Vision

Rods vs. Cones

i) Shape: rod-shaped vs. cone-shaped ii) Population: more rods than cones iii) Location: rods are in the periphery while cones are more centrally located (fovea has highest density) iv) Function: >Rods are made for scotopic (nighttime) vision while cones are for Photopic (daytime, colour) vision v) Function: >Cones distinguish elements of color and sharpen an image - high resolution images but less sensitive to light >Rods are more sensitive to light so can see in dark, but has poor resolution rods = sensitive to low light conditions cones = high visual acuity in daylight + colour sensitivity

Eye dominance

i. Eye that provides slightly more visual input into cortex of our brain ii. Everyone has a dominant eye in healthy eyes, you don't normally notice this, but it becomes more noticeable if there is a visual IMPAIRMENT in dominant eye iii. If someone has impairment in dominant eye, person may still depend on that eye, even if it is still impaired out of habit - so goal is to train patient to use non-dominant eye and SHIFT dominance to another eye - Testing eye dominance: o Look at the image and put fingers in a triangle, place image in the middle o Close right eye and then left eye o When closing one eye and image moves and SHIFT, then the eye that most shift happens = dominant eye o So if you close left eye, and right eye is still open + image doesn't shift --> then your right is dominant; closing right eye will lead to a shift o Other way to do this: tell client to look at a picture of a house through a card - will spontaneously hold that card through one eye or another - once they hold it up, it's probably going to be the one that is dominant

Contrast sensitivity test

i. LeaNumber Low Contrast Screener -Done at distances at 40cm, 1 metre, 3 metres- -Series of word on card - instead of words getting smaller and smaller (like reading acuity test), text gets lighter and lighter - based on how far down you can go, get idea of what visual contrast sensitivity level is like -Graph information you find to get objective number of what contrast sensitivity is

Visual field testing in biVABA

i. Measured by ophthalmologist - use perimeter tool ii. Visual field cut for functional reasons, can use another test - start at a point in front of you - point you focus on is POINT ZERO; shut one eye Measured in degrees: 1. Take finger and bring it to the side from temporal side and as soon as you see it, STOP - 100 degrees temporal 2. Take finger and bring it from medial side and stop when you see it - usually 60 degrees nasal because nose gets in the way (nasal visual field) 3. From top: usually 60 degrees superior 4. From bottom: 75 degrees inferior 5. Fovea: central 8 degrees (only cones) 6. Macula: central 20-35 degrees (includes fovea) 7. Peripheral field (primarily rods)

Presbyopia

impairment of vision as a result of old age -With age, lens becomes less flexible so it cannot refract light as well, leading to hyperopia

Measuring Visual Functional Performance

- Ask client to perform a functional task and use observational skills - Includes a detailed list of clinical observations - Visual acuity, contrast sensitivity function: - Visual acuity function examples: o Ask patient to read anything with standardized sized print - like book or newspaper o Use observational skills and note their behaviour --> do they move it closer or farther away, do they tilt their head, do they turn their head sideways, do they try to use more of peripheral vision (e.g. macular degeneration) - General observations examples: o Do they state that they can't recognize faces? See better in corner of eye? Do they state that vision fluctuates throughout the day? - Contrast sensitivity function example: o Ask client to fill a clear glass with water from tap or pitcher within ½ inch of brim § Observe: over filling glass, moves in really close to see glass

FUNCTIONAL IMPLICATIONS OF VISION IMPAIRMENTS

- Decrease gait, balance, and safe mobility o Example: VOR reflex important for balance - Decreased independence in self-care and daily activities - Reading/writing - Computer/phone use - Decreased visual endurance - fatigue/headaches/nausea o Influences independence - Social participation o Identifying non-verbal communication/social cues - cannot recognize faces, cannot see what is going on around them - Driving - Vocational roles e.g. glare --> hard to drive and see at night contrast sensitivity --> hard to navigate stairs that are one colour

Both eyes (-versions) moving in same direction

- Dextroversion - both eyes looking to the right - Levoversion - both eyes looking at left - Supraversion - both eye looking up - Infraversion - both eyes looking down

Considerations for biVABA

- Little emphasis on scoring or use of "cut-off scores" o Can't determine if they score at a certain level, that they have a visual deficit or not - alerts you that something is OFF - this is where knowledge of anatomy and pathology comes into play - is this a problem or not? - Focuses on individual's visual function as they impact ADLs - qualitative test more than a quantitative one - Requires more testing/studies on psychometric properties - One of the more comprehensive OT visual screening tools at this time

Aqueous humour

-A watery fluid which helps to maintain the shape of the eyeball and provides nutrients and oxygen to the lens and cornea, as well as carrying away waste products -Produced by ciliary body in the posterior chamber and flows in and out of anterior chamber

Macula lutea

-A yellowish, pigmented central area of the retina that is rich in cones and that mediates clear detailed vision - contains the fovea -For central vision

Visual acuity

-Ability to see clearly and resolve a visual object -Good initial screening test for all aspects of vision - needs good surface of cornea, lens, good eye globe shape, clear cornea and lens, clear ocular media, intact retina, optic nerve, and visual pathways (intact structures of eye and pathways of eye/neurosensory parts) -Usually tests far distance visual acuity

Strabismus

-Abnormal alignment of eyes -Often caused by defects in muscle function -Tropias an phorias - nonproper alignment of two eyes, leading to blurred/double vision because there is no bifoveal fixation

Medial and lateral rectus movements

-Adduction and abduction of eye

Vestibular ocular reflex - purpose, level of control

-Allowing visual focus (bifoveal fixation) to remain on objects even when the head is moving or turning rapidly - Spares supranuclear control from cortex which makes it faster, and no input from cortex = can allow for testing of just the infranuclear and nuclear inputs - distinguish where source of problem is - Saccades, gaze have supranuclear input - input from the CORTEX - allows for complex movements like smooth pursuits, saccades in different directions but we also need things that do not involve higher inputs if we want to do things quickly (VOR is very fast)

How to test extraocular movements

-Ask patient to follow finger and test all 6 cardinal positions of gaze -Smooth pursuit: patient tracks your finger across room

Refraction eye

-Bending of light as it passes from one medium (air) into a 2nd medium with a different density (cornea) -Cornea and lens are important for this -Cornea doesn't change shape or anything, but it's important for refracting the light and the lens will fine tune the image based on other factors - dynamic changes -Axial length of globe is important for refraction

Anterior chamber of eye

-Between the cornea and iris -Contains aqueous humour

Posterior chamber of eye

-Between the iris and the lens -Aqueous humour -Very small -Lens = posterior-most border of posterior chamber and is attached to muscles (zonule fibers + ciliary muscles) where it can change shape

Vitreous chamber of eye

-Between the lens and the retina -Contains vitreous humour

Optic nerve

-CNII -Carries impulses from the retina to the primary visual cortex in occipital lobe -Makes up the blind spot (no rods or cones) -Diseases may occur in optic nerve - glaucoma, optic neuritis

Eye opening muscles

-CNIII: Levator Palpebrae superioris -CNVII: Frontalis Muscle -Muller's muscle - Sympathetic

Closed angle glaucoma

-Caused by an anatomically narrow angle between the iris and the cornea, which prevents outflow of aqueous humour into the trabecular meshwork and canal of schlemm out of eye -Fluid cannot circulate so pressure will build up and lead to neurological damage of the optic nerve -Medial emergency -May be caused by going from a dark room to light room - ciliary muscles will contract and move the lens and pushes the lens and iris forward --> leading to narrowed angle between iris + cornea -Can lead to vomiting and headache, often pain is involved -Tunnel vision (only central vision)

Snellen Chart

-Chart containing symbols that is used in the testing of visual acuity -Usually at 20 ft. 14 inches away -Ask client to stand at fixed standardized distance and do one eye at a time or both eyes, and also do with glasses on -Scored as a fraction 20/20 = perfect 20/40 = able to read that row at 20 ft, in which normal people would be able to read that row clearly at 40 ft >First number = testing distance >Second number = based on smallest row of letters read

Blood supply to eye

-Comes from the ophthalmic artery that branches off from the internal carotid artery -Ophthalmic artery eventually branches off into the choroid, which is the vascular layer of the eye and supplies the eye globe

Age-related macular degeneration (AMD)

-Condition in which the macula degenerates, gradually causing central vision loss -Leading cause of irreversible blindness in developed world - retinopathy -Exudative deposits beneath the retinal epithelial membrane - happens in the macula -Cause is very complicated but pathology occurs ONLY in the macula

Tropias

-Constant diplopia, often close one eye; synonym for strabismus Esotropia- inward deviation of eye Exotropia- outward deviation of eye Hypertropia- upward deviation of eye Hypotropia- downward deviation of eye orthotropic - straight -Test with the uncover/cover test -Often genetic or trauma

Conjugate gaze

-Coordinated movement of the two eyes simultaneously in the same direction -Synergistic movements - both eyes move to look at the target point to project it onto the fovea - bifoveal fixation on same object is the goal -Eyes work in unison and in parallel -Connected to both visual + motor systems, and coordinated by higher centers in the cortex + brainstem (Gaze centers) to communicate with motor neurons of CNIII, IV,and VI to control extraocular muscles

Cover-uncover test

-Cover one eye; Watch the uncovered eye for a steady, fixed gaze - should not move (NORMAL) -ESOTROPIA in left eye (deviated inwards): if you cover the right eye, the left eye (esotropic) will move outwards from midline to pick up fixation (go to midline). If left eye (esotropic eye) is covered, the already fixated right eye will not move b/c it is normal

Internuclear Ophthalmoplegia

-Damage to the MLF -Leads to disruptions in neural circuitry between CNVI and CNIII -Prevents the neurons from abducens nuclei from projecting to the contralateral oculomotor nuclei in the midbrain -Side that is damaged is the eye that cannot go medial Left internuclear ophthalmoplegia: damage to the LEFT MLF = right abducens nuclei cannot communicate with the left oculomotor, so the left eye cannot activate medial rectus and look medially (can't look right)

Dorsal midbrain syndrome

-Damages vertical gaze center or one of the nuclei -Usually upgaze is affected because it involves only one nuclei (CNIII - SR and IO) whereas downgaze involves CNIII and CNIV, so damage to one nuclei can be compensated by other one -Progressive supranuclear palsy: upgaze affected before downgaze

Anopia

-Defect of vision in one eye -Optic nerve damage of one eye will lead to monocular vision loss - cannot see anything from that eye, both visual fields effected -Stereovision is gone

Conjunctiva

-Delicate membrane lining the eyelids and covering the eyeball -Semi-transparent, on top of sclera *does not go over top of the cornea -Bulbar conjunctiva: over sclera -Palpebral conjunctiva: on the eyelid

What to test in pupil exam

-Direct response -Consensual response -Relative afferent pupillary defect -Accommodation -Symmetry

Testing VOR

-Dolls eye maneuver -Passively move the patients head and see if eyes do opposite movement -Can help you isolate if there is an issue with cortex (supranuclear control) or a cranial nerve problem (abducens nuclei, MLF, CNIII, CNVI) -If VOR is intact, we know the CN nuclei and PPRF involved are working fine and visual deficits likely due to supranuclear controls (e.g. FEF, primary visual cortex) -Often used to pronounce brain death --> no VOR = brain stem damage

Visual association areas

-Dorsal stream and ventral stream

Diplopia

-Double vision - perception of two images of a single object -May be caused by CN palsies - extraocular muscles not working properly so eyes cannot work together and 2 different images are projected onto the retina in different spots

Types of Visual Impairments

-Double vision or blurred vision -GLares/halos/starburst vision -Low contrast vision/contrast sensitivity -Loss of central vision -Loss of peripheral vision -partial or full visual field loss

Smooth pursuit control

-Driven by visual stimuli; Voluntary eye movement in which the eyes move smoothly to follow a moving object -Slower, conjugate eye movements -More levels of control than a saccade -Has input from cerebellum (movement), vestibular nuclei (location/position in space) -Stabilizes and holds image on the retina during movement of object itself or the person -Involves integration of cortical information: primary visual/association cortex to see the object, FEF to move the eyes, cerebellar information to say how you are moving, and vestibular information to sense where you are in the environment, and interconnection of CNVI of one side to CNIII of other side via MLF -Both sides of cortex activated @ same time

Inferior oblique

-EXTORTION -Elevates eye and turns it laterally -Other actions: elevation and abduction

POTENTIAL OT intervention: for visual impairments

-Education is HUGE - teach patients all about pathology and impairments they have, and teach them to be the therapist and live their life with that condition - Make referrals based on findings from biVABA - Skills training to optimize use of residual vision >Changing dominance of eye, environmental scanning - Skill training to optimize use of residual sensory skill >Tactile, auditory, taste/smell >Using braille >Using auditory cues to get information - Visual endurance training >Energy conservation strategies - take a break BEFORE getting tired - Prescribed and practice use of visual aids > Magnifying tools > Prism glasses > Colour filters > Illuminating devices - Modifications for computer use > Colour filters over computer screens to minimize glare > Change font > Prism glasses (double vision) > Colour contrast screen modifications - Environmental assessments - maximize independence by using strategies - Modification to self-care and ADLs - Social assessment and training >Non-verbal communication, how to identify social cues - Driver assessment training - Vocational assessment and training -Support groups

Superior and inferior rectus movements

-Elevation and depression of eye

CNIII palsy

-Eye goes down and out -Pupil is dilated because CNIII normally constricts pupils -Eye cannot look up (SR and IO not working) and cannot look medially (MR not working and LR is unopposed) -Exotropia: outward deviation from midline - LR is unopposed by MR -Hypotropia: SO is unopposed, so brings the eye down

Volitional saccade wiring

-Eye jumps from one fixation point to the next and stops briefly at each point to allow for detailed examination by that fovea Frontal eye field: cortical area involved in saccadic eye movements: picks up item on the contralateral visual field (e.g. right frontal eye field picks up object on the left side) and sends inputs to contralateral PPRF ITEM ON LEFT: -Frontal eye field (right) --> Left PPRF --> left Abducens nuclei --> left lateral rectus muscle looks to left Left PPRF --> Left abducens nuclei --> MLF --> right oculomotor nuclei --> right medial rectus looks to the left

Eye globe

-Eye separate from its appendages

Accommodation - near image

-Eyes converge via vergence center activating CNIII - medial rectus -Pupils constrict to increase depth of field -Lens curvature increases --> ciliary muscles contract, zonule fibers relax, lens AP diameter increases to increase refraction

Accommodation - far image

-Eyes diverge via vergence center sending signals to the CNVI nuclei -Pupils dilate -Ciliary muscles relax (normal tension), leading to constriction and tension of zonule fibers on lens, flattening the lens to reduce AP diameter of lens

Disconjugate gaze

-Failure of the eyes to turn together in the same direction (e.g. both look to left)

Zonule fibers

-Fibers that connect the lens to the choroid; they pull on the lens to change its shape -Run from ciliary muscles and make up the suspensory ligaments of the lens -Relaxation of ciliary muscles = tension of zonule fibers --> lens flattens out to see a far point -Ciliary muscles contracting = zonule fibers RELAX and the lens ROUNDS

Intraocular pressure - how is it measured

-Fluid pressure in the eye -Eye globe is a closed compartment, so you can measure fluid that comes in and out, and the force over area -Aqueous humour flows from the ciliary body to the lens and cornea which exerts pressure -Normal: 10-21 mmHg -Tonometry: observes force over fixed area. Uses a technique to flatten the cornea (non-contact = puff of air, tonopen = pen to poke cornea, applanation tonometry = specialized microscope equipment to flatten cornea)

Cross-cover test

-For when pt. passes cover-uncover test (no tropia) but still complain of diplopia - may have a PHORIA in which it is not manifest all the time -Breaks fusion of eyes - does not allow eyes to work together/communicate -Example: If you go back and forth between the eye, breaking fusion/communication between the eyes, and both eyes move in, then normally they are both exophoric.

Why is peripheral vision lost first in glaucoma?

-Gnaglion cell axons travel along surface of retina and then exit eye at optic disc (medial to fovea), and exit the eye -Cells farther away from the optic nerve (periphery) travel over top of those closer to the nerve -More superficial axons (those in periphery) get damaged FIRST -Central vision damaged last because axons closer to the optic nerve/center are deeper

Horizontal and vertical gaze centers

-Horizontal: Paramedian Pontine Reticular formation (PPRF) in the pons -Vertical: Rostral Midbrain Reticular Formation (rMRF) in the midbrain -Act TOGETHER to allow two eyes to see images in the same visual field, and for a smooth projection of these images onto the retina - any discrepancy = double vision/diplopia

Superior oblique

-INTORSION - moving eyeball downwards and in -If eye adducted: depression -Other actions of depression and abduction (not main)

Scleritis

-Inflammation of sclera -May be really painful because extraocular muscles insert onto the sclera

Vestibular nystagmus - turn head to right

-Involuntary eye oscillations activated by rotation of the head --> activate vestibular apparatus (semicircular canals) in inner ear --> activate VOR -WHen head rotation is greater than can be compensated for the VOR, a rapid reset will occur (nystagmus) in same direction as rotation, then VOR will happen again Turning head to the RIGHT - right-beating nystagmus: -VOR will be activated (vestibular nuclei sending signals to the abducens nuclei) to move the eyes to the opposite side - left side --> slow beat to the left -Rapid beat occurs to the RIGHT to reset eyes (same direction of rotation of head) -VOR will then occur again -repeat

Nystagmus

-Involuntary, jerking movements of the eyes - back and forth rhythmic eye movements -Cortical inputs trying to correct eye movements to center -2 phases: fast beat (saccade/reset) and VOR (slow movement) -Named for the fast/rapid component (e.g. right nystagmus = fast beat to right) -Can occur in any axis but horizontal is most common - Can be caused physiologically by stimulation of vestibular system (NORMAL), by visual stimuli (NORMAL), or pathological processes -Pendular nystagmus: goes around in circle, cannot define if it is horizontal

Horizontal gaze wiring

-Lateral rectus muscle on one side and the medial rectus on other side must work together to move in the same horizontal direction -Horizontal gaze center: PPRF OBJECT ON LEFT 1) Horizontal gaze center (PPRF) gets signal from frontal eye field and gives input to the abducens nuclei to direct gaze to the ipsilateral side 2) From the abducens nuclei, a subset of neurons project directly to the ipsilateral lateral rectus and direct it to look LEFT 3) From abducens nucleus, another subset of neurons crosses the midline and travels in the medial longitudinal fasciculus (MLF) to the contralateral oculomotor nucleus 4) Oculomotor neurons project to the ipsilateral medial rectus muscle, and the eye will move to the left (contralateral side)

CNVI palsy

-Lateral rectus not working - eye cannot abduct -Medial rectus is unopposed so eye rests in adduction

Myopia

-Light lands too far in front of the retina - convergence point anterior to retina -May be due to too much refractive power or AP distance of globe is too long -See better from a near distance -NEARSIGHTEDNESS Lens shape: Concave - curved inwards to move image to back of the retina

Retina

-Light sensitive layer of the eye; contains rods and cones -Behind the vitreous humour and is red - lots of blood flow -Made of an repithelial layer and neural network of cells -Retinal pigmental epithelial layer = has melanin and supports neurosensory layer -Neurosensory layer: captures photons of light

Frontal gaze center/Frontal eye field

-Located in frontal cortex, processes information from the contralateral visual field and communicates with the contralateral PPRF in the pons -Responsible for saccadic eye movements + voluntary eye movement -The FEF communicates with extraocular muscles indirectly via the paramedian pontine reticular formation.

optic disc

-Medial to macula/fovea -Region at the back of the eye where the optic nerve meets the retina. It is the blind spot of the eye because it contains only nerve fibers, no rods or cones, and is thus insensitive to light.

Optic nerve position in relation to the fovea Optic nerve is surrounded by...

-Medial to the fovea -Surrounded by the optic disc --> beginning of the optic nerve/blind spot

Uvea

-Middle coat of the eyeball; includes the iris, ciliary body, and choroid -Between retina layer + sclera

Choroid

-Middle, vascular layer of the eye between retina and sclera -Provides oxygen and nutrients to outer layers of the retina (neurosensory layer)

Pupils - sympathetic vs parasympathetic

-Miosis = constrict -Mydriasis = dialate Parasympathetic: constrict Sympathetic: dilate - allow more light in

Tears - 3 layers of tear film

-Moistens the conjunctiva and cornea and sclera -Provides nutrients, keeps debris and unwanted material out of eye 1) Water film: for clear optimal transparency, coming from the lacrimal glands 2) Lipid film: from the Meibomian glands of the eye >Disease states lead to drying of the eye --> dry eye syndrome b/c not enough oil 3) Mucinous: prevents early desiccation of film >Conjunctival goblet cells of eye

Open-Angle Glaucoma

-Most common form of glaucoma, where the trabecular meshwork gradually becomes blocked, causing a buildup of pressure -May be due to genetics or secondary causes -Gradual onsets - neurotoxins/chemicals slowly damage optic nerve -Painless unlike in closed-angle clients, and may not know that they have this until vision loss is worsened -Often damages peripheral vision first, with center being okay -Once CNII is damaged, there is no regeneration so it is very important to get pressure down to preserve vision

Emmetropia

-Normal relationship between the refractive power of the eye and the shape of the eye that enables light rays to focus correctly on the retina -Perfect vision: 20/20, very small % of the population -Light falls perfectly on back of retina

Cataracts

-Opacification of the lens (normally clear) -Related with increasing age, clumps of proteins reduce transmission of light to retina -May be accelerated due to medical conditions like diabetes -1/2 of all causes of blindness -Lens may become hard and cannot accommodate as well, and cloudiness of lens leads to scattering of light and poor refraction -Light might scatter in front of retina (myopia) -Increase falls risk -Hard to see clearly, blurred, double vision, contrast sensitivity problems, cannot see at night, halos around light, glare, colour contrast problems

Pupil

-Opening through which light enters the eye at center of the iris -Black in colour because does not reflect back out light (absorbs it all)

Bitemporal hemianopsia

-Optic chiasm lesion/compression - pituitary tumour or aneurysm may lead to this -Compresses the nerves that come from the nasal aspect of the retina -Unable to see the temporal aspects of an object (b/c the nasal aspect of retina sees temporal aspect of visual fields) -Still can see nasal aspects of objects

Closing eye muscle

-Orbicularis Oris (CNVII)

Pie in the floor

-Parietal lobe damage -Baum's loop damage -Unable to see contralateral bottom quadrant

Phorias

-Partial changes to eye that are NOT manifest (not present all the time) -Diplopia that comes and goes, mostly with fatigue - double vision when tired -Must actively keep eyes in line for conjugate gaze -Phorias may become tropias (permanent and manifest) Esophoria- In Exophoria- Out Hyperphoria- Up Hypophoria- Down -Must test using cross-cover test to break fusion

How does light pass through the retina through the layers

-Pigment epithelium: lowest layer closest to the choroid (posterior) attached to the photoreceptors anteriorly. -Neurosensory retina is composed of 3 layers :photoreceptive. bipolar, and ganglion ---> light passes through 10 layers of cells 1) Light first passes through all of the layers of cells to activate the photoreceptors (rods and cones) - receptor cells 2) Photoreceptors activate bipolar cells (1st order neurons) 3) bipolar cells activate the retinal ganglion cells (2nd order neurons) 4) retinal ganglion cells --> axons group together and exit eye @ optic disc and form the optic nerve to go to the brain 5) optic nerve goes to the LGN (3rd order neurons)

Conjunctivitis

-Pink eye -Infection of the conjunctiva/inflammation - outer layer of sclera -No real nerve endings, so usually won't have pain unless other things are going on -May be infectious in etiology - Viral, bacterial, fungal, allergic

Treatment for AMD

-Prevention: sunglasses -Vitamins may slow progression -Injections might help -Often is progressive and will lead to blindness -Retinopathies = irreversible, glasses don't work

How is aqueous humour drained

-Production occurs in the ciliary body of posterior chamber, and from there it goes to the anterior chamber and nourishes the cornea -Not an entirely closed system and has to drain - goes through the trabecular meshwork through to the Canal of Schlemm, into the venous system

Sclera

-Protective white part of the eye (posterior 5/6 of the globe) -Continuous with the cornea and maintains shape of globe, provides attachment for extraocular muscle insertions -Non-refractive

Saccades

-Rapid, voluntary movements of eye that shifts center of the gaze from one part of visual field/fixation point to another -More common than smooth pursuits -reflexive: external visual stimuli -Volitional: independent of visual stimuli >Anti-saccade - averting eyes >memory saccade - directing eyes to where something had been >predictive saccade - directing eye to where object is expected to be

Optokinetic nystagmus

-Rapidly moving object within field of view or rapid movement past an object in field of view --> eye follows object that is moving in the field of view e.g. rapidly passing by powerline poles as looking out of window -Focus will be rapidly reset to next object in field of view --> slow beat will follow one powerline pole, then rapid component will reset to the next -If you are the one moving: Nystagmus (fast beat) is in the same direction that you are moving (but opp direction of object you're trying to focus on) -If object is moving (GAZE-EVOKED): fast eat/nystagmus will occur in opposite direction object is moving (e.g. drum rotating down, fast beat is up) - slow gaze = smooth pursuit - following object

Visual function testing - visual field tests

-Red Dot Confrontation Test -Kinetic Two Person Confrontation Test

Glaucoma

-Refers to neuropathic deterioration of the optic nerve -Increase intraocular pressure -Can present acutely (closed-angle) or slowly (open-angle) -Based on anatomical changes that occur at angle of iris + cornea -If untreated, the pressure pushes retina of eye, compressing and killing axons of ganglion cells - damaging optic nerve

Astigmatism

-Refractive error of vision due to differences in curvature in refractive surfaces of the eye (cornea and lens) -Abnormal shape of cornea - deviation from perfect sphere may lead to hyperopia or myopia - blurred vision

Ametropia

-Refractive error where light is not centered in the retina -May be due to mismatch between axial length of eye (A-P length) and refractive power of the cornea or lens accommodation ability

Is the retina vascular or avascular?

-Retina is one of the most metabolically active tissues in the body, consuming high levels of oxygen and nutrients. -Vascular system - choroid adapts to meet the metabolic requirements of the retina to ensure visual function

Object on LEFT with damage to the RIGHT MLF (right internuclear ophthalmoplegia)

-Right frontal eye field is triggered, and sends a signal to the left PPRF -Left PPRF activates the left abducens nuclei -Left abducens neurons travel to the left eye lateral rectus and it moves to elft -Neurons from abducens cannot travel to the right side via MLF b/c it is damaged, so the right oculomotor cannot be stimulated and the right eye cannot look medial

Iris

-Ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening -Controls amount of light entering eye via pupil

Ciliary body

-Ring of tissue that encircles the LENS and has a muscular component to adjust refractive power of lens (accomodation via ciliary muscles which are smooth muscles) and ciliary processes that produce aqueous humour -In posterior chamber Z

Vergence center

-Rostral midbrain near CNIII nucleus Object near: -Vergence center in the midbrain --> sends excitatory signals to the CNIII to activate medial rectus, and inhibitory signals to CNVI --> eyes converge Object far: -Vergence center activates CNVI in pons to activate lateral rectus and eyes diverge

Reflexive saccades

-Saccades generated to novel stimuli (visual, auditory, or tactile) that unexpectedly occur in the environment -Additional input from the superior colliculus compared to volitional saccades -Superior colliculus = layered structure located on posterior part of rostral midbrain -Frontal eye field will send inputs to the ipsilateral superior colliculus -Superior colliculus projects to contralateral PPRF -Superficial layer of superior colliculus = visual layer, and receives input from the retina via the LGN of thalamus -Deeper layers of superior colliculus contain motor layers that project to PPRF to initiate saccades for horizontal movements, or rMRF for vertical movements -Superior colliculus will also receive input from extrapyramidal sources like cerebellum + basal ganglia

Reflex of eye blink

-Sensory: CNV1 -Reflex: Orbicularis Oris CNVII - close eyelid

Vertical gaze

-Similar to horizontal gaze, and cortical input is still provided by the FEF as well as the parietooccipital lobe --> supranuclear inputs -Vertical gaze center: rMRF -Conjugate elevation and depression -Can be a saccade or a smooth pursuit -Elevation: IO, SR (CNIII) -Depression: SO (CNIV), IR (CNIII) -rMRF --> sends signal to the CNIV nucleus --> Superior oblique contracts -rMRF --> sends signalto CNIII to trigger IR, SR, and IO -No fasciculus because CNIV and CNIII are cloes to each other, and close to the rMRF

Treatment of glaucoma

-Some pharmacological methods may be used for open angle glaucoma to bring pressure down, or decrease production of aqueous humour -Iridotomy: shoots a laser to open a safety valve to allow aqueous humour to drain through the iris from anterior chambers for closed angle

Primary visual cortex

-Striate cortex that receives input from the LGN neurons -In the occipital lobe -Located superior and inferior to the calcarine sulcus -Information from superior visual field is represented in inferior part of calcarine sulcus

CNIV palsy

-Superior oblique not working - normally does intortion (down and in) -Eye will by hypertropic: above the midline and exortion: looking outwards

Treatment of cataracts

-Surgery to remove the lens and replace it with an intra-ocular implant - clear lens -Very good results

Pie in the sky

-Temporal lobe damage - Meyer's loop -Unable to see CONTRALATERAL visual field (e.g. damage to the left loop = unable to see the right top quadrant)

Visual field testing

-Test of peripheral vision -May indicate central lesions like strokes and tumours -Can indicate a distal peripheral lesion such as glaucoma -Asks you to focus on an object and show objects in the periphery and click on something to indicate if you see it or not

Amsler grid

-Test to assess central vision and to assist in the diagnosis of age-related macular degeneration

BiVABA - purpose

-The Brain Injury Assessment Battery for Adults Purpose: -Screens for visual impairments, provides information on FUNCTIONAL limitations and how vision problems impact ADLs -Alerts OTs for need for further referrals NOT at DIAGNOSTIC TOOL

Hyperopia

-The light lands too far behind the retina -Axial length of globe may be too short, or may have poor refractive power -People see better from a distance - FARSIGHTEDNESS LENS shape for correction: convex to allow for more refraction

Homonymous hemianopsia

-The loss of the right or left half of the visual field in both eyes. -Optic tract lesions

Visual tract (describe how left eye sees things)

-The nasal aspect of the left eye sees the temporal aspect of the left visual field -The temporal aspect of the left eye sees the nasal aspect of the right visual field -The nasal hemiretina crosses the optic chiasm to project to the other side of the brain -The temporal hemiretina projects to same side of the brain -After the optic chiasm, the optic nerve changes it's name to optic tract and it projects to the LGN of the thalamus -From the LGN of the thalamus there are optic radiations: Baum's Loop and Meyer's Loop

Vergence

-The two eyes move in opposite directions, as when both eyes turn towards the nose CONVERGENCE = eyes ADDUCT when bringing an object close to patient - accomodation test DIVERGENCE = eyes ABDUCT when looking at something far away - moves outward away from the nose

Vitreous humour

-Thick, jelly-like substance which helps to maintain the shape of the eye and also helps focus light/allow for proper refraction -Between the lens and the retina

Retinal detachment

-Thin layer of retina at back of eye pulls away from middle layer of blood vessels (choroid) -Tear in retina may lead to fluid passing through and colleciting under it, pulling it away from the choroid -Leaking BV may occur behind retina, leading to increased pressure and more detachment -May lead to permanent blindness -May have either small spots of blindness or curtain vision -Medial emergency floaters and flashes of light. curtain vision

Neurosensory retina

-Thin transparent layer of neural tissue in which light stimuli are converted into nerve impulses in the photoreceptors and relayed to bipolar then retinal ganglion cells -Rods and cones (photoreceptors) capture photons and transmit them via phototransduction

Fovea centralis

-Tiny pit or depression in the retina that is the region of clearest vision -Within the macula -Highest concentration of cones - where we want light to focus on -Ideal: bifoveal fixation of an object to get best resolution of object

Lens

-Transparent biconvex body behind the pupil of the eye (behind iris) -Very important for refraction - changes shape to change refractive power -Can reduce its anterior-posterior diameter, known as accommodation

Cornea

-Transparent outer covering of the front of the eye -Continuous with sclera -Very important for refraction -Anterior to iris -No blood vessels unlike sclera, so it must receive nutrients from aqueous humour

Left optic tract lesion

-Unable to see the right visual field -Cannot see both the nasal + temporal parts

Midbrain damage impacts what gaze

-Vertical gaze because the vertical gaze center is in the rostral midbrain (rMRF)

VOR nuclei

-Vestibular nuclei (CNVIII), CNVI, and CNIII involved -Vestibular inputs will either inhibit or stimulate CNVI and CNIII -Vestibulocochlear nerve: gives you position in space without cerebellar or cortex inputting - vestibular inputs tell you where you are in space, and sends signal to eye to keep track on objects

What components are part of physical exam of eye

-Visual acuity -Extra-ocular movements -Intraocular pressure -Pupils

Slit lamp examination

-Visual testing of the cornea, lens, iris, sclera, fluids, and membranes of the interior of the eye using a narrow beam of light -Magnified view of anterior eye structures in detail - precise analysis of all areas

Ventral stream of vision

-WHAT -Temporal lobe -Object vision/colour/shape perception and recognition -Access memories -spatial relationships

Dorsal stream of vision

-WHERE and HOW -Parietal lobe -Spatial vision - where, motion and spatial awareness -Important for visually guided actions - eye-hand coordination, navigation

Abnormal pupils

-no reaction, dilated, constricted, sluggish reaction, asymmetrical, ones slide could be sluggish, one side brisk -pharmacalogical interventions, acute trauma, CN palsies or Horner's syndrome, toxicity - opioid overdose = constrict pupil -lower MN lesion of parasympathetic/sympathetic system may cause changes -Upper MN lesions can also cause changes like stroke or traumas in brain stem -CNIII damage --> dilated pupil; normally it constricts pupil

Steps of the VOR

1) Head movement detected by vestibular organ (semicircular canals) which activates vestibular nerve + impulses get sent to the ipsilateral medial vestibular nuclei (e.g. movement to right --> activate vestibular nuclei on the right) 2) Vestibular nuclei sends impulses to the contralateral abducens nuclei, and a subset of neurons send projections to ipsilateral lateral rectus muscle (left eye moves to left b/c head turned to right) 3) Subset of neurons from the abducens nuclei will send projects to the contralateral oculomotor nuclei via the MLF, to activate that eyes medial rectus, moving it to the contralateral side of head rotation *other side sends inhibitory signals

3 controls of gaze

1) Supranuclear: cortex, above the CN nuclei 2) Nuclear: brain stem nuclei (abducens, oculomotor, trochlear) 3) Infranuclear: peripheral nerves - efferent to nuclei of the cranial nerves

Visual perceptual hierarchy

1. Foundational skills: a. Oculomotor control b. Visual field c. Visual acuity >Basic skills that alert individual to object + situations in the environment, allowing you to pay attention to things 2. Intermediate-level skills: a. Attention b. Scanning or visual search c. Pattern recognition >Attention allows you to visually scan environment and start to recognize patterns 3. Advanced-level skills: a. Visual memory b. Visuo-cognition. c. Adaptation through vision >Recognizing patterns allow you to connect to visual memory and identify what is going on - make decisions about what you are seeing, and adapt behaviour based on interpretation

Extraocular muscles + innervation

6 muscles: Superior rectus Inferior rectus Superior oblique Inferior oblique Medial rectus Lateral rectus -Some insert right onto the sclera CNIV: Superior Oblique CNVI: Lateral Rectus CNIII: Inferior oblique, superior and inferior rectus, Medial rectus

biVABA vision subsets

A) Measuring Visual Functional Performance a. Clinical observations assessment B) Basic Visual Function Assessment a. Pupillary response b. Eye dominance c. Acuity - for near and far and intermediate reading d. Contrast sensitivity e. Visual field C) Oculomotor Function Assessment a. Visual history b. General appearance of eyes c. Corneal reflections d. Eye movement e. Convergence f. Diplopia testing D) Visual Attention Assessment a. Search strategies for near space - structured visual array b. Search strategies for unstructured visual array c. Attention to detail d. Search strategies for extra personal space

Somatic sensory innervation of eye

CNVI - ophthalmic branch of CNV

Exotropia Esotropia Hypertropia Hypotropia

Exotropic: Movement of one eye away from the midline Esotropic: Movement of one eye towards the midline Hypertropic: above midline Hypotropic: below midline

Keratitis

Inflammation of cornea -Leads to pain - CNV1 sensory endings pick this up -Cold sore in eye or herpes infection

Right optic tract lesion

Left homonymous hemianopia -Cannot see the left visual field

Baum's loop

Part of visual pathway In Parietal lobe Damage--> quadrantic anopia (Pie in the floor)

Meyer's loop

Part of visual pathway in the temporal lobe Damage --> pie in the sky

Fundus of eye

Posterior/back of eye; inner part of the eye; visualized with an ophthalmoscope

One eye -duction movements

Primary position: If one person is sitting ahead and looking in front of you Adduction: Towards the midline (nose) Abduction: Away from the midline (temporal) Elevation: Looking up (supraduction) Depression: Looking down (infraduction)

Pupillary function assessment

Pupillary appearance - look at size and symmetry of the pupil - ask client to look at something around 6 feet away behind you, and examine their pupils i. Pupil asymmetry: pupillary reflexes, what happens in one eye should be the same in the other eye - the pupils should appear the same; may be a result of brain injury or concussion (e.g. decreased blood flow to brain stem) ii. Pupil size: Iris has special muscles that constrict pupils to minimize light coming in -Iris relaxing = opening of pupil becomes larger -In darker situations, pupils will dilate so more light comes in -Pupil is black because tissues in pupil absorbs all the colour from the light and doesn't get reflected back out -Eye light: shine light in the eye --> has gauge on it with different size of pupils, and you can measure size of pupil and compare it in each eye -Actual size of pupil will vary depending on how much light is in the room - if dimmer, pupil may dilate more, if brighter, pupil will constrict to prevent excessive light

Pupil size in low vs. high light

Responsiveness to light: - If pupil is relatively small, there is probably a moderately high level of light in room and entering eye >Pupils also constrict when looking at close objects + during parasympathetic response (CNIII) - If pupil larger, probably decreased light in the room so have to dilate pupil to get more light to enter it >pupils also dilate when looking at far objects and during sympathetic response

Pupil test procedure

Testing pupil on patient: - Use a pen light - has a gauge on it showing you size of pupils - Normal size = 3-5 millimeters, and should be ROUND - Ensure room is pretty dim - Direct response o Shine light in one eye and look at that pupil to see if it constricts and how well it is - should smoothly constrict and then dilate back normally - Consensual response o Look at opposite eye and make sure both pupils constrict simultaneously TOGETHER - Swinging test: swing the light between eyes every 2-3 seconds and should see that pupils get SAME reaction (constrict in one leads to constrict in other) - Accommodation response: eye fixated at something in front of them and then slowly move it towards their face and see if the pupils converge and if they constrict together -PERRLA - Pupils, equal, round, reactive to light, accommodating

Quadrantic anopia

Visual loss in one quadrant (1/4) of the visual field (contralateral) -Damage to either Meyer's Loop (temporal) or Baum's loop (parietal) (optic radiations)

biVABA acuity test

a. Acuity - uses modified Snellen chart i. Intermediate distance (1 metre) -Intermediate acuity test chart/low vision leaNumbers chart ii. Reading acuity -Sentences get smaller and smaller further down - functional assessment of reading acuity Warran text card

Diabetic retinopathy

disease of the retina in diabetics characterized by capillary leakage, bleeding, and new vessel formation (neovascularization) leading to scarring and loss of vision -Increase blood sugar in body = blockage of tiny blood vessels within the retina --> microaneurysms LEAK - blood flows into retina and certain parts of retina will lose circulation, becoming damaged -Patchy vision loss --> random areas where retina is damaged and deprived of O2 -May lead to glaucoma as fluid buids up -Can lead to retinal detachment --> blood vessel leakage leads to scar tissue formation and pulls retina away