Optics - Prisms Flashcards
For VERTICAL prisms, if they are the same (both myopic or hyperopic) are they additive or subtractive?
Subtractive!
For VERTICAL prism, if they are different are they additive or subtractive?
Additive!
For HORIZIONTAL prisms, if they are the same are they additive or subtractive?
Additive!
For HORIZONTAL prisms, if the are different are they additive or subtractive?
Subtractive!
A patient is viewing an object through base down prism using the left eye, what happens?
Induces a left HYPOtropia or right hypertropia.
Patients with what type of strabismus benefit from Prism correction?
Phoria, intermitent tropia, small / comitant deviations.
Where should a prism be placed in incomitant strabismus?
Place the prism over the eye with limited movements.
For Hyperopes ROUND top add does what to image displacement and what to image jump?
Minimizes, Maximize
For Hyperopes FLAT top add does what to image displacement and what to image jump?
Maximizes, Minimizes
A Prism displaces an IMAGE upward or downward? and REAL or Virtual
Upward and Virtual
Fresnel prism decrease vision how?
- Chromatic aberration 2. Glare
What is OPTICAL DOUBLING and give examples?
It eliminates the need to align a stationary ruler with the moving image of interest.
Keratometry, pachymetry, applanation tonometry.
How does indirect ophthalmoscope work?
The binocular eyepieces contain prism that utilize total internal reflection to reduce the observer’s interpupillary distance to about 15mm from 60mm.
How does small-pupil Indirect ophthalmoscope work and what is the tradeoff?
Decreases the IPD further but decreases the :
Depth perception and Increased Glare fro reflections.
IF a patient is MYOPIC in both eyes (-8,-4) how much prismatic effect will he have if he looks 1cm below?
4! For same lenses SUBTRACT… for opposite lenses ADD!
