rheumatoid arthritis Chronic, autoimmune, inflammatory disorder that mainly affects the joints. Symptoms include pain,
stiffness, swelling and deformities. Rheumatoid arthritis may also cause eye burning, discharge and dryness. It can be associated with uveitis.
river blindness Onchocerciasis is caused by a parasitic worm, which is spread
in the human bloodstream through bites from blackflies and buffalo gnats found in parts of Africa, South America, and Central America.
The worm's offspring cause inflammation, bleeding, and other problems in the eye.
Without a 15-year regimen of annual doses of Mectizan, blindness will result.
(Information supplied by ORBIS International.)
RK (Radial Keratotomy) Surgical procedure where cuts are made in the cornea in a radial pattern, to flatten the cornea and correct myopia. However, RK now is virtually obsolete as a corrective eye procedure.
rod A photosensitive receptor in the retina that helps you to see in low light.
rosacea Skin condition typically involving the face that is characterized by flushing, red bumps and telangiectasia (dilated, visible capillaries); it is most common among fair-skinned women,
who develop it in their 30s through 50s.
sarcoidosis Disease in which granulomas (nodules of inflamed tissue) form in the lymph nodes, lungs, skin and other areas.
The cause is unknown. Symptoms include fatigue, weight loss, fever, coughing, uveitis, cranial nerve palsies and skin lesions. Some patients also develop dry eyes.
sclera The outer coat of the eyeball that forms the visible white of the eye and surrounds the optic nerve at the back of the eyeball.
scleritis Inflammation of the sclera. Autoimmune disorders are the most common cause. Symptoms
include a red or pink eye, eye pain, light sensitivity, tearing and blurred vision.
scotoma Blind spot within the field of view.
seborrheic dermatitis Skin condition that causes scales, redness and itching; it commonly affects the scalp (dandruff), eyebrows, eyelids, nose, area behind the ears and sternum. It is associated with seborrheic blepharitis.
segment A part, as in the near-vision portion of a pair of bifocals.
silicone Type of flexible and comfortable plastic. Because it is commonly used in nose pads in eyeglasses, people who are allergic to silicone should ask their eye doctor for a different type of nose pad.
sinusitis Inflammation of the sinuses, due to an infection or an allergic reaction. Probably the most common cause of
pain in and around the eye. Symptoms include head pain (headache, pain around the eyes, toothache, jaw pain), nasal discharge,
postnasal drip, coughing, eyelid swelling, swelling around the eyes, a stuffy nose, fatigue,
bad breath and a sore throat.
Sjogren's syndrome An inflammatory autoimmune disorder characterized by a dry mouth and dry eyes. Additional eye symptoms
include burning, discharge, foreign body sensation, itching and light sensitivity.
skin cancer Skin cancer is commonly caused by exposure to the sun's UV rays. Types include basal-cell carcinoma,
squamous cell carcinoma and malignant melanoma. In carcinoma, you are likely to have a red or pink bump that bleeds, crusts and scales.
In melanoma, the pigmented areas can be raised or flat; they are often brown or black, but can be (or include) other colors as well,
such as blue, red, pink or white. Some raised moles are skin-colored. The most common symptoms of a malignant mole follow an ABCD checklist:
- Asymmetry: one half does not match the other.
- Border: irregular or scalloped.
- Color: varies in shade or color.
- Diameter: larger than that of a pencil eraser.
Snellen chart Standard chart with letters,
numbers, or symbols printed in rows of decreasing size used by eye care professionals
in distance visual acuity testing.
The chart was invented by Dutch ophthalmologist Hermann Snellen.
soft contact lenses Contacts made of gel-like plastic containing varying amounts of water.
solution Product used to clean, disinfect and store contact lenses.
SPF (sun protection factor) Number representing the amount of sun something blocks. For example, if you normally begin to burn after half an hour in the sun, a sunscreen with an SPF of 2 should let you stay out twice as long (1 hour), SPF 4 should let you stay out four times as long, and so on.
spherical A contact lens design that is like a sphere and is fairly common; in contrast, toric lenses for astigmatism are football-shaped and are less common.
spots Small, cloudy specks in the eye that become noticeable when they fall in the line of sight. Read
our spots and floaters article.
spring hinge Type of hinge on eyeglass frames that is more flexible
than a regular hinge, making the frames more durable.
stereopsis Three-dimensional vision, enabling depth perception.
strabismus A misalignment of the eyes: the eye
don't point at the same object together. Crossed eyes (esotropia) are one type of strabismus; "wall-eyes" (exotropia)
are another. The exact cause is unknown, but appears to be a problem with the eye
muscles. Strabismus can affect depth perception.
stroke An interruption in blood flow to the
brain, resulting in tissue death. Blood clots and other obstructions can
interrupt the blood flow, as can a ruptured artery. Symptoms include weakness or
numbness, particularly on one side of the body, a change in consciousness or mental status, vision loss,
double vision, and limited eye
movement. You may also blink frequently.
stroma The cornea's middle layer; it consists of lamellae (collagen) and cells, and makes up most of the cornea.
sty A small red bump on the edge of the eyelid
caused by an infected gland. Additional symptoms include eyelid pain, eyelid
swelling, eye pain or discomfort, foreign body sensation, light sensitivity and tearing.
subconjunctival hemorrhage Bleeding from
blood vessels on the surface of the eye that leaves a red patch. This common problem can be
caused by sneezing, coughing, high blood pressure, trauma and more.
surgery complication Complications from
cataract surgery, LASIK or other eye surgeries can result in a variety of
symptoms, including blurred vision, ptosis, foreign body sensation,
halos around lights, light sensitivity, eye pain or discomfort, red or
pink eyes, vision loss and an iris defect.
suspensory ligament Also called zonule of Zinn. Membrane of fibers (zonules) that holds the eye's lens in place.
Tay-Sachs disease Hereditary disorder
resulting from a deficiency of the enzyme hexosaminidase. Symptoms include blindness, delayed development, seizures and paralysis. Tay-Sachs disease often
results in an early death.
temple The "arm" of a pair of glasses, running from the ear to the lens area.
titanium A type of metal alloy that is very strong. Eyeglasses made of titanium are lightweight, durable and often hypoallergenic.
tonic pupil Dilated pupil that reacts sluggishly
to light, due to damage to the ciliary ganglion from trauma, viral infections or
other causes. The cause is sometimes unknown ("Adie's tonic pupil").
toric A lens design with two different optical powers at right angles to each other for the correction of astigmatism.
toxocariasis Infection caused by Toxocara
worms, which are typically found in cat and dog intestines. The form found in
the eyes, ocular larva migrans, can cause vision loss.
trabecular meshwork Porous, spongy tissue within the eye, through which fluids pass.
trachoma Chronic infection of the eyelid and cornea caused by a micro-organism that is spread by contact
with eye discharge from an infected sufferer. Flies can also transmit the bacteria. Over time,
the eyelid becomes scarred and turns inward. The eyelashes begin to scrape the eyeball and cornea, which
eventually causes visual impairment and blindness. Worldwide, 84 million people are affected by trachoma. Clean water and
good hygiene can prevent trachoma, while antibiotics can treat it early on. Inward-turning eyelids can be corrected with
simple surgery performed by a nurse. (Information supplied by ORBIS International.)
trauma Injury, such as from being
poked in the eye or hit in the head. Depending on the type of trauma, symptoms can include blurred
vision, a bulging eye, burning, double vision, dry eyes, floaters,
light sensitivity, pain or discomfort of the eye or around the eye, swelling, a pupil that is dilated or unresponsive to light, vision loss,
limited eye or lid movement, ptosis, an iris defect and an eyelid cleft.
trichiasis Condition in which the eyelashes grow inwardly (towards the eye).
trichotillomania Disorder characterized by compulsive hair or eyelash pulling. The exact cause is not known.
trifocal A lens design that has three focal areas: a lens for close work or reading, a lens for mid-distance viewing or arm's length, and a lens for faraway viewing or driving.
20/20 vision Many eyecare practitioners consider this the average visual acuity for human beings, but humans can see as well as 20/15 or even 20/10. People with 20/40 vision can see clearly at 20 feet what people with 20/20 vision can see clearly at 40 feet. In most of the United States, 20/40 is the lowest uncorrected acuity required for a driver's license.
ultraviolet (UV) The invisible part of the light spectrum whose rays have wavelengths shorter than the violet end of the visible spectrum and longer than X rays. UVA and UVB light are harmful to your eyes and skin.
uvea Middle layer of the eye, below the limbus, and consisting of the iris, ciliary body and choroid.
uveitis Inflammation of the uvea. In most
cases, the cause is unknown, but infectious or immunological systemic disorders
can cause uveitis. Symptoms vary depending on where in the uvea the inflammation
occurs; they include mild to strong eye pain, redness, light sensitivity,
blurred vision and floaters. You may also experience
tearing, a pupil that responds poorly to light or squinting. Specific types of
uveitis include iritis, iridocyclitis, cyclitis, pars planitis and choroiditis. Read our uveitis article.
vascular birthmark A pink, red or purple mark
(flat or slightly raised), typically on an infant's face or neck, caused by a
malformation of blood vessels. Types of vascular birthmarks include capillary hemangiomas ("stork bites" or "angel's kisses") and
port-wine stains.
vascular problem Problems with your body's
vascular system (i.e., blood vessels, arteries and so on) can include hardening
of the arteries, high blood pressure, a clot, an aneurysm, an embolus, etc.
These problems can sometimes affect the eyes, resulting in such symptoms as
blurred vision, a bulging eye, double vision, eye pain or discomfort, a red or
pink eye, eyelid swelling and vision loss.
vector In gene therapy, an agent such as a modified virus used to carry and transport genetic material that is then transferred into recipient cells in an organism.
vergence disorder Vergence refers to the eyes'
ability to turn either inward (convergence) or outward (divergence); convergence
insufficiency is the most common vergence disorder. The disorders' exact causes
are unknown. Symptoms include double vision, eyestrain, fatigue, headache,
squinting and difficulty concentrating (particularly while reading).
visual acuity Sharpness of vision, usually as measured with the use of a
Snellen chart. 20/20 is considered normal visual acuity,
though some people can see even better (such as 20/15 or 20/10).
vitreous body Part of the eye between the lens and the retina, containing a clear jelly called the vitreous humor.
vitreous detachment Separation of the vitreous
from the retina, caused by age-related vitreous shrinkage. Floaters
are the typical symptom, but some people experience flashes of light as the
vitreous tugs or causes traction on the retina prior to complete separation. Read our spots and floaters article.
vitreous hemorrhage Bleeding that goes into the vitreous from nearby parts of the eye, such as from leaking
retinal blood vessels. Causes include diabetic retinopathy, trauma, a retinal tear or detachment, vitreous detachment
and retinal vascular occlusion (blockage in the retina's vascular system). Symptoms include sudden blurring or loss of
vision, and new floaters.
wavefront Describes technology used to "map" how the eye processes images,
enabling correction through surgery or lenses for obscure vision errors.
wear schedule How long you wear your contact lenses: either daily wear (you remove the lenses each night) or extended wear (you may sleep with them in). It's important to differentiate between wear schedule and replacement schedule — that is, how often you discard and replace your lenses.
white dot syndrome One of a group of inflammatory
conditions that are characterized by white dots in the retina and choroid. You
may also hear these syndromes called by their specific names, such as acute
posterior multifocal placoid pigment epitheliopathy, multiple evanescent white
dot syndrome, birdshot chorioretinopathy or multifocal choroiditis and
panuveitis. In some cases, the cause is unknown; in others, it's believed to be
an autoimmune disorder. Symptoms can include blurred vision, loss of color
vision, floaters, light sensitivity, metamorphopsia
and vision loss.
wraparound (wrap) Type of eyeglass
frame that curves around the head, from the front to the side. Wraparound
sunglasses tend to offer extra sun protection because the lenses usually wrap
as well.
xanthelasma A yellow, fatty spot or bump on
the inner corner of either the upper eyelid, the lower one or both eyelids, often caused by a lipid disorder such as high cholesterol.
zeaxanthin A pigmented substance (carotenoid)
found in yellow or orange plants, such as corn and squash, or in dark green, leafy vegetables. Zeaxanthin is being investigated
for a possible association with promoting healthy vision. [Read more about zeaxanthin.]
zyl Zylonite, or cellulose acetate, is a lightweight plastic often used in eyeglass frames.
It often appears in laminated form, with layers in different colors, but it can also be made in
mottled patterns to imitate natural tortoise shell or animal skins.
More about eyeglass frame materials.
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Cataracts
