Twins have aroused the curiosity of man throughout history. In modern times twin research has become a special branch of human genetics and has greatly contributed to our knowledge of the earliest stage of prenatal development. Another aspect of twin research is the distinction between inherited and acquired traits. Of particular value are observations in monozygotic (true, singleegg) twins, who originate from one chorion and a single placenta. They are always of the same sex and belong to the same blood group; their over-all resemblance is very close, and popularly they are known as identical twins.
Twin research in ophthalmology has assumed considerable proportions. Every normal and abnormal eye trait in identical twins has been extensively investigated, and a number of studies are especially devoted to findings in the fundus oculi. Yet there still is very little agreement among the most competent observers, some claiming complete identity of all characteristic
TOWER P. The Fundus Oculi in Monozygotic TwinsReport of Six Pairs of Identical Twins. AMA Arch Ophthalmol. 1955;54(2):225-239. doi:10.1001/archopht.1955.00930020231010