What is a Purkinje image? How many of them are there? Where does/do it/they come from? What useful opthalmic instruement uses it?
No looking it up on the web. Uase your memory banks.
What is a Purkinje image? How many of them are there? Where does/do it/they come from? What useful opthalmic instruement uses it?
No looking it up on the web. Uase your memory banks.
It's an entopic phenomenon.Originally Posted by fjpod
oh, I see there is more than one question. well, there are several, such as reflections off the cornea, the lens, etc. then there's the purkinje tree.
Not sure what instrument uses them, other than a keratometer or ophthalmometer...
The pupillometer also uses Purkinje image I. There are a total of four -- one for each refracting surface.
Darryl J. Meister, ABOM
Another interesting "Purkinje" question: What is the Purkinje shift?
Darryl J. Meister, ABOM
They are virtual images that occur as light is reflected from each refracting surface of the eye. There are indeed four of them and they come from the anterior corneal surface#1, posterior corneal surface#2, anterior lens surface#3 and posterior lens surface#4. The order that they fall from front to back are 2,1,3,4. Keratometers use the first purkinge image to evaluate corneal curvature.
I am having trouble remembering the specifics on Purkinge shift and I don't want to put specifics on something that I feel may be wrong.
Also, the purkinge tree is the affect of a patient viewing the outline of their blood vessels as a light transilluminates the vascular regions of their eye. It looks like a bunch of tree branches. It is a little different than what I described in my previous post.
I think this has something to do with dark adaptation and seeing colors. I can't recall the specifics.
:cheers: Life is too short to drink cheap beer.
You're pretty close...I think this has something to do with dark adaptation and seeing colors. I can't recall the specifics
Darryl J. Meister, ABOM
That's about as close as I'm going to get with out looking it up.
:cheers: Life is too short to drink cheap beer.
I had to look it up so I won't post the answer. :finger:
Purkinje shift is where in the dark the eye adapt and becomes more sensitive to blue as (as opposed to red light). This has particular relevance to night time driving, and accounts for myopic shift at night
Yep. Though spherical aberration and involuntary accommodation are also causal factors in night myopia.
Darryl J. Meister, ABOM
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