THE RELATION OF HEREDITARY EYE 

 DEFECTS TO GENETICS AND EUGENICS' 



LuciEN Howe, M.D., Buffalo 



OF LATE years, while trying to 

 learn something about ocular 

 muscles, I have been confronted 

 often by questions concerning 

 heredity. I have found, as others 

 doubtless have, three, four or even more 

 persons in the same family with a 

 similar form of heterophoria,^ hetero- 

 tropia,^ predisposition to ocular fatigue, 

 or similar abnormal muscular conditions. 

 It seemed impossible to study these 

 anomalies satisfactorily without first 

 halting to learn something about that 

 mystery which we call heredity. 



It is not possible here to give any 

 systematic account of the studies al- 

 ready made of hereditary eye defects, 

 except to mention the classic work by 

 Groenouw,^ the interesting histories 

 collected by Nettleship, the more recent 

 bibliography by Loeb, with the exhaus- 

 tive articles by him, or those by Libby 

 and others. The point is that we oph- 

 thalmologists have been content thus far 

 with reporting family histories without 

 attempting to relate those histories to 

 other facts, now well established by 

 geneticists. 



The best way to learn these princi- 

 ples, and one vastly more interesting, 

 is to supplement the reading with at 

 least a few experiments. 



The breeding of eye defects is easier 

 than most persons imagine. Chickens 

 and pigeons are the best subjects for 

 such experiments. 



By advertising in the Reliable Poidtry 

 Journal and other trade papers, it has 



been possible to obtain for the parent 

 stock more than a dozen specimens of 

 eye defects. These included corneal 

 irregularities, and variations in the color 

 of the iris and in the position of the eyes 

 and of the pupil. The different pens of 

 chickens at a small place, known as 

 Mendel Farm, on the lake shore near 

 Buffalo, have proved to me a source of 

 much interest and enlightenment. 



The breeding of dogs has not been 

 found satisfactory. Eye defects are 

 rare, the generations slow and the litters 

 small. For similar reasons, cats are 

 undesirable. It is probable, however, 

 that interesting results could be obtained 

 by breeding white cats which have 

 blue eyes — such cats being often deaf. 

 This fact had been already observed 

 by Darwin and has been the subject of 

 breeding experiments by Dr. Graham 

 Bell. 5 



The eyes of the small fruit fly, Dro- 

 sophila ampelophila, have proved most 

 interesting. I am indebted to Professor 

 Morgan of Columbia for parent stock, 

 the blind variety of which I bred through 

 more than twelve generations. 



PRACTICAL VALUE OF THE STUDY 



The average reader of this paper may 

 say that such a glance at the principles 

 of heredity may be curious and possibly 

 interesting, but of what practical use 

 is it ? 



Of course we never find a typical 

 Mendelian ratio in the human species, 

 because brothers and sisters never 



1 Read before the Section on Ophthalmology at the Sixty-Ninth Annual Session of the Ameri- 

 can Medical Association, Chicago, Jime, 1918. Reprinted in condensed form from the Journal 

 of the American Medical Association, Vol. 70, pp. 1994-1997. 



2 A tendency of the visual axes to fail to meet in the fixation point, due to weakness of one 

 or more of the ocular muscles or their faulty innervation. m_ 



3 Displacements in position. '"^ 



^ Groenouw, in Handbuch der gesamten Augenheilkunde, Graefe-Saemisch, Ed. 2, Part 1 

 Vol. 11, p. 415. 



* Bell, Alexander Graham: Tr. Otol. Soc, 1885, Vol. 3, p. 478. 



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