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September 1975

Size of the Physiologic Cup of the Optic Nerve Head: Hereditary and Environmental Factors

Author Affiliations

From the National Eye Institute (Drs. Schwartz and Reuling) and the National Heart and Lung Institute (Dr. Feinleib), National Institutes of Health, Bethesda, Md.

Arch Ophthalmol. 1975;93(9):776-780. doi:10.1001/archopht.1975.01010020670002

This study provides a quantitative assessment of heritability of size of the normal physiologic cup when estimated as a continuous variable. A horizontal cupdisc ratio was estimated clinically among a sample of 37 pairs of monozygotic (MZ) and 26 pairs of like-sexed dizygotic (DZ) twins. Differences in intrapair variance and intraclass correlation coefficient between the MZ and the DZ samples were large and highly significant, and suggest that inheritance plays a major role in determining diameter of the normal physiologic cup. Values of heritability index (HI, an estimate of the proportion of variance within pairs explained by genetic factors) ranged from 0.60 to 0.80 by various computational methods employed.

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