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- safety: eye
- Because eyesight is considered by many to be the most important of the five senses,
protecting the eye from hazards should be a priority. The most common eye hazards
include flying objects from grinding, sawing, hammering and other projectiles, such as BB
guns. Dusts, welding sparks, fumes and chemical splashes are also major hazards,
particularly in workplace situations. High intensity light rays from arc welding, acetylene
equipment and even from staring into the sun can cause painful burns and permanent
damage to the retina. Following established safety guidelines and using appropriate protective eyewear can prevent 90 percent of all eye injuries.
See Free Eye Tests.
- saturation
- The richness of hue. Indicates how much color has been diluted by grayness.
- sclera
- Tough outermost layer of the eye that is visible as the white of the eye.
See Free Eye Tests.
- scleral buckle
- Surgical procedure that repairs a retinal detachment by indenting, or buckling the sclera
inward, usually by sewing a piece of preserved sclera or silicone rubber to the scleral
surface. This pushes choroid and pigment epithelium closer to the retina and helps relax
the vitreous tug on the retinal surface.
See Free Eye Tests.
- scotoma
- Nonseeing area, or blind spot, within visual field, resulting from damage to visual pathways or to the retina. Blind spots exist normally in all eyes and mark the site of the optic nerve.
See Free Eye Tests.
- scotopic vision
- Dim light conditions where only rods are functional. Also called twilight vision.
- segment
- Term used in designating different areas of eye, as in “posterior segment” or “anterior
segment.”
See Free Eye Tests.
- selenium
- An essential mineral that is a component of a key antioxidant enzyme in tissue respiration. Deficiency of selenium causes disease of the heart muscle. Food sources of selenium include seafoods, kidney and liver, and some grains and seeds.
- Sjogren's syndrome
- sicca syndrome
- An inflammatory disease of glands and other tissues of the body that classically combines dry eyes, dry mouth, and another disease of the connective tissues such as rheumatoid arthritis, lupus, scleroderma, or polymyositis. About 90 percent of Sjogren syndrome patients are female, usually in middle age or older. Sjogren syndrome can be complicated by infections of the eyes, breathing passages, and mouth. Also called sicca syndrome
- slit lamp
- Microscope used in eye examination that projects a thin, intense beam of light into the eye
through a controlled diaphragm. Used in examination of interior eye segment from the
cornea epithelium to the posterior capsule. Aids in the diagnosis of diseases or trauma
which affect the structural properties of the anterior eye segment.
See General Eye Examination in Eye Care Encyclopedia.
See Free Eye Tests.
- Snellen acuity
- Visual acuity as measured by the Snellen Chart. A person with a normal optical system
(20/20 vision) can see standardized symbols on the chart at a distance of 20 feet. A person
with 20/30 vision can see symbols on the chart from 20 feet that a person with normal
vision could see from 30 feet.
See General Eye Examination, Visual Acuity in Eye Care Encyclopedia.
See Free Eye Tests.
- Snellen Eye Chart
- Test chart for assessing visual acuity. Rows of letters, numbers and symbols in standarized
graded sizes, with a designated distance at which each row should be legible to a normal
eye.
See Free Eye Tests.
- soft contact lens
- Made from flexible plastic, these lenses absorb water and thus enable greater amounts of
oxygen to pass through the lens to the cornea. Soft lenses are more comfortable for most
wearers than hard lenses, and most lenses prescribed today are a version of a soft lens.
They vary in design depending on the type of materials and required refractive correction.
See Free Eye Tests.
- solution
- Variety of solutions for caring for contact lenses, including cleaning, rinsing and
disinfecting. There are also multi-purpose solutions that provide all three functions.
Rewetting solutions are designed to lubricate the lenses while they are worn.
See Free Eye Tests.
- SPF
- Acronym for sun protection factor. Measures the length of time a sunscreen product
protects against skin reddening from UVB (short-wave solar waves) compared to how
long the skin takes to redden without protection. For example, if reddening takes 20
minutes without protection, using an SPF 15 suncreen theoretically prevents reddening 15
times longer.
See Free Eye Tests.
- spherical
- Single prescription contact lenses with smooth spherical surfaces that bend light rays
equally in all directions (360 degrees).
See Free Eye Tests.
- sports vision
- Growing specialty in many eye care offices, usually focusing on the safety aspects of
sports, but may also include vision therapy designed to strengthen eye coordination and/or
overcome congenital weaknesses. Sports safety usually includes ultra-violet and sun
protection, glare protection and safety from direct impact.
See Free Eye Tests.
- spots
- Particles that float in the vitreous, which is jelly-like substance that fills the center cavity of the eye, and cast shadows on the retina. Some spots are formed before birth while others
occur normally with aging. The sudden appearance of many spots can be an indication of a
serious eye disorder and should be checked by your eye doctor.
See Free Eye Tests.
- spring hinge
- Type of hinge on eyeglass temple that is more flexible and durable than a conventional hinge and
holds eyeglasses more tightly to the head.
See Free Eye Tests.
- squamous cell carcinoma
- Cancer that begins in squamous cells, which are thin, flat cells resembling fish scales. Squamous cells are found in the tissue that forms the surface of the skin, the lining of the hollow organs of the body, and the passages of the respiratory and digestive tracts.
- stereopsis
- Perception of depth, depending on the differences in the images projected on the retinas of the two eyes.
- stereoscope
- Device for creating a 3-D image of drawn objects. Works by projecting two different images of the objects to the eyes.
- strabismus
- Also known as crossed eyes. Visual defect in which the eyes are misaligned and point in different directions. Strabismus
usually occurs in childhood but can occur later in life. Children with crossed eyes usually
adapt when the brain learns to ignore the image of the misaligned eye, although they lose
depth perception. Adults who develop the problem often have double vision because the
brain is already trained to see two images.
- sty
- Inflammation of one or more sebaceous, or fluid-producing, glands of an eyelid.
See Free Eye Tests.
- Stiles-Crawford effect
- An optical phenomenon in which light passing through the center of the pupil is perceived as more intense than light passing through the periphery of the pupil.
- Summit laser
- One of two primary manufacturers of the Excimer laser used in refractive eye surgery.
See Free Eye Tests.
- sunglasses
- Eyeglasses that enhance the normal light-filtering capabilities of the eye and protect
against the sun’s damaging ultraviolet (UV) rays. Good sunglasses should be judged by
their ability to reduce glare, filter out 99 percent to 100 percent of UV rays, provide visual
protection, be comfortable and not distort colors.
See Free Eye Tests.
- superior
- In eye care terminology, referring to the upper half of the eye.
See Free Eye Tests.
- superior colliculus
- Part of the brain that constitutes a primitive center for vision. Also called optic lobe, optic tectum.
- surgicial vision correction
- Any of a number of surgical procedures that either alter the shape of the cornea to correct
refractive error, or involve the insertion of a device within the front (anterior) of the eye to
enhance the eye’s natural focusing ability.
See Refractive Surgery in Eye Care Encyclopedia.
See Free Eye Tests.
- sympathetic ophthalmia
- Inflammation of one eye following inflammation in the other eye.
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