and it
will take you to my previous video on astigmatism but if you want to learn
more about whether you need glasses or not or prescription related things or
the eye test chart then you can have a look at the playlist over here and that
will give you that information as well so thank you for watching and I look
forward to seeing you in the next video remember also just to check out the
description box below and also leave me a comment as well below