Adult onset myopia was investigated by ultrasound eye measurements and keratometry in 33 subjects (16 females, 17 males; age 32-62 years; age at myopia onset 18-50 years, mean value 26.2 years, SD 7.80). They were compared with 30 subjects (15 females, 15 males; age 29-62 years) with myopia onset age 4-16 years (mean value 11.1 years, SD 2.89). Excluded were subjects with cataract and corneal pathology. In the adult onset group, myopia ranged a little lower than in early onset myopia (mean values -3.24 and -4.91 D, respectively), but high myopia was encountered in both groups (peak values -10 and -10.5 D). In both groups axial elongation was the main oculometric event. There was no evidence of a corneal/lenticular background in adult onset myopia. In accord with the higher myopia in the early onset group the eyes were also larger (as for axial and vitreous length, mid lens depth) than in those of adult onset. Adult onset myopia being axial of nature, the findings confirm what has been suggested from recent reports by other authors: that the eye has a potential for re-starting growth, even years after the presumed normal ocular growth arrest during early teenage years.
Over the last three decades some American Indian tribes in North America have received attention in the literature as a minority group with unique visual characteristics. Studies on the refractive status of Indians have shown an increase of refractive errors and particularly an abnormally high prevalence, and amount of, with-the-rule astigmatism. These changes appear to have taken place over the last 40 years. Eskimos, on the other hand, have recently showed an astoundingly high incidence of myopia. Other Native American tribes do not show dramatic changes in myopia or astigmatism. The Public Health Service-Indian Health Service, as an ongoing aspect of their responsibilities to Native Americans, perform screenings on children. This study reports the results of visual screenings primarily of Oklahoma Cherokee and Minnesota Chippewa children.
From: Fortuine, Robert et al. 1993. The Health of the Inuit of North America: A Bibliography from the Earliest Times through 1990. University of Alaska Anchorage. Citation number 2468.
PURPOSE: Refractive errors are a serious worldwide problem. So far a few papers have described the relationship between refractive errors and intelligence. However, based on the growing interest into the relationship between refractive errors and intelligence quotient (IQ) we decided to present and discuss the latest results of the clinical studies on that subject. MATERIAL AND METHODS: A review of the literature concerning the relationship between refractive errors and IQ was done. RESULTS: In 1958 Nadell and Hirsch found that children in America with myopia have a higher IQ. A similar relationship has been described by other researchers from the USA, the Czech Republic, Denmark, Israel, New Zealand, and Singapore. In other related studies, it was reported that myopic children regardless of their IQ gain better school achievements--table 1. It was also observed that schoolchildren with hyperopia have a lower IQ and gain worse school achievements--table 2. Several hypotheses explaining the relationship between refractive errors and intelligence have been published. Recently, Saw et al. concluded that higher IQ may be associated with myopia, independent of books read per week, in schoolchildren. According to them "the association between genetically driven IQ and myopia of hereditary predisposition could be forged because of a pleiotropic relationship between IQ and myopia in which the same causal factor is reflected in both genetic traits. There may be similar genes affecting eye size or growth (associated with myopia) and neocortical size (possibly associated with IQ)". CONCLUSIONS: The conducted clinical observations suggest that children with myopia may have a higher IQ. This relationship is most probably determined by genetic and environmental factors.
To study the prevalence of and changes in astigmatism from the onset of myopia at school age.
Two hundred and forty myopic schoolchildren (mean age 10.9 years), with no previous spectacles, were recruited during 1983-1984 to a randomized 3-year clinical trial of bifocal treatment of myopia. Three annual examinations with subjective cycloplegic refraction were performed for 237-238 subjects. Subsequent examinations were performed at the mean ages of 23.2 and 33.9 years for 178 and 163 subjects, and the last examination, including data from prescriptions of different ophthalmologists, for 32 subjects. Corneal topography was studied at baseline, at the 3-year follow-up and at the two adulthood follow-ups. Prevalence and changes in refractive astigmatism (RA), in its polar values J0 and J45, and corneal astigmatism (CA) were studied.
Mean RA of the right eye increased during follow-up from 0.26 D (SD) ± 0.30 to 0.79 D ± 0.74. Mean CA was 1.07 D ± 0.74 at study end. The prevalence of RA =0.25 or =1.00 D increased from 54.9 and 3.8% to 83.4 and 34.4%, respectively. The main direction of the axis of RA and its polar value J0 and CA changed mainly through sphericity, from against the rule (ATR) to with the rule during the follow-up. There was a negative correlation between RA and spherical refraction in the ATR group at end of follow-up. Changes in RA were associated with increase in myopia and with changes in CA.
The prevalence and mean amount of RA associated with CA increased, and the axis of astigmatism changed among myopics during the 23-year follow-up.
Changes in astigmatism were followed for a 3-year period among 238 myopic children as part of a clinical trial of myopia treatment. Children with mild myopia and no previous myopic spectacle correction and astigmatism less than or equal to 2 D were included in the study. The prevalence of astigmatism of at least 0.25 D was 55% at the beginning of the follow-up at a mean age of 10.9 years, increasing to 76% during the 3-year period. At the same time the mean astigmatism increased from -0.26 D to -0.45 D. Most of the astigmatism was against the rule; with the rule astigmatism represented 18% of the astigmatism at the beginning and 24% at the end of the study. There was a weak correlation between the spherical equivalent and astigmatism at the beginning of the follow-up (r = 0.122, n = 240, P = 0.029) but not at the end of the follow-up. Myopic progression controlled for the spherical equivalent, was not related to degree of astigmatism at the beginning of the study.
School myopia is a most common health problem in schoolchildren, in adolescents in particular. School myopia resulted from connective tissue failure of the whole organism. Some data, such as the association of school myopia with the HLA system confirm this idea. New investigations in this direction will assist in concretizing the real cause of this type of myopia. The interaction between the lighting conditions and the development of refraction is also of interest.
From: Fortuine, Robert et al. 1993. The Health of the Inuit of North America: A Bibliography from the Earliest Times through 1990. University of Alaska Anchorage. Citation number 676.
Intelligence test scores and educational levels were compared for 5943 myopic and 9891 non-myopic 18-year-old men being drafted for military service in Denmark. The former were grouped by degree of myopia, in the range -0.25 diopters (D) to -7.75 D, according to the power of correcting lenses required. Myopes of all degrees had significantly higher test scores and educational levels than non-myopes. However, the relation of these two variables to degree of myopia was not linear; for both variables there were no significant differences among myopia groups in the range -2.0 to -7.75 D. Whereas factors associated with intelligence and education seem to be important in triggering the onset of myopia, they seem to be much less important in determining the degree to which myopia progresses.
