http://www.eyecareamerica.com/eyecare/anatomy/
SCLERA:
The sclera is the white of the eye.
"Don't shoot until you see their scleras."
Exterior is smooth and white
Interior is brown and grooved
Extremely durable
Flexibility adds strength
Continuous with sheath of optic nerve
Tendons attached to it
CORNEA:
IRIS:
Iris is heavily pigmented
Sphincter muscle to constrict or dilate the
pupil
Pupil is the hole through which light
passes
Pupil diameter ranges from about 3-7 mm
Eye color (brown, green, blue, etc.)
dependent on amount and distribution of
the pigment melanin
The cornea is the clear bulging surface in front of the
eye. It is the main refractive surface of the eye.
Normally transparent and uniformly thick
Nearly avascular
Richly supplied with nerve fibers
Sensitive to foreign bodies, cold air, chemical irritation
Nutrition from aqueous humor
Tears maintain oxygen exchange and water content
Tears improve optical quality
http://www.eschoolonline.com/company/examples/eye/eyedissect.html
Legally Blind
The definition of Legal Blindness is used to determine who can get
government services for the blind. Only 1 in 10 people who are legally
blind see nothing at all. A person with normal eyesight has 20/20 vision,
right? Legal Blindness, in the USA, is defined as vision of 20/200 or less in
the better eye with best correction, or a visual field of 20% or less. We
have the Snellen Chart, the eye chart, to blame for these fractions. The
line on the eye chart a person with 20/200 vision sees at 20 feet a person
with normal vision sees at 200 feet. The 20 degrees or less refers to tunnel
vision. If you look through a toilet tissue tube your vision is restricted to
less then 20 degrees. You can have 20/20 vision with a visual field of less
then 20 degrees and be considered legally blind.
Myopia – (nearsightedness)
People with Myopic vision usually have eyeballs that are too large for
their lens and cornea to focus light properly on their retina. Eyeglasses
and contact lenses can usually correct this problem.
Hyperopia - (farsightedness)
Hyperopia vision is caused by the eyeball being too small for the lens
and cornea to focus light properly on the retina. Eyeglasses and contact
lenses can usually correct this problem.
Presbyopia - (aging eyes)
As people age, they often begin to have difficulty focusing their eyes for
reading or close work. It is usually corrected with reading glasses
glasses. Some people may need bifocal lenses.
Astigmatism - (distorted vision)
People with Astigmatism have an irregularly shaped cornea. It is usually
corrected with eyeglasses or contact lenses.
Cataracts
There are over 1 million Cataract operations performed annually in the
USA. Cataract surgery is an outpatient procedure with a very high
success rate. Due to the lack of modern medical technology in the
developing world, it is also the leading cause of blindness. Over 16 million
people are blind from cataracts.
Age-Related Macular Degeneration - (AMD)
This is a degenerative disease of the macula; the macula is the part of the retina
responsible for central vision There is no way yet of repairing the vision that has
been lost, but if detected early laser surgery can help slow the progression of the
disease. (AMD) is the leading cause of vision loss in people over age 65. Eight
million people are legally blind from macular degeneration worldwide and as the
population ages this number is expected to grow.
Glaucoma
This disease increases the fluid pressure inside the eye, leading to loss of
side vision and eventually total blindness. The increased pressure
destroys the optic nerve. With early detection, it can be kept under control
with pressure reducing eye drops and surgery. Chances of developing it
increase with age. There are over 5 million people blind from glaucoma
worldwide.
Diabetic Retinopathy
This complication of diabetes is a leading cause of blindness among
middle-aged Americans. The longer a person has had diabetes the more
apt they are to develop diabetic retinopathy. Laser surgery can slow the
progression of this disease along with management of blood glucose
levels. There are 2.4 million people blind from retinopathy worldwide.
Retinitis Pigmentosa - (RP)
This rare inherited degenerative disease slowly destroys the retina. Signs
of (RP) first show up in early childhood. The side vision is lost first. The
disease progresses over many years leaving the person with only a small
portion of their central vision. There is on cure for (RP) yet. There are 1.6
million people blind from (RP) worldwide.
Eye Injuries
Over 1 million people are blind worldwide from eye injuries. 90% of injuries
can be avoided by using proper eye protection. Any eye injury is a medical
emergency.
Retinopathy of Prematurity - (ROP)
This is an eye disease of premature babies. Soon after birth, abnormal
blood vessels start to grow on the retina, eventually destroying it. No one
is quite sure what causes this disease, but premature birth and low birth
weight are thought to be the main causes. With modern medical
procedures, only 400 babies a year go blind from this condition. In the
1950's the number of babies blind from (ROP) reached epidemic
proportions.
Neurological Visual Impairment (NVI)
Children with (NVI) have normal eyes, but a part of the brain responsible
for seeing is damaged. It can be caused from a lack of oxygen before,
during, and after birth. Diseases like meningitis or traumatic brain injury
can also cause it. Many of the children with (NVI) are multi-handicapped.
Vision loss can be temporary or last a lifetime.
Ocular Albinism
With this inherited birth defect, people have no pigment or reduced
pigment in their eyes, skin and hair. This pigment called melanin is
needed for the full development of the retina. Children with this condition
have mild to severe vision loss and are very light sensitive.
Coloboma
Coloboma is a Greek word, which means mutilation. People with Coloboma are missing
a portion or structure of the eye. The human eye develops between the fourth and
fifteenth week of pregnancy. As the eye starts to develop, a gap opens on the underside
of each eye bud. This gap provides a way for the developing eye to be nourished. This
gap, called the optic fissure, has to close before the eye is fully developed. Coloboma is
the incomplete closer of the optic fissure. Gaps can occur in the eyelid, iris, ciliary body,
lens, retina, macula, choroid and optic disc. It can cause from mild to sever vision loss.
Coloboma occurs in about 1 in 10,000 births.
Preventable Vision Loss
Over 90% of the world's blind people live in developing countries. Many
diseases can be prevented with education in basic hygiene, proper nutrition
and medical care. Conditions unheard of in the modern world like: Trachoma,
Onchoceriasis (river blindness) and nutritional blindness (vitamin A
deficiency), are the leading causes of vision loss in these countries.
Optic Nerve Hypoplasia
With this birth defect the optic nerve that connects the eye to the brain has not
developed properly or it is underdeveloped. This happens before birth leaving
the child with mild to severe vision loss.
Myth: Safety goggles are more trouble than they are worth.
Fact: FALSE. There are 500,000 eye injuries every year in the USA. 50%
of these accidents occur at home. The leading cause of blindness in
children is eye injury. 90% of injuries can be avoided by using proper eye
protection
Myth: Wearing poorly fit glasses damages your eyes.
Fact: FALSE. The right eyeglass prescription is required for good vision.
Poor fitting glasses do not damage your eyes
Myth: Poorly fit contacts can harm your eyes.
Fact: TRUE. Poorly fit contact lenses can damage your cornea. If you use
contact lenses, have them checked regularly
Myth: Reading in dim light will damage your vision.
Fact: FALSE. Reading in dim light can make your eyes feel tired. It is not
harmful and cannot damage your vision.
Myth: It is harmful to look at the sun - even if you squint or use dark glasses.
Fact: TRUE. The direct light from the sun can blind a person in less then a
minute. The sun's ultra-violet light will still get to your eyes, damaging the
cornea, lens and retina. Never look directly at a solar eclipse – regardless of
squinting or sunglasses.
Myth: Too much sex, especially masturbation, can make you go blind.
Fact: FALSE. Syphilis, a sexually transmitted disease, if left untreated can
lead to blindness, dementia and death. This is where this myth came from.
Myth: You can cure a black eye by putting a raw steak on it.
Fact: FALSE. Putting a steak on your eye will do nothing except expose your
eye to any organisms living on the raw meat. Get immediate medical attention, a
black can be a sign of serious eye injury.
Myth: Eating carrots will improve your vision.
Fact: FALSE. Carrots are high in Vitamin A, which is important for a
balanced diet. Eating carrots or other foods high in Vitamin A will not improve
your vision. Taking large amounts of Vitamin A can be very harmful. People
that do not eat a balanced diet can develop vision problems along with other
problems as they age.
Myth: In order to travel independently, a blind person needs a guide dog.
Fact: FALSE. To travel independently most Legally Blind people do not
even need to use a Cane. Very few use dog guides. Approximately
1,300,000 Americans are (Legally Blind); 109,000 of them use white canes;
7,000 use dog guides.
Myth: Sitting close to the television will harm your eyes.
Fact: FALSE. There is no evidence that sitting close to the television will
damage your eyes. If this were true, office workers that sit 8 hours a day 17
inches from their computer screens, would all be blind. Sit wherever you are
most comfortable when watching TV.