100 On Heterochromia Tridis in Man and Animals 



Fuchs(4) in 1906 reported 38 cases, of which a large proportion 

 suffered from cataract and a considerable number from opacities of 

 cornea or vitreous. 



Anton Lutz (5) after an exhaustive study of the subject of hetero- 

 chromia also corroborates the frequent recurrence of diseased conditions 

 in the lighter eye, and comes to the conclusion that hereditary influence 

 as a causative factor in heterochromia has not been clearly established. 



From these observations, and from the experience of other ophthalmic 

 surgeons, there can be no doubt that intra ocular disease, especially when 

 associated with increase of intra ocular tension, may bring about, under 

 certain conditions, anterior depigmentation, partial or complete, of the 

 iris of the diseased eye. 



But beyond this limited group of cases, in which irregular iris 

 pigmentation is associated with disease (frequently antecedent) of the 

 affected eye or eyes, there is a larger group (growing in size in proportion 

 to the care which is exercised in searching for and examining the cases) 

 in which the irregular pigmentation of the iris is congenital and 

 unassociated with any evidence of disease. 



Thus Thorpe (26) and Allan (2c) record such cases. J. Ross(2rf) 

 found 11 cases of heterochromia in a series of 5000 patients in which 

 the irregular eye colour was not associated with any symptoms. 



In these congenital and healthy cases the demarcation between the 

 pigmented and the less pigmented, or the unpigmented portions of the 

 iris in the same eye, is often sharply defined with clear tangential 

 margins quite unlike the merging of pigmented into unpigmented areas 

 in disease. 



Further, in a certain number of these congenital heterochromia 

 cases a familial incidence strongly suggests a genetic origin. When we 

 find the heterochromic condition closely associated with certain varieties 

 of domesticated animals, and in individuals in which there is no evidence 

 of ocular disease, when further we find that it makes its appearance in 

 man and in animals during the inter-breeding of individuals and varieties 

 of different eye colour and pattern, then we are, I think, fully justified 

 in considering that the whole subject of heterochromia of the iris should 

 be re-investigated from the genetic point of view. 



It is the object of this paper to record some observations which bear 

 on this hereditary aspect of the problem. 



Coincidentally with the important discovery announced by Hurst(6) 

 in 1907 (and independently by Davenport later) that the inheritance 

 of eye colour in man followed Mendelian lines, a further attempt was 



