Optics: Purkinji Images Flashcards
Image formed by reflection off the optical surfaces of the eye are referred to as __________
Purkinji image
Four main refracting surfaces of the eye:
-anterior corneal surface
-posterior corneal surface
-anterior lens surface
-posterior lens surface
Since there are 4 reflecting surfaces, there are four purkinji images numbered:
I, II, III, IV
Purkinji image formation order:
-II
-I
-IV
-III
Which purkinji image is the closest?
II
Which purkinji image is the farthest?
III
Purkinji reflection of I,II, and III form a _______ and ________ image
Virtual and erect
Purkinji reflection of IV forms a ________ and __________ image
Real and inverted
Purkinji reflection of the ________________ produces the strongest reflection
Anterior cornea (I)
Image formed by the ____________ has the most magnification (2X)
Anterior lens (III)
The first three images are formed by __________ reflecting surfaces
Convex
The fourth purkinji image is formed by a ____________ reflecting surface
Concave
The size and location of purkinji image III changes during _____________
Accommodation
(Decreases in size and moves closer to the surface)
anterior lens surface radius of curvature decreases during __________________
Accommodation
Purkinji images are important in several eye care applications:
-keratometry
-corneal topographers
-hirschberg test
-alignment of optical instruments with the eye (autorefractors, aberrometers and pupillometers)
-measurement of lenticular surfaces when measuring accommodation
-alignment and orientation during refractive surgery
Keratometry is the measurement of curvature of cornea based on the ____ purkinji image
1st
Keratometric is useful for….
Fitting contact lenses
Corneal topographers
Clinical instruments used to determine the shape of the cornea and utilize purkinji image 1
In the Hirschberg test the clinician views purkinji image ____when measuring angle _______
1, kappa
Hirschberg test is used to determine…
The amount of eccentric fixation and measure the angle of strabismus
In hirschberg test, if both eyes are aligned with the fixation light then…
Purkinji image I is located in the same position in each eye
In a left eye exotropia when performing Hirschberg, the left eyes purkinji image is…
Located closes to the nasal edge of the pupil
Each parameter of the purkinji image depends on…
IOL power, material, steps, and chromophores
If the light is coming from infinity, to find f, you can…
Divide r by 2
Corneal topographers are useful for:
-fitting CLs
-pre and post refractive surgery
-diagnosing certain conditions like keratoconus
