Astigmatism and Presbyopia Flashcards
Cornea has unequal curvature on the anterior surface
Corneal Astigmatism
Crystalline lens has an unequal curvature on the surface or in its layers
Lenticular Astigmatism
sum of corneal astigmatism and residual astigmatism
Total Astigmatism
adult patients eventually report visual difficulties when faced with gradually declining accommodative amplitude and near task demands.
Functional Presbyopia
condition in which virtually no accommodative ability remains.
Absolute presbyopia
Condition which can still be overcome by a hard or forced ciliary effort.
Facultative Presbyopia
two principal meridians are perpendicular to each other
regular astigmatism
three types of regular astigmatism
with-the-rule, against-the-rule, and oblique astigmatism
most common type of astigmatism based on the orientation of meridians
with-the-rule astigmatism
accommodative ability becomes insufficient for the patient’s usual near vision tasks at an earlier age than expected.
Pre-mature Presbyopia
condition in which near vision difficulties result from an apparent decrease in the AA in dim light.
Nocturnal Presbyopia
Minus cylinder axis around vertical meridian
Against-The-Rule (ATR) Astigmatism
two principal meridians are not perpendicular to each other
Irregular Astigmatism
one of the principal meridians is focused in front of the retina and the other is focused on the retina
Simple Myopic Astigmatism
one of the principal meridians is focused on the retina and the other is not focused on the retina
Simple Astigmatism
one of the principal meridians is focused behind the retina and the other is focused on the retina
Simple Hyperopic Astigmatism
true or false
In presbyopia, correction is by adding minus (-) lenses
false
A small scale snellen’s chart.
Near chart VA
With the use of contact lenses, some people choose to correct one eye for near and one eye for far.
monovision
How is astigmatism diagnosed?
Visual Acuity
Keratometry
Refraction
first accurate description of astigmatism as such is credited to ________________
Thomas Young
He was the first one to produce a distance test charts for Astigmatism.
John Green
the total of the degrees representing the two weakest (or two strongest) meridians for both eyes equals 180°
Symmetric
when the two weakest or the two strongest meridians of both eyes do not total 180°
Asymmetric
Lenses for astigmatism
Cylindrical Lenses
In what age does presbyopia starts?
40-50
Optometric management for presbyopia
Spectacles
Contact lens
+0.50sph=+1.25cylx70
+1.75=-1.25x160
-15.00x65=-1.00x155
-15.00sph=+14.00cylx155
+2.75x35=+1.25x125
+2.75sph=-1.50cylx125
