| Cataract
What is Cataract ?
A cataract is the condition in which the
crystalline lens of the eye becomes clouded or opaque, impairing vision and, if untreated,
can lead to blindness. Nearly two-thirds of all cases in Western countries affects people
over the age of 65.
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Known causes
The lens in the eye transmits light rays onto the
retina at the back of the eyeball which are then interpreted by the brain into images. It
is also through the lens that we are able to focus on objects, whether they be a few
inches away or 100 yards in the distance. A tiny muscle in the eye, known as the ciliary
muscle, changes the shape of the lens to enable the eye to focus on different objects. If
the lens becomes opaque or clouded, its shape cannot be effectively controlled by the
ciliary muscle which prevents proper focussing on objects and, due to the clouding of the
lens, general vision becomes impaired and can even lead to blindness.
There are thought to be many potential causes of cataract:- The vast majority of cataracts
are considered to be the result of an age-related change in the lens unassociated with
other disease processes. As we age, the structure and function of the lens begins to
degenerate. Through a complex series of chemical events, opacification ensues.
• Cataracts may be secondary to another eye disease. Intraocular inflammation,
retinitis pigmentosa, glaucoma, and many others can be associated with lens opacity.
• Cataracts may be toxic, i.e. drug-induced or diet-induced. Cortisone-type steroids
are the most commonly implicated medications.
• Cataract may be caused as a result of injury in early life. (Rapidly forming
cataracts usually occurs after direct injury to the lens from an object that penetrates or
cuts open the eye.)
• Systemic illnesses have also been associated with cataract formation. Diabetes
mellitus may be the most common, but the list includes Down's syndrome, myotonic
dystrophy, Marfan's syndrome, allergic dermatitis, and many other diseases.
• Congenital or infantile cataracts can occur spontaneously as a primary disorder, or
secondary to systemic diseases. Among the associated conditions are maternal infection
with rubella (German measles) or other agents, metabolic disturbances, hereditary
disorders, neurologic diseases, and rarely, birth injury.
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Symptoms
The symptoms usually begin with a gradual
diminution or blurring of vision. Glare from sunlight or nighttime driving can be a
significant problem.
Cataract most often affects people betwen the ages of 50 and 70 but the symptoms may first
appear at a much younger age, especially if cataract- associated diseases are present.
Congenital cataracts may be dense enough to preclude useful vision beginning at birth.
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Conventional Treatment
Conventional treatment for cataracts is entirely
surgical: the crystalline lens is removed. There are no known effective medications.
Surgery is usually only considered when the cataract is dense enough to alter the person's
ability to perform daily activities, but each individual case is assessed on the specific
circumstances. For example, a 55 year old taxi driver may need an operation much sooner
than an elderly, bed-ridden patient.
Cataract surgery is available to all individuals in the UK and many thousands of
operations are performed each year. In the USA over 500,000 cataract operations are
performed each year at a cost of over $3.8 billion. A variety of surgical procedures are
performed but the most common method is now the implanting of another lens in the eye to
replace the damaged one. The problem, of course, with this treatment is that it does not
affect the underlying causes that led to the cataract in the first place. Furthermore,
recent research (2) suggests that mental complications can arise as a result of the
treatment including confusion, agitation, schizophrenia, aberant behaviour and nervousness
which have, in some cases, necessitated sedative drugs and/or psychotherapy.
(1) British National Formulary
(2) Report of six cases of mental complications after cataractopiesis. Jiang S
Department of Ophthalmology, First Affiliated Hospital, Hubei Medical College
Wuhan, China. Yen Ko Hsueh Pao (CHINA) Jun 1991, 7 (2) p77-8
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