eye chart test A test that measures vision ability at various distances. An eye chart is imprinted with block letters that line-by-line decrease in size, corresponding to the distance at which each line of letters is normally visible. See also chart, Snellen.
eyedrop test A test that involves putting certain liquids into the eye to produce a particular response. There are many types of eyedrops and many types of eyedrop tests. One of the most common eyedrop tests is pupil dilation. See also dilation, pupil.
eyelid The lid or cover of the eye, a movable fold of skin and muscle that can be closed over the eyeball or opened at will. Each eye has an upper and a lower lid. Also known as a palpebra.
eyelids, adult ptosis of the Drooping of the upper eyelids in adults, most commonly due to separation of the tendon of the lid-lifting (levator) muscle from the eyelid. This may occur with age, after cataract or other eye surgery, or due to an injury, an eye tumor, or a complication of another disease that involves…
eyelids, congenital ptosis of the Drooping of the upper eyelids at birth. Moderate or severe ptosis calls for surgical treatment to permit normal vision development. If moderate or severe ptosis is not corrected, amblyopia (“lazy eye”) may develop, which can lead to permanently poor vision. Congenital ptosis is often caused by poor development of the…
eyes, flashing lights in the Spontaneous flashing-light sensations in the eyes that can be caused by a number of factors. A sensation of flashing lights can be caused when the vitreous humor (the clear, jelly-like substance that fills the middle of the eye) shrinks and tugs on the retina. These flashes of light can appear…
eyes, spots in front of the The spontaneous appearance of spots in the eyes. Also known as “floaters,” spots are usually images formed by deposits of protein drifting about in the vitreous humor (the clear, jelly-like substance that fills the middle of the eye). The appearance of permanent or recurring white or black spots in…
F 1 Chemical symbol for the element flourine. 2 Abbreviation for Fahrenheit. 3 The symbol for the coefficient of inbreeding. See also coefficient of inbreeding.
Fabry disease A genetic disease caused by a mutation in the GLA gene, resulting in a deficiency of the enzyme alpha-galactosidase A, also known as ceramide trihexosidase. This enzyme is essential to the metabolism of a fat compound known as globotriaosylceramide. Without alpha-galactosidase A, this fatty substance accumulates in the walls of blood vessels, leading…
face, masklike An expressionless face with little or no sense of animation; a face that is more like a mask than a normal face. Masklike face is seen in a number of disorders, including Parkinson’s disease and myotonic dystrophy. Also known as masklike facies.
facelift A surgical procedure that is designed to make the face appear younger by pulling loose facial skin taut and tightening and repositioning the underlying facial musculature. Excessive skin and/or fat may be removed during the procedure. Supplemental procedures—including necklift, blepharoplasty (eyelid surgery), autologous fat injection, forehead lift, and browlift; chemical or laser peel; and…
facial canal introitus The entrance to the facial canal, a passage in the temporal bone of the skull through which the facial nerve (the seventh cranial nerve) travels. In anatomy, an introitus is an entrance that goes into a canal or hollow organ.