General Terminology and Basic
Equipment
Please note: The information provided should be used as a reference guide.
20/20 pens or felt tip pens- Thin
tip markers. The 20/20 is a Standford brand that is used because it does not
bleed thru the paper.
Abacus- performs arithmetic
functions by manually sliding counters on rods or in grooves.
Accommodation -The eyes’ ability to adjust itself to see
things at different distances. This happens because the lens in the eye changes
shape allowing images to focus clearly on the retina.
Acuity- measurement of the sharpness of vision as it
relates to the ability to discriminate detail.
Add- This is the “bifocal” part of glasses. The add is
generally “added” to a persons’ distance prescription to help him focus better
for reading and other near tasks.
Amsler grid- A hand held card
featuring horizontal and vertical lines, usually white on black background, used
to test for central visual field defects.
Assistive technology- any item, piece of equipment, or
product system, whether acquired commercially off the shelf, modified, or
customized, that is used to increase, maintain, or improve functional
capabilities of individuals with disabilities.
Audio cassettes / Talking books- Many texts and novels are available on
audio cassette.
Best corrected visual acuity- The acuity that results from
the best possible refraction/lens correction.
Bifocals- The combination of two lenses into one. This is
generally done with the distance prescription at the top of the lens with
addition diopters of power at the bottom of the lens for reading and other near
tasks.
Binocular vision- The ability to use both eyes at the same
time to focus on the same object. The images of both eyes are fused into a
single image in the brain. This provides depth perception.
Blind, Blindness- A broad term meaning unable to see.
Total blindness specifically means no ability to see any light. Legal blindness
is a much broader term that includes vision loss ranging from total blindness to
having very usable residual vision. The definition of legal blindness in the
United States is: 1) central visual acuities of 20/200 or less in the better eye
after best correction; and/or a reduction of visual fields of 20 degrees -or
less in the better eye.
Braillers-
used for producing Braille. Perkins is a manual brailler. An embosser is an
electronic brailler.
Central visual acuity- The vision (acuity) measured from
the fovea and macula, “straight ahead vision”.
CF- count fingers
Closed circuit televisions- (CCTV)-
electronic magnification that produces the image onto a monitor- CCTVs are
available to each classroom at ISVI.
Contrast- the differences in a visual target and its
background.
Convergence- The process of having the eyes focus together
on a object held close to the them causing the eyes to turn inward towards the
nose, maintaining a single image of the object in the brain.
Correction- The wearing of glasses/lenses that correct
refractive errors in the eyes.
Depth perception- The ability to perceive the relative
positions of things in space.
Diopter- The unit of measurement used to indicate how much
light rays are refracted, or bent, by a lens.
Eccentric viewing- Ability in such a way that the
operative part of the retina is able to view, ie, turning the head or head tilt.
ENUC- enucleated
Eye dominance- When one eye tends to take over the major
function of seeing.
Floaters- Small particles of cells, fibers, etc., which
move around in the vitreous.
Focus- Bringing all light rays into a point by the use of
a lens. The cornea, lens, and fluids inside the eye work together to bring light
rays into focus on the retina with the lens doing the “fine focusing”.
Franklin Speller or Language Master-
A talking dictionary/thesaurus- gives definitions, spellings, and example in
sentences.
Fusion- The ability to combine the two images produced by
each eye into a single mental image.
Glare- An annoying sensation produced by too much light in
the visual field that can cause both discomfort and reduction in visual acuity.
Glasses- Bifocals and reading glasses should be worn for
all near activities- Distance glasses are usually worn full time unless
specified. Broken glasses should be sent to Low Vision Coordinator to be fixed
or the health center to send to LVC or optical to be repaired.
HM- hand motion
Intraocular pressure- The fluid pressure within the eye
created by the continual production and drainage of aqueous fluid in the
anterior chamber.
Learning media- an individual’s primary learning channel;
one or more of the primary senses that an individual uses most for learning; the
best and most efficient literacy medium.
Legal blindness- In the US, visual acuity of 20/200 or
worse in the better eye with corrective lenses OR visual field restricted to 20
degrees diameter or less in the better eye.
LP-Light perception- The ability to distinguish the
absence from the presence of light.
Light projection- The ability to determine the direction
of the source of light.
Low vision- A visual impairment after correction but with
potential for use of available vision, with or without optical or non-optical
compensatory visual strategies, devices, and environmental modifications, to
plan and perform daily tasks.
Magnifiers- increases the size of
the image- used for reading print, studying maps, viewing diagrams in
mathematics books- there are different powers,
Monocular- Using one eye.
Monocular telescopes are used for distance viewing to bring image closer to the
eye.
Motility- Eye movement controlled by the extra ocular
muscles.
Near point of accommodation- The closest point at which
the eye can still focus (accommodate) on an object clearly. The point varies
from person to person depending on age, refractive errors present, etc.
Near vision- The ability to see things clearly at a normal
reading distance (about 14 16 inches or 35 -40 centimeters) from the eye.
Night blindness- A condition where a person may be able to see with no problems
by day or in good illumination (light), but is unable to see at night or in
faint light. Can be caused by any eye condition that affects the rods.
NLP- No Light Perception- the total absence of vision.
Non-optical devices- devices or modifications that do not
involve optics, used to make visual information more accessible to individuals
with low vision, such as book stands, trays, positioning seating, modifications
of illumination, and large print when indicated.
Null point- Eye position or direction of gaze in which
oscillation is reduced.
Ocular- Having to do with the eye.
Ocular pursuit- The act of tracking a moving object in all
cardinal directions- vertical, horizontal, oblique, and circular.
OD- right eye
Ophthalmologist- A medical physician who specializes in
the medical and surgical care of the eyes and is qualified to prescribe ocular
medications, diagnoses eye conditions and to perform surgery on the eyes.
Ophthalmoscope- An instrument used in examining the interior of the eye.
Optic Nerve- It is the essential link between the eye and
brain. It carries impulses for vision from the retina to the brain.
Optician- A person who grinds lenses, fits them into a
frame, and adjusts the frame to the wearer.
Optometrist- A physician who specializes in refractive
errors, prescribes eyeglasses or contact lens and diagnoses and manages
conditions for the eye.
Orthoptics- The series of planned eye exercises used to
develop or restore the normal teamwork of the extraocular muscles of the eyes.
Orientation and Mobility- specialized teaching for
visually impaired persons including the use of a cane, dog guide, electronic
travel aids and sighted guide techniques.
OS- left eye
OU- both eyes
Peripheral vision- the perception of objects or motion
outside the direct line of vision. (“side vision”)
Prosthesis- Used here specifically for an artificial eye.
More generally, it means any -artificial part of the body.
Pupil- The circular opening in
the iris that allows light to pass through to the retina. The pupil dilates, or
becomes larger, to allow more light to enter the eye when lighting conditions
are low. The pupil constricts, or becomes smaller, to reduce the amount of light
entering the eye with lighting conditions are high. The size of the pupil is
controlled by the iris.
Reading stands- Bring work closer
to the eyes for optimum reading angles and lighting. Reduces neck and back pain
from bending down to the desk to read.
Refraction- 1.The deviation or bending of rays of light
when passing from one clear substance into another of a different density.
2 . The determination of refractive errors in the eye and their correction with
lenses.
Refractive error- A defect in the eye that prevents light
rays from coming to a single focus exactly on the retina.
Retina- The innermost layer of the eye mostly made up of
nerve fibers and rods/cones. Somewhat similar to the film in a camera.
Rx- prescription
SC- without correction
Slate and stylus- a small pocket sized device for
producing Braille in limited quantities and is a useful device in situations
where the student does not have access to a brailler.
Snellen chart- Test chart for assessing visual acuity. Usually tested at 20ft. Low vision charts are used for more exact assessments for nearer distance.
Tape recorders- For listening to
audio cassettes, to take notes, record lessons, do assignments, answer questions
and complete exams.
Thermoforms- heated formed raised lines on special paper.
Typoscope- a black piece of template with a slit to block
out all but the line of print that can be viewed through the slit and increasing
contrast for the print that is exposed. It limits the amount of information
shown at one time.
UTT- unable to test
Visual abilities- the dimension of functional vision that
includes visual acuity, visual fields, motility, brain function-control, and
light color perception.
VA-Visual acuity- The measurement of the eye’s ability to
distinguish the shapes and details of objects at a designated distance.
Visual clutter- a combination of images and backgrounds
that provide distracting details for some individuals who are unable to select a
single object from its background.
Visual fields- the area that can be seen when looking
straight ahead; the entire area without shifting the eyes or moving the head.
Visual functioning- how individuals use their ability to
see and interpret what is seen.
Visual impairment- a visual loss, after correction, that
affects an individual’s ability to perform tasks of daily life, caused by the
visual system that is not working properly or not formed correctly.
Visual perceptual skills- this refers to the process of
attaching meaning to a visual image. These skills encourage the use of
attending, (fixating), tracking, shifting attention between objects, scanning,
and reaching for objects. Visual perception occurs in the brain and it must be
determined whether the deficit skills are caused by the visual impairment or a
related brain-based perceptual problem.
Updated August 2, 2007