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.

Anatomy and Function of the Eye and Ocular Disorders

Part IIDeveloped by SKI-HI Institute

Utah State University

Winter 2011

For use in Training

2

vitreous humor

The Human Eye

retina

macula

fovea

choroid

optic nerveoptic disc

La Clinica Oculistica Virtuale

3

Choroid

• If deprived of its blood supply for more than a few minutes, will die

• Cannot be regenerated

• Nourished by blood vessels thatenter eye near optic nerve and which spread across surface ofretina

• Choroid supplies retina withnourishment

44

Rod and Cone Cells

Rods• More in the peripheral

retina• Detect motion• Function at low

luminance level…night vision

• Gross forms and shadowCones• Color vision• Detail, reading vision

55

Night Vision and Night Blindness

http://www.sapdesiguild.org

6

Prematurity and ROPNational Eye Institute, National Institutes of Health• Factors causing ROP are: excessive

oxygen, prematurity, infection, excessive exposure to light

• 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

7

The Disease Process in ROP

National Eye Institute, National Institutes of Health

• 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

8

Stages of ROPStage 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

9

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

10

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

11

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

12

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

Other Retinal Conditions

• Macular Degeneration• Retinitis Pigmentosa

• Ushers

• Leber’s Amaurosis

• ColobomaCHARGE

• Rubella

• CMV

12

14

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

15

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

16

Other InfectionsToxoplasmosis• 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

17

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

18

Loss of Color Vision Simulated

graphics.cornell.edu

Normal Red

Green Blue(rare)

19

Myopia or near sightedness

Normal vision

eyeatlas.com

20

Hyperopia or far sightedness

Astigmatism

eyeatlas.com

21

Glasses Can’t Fix Every Eye Problem!

Dr. Lea Hyvärinen, Helsinki, Finland

22

Saccades of eye looking at a photo of a face

Artlex.com

Eyes in Constant Motion

• 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 tochanges in color and luminance

• These saccades are so small they are imperceptible to others

• In many children with poor vision, thesemicrosaccades are exaggerated, so

we see them as nystagmus

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

23Dr. Lea Hyvärinen, Helsinki, Finland

24

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

25

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

26

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 usingsuch 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/~edinunder Resources, Vision Module, Session 4, handout I

27

The Visual System

Wps.prenhall.com

28

Normal Optic Nerve

National Eye Institute, National Institutes of Health

macula

optic nerve

29

Hydrocephalus

• Increased fluid in the ventricles or water spaces of the brain

• Put pressure on optic nerve fibers

• Prolonged high pressure causes

permanent damage

• Putting in shunt to drain fluid soon enough can minimize the damage

• Decreased visual functioning can be a

sign of shunt failureOptic nerve head in backof the eye of 2 year old

child with hydrocephaluswww.nature.com/

Child with Shuntwww.mps1disease.com

30

Brain Bleeds Around the Ventricles

• Optic radiations pass by and around the lateral ventricles

• Low birthweight premature babies may suffer brain bleeds in the ventricles

• These bleeds can damage the optic radiations, resulting in vision loss

• Severity of vision loss depends on the extent of the bleed, treatment, other

medical issues, etc.

Lateral Ventricle

Lateral Ventricle(other views)

OpticRadiations

Grade III Bleedin the LateralVentricals

31

Optic Nerve Atrophy (ONA)

• 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

www.nature.com

32

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 theBlind Childrens Center in

Los Angeles, CA

33

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

• There are milder degrees of each of the three problems, and some children only have one or two of the three

emedicine.com

34

Delayed Visual MaturationType 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