How It Works: Science and Technology - Vol. 12

How It Works: Science and Technology - Vol. 12

How It Works: Science and Technology - Vol. 12

How It Works: Science and Technology - Vol. 12

Excerpt

Ophthalmology

A surgeon uses a binocular operating microscope during an eye operation while a student follows the operation’s progress using the other set of binoculars.

Ophthalmology is the medical specialty concerned with the diagnosis and treatment of eye disorders. All ophthalmologists are physicians. They are sometimes called oculists but should not be confused with optometrists, who are people who test vision and prescribe glasses and contact lenses. Optometrists are not primarily concerned with eye diseases.

The range of equipment used by ophthalmologists has increased greatly in recent years. It includes slit lamp microscopes to examine the outside and front interior of the eyes under high magnification; automatic refractors to check whether glasses are needed; various kinds of ophthalmoscopes to examine the insides of the eyes; visual field analyzers to check how far the field of vision extends outwards and to see whether there are any defects in the visual fields; ultrasound eye measurement equipment to work out the power of lens implants needed after cataract surgery; lasers to treat a range of conditions and to seal holes in the retina; cryopexy equipment to freeze parts of the eye and secure attachment of detached retinas; and diathermy equipment to control minor bleeding in the eye.

Diseases of the eye

There are many conditions that affect the eye, some of which respond to drug treatment and others requiring surgery. The outer eye is suspect to inflammations of the lids, cornea, and lachrymal ducts that can arise through scratches from foreign bodies or infections of the sinuses or eyelash follicles. Most of these conditions can be treated with antibiotics or under local anesthetic to remove small growths or abscesses.

One of the most common ailments that impairs vision is the development of a cataract, which causes the lens to become opaque. Cataracts are mainly a consequence of aging but can also be found in infants whose mothers contracted rubella in early pregnancy. Exposure to certain drugs or radiation can also result in cataracts forming as can wounds that perforate the lens. Removing cataracts today is a straightforward procedure that uses a small ultrasonicprobe to shatter the lens into fragments that can then be sucked out. An artificial lens is then inserted into the eyeball, or the patient is prescribed special glasses or contact lenses to enable the eyes to focus.

The most serious problems with the eye are those affecting the retina and the optic nerve at the back of the eyeball. The retina is a thin layer that contains the rod and cone cells that provide color vision and has only a limited ability to repair any damage sustained. Small holes or tears can occur in the retina from physical injury and are common among nearsighted people, whose larger eyeballs may stretch the covering layers of the eye. As a result, the vitreous humor leaks through the retina, detaching it from the pigmented layer behind. Today ophthalmologists repair such tears using a laser, effectively spot welding the retina back in place.

The retina is also subject to degenerative diseases that can be hereditary or senile in nature. Retinitis pigmentosa is a hereditary condition that causes progressive loss of the field of vision until only a small tubular field remains. By contrast, in old age there can be a loss of vision from the central part of the retina owing to a decrease in the blood supply to the macula. Neither condition can be treated satisfactorily by drugs or surgery, though some improvement can be made by using corrective lenses.

Damage to the optic nerve can occur as a result of brain swelling from tumors or head injury. Pressure must be reduced quickly to prevent atrophy, which often leads to blindness. The . . .

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