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DEVELOPMENTAL MYOPIA AND THE TREATMENT OF MYOPES
795 and in more detail by Lewis in 1910 and from that date has been recognised as a clinical entity. In 1911 the first edition of " The Mechanism of the Heart Beat " 28 appeared, since when the string
galvanometer has played an increasing part in the practice of medicine. With the introduction of the galvanometer there followed a period of intensive investigation of all forms of abnormal rhythms with the result that the clinical picture of these
vagaries became so sharply defined that it was possible in most instances to make an accurate diagnosis without resort to the galvanometer. In a sense the electrocardiogram, so far as the arrhythmias are concerned, had played its part as an instrument of precision. Subsequently for some years, apart from research work, the electrocardiograph was employed clinically for teaching purposes and in the investigation of the less obvious and rarer forms of cardiac disorders. A new era began with the recognition of the peculiar and specific changes in the electrocardiogram associated with coronary infarction. Attention was increasingly focused on the myocardium and on lesions of the coronary arteries. This has stimulated further research and the electrocardiograph has proved its value in the investigation and determination of the integrity of the myocardium. It was clear that in it we possessed an instrument which could help in assessing the degree of the myocardial damage and recording the phases of recovery. With its aid the diagnosis of a typical case of coronary thrombosis has been placed on a sure basis and we are now in a position comparable to that in regard to the arrhythmias in which an electrocardiogram has become almost redundant. Unfortunately this stage has not yet been reached in the atypical and aberrant forms. Here we are still dependent on the machine for diagnosis and corroboration. Nevertheless, even in this more obscure field, knowledge is growing, facts are being accumulated, and the electrocardiograph is steadily guiding us to a clearer conception of the clinical results of coronary disease. REFERENCES
1. Herrick, J. B.: Jour. Amer. Med. Assoc., 1912, lix., 2015. 2. : Ibid., 1919, lxxii., 387. ,, 3. Libman, E.: Med. Record (New York), 1916, lxxxix., 124. 4. Levine, S. A. and Tranter, C. L. : Amer. Jour. Med. Sci., 1918, clv., 57. 5. Pardee, H. E. B. : Arch. Internal Med., 1920, xxvi., 244. 6. Longcope, W. T.: Illinois Med. Jour., 1922, xli., 186. 7. Wearn, J. T.: Amer. Jour. Med. Sci., 1923, clxv., 250. 8. Levine and Brown, C. L.: Medicine Monographs, 1929, vol. xvi. 9. Wolff, L., and White, P. D.: Boston Med. and Surg. Jour., 1926, cxcv., 13. 10. Christian, H. A. : North Western Medicine, December, 1925. 11. Gibson, A. G. : THE LANCET, 1925, ii., 1270. 12. McNee, J. W. : Quart. Jour. Med., 1925-1926, xix., 44. 13. Parkinson, J., and Bedford, D. E.: Heart. 1928, xiv., 195. 14. ,, ,, ,, : THE LANCET, 1928, i., 4. ,, 15. Parkinson : Brit. Med. Jour., 1932, ii., 549. 16. Lewis, T.: Arch. Internal Med., 1932, xlix., 713. 17. Davis, N. S.: Jour. Amer. Med. Assoc., 1932, xcviii., 1806. 18. Levine and Brown : Medicine, 1929, viii., 280. 19. Bell, A., and Pardee, : Jour. Amer. Med. Assoc., 1930, xciv., 1555. 20. Pardee : Amer. Jour. Med. Sci., 1925, clxix., 255. 21. Smith, F. M.: Arch. Internal Med., 1923, xxxii., 497. 22. Levy, R. L.: Ibid., 1931, xlvii., 1. 23. Holland, C. W., and Levine: Jour. Amer. Med. Assoc. (Abstract), 1932, xcviii., 1943. 24. Wilson, W. J. : Ann. Clin. Med., 1926, v., 238. 25. Pardee : Arch. Internal Med., 1930, xlvi., 470. 26. Wolferth, C. C., and Wood, F. C. : Amer. Jour. Med. Sci., 1932, clxxxiii., 30 ; Med. Clin. N. Amer., 1932, xvi., 161 ; Arch. Internal Med., 1933, li., 771. 27. Lewis: Brit. Med. Jour., 1909, ii., 1528 ; THE LANCET, 1909, ii., 1820 ; Heart, 1909-1910, i., 306. 28. Lewis: Mechanism of the Heart-Beat. London, 1911. ,,
DEVELOPMENTAL MYOPIA AND THE TREATMENT OF MYOPES BY SIR JOHN PARSONS, C.B.E., M.B., D.SC. LOND., F.R.C.S. ENG., F.R.S. CONSULTING SURGEON TO THE ROYAL LONDON OPHTHALMIC HOSPITAL ; CONSULTING OPHTHALMIC SURGEON TO UNIVERSITY COLLEGE HOSPITAL
THE state of static refraction of an eye is the result of the integration of a large number of variables. In most text-books too much stress is laid upon the length of the eye. It has been shown by actual measurements that the length of the emmetropic eye may vary by as much as 2 mm., and the radius of curvature of the cornea from 7 to 8-5 mm. Compensating factors are the curvatures of the refracting surfaces, the indices of refraction of the media, and the position of the lens. As an example, a buphthalmic eye may be as much as 31 mm. in length from the anterior surface of the cornea to the retina, and yet not be myopic. Myopia may be due theoretically to any of the following conditions :-
Abnormally increased length myopia). 1.
of
the
eye
curvature of the refracting : myopia): (a) too strong curvature (curvature cornea; (b) too strong curvature of one or both 2. Abnormal
(axial
surfaces of the surfaces
of the lens. 3. Abnormal refractive indices of the media (index myopia):(a) too high index of the cornea or aqueous ; (b) too high total index of the lens, due to too high index of the nucleus or too low index of the cortex ; (c) too low index of the vitreous. 4. Displacement forwards of the lens. 5. A combination of the above factors.
The
development of the eye is such that the normal is born with hypermetropic eyes. During the baby first years of life the various factors change in such a manner that the eye becomes less hypermetropic and may become perfectly emmetropic. Statistics of the incidence of emmetropia and ametropia at different ages are very unsatisfactory owing to several reasons. The estimates of different observers are not always reliable or strictly comparable ; but the chief source of ambiguity is the valuation for statistical purposes which should be allotted to various degrees of astigmatism. From the statistical point of view, however, the generalisation that the normal eye is hypermetropic at birth and tends constantly during the early years of life towards a condition of diminished hypermetropia may be regarded
as
true.
THE NORMAL AND THE IDEAL NORMAL
The statistical investigation of any variable commences with the determination of its frequency distribution. Thus, if in an adult male population the numbers of individuals are plotted against their heights, a " cocked hat " curve is obtained which almost exactly coincides with the theoretical ideal symmetrical frequency-distribution curve. In such a curve the criterion of absolute normality is given by the maximum ordinate, but slight differences on each side of the maximum cannot be regarded as pathologically abnormal. In very many biological and other examples-e.g., the weight of adult malesthe distribution curve is asymmetrical or skew, the greater frequencies lying towards one or other end of the range. Owing to the higher incidence of hypermetropes at birth we should expect the frequency
796 distribution of variations in refraction to present such a skew deviation curve. In all such "populations " large numbers of individuals approximate nearly to the statistical ideal normal as judged by the maximum ordinate of the frequency curve. Apart from the statistical examination there is often no more reason for regarding these as less normal than the ideal normal. In the case of the refraction of the eye, on the other hand, the normal has not been arrived at by statistical methods, but by quite other considerations. Emmetropia is the condition in which parallel rays are brought to a focus on the retina ; optically considered, it is an ideal normal. Moreover, it is one to which large numbers of individuals conform, and which must therefore deviate little from the statistical normal. The cases are rare in which nature attains the optimum invariably, as in the angle of the honeycomb cell; and emmetropia is certainly not one of these cases. Owing to the prolonged immaturity of the young of primates, and especially man, the teleological argument would lead one to expect that human vision is specially adapted to the requirements of early and middle adult life. During this period accommodation is active, and the moderate hypermetrope is at least as well adapted to everyday life as the emmetrope. The fact that practically all mammals are hypermetropic would lead one to expect that their statistical ideal normal is definitely hypermetropic, and it would seem that in man the frequency curve has shifted towards the emmetropic condition. Too much stress cannot, however, be placed on this argument, owing to the absence of a fovea in lower mammals and the differences in their vision and mode of life. It would be interesting to know whether the lower primates are ever emme-
tropic .
or
myopic.
it would seem certain that from the biological point of view we should expect to find many examples of permanent low hypermetropia, and a few-but perhaps not negligible-examples of permanent low myopia. Such cases are fundamentally no more pathologically abnormal than short men or tall men. My own experience, chiefly derived from private cases carefully watched over a number of years, is that cases of "stationary" myopia conforming to this hypothesis are not very uncommon. One meets with children with very low degrees of myopia which increase up to a maximum of 1 or 2 dioptres during the growing period, and then remain quite stationary. As a rule their fundi are perfectly normal, and there are no myopic crescents. Of course it is impossible to be certain that any such child belongs to this group of "’ developmental myopia," since every progressive myope must pass through the stage of low myopia. Certainly some such cases remain stationary for many years. In any
case
VISUAL CAPACITY
If, as suggested above, there has been a tendency iri the mammalia for the maximum of the frequency curve to shift towards low hypermetropia or emmetropia, some enhancement of this tendency might be anticipated as the result of civilised conditions. If so, it would not be surprising for cases of low myopia to occur from this cause. Important as perfect visual acuity is, I am of opinion that its value is not infrequently over-estimated. A man’s visual efficiency depends not only on his visual acuity, but also upon his field of vision, rapidity of accommodation and adaptation, and many other factors which can be conveniently summed up in
the term ’visual capacity.1 Even when a man’s visual capacity has diminished his working efficiency for his job may be little impaired, owing to the compensating effects of acquired technical skill. This fact was conclusively proved in certain cases by an investigation carried out by the Committee on the Physiology of Vision of the Medical Research Council for the Royal Navy. It is a well-known fact that a good game shot remains good long after his visual capacity has materially declined. MYOPIA AND NEAR WORK
remarkable fact that the eye, which can be regarded as having been evolved for the express purpose of adaptation to the needs of civilised life, is yet capable of fulfilling them with relatively There are, little detriment or even discomfort. indeed, many occupations in which a low degree of per se, is a real asset. If there are cases of myopia, " stationary " myopia such as I have suggested, they are eminently suited for such occupations, since there is no reason to suppose that they would suffer in any way. I think the evidence is in favour of the view that degrees of myopia (e.g., of 4 or 5 D), which I have not ventured to include in the above category, may yet suffer no detriment whatever from a considerable amount of near work. The natural and quite justifiable dread of the evil effects of near work on myopia has, in my opinion, led some ophthalmic surgeons to undue pessimism, and in some cases to serious and unnecessary interference I have had cases of with children’s education. children of 11 or 12 years of age, with 3 or 4 dioptres of myopia, whose parents have been warned of the direst consequences unless they take the children away from school for two or more years and practically allow them to do no near work. In my opinion in most cases of low myopia a reasonable amount of near work, carried out under the best conditions and with proper precautions as to correction of refractive errors (especially astigmatism), good lighting, proper working distance, and strict attention to general health, does no harm at all. It is even doubtful whether it has any appreciable effect in increasing the rate of development in cases which are truly progressive. Nevertheless, of course each case must be periodically examined at short intervals and near work restricted if increase is at all rapid. So far as the eyes themselves and vision are concerned no deleterious consequences are likely to accrue even if cases of developmental myopia are not corrected at all. Such patients may get headaches, &c., if there is anisometropia or astigmatism, but not if both eyes have the same amount of myopia, and there is no astigmatism. I think the same applies to cases of low myopia which more doubtfully belong to the developmental and stationary I regard it, however, as of the greatest .group. importance that these children should wear their distance corrections, and wear them constantlynot specially in the interests of their eyes, but in the interests of their mental development. For children with even low degrees of uncorrected myopia cannot be expected to take a normal interest in their surroundings since they cannot see distant objects as clearly as their fellows. Their mental horizon is constricted, they tend to become unduly introspective, and they are thrown more’ and more into finding their interest in reading and near work, so that it becomes more difficult -than ever to restrict such work. It is
a
scarcely
1 See Brit. Med. Jour., 1928, ii., 205 ;
ibid., 1928, ii., 287.
Fergus, Freeland:
.
797
Many patients with moderate degrees of myopia poisoned with deadly nightshade or gored by mad are perfectly happy when using their distance correcbulls, children too good for this world might succumb tions for all purposes. They are thus placed as to fevers or simply fade away, but their little nightnearly as possible in the condition of emmetropes. shirts were never stained with the " blood-red spots " which bespattered the "glittering fan " of Ethel But this does not apply to all cases, especially if the and must beare Churchill.1 If consumption had been at all common engaged-as many are, patients in childhood a century ago, Little Nell and Paul in prolonged near work. In these cases they are much Dombey need not have declined in so unscientific a happier with a weaker correction for near work. manner. The treatment for patients with high degrees of Improved methods of diagnosis have enabled myopia has been the subject of much thought and us to recognise many forms of pulmonary tuberculosis in childhood previously unknown, but it has only care, and great advances have been made in recent establishment of has The classes confirmed clinical and lay observation in. proving myope years. undoubtedly been a step in the right direction and the rarity of phthisis in the early years of life. has had an undeniably beneficial effect. At the same RARITY OF OTHER FORMS OF PULMONARY time it has been by no means free from the enthuTUBERCULOSIS IN CHILDHOOD siasm which outruns discretion. Many of these It is often assumed that though phthisis in childpatients are advised to adopt a regime and mode of life which is as ill-judged as to advise a poor patient hood may be rare, milder manifestations of pulmonary tuberculosis are common, and that by the early to winter on the Riviera. Are we really quite so certain of the data upon which we found our counsels recognition of certain stigmata which indicate of perfection as we think we are ?‘ I think that in incipient disease, graver developments may be cases of progressive myopia the evidence is overprecluded. We are asked to believe that adolescent whelming that near work, especially when prolonged phthisis can be prevented by the adequate treatment of children who have been quaintly described as or carried out under unsatisfactory conditions, tends to aggravate the disease-for these are cases of pretuberculous. This is not so. Pulmonary tuberdisease, therein differing from what I have called culosis is not often the cause of delicacy in childhood developmental myopia. I am entirely in support of in this country. The most meticulous examination the principles underlying the methods adopted in of the delicate child will rarely reveal any evidence _myope classes, but I am also convinced that in many of tuberculosis save that supplied by a positive cases lack of judgment is shown in pushing these reaction to skin tests, a reaction which merely proves principles to their logical conclusion. We have to that the child has been the subject of a primary face,the fact that many high myopes are condemned, infection, and that its tissues are hypersensitive to ipso facto, to spend much or most of their working tuberculin. We do not even know whether allergy hours doing near work, and we cannot deny that implies increased susceptibility, relative immunity, in many respects they are specially adapted to or neither. A " follow-up " of child " suspects " perform this type of work. Moreover, large numbers through the danger years of adolescence would do so for many years without disaster. Many such probably show a percentage of tuberculosis, little, if any, greater than might be found in a " noncases settle down in early adult life to a degree of indeed of shows myopia-often high degree-which suspect " group drawn from the same social class little or steadily diminishing rate of increase. Each and circumstance. There is no definite evidence that primary infections which do not produce case must be considered on its merits (or demerits), general health, social status, and occupational demonstrable lesions have any ill-effect upon a child’s opportunities must be evaluated, and a sane com- health. But though pulmonary tuberculosis is unpromise arrived at which errs neither on the side of common in childhood, the disease cannot be relegated "
"
.
idealism
nor
to the class of medical curiosities. Failure to recognise it may be attended with disastrous consequences, and a knowledge of its varieties and of the evidence upon which a correct diagnosis depends is essential if needless fears are to be allayed or incipient disease arrested.
recklessness.
CLINICAL MANIFESTATIONS OF
PULMONARY TUBERCULOSIS IN CHILDHOOD BY W. BURTON WOOD, M.D. M.R.C.P. LOND.
CAMB., .
PULMONARY TUBERCULOSIS THE ESSEX COUNTY COUNCIL
(WITH PHTHISIS is
ILLUSTRATIONS ON
TO
PLATE)
of the rarest of the diseases of it is improbable that the disease was ever common in the early years of life it is not very easy to understand the fear of consumption in childhood, which still prevails among the laity and even to some extent in the profession. The pathos of consumption in adolescence has been fully exploited by novelists, but even the Victorian writer, who did not scruple to employ the death-bed of a child as a means to evoke the flow of tears upon which his income depended, was obliged to find some other means than consumption when disposing of his child victims. Disobedient children might be
childhood,
and
one as
In diagnosis we have to depend almost entirely the X ray picture of the chest. Symptoms are not distinctive. The history of coughs, malaise, and
on
PHYSICIAN TO THE CITY OF LONDON HOSPITAL FOR DISEASES OF THE HEART AND LUNGS ; CONSULTING PHYSICIAN FOR
PARAMOUNT IMPORTANCE OF RADIOLOGY IN DIAGNOSIS
malnutrition
are
frequently given- when a delicate
child is brought for examination. They may even be due to a digestive disturbance wholly unconnected with the lungs. Sweating, a symptom of no diagnostic significance, is the one to which maternal solicitude generally attaches chief importance-a curious reminder how short a time separates us from the days when a complete absence of bedroom ventilation was responsible for drenching sweats in
dying consumptives. Physical signs
are
notoriously
unreliable in the examination of tuberculous patients, and in childhood they are perhaps even less helpful than they are in later years. Thus X ray examination of the chest should be made whenever a history of contact with infection suggests that delicacy may be associated with a tuberculous infection, and to exclude the possibility of such an infection when no other cause for a persistent malaise is apparent.
galvanometer has played an increasing part in the practice of medicine. With the introduction of the galvanometer there followed a period of intensive investigation of all forms of abnormal rhythms with the result that the clinical picture of these
vagaries became so sharply defined that it was possible in most instances to make an accurate diagnosis without resort to the galvanometer. In a sense the electrocardiogram, so far as the arrhythmias are concerned, had played its part as an instrument of precision. Subsequently for some years, apart from research work, the electrocardiograph was employed clinically for teaching purposes and in the investigation of the less obvious and rarer forms of cardiac disorders. A new era began with the recognition of the peculiar and specific changes in the electrocardiogram associated with coronary infarction. Attention was increasingly focused on the myocardium and on lesions of the coronary arteries. This has stimulated further research and the electrocardiograph has proved its value in the investigation and determination of the integrity of the myocardium. It was clear that in it we possessed an instrument which could help in assessing the degree of the myocardial damage and recording the phases of recovery. With its aid the diagnosis of a typical case of coronary thrombosis has been placed on a sure basis and we are now in a position comparable to that in regard to the arrhythmias in which an electrocardiogram has become almost redundant. Unfortunately this stage has not yet been reached in the atypical and aberrant forms. Here we are still dependent on the machine for diagnosis and corroboration. Nevertheless, even in this more obscure field, knowledge is growing, facts are being accumulated, and the electrocardiograph is steadily guiding us to a clearer conception of the clinical results of coronary disease. REFERENCES
1. Herrick, J. B.: Jour. Amer. Med. Assoc., 1912, lix., 2015. 2. : Ibid., 1919, lxxii., 387. ,, 3. Libman, E.: Med. Record (New York), 1916, lxxxix., 124. 4. Levine, S. A. and Tranter, C. L. : Amer. Jour. Med. Sci., 1918, clv., 57. 5. Pardee, H. E. B. : Arch. Internal Med., 1920, xxvi., 244. 6. Longcope, W. T.: Illinois Med. Jour., 1922, xli., 186. 7. Wearn, J. T.: Amer. Jour. Med. Sci., 1923, clxv., 250. 8. Levine and Brown, C. L.: Medicine Monographs, 1929, vol. xvi. 9. Wolff, L., and White, P. D.: Boston Med. and Surg. Jour., 1926, cxcv., 13. 10. Christian, H. A. : North Western Medicine, December, 1925. 11. Gibson, A. G. : THE LANCET, 1925, ii., 1270. 12. McNee, J. W. : Quart. Jour. Med., 1925-1926, xix., 44. 13. Parkinson, J., and Bedford, D. E.: Heart. 1928, xiv., 195. 14. ,, ,, ,, : THE LANCET, 1928, i., 4. ,, 15. Parkinson : Brit. Med. Jour., 1932, ii., 549. 16. Lewis, T.: Arch. Internal Med., 1932, xlix., 713. 17. Davis, N. S.: Jour. Amer. Med. Assoc., 1932, xcviii., 1806. 18. Levine and Brown : Medicine, 1929, viii., 280. 19. Bell, A., and Pardee, : Jour. Amer. Med. Assoc., 1930, xciv., 1555. 20. Pardee : Amer. Jour. Med. Sci., 1925, clxix., 255. 21. Smith, F. M.: Arch. Internal Med., 1923, xxxii., 497. 22. Levy, R. L.: Ibid., 1931, xlvii., 1. 23. Holland, C. W., and Levine: Jour. Amer. Med. Assoc. (Abstract), 1932, xcviii., 1943. 24. Wilson, W. J. : Ann. Clin. Med., 1926, v., 238. 25. Pardee : Arch. Internal Med., 1930, xlvi., 470. 26. Wolferth, C. C., and Wood, F. C. : Amer. Jour. Med. Sci., 1932, clxxxiii., 30 ; Med. Clin. N. Amer., 1932, xvi., 161 ; Arch. Internal Med., 1933, li., 771. 27. Lewis: Brit. Med. Jour., 1909, ii., 1528 ; THE LANCET, 1909, ii., 1820 ; Heart, 1909-1910, i., 306. 28. Lewis: Mechanism of the Heart-Beat. London, 1911. ,,
DEVELOPMENTAL MYOPIA AND THE TREATMENT OF MYOPES BY SIR JOHN PARSONS, C.B.E., M.B., D.SC. LOND., F.R.C.S. ENG., F.R.S. CONSULTING SURGEON TO THE ROYAL LONDON OPHTHALMIC HOSPITAL ; CONSULTING OPHTHALMIC SURGEON TO UNIVERSITY COLLEGE HOSPITAL
THE state of static refraction of an eye is the result of the integration of a large number of variables. In most text-books too much stress is laid upon the length of the eye. It has been shown by actual measurements that the length of the emmetropic eye may vary by as much as 2 mm., and the radius of curvature of the cornea from 7 to 8-5 mm. Compensating factors are the curvatures of the refracting surfaces, the indices of refraction of the media, and the position of the lens. As an example, a buphthalmic eye may be as much as 31 mm. in length from the anterior surface of the cornea to the retina, and yet not be myopic. Myopia may be due theoretically to any of the following conditions :-
Abnormally increased length myopia). 1.
of
the
eye
curvature of the refracting : myopia): (a) too strong curvature (curvature cornea; (b) too strong curvature of one or both 2. Abnormal
(axial
surfaces of the surfaces
of the lens. 3. Abnormal refractive indices of the media (index myopia):(a) too high index of the cornea or aqueous ; (b) too high total index of the lens, due to too high index of the nucleus or too low index of the cortex ; (c) too low index of the vitreous. 4. Displacement forwards of the lens. 5. A combination of the above factors.
The
development of the eye is such that the normal is born with hypermetropic eyes. During the baby first years of life the various factors change in such a manner that the eye becomes less hypermetropic and may become perfectly emmetropic. Statistics of the incidence of emmetropia and ametropia at different ages are very unsatisfactory owing to several reasons. The estimates of different observers are not always reliable or strictly comparable ; but the chief source of ambiguity is the valuation for statistical purposes which should be allotted to various degrees of astigmatism. From the statistical point of view, however, the generalisation that the normal eye is hypermetropic at birth and tends constantly during the early years of life towards a condition of diminished hypermetropia may be regarded
as
true.
THE NORMAL AND THE IDEAL NORMAL
The statistical investigation of any variable commences with the determination of its frequency distribution. Thus, if in an adult male population the numbers of individuals are plotted against their heights, a " cocked hat " curve is obtained which almost exactly coincides with the theoretical ideal symmetrical frequency-distribution curve. In such a curve the criterion of absolute normality is given by the maximum ordinate, but slight differences on each side of the maximum cannot be regarded as pathologically abnormal. In very many biological and other examples-e.g., the weight of adult malesthe distribution curve is asymmetrical or skew, the greater frequencies lying towards one or other end of the range. Owing to the higher incidence of hypermetropes at birth we should expect the frequency
796 distribution of variations in refraction to present such a skew deviation curve. In all such "populations " large numbers of individuals approximate nearly to the statistical ideal normal as judged by the maximum ordinate of the frequency curve. Apart from the statistical examination there is often no more reason for regarding these as less normal than the ideal normal. In the case of the refraction of the eye, on the other hand, the normal has not been arrived at by statistical methods, but by quite other considerations. Emmetropia is the condition in which parallel rays are brought to a focus on the retina ; optically considered, it is an ideal normal. Moreover, it is one to which large numbers of individuals conform, and which must therefore deviate little from the statistical normal. The cases are rare in which nature attains the optimum invariably, as in the angle of the honeycomb cell; and emmetropia is certainly not one of these cases. Owing to the prolonged immaturity of the young of primates, and especially man, the teleological argument would lead one to expect that human vision is specially adapted to the requirements of early and middle adult life. During this period accommodation is active, and the moderate hypermetrope is at least as well adapted to everyday life as the emmetrope. The fact that practically all mammals are hypermetropic would lead one to expect that their statistical ideal normal is definitely hypermetropic, and it would seem that in man the frequency curve has shifted towards the emmetropic condition. Too much stress cannot, however, be placed on this argument, owing to the absence of a fovea in lower mammals and the differences in their vision and mode of life. It would be interesting to know whether the lower primates are ever emme-
tropic .
or
myopic.
it would seem certain that from the biological point of view we should expect to find many examples of permanent low hypermetropia, and a few-but perhaps not negligible-examples of permanent low myopia. Such cases are fundamentally no more pathologically abnormal than short men or tall men. My own experience, chiefly derived from private cases carefully watched over a number of years, is that cases of "stationary" myopia conforming to this hypothesis are not very uncommon. One meets with children with very low degrees of myopia which increase up to a maximum of 1 or 2 dioptres during the growing period, and then remain quite stationary. As a rule their fundi are perfectly normal, and there are no myopic crescents. Of course it is impossible to be certain that any such child belongs to this group of "’ developmental myopia," since every progressive myope must pass through the stage of low myopia. Certainly some such cases remain stationary for many years. In any
case
VISUAL CAPACITY
If, as suggested above, there has been a tendency iri the mammalia for the maximum of the frequency curve to shift towards low hypermetropia or emmetropia, some enhancement of this tendency might be anticipated as the result of civilised conditions. If so, it would not be surprising for cases of low myopia to occur from this cause. Important as perfect visual acuity is, I am of opinion that its value is not infrequently over-estimated. A man’s visual efficiency depends not only on his visual acuity, but also upon his field of vision, rapidity of accommodation and adaptation, and many other factors which can be conveniently summed up in
the term ’visual capacity.1 Even when a man’s visual capacity has diminished his working efficiency for his job may be little impaired, owing to the compensating effects of acquired technical skill. This fact was conclusively proved in certain cases by an investigation carried out by the Committee on the Physiology of Vision of the Medical Research Council for the Royal Navy. It is a well-known fact that a good game shot remains good long after his visual capacity has materially declined. MYOPIA AND NEAR WORK
remarkable fact that the eye, which can be regarded as having been evolved for the express purpose of adaptation to the needs of civilised life, is yet capable of fulfilling them with relatively There are, little detriment or even discomfort. indeed, many occupations in which a low degree of per se, is a real asset. If there are cases of myopia, " stationary " myopia such as I have suggested, they are eminently suited for such occupations, since there is no reason to suppose that they would suffer in any way. I think the evidence is in favour of the view that degrees of myopia (e.g., of 4 or 5 D), which I have not ventured to include in the above category, may yet suffer no detriment whatever from a considerable amount of near work. The natural and quite justifiable dread of the evil effects of near work on myopia has, in my opinion, led some ophthalmic surgeons to undue pessimism, and in some cases to serious and unnecessary interference I have had cases of with children’s education. children of 11 or 12 years of age, with 3 or 4 dioptres of myopia, whose parents have been warned of the direst consequences unless they take the children away from school for two or more years and practically allow them to do no near work. In my opinion in most cases of low myopia a reasonable amount of near work, carried out under the best conditions and with proper precautions as to correction of refractive errors (especially astigmatism), good lighting, proper working distance, and strict attention to general health, does no harm at all. It is even doubtful whether it has any appreciable effect in increasing the rate of development in cases which are truly progressive. Nevertheless, of course each case must be periodically examined at short intervals and near work restricted if increase is at all rapid. So far as the eyes themselves and vision are concerned no deleterious consequences are likely to accrue even if cases of developmental myopia are not corrected at all. Such patients may get headaches, &c., if there is anisometropia or astigmatism, but not if both eyes have the same amount of myopia, and there is no astigmatism. I think the same applies to cases of low myopia which more doubtfully belong to the developmental and stationary I regard it, however, as of the greatest .group. importance that these children should wear their distance corrections, and wear them constantlynot specially in the interests of their eyes, but in the interests of their mental development. For children with even low degrees of uncorrected myopia cannot be expected to take a normal interest in their surroundings since they cannot see distant objects as clearly as their fellows. Their mental horizon is constricted, they tend to become unduly introspective, and they are thrown more’ and more into finding their interest in reading and near work, so that it becomes more difficult -than ever to restrict such work. It is
a
scarcely
1 See Brit. Med. Jour., 1928, ii., 205 ;
ibid., 1928, ii., 287.
Fergus, Freeland:
.
797
Many patients with moderate degrees of myopia poisoned with deadly nightshade or gored by mad are perfectly happy when using their distance correcbulls, children too good for this world might succumb tions for all purposes. They are thus placed as to fevers or simply fade away, but their little nightnearly as possible in the condition of emmetropes. shirts were never stained with the " blood-red spots " which bespattered the "glittering fan " of Ethel But this does not apply to all cases, especially if the and must beare Churchill.1 If consumption had been at all common engaged-as many are, patients in childhood a century ago, Little Nell and Paul in prolonged near work. In these cases they are much Dombey need not have declined in so unscientific a happier with a weaker correction for near work. manner. The treatment for patients with high degrees of Improved methods of diagnosis have enabled myopia has been the subject of much thought and us to recognise many forms of pulmonary tuberculosis in childhood previously unknown, but it has only care, and great advances have been made in recent establishment of has The classes confirmed clinical and lay observation in. proving myope years. undoubtedly been a step in the right direction and the rarity of phthisis in the early years of life. has had an undeniably beneficial effect. At the same RARITY OF OTHER FORMS OF PULMONARY time it has been by no means free from the enthuTUBERCULOSIS IN CHILDHOOD siasm which outruns discretion. Many of these It is often assumed that though phthisis in childpatients are advised to adopt a regime and mode of life which is as ill-judged as to advise a poor patient hood may be rare, milder manifestations of pulmonary tuberculosis are common, and that by the early to winter on the Riviera. Are we really quite so certain of the data upon which we found our counsels recognition of certain stigmata which indicate of perfection as we think we are ?‘ I think that in incipient disease, graver developments may be cases of progressive myopia the evidence is overprecluded. We are asked to believe that adolescent whelming that near work, especially when prolonged phthisis can be prevented by the adequate treatment of children who have been quaintly described as or carried out under unsatisfactory conditions, tends to aggravate the disease-for these are cases of pretuberculous. This is not so. Pulmonary tuberdisease, therein differing from what I have called culosis is not often the cause of delicacy in childhood developmental myopia. I am entirely in support of in this country. The most meticulous examination the principles underlying the methods adopted in of the delicate child will rarely reveal any evidence _myope classes, but I am also convinced that in many of tuberculosis save that supplied by a positive cases lack of judgment is shown in pushing these reaction to skin tests, a reaction which merely proves principles to their logical conclusion. We have to that the child has been the subject of a primary face,the fact that many high myopes are condemned, infection, and that its tissues are hypersensitive to ipso facto, to spend much or most of their working tuberculin. We do not even know whether allergy hours doing near work, and we cannot deny that implies increased susceptibility, relative immunity, in many respects they are specially adapted to or neither. A " follow-up " of child " suspects " perform this type of work. Moreover, large numbers through the danger years of adolescence would do so for many years without disaster. Many such probably show a percentage of tuberculosis, little, if any, greater than might be found in a " noncases settle down in early adult life to a degree of indeed of shows myopia-often high degree-which suspect " group drawn from the same social class little or steadily diminishing rate of increase. Each and circumstance. There is no definite evidence that primary infections which do not produce case must be considered on its merits (or demerits), general health, social status, and occupational demonstrable lesions have any ill-effect upon a child’s opportunities must be evaluated, and a sane com- health. But though pulmonary tuberculosis is unpromise arrived at which errs neither on the side of common in childhood, the disease cannot be relegated "
"
.
idealism
nor
to the class of medical curiosities. Failure to recognise it may be attended with disastrous consequences, and a knowledge of its varieties and of the evidence upon which a correct diagnosis depends is essential if needless fears are to be allayed or incipient disease arrested.
recklessness.
CLINICAL MANIFESTATIONS OF
PULMONARY TUBERCULOSIS IN CHILDHOOD BY W. BURTON WOOD, M.D. M.R.C.P. LOND.
CAMB., .
PULMONARY TUBERCULOSIS THE ESSEX COUNTY COUNCIL
(WITH PHTHISIS is
ILLUSTRATIONS ON
TO
PLATE)
of the rarest of the diseases of it is improbable that the disease was ever common in the early years of life it is not very easy to understand the fear of consumption in childhood, which still prevails among the laity and even to some extent in the profession. The pathos of consumption in adolescence has been fully exploited by novelists, but even the Victorian writer, who did not scruple to employ the death-bed of a child as a means to evoke the flow of tears upon which his income depended, was obliged to find some other means than consumption when disposing of his child victims. Disobedient children might be
childhood,
and
one as
In diagnosis we have to depend almost entirely the X ray picture of the chest. Symptoms are not distinctive. The history of coughs, malaise, and
on
PHYSICIAN TO THE CITY OF LONDON HOSPITAL FOR DISEASES OF THE HEART AND LUNGS ; CONSULTING PHYSICIAN FOR
PARAMOUNT IMPORTANCE OF RADIOLOGY IN DIAGNOSIS
malnutrition
are
frequently given- when a delicate
child is brought for examination. They may even be due to a digestive disturbance wholly unconnected with the lungs. Sweating, a symptom of no diagnostic significance, is the one to which maternal solicitude generally attaches chief importance-a curious reminder how short a time separates us from the days when a complete absence of bedroom ventilation was responsible for drenching sweats in
dying consumptives. Physical signs
are
notoriously
unreliable in the examination of tuberculous patients, and in childhood they are perhaps even less helpful than they are in later years. Thus X ray examination of the chest should be made whenever a history of contact with infection suggests that delicacy may be associated with a tuberculous infection, and to exclude the possibility of such an infection when no other cause for a persistent malaise is apparent.