MODULE 6: DEVELOPMENT OF AMETROPIA Flashcards
process where the refractive power of the anterior segment as well as axial length adjust to reach emmetropia
Emmetropization
Desired results of emmetropization
▪️ Parallel rays of light come to a point focus or near point on the retina
▪️ The refractive condition of the eye centers on a refractive range around low hyperopia to emmetropia
_________________ of light come to a point focus or near point on the retina
Parallel rays
The refractive condition of the eye centers on a refractive range around__________________
low hyperopia to emmetropia
Prescription given the benefit of the doubt na emmetropic
+0.50 to 1.00D of hyperopia with SD of +1.00D
Theory of emmetropization
- nature and genetics are guiding and key factor
Passive process
Theory of emmetropization
- natural growth and development of most eye are likely predictable
Passive process
Theory of emmetropization
- predictable programmed growth
Passive process
Key factors of nature in emmetropization as a passive process
- growth in vitreal chamber
- crystalline lens flattens
- anterior chamber deepens
- cornea flattens
Key factors of genetics in emmetropization as a passive process
- hereditary aspect of myopia
- likelihood of being myopic is directly correlated to number of myopic patients
Likelihood of being myopic if both parents are myopic
42%
Likelihood of being myopic if one parent is myopic
22.5%
Likelihood of being myopic if neither is myopic
8%
Theory of emmetropization
Major influences in active process
Nature and environment
Theory of emmetropization
Major influences in passive process
Nature and genetics
Theory of emmetropization
Visual system is able to compute the existence of a blur and then respon appropriately to compensate for it
Active process
Elements of emmetropization
• Healthy eye
• Healthy environment
• Operational refractive range
• Intact emmetropization mechanism
develop when there is a failure in the emmetropization process
Ametropia
Ametropia results from _________ in the correlation of ocular components
Anomaly
eye does not possess enough optical power for its axial length
Hyperopia
Most common refractive error in children (most will not need optical correction)
Hyperopia
Significant hyperopia is more likely to cause
Amblyopia
Uncorrected hyperopia can cause:
Blurred vision
Amblyopia
Binocular dysfunction (strabismus)
Learning problems
eye possess too much optical power for its axial length
Myopia
2 types of childhood myopia
Congenital myopia & developmental myopia
-5.00Dsph in a child 6y/o or less with history of signs associated with nearsightedness assessed by parents since early infancy
Congenital myopia
presents at 7-10y/o with moderate degrees of myopia
Developmental myopia
Acquired myopia
Developmental myopia
caused by an irregularity on corneal surface
Astigmatism
EOR differs between 2 eye, with 2D difference
Anisometropia
Age-related changes in astigmatism: ATR at birth
“sagging” of the cornea of the still developing globe
Age-related changes in astigmatism: WTR at preschool
Stiff upper tarsal plate exerting pressure on horizontal
Age-related changes in astigmatism: ATR middle life and beyond
upper tarsal plate looses is rigidity
unilateral or less often, bilateral, decrease in BCVA in an otherwise structurally normal eye
Amblyopia
Types of Amblyopia
Visual deprivation
Strabismic amblyopia
Refractive amblyopia
Type of amblyopia caused by complete or partial obstruction of the visual axis
Visual deprivation
Type of amblyopia due to constant, non-altering, or unequally alternating tropias
Strabismic amblyopia
Type of amblyopia due to untreated unilateral or bilateral EOR
Refractive amblyopia
