disorder of the eyes

Resident’s TutorialDisorder of the eyes I

Piti Niyomsirivanich ,MD.

•Episode IThe Human visual systemClinical Assessment of Visual Function

Outline

• Episode I– The Human visual system– Clinical Assessment of Visual Function

• Episode II– Disorders– Transient or sudden visual loss– Diplopia

Take home message

• Retinogeniculatecortex pathway– RetinaOptic nerveOptic chiasmOptic tractLateral

geniculate bodyPrimary visual cortex• Pupils response pathway

– Retina (ganglion cells)Optic nerveOptic chiasmOptic tractPretectal Olivary NucleiEdinger-Wesphal NucleiCN IIICiliary GanglionCiliary muscle

• Refractory defect : pinhole : Rx glasses , LASIK• VA : snellen chart ,rosenbaum card , FC HM LP • color blindness : Ishihara color plate :red,green• Stereopsis : Random dot stereogram , polarized image• Visual field : RetinaOptic nerveOptic chiasmOptic

tractLateral geniculate bodyPrimary visual cortex

Take home message

Human visual system

• Retina– Part of brain– Serve as transducer– Two type of receptor

• Rod scotopic (dim)• Cone photopic (day)

– Cone Fovea (exclusively)

Rod Cell

Cone Cell

Amacrine Cell

Horizontal Cell

Ganglion Cell

Optic disc Optic nerve

Optic nerve

Retinogeniculatecortex pathway

Optic Chiasm

Optic Tract

Lateral geniculate bodysynapseRelay station

Primary visual cortex

RetinaOptic nerveOptic chiasmOptic tract

Lateral geniculate body(Synapse , relay station)

Primary visual cortex

Rod , coneAmacrine Horizontal cell

Ganglion cell

Pupil responseRetina (ganglion cell)Optic nerveOptic chiasmOptic tract

ไม่�ผ่�าน Lateral geniculate body

Pupil responseRetina (ganglion cells)Optic nerveOptic chiasmOptic tract

Pretectal Olivary NucleiSynapse

Edinger-Wesphal Nuclei Synapse

CN III

Pupil responseRetina (ganglion cells)Optic nerveOptic chiasmOptic tractPretectal Olivary Nuclei

SynapseEdinger-Wesphal Nuclei SynapseCN IIICiliary Ganglion

Pupil responseRetina (ganglion cells)Optic nerveOptic chiasmOptic tractPretectal Olivary Nuclei

SynapseEdinger-Wesphal Nuclei SynapseCN IIICiliary GanglionCiliary muscle

Clinical Assessment of Visual Function

Refractory State

Emmetropia

Myopia

Hyperopia

Astigmatism

Presbyopia

• Middle age

• Unable to increase refractory power to accomodation

• Reading glasses / Bifocal

• Refractory Errors– Develop slowly stable adolescence

• Diabetes mellitus Sudden myopia – Hyperglycemia induced corneal edema

Testing

• Pinhole aperture– Better through a pinhole refractory error

Treatment• LASIK

• glasses

Refractory State

Visual acuity

Snellen chart

• Distance 6 m (20 ft)

• Rosenbaum card (36 cm) (14 in)

• Distance 36 cm – (14 inches)

• Normal 20/20

• VA < 6/240– Finger counts– Hand motion – Light perception

Rosenbaum card

Refractory State

Visual acuity

Pupils

• Should be test in dim light

• Fixing on a distant target

Light response

Near response

No need to test‘near response’

Normal Light-Near dissociation

•Argyll Roberson pupil (neurosyphilis)•Pineal region tumors•Obstructive hydrocephalus•Adies’s tonic pupil

• No light pupillary response Marcus Gunn pupil

http://www.youtube.com/watch?v=IcrXmeCI08w

Anisocoria

• Anisocoria (asymetrical pupil up to 0.5 mm)

normal person constant as ambient varies

• DDX– Horner’s syndrome– Brainstem stroke – Carotid dissection

• Mydriasis (Acute pupil dilatation)– Infection (Herpes zoster, influenza)– Trauma (blunt, penetrating, surgical)– Ischemia (diabetes , temperal arteritis)

• Tonic pupil ==> เอาไฟฉายออก แล้�วม่�านตาขยายช้�าล้ง– Adie’s syndrome (Tonic pupil + absent DTR)– Shy-Dragger syndrome (PD + MSA)– Diabetes , amyloidosis , segmental hypohidrosis

Bilateral pupils abnormal

• Miosis– Medications (Narcotics: Morphine, Heroine)– Parasympathetics agents (pilocarpine ,demecarium

bromide)

• Mydriasis– Anticholinergic (Scopolamine)

• Unexplained abnormality Slit lamp examination– Trauma,FB adhesions , close angle glaucoma ,

intraocula inflammation

Refractory StateVisual acuity

PupilsEye movements And Alignment

Eye Movements and Alignment

• Corneal light reflex

• Cover Test

http://www.youtube.com/watch?v=yyIA-dl49Lg

Stereopsis

Two eyes = 3D

Stereopsis test

Polarized imageRandom dot stereogram

Color vision

• Three classes of cones – Red (560 nm) X chromosome– Green (530 nm) X chromosome– Blue (430 nm) chromosome 7 rare

• Shift in peak spectral sensitivityAltering the proportion of primary colorColor mismatchdiscrimation between 2 color are impaired• Ishihara color plate (red-green color blindness)

• Acquired color blindness– Bilateral stroke involving the ventral portion of

occipital lobe (cerebral achromatopsia) perceive only gray shadesdifficulty recognizing faces (prosopagnosia)

Visual fields

• Mapping– Visual confronation– Quantitative visual

field mapping

Visual field defect

Macula damage

GlaucomaOptic neuritis

(destroy axon of optic disc)

Turkish scimitar

Ischemic optic neuropathy

Horizontalmeridian

Optic neuritisToxic metabolicnutrition

macula

Next episode

Thankyou

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