Physiological Optics Flashcards by Dr. Kim Sefuentes

group of end organs of sensory afferent neurons specialized to be sensitive to stimulating agents

receptors

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sense organ that pertains to the various organs wirh specialized mechanisms, by means of which serves to protect and modulate the receptors

physiologic connectors

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the “impinging” of an incident ray of light upon the eye and its transmission through various refractive media of the eye

physical process

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the photoreceptor layer of the retina is the site where the light is absorbed and transformed into electrical impulses where it is called

photo transduction

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refers to the stimulus-altering events where in a physical stimulus is converted into action-potential, which is transmitted along axons towards CNS for integration

sensory transduction

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term given to the lateral half of the visual field has blindness

hemianopsia

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type of anisocoria where there is more than 0.5 mm difference to both pupil size

pathological anisocoria

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blood vessel that supplies 80% of the blood on the retina

choriocapillaries

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disease that could cause argyll robertson’s pupil

neuro syphilis

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bacteria or microorganism causes argyll robertson’s pupil

treponema pallidum

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visual field defect if there is lesion on optic chiasma

binasal heteronymous hemianopsia

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called the temporal or external optic radiation

meyer’s loop

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supplies the mucin layer on the pre corneal tear film

goblet cells of the conjunctiva

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supplies oil layer on the pre corneal tear film

meibomian gland

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area of the keenest vision

fovea

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thickest layer of the cornea

corneal stroma

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layer on the retina where phototransduction takes place

photoreceptor cell layer

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swingin flashlight is a test that is commonly done to check if there is a presence of

marcus gunn pupil

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higher order of visual system for visual information stream that reacts ro eye and hand movements in an environment

dorsal stream pathway

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reflexive movement to keep things constant while head is moving

vestibulo ocular

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part of visual pathway affected when theres visual field defect of right homonymous hemianopsia.

lateral geniculate body (left)

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science that deals with the normal functions of living organisms and their parts

physiology

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study of sight and behavior of light; concerned with vision and the generation, propagation, and behavior of electromagnetic light

optics

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visual science that deals with the study of the eye and their functions as affected by the behavior of light such as refraction, absorption, reflection and dispersion

physiological optics

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covers the fundamental knowledge based on scientific principles of light and its effect to the eye. Application of these principles in optometric solutions which can assist the optometrist in optometry care and practice

visual optics

differentate animate from inanimate body

stimulus response phenomenon

has the capability to adjust to environmental changes

animate

has no power of responding to environmental changes

inanimate

something that causes a physiological/psychological response something external that influences an activity

stimulus

structures that receive the environmental stimuli and produce an informative nerve impluse from it

receptor (sensory receptor)

3 distinct type of organs thats making possible for adjustment or response to be adaptive

receptors effectors physiological connectors

these organs in which the irritability to environmental changes (stimuli) is highly developed

receptor (sensory receptor)

a bodily organ (gland/muscle) that becomes active in response to stimulation

effector (responding organ)

more commobly known as neurons

physiological connectors

responsible for muscle contraction/ body movements

muscles

responsible for glandular secretions

glands

connects the receptor to the CNS (Afferent)

sensory receptor

connects CNS to the responding effectors (efferent)

responding organ

strands of protoplasm which connects the two organs (receptors and effector)

physiological connectors

the impulse received by the effectir throws gland into action

secrete

when neurons have an intimate contact with receptors, and the change in set up in the receptor causes a distrubance in the neuron, this is known as

nerve impulse

the impluse received by the effector throw in muscle into action

contract

accessory organs do

serve to protect the receptor converys the stimulus to the receptors provide a nourishment to the receptor

accessory organs for vision

retina optic nerve optic chiasma optic tract LGB optic radiation visual cortex (area 17)

refers to the refractive power of the lens or system of lenses

dioptrics of the eye

factors affecting the refractive power of the eye

index of refraction radius of curvature

straight line extending from the center of a circle or sphere to the curve or surface

radius of curvature

eyeball shape

slightly elongated sphere

length of the eyeball antero postero

22mm (other 2 diameter)

eyeball shape

slightly elongated sphere

length of the eyeball antero postero

22mm (other 2 diameter)

wieght of the eyeball

10 grams

volume of the eyeball

6.5 ml (aqueous and vitreous)

eyeball is suspended on the orbit by

ligament of lockwood

transparent medias of the eye

tear film cornea aqueous humor crystalline lens vitreous humor

eyeball is composed of 3 coats/ tunics

fibrous coat uveal coat nervous coat

outermost coat

fibrous/sclero corneal coat

structures inside fibrous/sclero corneal coat

scleara cornea limbus/sclero corneal junction

white of the eyeball

sclera

occupy 5/6 of the eyeball

sclera

hard and tough layer of the eyeball

sclera

function is protective covering against various forms of injury of the eyeball

sclera

maintains the globular shape of the eyeball

sclera

firm surface for the attachment of muscles

sclera

being failry opaque, aids in excluding extraneous light

sclera

maintain refractive apparatus of the eye

cornea

cornea occupies __ of the eyeball

1/6

by its rigidity , gives eyeball constant shape

cornea

because of cornea's transparency,

it permits light to reach interior of the eye

refracts light rays

cornea

by its extreme sensitivity, aids in protecting the eye

cornea

transition zone between sclera and cornea

limbus/sclero-corneal junction

middle layer (coat)

uvea/vascular coat

structures inside the uvea/ vascular coat

choroid cillary body iris

why choroid is a dark membrane

due to melanocytes

covers about 5/6 of the interior of the eyeball

choroid

nourishing coat of the eye

choroid

part of the cornea that choroid nourishes

outer part (rpe & photoreceptors)

prevents dispersion of the light, thus attains clear image of an object

choroid

blood rich tissue whose structures work together to produce aqueous humor

cillary body

nourishes the cornea and lens throygh aqueous humor

cillary body

serves as attachment of zonular fibers

cillary body

reduces chromatic and spherical aberrations - increasing VA

iris

perforated at its center by an aperture

iris

thin circular membrane hanging behind the cornea and in front of the lens

iris

innermost and most important layer

nervous/ functional coat

thin, transparent membrane upon which the images are cast and in where nerve impulses are generated

retina

for dim illum scotopic vision

rods

for day illum/photopic vision, color perception

cones

for transmission of visual and pupillary impulses

nerve fibers

adaptation that is quicker because the cone photopigment easily regenerates

light (bright)

IR cornea

1.376

IR of Aqueous humor

1.336

IR of crystalline lens nucleus

1.406

IR of crystalline lens cortex

1.386

IR of vitreous humor

1.336

made a single surface model for simplicity and speed of ray tracing

emsley

made six surface eye model (crystalline lens with a high index core and a low shell)

gullstrand

Angle Kappa is the angle formed at the intersection of the:

visual axis and pupillary axis

Pupillary light reflex falling nasal to the pupil is __ angle kappa and what strab

positibe angle kappa and exotropia

Large disparities in images give rise to:

diplopia

The muscle in the same eye that acts in the direction opposite to that of the primary muscle

antagonist

Conjugate eye movements are termed as:

versions

refractive power of the eye with relaxed accommodation?

58.64 D

line joining the anterior & posterior pole of the eye where the centers of curvature of the refracting surfaces & the cardinal points are located.

optic axis

A line image of a distant point source produced by an astigmatic optical system.

focal line

Among the retinal field which has the highest type of retinal sensitivity?

color field

A line image of a distant point source produced by an astigmatic optical system.

focal line

A kind of visual field that is limited to the brow, cheek bone and nose.

relative field

projected area of retina which when stimulated enables observer to detect presence of moving object.

motion field

tumor in the pituitary gland will manifest what kind of hemianopsia?

binasal hemianopsia

Any lesion affecting posterior to the optic chiasm will result to

binocular defect

Anabolism of red-green substance will produce:

green

Mixing blue and red color paints will produce:

violet

theory that stated that only the three wavelength – red, green and blue, are required to elicit all color sensations the human visual sensation is capable of experiencing:

Young–Helmholtz Trichromatic Theory

theory of color vision that stated that our vision is tetrachromatic in nature.

young helmoltz theory

theory of color vision that assumes that there are 3 different kinds of substances found in the same part of the visual mechanism responsible for color perception.

hering

Index of Refraction of Aqueous Humor.

1.33

law states that existence of corresponding retinal elements with their common relative subjective visual direction is the essence of binocular vision.

law of sensory correspondence

the fovea of the one eye bears common visual direction in the other extrafoveal area of the other eye.

ARC

Ability of the eye to align in such a manner that fusion can still be maintained.

motor fusion

Eccentric fixation can be detected by:

visuoscope

The site for vergence system control is located in the:

midbrain

Yoke muscles involve in right-up gaze are:

RSR, LIO

work-up among the following will help in the treatment of a V-pattern esotropia

superior oblique traction test lateral versions Bielschowsky head tilt test

Dioptric power of the Cornea during maximum accommodation.

43. 00D

He said that light produces a change in the body only when the object/body absorbs the vibrations of light.

draper

he postulated the Opponent Theory of Color Vision:

hering

A method of color mixing that is based upon the positive after image where the positive image of the previous stimulation fused with the primary image of the succeeding stimulus.

physiological method

white light passes through a prism it produces spectral colors. It is called:

dispersion

Fibrous Coat of the eye

sclero corneal coat

performing cover-uncover test, the examiner notices that the uncovered eye moves in order to fixate on the target. What does this probably represent?

tropia

tested when the cardinal position of gaze is evaluated?

function of the 6 EOM

Often used for cycloplegic refraction in young, actively accommodating children with suspected latent hyperopia or accommodative esotropia.

cyclopentolate

type of strabismus may experience the eye to drift occasionally, such as when they are very tired, feeling sick, or after drinking alcohol, despite their efforts to refocus.

intermittent

Binocular directionality is:

egocentric

FM radio is the source of:

microwave

primary muscle that moves the eye in a given direction:

agonist

refractive index of the lens

1.39

A thin transparent hyaline collagenous membrane w/e surrounds the lens completely

lens capsule

Consist of cuboidal cells w/c are polygonal in flat section, their nuclei are round & located slightly apical.

central zone

refractive index of the lens

1.39

In cover uncover test, Covered eye moves when uncovered, this indicates presence of what deviation

phoria

in cover uncover test, covered eye moves when uncovered, this indicates presence of what deviation

phoria

term for an optical state with equal refraction in the two eyes?

isometropia

it's a simplified schematic eye model, though it provides a more detailed representation of the eye's optical components. Older model but useful for basic understanding, incorporates multiple refractive surfaces (cornea and lens)

Listing's Reduced Eye

detailed and multi-surface schematic eye model (most accurate, includes six refractive surfaces)

gullstrand's schematic eye

who developed the most authoritative model of the eye.

gullstrand

the essential parameters that Gullstrand needed

a. curvatures of the surfaces of the cornea and lens b. their positions c. indices of refraction of the ocular media.

represents the eye as a single refracting surface (cornea), a simplified model, useful for understanding basic optical principles but doesn't accurately reflect the complexity of the real eye.

Emsley's Model Eye

represents the eye as a single refracting surface (cornea), a simplified model, useful for understanding basic optical principles but doesn't accurately reflect the complexity of the real eye.

Emsley's Model Eye

schematic sye which is simplified with just one refractive surface; used for quick calculations.

reduced eye

Not a refractive power component itself, but affects refractive status.

axial length of the eye

refractive error if eye is longer

myopia

refractive error if eye is shorter

hyperopia

4 types of schematic eye

Listing's reduced eye gullstrand's schematic eye emsley model reduced eye

schematic eye which is simplified with just one refractive surface; used for quick calculations.

reduced eye

4 types of schematic eye

Listing's reduced eye gullstrand's schematic eye emsley model reduced eye

What happens to the effective power of a lens when it is positioned more anteriorly (moved forward)?

effective power increases

In post-cataract surgery, if an intraocular lens (IOL) is placed more anteriorly than intended, it will result in a

myopic shift

What happens to the effective power of a lens when it is positioned more posteriorly (moved backward)?

The effective power decreases

Posterior displacement of a natural lens due to trauma can cause a

hyperopic shift

In post-cataract surgery, if an intraocular lens (IOL) is placed more anteriorly than intended, it will result in a

myopic shift

Cytoarchitecture of retina meaning

detach/attach

Segment of rods & cones wherein it is also called transverse disc that consist the photopigment and visual pigment

Outer Segment

Segment of rods & cones wherein it contains cilia that transmit nerve electrical impulse

Inner Segment

Helping cell of bipolar in releasing GABA

Muller

Image forming activities

Rods & cones

Type of eyelid closure that is voluntary

Winking

Type of eyelid closure that is involuntary

Blinking

Dispersive media

Cornea & lens

part of the central nervous system that is required for visual, perception, processing, and interpreting visual informations to build a representation of the visual environment

visual system

it detectz and interprets information drom the optical spectrum perceptible to that species to build a representation of the surrounding environment

visual system

parts of the CNS

Retina optic nerve optic tract visual cortex

also known as the perceptual system

visual system

are a special class of retinal cells that play a key role in non image forming visual functions, they respond to light but not for seeing objects. Instead, they help regulate biological rythmas, mood, and pupil response

ipRGCs Intrinsically Photosensitive Retinal Ganglion Cells

the neuropsychological side of visual information processing is known as

visual perception

visual system carries out a number of complex tasks including:

• pereception of light • formation of monocular neural representations • colour vision • stereopsis • identification of objects • motion perception analysis and integration of visual information • pattern recognition • accurate motor coordination under visual guidance • The neuropsychological side of visual information processing is known as visual perception. • Non-image forming visual functions, independent of visual perception, include (among others) the pupillary light reflex (PLR) and circadian photoentrainment.

they carry out the body's response to stimuli

effectors

are specialized to respond to one kind of stimulis more efficiently than others

receptors

the object of the protoplasmic changes in the receptor as the result of stimulation is to ___ the organism with the environmental changes and thereby enable organism to adjust itself to these changes

acquaint

pertains to the various organs or structures that consist of specialized nerve endings

sense organs

structures that helps to convey stimulus to the receptors , for protection and nourishment, they may be called the

accessory organs of the receptors

when light is reflected off any surface, the angle of incidence is always equal to the angle of ___

reflection

function of lacrimal glands as effector

produce tears (lubrication, protection)

function of cillary muscles as effector

adjust lens for focusing (accommodation)

function of iris muscles as effector

control pupil size (light regulation)

function of orbicularis oculi muscle as effector

close eyelids (blinking, protection)

key applications of reflection in optometry:

1. Retinoscopy Principle 2. Ophthalmoscopy (Fundoscopy) 3. Use of Mirrors and Lenses in Optical Instruments: Devices like slit lamps, keratometers, autorefractors 4. Coatings on Lenses (Anti-Reflective Coatings) 5. Corneal Topography Principle 6. Tear Film Assessment (Tear Break-Up Time)

this refers to how easily light can travel through a medium

optical density

measure the bending of a ray of light when passing from one medium into another

refractive index

abbe value is also known as

v number

changes in refraction due to cataract, which is common in nuclear cataract

myopic shift

can alter the refractive index of the lens as it becomes denser or swollen

cataract

means less dispersion and therefore less chromatic aberration

higher abbe value

lower abbe value effect in chromatic aberration

more chromatic aberration

effect in dispersion if theres higher abbe value

less dispersion

effect in dispersion if theres lower abbe value

more dispersion

change in refraction due to cataract especially with cortical or posterior sucapsular cataract

irregular astigmatism

reuslt in prescription if there's changes in refraction due to cataract

may change rapidly or become unstable

a stimulus where a particular receptor responds effectively and that gives rise to a characteristic sensation

adequate stimulus

ocular media/s which absorb uv-c and some uv-b radiation

cornea and aqueous humor

lens aborbs what uv

uv a and part of the blue light spectrum

the splitting of light into its different components

dispersion

the spreading of white light into its full spectrum of wavelengths

dispersion

ocular medias that act like dispersive medias, bending short wavelengths (blue light) more than long wavelengths (red light)

cornea and crystalline lens

ocular medias that act like dispersive medias, bending short wavelengths (blue light) more than long wavelengths (red light)

cornea and crystalline lens

when to consider the abbe valie when choosing lens materials

high prescription glasses px sensitive to visual distortions

they developed schematic eye

listing tscherning helmoltz

who developed the most authoritative model of the eye

gullstrand

parameters gullstrand needed in schematic eye

curvature of the surfaces of the cornea and lens their positions indices or refraction of the ocular media

line passing through center of cornea, lens, and meets retina

optical axis

line joining fixation point, nodal point, and fovea

visual axis

line joining fixation point and centre of rotation

fixation axis

line joing from the eye to the perceived object

line of sight

line that passes through the center of of the cornea

pupillary axis

angle formed between visual axis and optical axis at the nodal point

angle alpha

angle between optical axis and fixation axis at the center of rotation

angle gamma

angle formed between the pupillary axis and LOS

angle lambda

angle between visual axis and pupillary axis

angle kappa

factors affecting size of retinal image

- varies directly as the size of the object - inversely as the distance between the object of the eye that is it varies directly as the visual angle - dist. bet. nodal point (optic center) and the retina

it is the monocular visual field representation with simultaneously approach of the bino vision

visual pathway

refers to the anatomical structure of the eye that are responsible for perceptual interpretation

visual pathway

refers to the total area in which objects can be seen in the side as you focus uour eyes on a central point

visual field

entire area that can be seen when the eye is directed forward, including that which is seen in the peripheral visuon

visual field

"surrounded by a sea of blindness"

traquair's field of vision

a visualization of visual function

hill of vision

3D representation of the retinal light sensitivity

hill of vision

where is the highest concentration of cones located

fovea

are in what states does the contour of the island of vision changes greatly

mesopic (twilight) scotopic (dark adapted)

line connecting all points in the viual field with the same threshold (for a given spot)

isopter

boundary betaeen areas of visibility to the area of non visibility for a particular stimulus

isopter

visual field screening for peripheral visual field

confrontation test

visual screening for central visual field

amsler grid test

these are due to disease or disorders of the eye, optic nerve, and brain

visual field defecfs

these are the loss of vision/ visual field defects above or below the horizontal

altitudinal field defects

loss of vision at the sides

bitemporal heteronymous hemianopsia

loss of vision at one side of the visual field for both eyes (optic chiasma)

homonymous hemianopsia

localized defects/ depressions surrounded by normal visual field

scotoma

negative scotoma

blind spot

defect that persists when the maximum stimulus is used

absolute scotoma

defect that is present to weaker stimulus but dissaperas with brighter stimulus

relative scotoma

differential light sensitivity at which a stimulus of a given sizs and duration of presentation is seen 50%

threshold

the physiological capacity to detect a stimulus at a given location under specific condition

threshold

percentage of projected times in suprathreshold

95%

the weakest test stimulus that is just visible in particular location under the specific testing condition

threshold

percentage of low intensity stimulus

most subtle characteristic of stimulis that is visible at a specific point in space

sensitivity

what distance is the patient typically tested from the tangent screen?

1 meter

What is the field size assessed by the tangent screen?

Typically assesses 30 degrees of central vision, though testing at 2 meters can double this range to 60 degrees.

What types of defects can tangent screen detect?

Central scotomas Hemianopic defects Constricted fields Functional field loss

What ocular or neurologic conditions might show field loss on tangent screen?

Pituitary tumors (bitemporal hemianopia) Optic nerve lesions (central scotoma) Strokes (hemianopic defects) Retinal disease (localized scotomas)

What ocular condition typically produces a central scotoma on a tangent screen?

Optic neuritis or macular disease (e.g., macular degeneration) can cause a central scotoma.

What neurological lesion is associated with a bitemporal hemianopia on a tangent screen?

pituitary adenoma compressing the optic chiasm.

What are signs of functional (non-organic) visual field loss on tangent screen?

Tubular fields: Same size field at 1m and 2m (should expand with distance) Spiral fields: Field borders spiraling in an implausible way Inconsistent responses

What visual field defect is typically caused by a stroke in the occipital lobe?

Homonymous hemianopia, often respects the vertical midline.

What neurological lesion is associated with a bitemporal hemianopia on a tangent screen?

pituitary adenoma compressing the optic chiasm.

What condition might cause a quadrantanopia on a tangent screen?

A temporal or parietal lobe lesion (e.g., stroke or tumor) affecting the optic radiations.

What pattern of field loss is associated with retinitis pigmentosa?

Constricted (tunnel) visual fields, more pronounced in the periphery but may show as a central narrowing on tangent screen.

What functional (non-organic) condition might mimic severe constricted fields on tangent screen?

Hysteria, malingering, or conversion disorder — look for tubular fields (same field size at 1m and 2m), which are not anatomically possible.

Which optic nerve condition may produce an enlarged blind spot on tangent screen?

Papilledema — due to increased intracranial pressure.

What condition might cause an altitudinal visual field defect on tangent screen?

Ischemic optic neuropathy (AION or NAION).

tangent screen has a radial stitching starts at 180 meridian running through the fixation point every how many degrees

22.5 degrees

what are the targets in tangent screen

colored pigments

This pattern seen in visual field test is a non-physiologic and may indicate malingering or conversion disorder (functional vision loss)

spiral or inconsistent field boundary

This pattern seen in visual field test is a non-physiologic and may indicate malingering or conversion disorder (functional vision loss)

spiral or inconsistent field boundary

What does a constricted or tunnel vision field indicate?

May indicate advanced retinal disease (e.g., retinitis pigmentosa) or a functional disorder depending on consistency and test distance.

What does inconsistent response to the same test points suggest?

Suggests low reliability due to patient fatigue, lack of understanding, or functional visual loss.

meaurement of hill of vision

perimetry

systemic measurement of the VF function, essential for glaucoma

perimetry

extent of visual field determination of amsler grid test

10 degrees

common cause of VF defect

central visual field loss optic neuropathy macular degeneration macular hole cone dystrophies rare (best's disease, stargardts, achromatopsia)

What is the expected tangent screen finding in Best’s Vitelliform Macular Dystrophy?

A central scotoma may be seen on tangent screen in later stages due to macular degeneration, but early stages often have normal visual fields, despite abnormal EOG.

What visual field defect might be seen in Stargardt’s disease on a tangent screen?

A central scotoma, reflecting progressive macular atrophy, often bilateral.

What does a central visual field defect on tangent screen suggest in a young patient with normal retinal vessels and pigment clumping in the macula?

Suggests Stargardt’s disease – classic “beaten bronze” macula with central field loss.

Why might patients with achromatopsia have normal visual fields on tangent screen?

Because rods are preserved, peripheral vision is usually intact; central acuity loss is due to non-functioning cones but may not produce a clearly defined scotoma on basic field testing.

Which macular dystrophy is more likely to show a normal tangent screen early in the disease?

Best’s disease — the vitelliform lesion affects the macula but may not immediately impact field testing unless degeneration progresses.

Stargardt patients should avoid what vitamin supplementation which may accelerate lipofuscin accumulation

vitamin A

Stargardt patients should avoid what vitamin supplementation which may accelerate lipofuscin accumulation

vitamin A

non optical devices, part of the optometric management that can be given to patients

cane cap lamp

term refers to field loss wherein the obstructing lens rim, a droppy eyelid, or prominent brow obstruct field.

artificial field loss

is a psychophysical percept wherein lateral motion of an object in the field of view is interpred by the visual cortex as having a depth componennt due to a relative difference in signal timings between the two eye

pulfrich phenomenon

pulfrich phenomenon is named for this german physicist

carl pulfrich

the pulfrich effect is generally induced by placing a what filter over one eye

dark filter

pulfrich effect can be also occur spontaneously in several eye disease such as

cataract optic neuritis multiple sclerosis

it provides objective measurements of fuctional VA in three common bright light conditions while the px is in a standard refracting lane

brightness visual acuity test

brightness visuity tested can stimulate three bright light conditions

high direct overhead sunlight medium partyly cloudy day low bright overhead commercial lighting

brightness setting that is equivalent to the patient being in direct overhead sunlight (10,000 fc) and standing on a white concrete sidewalk or sandy beaach

high (400 foot lamberts)

brightness setting Equivalent to the patient being in indirect sunlight (2,500 foot-candles) and standing on a white concrete sidewalk or sandy beach on a cloudy day.

medium (200 foot lamberts)

brightness setting Equivalent to the patient being in bright overhead fluorescent lighting (300 foot-candles) such as in a department store, piant assembly line or classroom.

low (12 foot lamberts)

average bowl luminance for setting is what brightness setting

low

Marginal prolonged recovery time in macular photostress test

30-60 seconds

recovery time results in macular photostress test if maculopathy is possible but not definite

>60 seconds

A lesion affecting the right retina or optic nerve will cause what visual field defect?

A right eye total visual field defect (monocular blindness).

What is the visual field defect from a lesion in the left retina or left optic nerve?

A left eye total visual field defect. → Pre-chiasmal lesions affect the same eye.

A lesion affecting the right retina or optic nerve will cause what visual field defect?

A right eye total visual field defect (monocular blindness).

What visual field defect results from a lesion affecting the crossing fibers at the optic chiasm?

Bitemporal hemianopsia — loss of the temporal fields in both eyes.

What visual field defect occurs from a lesion affecting the uncrossed (lateral) fibers of the optic chiasm?

Binasal hemianopsia — loss of the nasal fields in both eyes.

A right optic tract lesion causes what type of visual field defect?

Left homonymous hemianopsia. → Post-chiasmal lesion = contralateral, same-side field loss in both eyes.

A right optic tract lesion causes what type of visual field defect?

Left homonymous hemianopsia. → Post-chiasmal lesion = contralateral, same-side field loss in both eyes.

What visual field defect results from a left optic tract lesion?

Right homonymous hemianopsia. → Commonly due to stroke, tumor, or trauma.

What does a right occipital lobe (Area 17) lesion typically cause?

Left homonymous hemianopsia with macular sparing. → Due to dual blood supply to macula (PCA and MCA).

A lesion in the left occipital lobe (Area 17) produces what defect?

Right homonymous hemianopsia with macular sparing. → Macular sparing helps differentiate occipital from optic tract lesion.

What does a right occipital lobe (Area 17) lesion typically cause?

Left homonymous hemianopsia with macular sparing. → Due to dual blood supply to macula (PCA and MCA).

Lesions of the retina or optic nerve result in visual field loss on which side?

On the same side (ipsilateral) as the lesion. → This is pre-chiasmal vision loss.

A lesion at the crossed fibers of the optic chiasm causes a visual field pattern that resembles which eye deviation?

An exotropic-like (divergent) field defect → bitemporal hemianopsia. → Loss of temporal fields mimics eyes turned outward.

A lesion at the uncrossed fibers of the optic chiasm results in a field defect resembling what deviation?

An esotropic-like (convergent) field defect → binasal hemianopsia. → Loss of nasal fields mimics eyes turned inward.

Lesions from the optic tract to Area 17 (occipital lobe) cause visual field loss on which side?

On the opposite (contralateral) side → homonymous hemianopsia. → All post-chiasmal lesions behave this way.

What field defect results from a lesion in the left retina or left optic nerve?

Total loss of vision in the left eye (left monocular blindness)

Lesions from the optic tract to Area 17 (occipital lobe) cause visual field loss on which side?

On the opposite (contralateral) side → homonymous hemianopsia. → All post-chiasmal lesions behave this way.

What is the defect and lesion site if both crossed fibers of the optic chiasm are affected?

Bitemporal hemianopsia (loss of temporal fields in both eyes)

What happens with a lesion in the right optic tract?

Left homonymous hemianopsia (left field in both eyes lost)

What field defect results from a lesion in the right occipital lobe (Area 17, primary visual cortex)?

Left homonymous hemianopsia with macular sparing

What is the field defect from a lesion in the left occipital lobe (Area 17)?

Right homonymous hemianopsia with macular sparing

What does a lesion of the optic chiasm crossing fibers resemble in field pattern?

Bitemporal hemianopsia, resembling exotropia (divergent fields)

What happens with a lesion in the right optic tract?

Left homonymous hemianopsia (left field in both eyes lost)

What does a midline optic chiasm lesion cause?

Bitemporal hemianopsia Classic for pituitary adenoma

Which lesion causes incongruous homonymous hemianopsia?

Lesions closer to the optic tract or LGN

What does a midline optic chiasm lesion cause?

Bitemporal hemianopsia Classic for pituitary adenoma

Which lesion causes congruous homonymous hemianopsia?

Lesions closer to the occipital cortex (e.g., visual cortex or posterior optic radiations)

What is the visual field defect caused by a lesion at the right optic nerve head?

Right eye total vision loss or altitudinal defect

Lesion Site: Central optic chiasm

Defect: Bitemporal hemianopsia

Lesion Site: Left LGN (thalamus)

Defect: Right homonymous hemianopsia, incongruous

What is the visual field defect caused by a lesion at the right optic nerve head?

Right eye total vision loss or altitudinal defect

What happens with a lesion of the right Meyer’s loop (temporal lobe)?

Defect: Left superior quadrantanopia ("pie in the sky")

Lesion Site: Right anterior inferior optic radiations

Left superior quadrantanopia ("pie in the sky")

What happens with a lesion of the right Meyer’s loop (temporal lobe)?

Defect: Left superior quadrantanopia ("pie in the sky")

What is the result of a lesion in the left parietal lobe (superior optic radiations)?

Right inferior quadrantanopia

What is the result of a lesion in the left parietal lobe (superior optic radiations)?

Right inferior quadrantanopia

What is the result of a lesion in the left parietal lobe (superior optic radiations)?

Right inferior quadrantanopia ("pie on the floor")

What is the first step in the visual process and what structure initiates it?

light entry (physical process)

What is the first step in the visual process and what structure initiates it?

light entry (physical process)

Which structures work together to refract light before it hits the retina?

Cornea, aqueous humor, lens, and vitreous humor

What is the process where light is converted into electrical signals in the eye?

Phototransduction — occurs in the rods and cones of the retina

Which photoreceptor is responsible for low-light (scotopic) vision?

rods

What photopigment in rods is essential for phototransduction?

rhodopsin

Which photoreceptor is responsible for low-light (scotopic) vision?

rods

What photopigment in rods is essential for phototransduction?

rhodopsin

After photoreceptors activate, which retinal cells process and transmit the signal next?

Bipolar cells, then ganglion cells, with help from horizontal and amacrine cells

What structure is formed by the axons of the ganglion cells?

optic nerve

Where does the optic nerve partially cross to sort visual information?

optic chiasma

Where are visual signals relayed after the optic chiasm?

To the lateral geniculate nucleus (LGN) of the thalamus

Where does the optic nerve partially cross to sort visual information?

optic chiasma

From the LGN, visual signals are sent to which brain area for interpretation?

The primary visual cortex (Area 17) in the occipital lobe

Where are visual signals relayed after the optic chiasm?

To the lateral geniculate nucleus (LGN) of the thalamus

What is the final step of the visual process, where perception occurs?

Visual perception in the occipital cortex, where signals are interpreted into meaningful images

What part of the cortex is primarily responsible for processing raw visual data?

The primary visual cortex (V1), located in the occipital lobe

process of seeing refers to the generation of nerve impulses in the retina and its transmission by the chain of neuron to the CNS

neuromuscular/neuroelectrical process

refers to the stimulus alerting events wherein in a physical stimulus, is converted into action potential which is transmitted along axons towards CNS for integration

sensory transduction

process of seeing that refers to the intergration of electrical impulse that passes through neural nerves on the visual pathway to the brain (area 17/ area striata) to be process and interpreted

psychological or interpretative process

layer/ coat of the eye comprises sclera and cornea

fibrous coat

coat that protects the internal part of the eye especially. nervous

fibrous coat

What is the outermost layer of the sclera and is it vascular or avascular?

The episclera — it is the vascular outermost layer of the sclera.

What layer of the sclera is composed of dense, irregularly arranged collagen fibers?

The scleral stroma (also called scleral proper).

What is the innermost layer of the sclera

The lamina fusca

what cells does laminate fusca contains

it contains melanocytes and lies adjacent to the choroid.

How much of the outer coat of the eyeball is occupied by the sclera?

The sclera occupies 5/6 of the outer tunic of the eyeball.

How much of the outer coat of the eyeball is occupied by the sclera?

The sclera occupies 5/6 of the outer tunic of the eyeball.

What fibrous capsule covers the sclera externally?

Tenon’s capsule (also called the fascia bulbi).

Tenon’s capsule is also called the

fascia bulbi

What conjunctiva covers the exposed part of the sclera?

The bulbar conjunctiva.

Tenon’s capsule is also called the

fascia bulbi

What is the normal fluid content of the sclera

65–70%

If it fluid content of sclera drops below 40%, from 65–70%, the sclera may appear ___ due to underlying uveal pigmentation showing through

bluish

What are the two main foramina (openings) in the sclera?

Anterior scleral foramen Posterior scleral foramen

What cranial nerve passes through the posterior scleral foramen?

Cranial nerve II (optic nerve).

What structure within the posterior sclera acts as a sieve for optic nerve fibers?

The lamina cribrosa

Where is the anterior scleral foramen located?

It is located at the limbal area of the eye.

What structure pierces the anterior scleral foramen?

It is pierced by the 7 anterior ciliary arteries (ACA).

Where is the posterior scleral foramen located?

It is located at the optic nerve head (posterior pole of the eye).

Approximately how many nerve fibers make up the optic nerve at the posterior scleral foramen?

Approximately 800,000 to 1.3 million nerve fibers.

Where is the posterior scleral foramen located?

It is located at the optic nerve head (posterior pole of the eye).

What major blood vessels pass through the posterior scleral foramen?

The central retinal artery (CRA) and the central retinal vein (CRV).

Which arteries other than CRA pierce the posterior scleral foramen?

The long and short posterior ciliary arteries (LPCA & SPCA).

Which nerves pierce the posterior scleral foramen aside from the optic nerve?

The long and short posterior ciliary nerves (LPCN & SPCN).

Where are all rectus muscles inserted relative to the equator of the eyeball?

Anterior to the equator.

Where are oblique muscles inserted relative to the equator of the eyeball?

Posterior to the equator.

At which part of the sclera is it thickest, and what is the thickness?

At the entrance of the optic nerve (CN II) — about 1 mm thick.

Where is the thinnest part of the sclera, and what is its thickness?

At the insertion of the rectus muscles — about 0.3 mm.

What is the radius of curvature of the sclera?

Approximately 12 mm.

What are the blood supply sources of the sclera?

Anterior ciliary arteries (ACA) Long posterior ciliary arteries (LPCA) Short posterior ciliary arteries (SPCA)

What nerves innervate the sclera?

Long posterior ciliary nerves (LPCN) Short posterior ciliary nerves (SPCN)

What is the main refractive medium of the eye and its total refractive power?

cornea, with a refractive power of 43D to 46D.

refractive power of cornea

43D to 46D.

How much of the outer coat of the eye is occupied by the cornea?

The remaining 1/6 (the sclera occupies the other 5/6).

What is the radius of curvature of the cornea?

7 to 8.5 mm

What are the horizontal and vertical diameters of the cornea?

Horizontal: 11–12 mm Vertical: 10–11 mm

What is the central thickness of the cornea?

Approximately 0.52–0.56 mm

What is the radius of curvature of the cornea?

7 to 8.5 mm

What is the peripheral thickness of the cornea?

Ranges from 0.7 to 1.0 mm

What is the index of refraction of the cornea?

1.376

What is the total refractive power of the cornea?

43D

What are the three main sources of nourishment for the cornea?

Aqueous humor (AH) – nourishes the endothelium (posterior layer) Limbal capillaries – at the corneal periphery Pre-corneal tear film – nourishes the anterior epithelium

What is the outermost layer of the cornea and what percent of the corneal thickness does it comprise?

The anterior corneal epithelium — about 10% of the total corneal thickness.

Is the cornea vascular or avascular?

The cornea is avascular, except at the limbal area.

What supplies the limbal area of the cornea?

The conjunctival arteries, branches of the anterior ciliary arteries (ACA).

Which layer of the cornea is nourished by the aqueous humor?

The endothelium (posterior layer).

Which part of the cornea is nourished by the pre-corneal tear film?

The anterior corneal epithelium.

What percentage of the cornea does the epithelium comprise?

About 10% of the total corneal thickness.

How often does the corneal epithelium regenerate?

Every 7 days.

Why is the corneal epithelium highly sensitive to pain?

Because it is filled with thousands of nerve endings.

What supplies the limbal area of the cornea?

The conjunctival arteries, branches of the anterior ciliary arteries (ACA).

How often does the corneal epithelium regenerate?

Every 7 days.

What is the second layer of the cornea beneath the epithelium?

Bowman’s membrane

To act as a basement membrane that binds the epithelium to the stroma.

bowman's

Can Bowman’s membrane regenerate after injury?

No, it is non-regenerative.

To act as a basement membrane that binds the epithelium to the stroma.

bowman's

What is the second layer of the cornea beneath the epithelium?

Bowman’s membrane

Which layer of the cornea accounts for approximately 90% of its total thickness?

corneal stroma

What are the two major components of the corneal stroma?

Water (78%) and collagen (16%).

Is the corneal stroma capable of regeneration?

Yes, it can regenerate

What is the fourth layer of the cornea, located beneath the stroma?

Descemet’s membrane

What is the fourth layer of the cornea, located beneath the stroma?

Descemet’s membrane

What does Descemet’s membrane consist of

consists of collagen

what does decements membrane separate?

separates the stroma from the endothelium.

corneal layer which acts as a protective barrier against infection and injury.

decement's membrane

Can Descemet’s membrane regenerate after injury

yes

What is the innermost layer of the cornea?

corneal endothelium

what does decements membrane separate?

separates the stroma from the endothelium.

What term describes the state of the cornea when it remains partially dehydrated for transparency?

Deturgescence

What happens to endothelial cells after injury if they cannot divide?

They undergo polymegathism (change in size) and pleomorphism (change in shape) to cover the defect.

What happens if the corneal endothelium fails to pump fluid out of the stroma?

The stroma swells, becomes hazy, and ultimately opaque, leading to vision loss.

What happens to endothelial cells after injury if they cannot divide?

They undergo polymegathism (change in size) and pleomorphism (change in shape) to cover the defect.

What is another name for the vascular layer (middle coat) of the eyeball?

Uvea or tunica vasculosa (also called tunica media)

Why is the uveal coat considered the most dangerous layer of the eye?

Because it is highly vascular, making it more prone to inflammation and infection.

What is another name for the vascular layer (middle coat) of the eyeball?

Uvea or tunica vasculosa (also called tunica media)

What are the two anatomical subdivisions of the uvea?

Anterior uvea Posterior uvea

What is the anterior portion of the uveal tract called?

The anterior uvea

What two structures make up the anterior uvea?

The iris and the ciliary body.

where does iris located

located between the cornea and the lens at the most anterior part of the uveal tract.

What two structures make up the anterior uvea?

The iris and the ciliary body.

is a delicate diaphragm

iris

What is the central opening in the iris called?

pupil

What are the three physiological functions of the iris?

Reduces spherical and chromatic aberration Regulates the amount of light entering the eye Increases the depth of focus

is a thickened extension of the choroid that begins at the ora serrata.

cillary body

where does cillary body begins

begins at the ora serrata.

What is the junction between the choroid and the ciliary body called?

The ora serrata.

What are the 70 folds on the inner surface of the ciliary body called?

Ciliary fibers (or processes).

What suspends the lens by attaching to the ciliary processes?

The suspensory ligaments, also known as the zonules of Zinn.

What is the posterior portion of the uveal tract called?

posterior uvea.

What structure makes up the posterior uvea?

choroid

How much of the eye’s internal surface does the choroid cover?

It covers about 5/6 of the interior of the eye.

What is the main composition of the choroid?

It is made up mostly of blood vessels.

Why is the choroid dark brown in color?

Due to the presence of melanocytes (pigmented cells).

What is the main composition of the choroid?

It is made up mostly of blood vessels.

function is to nourish the outer retina and coats of the eye.

choroid

What is the first histologic layer of the choroid?

The lamina fusca (also called lamina suprachoroidea).

the lamina fusca is also called as the

lamina suprachoroidea

What is the lamina fusca composed of?

Collagenous and elastic fibers.

the lamina fusca is also called as the

lamina suprachoroidea

What is the second histological layer of the choroid called?

The blood vessel layer.

A part of the blood vessel layer containing large-sized anastomosing veins.

Haller’s layer

part of the blood vessel layer containing medium-sized anastomosing veins.

Sattler’s layer

It is a capillary-rich layer containing wide-bore, fenestrated capillaries that nourish the outer retina.

choriocapillaris (membrane of Ruysch)

part of the blood vessel layer containing medium-sized anastomosing veins.

Sattler’s layer

What is the third layer of the choroid?

The lamina vitrea, also called Bruch's membrane or lamina basalis choroidea.

The lamina vitrea, also called

bruch's membrane

It is a thin, structureless layer that serves as the base to which the retinal pigment epithelium (RPE) is firmly adherent.

lamina vitrea, bruch's membrane

What is another name for the retina?

Nervous coat, retinal coat, or tunica intima.

From where is the retina embryologically derived?

From the optic cup or optic vesicle.

What are the anterior and posterior boundaries of the retina?

It extends anteriorly to the ora serrata and posteriorly to the optic disc.

What are the anterior and posterior boundaries of the retina?

It extends anteriorly to the ora serrata and posteriorly to the optic disc.

What is the thickness range of the retina?

From 0.1 mm to 0.5 mm.

What are the two regions of the retina?

Central retina (macula lutea or yellow spot) Peripheral retina

What are the two divisions of the retina?

Pars optica retina Pars caeca (ciliary retina)

division of retina which contains photoreceptors and serves as the sensory end-organ for vision.

pars optica retina

division of retina which transitions into epithelial coverings of the ciliary body and iris, and it is insensitive to light and nerve impulses (no photoreceptors).

pars caeca or ciliary retina

division of retina which contains photoreceptors and serves as the sensory end-organ for vision.

pars optica retina

division of retina which is insensitive to light and nerve impulses (no photoreceptors).

pars caeca or cillary retina

What type of photoreceptor is responsible for day/bright vision (photopic vision)?

cones

They transmit visual and pupillary impulses.

nerve fibers

What supplies the outer retina, RPE, and photoreceptors?

choriocapillaris (membrane of Ruysch)

What percentage of total retinal blood flow is provided by the choriocapillaris?

Approximately 65%–85%.

division of retina which is insensitive to light and nerve impulses (no photoreceptors).

pars caeca or cillary retina

What supplies the outer retina, RPE, and photoreceptors?

choriocapillaris (membrane of Ruysch)

What supplies the inner sensory retina?

The central retinal artery (CRA).

What percentage of total retinal blood flow is provided by the central retinal artery?

Approximately 20%.

retinal layer which choriocapillary supplies

rpe and photoreceptor cell

In which direction is a light ray bent when it enters a prism?

Toward the base of the prism.

In which direction is an object displaced when viewed through a prism?

Toward the apex of the prism.

In which direction does the eye turn when looking through a prism

Toward the apex of the prism.

What is the rule for neutralizing an ocular deviation using prisms?

Place the apex of the prism in the same direction as the deviation.

In which direction is a light ray bent when it enters a prism?

Toward the base of the prism.

How do you use a prism to neutralize a SOT (eso deviation)?

Use a Base Out (BO) prism. → Because in SOT, the image falls nasal to the fovea. BO prism shifts the image temporarily onto the fovea.

IR which has greater refractive power

higher index

IR which has lesser refractive power

lower index

The distance from the center of curvature to the surface of a lens or cornea.

radius of curvature

What does a shorter (steeper) radius of curvature indicate about a surface's shape?

The surface is more curved, creating a stronger lens.

Which condition is often associated with very short axial lengths?

nanophthalmos

Which condition is associated with very long axial lengths?

Pathologic myopia → may lead to posterior staphyloma, retinal detachment, and chorioretinal atrophy.

What happens to the focal point in an eye with an axial length < 23 mm?

Light focuses behind the retina, resulting in axial hyperopia.

What happens to the focal point in an eye with an axial length > 24 mm?

Light focuses in front of the retina, resulting in axial myopia.

Which condition is associated with very long axial lengths?

Pathologic myopia → may lead to posterior staphyloma, retinal detachment, and chorioretinal atrophy.

What happens to the focal point in an eye with an axial length < 23 mm?

Light focuses behind the retina, resulting in axial hyperopia.

What type of refractive error can result from a steep cornea?

Myopia, due to greater refractive power.

What type of refractive error can result from a flatter cornea?

Hyperopia, due to less refractive power.

What does a longer (flatter) radius of curvature indicate about a surface’s shape?

The surface is flatter, producing less refractive power.

How does the position of the crystalline lens affect the eye’s effective refractive power?

A more anteriorly placed lens increases refractive power, while a posteriorly displaced lens reduces it

What happens to refractive power when the lens is positioned closer to the cornea (more anteriorly)?

effective power increases, potentially causing a myopic shift.

What happens to refractive power when the lens is displaced posteriorly (e.g., after trauma)?

The effective power decreases, resulting in a hyperopic shift.

posterior shift in lens movement may cause what ref error after intraocular surgery or trauma

induced hyperopia

What type of refractive error can result from a flatter cornea?

Hyperopia, due to less refractive power.

anterior shift in lens movement may cause what ref error after intraocular surgery or trauma

induced myopia

Physiological Optics Flashcards

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