Bma Illustrated Medical Dictionary

propulsion of waste matter through the

colon. Other common causes include lack

of regular bowel movements due to poor

toilet-training in childhood or repeatedly

ignoring the urge to move the bowels.

Constipation in the elderly may be due to

immobility or to weakness of the muscles

of the abdomen and the pelvic floor.

Self-help measures such as establishing

a regular bowel routine, increasing the

amount of fibre in the diet, and drinking

more fluids are usually beneficial. Pro-

longed use of laxative drugscan impair

the normal functioning of the colon.

Constipation is occasionally a symptom

of an underlying disorder, especially if it

is part of a persistent change in bowel

habits after the age of 40, or if it is

accompanied by blood in the faeces, pain

on moving the bowels, or weight loss.

Conditions that may result in constipa-

tion include haemorrhoids, anal fissure,

irritable bowel syndrome, and narrowing

of the colon in, for example, diverticular

diseaseor cancer (see colon, cancer of).

constrictionA narrowed area, or the

process of narrowing.

contact dermatitisA type of dermatitis

caused by an allergic reaction to a sub-

stance that is in contact with the skin

and which would not cause a reaction

in most people exposed to it. Common

causes include nickel and rubber. (See

also irritant dermatitis.)

contact lensesVery thin, shell-like, trans-

parent discs fitted on the cornea of the

eye to correct defective vision. General-

ly, contact lenses are used to correct

myopia(shortsightedness) and hyperme-

tropia (longsightedness). There are several

CONTACT LENSES

and may cause the eyelids to be stuck

together on waking. In allergic conjunc-

tivitis, the discharge is clear and the

eyelids are often swollen.

Bacterial infections are treated with

antibioticeyedrops or ointment. Viral

conjunctivitis often disappears without

treatment. Allergic conjunctivitis may

be relieved by eyedrops containing an

antihistamineor a corticosteroid drug.

Other forms of conjunctivitis include

neonatalophthalmia, keratoconjunctivi-

tis, and trachoma.

connective tissueThe material that

supports, binds, or separates the vari-

ous structures of the body. Tendons and

cartilage are made up of connective tis-

sue, and it forms the matrix (ground

substance) of boneand the nonmuscu-

lar structures ofarteriesand veins.

connective tissue diseasesTypes of

autoimmune disordersthat often affect

blood vessels and produce secondary

connective tissuedamage. They include

rheumatoid arthritis, systemic lupus

erythematosus, polyarteritis nodosa, scle-

roderma, and dermatomyositis.

Conn’s syndromeA disorder caused

by the secretion of excessive amounts

of the hormone aldosteroneby a non-

cancerous tumour of one of the adrenal

glands. (See also aldosteronism.)

consciousnessA state of alertness in

which a person is fully aware of his or her

thoughts, surroundings, and intentions.

consentThe legal term describing a pa-

tient’s agreement to a doctor performing

an operation, arranging drug treatment,

or carrying out diagnostic tests.Strictly,

consent is valid only if the patient has

been fully informed about the purpose of

the procedure, the likely outcome, and

any complications and sideeffects. Con-

sent cannot be given by children or by

people with serious mental disorders,

but a relative may give or withhold con-

sent on their behalf. The patient’s

consent is also needed before a doctor

supplies confidential information to an

insurance company, employer, or lawyer.

constipationThe infrequent or difficult

passing of hard, dry faeces. Constipation

is usually harmless. The most common

cause is insufficient fibre in the diet (see

fibre, dietary), because fibre assists the

CONNECTIVE TISSUE CONTACT LENSES

C

Tear film

Soft

contact

lens

Cornea

Conjunctiva

Lens of

RIGID LENS eye

SOFT LENS