EPIDEMOLOGY OF AMETROPIA (Applied optics) Jasmin modi

History
Causative factor
Factor associated with refractive error

1. EPIDEMOLOGY OF AMETROPIA

2. CONTEXT Epidemiology of ametropia Incidence and distribution of refractive error in general population  Changes in refraction with age Hereditary and environmental factors

3. EPIDEMOLOGY OF AMETROPIA

4. EPIDEMOLOGY OF AMETROPIA According to Aristotle short sightedness myopia and long sightedness hyperopia both were weakness of eyes. People can adjust their working distance and bring closer to the face ‘’Near at the hand distance light can be perceived easily”

5. Epidemiology of ametropia History Levene and hofsteter stat that refractive error lies about the crystalline lens Johannes kepler described the optical system of the eye and action of both convex and concave lenses. Scheiner described optics of eye First indication of hyperopia accounted by William Wells Donders wrote the anomalies of accommodation Benjamin Franklin was invented BIFOCAL first time Correction of astigmatism was corrected by the patient who had astigmatism sir George Airy

6. Epidemiology of ametropia History Astigmatism first described by sir Isaac newton Donders described clinical procedures to measurement of hyperopia , myopia & Heterophoria In 1700 astigmatism was considered as normal anomaly 1.00D or more occurring in only 1 out of 40-50 patients

7. Incidence and distribution of refractive error in general population  Age Age is the single most important determinant of the distribution of refractive error in a given group. The onset and development of myopia occur in well-established yet poorly understood patterns. Only a very small proportion of infants are myopic at birth, and much of this neonatal myopia is associated with prematurity.

8. Mean refractive error in childhood

9. Prevalence of refractive errors white children

10. gender A large sample of children from the United Kingdom yielded no significant differences in refractive error between boys and girls." In other studies, the trend has gone both ways, and it is therefore probably inconclusive. Hirsch" found a more myopic mean refraction in boys than in girls among 5- to 6-year-olds but more myopia among girls by age 14 years,, Alsbirk " reported a similar trend in adults. Myopia is more prevalent in Danish school-age girls than in Danish boys of all ages." but both myopia and hyperopia are more prevalent in Finnish schoolchildren than in Goldschmidt's Danes

11. ethnicity Few studies have simultaneously compared different races, and it is problematic at best to compare data across races in different geographic areas, different cultures, and samples with different socioeconomic and educational bases. The best estimate comes from the NHANES data reported by Sperduto . The claim that there is a high prevalence of myopia among Asians is difficult to document. Oft-cited high prevalence rates among Singapore medical students'

12. Geography Certainly, no clear geographical differences emerge beyond those identified in the preceding section on racial differences in myopia prevalence in the United States.

13. diet Gardiner" conducted a nonrandomized clinical trial of the effect of animal protein supplement on the progression of myopia in children. The treated group either altered diet or took protein supplements to make 10% of the intake of calories come from animal protein. The control group followed their regular, unmonitored diet At one year, the treated group showed less myopic

14. time Researchers working in different decades used different measurement methods and different criteria for defining the types of refractive error. Different age groups cannot be directly compared. Comparisons among groups of different ethnic origins and from different P arts of the world do not lead to conclusions. Nevertheless, Table 2-12 presents an attempt to sort out these relationships.

15. Personality The conventional wisdom on associations between personality traits and refractive error is that myopia is associated with introversion." Further, myopes have been shown to exhibit an inhibited disposition, a disinclination for motor activity and social leadership, whereas hyperopes are carefree, impulsive, hyperactive, and socially passive

16. Ocular conditions The distribution of refractive errors of these groups was shifted toward more myopia or less hyperopia compared with patients who experienced normal development. Numerous conditions that interfere with normal vision have been reported to affect refractive error through the induction of a deprivation-like myopia. These include corneal opacification." eyelid closure," vitreous hemorrhage." and congenital cataract." Astigmatic and myopic spherical equivalent refractive errors have been reported in connection with hemangioma." Astigmatism is also reported to increase after the surgical correction of congenital ptosis

17. Ocular conditions Glaucoma may be connected to myopic refractive error in two ways. First, as part of the near-work theory of the etiology of myopia, prolonged reading may increase intraocular pressure ( lOP ), driving the expansion of the eye by mechanical force.": Second, glaucoma and myopic refractive errors may be associated conditions. Besides keratoconus, other corneal conditions may affect refractive error because of the alterations in corneal curvature they create. P

18. Ocular conditions change in the elevation of the photoreceptor plane as a result of retinal pathology may also have an effect on refractive error and visual acuity. The classic example is central serous chorioretinopathy, in which the sensory retina is moved anteriorly by the accumulation of fluid underneath it, with a concomitant increase in hyperopia or decrease in myopia.

19. FACTORS ASSOCIATED WITH REFRACTIVE ERROR

20. HERIDITY Studies of the heritability of refractive error and the ocular components consist of two types: those based on correlations between parents and children and those based on monozygotic and dizygotic twin comparisons. Generally, in studies of parents and offspring, higher heritabilities have been found for axial length and corneal power than for the other ocular components or for refractive error. In studies of twins, the heritabilities for corneal power, axial length, and refractive error have all been high and approximately equal and the differences in refractive error and the ocular components have been smaller for monozygotic than for dizygotic twins.

21. Near Work Human resources Theory A body of work on the nurture theory of myopia development indicts excessive reading during childhood as the cause of abnormal eye growth Examples include an increased prevalence of myopia among the first school-educated Espinosa decreased prevalence of myopia during World War II in Japan The characteristic of accommodation that has most consistently been associated with refractive error is tonic. accommodation (TA), or the accommodative state in the absence of an accommodative stimulus Myopes show the lowest levels of TA and the greatest hysteresis, whereas hyperopes have higher levels of TA and the least hysteresis. The level of TA also appears to be related to refractive error type in schoolchildren. Second, it has been shown that near work, performed for both the short term and the long term.!" can alter TA

22. this position was believed to reflect the level of tonic innervation to the ciliary muscle, this response has been termed tonic accommodation (TA).

23. Animal Model Evidence and Limitations The effects of environmental manipulation on chicken, tree shrew, and primate ocular development-creating deprivation myopia-provide some of the strongest evidence cited for a significant role for the environment in human myopia It should be noted, however, that the animal models of myopia are designed only to assess environmental effects; no animal model has been used in which any genetic effect could be found even if it existed

24. Intelligence Numerous studies have documented associations between intelligence, school achievement, and myopia. Myopes tend to have higher scores on tests of intelligence and cognitive ability and better grades v than do other refractive error groups. Hyperopes, on the other hand, tend to show poorer reading skill and other perceptual anomalies more frequently. Only one investigator has attempted to analyze all three factors in the same children, obtaining uncertain results. Ashton175 used self-reported grades in school and results from cognitive tests used in the Hawaii Family Study of Cognition as measures of aptitude and achievement. Numbers of books and magazines read, hours spent doing homework and watching television, and years of education served as measures of near work. Myopia remained associated with near work after correction for aptitude and achievement and was associated with aptitude and achievement after correction for near work.

25. Socioeconomic Status In each study, myopes tended to be overrepresented among the higher socioeconomic status and underrepresented among lower income levels. Angle and Weissman categorized 15,536 subjects ages 12 to 17 years old by refractive status and 10 levels of family income. Myopia was least frequent in the lowest income group (16.8% of those with incomes below $500) and increased steadily with increasing income to 35.1 % of those with incomes over $15,000. Sperduto et al. analyzed data from 5282 subjects ages 12 to 54 years. Once again, myopia was least frequent among the families with the lowest incomes (10.0% to 26.6% of those with incomes below $5000) and most common in the highest income families (27.6% to 30.3% of those with incomes above $10,000).

26. Changes in refraction with age

27. REFRACTIVE CHANGES FROM BIRTH TO 5 YEARS OF AGE Mohindra and Held 2 reported a study of 400 full-term infants in Massachusetts, in whom refractive error was measured in a dark room by manifest retinoscopy.’: " There was a wide distribution of refractive errors in the first month of life, from more than -10.00 D of myopia to more than +5.00 D of hyperopia.

28. From 1 year of age to 3.5 years of age, the prevalence of myopia decreased and the prevalence of emmetropia increased, because children with myopia at 1 year of age shifted toward hyperopia. Children with hyperopia between +1.00 and +2.25 D tended to have decreases in hyperopia. Some children with +2.50 D or more hyperopia increased in hyperopia, and about the same number had decreases in hyperopia. There is a higher prevalence of astigmatism in infants than in older children and adults. 1O12 Samples of primarily white infants have been reported to have a high prevalence of against-the-rule astigmatism, which decreases over the first few months and years of life. Dobson et al. IJ reviewed cycloplegic refraction records of consecutive patients in a Boston hospital medical center. In 85 children under 3.5 years of age, against the-rule astigmatism was found 2.5 times as often as with-the-rule astigmatism. In children between 5.5 and 9.5 years of age, with-the-rule astigmatism was 3 times as common as against-the-rule astigmatism.

29. astigmatism Against-the-rule astigmatism was more common than with-the-rule astigmatism before 4.5 years of age, but after that with the-rule astigmatism was more common. There were 29 children who had 1.00 DC or more of astigmatism at 6 months of age. Of these children, 16 had against-the rule, 8 had with-the-rule, and 5 had oblique astigmatism. All 29 had reductions in astigmatism by the time they were 4 to 6 years old Some of the infants who had against-the-rule astigmatism shifted to with-the-rule astigmatism by 6 years of age In a longitudinal study conducted in Israel, Scharf et al." found that 42% to 45% of 134 eyes of premature babies were myopic shortly after birth. Of these myopic eyes, 46% were emmetropic at 7 years of age. Of the eyes that were hyperopic at birth, 77% were emmetropic at 7 years of age.

30. REFRACTIVE CHANGES DURING THE SCHOOL-AGE YEARS Longitudinal Studies on Populations not Selected by Visual Characteristics Hirsch found that in most cases the change in refractive error from 6 or 7 years of age to 11 or 12 years of age was linear. For the children whose changes in refractive error were linear, the mean slope was -0.070 per year. There was a negative skew in the distribution of slopes of refractive error change, because of the higher negative slopes for children with myopia. Hirsch randomly selected 100 of the 605 emmetropic eyes for data analysis. His comparison of refractive errors at the two different ages is given in Table 3-1. Presuming that the 100 eyes are representative of the sample, each of the numbers in the emmetropia column could be multiplied by about 6

31. Changes in Hyperopes Compared with Myopes Hofstetter's conclusion" that refractive change is faster when a child crosses from hyperopia into myopia was supported by Mantyjarvi ." Mantyjarvi's analysis was based on the right eye spherical equivalents of cycloplegic refraction in children 7 to 15 years of age. Forty-six hyperopic children and 133 myopic children were followed for at least 5 and up to 8 years.

32. Onset of Myopia in Youth The four types of myopia in this system are congenital, youth-onset, early adult-onset, late adult-onset Youth-onset myopia has its onset in the school-age years and is the most common type of myopia. Most studies give a prevalence of myopia of about 2% at 5 or 6 years of age and a prevalence of 20% to 25% at 15 to 16 years of age

33. Progression of Childhood Myopia Once myopia appears in childhood, it increases until the middle to late teens.“ Typical patterns of childhood myopia progression are shown in Figures 3-3 and 3-4, Additional examples of patterns of childhood myopia progression, shown in Figure 3-5, include some points before the onset of myopia and show that the refractive change accelerates at the onset of myopia, Perusal of the examples in these figures suggests that the change in refractive error is largely linear from the beginning to the end of childhood myopia progression, Using an F test for linearity and visual inspection, Langer" determined the refractive changes to be linear in all of the children with myopia greater than -0,50 D in his study population, GOSS44 studied the linearity of the change in refractive error with age from ages 6 to 15 years in the optometric practice records of 198 children with myopia. Of the cases, 90% to 94% were found to fit a linear model by an F test for linearity and the statistical significance of the correlation coefficient, When cases such as those in Figure 3-5 were excluded, 96% were found to be linear.

34. HERIDITY AND ENVIRONMENTAL FACTORS

35. Myopia & hyperopia Franscosis discussed the inheritance about it. Wixon compared refractive findings for 10 pairs of identical twins , 6 pairs of fraternal twins and 10 pairs of same sex siblings He found that spherical equivalent +0.99 for the identical twins ,+0.67 for fraternal twins & +0.54 for the siblings. Hirsch and ditmars analyzed data concerning the refractive states of both parents of each of 258 myopic children , the greater the percentage of parents who were myopic

36. astigmatism Astigmatism is genetically determined Wixson found the correlation coefficients for refractive astigmatism to be +0.93 for identical twins ,+0.07 for fraternal twins & +0.47 for the control group of same sex siblings Astigmatism is transmitted as an autosomal dominant trait and is known to be transmitted through general questions Many authors have found concordant hyperopic astigmatism in identical twins , but that discordance has been found to be the rule in fraternal twins

37. Environmental factors Few authors suggests that environmental factors are changes in hyperopia Ware observed that myopia occur in officers who use computer for near work Donders proposed that myopia occurs as a result of prolonged tension on the eyes during close work and due to and elongation of the visual axes. Cohn published that in children myopia progress in school REFRACTIVE ERROR AND OCCUPATION Young , learly , baldwin ,west box , harris and johnson investigated the roles of heredity and environment in the refraction of 41 eskimo family units They found the average refraction of +1.69 D for 82 parents and +0.33 D for the 115 children .they also found that correlation between siblings were high and significant . The proposed environmental component was compulsory schooling leading to a considerable amount of reading among the children

38. astigmatism Astigmatic changes is predictable with age The tendency of both rigid and soft contact lenses causes changes By wearing rigid contact lens 12 year old wear patient corneal astigmatism increased with the rule direction +2.50 D in one eye & +3.25 D in other Hartstein and becker reported not only on the development of with the rule astigmatism but also developed keratoconous . This test done by Schiotz tonometer with the rule ------Lower rigidity The key to variation of ocular astigmatism changes with ages ,with contact lens and ocular rigidity

39. Can eyelid pressure cause astigmatism?? Yes ? Why Any pediatric having astigmatism Developed with the rule astigmatism but it is covered by internal astigmatism But patient having normal or high IOP may develop with the rule astigmatism but later on it will compensate by eyelid pressure

40. Primary care optometry chapter2 page 22 onwards Clinical boorish chapter 2 page 32 onwards