Genetics in ophthalmology / Arnold Sorsby.

  • Sorsby, Arnold, 1900-1980.
Date:
1951
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Genetics in ophthalmology / Arnold Sorsby. Source: Wellcome Collection.

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    PREFACE of environmental factors. But disease is generally the result of the disharmonious interaction of constitution and environment, so that study of the genetic con¬ stitution of man is as significant as the study of the environmental pathogen. At the two extremes, either factor by itself may produce disease, as shown respec¬ tively by the lesions produced by mechanical injury and that produced by an inherited gene for retinitis pigmentosa. Frequently, however, other environmental or constitutional factors have to come into play for a disease process to become established. Not every individual exposed to tuberculous infection develops tuberculosis; not every carrier of the gene for, say, the Laurence-Biedl syndrome, develops the full syndrome. Medical genetics is therefore not merely a study of the modes but also of the nature of inheritance. Contrary to the widespread belief, medical genetics is not concerned with collecting curious pedigrees of the unconsidered trifles of pathology. At the very least, it is an attempt to elucidate some aspects of the constitutional basis of disease. In some affections the genetic factor is obvious. In others, it can be revealed only by exhaustive investigations aided by an understanding of genetic theory. The genetic anomahes have assumed greater significance with the recognition of modes of inheritance other than the simple autosomal récessives and dominants of the past. Isolated cases of genetic disease are no longer clinical puzzles and unusual modes of inheritance are more readily recognized. A further significant development has been the recognition of the abiotrophic character of many of the genetic anomalies, so that many affections coming on late in life and previously regarded as of environmental origin are now recognized as genetic in type. It is not unlikely that some of the so-called senile degenerations are late abiotrophic manifestations, and evidence is accumulating that senile cataract and primary glaucoma are essentially genetic affections. Indeed, the congenital anomalies and classical forms of abiotrophic defects constitute only a small part of the inherited abnormalities or inherited potentialities towards abnormality of the eye. The scope of ophthalmological genetics is, in fact, very much wider than was suspected by the pioneers of the study, and this enlarged scope has an immediate bearing on the causes of blindness and ocular disease generally, as seen today. And if the scope of ophthalmological genetics has become larger, so has the prospect of the eventual control of the genetically determined affections. The fatalism with which genetic affections are generally regarded is as unfounded in reason as it is unjustified by achievement already reached. It is more than an act of filial piety to pay tribute to the work of Edward Nettleship and C. H. Usher. Their pioneer efforts have done much to make ophthalmological genetics the most highly developed branch of medical genetics. The monumental volume by Julia Bell in The Treasury of Human Inheritance has been a constant source of help and inspiration, as have been the exhaustive ophthalmological surveys by A. Franceschetti and by P. J. Waardenburg, and the fascinating Introduction to Medical Genetics by J. A. Fraser Roberts. My thanks are due to many workers for the use of pedigrees and other illustra¬ tions, and to Miss Muriel Attfield, M.Sc., and Mr. C. Martin for help with the drawings. Acknowledgement of borrowed illustrations is given under the appro¬ priate figures. X