What you will learn today . . .

Vision is a complicated process, and we can use several tests to measure the proper function

What you will do today…

Conduct the tests used to evaluate visual acuity, astigmatism, the ability to accommodate for close vision, and color vision

Describe four conditions that can lead to defective vision

Demonstrate the blind spot, photopupillary reflex, and convergence reflex

Sight Lab

Cow Eye Dissection

Dissect a cow eye to observe the major structures of sight

Visual Acuity Use a Snellen Chart to

determine your acuity 20/20 vision is normal

Example: If you have 10/20 vision, you have worse than average vision. You must be 10 feet away to see what the average person can see at 20 feet.30/20 vision is better than average.

Astigmatism Test

Astigmatism is a condition where some parts of an image are sharply focused, while other parts are blurred

It can be diagnosed using an astigmatism chart

Accommodation Test

Measure the shortest distance at which the eye can see an object clearly, moving toward the eyeball

Color Vision Test

Use the Isihara Test to determine any color blindness

Blind Spot Demonstration

Blind spot: the area on the retina where the optic nerve and blood vessels enter and leave the retina, thus there is no visual reception

Pupillary Reflexes

Shine a light into the eye and measure the pupil

Measure the size of pupil when focusing on objects at different distances

Negative After-Images: Complementary Colors

Look at a very bright scene or color and then look at a white surface. Record your observations

Binocular Vision and Space Perception

Observe how objects look differently with one eye closed

References http://www.developertutorials.com/images/arti

cles/jongos/reflectiveeye/1369517153_5d1f4c562a.jpg

http://apps.uwhealth.org/adam/graphics/images/en/10184.jpg

http://www.beaconlearningcenter.com/WebLessons/MeasuringTools/METRIC_RULER2.gif

http://benskerrett.com/blog/wp-content/uploads/2008/03/binocular-vision.jpg

http://serviceworksconsulting.com/blind_spot/a_blind_spot.gif

http://www.flightglobal.com/blogs/terminal-q/dice.gif

References http://www.optivision2020.com/image-files/snellen-chart

.jpg http://www.artemis-uk.org/Figures/1919_eclipse_negativ

e.jpg http://www.ext.colostate.edu/pubs/garden/gardimg/

07238f01a.jpg http://www.colblindor.com/wp-content/images/ishihara-

transformation.jpg http://district.bluegrass.kctcs.edu/billd.snyder/

sharedfiles/biowebsite/BiologyLabs/BIO137/137Lab10/Lab10Images/CowEyeCoronal-label.jpg

http://www.logosoftwear.com/embroideryclipart/Needle%20&%20Thread.PST844.gif