PO. 2 MIDTERM Flashcards
REFLECTIONS OF OBJECTS FROM STRUCTURE OF THE EYE
PURKINJE SANSON IMAGES
ANTERIOR SURFACE OF THE CORNEA (ACTUALLY THE TEAR FILM) AND IS COMMONLY REFERRED TO AS “CORNEAL REFLEX
PURKINJE SANSON IMAGE I
POSTERIOR SURFACE OF THE CORNEA
purkinje sanson image II
FORMED A DISTANT OBJECT THE SIZE OF THE IMAGE FORMED BY A SPHERICAL MIRROR IS DIRECTLY PROPORTIONAL TO THE RADIUS OF CURVATURE OF THE REFLECTING SURFACE
PURKINJE SANSON IMAGE I
ANTERIOR SURFACE OF THE LENS
purkinje sanson image III
-POSTERIOR SURFACE OF THE LENS .
-IN THE UNACCOMMODATED STATE IMAGE IV IS THE SMALLEST PURKINJE IMAGE
PURKINJE SANSON IMAGE IV
100x Brightervthan purkinje II
purkinje I
20% brighter than purkinje III OR IV
purkinje II
the human eye has four media
cornea
aqueous humor (ant.chamber)
crystalline lens
vitreous humor (post. CHAMBER)
the Eye’s limitations and corrections
myopia
hyperopia
astigmatism
presbyopia
HOW THE EYE WORKS
light entry
pupil ADJUSTMENT
lens focusing
image formation
signal transmission
brain interpretation
is a complex and fascinating optical instrument that allows us to perceive the world around us
the human eye
-the eye is a system of coaxial spherical refracting surfaces.
-that is the center of curvature for the entire refracting surface lie on a common axis coaxial.
CENTERED OR HOMOCENTRIC
the refractive indices of the media that surround the REFRACTIng surfaces are uniform
cornea
aqueous
len
vitreous have unique but uniform indices of refraction
Gaussian theory of cardinal points three pairs
focal point
principal point
nodal point
used to determine the basic imaging properties of lens sych as image size location and orientation
CARDINAL POINTS
IMPORTANT REFERENCE POINT FOR ANY OPTICAL SYSTEM
CARDINAL POINTS
-LOCATION THROUGH WHICH ANY RAY FROM ANY ANGLE WILL UNDEVIATED.
-IF A RAY PASSES THROUGH THE NODAL POINT IT WILL NOT BE REFRACTED THAT IS IT WILL EXIT THE LENS WITH THE SAME ANGLE AT WHICH IT ENTERED.
NODAL POINT
6 cardinal points
1st and 2nd:focal point f,f’
1st and 2nd Nodal point N,n’
1st and 2nd principal P,P’
-THE POINT AT WHICH LIGHT IS PRICESLY FOCUSED ON THE RETINA .
-IS WHERE THE LIGHT FROM PARALLEL BUNDLE OF RAYS COMES TO FOCUS
FOCAL POINTS
THE POINT WHERE THE PRINCIPAL PLANES INTERSECT WITH THE OPTICAL AXIS
PRINCIPAL POINT
RADIU OF CURVATURE
POSITION
INDEX OF REFRACTION
KEY PARAMETERS
I,II,III PURKINJE IMAGES ARE ERECT AND THEREFORE WILL APPEAR TO MOVE IN THE SAME DIRECTION AS THE LIGHT
motion of the purkinje images
ANTERIOR AND POSTERIOR CORNEA
ANTERIOR AND POSTERIOR CRYSTALLINE LENS
major optical surface
against motion
PURKINJE IV IMAGE
THE LINE THAT CONNECTS FIXATION POINT AND THE FOVEA AND THAT PASSES THROUGH THE NODAL POINTS
VISUAL AXIS
the line connecting the centres of curvature of all REFRACTIng surfaces
OPTICAL AXIS
formed between the optical and visual axis at the nodal point in the average eye the optical axis is displaced temporarily
ANGLE ALPHA
From the fixation point to the centre of the entrance pupil (E) and then from the exit pupil (E’) to the fovea. clinical counterpart of the visual axis
LINE OF SIGHT
THE LINE FROM THE CENTRE OF THE ENTRANCE PUPIL THAT INTERSECT THE CORNEA IN A PERPENDICULAR MANNER. THE CLINICAL COUNTER PART OF THE OPTICAL AXIS
PUPILLARY AXIS
FORMED BETWEEN THE PUPILLARY AXIS AND THE LINE OF SIGHT AT THE CENTRE OF THE ENTRANCE PUPIL. THE CLINICAL COUNTERPART OF THE ANGLE ALPHA
ANGLE LAMBDA
FROM FIXATION POINT TO THE CENTRE OF ROTATION (AN IMAGINARY REFERENCE POINT FOR EYE MOVEMENTS THAT IS ABOUT 14 MM BEHIND THE CORNEA)
FIXATION AXIS
clinical variables
ANGLE LAMBDA (FIXATION STATUS)
CORNEAL RADIUS
FIXATION DISTANCE
PUPIL Size
ANGLES
GAMMA
ALPHA
KAPPA
LAMBDA
FORMED BETWEEN THE FIXATION AXIS AND THE OPTICAL AXIS AT THE EYE’S CENTRE OF ROTATION (C)
ANGLE GAMMA
AXES
F-FIXATION
O- OPTICAL
V-VISUAL
P-PUPILLARY
L-LINE OF SIGHT
