Amblyopia II Flashcards
What are the types of refractive amblyopia
- meridonial
- isoametropic
- anisometropic
Meridional amblyopia
Due to uncorrected high astigmatism in one or both eyes
-can be easily missed due to the orientation of the astigmatism (some kids can squint or compensate)
Isoametropic amblyopia
- caused by very high refractive error in both eyes
- so high that a clear retinal image cannot be obtained
- results in a bilateral decrease in VA
A 6 yo Caucasian male with +7.50D of uncorrected hyperopia will have..
Difficulty focusing (accommodating) to form a clear image at distance and/or near -even after proper correction for this child, VA may initially stay reduced OU. Brain needs time to adjust
What can high hyperopia cause and why?
Esotropia, from accommodating so much. Not always the case especially for kids who haven’t started school yet
Anisometropic amblyopia
Normal refractive error with good VA in one eye and a significant error and reduced VA in the other eye
-“that’s my bad eye”
Which type of amblyopia may be more difficult for parents to detect and why
Anisometropic amblyopia because the child relies heavily on the better seeing eye
What are some mistakes the Dr could make that would cause them to miss this diagnosis
- VA done with both eyes open
- not making sure that each eye is properly covered to prevent peeking
- skipping parts of the exam
- assumptions that little children cant have visual impairments
What are some tests that should be done if you suspect amblyopia
- cover test
- stereo
- retinoscopy
- ophthalmoscopy
Uncorrected refractive error causes a ________ that prevents the brain form getting clear information via the visual pathway
Constant blur
In a properly functioning visual pathway, the ___________ of the ________________ responds to high spatial frequency stimulation
- parvocellular layer
- lateral geniculate nucleus
Parvocellular layers in the poorer seeing eye
Not stimulated by blur
When is the effect of blur highest?
In the critical period of development of the visual system (in the first years of life)
Hyperopic anisometropia
Amblyopia resulting from a difference of hyperopia between the 2 eyes is common
What is the minimum of hyperopic anisometropia that can be problematic?
As little as +1.00D
What can as little as +1.00D of hyperopic anisometropia affect?
- proper fusion at distance and near
- cause amblyopia in the more hyperopic eye
If both eyes are hyperopic
The less hyperopic eye can maintain control, keep some motor and sensory function
What is something that could could develop from hyperopic anisometropia
Esotropia
What two entrance tests could be affected with hyperopic anisometropia?
- stereopsis
- W4D could show fusion depending on the severity of the amblyopia, you could also pick up a central scotoma
Myopic anisometropia
High unilateral myopia with lesser myopia in the other eye
If they have a significant difference in refraction between the two eyes
Most definitely amblyopia
Moderate myopic anisometropia (less than 5D)
OD: -0.75 Ds (used for distance)
OS: -3.25 Ds (advantage for near)
Amblyopia will likely NOT develop in this case because both eyes attain clarity at either distance or near **
Form deprivation
Obstruction of the line of sight that prevents a clear image to form on the retina
-can occur in one or both eyes
Physical obstructions that can lead to amblyopia include:
- congenital cataracts
- ptosis
- traumatic cataract
- corneal opacity
- vitreous opacity
- vitreous hemorrhage (shaken baby syndrome)
