Night blindness Health Dictionary

The statutory de?nition – for the purposes of registration as a blind person under the National Assistance Act 1948 – is that the person is ‘so blind as to be unable to perform any work for which eyesight is essential’. Generally this is vision worse than 6/60 in the better eye, or with better acuity than this but where ‘the ?eld of vision is markedly contracted in the greater part of its extent’. Partial sight has no statutory de?nition, but there are o?cial guidelines for registering a person as partially sighted: generally these are a corrected visual acuity of 3/ 60 or less in the better eye with some contraction of the peripheral ?eld, or better with gross ?eld defects. In the UK more than 100,000 people are registered as legally blind and some 50,000 as partially sighted. The World Health Organisation has estimated that there are over 40 million binocularly blind people in the world. The causes of blindness vary with age and degree of development of the country. In western society the commonest causes are glaucoma, diabetic retinopathy, other retinal diseases and senile cataract. (See also VISION.)

Any blind person, or his or her relatives, can obtain help and advice from the Royal National Institute for the Blind (www.rnib.org.uk).

Night blindness An inability to see in the dark. It can be associated with retinitis pigmentosa or vitamin A de?ciency (see EYE, DISORDERS OF).... blindness

See VISION – Defective colour vision.... colour blindness

Damage caused to the cornea of an unprotected EYE by the re?ection of the sun’s rays from snow. ULTRAVIOLET RAYS (UVR) are the damaging agent and people going out in snow and sunlight should wear protective goggles. The condition is painful but resolves if the eyes are covered with pads for a day or two. Prolonged exposure may seriously damage the cornea and impair vision.... snow blindness

Alexia: a condition in which, as the result of disease in the brain, a person becomes unable to associate their proper meanings with words, although he or she may be quite able to spell the letters.

Word deafness is an associated condition in which, although hearing remains perfect, the patient has lost the power of referring the names heard to the articles they denote. (See also DYSPHASIA.)... word blindness

A condition in which the patient sees better in a dim light or by night than in daylight. It is only found in conditions in which the light is very glaring, as in the desert and on snow, and is relieved by resting the retina (see EYE) – for example, by wearing coloured glasses for a time.... day blindness

See onchocerciasis.... river blindness

A disorder, occurring mainly in children, that consists of abrupt arousals from sleep in a terrified state. Night terror (also called sleep terror) usually starts between the ages of 4 and 7, gradually disappearing in early adolescence.

Episodes occur during (nonrapid eye movement) sleep, usually half an hour to 3 and a half hours after falling asleep. Sufferers wake up screaming in a semiconscious state and remain frightened for some minutes. They do not recognize familiar faces or surroundings, and usually cannot be comforted. The sufferer gradually falls back to sleep and has no memory of the event the following day.

Night terror in children has no serious significance, but, in adults, is likely to be associated with an anxiety disorder.... night terror

(American) Born in the evening; child of the darkness Nite, Nyt, Nyte, Nyght... night

Copious PERSPIRATION occurring in bed at night and found in conditions such as TUBERCULOSIS, BRUCELLOSIS and lymphomas (see LYMPHOMA), as well as thyrotoxicosis (see under THYROID GLAND, DISEASES OF), anxiety states and menopausal ?ushes (see MENOPAUSE).... night sweats

A service that enables a caregiver night rest (e.g. where night disturbances of the older person receiving care are frequent).... night-sitting service

Inability to see at night or in imperfect light due to a deficiency of visual purple (rhodopsin) in the rods at the back of the eye due to low level Vitamin A. Night myopia usually affects people during twilight. “One in five people are not fit to drive at night.” May occur in glaucoma and other eye disorders. Other causes: old age, free radical damage.

Alfalfa tea freely.

Of value: Kelp, Irish Moss, Iceland Moss.

Diet. Vitamin A foods, carrots, bilberries, Cod Liver oil.

Supplements. Vitamin A, Beta-carotene. C (2g), E (400iu). B-complex, B2, Niacin, Zinc. ... eyes  - night blindness

See: CACTUS. ... night blooming cereus

copious sweating during sleep. Night sweats may be an early indication of tuberculosis, AIDS, or other disease.... night sweat