1. Done by: natalie bahsous and Charlie khalil
Sense of sight
Done by: natalie bahsous and Charlie khalil

2. introduction The eye is a sphere filled with two fluids
The skeletal muscles that move the eye are called the rectus muscles and the oblique muscles.
Only 1/6th of the eye’s anterior surface can normally be seen.
Protection for the eye
The rest of the eye is enclosed in a bony orbit.
A cushion of fat surrounds most of the eye.
It has two basic structures
Eyeball
Accessory structures

5. pupil Pupil is a central opening of the iris
Regulates the amount of light entering the eye during:
Close vision and bright light – pupils constrict
Distant vision and dim light – pupils dilate
Changes in emotional state – pupils dilate when the subject matter is appealing or requires problem-solving skills

6. lens Biconvex crystal-like structure
Held in place by a suspensory ligament attached to the ciliary body
Light passing through a convex lens is bent so that the rays converge to a focal point
When a convex lens forms an image, the image is upside down and reversed right to left

7. retina Extends anteriorly only to the ciliary body.
Contains receptor cells (photoreceptors)
Rods
Cones
Signals leave the retina toward the brain through the optic nerve.
No photoreceptor cells are at the optic disk, or blind spot

9. rods Hundreds of times more sensitive to light than cones
Provide vision in poor light.
Produce colorless (black and white) vision.
Nerve fibers converge so impulses produce more general outlines.

10. cones Provide vision in good light. Produce colored and sharp vision
Nerve fibers do not converge as much so impulses produce more detailed images.

12. There are three types of cones
Different cones are sensitive to different wavelengths
Color blindness is the result of lack of one cone type

13. Cones contain iodopsins
A group of pigments sensitive to light waves of different frequencies.

14. Physiology of EYE
Light waves from an object enter the eye first through the cornea, The light then proceed to the pupil
Fluctuations in incoming light change the size of the pupil.  When the light entering the eye is bright enough, the pupil will constrict due to the pupillary light response.

16. Vision interpretation
The light continues through the vitreous humor then, ideally, back to a clear focus on the retina, behind the vitreous.  The small central area of the retina is the macula, which provides the best vision of any location in the retina.
Within the layers of the retina, light impulses are changed into electrical signals.  Then they are sent through the optic nerve, along the visual pathway, to the occipital cortex .  Here, the electrical signals are interpreted or “seen” by the brain as a visual image.

20. How we can test our sense of vision ?

21. Test of visual acuity
It is a measure of the smallest retinal images which can be appreciated
By using a Snellen’s chart we can recode the visual acuity for distance and for near

23. A visual acuity test is a measure of how well you see or the sharpness and clarity of your vision. Your eye doctor will ask you to read letters on a chart while standing 20 feet away. The smallest letters you are able to read will be recorded as your acuity.
Your visual acuity may be written as 20/20 or (6/6) if your vision is normal. If your vision is reduced, it might be recorded as less than 20/20, such as 20/100.

24. Test of Color Vision
Red and Green color vision can be assessed using Ishihara test plate.
These colored spots forming numbers which the patient reads out

26. Pupillary Examination
Examine the pupil for the shape and symmetry
Ask the pt to fix the eye on a distant point straight ahead
Bring a bright torchlight from the side to shine on the pupil
Look for constriction of that pupil ( direct light reflex) and for the constriction of the opposite pupil ( consensual light reflex )