CLINICAL PERSPECTIVESSTRUCTURES AROUND THE GLOBE

Orbit- provides a safe place for the eyeballeyelids- closes light off of eye, protects, distributes tearstears- lubricates & protectslacrimal system- distributes tearsconjunctiva- covers sclera and inner surface of eyelidsorbital septum- bone covering top of orbiteyebrow- covers orbital septum, protects eye from sweat

• Photos courtesy of the National Eye Institute

• NEI@nih.gov

Extraocular Muscles

• Superior & Inferior Recti

• Medial & Lateral Recti

• Superior & Inferior Obliques

Eyelids & eyelashes

• meibomian glands- oil glands

Conjunctiva

• sclera- white fibrous covering of eyeball

• 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

• 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

• 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

•

• 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– 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