Transcript The Visual Process & Implications of Visual Disabilities

CLINICAL PERSPECTIVES
STRUCTURES AROUND THE GLOBE
Orbit- provides a safe place for the eyeball
eyelids- closes light off of eye, protects, distributes tears
tears- lubricates & protects
lacrimal system- distributes tears
conjunctiva- covers sclera and inner surface of eyelids
orbital septum- bone covering top of orbit
eyebrow- covers orbital septum, protects eye from sweat
• Photos courtesy of the National Eye
Institute
• [email protected]
Extraocular Muscles
• Superior & Inferior Recti
• Medial & Lateral Recti
• Superior & Inferior Obliques
Eyelids & eyelashes
• meibomian glands- oil glands
Conjunctiva
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sclera- white fibrous covering of
eyeball
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limbus- point where sclera and
cornea meet
Lacrimal Apparatus
• puncta- inner margin of the upper & lower
lids
• caniliculi- passages to sacs & ducts
• lacrimal sac- contains some tears
• nasolacrimal duct- drains tears into nose
Eye Divided Into Two Parts
• Anterior Segment
– aqueous humor
– pupil
– Iris
– lens
• Posterior Segment
– vitreous humor
– retina
– optic nerve
Cornea
• clear, avascular window of the eye, most
refractive power
Anterior Segment
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aqueous humor
trabecular meshwork
canal of Schlemm
ciliary process
lens
Pupil & Iris
• Pupil- adjusts light
• Iris- pigmented muscular ring
Structures In the Globe
• 3 Main Structures:
– protective outer layer
– vascular inner layer
– sensory retina
Vascular Inner Layer
• Uveal tract
• Ciliary body
• Choroid
Sensory Layer
• Central Retina
– Macula & fovea contain mostly cones
– Optic disk
• Peripheral Retina
– Contains mostly rods
Transmission of Visible Information
to the Brain
• Light energy from environment to chemical
energy in retina to electrical energy in
optic nerve & synapses to chemical
energy in nerve cells
Relationship of Sight to Vision
• Images from eye structures must be
interpreted in the visual cortex for sight to
occur
• The eyes and associated structures must
be normal in structure & function.
• The neurological pathways from the retina
& optic nerve to the visual cortex must be
in tact.
• The brain must be capable of interpreting
the information received.
MEDICAL EYE REPORT
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Name
Sex
Age
Family Medical Hx
General Medical Hx
Surgical Hx
Medications
Ophthalmic complaint
Eye Care Professionals
• Optometric technicians, ophthalmic
technicians
• Vision Rehabilitation practitioner
• Teacher of Visually Impaired
• D.O.- doctor of optometry, doctor of
ophthalmology, low vision specialist
• M.D.- ophthalmologist
• Specialist- did fellowship in specialty,
FACS
• optician
VISUAL ACUITIES
• Autorefractor
• Lensometer
• Snellen chart (distance)
• Checking distance each eye using an
occluder
• Jaeger near vision chart
• Ishihara- color vision charts
• Titmus fly
• Amsler grid
External Examination
• LLL- Lids, lens, lacrimal system
CAUSES & FUNCTIONAL
IMPLICATIONS OF VISUAL
IMPAIRMENT
• PERL- Pupils equal & reactive to light
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• MM- Muscular motility
• Eye Muscle Balance
Cornea & Anterior Segment
• Ophthane- numbs eye
• Midriatic- dilates pupil
• Cycloplegic- relaxes lens
• Tonometer- measures pressure
– FP- finger pressure
– Air puff
– Contact
• Keratometer- measurement of corneal
thickness
• Goniometer- measures angle of anterior
segment (risk factors for glaucoma)
• Slit lamp
• Direct ophthalmoscope
Undilated versus Dilated Pupil
• Indirect ophthalmoscope
Normal Fundus
• Phoropter
Functional & Visual Efficiency
Testing
• Behavioral
• Electrophysiological
• Subjective
Behavioral
• OKN (optokinetic nystagmus)- cortical
• PLT (preferential looking test)- Teller
acuities
• Chromatic luminance- contrast sensitivity
• Tracking a toy or light
Electrophysiological
• Fundus photos & OCT
• VER- visual evoked response- visual
pathways, cortical function
• ERG- electroretinogram (cone & rod
function)
• EOG- electrooculogram (measures charge
& potentials of eyes)
Subjective
• Acuity
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Lea charts
Snellen
Tumbling E
Amsler grid
CSF- contrast sensitivity function
Flicker fusion macular & foveal function
Color- Ishihara & Farnsworth
Visual fields
– Confrontation
– Ganzfeld globe
– computerized
Visual Efficiency Testing
• ISAVE
• Program to Improve Visual Efficency
(Barraga)
• Conditions That Result In Low Visual
Acuity
Ocular Muscle Disorders-
• eyes that are not in proper alignment
Strabismus & Amblyopia
amblyopia- a reduction in visual acuity due
to non-use of the eye
• tropia- marked deviation of an eye
• esotropia- turning in of one or both eyes
• exotropia- turning out of one or both eyes
• hypertropia- turning up of one or both eyes
• hypotropia- turning down of one or both eyes
• phoria- tendency of eye to deviate, particularly
when fatigued or fusion broken
Nystagmus
• Involuntary, rhythmical repeated
movement of one or both eyes in a
horizontal, vertical or pendular motion
– null point- point of least nystagmus & best
vision
– pendular nystagmus- up-and-down
movements of equal speed, amplitude &
duration
– jerk nystagmus- slower movement in one
direction