Javal’ rule assumes the average person has about how much astigmatism?
0.50D against the rule of lenticular astigmatism must be added to the corneal astigmatism
What is the height of a 20 foot letter at the testing distance of 20 feet?
 8.75 mm
Which of the following is most appropriate add for a 50 year-old emmetrope? assume the working distance is about 40 cm
Number one: what is the minimum accommodation for his age?
15-age/4
15-50/4=2.5D
Number two: what is the accommodative demand?
1/.40=2.5
Remember that you can only use half of your accommodation. So 1.25 diopters subtracted from the visual demand. Leaves us with a +1.25 add
What prescription will likely result in refractive amblyopia?
Anisometropia of greater than +1.50 DS in hyperopia or greater than -3 dpt in myopia.
What isometropic refractive error will lead to refractive amblyopia?
Isometropia of astigmatism greater than -2.50 diopters, hyperopia greater than +5diopter or myopia greater than -8DS .
A person who has a high AC/a ratio can be described as having divergence ____ or convergence ___
A person who has a high AC/a ratio can be described as having divergence excess or convergence excess
Accommodated facility test what?
The speed at which a patient can alternatively increase and then decrease their accommodation. In other words, stimulates or relax accommodation.
How to perform the accommodative facility test
Alternate between +1.5 and -1.5 lenses and switch once the image is brought into focus.
The CA/C ratio describes
Amount of accommodation elicited by convergence.
Binocular convergence can drive accommodation.
CA/C ratio is low in presbyopes and myope because
There is none existing in presbyopes and unnecessary in myope
Myope don’t have issue accommodating
Large Base in prisms placed in front of both eyes can mimic
Esotropia
When the angle of deviation remains fairly constant in all fields of gaze, the strabismus is considered
Comitant
indicates a decompensated phoria
No Comitant deviation deviation is not constant. indicates a muscle restriction
ESO deviation that increases on upward gaze shows what pattern
A pattern esotropia
Photokeratoscope use
maps the curvature of the cornea by analyzing the reflection of these rings from the eye’s surface
Refractive surgeries or for astigmatism assessment
Which instrument is needed for compression gonioscopy
Gonio 4 mirror lens
A reduced accommodative facility under binocular condition indicates what kind of problem
Vergence problem , not accommodative
