Myopia Prevalence and Progression (1989) / Chapter Skim
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3. Analysis of the Progression Literature
3. Analysis of the Progression Literature
Pages 23-35
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From page 23... ...
One concluded that females are less likely to show myopic onset or increase after age 17, although it was noted that such findings could be biased by sex differences in culturally determined occupational patterns (Goss et al., 1985~. The other study reported equal incidence of loss of unaided distance visual acuity among male and female college students (Parnell, 1951~.
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From page 24... ...
Similarly, the decrease in mean refractive status during the period beginning at age 7 is produced not by a general decrease in refractive status but by the onset of myopia and its progression among a portion of the population. By age 25, from 15 to 25 percent of samples from clinic or general population groups have been found to be myopic by one or both of the following criteria: visual acuity is less than 20/20 and improved to 20/20 by concave lenses, or an amount of myopia of -0.50 D
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From page 25... ...
Groups of young males between ages 17 and 21 have been examined since 1876 to determine uncorrected visual acuity or refractive status prior to admission to college or military officer training, and again after a period of time. Studies of those ages 17 to 21 at entrance generally report that subjects exhibiting hyperopia of greater than +0.75 D
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From page 26... ...
College Students Unquestionably, many young adult males who undertake college study or assume roles that involve extensive near work become less hyperopic or more myopic. For very low hyperopes, the change may be great enough to produce a low degree of myopia.
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From page 27... ...
Data suggest that the total amount of myopia that develops among those who were emmetropes or low hyperopes before entering environments associated with risk seldom exceeds -1.00 D., and that when myopia progresses in these environments, the progression is seldom as much as -2.00 D A few longitudinal studies involving small numbers show that individuals may change at a fairly constant rate over several years, even into their 30s (Diamond, 1957; Kent, 1963; Kinney et al., 1979; Provines et al.
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From page 28... ...
Subjects ranged in age from 18 to 41: 51 percent of the submariners showed unaided visual acuity loss versus 20 percent of the control group. Greene (1970)
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From page 29... ...
military academies provide convincing evidence that about one in five young emmetropes and low hyperopes become low myopes in an intense academic environment and that more than half of all myopes, most of whose mvonia has stabilized under the same circumstances will show mvocia progression. ,, ~ That significant myopic shifts occur commonly among military cadets and consequently lead to visual disqualifications was first documented in the early 1940s.
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From page 30... ...
The Naval Academy studies show that those who initially exhibit 20/20 visual acuity, but who develop myopia of low degree when placed in the Academy environment, have two characteristics in common: they are more often at or near the lower end of the age spectrum (age 17 to 21 at entrance) and most are essentially emmetropic (range from +0.50 D
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From page 31... ...
The mean myopic change for the group was -0.66 D Brown reported that the mean change of five subgroups, all of whom were myopic at entrance (entering spherical equivalent refractive errors of -0.50 D
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From page 32... ...
O'Neal gives more detailed changes for specific ranges of entering refractive error. The mean refractive error change over the 2.5 year period in the O'Neal study is given in Table 10 for various levels of entering refractive error.
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From page 33... ...
The higher amount of myopic change noted for the 1980 data than the 1985 study may be accounted for by the decision in the 1980 study to use only the data from the eye with the poorer uncorrected acuity. In addition, the 1980 study excluded a large number of subjects because the entering refractive data were not available for most of those who had 20/20 or better uncorrected visual acuity and did not wear spectacles.
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From page 34... ...
V - 0.62 - 0.52 -0.43 - 1.00 -0,58 -°'19 1.00 +0.50 0.00 - 0.25 - 0.50 - 1.00 -3.00 ENTERING SPEQ REFRACTIVE ERROR ( D) FIGURE 3 Mean myopic shift in spherical equivalent (SPEQ)
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From page 35... ...
Owens and Harris (1986) reported that noncycloplegic refractions taken at the beginning and the end of each of two freshman semesters exhibited significant myopic shifts, as did accommodative focus measured in darkness (dark focus)
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