Astigmatism Flashcards
An unequal curvature of the cornea on the anterior surface
Corneal Astigmatism
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
Composes the residual astigmatism
Posterior Corneal Surface
Lenticular Surface
Lenticular Zonule
When the two principal meridians are perpendicular to each other.
Regular Astigmatism
The ““most common type of astigmatism based on the orientation of meridians
With-The-Rule (WTR) Astigmatism
Minus cylinder axis around vertical meridian
Against-The-Rule (ATR) Astigmatism
Curvature of any one meridian is not uniform
Irregular Astigmatism
VA is often not correctable to 20/20
Irregular Astigmatism
When one of the principal meridians is focused in front of the retina and the other is focused on the retina with accommodation is relaxed
Simple Myopic Astigmatism
When both principal meridians are focused either in front or behind the retina when accommodation is relaxed
Compound Astigmatism
When one of the principal meridians is focused in front of the retina and the other is focused behind the retina when accommodation is relaxed
Mixed Astigmatism
The principal meridians or axes of the two eyes are symmetrical
Symmetrical Astigmatism
The principal meridians or axes of the two eyes are not symmetrical
Asymmetrical Astigmatism
When parallel rays of light enter the eye and do not come to a single point focus on or near the retina
Astigmatism
