[The importance of biomicroscopic examination of the lens in the detection of heterozygotes for certain hereditary diseases, in particular, myotonic dystrophy].

Slit-lamp examination of the lens of 80 normal controls aged between 17 and 36 years has shown that the opacities are very common (91.5%). The total opacities count (TOC) varies between 0 and 109, with a mean value of 14.65 and a standard deviation of 18.43. The study of 10 families of myotonic dystrophy supports the value of such a test in early diagnosis of this condition. The value of the TOC in carrier detection of Lowe's syndrome and in the diagnosis of "formes frustes" of hereditary cataract is discussed. The possible application of this test in genetic counselling is stressed.