Lecture 5 - Pupillary Optics Flashcards
What forms the Aperture stop of the eye?
The iris
The opening of the Aperture stop is known as the ???
Pupil
What two muscles control the Pupil size?
The Sphincter pupillae - for pupil constriction
The dilator pupillae- for pupil dilation
The iris is designed to prevent undesirable light from getting to the lens/retina.
It is designed to absorb light
Iris is designed to have Melanin granules in stroma and epithelium (Brown eyes)
Blue and green irises has granules only in epithelium
Iris is a unique Biometric identification system. The most reliable one!
Job Description of the Iris
- Stops undesirable light (pigmented tissue)
Pupil is an important optical system
The ??? Of an optical system is the image of the aperture stop formed in object space (Image formed by the ???)
The ??? Is the image of the aperture stop formed in the image space. (Image formed by the ???)
???? Is an erect, virtual image formed 0.5mm in front of the real pupil
Entrance pupil, formed by the cornea
Exit pupil, formed by the lens
Entrance pupil
The level of illumination is the most important factor affecting pupil size.
Depending on illumination, pupil varies from 2-8mm in diameter
The ??? To an increase in illumination by a decrease in pupil size.
Latency:
With low illumination, latency of 0.5 secs before ???
With increase illumination, latency decrease to 0.2 or 0.3 seconds
Pupil Centration
Pupil is decentered by 0.5mm ??? Relative to the Optical axis
The pupil response
Nasally
Field of view:
???, if light distribution in the central visual field.
???, if light distribution in the peripheral visual field
Pupil response to changes in light level is mediated by both rod and cone photoreceptors.
Direct light reflex
The constriction of the pupil due to direct light stimulation
Consensual light reflex
Pupils of both eyes respond equally to stimulation of only one eye
Near reflex
The pupil decreases in diameter when the eyes converge or accommodate
More response
Less response
Age
The pupil size ??? With increase in age
Drugs
Pupil dilation - ???
Pupil constriction - ???
Psychological factors
Emotional state affects the pupil size
Pleasant mental images increases pupil size and unpleasant mental images decreases pupil size
Decreases
Mydriatics
Miotics
Depth-of-field
A decrease in pupil size ??? The depth of field
The range of distances over which the system’s detector cannot detect any change in focus is called the ???
This range may be specified by a movement of the object plane or by the corresponding movement of the image plane.
Increases
Depth-of-field
Retinal Light Level
Pupil diameter affects the retinal light level
It is expected about 50-90% of the light entering the eye reaches the retina
Light entering the eye and reaching fovea depends upon the entry point in the pupil
Nothing
Retinal Image quality and visual performance
For ??? Pupil diameters, ??? Cause deterioration in retinal image quality.
For ??? Pupil diameters, ??? Limits image quality
There is an optimum pupil diameter range of 2-3mm that gives the best balance between these two effects for the corrected eye.
Large, aberrations
Small, diffraction
