Anatomy of the Eye
with some fact of eye diseases ( courtecy;-
medicinenet.com )
Many Americans Miss the
Mark on Eye Diseases and Conditions.
When it comes to signs
of eye disease, Americans are blind to the facts. A recent survey showed that
while nearly half (47%) of Americans worry more about going blind than losing
their memory or their ability to walk or hear, almost 30% of those surveyed admitted
to not getting their eyes checked.
The following slides
take a look at some of the signs and symptoms of some of the most common eye
diseases.
Anatomy of the Eye
The anatomy of the eye
is complex. The main structures of the eye include:
·
Cornea: clear tissue in
the very front of the eye
·
Iris: colored part of
the eye surrounding the pupil
·
Pupil: dark hole in the
iris that regulates the amount of light going into the eye
·
Lens: small clear disk
inside the eye that focuses light rays onto the retina
·
Retina: layer that lines
the back of the eye, senses light, and creates electrical impulses that travel
through the optic nerve to the brain
·
Macula: small central
area in the retina that allows us to see fine details clearly
·
Optic nerve: connects
the eye to the brain and carries the electrical impulses formed by the retina
to the visual cortex of the brain
·
Vitreous: clear,
jelly-like substance that fills the middle of the eye
As you read this
slideshow you may need to refer to this illustration for reference.
Glaucoma
Glaucoma is a
group of eye diseases that develop due to elevated intra-ocular pressure (IOP)
within the eye. The increased pressure affects the optic nerve and may cause
vision loss. Glaucoma is classified either as open-angle (the more common form
that is usually painless) or angle-closure glaucoma (which often occurs
suddenly and is associated with pain and redness of the eye).
In the early
phases of glaucoma there are often no symptoms. By the time vision is affected,
the damage is permanent. Progression of glaucoma can be slowed or halted with
eye drops, laser treatments, or surgery so early diagnosis is key.
Cataracts
A cataract is a
painless cloudy lens in the eye that causes blurry vision. It progresses slowly
as we age (most people who live long enough will have some cataract-like
changes to their cornea). Other causes of cataracts include diabetes, trauma,
some medications, and excessive UV light exposure.
Your doctor can
see a cataract while doing a routine eye exam. Treatments for cataracts include
eyeglasses, magnifying lenses, or surgery. Surgery is curative as the cloudy
lens is removed and replaced with an artificial one. The need for surgery and
the risks involved should be discussed with your eye doctor.
Age-Related Macular Degeneration (AMD)
Age-related
macular degeneration is an eye disease with onset at any age, usually after age
60, that progressively destroys the macula, the central portion of the retina
that helps with focus. It rarely causes total blindness as only the center of
vision is affected.
There are two
types of AMD: wet and dry. In wet AMD, abnormal blood vessels behind the retina
start to grow, leaking blood and fluid, causing loss of central vision, which
may occur quickly. In dry AMD, the light-sensitive cells in the macula slowly
break down causing central vision to diminish over time.
Retinal Detachment
Retinal
detachment occurs when the retina (tissue in the back of the eye) separates
(detaches) from its underlying structures. The buildup of fluid behind the
retina is what separates the retina from the back of the eye. Retina
detachments are often painless, and symptoms that may be noticed include
perception of flashing lights, floaters, or a curtain drawn over your visual
field. Risk factors for retinal detachment include being a nearsighted adult
age 25 to 50, or an elderly person after cataract surgery. Treatment for a
detached retina involves surgery, mostly using lasers, that can improve vision
affected by the retinal detachment.
Conjunctivitis (Pink Eye)
Conjunctivitis,
or pinkeye, is redness and inflammation of the clear tissue covering the eye
and the inside of the eyelids (conjunctiva). It is commonly caused by bacterial
or viral infections but may also be due to irritants (chemicals, pollutants, or
allergens).
Most cases of
infectious conjunctivitis are viral and do not need treatment with antibiotics.
Bacterial conjunctivitis can be treated with antibiotic drops or ointments
prescribed by your doctor. A crusty discharge may make it difficult to open the
eyelids. If this happens a warm, wet compress may be applied to the eyes to
gently remove the crusting.
To reduce the
spread of the infectious conjunctivitis, wash hands frequently, do not share
eye drops, cosmetics, towels, or washcloths.
Uveitis
Uveitis is
inflammation to the middle layers of the eye (the uvea). The uvea is the layer
of the eye that contains the arteries and veins that feed the important
structures used in vision. Causes of uveitis include trauma or injury to the
eye, infections, or rheumatologic or inflammatory diseases that affect other
parts of the body. The main symptom of uveitis is pain in the eyeball. The eye
will look red (bloodshot) and you may notice blurred vision, light sensitivity,
and spots in your vision.
Treatment for
uveitis depends on the cause. Anti-inflammatory or antibiotic drops, along with
pain medications may be prescribed.
Eye Allergies
Severe eye
allergies may cause damage to the eye that may threaten eyesight. Allergies can
cause chronic inflammation that may permanently damage the cornea. Causes of
eye allergies are usually due to seasonal allergies, sensitivities to cosmetics
or medications, or dust. Over-the-counter eye drops that contain antihistamines
or decongestants are usually helpful. Consult a doctor if OTC remedies do not
work, or if you experience pain, discharge, or extreme eye redness.
Sty (Stye)
A sty (also
spelled stye) is an infection of the oil gland at the base of an eyelash. It
appears as a red, raised pimple on the edge of the eyelid. Symptoms of a sty
are pain, tenderness, redness, and swelling with a small pustule. The eyeball
itself may feel irritated or as if something is scratching it due to the
swelling of the eyelid. Treatment for a sty includes warm compresses applied to
the affected area for 10 minutes, up to six times daily. If the sty comes to a
head and releases pus, it should be cleaned gently with soap and water. This
rupture usually leads to the sty going away. If the sty is very large, painful,
or affects your vision, see your doctor.
Keratoconus
The cornea is
the clear surface covering the front of the eye. It is normally smooth and
round, following the contour of the eyeball. Weakness in the structure of the
cornea can lead to pressure in the eyeball, causing an conical-shaped abnormal
bulge to the front of the eye in a condition called keratoconus. Changes in the
shape of the cornea make it difficult for the eye to focus even with the help
of glasses or contact lenses. Keratoconus can also cause complications during
certain eye surgeries. Treatment includes rigid contact lenses or corneal
transplantation.
Blepharitis
Blepharitis is
inflammation of the eyelids. The inflammation can be found on the outer
(anterior) or inner (posterior) eyelid and symptoms include burning, itching,
swelling, flaky skin at the base of the lashes, crusting of the eyelids,
tearing, or blurred vision. Common causes of blepharitis are problems with oil
glands at the base of the eyelids, infections, or other skin conditions.
Treatment includes good eyelid hygiene, including frequent cleaning, light
scrubbing, using a mixture of water and baby shampoo. Severe cases of
blepharitis may require antibiotics or steroids.
Chalazion (Eyelid Cyst)
A chalazion
(also called a meibomian cyst, tarsal cyst, or conjunctival granuloma) is the
inflammation of a small cystic gland in the eyelid. The gland opening becomes
clogged and the gland swells. Chalazia are treated with warm compresses, though
in rare cases they may require antibiotics. If the chalazion becomes severe,
causes changes in vision, or is persistent, it may be removed surgically.
Corneal Ulcer
A corneal ulcer
is a small crater (ulcer) on the front part of the eye, usually resulting from
infection. Bacteria, viruses, or fungus can cause a corneal ulcer. People who
wear contact lenses are at higher risk for corneal ulcers because infectious
agents may get trapped behind a lens. Symptoms of a corneal ulcer include pain,
intense redness, feeling as if the eye is scratched or something is in the eye,
sensitivity to light, and blurry vision. If you suspect a corneal ulcer or have
the symptoms of a corneal ulcer and wear contact lenses, see your
ophthalmologist immediately. High potency antibiotics and pain medications are
the treatments for this condition.
Diabetic Retinopathy
People with diabetes
often have problems with their blood vessels throughout their bodies and the
eye is no exception. A complication of diabetes is diabetic retinopathy, which
affects the blood vessels in the back of the eye, on the retina.
There are two types of
diabetic retinopathy:
·
Nonproliferative
retinopathy, the less severe type in which there may be bleeding in the retina
and leakage of blood or serum causing a "wet retina."
·
Proliferative
retinopathy, a more severe type where new abnormal blood vessels grow on the
retina. These vessels may bleed into the vitreous (the clear jelly in the
center of the eye) and cause visual problems.
Treatment involves laser
surgery but damage may be permanent. The best way to prevent diabetic
retinopathy is with strict glucose control and a healthy lifestyle (weight
loss, dietary restrictions, and exercise).
Strabismus (Crossed Eyes)
Crossed eyes
(strabismus) is a condition where the eyes do not look in the same direction as
they should. One eye may track differently than the other causing a disjointed
appearance. Young children born with this disorder may develop decreased vision
in one eye (amblyopia). Treatment for strabismus involves using an eye patch on
the stronger eye, eye exercises, and possibly surgery.
Floaters
Floaters are
caused by aging changes in the vitreous jelly of the eye. They are a common
consequence of aging. If you develop multiple floaters, or floaters associated
with pain, get checked by your ophthalmologist. In general floaters do not
cause blindness and are mostly harmless. There is no definitive treatment for
floaters, as most will fade or become less noticeable over time.
Farsightedness (Hyperopia)
Farsightedness
(hyperopia) is difficulty focusing on objects that are close. It is very common
and the incidence increases with age. It is caused by an abnormally flat cornea
that does not allow light to sharply focus on the retina. Glasses, contact
lenses, or surgery may be used to correct hyperopia.
Nearsightedness (Myopia)
Nearsightedness
(myopia) causes people to be unable to see distant objects, though they can see
nearby objects clearly. It is caused by the cornea having too much curvature,
resulting in problems with focusing on the retina. Myopia is extremely common
and easily corrected with eyeglasses, contact lenses, or surgery.
Astigmatism
Another common
cause of visual difficulty is astigmatism, in which images are blurred due to
an irregularly-shaped cornea. Astigmatism will eventually affect most people as
a part of the aging process. It is treated with glasses, contact lenses, or
refractive laser eye surgery.
Color Blindness
The colors we
see are a result of how our eyes (and thus our brains) interpret different
wavelengths of light. People with color blindness have difficulty seeing
certain colors, usually reds, greens, and blues. Color blindness is caused by
an absence or malfunction of color-sensitive cells located in the retina. Most
of the time this is genetic (people are born with it) but it can also be caused
by aging, disease, trauma to the eye, or certain medications. If the cause of
the color blindness is genetic, the problem cannot be corrected but people may
be trained to adapt to interpret color shades. In cases where color blindness
is acquired, it may be treatable.
Proactive Eye Health
Take care of
your eyes to protect your vision. Always use eye protection to avoid injuries
and wear sunglasses to protect your eyes from UV rays. People over 40 should
have their eyes checked every two years and people over 60 should have their
eyes checked every year.
Be proactive in
your eye health. If you notice any symptoms of the disorders discussed in this
slide show, see your ophthalmologist.
Reviewed by William Baer, MD on Tuesday,
June 21, 2016
Common Eye Problems and
Infections
This tool does not
provide medical advice.
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