D3- Physiological Optics & Binocular Vision Flashcards
Science that deals with the normal functions of living organism and their parts
Physiology
Study of sight and behavior of light
Optics
Visual science that deals with the study of structures of the eye and functions affected by behavior of light
Physiological Optics
Has the power to adjust to environmental changes
Animate
Stimulus not capable of responding
Inanimate
Something that causes physiological/psychological response
Stimulus
Receives the environmental stimuli
Receptor
A bodily organ which becomes active in response to stimulation
Effector
Strands of protoplasm which connects the two organs (receptor and effector)
Neurons
Refers to the refractive power of the lens
Dioptrics
Unit for measuring the dioptric power of the eye
Diopter
Ratio of speed of light in air to speed of light in other optical medium
Index of Refraction
Length of the eyeball
24 mm
Weight of an eyeball
10g
Volume of an eyeball
6.5 mL
3 coats/tunics of the eyeball
Fibrous coat
Uveal coat
Nervous coat
Fibrous coat comprises:
Sclera
Cornea
Limbus
White of the eyeball
Sclera
Hard and tough layer of the eye
Sclera
Main refractive apparatus of the eye
Cornea
By its transparency, permits light reach interior of the eye
Cornea
Transition zone between sclera and cornea
Limbus
Uveal coat comprises of:
Choroid
Ciliary body
Iris
Thin, dark membrane of the eye
Choroid
Nourishes the outer part of the retina
Choroid
Prolongation and thickening of the choroid
Ciliary body
Nourishes the cornea and lens through aqueous humor
Ciliary body
Serves as attachment of the zonular fibers
Ciliary body
Has pigmentation that gives color
Iris
Regulate the light entering the eye
Iris
Reduces chromatic and spherical abberations
Iris
Nervous coat comprises of:
Retina
Thin, transparent membrane upon which the images are cast and in where nerve impulses are generated
Retina
Mathematical or physical model that represents the basic optical features of the real eye
Schematic eye
Index of refraction of the CORNEA
1.376
Index of refraction of AQUEOUS HUMOR
1.336
2/3 of refraction of the eye
Cornea
Where cornea owes its clear optical surface
Tear Layer
Steeper curvature will result to?
Higher surface power
Flatter curvature will result to?
Lower surface power
1/3 refraction of the eye, important structure for ACCOMMODATION
Crystalline lens
Process which crystalline lens varies its focal length in response to changes in vergence
ACCOMMODATION
Dioptric adjustment of the eye to attain maximum sharpness of retinal imagery
ACCOMMODATION
If the accommodation is insufficient, object will fall in the?
Behind the retina
If the accommodation is insufficient, this is termed as?
Lag of accommodation
If the accommodation exceeds it is termed as?
Lead of accommodation
The relationship between posterior principal focus, refractive mechanism, and retina of the same eye with accomm relaxed
REFRACTIVE STATUS
Focal points of the refracting mechanisms
Posterior principal focus
Refractive medias
Cornea
Crystalline lens
Aqueous humor
Vitreous humor
Factors that influence refractive status:
Length of the eyeball
Power of cornea
Power of lens
Depth of anterior chamber
Posterior principal point is focused on the retina
Emmetropia
Posterior principal point focused in front or behind the retina
Ametropia
Process of seeing:
Physical process
Photo-chemical process
Neuro-muscular process
Psychological process
Process wherein an incident ray of light strikes the eye and its transmission through the various transparent media
Physical process
The transformation of a radiant energy at the neuro-epithelium into some other form of energy
Photochemical process
The generation of the nerve impulse in the retina and its transmission by a chain of neuron to the central nervous system
Neuro-muscular process
The interpretation of the stimulus received by the retina
Psychological process
A transparent membrane where images are cast and where nerve impulses are generated and converted to the optic nerve
Retina
Nerve of sight
Optic nerve
Posterior continuation of optic chiasma with its fibers terminating at lateral geniculate body
Optic tract
Serves as the end station for some visual fibers
Lateral geniculate body
Carry visual impulse to area striata
Optic radiation
Visual/optic center of the brain located at medial aspect of the occipital lobe
Area striata
Complete inability of the eye to see
Blindness
One eye is completely blind
Uniocular blindness
Half blindness
Hemianopsia/hemianopia
Loss of peripheral or central vision
Heteronymous hemianopsia
Both eyes are blind to either right or left side
Homonymous hemianopsia
Hemianopsia on both eyes are completely symmetrical in extent and intensity. Same size, shape, and position
Congrous hemianopsia
Visual field defects are dissimilar in both eyes
Incongrous hemianopsia
Scotoma wherein perception of light is entirely lost
Absolute scotoma
Scotoma wherein perception of light is only diminished
Relative scotoma
Scotoma that appears as black spot on the visual field. Patient is not aware.
Negative scotoma
Scotoma that appears as a dark spot in the visual field
Positive scotoma
Scotoma that involves the point of fixation
Central scotoma
Scotoma that involves the peripheral areas
Peripheral scotoma
Scotoma that appears usually in person with migraine
Scintillating scotoma
Scotoma that is an arch-like and an extension of blind spot. It is a symptom of early stages of glaucoma
Arcuate scotoma
Reflex that controls/regulates the intensity of light entering the eye
Pupillary light reflex
Greater intensity of light means the pupil is ______
Small
Lower intensity of light means the pupil is _____
Large
Smaller pupil means _____ light in
Less
Larger pupil means ______ light in
More
Stimulation of one retina by light produces a contraction of pupil on the same eye
Direct light reflex
Stimulation of one retina by light produces a contraction of pupil on the opposite eye
Consensual light reflex
Person looking at an object close to the face will cause contraction of the pupils
Accommodative convergence reflex
Nerve that is responsible for the afferent limb of pupillary reflex
Optic nerve
Nerve that is responsible for the efferent limb of the pupillary reflex
Oculomotor nerve
Lesion is from retina to nucleus
Relative afferent pupillary defect
Lesion is from pre-ganglionic to post ganglionic fiber
Relative efferent pupillary defect
Covers the fundamental knowledge based on scientific principles of light and its effect to the eye
Visual optics
Real sense organs of the body
Receptors
Nerves that connects the receptors to the effectors
Physiological connectors
Connects the receptors to the effectors
Sensory
Connects the CNS to the responding effectors
Motor
What are the visual pathways
Retina
Optic nerve
Optic chiasm
Optic tract
Lateral geniculate body
Optic radiation
Visual cortex
The retina consists of two parts
Retinal pigment epithelium
Neural retina
Dark pigments in the retina that absorbs light passing through the receptor layer
RPE
The neural retina contains five types of neurons
Visual receptor cells
Horizontal cells
Bipolar cells
Amacrine cells
Retinal ganglion cells
Part of the retina where image of the central visual field center is focused
Fovea
Part of the eye that is formed by the retinal ganglion cell axons that are exiting the retina
Optic disc
Pigments that is responsible for photopic vision
Cones
Pigments that is responsible for scotopic vision
Rods
Two locations in the retina that have no rods
Fovea and optic disc
Total number of cones in the retina
4% in the fovea, 96% in the periphery
Three different kinds of cones
S, M and L cones
Photopigment of S cone
Cyanolabe
Photopigment of M cone
Chlorolabe
Photopigment of L cone
Erythrolabe
The ability to detect and recognize small objects visually
Visual acuity
Field of vision that operates best under high illumination
Central vision
Field of vision that has the greatest visual acuity and color sensitivity
Central vision
Field of vision that is more sensitive to dim light
Peripheral vision
Field of vision that operates under low illumination
Peripheral vision
A small ________ is located in the temporal hemifield
Blindspot
Image formed by the optical system of the eye
Optical image
Image formed on the retina which may be either sharply focused or blur circle
Retinal image
The farther the optical image from the retina, the _______ the blur cirle
Bigger
The smaller the pupil, the ________ the blur circle
Smaller
The extent to which the image may be located in front or behind the retina and still appear to be clear
Depth of focus
The extent to which the object may be moved toward or away and yet remain clear with the same dioptric power
Depth of field
The ability to detect differences in the wavelength of light
Color vision
Color vision may be tested using:
Ishihara test plates
Farnsworth D-15
Anomaloscope
Lanterns
Having a sense of direction while moving around an environment
Spatial orientation
The process of producing a single image from the two disparate monocular images
Binocular fusion
The ability to perceive the distance of an object
Depth perception
If two objects are roughly the same size, the object that looks the largest will be judged as being closest to the observer
Relative size
As you are moving, objects that are closer seem to zoom by faster than do objects in the distance
Motion parallax
Objects that are farther away seem to be blurred or slightly hazy
Aerial perspective
Parallel lines appear to meet as they travel into the distance
Linear perspective
When one object overlaps another, the object is partially obscured is perceived as being farther away
Overlap
What are the refractive errors of the eye
Myopia
Hyperopia
Astigmatism
An inherited disorder in which there is a gradual and progressive failure to maintain receptor cells
Retinitis Pigmentosa
A symptom of this condition is night blindness and loss of peripheral vision
Retinitis Pigmentosa
A vitamin deficiency that can cause permanent blindness
Vitamin A deficiency
The leading cause of blindness in the elderly
Macular Degeneration
A form of macular degeneration which involves intraocular proliferation of cells in the macular area, fovea, and surrounding retinal areas
Dry ARMD
A form of macular degeneration where capillaries of the choroid invade the macular area
Wet ARMD
A condition where the neural retina is torn away from the RPE
Retinal detachment
A condition which involves microaneurysm and punctate hemorrhages in the retina
Diabetic retinopathy
What are the vitreoretinal sources of entoptic images?
Moore’s lightning streaks
Purkinje Figures
Entoptic images consisting of flashes of light on the visual field and is associated with stress
Moore’s lightning streaks
Appearance of tiny bright dots moving rapidly along squiggly lines in the visual field
Blue field phenomenon
A phenomenon caused by white blood cells moving in the capillaries in front of the retina
Blue field phenomenon
Is the perception of light without light actually entering the eye
Phosphene
Refers to an image continuing to appear in one’s vision after the exposure to the original image has cased
Afterimage
Aspect of things that is caused by differing qualities of the light reflected or emitted by an object
Colors
Sometimes called Chromatics or colorimetry
Science of color
It includes the perception of color by the human eye and brain
Chromatics
A color that is evoked by a single wavelength of light in the visible spectrum
Spectral color
A process that allows the brain to recognize a familiar object as being a consistent color
Color constancy
Theory that suggests that both the eye and brain are involve in color constancy
Retinex theory
Who discovered the retinex theory?
Edwin H. Land
He discovered the trichromat theory
Thomas Young
He discovered the opponent theory of colors
Ewald Hering
Theory that suggests that the ability of the human eye is to distinguish colors is based upon the varying sensitivity of photoreceptors in the retina
Trichromat theory
A region of luminance levels and color temperatures that are often viewed as comfortable or pleasing to an observer
Kruithof Curve
The ability to distinguish objects based on the wavelengths and frequencies of the light they reflect
Color vision
The ability to discriminate light on the basis of wavelength composition
Color vision
How many rods are in the eye
120 million
Where are rods located?
Peripheral retina
Rods has photopigment called
Rhodopsin
How many cones are in the eye
6-7 millions
Where are cones located?
Central retina
Cones has photosensitive protein called
Photopsin
The most common color vision deficiency
Deuteranomaly or Anomalous deuteranopsia
Color vision deficiency where the green-sensitive cones have decreased sensitivity
Deuteranomaly or Anomalous deuteranopsia
Referred to as “red weakness”
Protanomaly or Anomalous protanopia
A rare type of anomalous trichromatic vision
Tritanomaly
Color vision deficiency where the blue-sensitive cones have decreased sensitivity
Tritanomaly
A color vision deficiency where one of the three groups of cone cells is missing or not functioning
Dichromacy
The most common type of dichromacy
Protanopia
A type of dichromacy where the px is unable to spot red color and have difficulty spotting green color
Protanopia
A type of dichromacy where it does not have green cone cells making him or her unable to spot green color
Deuteranopia
The most rarest form of dichromacy having a ratio of 10 in 1 million people
Tritanopia
In this type of dichromacy, the patient is unable to distinguish between yellow and blue
Tritanopia
Reduced or complete loss of color discrimination
Achromatopsia
Refers to the complete loss of color vision
Rod monochromatism
Refers to incomplete loss of color vision
Cone monochromatism
Perceive everything just in shades of gray
Achromatopsia
Most commonly referred to as total color blindness
Achromatopsia
Test used for red-green color deficiencies
Ishihara color test
Ishihara color test is named after?
Dr. Shinobu Ishihara
Color vision test that consists of a number of colored plates each of which contains a circle of dots appearing randomized in color and size
Ishihara color test
Refers to a plate in Ishihara where individuals with color defect should see a different figure from individuals with normal color vision
Transformation plates
Refers to a plate in ishihara where only individuals with normal color vision could recognize the figure
Vanishing plates
Refers to a plate in Ishihara where only individuals with color vision defect could recognize the figure
Hidden digit plate
Color vision test that can be used to classify all three different forms or color vision deficiency
Hardy-Rand-Rittler
Intended to classify color vision defects by using a set of discs
D-15
This is accomplished by the arrangement of unsaturated colored discs
Lanthony desaturated d-15
Provides the most accurate way to test the severity of color blindness
Anomalosocpe
Coordinate use of BOTH eyes to produce single mental image
Binocular vision
Blending of sight to form single percept
Fusion
Proper coordination of eyes and brain
Neuroplasticity
Pre-requisites for single binocular vision
Frontally placed eyes, overlapping retinal fields
Partial decussation of the optic nerve fibers
Foveal region stimulated
Corresponding or identical points
Size of retinal images
Efficient functions of EOM and nerves
Equal size of retinal images
Iseikonia
Unequal size of retinal images
Aniseikonia
Equal best corrected VA
Iso-oxypia
Unequal best corrected VA
Aniso-oxyopia
High difference of refractive error
Anisometropia
Different refractive statuses
Antimetropia
Advantages of binocular vision
Single vision
Optical defects in one eye are made less obvious by the normal image of the other eye
Enlarged field of vision
Power to discriminate details and contours of an object is better with two eyes than one eye alone
Loss of one eye will seriously handicap the individual
Stereopsis
Compensation of blindspot and other differences
At what month the eyes are normally hyperopic
At birth
At what month the eyes follow light
In newborn
At what month the eyes follow large objects
At 2 months
At what month foveas are fully formed
At 3 months
At what month they hold objects
At 3 months
At what month eyes are expected to be straight
At 3-4 months
At what month they fixate an object for 1-2 min.
At 6 months
At what age the VA is at 20/70
1 year old
At what year does fusional mechanism becomes fully developed?
1-1 1/2 year old
At what age does accommodation develops with sharpening VA
at 3 years old
At what age is the age of emmetropization
7-12 years old
Binocular-like instrument that makes use of a SEPTUM to separate images
Stereoscope
The images used (plates) in stereoscope is called?
Stereogram
Light passing through a prism is bent towards the
BASE
Eyes looking through a prism is displaced on the
APEX
Object viewed through a prism is displaced on the
APEX
9 positions of gaze
Ortho
Dextroversion
Levoversion
Supraversion
Infraversion
Dextrosupraversion
Dextroinfraversion
Levosupraversion
Levoinfraversion
Movement of one eye only
Duction
Movement of one eye inwards
Adduction
Movement of one eye upwards
Supraduction
Movement of one eye downwards
Infraduction
Movement of the vertical corneal meridian of one eye outward
Exycloduction
Movement of the vertical corneal meridian of one eye inward
Incycloduction
Synchronous and symmetric movement of both eyes in same direction
Version
Synchronous and symmetric movement of both eyes in opposite direction
Vergence
Strongest, heaviest, broadest muscle
Medial rectus
Muscle that has the closest insertion from limbus
MR
Muscle that is innervated by CN #6
LR
Muscle that has no secondary and tertiary actions
LR
Muscle that has the farthest insertion from the limbus
SR
