THE LITERATURE on mongolism is replete with marked differences in incidence of some of the more common eye findings associated with this condition. Few authors define or even partially describe the sign they are reporting, and fewer still explain the means by which the sign was measured. There is no doubt that different authors have used different criteria in reaching their conclusions, and therefore comparison between the results of one report and another is difficult. Furthermore, lack of definition produces confusion, and some signs may receive an emphasis conducive to misdiagnosis.In this study, four of the common eye findings in mongolism, easily determined without special instruments or training, are defined, the pertinent literature reviewed, and the incidence in institutionalized and noninstitutionalized patients with mongolism compared with normal controls. The signs are slanting eyes, epicanthic folds, Brushfield spots, and hypoplasia of the iris. As the frequency of Brushfield spots is related to eye color, the eye color of the institu¬ tionalized mongoloids and of the normal con¬ trol group was determined. For the sake of clarity, each eye finding is considered separately. SubjectsGroup I.-Examined were 138 institutional¬ ized mongoloids, 83 males and 55 females.Doubtful cases were excluded. The data were broken down by five-year age groups : 0 to < 5 years, 5 to < 10 years, 10 to <15 years, 15 to ,33, and 42 subjects in these age groups, respectively. Group II.-Because mongoloid children are rarely institutionalized under 5 years of age, and only four such patients were present in group I, the records of 78 noninstitutionalized mongol¬ oids, primarily examined by one of us (H. Z.), were reviewed and the data on slanting eyes, epicanthus, and Brushfield spots analyzed in asimilar manner and presented in the Table for comparison. There were 64 subjects under 5, and 14 between 5 and 10 years of age. The diag¬ nosis of mongolism was confirmed in most cases by chromosomal analysis.Group III.-Data on 150 "normal" subjects were obtained in a pediatrie out-patient depart¬ ment of a large university hospital. Fifteen males and 15 females were examined in each of the age groups outlined for group I. DefinitionsSlanting Eyes.-A clear plastic straight edge was placed across the bridge of the nose at the level of both inner canthi. The elevation of the outer canthi above this horizontal line was esti¬ mated, in millimeters, by one observer and re¬ corded. All measurements were carried out by the same observer. The use of a protractor in order to measure this slant in degrees was at¬ tempted, but this was found impractical. The position of the head was fixed to insure stand¬ ardization of measurement. The following four categories were defined:1. Straight: if the outer canthi were less than 2 mm above this line;2. Slanting (mongoloid) : if the outer canthi were more than 2 mm above this line ( Fig 1 ) ; 3. Antimongoloid : if the outer canthi were below this line;