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- daily wear contact lens
- Contact lenses worn only during waking hours.
- depth perception
- The ability to judge how far away an object is as well as how far away objects are from each other.
- diabetes and your eyes
- Diabetes can cause many problems that result in changes to the eye. The most
common and serious diabetes-related disease is diabetic retinopathy, but diabetes
can also cause cataracts and affect the nerves that control eye alignment. The
disease can also cause the optic nerve to be more easily damaged by glaucoma.
Diabetics should be very careful about regulating their level of blood sugar to
protect themselves from serious eye problems.
See Diabetes and Your Eyes in the Eye Care Encyclopedia.
See Free Eye Tests.
- diabetic retinopathy
- Potentially serious complication of diabetes that results in the weakening of tiny
blood vessels that nourish the retina. These vessels may leak causing a variety of
complications including the formation of scar tissue on the retina, a decrease in
nourishment to the retina or blood in the vitreous humor (fluid that fills the inner
cavity of the eye) causing cloudy vision. If the condition is not caught and treated
during the early stages, it can result in blindness. For this reason, diabetics should
have regular and frequent eye examinations.
See Diabetes and Your Eyes in the Eye Care Encyclopedia.
See Free Eye Tests.
- diamond knife
- Surgical knife with a high-quality diamond edge often used in delicate eye surgery.
- diathermy
- The use of heat to destroy abnormal cells. Also called cauterization or electrodiathermy.
- diet and nutrition
- A well-balanced diet is essential for overall good health and a variety of vitamins
and minerals are necessary for normal cell growth and repair. Eyes contain highly
specialized tissues, and studies show that a healthful diet rich in several specific
nutrients and vitamins helps maintain lifelong eyesight.
- diffraction
- The scattering of rays of light when they bump into an object or when they pass through air or water, or go by an edge or narrow opening. Plays a role when the pupil is small.
- diopter
- Unit that measures the degree of refractive error in an eye or the light-bending
power of a lens. In an eyeglass or contact lens prescription, a negative number
refers to nearsightedness, while a positive number refers to farsightedness. For
instance, a –8.00 diopter lens is very nearsighted, while a +0.75 is slightly
farsighted. Astigmatism can be measured as either a positive (+) or a negative (-)
but will be accompanied by another number such as “@ 90” indicating the
direction (axis) of the astigmatism.
- diplopia
- The condition whereby a single object appears as two objects. Occurs because the eye muscles do not act equally. Also called double vision.
- disposable contact lens
- Contact lenses intended to be worn for a certain time period – daily, weekly, biweekly,
monthly – and then discarded. Among most eye doctors, “disposable” usage ranges from
one day to two weeks, while “frequent replacement” lenses are thrown away monthly or
quarterly. (index to contact lens: disposables)
- drooping eyelids
- Condition (usually hereditary) in which the upper eyelid(s) sag. May be
congenital or caused by a later problem associated with a nonfunctioning levator
muscle.
See Free Eye Tests.
- druse
- drusen, plural
- Tiny yellow or white deposits in the retina of the eye or on the optic nerve head, visible to an eye care specialist during an eye examination. One of the most common early signs of age-related macular degeneration (ARMD). The presence of drusen alone does not indicate disease, but it may mean that the eye is at risk for developing more severe ARMD.
- dry eye
- Condition due to a deficiency in the production and/or composition of tears by the eye’s
lacrimal glands. Symptoms are redness, swelling and irritation, often accompanied by
excessive watering of the affected eye. The condition is more common as the eye ages and
may be worsened by a dry climate, exposure to wind, smoke, smog, air conditioners and
ceiling fans. Most dry eye can be corrected by the use of artificial tear drops prescribed by
your eye doctor.
See Free Eye Tests.
- double vision
- The condition whereby a single object appears as two objects. Occurs because the eye muscles do not act equally. Also called diplopia.
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