Diseases of The Optic Nerve and Retina
Optic neuritis, or inflammation of the optic disc, at the point where the optic nerve enters the back of the eyeball, is a symptom occurring in various conditions such as diseases of the kidneys, anaemia, diabetes mellitus, high blood pressure, and certain diseases of the brain. These may be inflam-mation or meningitis, tumour of the brain, syphilis of the brain with gummata or tumours, abscess, or tuberculous meningitis. Slight optic neuritis may occur after con-cussion; rarer causes are chronic poisoning with heavy metals such as lead, with alcohol, tobacco, or quinine, or multiple sclerosis.
There is congestion and swelling of the disc with inflammation of the surrounding retina, which is the inner layer of the eye containing the fine nerve endings of the optic nerve.
Usually both eyes are affected, although this may occur at different times. There may be no pain or loss of sight, but usually this develops rapidly, causing blurring of vision, with sickness, pain and headache.
If optic neuritis progresses, it leads to optic atrophy or destruction of the optic nerve, which may also follow fractures of the skull.
In secondary syphilis, optic neuritis is liable to develop within six to eighteen months after the primary sore, if this is untreated.
If syphilis is suspected, a Wassermann blood test must be carried out and antisyphilitic treatment given when this is indicated. The outlook is good in these cases if treatment is given early and carried out thoroughly.
When a tumour of the brain is suspected, it is often necessary to trephine (or drill) the skull to reduce the pressure, and save the eyesight.
In optic neuritis due to kidney disease the outlook is unfavourable, and cases often end fatally within eighteen months.
Inflammation of the Optic Nerve Behind The Eyeball
Inflammation of the optic nerve behind the eyeball may develop in nicotine poison-ing in heavy smokers who smoke strong dark tobacco over long periods. Loss of sight for green or red objects, or for yellow, occurs in this condition, while ordinary white light can still be seen.
If smoking and chewing tobacco are given up, the sight usually improves steadily.
Detachment of the Retina
When a heavy blow falls upon a healthy eye it may cause bleeding into the retina, or nerve-layer, of the eye; while in short-sighted persons slight bruising, or even the strain caused by stooping down, may cause separation of the retina from the outer wall of the eyeball. There is sudden loss of sight, usually in the upper part of the eye, as though a curtain had half descended.
When the case is diagnosed the patient must lie absolutely quiet in bed, to allow the retina to settle back into place. Surgical treatment is often good for an acute attack, but recurrences may occur.
Laser beam rays have proved valuable in fixing the retina in position again.
There are various types of tumours of the orbit and eye which occur, but they are all relatively uncommon. They may affect the bony walls of the orbit, the optic nerve, retina, choroid or sclera, or rarely the iris. Tumours of the brain may affect the eyesight by pressure on the optic nerve.
Dr. T. Hossain
The author is an eye-especialist in Toronto.
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