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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    congenital anomalies Night-hlindness with myopia Sex-linked recessive.—Fig. 142 a is taken from another famous pedigree, the Pfluger-Amman-Kleiner pedigree. The mode of inheritance is clearly that of recessive sex-linkage. A characteristic feature in this pedigree—and in some pedigrees recorded by Nettleship—(Fig. 142 b) was the presence of myopia ranging from 6 D to 11 D. Astigmatism was not uncommon, as also was some degree of visual defect. It is not unlikely that the pedigree of sex-linked recessive myopia recorded by Worth falls into this category. Tn one of Nettleship's pedigrees, an affected woman appeared. Autosomal recessive.—Fig. 142 c, an extract from yet a third well-known pedigree (the Gassier pedigree), shows autosomal recessive inheritance. It is uncertain whether the myopia or the night-blindness differs from features as seen in sex- linked recessive inheritance. In the Gassier pedigree, the myopia varied between 9 D and 16 D and corrected vision varied between 6/60 and 6/18. Night-blindness with abnormal fundus coloration In Oguchi's disease there is a characteristic greyish reflex on ophthalmoscopic examination. After an hour or more in a dark room the normal fundus coloration appears—the Mizuo sign. Only a few cases have been recorded in Caucasians; the affection appears to be fairly prevalent amongst Japanese. The available pedigrees show a high rate of consanguinity and suggest recessive inheritance. Fundus albi punctatus Lauber in 1910 sought to differentiate between retinitis punctata albescens, which he regarded as a progressive affection of the retinitis pigmentosa group, and fundus albi punctatus, which he considered to be a congenital stationary affection with no complications beyond night-blindness. The exact status is still uncertain. It is unlikely that any further substantial clarification of the various affections with night-blindness will be achieved until finer methods of examination than those used clinically at the present are employed. Anomalies of Colour Vision In trichromatic vision any colour (or spectral light) can be matched by a mixture of three primary colours (or spectral lights). Dichromats can match any light with a mixture of two primary lights. In monochromatic vision any light can be matched by any other light, merely by adjusting intensities. Normal trichromatic vision is present in about 92 per cent of men and about 99-5 per cent or more of women. Of the 8 per cent or so defectives amongst men, most have trichromatic vision: they match a light with a mixture of three primary lights, but their trichromatic coefficient curves are of a different shape and their colour vision differs in some details from the normal trichomats (anomalous trichromatism). Only 2-6 per cent of men are dichromats. Monochromats are rare, and there does not appear to be any definite excess of men over women. Monochromatism (total colour-blindness; day blindness) Total colour-blindness is an aspect of a severe symptom-complex, which 157