P.O 2 Flashcards
-is a complex and fascinating optical instrument that allows us to perceive the world around us.
- it function much like a camera capturing light and forming images on light sensitive surface
THE HUMAN EYE
how the eye works:
- Light entry
- pupil ADJUSTMENT
- lens focusing
- image formation
- signal transmission
- brain interpretation
THE HUMAN EYE HAS A FOUR REFRACTIVE MEDIA
- cornea
- aqueous humor
(ant. chamber) - crystalline lens
- vitreous humor
(post. chamber)
THE HUMAN EYE LIMITATIONS AND CORRECTION
- myopia
- hyperopia
- astigmatism
- presbyopia
FROM COLORS AND SHAPES TO DISTANCE AND DEPTHS
Perceive the world around us
the eye’s role in our lives
- perceive the world around us
- interact with others
- enjoy activities
-the eye is a system of coaxial spherical refracting surfaces.
-that is the center of curvature for the entire refracting surfaces lie on a common axis coaxial
centered or homocentric
through the facial expressions, body language and eye contact
interact with other
Are used to determine the basic imagong properties of lens , such as image size location and orientation
CARDINAL POINTS
-I,II,III PURKINJE IMAGES ARE ERECT AND THEREFORE WILL APPEAR THE SAME DIRECTION AS THE LIGHT
-HOWEVER SINCE THE IV PURKINJE IMAGE IS INVERTED IT DEMONSTRATES.
MOTION OF THE PURKINJE IMAGES
the refractive indices of the media that surround the refracting surfaces are uniform
that are cornea, aqueous,lens, vitreous
from the fixation point to the centre of the entrance pupil (E) and then from the exit pupil (E’) to the fovea. the clinical counterpart of the visual axis.
LINE SIGHT
three pairs of cardinal points on the optical axis of a rotationally symmetric lens:
focal points
principal points
nodal points
6 cardinal points
FOCAL POINT F1 &F2
NODAL POINTS N1 &N2
PRINCIPAL POINTS P1& P2
-The point at which light is precisely focused on the retina.
-is where the light from a parallel bundle of rays comes to focus.
FOCAL POINTS
The points where the principal planes intersect with optical axis
PRINCIPAL POINT
-LOCATION THROUGH WHICH ANY RAY FROM ANY ANGLE WILL PASS UNDEVIATED
- IF A RAY PASSES THROUGH THE NODAL POINT IT WILL NOT BE REFRACTED THAT IS IT WILL EXIT LENS WITH THE SAME ANGLE AT WHICH IT ENTERED
NODAL POINT
cardinal point
p, p’= principal planes
n, n’= nodal point
f,f’= Focal point
the line from the centre of the entrance pupil that intersects the cornea in a perpendicular manner. the clinical counterpart of the optical axis
PUPILLARY AXIS
Formed between the pupillary axis and the line of sight at the centre counterpart of angle alpha
ANGEL LAMBDA
key parameters
-radius curvature
-position
-index refraction
MAJOR OPTICAL SURFACES
-anterior and posterior CORNEA
-ANTERIOR and posterior CRYSTALLINE LES
-REFLECTIONS OF OBJECT FROM THE STRUCTURE OF THE EYE.
PURKINJE SANSON IMAGES
ANTERIOR SURFACE OF THE CORNEA AND IT COMMONLY REFERRED TO AS CORNEAL REFLEX
PURKINJE SANSON IMAGE 1
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.
-Fact that image I tells you that the radius of curvature the Posterior surface of the cornea is shorter than the radius for anterior surface.
PURKINJE SANSON IMAGE II
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 brighter than purkinje II
purkinje I
20% brighter than purkinje III OR IV
PURKINJE II
FORMED BETWEEN THE FIXATION AXIS AND THE OPTICAL AXIS AT THE EYE’S CENTRE OF THE ROTATION (C)
ANGEL GAMMA
ANGELS
G-GAMMA
A-ALPHA
K,-KAPPA
L-LAMBDA
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 ( it is perpendicular to all REFRACTIng surfaces)
OPTICAL AXIS
FORMED BETWEEN THE OPTICAL AND VISUAL AXIS AT THE NODAL POINT IN THE AVERAGE EYE THE OPTICAL ACIS IS DISPLACED TEMPORARILY (ABOUT 5 DEG) AND DOWN (1.5 DEG) WITH RESPECT TO THE VISUAL AXIS
ANGLE ALPHA
clinical variables
Angle lambda (FIXATION status)
corneal radius
fixation distance
pupil size
Orbit and the extraocular muscles are embryologically derived from?
meso and neural crest cells
primary movement of superior oblique muscles
INTORSION
secondary movement of superior oblique muscles
Depression
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
AXES
F-fixation
O- Optical
V- visual
P-pupillary
L-line of sight
EOM MAJOR BLOOD SUPPLY
OPHTHALMIC ARTERYS MEDIAL AND LATERAL MUSCULAR BRANCH
BLOOD SUPPLY OF SR,IR, MR
SINGLE BRANCH OF THE LACROMAL ARTERY
OPHTHALMIC ARTERYS LATERAL MUSCULAR BRANCH
LR, SR,SO,LPS
OPHTHALMIC ARTERY MEDIAL MUSCULAR BRANCH
MR,IR,IO
fixation light held at ______
viewing distance
33cm
BLOOD SUPPLY OF MR,IR,IO
ophthalmic arterys medial muscular branch
Primary movement of inferior rectus
DEPRESSION
Secondary movement of inferior rectus
INTOSION
NERVE SUPPLY OF sr and LPS
CN III SUPERIOR DIVISION
Blood supply of inferior rectus and inferior oblique muscle
infraorbital artery a branch of the maxillary artery
PRIMARY MOVEMENT OF LATERAL RECTUS
ABDUCTION
NERVE SUPPLY OF MR,IR,IO
CN III INFERIOR DIVISION
TROCHLEAR NERVE INNERVATE
S.O
NERVE SUPPLY OF SO
CN IV
PRIMARY MOVEMENT
LR
NERVE SUPPLY OF LATERAL RECTUS
CN VI
THE ONLY EOM TO HAVE ITS ANATOMIC ORIGIN IN THE ANTERIOR ORBIT
IO
its origin is from orbital floor lateral to nasolacrimal groove
IO
TERTIARY MOVEMENT OF LATERAL RECTUS
NONE
sr lenght
42 MM
IO LENGTH
37, mm
SO LENGHT
60mm
MR LENGTH
40mm
IR LENGTH
40mm
IO LIMBUS INSERTION
5-14MM
SO LIMBUS INSERTION
7.7 MM
LR LIMBUS INSERTION
6.9mm
MR LIMBUS INSERTION
5.5mm
LR LENGTH
48mm
