Astigmatism and Presbyopia Flashcards
(30 cards)
is equal to the difference in refracting power of the two principal meridians.
Amount of astigmatism
It happens when the cornea has unequal curvature on the anterior surface
Corneal Astigmatism
The sum of corneal astigmatism and residual astigmatism
Total Astigmatism
It has three types of astigmatism
Regular Astigmatism
The parallel rays of light do not come to a single point focus on or near the retina
Astigmatism
When two principal meridians are perpendicular to each other
Regular Astigmatism
A minus cylinder axis around the horizontal meridian
WTR Astigmatism
The minus cylinder axis is around the vertical meridian
ATR Astigmatism
This is associated with trauma, disease, or degeneration
Irregular Astigmatism
It happens when one of the principal meridians is focused on the retina and the other is focused on the retina with accommodation relaxed
Simple Astigmatism
Happens when both principal meridians are focused in front of the retina with accommodation relaxed
Compound Myopic Astigmatism
The sum of the two axis of the two eyes equals approximately 180
Symmetrical Astigmatism
This happens when you change the sphere in contact lens by diving the cylinder by two
Spherical Equivalent
The first accurate description of astigmatism is credited to whom?
Thomas Young
The first one to produce a distance test charts for astigmatism
John Green
It is not a disease but a physiological condition that affects everyone at a certain age
Presbyopia
It is also called as “short arm syndrome”
Presbyopia
At what age does Presbyopia occur?
40-50
It a lens based theory in which the amount of ciliary muscle contraction remains constant with age
H-H-G Theory
Nutritional changes, action UV rays and exposure to intense infrared radiation are the causes of what?
Sclerosis
It is the earliest stage at which symptoms or clinical findings document the near vision effects of the condition
Incipient Presbyopia
It has an etiology of functional presbyopia
Absolute Presbyopia
It is a condition which can still be overcome by a hard or forced ciliary effort
Facultative Presbyopia
It is the maximum increase in optical power that an eye can achieve
Amplitude of Accommodation
