Blind Experiment

BLIND EXPERIMENT, a control research conducted in biochemical and other analyses to determine the magnitude of error, which is a consequence of contamination of reagents, inaccuracy of instruments and measuring vessels, the effect of temperature on the reaction, etc. The blind experiment is conducted in all respects exactly like the main analysis, with the exception that the substance being investigated is replaced by some other substance that definitely does not contain the element being determined; in biochemical analyses - usually by distilled water. The figures obtained in the B. e. are subtracted from the results of the main research. Particular importance is attached to the careful conduct of the B. e. in microanalyses of blood, tissues, urine, etc., which have now become widespread in the clinic for diagnostic purposes. In these analyses, the magnitude of error due to contamination of reagents, insufficient purity of the water used for dilution of reagents and the substance being investigated can reach such a magnitude that failure to take it into account can completely distort the results of the main analysis and deprive them of any value. Thus, for example, in the microanalysis of calcium content in blood, the main source of error may be the presence of calcium in the water used for diluting the blood and preparing the reagents. Usually, about 0.1 cm³ of a ¹/₁₀₀ solution of KMnO₄ is consumed in the final titration in the blind experiment; in the main research, however, if 1 cm³ of blood was taken for determination - 0.5-0.8 cm³ of a ¹/₁₀₀ solution of KMnO₄. The calcium content in the water thus constitutes about 20% of the amount of calcium in the blood being investigated, which in the absence of B. e. would lead to an error of the same order. If the data obtained in the B. e. exceed a certain definite value for a given analysis, then in general the reagents used for the analysis cannot be used, and it is necessary to replace them with others, purer ones. B. e. must be repeated each time at least one reagent used in the analysis is replaced by another. Under the conditions of conducting microchemical analyses, this means that B. e. must be practically conducted for each given series of investigations or even for each individual investigation. BLINDNESS. From a purely scientific point of view, a person is called blind who is deprived of objective light perception. Emphasizing the objectivity of light perception, we mean those subjective light phenomena which are so common in blind eyes. Thus, already one who distinguishes light and shadow, and even more so one who can distinguish objects or count fingers at the nearest distance from the eye, theoretically should not be considered blind. But practically in life one has to consider blind not only people deprived of light perception, but also those who, because of the state of their vision, are incapable of any occupation requiring vision. In addition to the scientific concept of B., the concept of civil B. is thus established. Life introduces, it is true, some correction into the concept of civil B., because we see how, after appropriate training, people completely deprived of vision begin not so rarely to work in enterprises where vision is absolutely required (see Blind). But such cases in the general mass of the blind are still still exceptions, and until these exceptions become the rule, the concept of civil B. remains in force. It goes without saying that when speaking of civil B., one implies B. in both eyes and moreover incurable B. From a scientific point of view, the study of one-sided B. and curable B. has unquestionable interest, but practically one has to deal primarily with bilateral incurable civil B. The latter stands next to the so-called weakness of vision, which can also greatly reduce the working capacity of people suffering from it. When establishing boundaries between civil B. and weakness of vision, subjectivism of individual authors can naturally occur. In answering the question what visual acuity should be considered the upper limit of civil B., the opinions of authors differ somewhat, though not sharply. Katz proposes to distinguish 3 degrees of B.: 1) absolute B., when there is no light perception; 2) qualitative light perception, when light and shadow are distinguished, and 3) quantitative light perception, when visual acuity is equal to counting fingers at the face itself. Tsegender also divides B. into 3 degrees: 1) absolute B., 2) with slight light perception and 3) with good light perception, when large objects are distinguished in their outlines. Schmidt-Rimpler classifies as blind those who can count fingers at a distance of ²/₃ m; those who count fingers at a greater distance are already classified as poorly seeing, but not blind. Magnus agrees with the opinion of Schmidt-Rimpler. According to Fuchs, to whom Hirsch joins, one can consider blind even one who counts fingers at a distance of 1 m, and Trüke includes among the blind even persons having one tenth of normal vision; but such a broad scale of B. can hardly be considered correct. Pablazek proposed to introduce in addition to light perception the criterion of color perception for determining B., but this proposal was rejected by the vast majority of authors as not introducing anything essentially new and at the same time complicating the question of determining B. The doctrine of color blindness, or Daltonism (see), has great scientific interest, but not from the point of view of defining the concept of blindness. There were attempts to approach the definition of B. from another side, proposing in addition to visual acuity a new criterion in the form of the ability or inability of a blind person to orient himself in an unfamiliar place. This criterion, put forward by Emmert, met with different attitudes among other authors. Part of them (Schmidt-Rimpler, Magnus, etc.), criticizing it, point out that often and completely blind people orient themselves well in unfamiliar places, using hearing, touch, etc., and that, on the other hand, the specified criterion does not give definite grounds for distinguishing B. from weakness of vision, because people with weak vision, for example with high myopia, sometimes cannot walk alone on any fairly lively streets. Another part of the authors (Fuchs and others) considers the inability to orient oneself a good criterion of B., because such persons are usually unemployable because of this. Fuchs attempts to link both criteria, pointing out that with the proposed limit of visual acuity in a blind person - counting fingers at a distance of 1 m - this blind person stands on the border of the ability to orient himself. Finally, there were individual attempts to individualize the criterion of B. for separate professions. Thus, Seidelmann proposed to consider blind one who cannot engage in the profession he has been engaged in up to now. But with such a criterion the concept of B. becomes too broad and vague, and we must equally consider blind both people completely deprived of light perception and those who, with a significant decrease in central visual acuity, have preserved peripheral vision and because of this not only do not need outside help but can also perform some work. We can and must, of course, when determining the degree of decrease in working capacity, take into account the fact that a person cannot work in his profession, but such a criterion cannot be the basis for defining the concept of B. The majority of Russian authors working on the problems of B. stand on the above-mentioned point of view of Schmidt-Rimpler. In any determination of residual visual acuity, we must keep in mind that it must be determined under normal daylight illumination, because, on the one hand, too bright illumination allows distinguishing objects at a greater than usual distance, and on the other hand, with insufficient, twilight illumination, people suffering from night blindness, or hemeralopia (see), see poorly. The second most important question in the study of B. is the question of its etiology. Unfortunately, sources for studying this question are rather few. All official censuses of the blind, conducted not by physicians, cannot obviously serve as sources of information on this question. There remain, therefore, only the so-called mass examinations of the population, conducted by physicians, and reports of physicians and medical institutions, which also include information about B. The disadvantage of the second source, as Prof. Golovin rightly notes, is that information about B. is collected on material, so to speak, artificially selected from the population, and therefore the distribution of causes of B. obtained in this way should differ from the true distribution of these causes in the given population. But the more material collected, the less noticeable will be individual fluctuations and the more clearly the general regularities will appear. In our USSR, both before and after the revolution, various authors have presented large figures on the question of the etiology of B. on the basis of data from medical institutions. Unfortunately, to this day no uniform and generally accepted classification of the causes of B. has been developed.

Two principles are usually used as the basis for classifying the causes of B.: 1) the anatomical principle, in which the main consideration is given to the anatomical changes observed in the blind eye, for example, corneal opacity, pupil closure, atrophy of the eyeball, etc.; 2) the second principle is the determination of those diseases, local and general, that led to blindness. As early as 1883, Magnus proposed a classification of the causes of B., in which all causes are divided into 4 groups: 1) congenital B.; 2) acquired B. due to idiopathic, independent eye diseases; 3) acquired B. due to injuries to the eyes and head; 4) acquired B. due to diseases caused by general diseases of the body. In each of these groups, Magnus arranged the individual forms of diseases according to the anatomical changes present in the eye. Thus, the first group of congenital B. includes: anophthalmos, micro- and macrophthalmos, congenital adherent cataract, congenital choroiditis, congenital atrophy of the optic nerve, pigmentary retinitis, congenital atrophy of the retina, congenital anomalies of the cornea, and congenital tumors. The second group includes: ophthalmia neonatorum and in adults, trachoma, diphtheritic conjunctivitis, diseases of the cornea, iritis, cyclitis, irido-choroiditis, choroiditis in myopia, acquired pigmentary retinitis, retinitis with hemorrhages, neuroretinitis, detachment of the retina, glaucoma, independent atrophy of the optic nerve, tumors of the eye and surrounding parts. The third group includes: direct injuries to the eye, unsuccessful operations, injuries to the head and sympathetic disease of the second eye. Finally, the fourth group includes diseases of the eye in syphilis, gonorrhea, scrofula, meningitis; atrophy of the optic nerve: in diseases of the brain and spinal cord, after vomiting, hemorrhage, erysipelas, epilepsy, dysentery, mental diseases; changes in the eye in kidney disease, after typhus, measles, scarlet fever, smallpox, other exanthems, heart diseases, childbirth and pregnancy, on the basis of poisonings and diseases of the orbit.

Pokrovsky cites this classification because it formed the basis for a number of other studies on the etiology of B., and its influence was long felt in the works of some authors. In the subsequent criticism of Magnus's classification, the change in views on the etiology of eye diseases in general is reflected. The main group of his classification—idiopathic eye diseases—became increasingly linked to general diseases of the body. On the other hand, general intrauterine diseases of the fetus (syphilis, etc.) and in the origin of the first group—congenital B.—were increasingly taken into account. It became increasingly clear that, on the one hand, the anatomical principle, so important in Magnus's classification, does not indicate a specific etiology of B., because, for example, diseases of the cornea or iris can arise from the most diverse causes. On the other hand, the same cause can cause the most diverse anatomical changes, for example, tuberculosis and syphilis can cause changes in the cornea, all parts of the uvea, retina, optic nerve, etc. Therefore, the attempts of other authors to base themselves in compiling a classification only on the basic etiology of the disease that led to B. are quite understandable. For example, Fik proposed such a classification: congenital B., ophthalmia neonatorum and in adults, trachoma, diphtheria, myopia, glaucoma, new growths of the eye, injuries and sympathetic inflammation, poisonings, smallpox, measles, scarlet fever, typhus, postpartum diseases, syphilis, tuberculosis and scrofula. Here, as we see, the anatomical principle is completely absent from the classification, but in the first place, such a classification undoubtedly does not cover all the diversity of causes of B.; in the second place, it is well known that very often there are cases where it is difficult to establish the true cause of B. with even some probability, and one can only note the presence of certain anatomical changes. We very often see, for example, B. from corneal opacities, but we cannot establish, either from the nature of the changes or from the anamnesis, what specific causes caused such opacities. Therefore, according to the correct indication of Prof. Golovin, 'one should not neglect the anatomical forms of B., but should combine the table of anatomical changes with the table of etiological factors'.

In the diagram of the main causes of B. identified by Prof. Golovin in pre-revolutionary Russia, there are: congenital B., ophthalmia neonatorum and in adults, trachoma, diseases of the cornea, diseases of the vascular tract, glaucoma, diseases of the optic nerve and retina, diseases of the central nervous system, syphilis, smallpox, injuries to the eye. We find approximately the same classification of the causes of B. in the most extensive material on statistics of B. according to data from medical institutions of the former Guardianship of the Blind. This classification was proposed at one time by prominent St. Petersburg ophthalmologists led by Prof. Belliarminov. The classifications by which the causes of B. were distributed in the statistics of medical institutions of other departments of pre-revolutionary Russia differed little. Such uniformity in the classification of the causes of B. in a large number of medical institutions undoubtedly had important significance, as it made it possible to compare data from individual medical institutions and to calculate average figures from them (Golovin, Pokrovsky, etc.). Analysis of these huge figures proved (Pokrovsky) that in them, according to the law of large numbers, the general regularities are indeed reflected. But one cannot fail to see that these classifications are, first, too simplified and too general, and second, that in them more than half of the purely anatomical principle is preserved. It is therefore quite understandable that both here and abroad attempts at new classifications of the causes of B. do not cease. One of such interesting attempts is the classification proposed by Marets at the last international ophthalmological congress in Madrid in 1933. The author tries to build such a classification that would give at the same time an idea of both the anatomical changes and those local and general diseases that served as the cause of such changes.

In a special table divided into cells, the author arranges along the coordinate axes: in the vertical direction—disorders of the refractive media of the eye, retina, visual pathways, and centers, and in the horizontal direction—eye diseases or general diseases that caused the above-mentioned disorders. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes.

In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes.

In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes.

In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes.

In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes. In the vertical direction, the author places the following groups: A. The eyeball as a whole B. Cornea C. Anterior chamber D. Iris and E. Lens F. Vitreous body G. Vascular and H. Retina I. Optic nerve J. Without visible changes.

Nephritis ?Heart diseases Embolisms Hemorrhages Elevated blood pressure Other Various anemias Blood loss Adjacent to the orbit Sinuses Nervous system Blood Nutrition and internal secretion Intoxications Diabetes Other Alcohol and tobacco Medications Other Chronic XIII. Infections Acute XIV. Parasitic diseases Cysts Cysticercus Other Syphilis Leprosy Other Diphtheria Measles Scarlet fever Smallpox Influenza Other XV. Congenital diseases XVI. Unclassified XVII. Indeterminate When classifying each case of blindness, it is marked in the cell located at the intersection of the corresponding horizontal and vertical rows. For example, a leucoma, if it resulted from purulent keratitis, finds its place at the intersection of B vertically and II horizontally; or atrophy of the optic nerve, if it is a consequence of glaucoma, then at the intersection of J vertically and I horizontally, and if it is a result of tabes, then at the intersection of J vertically and VII horizontally, etc. Marke correctly emphasizes the need to introduce a uniform international classification of the causes of blindness. So far this has not existed: so far each country, and moreover, almost every author in a separate country had peculiarities in the classification of blindness. As a result, it was extremely difficult, and sometimes impossible, to compare data from different countries and individual authors and draw conclusions. And how necessary this is both theoretically and practically, is self-evident. Therefore, one cannot but welcome Marke's attempt. Undoubtedly, amendments and additions will be made to it; one should even insist that such classifications be periodically reviewed at international ophthalmological congresses, but the necessity of their existence in one form or another for a certain period of time is indisputable. The classifications presented above show the numerousness and diversity of the causes of blindness. Individual countries have their own peculiarities in this regard. And in each country, the causes of blindness are not static, but dynamic; some of them lose their significance and then almost disappear, while others re-emerge and grow. For example, in tsarist Russia, smallpox had enormous significance among the causes of blindness, especially among certain national minorities, which is now losing its significance. A noticeable decline in the number of people blinded by trachoma is already evident now, thanks to which before the revolution 21% or more of all blind people lost their sight. New socio-economic and living conditions will soon affect the significance of other causes of blindness. On the other hand, the rapidly growing industry with an influx of new unskilled workers initially led to an increase in trauma and its role as a cause of blindness. But the comprehensive organization of preventive measures with the rationalization of production and the production process in the USSR is now noticeably eliminating this temporary phenomenon, and we see from year to year a decrease in eye trauma as a cause of blindness. The main cause of blindness in pre-revolutionary Russia, according to Prof. Golovin, was: trachoma-21.4%, glaucoma-19.2%, diseases of the cornea-13.5%, smallpox-12.1%, gonorrhea of newborns-4.9%, trauma-3.7%. Such an approximate ratio of the causes of blindness remained, according to Savvaitov, in 1926, only the percentage of trauma increased to 6.56 and the percentages of smallpox decreased to 10.63 and diseases of the cornea to 8.43. But these were average figures for all of Russia, and in its individual regions the significance of individual causes of blindness changed; for example, in the former Volga provinces, as well as in Vyatka, Ufa, Belarus, trachoma came to the forefront among the causes of blindness, in Central Asia--smallpox and glaucoma, in the southwest of European Russia--gonorrhea acquired a certain significance, etc. Post-revolutionary data from Siberia (Kozytsyn), Kazakhstan (Kurlow), the Urals (Chichkanova, Lyubimov), the Middle and Lower Volga region (Batrachenko and Boltyansky), the Central Black Earth region (Pokrovsky and Lurie, Ptashnik), Donbas (Balabonina), Ukraine (Rabkin and Miller), Kuban (Berberov), the North Caucasus region (Volokonenko) show that so far the main causes of blindness remain the same, but shifts and changes are occurring in the significance of individual causes. Smallpox is receding to the background, there is a certain downward shift in trachoma, glaucoma and diseases of the cornea retain their place, there is a slight increase in gonorrhea during the war and post-war period. Data from foreign authors on the etiology of blindness show that in France, according to Trousseau (1902), the main causes of blindness were: glaucoma-19%, gonorrhea of newborns-9.3%, diseases of the cornea-8%, trauma-6%, trachoma-1.9% and smallpox-1.1%. In Germany, according to Hirsch (1902), people went blind from glaucoma-2.4%, gonorrhea of newborns-15%, diseases of the cornea-2.3%, trauma-10.3%, trachoma-4.7%, smallpox-4.3%, or according to Magnus's groups: congenital blindness-13.8%, due to idiopathic eye diseases-40.8%, general diseases-29.5%, injuries-10.3%. Comparing the latest figures with Magnus's own figures-I group-3.8%, II-67.1%, III-18.3% and IV-10.8%,-we see how Hirsch's III group grew at the expense of II and how the percentage of congenital blindness increased. Data from the latest foreign authors confirm that even now gonorrhea of newborns, trauma, atrophies of the optic nerves of various origins and glaucoma occupy a prominent place among the causes of blindness. The percentage of smallpox among the causes of blindness abroad has sharply decreased; according to Axenfeld, it now amounts to only 0.3 among young blind people in Germany, whereas previously it was equal to 35% of all blind people. Trachoma has some significance in Romania (4.9%) and in Hungary. Among our eastern neighbors—the Chinese, according to Chang's data (1930), the main causes of blindness are: diseases of the cornea-34.5%, trachoma-14%, glaucoma-8.9%, syphilis-6.5%, injuries-4.2%. The percentage of congenital blindness in the works of the latest foreign authors is rising high; thus, according to Fritze and Zade (Germany), it is 22 and 18.6, according to Norrie (Denmark)-33, according to Darier (France)-18.4, according to Osborne (USA)-24, according to Suda (Japan)-23.4, etc. This increase in the figure is explained, among other things, by different understandings of congenital blindness; some, together with Magnus, include in this group only those born blind, while others, together with Fuchs, all those blinded by eye diseases that developed on a hereditary basis. The question of blindness in childhood deserves special attention. In pre-revolutionary Russia, the percentage of children among the blind was high—higher than in Western European states. Interestingly, this percentage varied in different provinces of former Russia, and for example, the provinces of Kyiv, Oryol, Tula, Podolia, Voronezh, Kharkov, Ryazan, Poltava, Chernigov, Tambov and some others were distinguished by a particularly high percentage of blind children, both according to census data and according to medical institutions (Pokrovsky). Among the causes that caused such a difference, the main role was played, of course, by the degree of spread in a given province of those diseases that are the main causes of childhood blindness. Such diseases were: smallpox-24.9%, diseases of the cornea-19.8%, gonorrhea of newborns-18.4%, congenital blindness-6.8%, diseases of the central nervous system-5.0%, scrofula-5.0%, measles and scarlet fever-3.9% and injuries-2.7% (Pokrovsky). Abroad, in the etiology of childhood blindness, smallpox plays almost no role and diseases of the cornea and scrofula play a much smaller role, but as a result, the participation of gonorrhea, trauma, diseases of the vascular coat of the eye (7.0%) and the visual-nerve apparatus of the eye (15-19%) is characterized by higher figures. In Russian authors, the figures for the last two groups are significantly lower. Trachoma as a cause of blindness, according to Russian authors, appears later at the border of childhood with adolescence. The most dangerous age in terms of vision loss in children is the age up to 1 year and from 3 to 5 years (Dyakonov, Golovin, Pokrovsky). This is also confirmed by a number of foreign authors. The second age-related rise in the curve of blindness, although smaller than the first, occurs from 20 to 60 years after its decrease with a minimum between 10 and 20 years (Golovin).-Comparing the main causes of blindness in persons of both sexes, one can see that men more often go blind from injuries, diseases of the optic nerve, syphilis, intoxications, while women-from diseases of the cornea, smallpox, trachoma, i.e., adds Prof. Golovin, from causes that are particularly amenable to treatment. The extremely important question of the percentage of preventable blindness is resolved differently by authors of different countries, which is quite understandable, since the causes of blindness, as we have seen, are dynamic and some of them are receding in more cultured countries. In pre-revolutionary Russia, according to Golovin, the percentage of preventable blindness was determined at 59.7 and non-preventable at 40.3. In the post-revolutionary period, Savvaitov gives for the USSR already somewhat lower figures for preventable blindness-56.96%; Berberov in Kuban and Volokonenko in the North Caucasus indicate an even lower percentage-53.8. Abroad the figures are lower: in France, according to Trousseau-43%, according to Truquet-34%; in Germany, according to old Magnus data-40%, according to Fick-41%, according to Hirsch-41.9%; according to more recent data (1926) Fritze-the percentage of absolutely preventable blindness is 31.2 and conditionally preventable-4.6.

The percentage is even lower in cities; thus, according to Uterman, in Cologne it is 20-25. The question of the preventability of the causes of Blindness is closely linked to the question of its prevention, since our prevention is aimed precisely at these causes. When considering individual causes of Blindness, Golovin believes that with proper prevention, Blindness from trachoma, smallpox, and neonatal blennorrhea can be eliminated completely, from diseases of the cornea, syphilis, and injuries-by 50%, from glaucoma-by 33.3%, and from diseases of the vascular tract and congenital Blindness-by 10%. Among foreign authors, Fik differs from Golovin only in regard to glaucoma, where he allows for preventability in 44.4% and congenital Blindness in 33.3%. The latest foreign authors, as we have seen, are even greater optimists in terms of the prevention of Blindness (Freyse, Uterman, Norri, and others). (For the prevention of trachoma, smallpox, and neonatal blennorrhea-see the respective articles.) Diseases of the cornea, with timely and proper treatment, according to Golovin, provide a favorable field for the prevention of Blindness. Prevention of Blindness from glaucoma comes down mainly to early recognition and proper treatment of it (see Glaucoma). Proper treatment of syphilis not only prevents Blindness from it in many cases but is also a measure for the prevention of congenital Blindness in children of syphilitics. Prevention of Blindness from injuries is self-evident and follows along the lines of labor protection. Prevention of Blindness from scrofula is closely connected with the improvement of the economic situation of the population; similarly, institutions for child health protection are also institutions for the prevention of Blindness from scrofula. The situation is much worse in terms of prevention of Blindness from diseases of the vascular coat of the eye and the central nervous system; but here too the etiological approach to these diseases undoubtedly gives hope for a better future. The widely developed prevention of acute childhood infections in the USSR will sharply weaken this important source of childhood Blindness in the near future. We have seen that in just the few years since the devastation of the war, a decrease in the figures of preventable Blindness is being observed in our USSR; the heavy legacy of tsarist Russia in the form of smallpox, trachoma, and the like is being eliminated, and along with this, the most powerful sources of Blindness are being eliminated. One of the outstanding researchers of questions of Blindness, Kershbauer, said that the number of blind people in a country is the best indicator of its culture and concern for the people's health. From this point of view, in our USSR we have a solid foundation for eliminating all preventable Blindness.