P Lab: Vision Flashcards
Visual Perimeter
MEasurment of the visual field function
Visual Acuity
Clarity of Vision. It is determined as the smalles letters/symbols one can read on a standard chart (Snellen Chart)
Optic disc
exit of optic nerve fibers, blind spot, optic nerve head
Astigmatism
spherical abberation (irregularly shaped cornea)
Glaucoma
increased intraocular pressure due to incomplete evacuation of aqueous humor via Schlemm’s canal
Macula degenration
damage to the macula, the area of sharpest vision
Myopia
eyes are too long for its optical powers (image is formed in front of the retina)
Hyperopia
eyes are too short for its optical power (image is formed behind the retina)
Achromatopsia
Loss of color vision due to lesion of cortical area V4
Protanopia/protanomaly
missing/malfunctioning L-cone (red); sub-form of red greeen blindness
Deuteranopia/deuteranomaly
missing/malfunction M-cone (green)
subform of red-green blindness
Tritanopia/tritanomaly
missing/malfunctioning S cone (blue)
Snellen Chart
an eye chart used to measure visual acuity
Sloan letters
optotypes to test visual acuity; used in Snellens chart
What is one letter element on the Snellen Chart?
a horizantal bar in an E subtends 1 minute of arc at the indicated distance (20 feet for the 20/20 line)
2 min of arc is a measurement of?
one letter element and one interspace i.e one period of a sinusoidal grid
Landolt C
A broken ring
uses a single optotype placed in a different position
Lea test
pediatric vision test
pictures of animals and objects
to test visual acuity
Amsier grid
test for macula degenration or another vision problem
Do the lines look wavy or areas of visual field missing?
Ishihara test
color vision deficiency
Astigmatism wheel
radiating spokes placed at angles of 10 degrees
any inequality of the wheel signals astigmatism
How do yo correct for myopia?
Use a concave lense which will disperse the image
How do you correct for hyperopia
Using a convex lense which will focus the image
Which type of color blindess is most common?
Red-green
Red green blindness
More common in males
X chromosome linked
Which type of color blindness is rare?
Blue
Chromosome 7
What is the prevelance of blue blindness between men and women?
Gender equality
What conditions can be diagnosed through perimeter testing?
Visual field deficits
What is diopter?
A unit of refractive power that is equal to the reciprocal of the docal length (in meters) of a given area
