Download 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
1
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
2
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
3
Night Vision and Night Blindness
http://www.sapdesiguild.org
4
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
5
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
6
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
7
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
8
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
9
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
10
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
11
Other Retinal Conditions
• Macular Degeneration
• Retinitis Pigmentosa
• Ushers
• Leber’s Amaurosis
• Coloboma
CHARGE
• Rubella
• CMV
12
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
13
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
14
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
15
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
16
Loss of Color Vision Simulated
Normal
Red
Blue
(rare)
Green
graphics.cornell.edu
17
Normal vision
Myopia or near sightedness
eyeatlas.com
19
Hyperopia or far sightedness
Astigmatism
eyeatlas.com
20
Glasses Can’t Fix Every Eye Problem!
Dr. Lea Hyvärinen, Helsinki, Finland
21
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
21
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
23
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
23
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
24
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
25
The Visual System
Wps.prenhall.com
26
Normal Optic Nerve
optic nerve
macula
National Eye Institute, National Institutes of Health
27
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/
28
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
29
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
30
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
31
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
32
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
33