Astigmatism and Presbyopia Flashcards
Has an unequal curvature on its anterior surface
Cornea
The crystalline lens has an unequal curvature on its surface or in its layers
Lens
When the cornea has unequal curvature on the anterior surface
Corneal Astigmatism
When the crystalline lens has an unequal curvature on the surface or in its layers
Lenticular Astigmatism
The sum of corneal astigmatism and residual astigmatism
Total Astigmatism
Give at least one type of Astigmatism
With-The-Rule (WTR) Astigmatism
When both principal meridians are focused either in front or behind the retina (with accommodation relaxed)
Compound Astigmatism
When one of the principal meridians is focused on the retina and the other is not focused on the retina (with accommodation relaxed)
Simple Atigmatism
When one of the principal meridian is focused in front of the retina and the other is focused behind the retina (with accommodation relaxed)
Mixed Astigmatism
The sum of the two axes of the two eyes equals to 180
Symmetrical Astigmatism
The sum of the two axes of the two eyes does not equal to 180
Asymmetrical Astigmatism
Decreased visual acuities at distance and near
Signs
Give at least two optometric management for astigmatism
- Toric Contact Lenses
* Cylindrical Lens
Two types of contact lenses for astigmatism
- Toric Soft Contact Lenses
* Toric Rigid gas permeable contact lenses
The first accurate description of astigmatism as such is credited to
Thomas Young
It is also known as “short arm syndrome”
Presbyopia
It is a theory that based on Lens
H-H-G Theory
It is a theory that based on Muscle based
D-D-F Theory
Patients are symptomatic at an early age
Functional Presbyopia
Condition which can still be overcome by a hard or forced ciliary effort
Facultative Presbyopia
It is a Presbyopia that the etiology is Functional Presbyopia
Absolute Presbyopia
It is a Presbyopia that due to environmental, nutritional, disease related, or drug-induced causes
Pre-mature Presbyopia
It is a Presbyopia that increased pupil size and decreased depth of are usually responsible for this
Nocturnal Presbyopia
DD-NN is what is our guide in what optometric management?
Monovision
It is a Presbyopia that performs well on vision testing
Incipient Presbyopia
Focused in front of the retina and the other is focused on the retina
Simple Myopic Astigmatism
Focused behind the retina and the other is focused on the retina
Simple Hyperopic Astigmatism
When both principal meridians are focused in front of the retina
Compound Myopic Astigmatism
When both principal meridians are focused behind the retina
Compound Hyperopic Astigmatism
Give two examples of astigmatic charts
- Fan Dial
* Clock Dial
