George A. Leary

THE TRANSMISSION OF REFRACTIVE ERRORS WITHIN ESKIMO FAMILIES

ABSTRACT A study was carried out on volunteer Eskimo families at Barrow, Alaska. The total population consisted of 508 subjects with complete information including a clinical examination as well as refractions with and without cycloplegics. Correlations between refractive errors of parents and children as well as between siblings are determined on 41 family units comprising 197 subjects. The correlations between parents and children were not significantly different from zero, whereas the correlations between siblings were high and significant. These results were interpreted to suggest that there is no major hereditary component involved in development of myopic refractions among the offspring while there is a strong environmental component operating to create the sibling correlations. These interpretations are supported by the fact that there is virtually no myopia among the grandparents or parents but approximately 58% of the offspring are myopic.

Refractive errors, reading performance, and school achievement among Eskimo children.

ABSTRACT The relationship between refractive errors and various measures of reading and school achievement on the entire school population of Eskimo children at Barrow, Alaska, are presented. Comparisons are made with the Caucasian population of school children at Pullman, Washington.

Comparison of cycloplegic and non-cycloplegic refractions of Eskimos.

&NA; A cycloplegic and non‐cycloplegic refraction was obtained on 946 eyes of 213 male subjects and 291 female Eskimos between 6 and 88 years old. When the results obtained are compared with those obtained on white subjects by Bannon, good agreement is found between the two studies in the case of the hypermetropic subjects but relatively poor agreement is found for the myopic subjects. Bannon found approximately 38% of his myopic cases showing less myopia under cycloplegia whereas the present study found 75% of the myopia subjects showing less myopia under cycloplegia. The Barrow population shows an exceptionally high proportion of myopes in the age group between 11 and 26 with approximately 60% being myopic with a high degree of myopia. It is possible that these Eskimo subjects are in such a strong spasm of accommodation that it is not possible to reduce the spasm by means of any type of fogging technique. Thus, when the subjects are put under cycloplegia, there will be a considerable decrease in the amount of myopia resulting from a reduction of the spasm.

THE INHERITANCE OF OCULAR COMPONENTS

&NA; This paper represents the analysis of the components of refraction across seventy‐one Eskimo families consisting of thirty, first generation or grandparents, forty‐one, second generation or parents and 258 generic children. Both husbands and wives are included in the first and second generations. The results indicate that the initial size and component relationships within the one‐two year old eye are probably inherited along with high hypermetropia and corneal power in older children and adults. There is no evidence that any of the other components are inherited.

Four years of annual studies of chimpanzee vision.

&NA; Four annual studies of the visual ocular components of approximately 40 male and 40 female chimpanzees are summarized and discussed. In general, ocular changes over the five‐year span are similar to those found in human subjects under similar conditions except for changes in the corneas, which show changes not usually found in humans. Approximately a third of the subjects show increased axial lengths and myopia. Females show higher levels of myopia than males.

Houston Myopia Control Study: a randomized clinical trial. Part I. Background and design of the study.

ABSTRACT The Houston Myopia Control Study is a 3‐year randomized clinical trial in which each of 213 myopic children was placed in either a single vision (standard treatment) group, a +1.00 D add treatment group, or a +2.00 D add treatment group, on the basis of a randomized procedure. Subjects for the three treatment groups were matched on the basis of sex, age, and the initial amount of myopia. The study involves two groups of investigators: an evaluation team, whose task has been to evaluate candidates before entering the study and to reevaluate each subject on a yearly basis for the 3‐year period, and a patient care team, whose task has been to prescribe glasses for each subject as well as to counsel subjects and their parents in the correct use of the glasses and to provide a follow‐up examination every six months for the duration of the study. Once the glasses had been prescribed, members of the evaluation team were not permitted to know which subjects wore single vision lenses and which wore bifocals. In the interest of good patient care, members of the patient care team knew which subjects wore single vision lenses and which wore +1.00 D add or +2.00 D add bifocals. In this report, the authors discuss theories concerning the etiology of myopia, methods that have been used in an attempt to control the progression of myopia, and the design of the current study. Further reports will present the results of the study on the basis of the data collected by each of the two study teams.

A set of equations for computing the components of ocular refraction.

ABSTRACT The ultrasonic method of assessing the ocular components of refraction provides an observed axial length but no data on the lens surface powers. For many years the phakometric methods have been supplying a full data output on the lens surfaces and relying on a computed value for the axial length; the validity of the latter, however, has been challenged in the light of present‐day techniques. A series of equations are presented in which the two techniques are combined to overcome some of the objections to phakometry yet maintain not only the lens data but also include the cardinal points of the eye optical system.

Ultrasound and phakometry measurements of the primate eye.

Abstract : Results obtained on 160 eyes of 53 male and 40 female chimpanzees ranging in age from 2 to 15 years, using ultrasonography and photographic ophthalmophakometry to measure anterior chamber depth, lens thickness, and axial length, are compared with the results obtained on 140 human eyes of a comparable sex grouping using the same methods. The intercorrelations between methods are not quite as high on the chimpanzees as on the humans, but the correlations between the measures of axial length and the vertical ocular refraction are virtually identical for the two groups. Either ultrasound or photographic ophthalmophakometry may be used successfully on primates and will yield results which compare favorably with those obtained on humans, but ultrasound is the method of choice since it does not require as much time to make the measurement or to calculate the result as does phakometry. Further, it does not require the rigid degree of control over the animals behavior that phakometry requires and its flexibility allows measurement in situations in which it would be impossible to obtain phakometry measurements. Thus for both human and animal work, ultrasound is generally superior to phakometry. (Author)

Diet and refractive characteristics.

ABSTRACT Twenty monkeys which had been on a low protein diet (2.5—3%) for an average of 32 months are compared visually with eighteen monkeys which had been on a high protein diet (22—23%) for an average of 28 months. The range of visual refractive errors as well as the median and mean refraction are identical in the two groups even though other diet‐related characteristics (height, weight, growth and development and behavior) are significantly different.