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and in five cases on both sides. In one case only was the deafness due to internal
ear complications.
Other infective diseases are represented chiefly by congenital syphilis, of which
there were 7 cases, or 4.3 per cent. of all acquired cases. This is practically the same
proportion as in 1925. Three cases of deafness due to pneumonia (two suppurative,
one catarrhal), all preventable, are included in this section.
The great majority of the cases in the partially deaf schools is drawn from
these cases, included under the heading of primary ear diseases, the remainder
coming from the infectious diseases class. They are, this year, all cases of chronic
middle ear catarrh and chronic middle ear suppuration or its results. They
numbered 114 in all, or 70.3 per cent. of all acquired cases. The cases of middle ear
catarrh were 56, in which no less than 49 had undergone operation for tonsils and
adenoids, some more than once. The cases of deafness due to middle ear suppuration
or its results were 53, the number having had tonsils and adenoids removed being
19. In many the suppuration had begun in early life and the original cause could
not be ascertained with certainty. In all probability, however, it had commenced
in the course of an inflammation of the upper air passages. In one case it followed
an operation for cleft palate. The mastoid operation had been performed 14 times,
on one side in 9, on both sides in 5.
Nine cases of deafness due to injury (5.5 per cent. of all acquired cases) were
seen. In each instance the deafness followed a fall on the head.
During the year under review the whole question of the cause of blindness, and
the measures for prevention and treatment available, were considered in the light of
the powers afforded in areas other than London by the Public Health Act, 1925.
The most recent authoritative statement on the causes of blindness was contained
in the report of the Departmental Committee of the Ministry of Health, many of
the data of which were supplied by the Council's Ophthalmic Consultant.
Causes of
blindness
and means
for
prevention.
Age of incidence of the onset of blindness.—The following table contains the age
of incidence of the onset of blindness:—
Age. Per cent. Age. Per cent. Age. Per cent.
0—1 21.4 20—30 9.7 50—60 9.5
1—10 10.8 30—40 9.7 60—70 9.6
10—20 94 40—50 11.0 70 6.4
Apart from the initial crop the incidence appears to be fairly steady throughout
life.
Causes of Blindness.—These may be classified into six groups: Congenital
defects; Inflammatory conditions of the surface of the eye; Inflammations inside
the eye; Accidents, chiefly industrial; Myopia; Senile changes.
These vary in their incidence at different age periods while the possible measures
for prevention are also varied in character.
The chief factors which lead to blindness are:—
(1) Before the school age, congenital defects and ophthalmia neonatorum.
(2) During the years of school life, inflammations, as a result of congenital
syphilis, play a large part, as do some of the surface inflammations which are not
connected with veneral disease, while myopia begins to be an effective agent.
(3) In adult and middle life, accidents assume a prominent part in the
causation of blindness, lesions resulting either from congenital or acquired
syphilis continue to be important factors, while the loss of vision due to the
secondary changes in the eyes of high myopes has usually made itself known
by the end of this period.
(4) After fifty, glaucoma and cataract which may be looked upon as largely
senile conditions are the most important factors.
Methods of prevention.—Under these must be considered both the prevention
of the morbid condition responsible for the damage to the eye and the prevention,
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