Today we are talking about visual acuity and this is known as the Snellen
chart. I'm going to talk to you about how to set it up, what do all these
numbers mean, when should I see an eye doctor right
after
this.
Welcome back my name is Tammy and this is NurseMinder and on this channel we do
everything nursing so if you're new here consider subscribing below so that you
get the next video when it's released. Now to establish a place to put your
Snellen chart you need to have 20 feet and so that wall over there
we've had to come down into my basement here to set this up,
I'm going to be putting up the Snellen chart and demonstrating how to use it
next. Now you'll want to pick a well-lit area
the height of the Snellen chart is 64 inches to the 20/20 line
and you want to measure 20 feet back for your patient to stand.
Now as your patient is standing at the 20 foot line you're going to be pointing
at different areas on that map and asking them to read the line that you
point to, but we're going to do it one eye at a
time and so you'll want them to cover up their eye
with either the palm of their hand or a piece of paper so that there's no
cheating, because if they use their fingers they can see through
and then that might skew your results. Now you can do one without glasses and
with glasses, we definitely want to note that
in your annotation if you're doing both, but typically we'll just leave the
glasses on to see what their visual acuity is. So let's
begin our test can you please read line one
e f p three t o zed four l p e d five p c e f
e d six and I can't read that last line at all. Now when it
comes to determining the actual value that we're going to assign for that
patient's visual acuity there is something you need to be aware
of and that is the patient can make two errors on a line and still get
credit for that line. If they make more than two errors or
they're unable to read the next line then that is where we would stop. So in
the case of this assessment, able to read line five with one error
and then unable to attempt line 6 and you noted signs of squinting and leaning
forward, which are troublesome signs. So we're
going to go back to line 5 and give credit for the line 5 visual acuity
which is 20 out of 40, so at 20 feet they can see what most people would be
able to see at 40 feet and there was one error made so we're
going to put a minus one. Okay now in assessing the left eye you
want to employ a few different strategies to make sure they're just
not repeating what they've just said to you. One of the strategies I will share
is to start at a different line so you don't have to start at number one like
you did the first time, you can start at line three and then you
can skip to line five or you can have them read it backwards;
that's the second tip is to go to line four
and read it backwards and that helps you to ascertain that what they're reading
is authentic for their vision. Then of course once you've done the left
eye you want to do both eyes together so you have the full picture
and that would be your visual acuity assessment done using this Snellen chart.
So the real question is what does 20/20 vision mean?
In order to understand this, we need to know that the top number represents how
far you're standing away from the chart and the bottom number is the
distance in which a normal eye would be able to read
that particular line. So for example 20 over 200 means that you are standing at
20 feet away from the chart and you can see at 20 feet what others
can see at 200 feet. That is not very good. Now on the other
end of that spectrum if you are standing at 20 feet
and you have 20/10 vision that means you have better eyesight because
another person would have to stand at 10 feet to see what you can see
at 20. So the Snellen chart is typically used for those who
are school age and above and they, you know, we have to make sure they can read
and understand their letters. If you're dealing with somebody who is
younger they do have pictures on the back side
or there's another one that uses just the letter e and it has
the e in different orientations and the child
is then asked to identify which way the e
is facing. So you may note that there are a few different ways in which your
doctor is testing your eyes. That's it for me today. I hope
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