Optics: Optical Models Of The Eye Flashcards
Use of schematic model eye:
-physical models for calibrating instruments
-retinal image size
-retinal light levels
-refractive errors
-power of IOL following cataract surgery
-retinal image quality
-designing glasses, cl, and IOL
-customization
-imaging instruments
-one-off types of problems
What is an optical model eye?
-summarizes and organizes our understanding of the eye as an optical system
-provides conceptual framework for thinking how the retinal image is formed to launch the visual process
Two categories of eye models:
- Encyclopedia
- The toy train
The encyclopedia concept of model eye
A model eye is a mechanistic summary of everything we know about the eyes optical system and how it works
The toy train concept of the model eye:
-a model eye is a working device that mimics the functional behavior of real eyes
-can have variety of embodiments
Different embodiments of model eye:
-physical
-mathematical
-computational
How is the encyclopedia category of model eye used?
To store and retrieve knowledge
Advantage of encyclopedia eye model category
A compact, working representation of knowledge about ocular mechanisms
Disadvantage to encyclopedia eye model category
When all details are included the model may be too complicated to use
Working model eyes are used for…
Utilitarian tools for problem solving
Advantage to working model eyes
Real-world problems get solved
DisAdvantage to working model eyes
May oversimplify important features of the eye, structurally or mechanistically
Cardinal points were invented by __________ and applied to the eye by ___________________ to make imaging by thick optical systems easier to analyze in the paraxial domain
Gauss, Listing & donders
Le grands schematic eye has ___ refracting surfaces:
4
-two corneal
-two lens
Gullstrand-emsley eye model has ____ refracting surfaces:
3
-one cornea
-two lens
What are the 6 cardinal points of the eye invented by __________?
Gauss,
-two principal points
-two focal points
-two nodal points
Single refracting surface or reduced eye has…
one refracting surface is the simplest of the schematic eyes
Reduced eyes are anatomically inaccurate because…
There is no crystalline lens and there is an extra powerful cornea and having a short length
Reduced eyes are good for learning about:
-refractive error
-astigmatism
-blur
-effects on retinal image
Models with equal cardinal points are ________________________
Functionally equivalent
First focus:
Axial object position for which the image will be formed at infinity
Second focus:
Axial image point of an infinitely distant object
Nodal point shave the property that….
Any incident ray which passes through the 1st nodal point leaves the system from the second nodal point and parallel to the incident ray
1st principal point located where…
the exiting rays parallel to the optical axis intersect the refracted rays coming from the first focal point
2nd principal point located where
The incident rays parallel to the optical axis intersect the refracted rays coming from the 1st focal point
Summary parameters, like power and focal length of the eye are derived from….
Analysis of schematic eyes
At the beginning of the 19th century _____________ introduced the idea of making a schematic for the individual which he did for himself using his own eye
Thomas young
___________introduced average schematic eye and reduced it to cardinal points
Listing
Cardinal points enabled calculation of…
Image size without concern for anatomical details
In the 20th century eye models became more complete, complex, and anatomically correct and mechanistic:
-better biometrics
-discrete approx. to continuous GRIN profile
-changes over lifespan
-development and progression of refractive error
-aspheric surfaces to account for
