Incidence And Distribution Of Refractive Anomalies Flashcards
At birth, what type of refractive error is most common?
Hyperopia
What percentage of newborns are myopic?
Less than 25%, most at hyperopic.
As an infant grows, they shift towards:
Emmetropia
Why do infants become more Emmetropic as they become older?
Because as they grow taller, their eyes grow as well. Therefore, they become more myopic.
Within first year of life
What is emmetopization?
The process in which refractive error shifts towards emmetropia as the child ages
What happens between ages 5-15?
Ocular development slows
Anterior chamber depth increases
Vitreous chamber depth increases
Axial length increases
Cornea is stable
Lens power decreases
(Hyperopia decreases)
On average, by how much do the eyes change between ages 5-15?
3 D
2 D from lens power
1 D from length of eye
Between the ages 5-15, myopia increase by..
Over 7x to 15%
Juvenile-onset myopia
Increase about -0.50 D per year during early teen years
Due to reduced ability of lens to compensate for the growth in axial length
Myopia progression stops around what age?
- 6-15.3 years old for females
15. 0-16.7 years old for males
When does the eye stop growing?
Beyond ages 13-14
Adult-onset myopia
10% of population is myopic after teen years
Total myopic prevalence in adult population is about
25%
Factors that affect refractive error distribution
Age Gender Ethnicity Geography Diet Time Personality Systemic Conditions Ocular Diseases
What is the most important determinant of distribution of refractive error in a given group?
Age
Neonatal myopia
Associated with prematurity
Astigmatism from birth to ages 6-8
Have greater than 1 D cyl, but then decreases ages 6-8
When will refractive error become stable?
High school ages
Refractive error in Gender
Inconclusive.
No significant differences between males and females.
Ethnicities and Refractive Errors
Not enough data.
Caucasians have 2x prevalence of myopia than African Americans
Asians are more prevalent than Caucasians
Asians > Caucasians > African Americans
Geography and Refractive Error
More so based on ethnicity.
Studies showed that other factors such as diet and education base geography
Alaskans > Austrailians/Europeans > US/Native Americans/Jewish > Nigerian/Black
Diet and Refractive Error
Unclear. Difficult to alter nutritional needs of children.
Time and Refractive Error
Inconclusive.
Studies done in different decades are difficult to compare with each other.
Overall trend: decrease in prevalence of myopia with increasing age in elderly range
Personality and Refractive Error
Myopia is associated with:
- introversion
- inhibited disposition
- disinclination for motor activity and social leadership
Hyperopia is associated with:
- carefree
- impulsive
- hyperactive
- socially positive
NO STRONG DATA
Systemic Conditions and Refractive Error
Effects the development of the eye
Albinism (inability to produce melanin)
-associated with myopia and high astigmatism
Down’s Syndrome
-myopic in 1/3 of population
Connective Tissue and Skeletal Disorders are associated with myopia
Homocystinuria
-lens dislocation, myopia, light iridies, hypotony, retinal elevation, cataract
Diabetes
-higher prevalence of myopia
Ocular Diseases and Refractive Error
Majority of conditions are associated with myopia
Involves peripheral visual impairment
Conditions associated with hyperopia:
-albinism, maculopathies, Rod monochromacy
Glaucoma is connected with..
Myopia
Near-Work Theory of Myopia
Prolonged reading increases IOP, driving the expansion of the eye by mechanical force.
Directly related to Glaucoma
Against the rule astigmatism
Pellucid Marginal Degeneration
Thins the inferior cornea and flattens the vertical corneal meridian
Factors with a known affect on refractive error distribution
Age, Systemic Conditions, and Ocular Diseases
With 1 myopic parent,
20-25% chance the child will be myopic
With 2 myopic parents,
30-35% chance child will be myopic
Inheritance and Refractive Error
Axial length and corneal power seem to be hereditary.
High heritabilities seem prevalent in axial length, corneal power, and refractive power.
Near Work Theory and school aged children
Excessive reading causes abnormal eye growth, therefore leading to myopia
Studies supporting Near Work Theory:
Increase in myopia prevalence in first school-educated Eskimos.
Decrease in myopia during WW2 in Japan
Adult onset myopia in college populations
Intelligence and Refractive Error
Myopes tend to have higher scores on tests of intelligence and cognitive ability
Hyperopes tend to show poorer reading skills
Socioeconomic Status and Refractive Error
Myopia tend to be over represented among the higher socioeconomic strata.
-and underrepresented on low income levels.
Possible link between myopia, intelligence, and education.
