Given to measure individuals visual acuity Given as part of
physical exam or to detect eye disease Conduct exam in a
well-lighted room (natural light, with no direct sunlight Watch for
squinting, leaning toward eye chart, closing one eye when both eyes
are being tested, excessive blinking, watering of eyes
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Snellen chart Used to test distant vision>
nearsightedness=Myopia Come in a variety of types> some contain
pictures for use with small children, some contain letters of the
alphabet, some contain the letter E in a variety of positions (pt
points in the direction that the E points- used for non English
speaking people or nonreaders) When standing 20 feet from the
chart, a person with normal visual acuity should be able to see
characters that are 20mm high= 20/20 vision (top number represents
distance and bottom number represents height of the
characters)
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Examples Person has 20/30 vision Means when standing 20 feet
from the chart, pt sees characters 30mm high Also, it means that
this pt standing 20 feet from the chart can see what a normal
visual acuity pt can see standing 30 from the chart Person has
20/100 >person can only see characters 100mm high standing 20
feet from chart >person with normal visual acuity would be able
to see same figures while standing 100 feet from chart
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Hyperopia (farsightedness) Problems reading small print and
seeing close up Use the Jaeger system to test Uses a printed card
with different short paragraphs> each paragraph is printed in a
different size type, ranging from 0.37 to 2.5mm high; card with
different characters/pictures is available for small children or
individuals who cannot read> card is held 14-16 inches away from
eyes Pt will read printed text or identify pics that gradually
become smaller> smallest print/pic that the pt can read without
error is recorded
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Color vision Tested using the Ishihara method Ishihara book has
a series of numbers printed in colored dots against a background of
dots in contrasting color Pts with normal color vision can identify
the numbers Pts with color blindness either are unable to see the
numbers or identify incorrect numbers Most accurate conducted in a
room with natural daylight and not bright sunlight
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Terms/Abbreviations OD= right eye (oculus dexter) OS= left eye
(oculus sinister) OU= both eyes; each eye (oculus uterque) Myopia=
nearsightedness> defect in distant vision Hyperopia=
Farsightedness> defect in close vision Ophthalmoscope=
instrument for checking the eyes Tonometer= instrument used to
measure intraocular pressure (increased pressure could mean ?)
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Procedure Assemble equipment; check lighting; wash hands;
introduce yourself; identify pt; explain procedure to pt Snellen:
Pt will stand facing chart, toes on taped lined, pts eyes will be
20 feet from chart What if pt wears glasses/contacts? Watch and
make sure pt is not? Use an eye shield (occluder) to screen each
eye- Ask pt not to close eye that is covered. Why? Make sure you
_________ occluder after each pt use. Use abbreviations OD, OS, OU
to document results
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Jaeger Seat in comfortable position Pt to hold Jaeger card
14-16 inches from eyes Pt will read paragraphs out loud (If pt
cannot read- provide Jaeger card that contains pictures/characters)
Have pt read with OS, OD, and OU > record smallest line of print
pt can read with OS, OD, and OU
Slide 13
Ishihara (color vision) -Seat pt in a comfortable position
-Hold plate approx. 30 inches from pts eyes -Ask pt to read number
on the plate -Some plates contain color lines instead of numbers-
Ask the pt to trace the line with a finger -Document how many
plates the pt identifies correctly with OS, OD, OU - Report any
frame that the pt misses so that the MD can determine type of color
blindness