Anatomy of the Eye
The eye is made up of numerous components. As you proceed through
the slideshow, you may use this illustration to reference the main
structure and anatomy of the eye.
- Cornea: clear front window of the eye that transmits and focuses light into the eye
- Iris: colored part of the eye that helps regulate the amount of light that enters
- Pupil: dark aperture in the iris that allows light to go through into the back of the eye
- Lens: transparent structure inside the eye that focuses light rays onto the retina
- Retina: nerve layer that lines the back of the eye, senses light,
undergoes complex chemical changes, and creates electrical impulses
that travel through the optic nerve to the brain
- Macula: small central area in the retina that contains special light-sensitive cells and 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
Glaucoma
Glaucoma (the sneak thief of sight) refers to a group of eye
diseases that affect the optic nerve and may cause vision loss. Optic
nerve damage in glaucoma is primarily due to elevated intra-ocular
pressure (IOP) within the eye. Glaucoma is classified either as
open-angle (the more common chronic condition which is usually painless)
or angle-closure glaucoma (the more unusual type which often occurs
suddenly [acutely] and is associated with pain and redness of the eye).
The elderly, African-Americans, and people with family histories of the
disease are at greatest risk. There are no symptoms in the early
stages, and by the time the patient notices vision changes, visual loss
due to glaucoma can only be halted, not reversed. Glaucoma is usually
treated with eyedrops, although lasers and surgery can also be used.
Most cases can be controlled well with these treatments, thereby
preventing further loss of vision. Early diagnosis and treatment is the
key to preserving sight in people with glaucoma.
Cataracts
Cataract is a painless condition where the normally clear
aspirin-sized lens of the eye starts to become cloudy. The result is
much like smearing grease over the lens of a camera, which impairs
normal vision. Causes of cataracts include cortisone medication, trauma,
diabetes, and aging. In fact, cataracts will affect most people if
they live long enough. Diagnosis can be made when a doctor examines the
eyes with a viewing instrument. Symptoms of early cataracts may be
improved with new eyeglasses, brighter lighting, antiglare sunglasses,
or magnifying lenses. If these measures do not help, surgically removing
the cloudy lens and replacing it with an artificial lens is the only
effective treatment. Removal is only necessary when vision loss
interferes with your everyday activities, such as driving, reading, or
watching TV. You and your eye-care professional can discuss the surgery,
and once you understand the benefits and risks, you can make an
informed decision about whether cataract surgery is right for you. In
most cases, delaying cataract surgery will not cause long-term damage to
your eye or make the surgery more difficult.
Age-Related Macular Degeneration (AMD)
Age-related macular degeneration is an eye disease with onset
usually after age 60 that progressively destroys the macula, the central
portion of the retina, impairing central vision. It rarely causes
blindness because only the center of vision is affected. There are two
types of AMD -- wet and dry -- neither of which causes pain. In wet AMD,
abnormal blood vessels behind the retina start to grow under the macula
and leak blood and fluid, causing loss of central vision, which may
occur quickly. Treatment includes laser surgery, photodynamic therapy,
and injections into the eye. None of these will cure the disease and
loss of vision may still progress. In dry AMD, the light-sensitive cells
in the macula slowly break down, causing central vision to diminish
over time. Early stages of dry AMD can be treated with high-dose
formulations of antioxidants and zinc, which may delay and possibly
prevent AMD from progressing to a more advanced stage. Once in the
advanced stage, no form of treatment canrestore vision loss.
Retinal Detachment
A retinal detachment is a separation of the retina from its
attachments to its underlying tissue within the eye. Most retinal
detachments are a result of a retinal break, hole, or tear. Once the
retina has torn, liquid from the vitreous gel (clear gel that fills most
of the inside of the eye) passes through the tear and accumulates
behind the retina. The buildup of fluid behind the retina is what
separates (detaches) the retina from the back of the eye. Flashing
lights, floaters, or a curtain may be the initial symptoms of a retinal
detachment or of a retinal tear that precedes the detachment itself.
Retinal detachments can occur at any age but occur most commonly in
younger adults (age 25 to 50) who are highly nearsighted and in older
people following cataract surgery. Surgical repair of a retinal
detachment is usually successful in reattaching the retina, although
more than one procedure may be necessary. Once the retina is reattached,
vision usually improves and then stabilizes.
Bacterial Conjunctivitis (Pink Eye)
Pinkeye, or conjunctivitis, is redness and inflammation of the
membranes (conjunctiva) covering the whites of the eyes and the
membranes on the inner part of the eyelids. The term pinkeye is most
commonly used to refer to the infectious (viral or bacterial) type of
conjunctivitis, but it may also result from allergic reactions or
chemical irritants such as air pollution, smoke, or noxious fumes. The
infectious form is very common in children and is highly contagious.
Children and adults who develop infectious pinkeye should see a doctor
to determine whether antibiotic treatment is necessary. Most infectious
cases are caused by viruses and will not respond to antibiotics. In
these instances, the discharge from the eye is clear and watery and
symptoms of a cold may be present. Viral infections last from seven to
10 days. Bacterial pinkeye generally results in a large amount of
discharge that is green to yellow in color. This discharge can
accumulate at night and make opening the eye difficult in the morning.
Bacterial pinkeye usually lasts three to five days and requires
antibiotic eyedrops to help the body remove the bacterial infection.
Application of warm washcloths to the eye area is also effective in
removing discharge. To reduce the chance of spreading infectious
pinkeye, those affected should avoid touching the eye area and wash
their hands frequently, particularly before applying medications to the
eye area. Sharing of towels, washcloths, cosmetics, or eyedrops can also
spread the infection.
Uveitis
Uveitis (pronounced you-vee-EYE-tis) is defined as all inflammatory
processes of the middle layers of the eye, also called the uveal tract
or uvea. The uvea is very important because its many veins and arteries
transport blood to the parts of the eye that are critical for vision.
Symptoms and signs of uveitis may include eye redness and irritation,
blurred vision, eye pain, increased sensitivity to light, and floating
spots. Potential causes include infection with a virus, fungus,
bacteria or parasite, inflammatory disease affecting other parts of the
body, or injury to the eye. Because uveitis is serious, treatment needs
to begin right away. For uveitis not caused by an infection, your
ophthalmologist may prescribe eyedrops containing steroids to reduce
swelling and drugs to relieve pain. Antibiotics are used in patients
with infectious uveitis. Dark glasses will help with light sensitivity.
Eye Allergies
Severe allergic eye symptoms can be very distressing and are a
common reason for visits to the allergist or ophthalmologist.
Occasionally, severe eye allergies cause serious damage that can
threaten eyesight. Eye allergies usually are associated with other
allergic conditions, particularly hay fever (allergic rhinitis) and
atopic eczema (dermatitis). Medications and cosmetics can also play a
significant role in causing eye allergies. Most people with eye
allergies treat themselves and do so quite effectively with OTC products
such as eye drops as well as antihistamines and decongestants. If these
remedies don't work or if there is eye pain, extreme redness, or heavy
discharge, you should seek medical advice.
Sty (Stye)
A sty (sometimes spelled stye) is a tender, painful red bump
located at the base of an eyelash or inside the eyelid. A sty results
from an acute infection of the oil glands of the eyelid that occurs
after these glands have become clogged. A sty also may arise from an
infected hair follicle at the base of an eyelash. Symptoms include
redness, tenderness, and pain in the affected area. The eye may feel
irritated or "scratchy." Later symptoms can include swelling, discomfort
during blinking, watering of the eye, and light sensitivity. A common
sign of a sty is a small, yellowish spot at the center of the bump that
develops as pus expands in the area. People of all ages and both genders
can develop a sty. Application of a warm compress or washcloth to the
affected area for 10 minutes, four to six times a day, can speed rupture
of the sty and aid in the relief of symptoms. A sty should not be
pressed or squeezed to facilitate drainage. If a sty persists for
several days, a doctor may lance (drain) the infection under local
anesthesia.
Keratoconus
We see through the cornea, which is the clear, central part of the
front surface of the eye. Normally, the cornea has a round shape, like a
Ping-Pong ball. Sometimes, however, the structure of the cornea is just
not strong enough to hold this round shape. The normal pressure inside
the eye makes the cornea bulge outward like a cone, causing distorted
vision. This condition is called keratoconus. Often the cause of
keratoconus is unknown. The disease usually does not cause blindness.
However, the changes to the cornea will make it impossible for the eye
to focus well even with glasses or soft contact lenses. Rigid contact
lenses or corneal transplantation may be necessary to provide good
vision.
Blepharitis
Blepharitis is an inflammation of the eyelids and occurs in two
forms, anterior (outside of the eyelid) and posterior (inner eyelid).
Both types of blepharitis can cause a burning or foreign body sensation,
excessive tearing, itching, sensitivity to light, red and swollen
eyelids, redness of the eye, blurred vision, frothy tears, dry eye,
flaking at the base of the lashes, or crusting of the eyelashes upon
awakening. Common causes for anterior blepharitis are bacteria (Staphylococcus)
and scalp dandruff while posterior forms are caused by problems with
the oil glands in the eyelid. Treatment for both forms involves keeping
eyelids clean and free of crusts. Warm compresses should be applied to
loosen crusts, followed by a light scrubbing with a cotton swab and a
mixture of water and baby shampoo. Because blepharitis rarely goes away
completely, most patients must maintain an eyelid hygiene routine for
life. If the blepharitis is severe, an eye-care professional may also
prescribe antibiotics or steroid eyedrops.
Chalazion (Eyelid Cyst)
A chalazion is a tiny lump of the upper or lower eyelid caused by
inflammation of a gland of the lid. It may be soft and fluid-filled or
firmer. A chalazion is also referred to as a meibomian cyst, tarsal
cyst, or conjunctival granuloma. The narrow opening through which a
meibomian gland secretes its material can become clogged from narrowing
of the opening or hardening of the sebaceous liquid near the opening. If
this occurs, the gland will have a backup of the material it secretes
and it will swell. Most chalazions are treated with warm compresses to
the eyelid to promote healing and circulation of blood to the inflamed
area. Doctors may prescribe an antibiotic drop or ointment to be used
immediately after the compresses. If the chalazion persists and is
causing an unsightly lump, it can be removed surgically through the
inside of the lid. 
Corneal Ulcer
Most corneal ulcers are caused by infections and can be bacterial
(common in people who wear contact lenses), viral (herpes simplex virus
and varicella virus), or fungal (improper care of contact lenses or
overuse of eyedrops that contain steroids). Symptoms include red eyes,
pain, feeling like something is in the eye, tearing, pus/thick
discharge, blurry vision, pain from bright lights, swollen eyelids, or a
white or gray round spot on the cornea. Self-treatment consists of
removing contact lenses, applying a cool compress to the affected eye,
washing hands often, and OTC pain medications such as Tylenol or Motrin.
Anyone with a corneal ulcer should be seen immediately by an
ophthalmologist, who will do testing and most likely prescribe
antibiotic and other eyedrops. If the ulcer persists or worsens, a
surgical procedure known as corneal transplantation may be performed.
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