Transcript Anatomy & Function and Ocular Disorders Part 2

Anatomy and Function of the Eye
and Ocular Disorders
Part II
Developed by
SKI-HI Institute
Utah State University
Winter 2011
For use in Training
The Human Eye
retina
macula
fovea
optic nerve
optic disc
choroid
vitreous humor
La Clinica Oculistica Virtuale
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Choroid
• If deprived of its blood supply for
more than a few minutes, will die
• Cannot be regenerated
• Nourished by blood vessels that
enter eye near optic nerve and
which spread across surface of
retina
• Choroid supplies retina with
nourishment
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Rod and Cone Cells
Rods
• More in the peripheral
retina
• Detect motion
• Function at low luminance
level…night vision
• Gross forms and shadow
Cones
• Color vision
• Detail, reading vision
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Night Vision and Night Blindness
http://www.sapdesiguild.org
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Prematurity and ROP
• Factors causing ROP are: excessive
oxygen, prematurity, infection,
excessive exposure to light
National Eye Institute, National Institutes of Health
• Babies born today are more
premature and lower in weight
• Aggressively treated and have a perilous neonatal period
full of numerous life sustaining procedures
• Medical technology has increased survival, but not the
chances of ROP occurring
• ROP a major cause of infant blindness in developed
countries
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The Disease Process in ROP
• Baby born early, retina has not
vascularized yet—blood vessels
grow from optic nerve head
to outer reaches of retina
• Growth stops for a while
• Then oxygen causes them to
grow wildly, tangle and grow
into vitreous, not to edges
• Vessels hemorrhage, scar tissue
forms and vitreous contracts,
damaging retina and causing
detachments
National Eye Institute, National Institutes of Health
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Stages of ROP
Stage
Description of Retina
0
No abnormality
1
Minor changes in periphery of retina; some irregular
blood vessels; see white band between area of retina
with and area without blood vessels
2
Same characteristics as stage 1; now area without
blood vessels looks silvery gray and opaque; band has
Increased in height and width
3
Band now forms a thick ridge; lots of blood vessels near
the ridge and spreading into vitreous
4
Peripheral retina starts to pull away, moderate
detachment
5
Advanced or total retinal detachment
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Zones of ROP
• Described as if retina were
the face of a clock
• ROP in zone 1 more serious
as it may involve the macula,
affecting central or reading
vision
• ROP in zone 1, at 1-2 o’clock
position, retinal changes don’t
involve the macula; are
further away
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Treatment of ROP
Observation/Monitoring
• Most babies with ROP get better on their own
• For most, disease can get worse fast and without treatment,
half will end up blind
Surgical Treatments
• May be used alone or in combination
laser photocoagulation
cryotherapy-freezing
surgical repair
• Length of time between detachment
and surgery is crucial to restoring
vision
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Vision Impairment in ROP
• Baby’s vision can vary from near normal to total
blindness, depending on how changes had progressed
prior to diagnosis and treatment
• ROP sometimes spontaneously regresses or cures itself
and retina returns to near normal; rarely happens after
stage 3
• Children with ROP may later develop myopia or near
sightedness, strabismus, cataracts, nystagmus,
astigmatism, microphthalmia, or blue-yellow color deficits
• In the adult years, may develop further myopia,
cataracts, closed-angle glaucoma or further detachment
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Other Disabilities and ROP
70 % of infants born under a pound in weight and
3 months premature have additional disabilities such as:
• Brain damage
• Cerebral Palsy
• Seizures
• Hearing Loss
• Learning disabilities
• Cortical/Cerebral
Visual Impairment
• Sensory Issues
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Other Retinal Conditions
• Macular Degeneration
• Retinitis Pigmentosa
• Ushers
• Leber’s Amaurosis
• Coloboma
CHARGE
• Rubella
• CMV
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Retinoblastoma
• A slow growing malignant tumor that arises from retina
• Hereditary or non-hereditary; one or both eyes
• Both types gradually fill the eye then extend through the optic nerve
to the brain or into sclera and surrounding tissue
• Pupil appears white or glows,
strabismus present, eye inflamed
• Discovered before age of three;
diagnosed by ultra-sound, MRI, CT
• Treatment: may remove the eye; in some cases chemo
or radiation is used; high survival rate
• Cataracts may result from treatment
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Traumatic Retinal
Detachment/Hemorrhage
Shaken Baby Syndrome (SBS)
• Infant forcefully shaken
• Retina detaches as result of direct
traumatic injury or secondary
complication of bleeding in the eye
• Visual impairment due to retinal
detachment, optic atrophy or damage
to visual pathways in the brain
Head Injury
• Similar destruction as SBS, most commonly occurring
in car accident
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Other Infections
Toxoplasmosis
• Infection of eye that is the result of maternal exposure
during pregnancy to a parasite in cat feces
• Can affect the brain as well as the eyes
Toxocara
• Acute inflammatory response inside eye in response to a
parasite in dog feces
• Causes cataracts, inflammation of vitreous
Herpes
• Blood-born viral infection transmitted during pregnancy
or delivery that can cause severe damage to brain and
retina
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Loss of Color Vision
• More common in males than females
• Three types of color photoreceptors in the retina—red,
green, and blue cones; defect may lie in ay of these
• Most common: an inability to distinguish reds and greens
• Present in both eyes and remains constant over time
• Occasionally accompanies retinal disease or exposure to
toxic materials that damage cones
• No known treatment
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Loss of Color Vision Simulated
Normal
Red
Blue
(rare)
Green
graphics.cornell.edu
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Normal vision
Myopia or near sightedness
eyeatlas.com
19
Hyperopia or far sightedness
Astigmatism
eyeatlas.com
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Glasses Can’t Fix Every Eye Problem!
Dr. Lea Hyvärinen, Helsinki, Finland
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Eyes in Constant Motion
Saccades of eye looking
at a photo of a face
Artlex.com
• Human eye is in constant state of
vibration, oscillating back and forth at
rate of 60 per second
• Serve to refresh the image cast on rods
and cones at back of eye
• Without these microsaccades,
staring fixedly causes distortions
• Rods and cones respond best to
changes in color and luminance
• These saccades are so small they are
imperceptible to others
• In many children with poor vision, these
microsaccades are exaggerated, so
we see them as nystagmus
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Nystagmus
• Involuntary rhythmic, jerky eye movement
• Vertical, horizontal or rotary
• May decrease with age
• Slightly blurs vision, central vision decreased
• May hold objects closer to eyes
• May turn head slightly to use null point
• Increases with fatigue, stress, excitement
Dr. Lea Hyvärinen, Helsinki, Finland
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Difficulties with Saccades When Reading
• Children with conditions such as nystagmus or strabismus
may have inefficient reading saccades
• Eye movements may be bigger; less room for error
• They may struggle and lose their place
• Enlarging the print may help
• Using a finger or line marker to keep their place may help
• Presenting print on computer line by line or in shorter lines
Use of finger to keep place
Use of paper as line marker
to keep place
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Random or Roving Eye Movements
• Sign of poor acuity;
takes good acuity to
fixate
• As if eyes are trying to
find a target, but can’t
quite focus on it well
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Medications That Cause Double or
Blurred Vision
• May include antidepressants, antidiabetic drugs,
barbiturates, cortisones, sedatives, and tranquilizers
• Contact physician if any changes are noticed when using
such drugs
•
The side effects can interfere with vision
• Many children with multiple disabilities are on seizure
medications which can cause visual side effects
(blurring, less alert, double vision).
• Great handout on this on website:
www.fpg.1unc.edu/~edin
under Resources, Vision Module, Session 4, handout I
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The Visual System
Wps.prenhall.com
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Normal Optic Nerve
optic nerve
macula
National Eye Institute, National Institutes of Health
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Hydrocephalus
• Increased fluid in the ventricles or water
spaces of the brain
• Put pressure on optic nerve fibers
Child with Shunt
• Prolonged high pressure causes
permanent damage
www.mps1disease.com
• Putting in shunt to drain fluid soon
enough can minimize the damage
• Decreased visual functioning can be a
sign of shunt failure
Optic nerve head in back
of the eye of 2 year old
child with hydrocephalus
www.nature.com/
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Brain Bleeds Around the Ventricles
• Optic radiations pass by and around
the lateral ventricles
Lateral Ventricle
• Low birthweight premature babies may
suffer brain bleeds in the ventricles
Optic
Radiations
• These bleeds can damage the optic
radiations, resulting in vision loss
Lateral Ventricle
(other views)
• Severity of vision loss depends on the
extent of the bleed, treatment, other
medical issues, etc.
Grade III Bleed
in the Lateral
Ventricals
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Optic Nerve Atrophy (ONA)
www.nature.com
• Loss of blood supply to optic nerve
with accompanying gradual vision
loss
• Optic disc is pale when examined
• Change in visual acuity and
peripheral field may occur before
change in the disc is evident; nerve
cells of retina may stop functioning
before the nerve atrophies
• Degenerative condition following
normal function
• Not normally diagnosed in infancy
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Optic Nerve Hypoplasia (ONH)
• Small optic nerves with normal size blood
vessels
• Varying degrees of visual acuity and field losses
• Associated with CNS anomalies
-agenesis of corpus callosum (failure of two
halves of brain to connect)
-endocrine disorders
• Incidence increasing, possibly as result of
drugs, alcohol, tobacco use of mother before
birth while pregnant
Booklet on ONH from the
Blind Childrens Center in
Los Angeles, CA
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Septo Optic Dysplasia
de Morsier syndrome
• A congenital malformation syndrome manifested by:
- hypoplasia (underdevelopment) of the
optic nerve
- hypopituitarism
- absence of the septum pellucidum (a
midline part of the brain)
• In a severe case, this results in pituitary hormone
deficiencies, blindness, and mental retardation
emedicine.com
• There are milder degrees of each of the three problems,
and some children only have one or two of the three
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Delayed Visual Maturation
Type I: child with normal general/neurological development and
no underlying pathology; by 3-6 months, child has a rapid
improvement of vision to normal or near-normal levels
Type II: associated with systematic disorders of mental retardation;
vision usually improves, but takes longer and there may be
continued loss of vision
Type III: associated with other ocular disorders such as albinism,
cataracts or aniridia; vision worse than expected from
disease alone with mean age of recovery at 20 weeks;
onset of nystagmus precedes recovery which is complete
by 8 months; also depends on visual abilities and other
characteristics of the child
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