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- Bardet-Biedl Syndrome
- A genetic disorder characterized by degeneration of the light sensitive cells in the
periphery of the retina causing night blindness, tunnel vision, decreased visual acuity, and
photophobia. Other conditions include obesity, developmental delays, spastic paraplegia
and renal disorders.
- basal cell carcinoma
- A type of skin cancer in which the cancer cells look like the basal cells of the skin.
- Basil cell nevus syndrome
- An inherited group of multiple defects that result in an unusual facial appearance and a
predisposition for skin cancer. The disorder affects the eyes as well as the skin, nervous
system, endocrine glands and bones. Children with the disease have wide-set eyes, a
broad nose and heavy protruding brow. The disorder results in the appearance of skin
cancers, particularly around the cheekbones, upper lip and eyes.
- Batten Disease
- A group of inherited neurological disorders that affect children and are marked by
progressive vision failure and other disorders that affect the brain. Most prominent in
families of Northern European-Scandinavian ancestry.
- Bell’s Palsy and the eye
- Paralysis of muscles controlled by the facial cranial nerve. Eyelid on affected side does not
close properly, so corneal drying may become a problem.
- bifocals
- Eyeglasses incorporating two different powers in each lens, usually for near and distance
vision corrections.
See Prescription Eyewear in Eye Care Encyclopedia.
See General Eye Care in Free Eye Tests.
- Bifocal lens
- Vision correction lens that comprises two parts: the upper part for distance vision and the lower part for near-vision tasks such as reading. The distance vision correction can have no correction at all. The segment for near-vision correction can be a half-moon shape, round, rectangular, or the bottom half of the lens.
See Prescription Eyewear in Eye Care Encyclopedia.
- binocular vision
- The ability to maintain visual focus on an object with both eyes, creating a single visual image. Lack of binocular vision is normal in infants. Adults without binocular vision experience distortions in depth perception and visual measurement of distance.
- bioluminescence
- The giving off of light from living organisms.
- blastoma
- Never used without “retino or “neuro” in front of it.
- blepharitis
- Common, persistent and sometimes chronic inflammation of the eyelids, resulting from
bacteria that reside on the skin. In certain individuals, these bacteria thrive in the skin at
the base of the eyelashes or even in the oil glands near the eyelid, resulting in dandruff-like
scales and particles. Blepharitis is usually only a minor irritation.
- blepheroplasty
- Surgery to improve the appearance of the eyelids. In addition to detracting from overall
appearance, drooping eyelids may cause functional problems such as impaired field of
vision or difficulty wearing glasses. Blepharoplasty is usually outpatient surgery performed
by ophthalmic plastic and reconstructive surgeons.
See Plastic Surgery in Free Eye Tests.
- blepharospasm
- Condition characterized by uncontrollable, forcible closure of the eyelids caused by a
progressive dysfunction of the nerve that controls muscles around the eye. Less serious
form may cause eyelid twitches or tics.
- blindness
- Inability to see. Legal blindness is corrected visual acuity of 20/200 or less, or corrected
visual field to 20 degrees or less, in the better seeing eye.
See Low Vision in Eye Care Encyclopedia.
See General Eye Care in Free Eye Tests.
- blind spot
- 1. A small area of the retina where the optic nerve enters the eye, this type of blind spot occurs normally in all eyes. Also called optic disk. 2. Any gap in the visual field corresponding to an area of the retina where no visual cells are present; this type of blind spot is associated with eye disease.
- blindsight
- A phenomenon reported in individuals who have damage to the primary visual cortex resulting in blindness. Individuals with blindsight report that they are unable to see, yet when examined are able to indicate the presence and location of objects.
- botox
- Toxin produced by the same bacteria responsible for a type of food poisoning called
botulism. Injected in very small amounts into the eyelid muscles, botox has been found to
be effective in stopping uncontrollable eyelid spasms such as those found in
blepharospasm.
- Braille
- A system of raised-dot writing devised by Louis Braille (1809-1852).
Each braille character or "cell" is made up of 6 dot positions that are arranged in a rectangle comprising 2 columns of 3 dots each. A dot may be raised at any of the 6 positions, and each combination of raised dots corresponds to a letter of the alphabet, a punctuation mark, and another symbol.
- bridge
- The portion of the eyeglass frame which extends across the top of the nose. Because the
nose supports 90 percent of the weight of the glasses, a properly sized and adjusted bridge
is critical to the fit and comfort of the eyeglasses.
- B-Scan
- Ultrasound procedure in which high frequency waves are reflected by eye tissues and
orbital structures and then converted into electrical pulses which are displaced as bright
spots on a black background. Provides a cross-sectional view of tissues used for
evaluating structures that cannot be seen directly.
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