Chapter 8

VISION

- One of the five senses- Most primary sense

The _____ obtain the visual information from the environment by controlling the muscles that look for and find a target.

eyes

The _____ then receives and interprets this information, allowing for an action to be taken.

brain

Ophthalmologist

Diagnose conditions of vision loss and medical management of these conditions

Optometrist

Perform eye examinations to assess general I site in the need for corrective lenses and prescribe medications for eye diseases, train and vision therapy, and are also known as Nuro optometrist

Physiatrist

Physical medicine and rehab doctor, Can you refer Client to OT services

Certified low vision therapist (CLVT)

Works with clients with visual impairment to improve their functioning of daily skills using remaining vision in adaptive devices the skills main clue computer use communication skills such as reading and writing in braille and home management

Certified vision rehabilitation therapist (CRVT)

Works for clients to increase independence with adaptive devices including home management outside employment

Certified orientation and mobility specialist (COMS)

Teaching clients travel and ability skills including using a sided cane or white cane used to locate obstacles that may be in the way of mo that mobility and preparing to utilize a guide dog.

Lens

Focuses light rays onto the retina

Cornea

Clear part covering the pupil and iris; lets light into the eye

Pupil

Dark, round center of the eye; opens and closes to regulate the amount of light the retina receives

Iris

Colored part of the eye

Vitreous Body

Lies between the lens and the retina and holds these structures in place. Contains a clear jelly,called vitreous humor, which assists with transmitting light

Optic Nerve

Nerve that carries impulses from the eye to the visual cortex to the brain

Fovea

Located in the retina, provides the most acute vision

Macula

Located near the middle of the retina. Enables visualization of objects with great detail

Retina

Sensory membrane that lines the eye. Receives images from the lens and converts them intosignals that reach the brain via the optic nerve

Choroid

Layer of blood vessel; provides nourishment to the back of the eye

Sclera

White portion of the eye

The eye has _____ ______ that work in conjunction to allow full range of motion for scanning the environment to bring information to the brain.

seven muscles

If one of these muscles is impaired, or if the muscle is not receiving the message from the brain because of a nerve injury, this will affect the eye's _____ __ ______

range of motion

Cranial Nerve II (CN II)

- Optic nerve- Carries impulses from the retina to the brain (vision)

Cranial Nerve III (CN III)

- Oculomotor nerve- Moves all extraocular muscles, except the superior oblique and lateral rectus. Also controls the size of the pupil and elevating the eyelid

Cranial Nerve IV (CN IV)

- Trochlear nerve- Motor control of the superior oblique muscle

Cranial Nerve VI (CN VI)

- Abducens nerve- Motor control of the lateral rectus muscle

CN III palsy

Functions: Eye turns down and out, eyelid droops (ptosis), dilated pupilsIf Nonfunctional: Diplopia (double vision),difficulty with depth perception,difficulty with reading,convergence insufficiency

CN IV palsy

Function:Outward rotation of the upper portion of the eyeIF NONFUNCTIONAL:Vertical diplopia, difficulty withreading, computer work, andwalking down steps.Client may turn his or her headdown and out to compensate

CN VI palsy

Function: Eye drifts in toward the noseIf Nonfunctional: Diplopia; client may turn head tothe side to compensate

Injury to a motor nerve leads to

palsy

Acuity

sharpness of vision

Visual field

•Extent of visual space that is visible‒65 deg upward‒75 deg downward‒95 deg outward‒Functionally 180 deg horizontally & 125 deg. vertically

Visual field deficits

Blind spots in a portion of the visual field

Types of Visual Field Deficits

HemianopsiaHomonymous hemianopsiaQuadrantopsia

Hemianopsia

Vision loss in one half of the visual field in one eye

Homonymous hemianopsia

Vision loss in one half of the visual field on the same side of both eyes

Quadrantopsia

Vision loss in one quarter of the visual field

Oculomotor control

•Convergence•Saccades•Fixation

Visual Skills and Interventions

- Oculomotor control- Clinical observations- Interventions- Diplopia- Visual attention- Visual scanning

Diplopia

•humans have two eyes - only see one image. - Two eyes not working together because of muscle or nerve weaknessClinical observations•OT Interventions•Physician interventions

Visual Processing Skills and Interventions

- Pattern recognition- Visual memory- Visual perception- Spatial relations- Form discrimination- Figure ground- Visual closure-Depth perception

Visual attention

ability to attend to visual information, determine if information is relevant to a situation.Clinical observationsLess efficient with task completion.Interventions for impaired visual attentionRemove all distractionsBegin in these quieter environments and then add small distractions.

Visual Scanning

(smooth pursuits) - how the eyes move to obtain information.Normal scanning pattern is left to right, top to bottom, in the alphabets of English and French (Canada).Clinical observationsDifficulty with readingDifficulty with visual scanningINTERVENTIONS Tabletop scanning in these directions in an organized manner.Utilize a more disorganized patternIncorporating this into a functional task,

Pattern recognition

ability to identify details of objects to determine what the objects are.INTERVENTIONS compensatory strategies by teaching clients different ways to determine what they are seeing.Look for distinguishing featuresMarked differently, such as with colored duct tape.Write the object's name on a piece of tape and attach it to the object.

Visual Memory

remembering what is seen.INTERVENTIONSCompensatory strategieswriting it downwrite the specific features of an item to assist with recallBasic tabletop tasks. Start with 1 picture/item progress to multiple items and functionalLook at the picture of the cars for 5 secondsHow many cars are there? - 9How many were red - 3How many were white - 1

Visual perception

...the dynamic process of receiving the environment through sensory impulses and translating those impulses into meaning based on previously developed understanding of that environment.

Spatial relations

•Knowing where an object is in relation to self & others

Form discrimination

•Discriminating the important features of different objects

Figure ground

•Distinguishing objects from surrounding objects

Visual closure

•Perceiving the whole picture when only pieces are available for visual interpretation

Depth perception

•Knowing how far away an object is

Hemi-inattention

•Decreased awareness of one side of the body/environment

Hemi-inattention interventions

‒Environmental adaptations‒Safety concerns‒Use mirrors‒Weightbearing through affected side

Hemi-neglect (unilateral neglect)

•Severe form of hemi inattention•No awareness of a side of the body

Agnosia

inability to recognize/perceive sensory info

Prosopagnosia

inability to recognize faces

Simultagnosia

inability to perceive entire picture or integrate it parts

Tactile agnosia (astereognosis)

inability to recognize objects by feel

Auditory agnosia

inability to recognize sounds

Object agnosia

inability to recognize objects

Intervention is generally ________ strategies

compensatory

_________ _________ is a visual impairment that cannot be corrected by medical or surgical intervention and is severe enough to interfere with the performance of activities of daily living, but allows some usable vision. Low vision is typically caused by diseases of the eye itself and does not always consist of neurological deficits at the brain level.

low vision

LOW VISION/CATEGORIES OF VISUAL LOSS

- Normal- Near Normal- Low Vision (A person with low vision is not blind)- Blindness (A lack of light perception and usable vision)

Legal Blindness

-means that the acuity is no better than 20/200 with best correction in the better-seeing eye (glasses or after surgery) or only 20 degrees or less of total visual field in the better-seeing eye. This is still very usable vision.-The term legal blindness can be confusing.-Term used by the government to determine whether a client qualifies for government services and benefits.

Age-related macular degeneration (ARMD or AMD)

‒Loss of central vision--Maintain peripheral vision‒Central blind spot known as scotoma‒ Cell death occurs in the macula due to lack of oxygen and a build-up of waste products. Lose central vision but keep peripheral vision.‒2 types - Wet and Dry

Dry Age-related macular degeneration (ARMD or AMD)

‒most common; *gradual loss of vision; *waste deposits on macula

Wet Age-related macular degeneration (ARMD or AMD)

‒more severe; unstable; abnormal bld. vessels under macula that tend to hemorrhage; *loss is usually sudden; *laser tx often recommended to stop bleed

Diabetic retinopathy

‒Vision loss/blind spots‒"Swiss chees vision"‒Typically, a complication of diabetes (Type 1 and type 2)‒affects the blood vessels of the entire retina, causing decreased circulation and hemorrhages that will lead to varying levels of vision loss (blind spots).‒Caused by damage to tiny blood vessels in the retina; over time can get worse and cause total blindness; typically has no early warning signs

•Glaucoma-

‒Decreased peripheral vision (tunnel vision)‒gradual degeneration of cells that make up the optic nerve which carries visual information from the eye to the brain. As the nerve cells die, vision is slowly lost; associated with elevated intraocular pressure.

•Cataracts

‒Clouding of the lens of the eye can affect one or both eyes‒Increased glare from lights

The focus of ___ is on compensation, adaptations, equipment, and environmental modifications

OT

OT treatment

•Education•Environmental adaptations•Color contrast•Tactile cuesLighting

Aids

•Magnifiers•Writing aids•Kitchen aids

Reading with Low Vision

-Techniques vary with Dx, field of view, & central vs. peripheral• Matte paper• Finger guiding• Anchor lines• Good lighting• ContrastLarger font

Psychological Impact of Low Vision

-Can be devastating•Loss of function & independence-OTA role•Emotional support to client/family•Info re: support groups/counseling•Resources for leisure activities