Astigmasim and Presbyopia Flashcards
When parallel rays of light enter the eye with accommodation relaxed
Astigmatism
When the cornea has unequal curvature on the anterior surface
Corneal Astigmatism
When the crysalline lens has an unequal curvature on the surface or in its layer
Lenticular Astigmatism
Total Astigmatism= ________+ ________
Corneal +residual
When the two principal meridians are perpendicular to each other
Regular Astigmatism
Minus cylinder axis around horizontal meridian
Also 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
When the two principal meridians are not perpendicular to each other
Irregular Astigmatism
When one of the principal meridians is focused in front of the retina and the other is focused behind the retina
Mixed Astigmatism
When both principal meridians are focused behind the retina with accommodation relaxed
Compound hyperopic Astigmatism
Give at least 3 clinical test for Astigmatism
Autorefraction
Keratotomy
Retinoscopy
Symptoms of Astigmatism
Distorted vision at distance and near
Headaches
Squinting
Prevalence of Astigmatism
Age
Gender
Ethnicity
The principal meridians or axes of the two eyes are not symmetrical
Asymmetrical Astigmatism
Both eyes are WTR Astigmatism, and the sum of the two axes equal approximately 180
Symmetrical Astigmatism
The inability of the human eye to focus on objects up close that results with aging
Presbyopia
The amount of ciliary muscle contraction or effort/innervation required to produce a unit of change
H-H-G theory
The amount of cilliary muscle contraction needed to produce a unit change
D-D-F theory
Is the condition in which virtually no accomodative ability remains
Absolute presbyopia
Condition which can still be overcome by a hard or forced cilliary effort
Facultative presbyopia
The condition in which near vision difficulties results from an apparent decrease in the AA in dim light.
Nocturnal Presbyopia
Symptoms of Presbyopia
Occipital headache
Diplopia
Pain around the eyes
Dizziness
Mild laser hear is used in a three-second procedure to shrink collagen
Laser Thermal keratoplasty
Is the maximum increase in optical power that an eye can achieve in adjusting its focus from as far as possible to the nearest possible
Amplitude or Accommodation
A Small scale snellen’s chart
Near Chart VA
Corrections for Presbyopia
Bifocals
Reading glasses
With the use of contact lenses, it also eliminates the need for bifocal or reading glasses
Monovision
Causes of Sclerosis
Nutritional changes
The earliest stage at which symptoms or clinical findings documents the near visions effect of the condition
Incipient Presbyopia
Adults patients eventually reports visual difficulties when faced with gradually declining accommodation amplitude
Functional presbyopia
