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Glossary

Accommodation: is the involuntary act of the eyes' crystalline lens to add extra strength to the vision optical system assisting in the capacity to focus on objects nearby; aging of the crystalline lens causes a reduced accommodative ability called "presbyopia"; strength added to lenses to counter presbyopia is call "the add".

Add, the: the add is that part of a spectacle prescription which applies extra strength to a lens; the add is used to assist the eye in focusing while looking at things nearby (i.e., reading, cooking, playing cards); the add relieves accommodation; the add may be a single vision reading lens, bifocal, trifocal, or P.A.L.; the strength and design of the add determines the limitations and location of the "sweet spot"; stronger adds cause greater limitations and consequently lens design considerations become more critical.

AR coating: Anti-reflection coating reduces reflections on lenses by approximately 7 percent per lens side; is useful for promoting better vision by reducing reflections which compete with what you want to see; especially effective for night driving, especially effective for persons who are nearsighted, especially effective for the elderly who need more light to see.

ARMD: (age related macular degeneration) a condition which effects central vision but does not generally effect the peripheral vision; rehabilitation is very effective with persons who are adaptable and willing to adjust. Using low vision aids and or a CCTV may help significantly. Also referred to as magnifier.

Blind: a condition usually defined as vision that measures at least 20/200 in the best eye with correction or no more than 20 degrees of vision in the best eye with correction; less than 10 percent of the legally blind are totally blind.

Braille: a tactile way to read and write; may be a very important tool to develop, especially if your prognosis is uncertain.

CCTV; the closed circuit television, or video magnifier is generally used by the legally blind (with partial vision) and visually impaired that allows them to read newspapers, medicine bottles, bills, etc., to write checks, letters, etc., and to look at photographs and other items: this machine enables persons with magnifier to maintain their affairs and remain productive.

"Can do" attitude: an ability to overcome frustration and despair.

Cataract: opacity found in the crystalline lens within the eye, can be caused by exposure to ultraviolet light, contributes to sensitivity to violet light, may interfere with vision, may be removed by excising the crystalline lens.

Close focus: an optical instrument which has an ability to view an object closely and still have it in focus.

Commission for the Blind: a state social service organization responsible for the rehabilitation of citizens who qualify; for some services, one needs only to be legally blind not totally blind and for other services visual dysfunction matched with other criteria

Computer magnification systems: an access technology which permits the visually impaired to use computers and see the computer monitor.

Crystalline lens: natural lens found inside the eye, adding approximately 17 diopters to the optical system (vision); responsible for adding diopters as needed to the vision optical system when viewing something nearby (accommodation); place where cataracts form; its failure is responsible for the condition called presbyopia.

D: see diopter

DSF: dark special filter, amber 16% transmission, used outdoors in full sun conditions; 40% more effective when designed to wrap around the face, keeping its electromagnetic filtering effective from the side, up above and in front; filters out ultraviolet and filters violet light.

Denial: a state of mind that precludes developing useful alternatives to vision loss.

Depth of field: defined by the strength of a lens: the greater the strength of the lens, the more confining the depth of field; a critical issue to know about when learning to use "low vision aids".

Diabetic retinopathy: a condition responsible for vision loss in some diabetics. Using low vision aids and or a CCTVs may help significantly.

Diopter: (D), unit of measure for the ability of a lens to alter the direction of a ray of light; 1 diopter will alter a ray of light 1 centimeter over a distance of 1 meter; 4 diopters (D) equals 1 power of magnification (X).

Distance: those items which are viewed beyond arm's length are considered in the distance, i.e., curbs, steps, television, etc.

Field of view: that area defined by the constraints of an optical system; the stronger the optical system, the smaller the field of view.

Focal distance: determined by the strength of the lens; in plus lenses the greater the strength, the shorter the focal distance (this is why one needs to hold their reading material ever closer and closer as they get stronger and stronger adds in their lenses and also the reason for holding a magnifier close to one's face).

Full view: spectacle lenses which are significantly large enough to place the optical correction in front of the eye's line of sight.

Glaucoma: an eye condition which if untreated may lead to blindness; treatment is effective with early detection and when medicine regimen is followed precisely; vision loss is effected from the outside in; peripheral vision is lost leaving one with ever increasing tunnel vision.

Half-eyes: spectacle lenses which are significantly small enough to allow the eye to either look through the lens or over the lens; useful for reading glasses and magnifying spectacles.

IOL: interocular lens used to replace the crystalline lens when the crystalline lens was removed due to cataract or for some other reason; certainly better than a crystalline lens with a cataract but it does not have the capacity to add extra power which is needed to see clearly up close; progressive addition lenses are a good solution here because they offer a more natural (no line) multi-focal type of vision; UV filters strongly recommended because earlier IOLs did not have UV filters in them, whereas the original crystalline lens protected the retina from UV; new IOLs have been developed that don't have little holes in them, a style superior to the older style that should be asked about when considering this procedure.

Intermediate: those items which are viewed at approximately arms distance are considered in the intermediate.

LSF: light special filters effective in eliminating ultraviolet, filtering violet light, heightening contrast, improving visual functioning and promoting comfort; yellow 54 percent transmission.

Lap desk: used on a table to hold reading materials up at the proper angle to assist with using a high power magnifier or close focus telescope.

Lens design: the factors of an optical lens (other than the prescription) which determine how it is going to function; level of satisfaction is determined by your dispenser's ability to advise you about options not specified by the prescription that are available and will potentially meet your particular needs; options include but are not limited to AR coating, violet light filtering, DSF, distance, half eyes, intermediate, LSF, magnifying spectacles, PAL, polarization, UV filtering; some options may be used in combination.

Lighting: of major importance in the promotion of visual functioning; task lighting is useful for specific tasks like reading, cooking, doing dishes, etc.; area lighting is useful for walking around; the source of the lighting should be positioned to see indirectly.

Low vision: term used to describe a level of unaided visual ability insufficient to perform certain tasks like reading.

Low vision aids: any device (optical or non-optical) which assists one who has low vision, i.e., magnifiers, telescopes, special purpose glasses, check writing guide, etc.; there are over 1000 low vision aids.

Macular degeneration: see ARMD

Magnifier: tool used to see anything up close; enlarges object being viewed; allows one to view objects closely; very effective when used properly for persons with magnifier; may be used by the legally blind with partial vision as a reading tool.

Magnifying spectacles: spectacles whose lenses are magnifiers.

Monocular: a telescopic-type optical tool used to magnify and view objects in greater detail; used with one eye, usually hand held; lower powers may be mounted on eyeglasses; hand-held units particularly effective for spotting and reading signs, i.e., Walk/Don't Walk signs, street signs, rest room signs, bus numbers, etc.

Nonprescription lenses: these lenses magnify only, i.e., ready made reading glasses, magnifiers and telescopes; prescriptions may be written for these items but are not necessary for their purchase (in most states).

Ophthalmologist: a Medical Doctor, M.D., who can, among other things, do refractions on, prescribe medications for and do surgery on eyes.

Optician: responsible for filling your prescription for corrective lenses; understands lenses and their effectiveness; makes recommendations about different lens options which are by the prescription; helps you select those products which are most appropriate and teaches you how to use them; opticians are licensed in only 25 states (your ability to find a qualified optician is better in those states where opticians are licensed; in those other States a measure of qualification is if the optician is American Board of Opticianry Certified (A.B.O.C.)).

Optigram: a diagram designed by Ralph Sherman, Dispensing Optician, for the express purpose of assisting in the magnifier selection process; potentially maximizes one's reading potential through the use of nonprescription magnifiers.

Optometrist: Doctor of Optometry, O. D., who among other things, does refractions and writes prescriptions for corrective lenses.

Orientation and mobility: adaptive skills the blind and or visually impaired need to know to travel around on their own and know where they are going, i.e., cane techniques and using a monocular.

PAL: the progressive addition lens adds power to the lens progressively, allowing a user of this style of lens to have a more varied area of corrected near vision than would be accomplished by bifocals or trifocals; there is no line in the path of one's eye as it moves from distance to near viewing; sometimes called a "no line bifocal"; particularly effective for persons with IOLs.

Peer support group: attending one is a very effective means to develop a better understanding of what problems are associated with vision loss and their potential solutions.

Peripheral vision: that vision which is most sensitive to motion and is most normally used for viewing things as they pass by, for instance while walking; normally not effected in cases of magnifier; may be used for supplementing central field deficits caused by magnifier by using low vision aids like magnifiers and telescopes.

Polarization: reduces light reflected off the horizontal; especially effective when used around water, snow, wet or icy conditions, and in traffic.

Power: (X), the American formula for the power of a magnifier or telescope, 1 level of power equals 4 diopters, i.e., 4 power equals 16 diopters; the exception to this rule is when the power is figured by the European method -- their equation leaves the dioptric equivalent always 4 diopters less than the American method, i.e., 4 power equals 12 diopters (knowing where the item is manufactured becomes necessary if you are ordering a item by its power notation because there is no international standard and you may not get the appropriate dioptric equivalent for your purposes); diopters and power are not interchangeable -- a 6 diopter (D) half eye is one and one half power (X), a 6 power (X) half eye is 24 diopters (D).

Presbyopia: condition caused by aging of the crystalline lens; effects one's ability to focus on those things viewed nearby; additional strength is required to replace the eyes' increasing inability to add this extra strength; bifocals are often appropriate; dozens of alternative lens designs are available and are sometimes more appropriate, i.e., trifocals, PALs, reading glasses.

Prescription lenses: only an Optometrist or Ophthalmologist may write a prescription for corrective lenses; components of a prescription may be sphere, cylinder, axis, add, prism, vertex distance; components that may be necessary for satisfaction but not specified by most prescriptions are pupillary distance, segment height, optical center, lens design, tints, coatings, filters, directions in their use and care; prescription lenses may not be purchased without a signed and current (not more than 2 years old) prescription.

Reading glasses: a special purpose pair of glasses used for reading that may be prescription or nonprescription; may, however be designed for use as an intermediate vision glasses used at one's desk to see the things on the desk and potentially a computer screen or a CCTV; sometimes a good alternative to bifocals, trifocals or PAL.

Retinitis Pigmentosa: a eye disease that takes vision away from the periphery and gradually continues to cause ever greater tunnel vision. Low vision aids and CCTVs are useful but large amount of magnification are contra indicated because the patient's field of view is limited.

Reliance alliance: a mutual partnership in promoting and maintaining another person's quality of life.

Synthetic speech: this technology provides access to computer information through sound; the computer will talk to you through synthetic speech.

Sweet spot: that area defined by limitations of depth of field and focal distance relative to a lens' strength and design; the greater the strength of the lens, the shorter the focal distance and the more confining the depth of field; the greater the strength of the lens the more important design features become (to find your lenses' sweet spot hold your reading material in front of you and look through the lower part of your lenses, now slowly move the text toward you, and when it comes into focus you have found the sweet spot).

Telescopes: may be prescription or nonprescription, are sometimes monocular (one eye), sometimes binocular (two eyes); lower powers may be mounted on eyeglasses; used to magnify and promote a better visual response by concentrating the image on a greater area of the eye; telescopic spectacles are particularly effective for watching TV; close focus are good for viewing at intermediate distances, i.e., piano music or hobbies; hand held are good for sightseeing and reading signs, etc.

Trifocals: a lens design with three areas to look through, the top area is for distance vision, the central area is for intermediate vision, and the lower part is for near vision; each division is separated by a line which is sometimes in the way; a more natural (no line) alternative may be the PAL.

UV: ultraviolet is an invisible part of the electromagnetic spectrum, of which visible light is also a part; ultraviolet is one cause of cataracts, and speculation exists about its role in promoting magnifier; spectacles with lenses that filter out UV are effective in reducing exposure to UV and therefore potentially protect and comfort the eye.

Violet light: a part of the visible light spectrum that causes reduced visual functioning; suspected of contributing to the development of magnifier.

Vision aid services: Those services that meet the needs of persons whose vision is less than 20/20 fully corrected and persons who suffer either productivity or comfort problems associated with visual dysfunction regardless of visual acuity.

X: see Power