Eye care basicsand optical options

Rick Smith &

Sam Powdrill

Eye Anatomy

Visual Image

Components of Vision

The External Eye

The Skull

Bones of the Orbit

• Frontal• Zygoma• Ethmoid• Maxilla• Sphenoid

The Lacrimal System

The tear film

• Lipid layer• Aqueous layer• Mucus layer

The Eyelids

Vessels and

Musclesof the Eyelids

Extrinsic Eye Muscles

Extrinsic muscles with innervation

The Globe

• Anterior chamber aqueous

• Iris

• Lens

• Posterior chamber vitreous

• Optic nerve

Layers of the eye

• Protective

• Vascular

• Visual

Protective Layer

• Sclera

• Cornea

Vascular layer

• Iris

• Ciliary body

• Choroid

Angle of the Eye

Visual Layer

• The retina

• Optic nerve

Central Retina

Optic Nerve (II) Visual pathway

Optic Nerve (II) – Visual pathway

Refraction

Prism

Converging

diverging

Lens Power

• Measured in diopters• One diopter lens focuses at 1 meter Lens power = 100 cm focal length focal length = 100 cm Lens power

Refractive errors

• Nearsighted – myopia

• Farsighted – hyperopia

• Astigmatism

• Presbyopia

Refraction

• Convex lens

• Concave lens

• Accommodation

• Refractive error

Correction of Refractive Errors

• Pinhole

• Myopia

• Hypermetropia

• Astigmatism

Exam of the Eye

Pathways of Blindness

• Corneal• Anterior chamber• Lens• Vitreous• Retina • Optic nerve• Occipital• Functional

Instruments needed to examine the eye

1. Visual acuity chart2. Flashlight3. Ophthalmoscope4. Tonometer5. Simple loupe

Measure Visual acuity

The vital sign of the eye• Distance vision

• Near vision

• Peripheral vision

• Central vision

• Color vision

Snellen charts

Pinhole

eliminates the

refractive error

Visual acuity

• Cover the eye with the palm of the hand

• Test the eyes separately then together

• Point to the letters clearly

• Use a random sequence

Recording Visual acuity

20/20Upper number = distance in feet from the

patient to the chart

Lower number = distance in feet at which a person with excellent visionwould see the same letter

Examples

• 20/40• 20 /400• 20/15• 10/50• CF 10ft• HM• LP• NLP

Central vision

• Test for loss of central vision - macula

• Amsler grid

• Abnormal in macular degeneration

Amsler grid

Color vision

• Check for red / green color blindness• Ishihara chart

• Color comparison method with a red object

• Color blindness is an X linked genetic disorder that most often affects males.

Ishihara chart

Tonometry

• Schiotz• Applanation • Air puff• tonopen

Normal is

10 to 20 mmHg

Extraocular Muscles

• Six Cardinal eye movements• Corneal light reflex position• Nystagmus• Cover - uncover test• Convergence

Peripheral vision

Testing the visual field• Confrontation method – compares the

examiner’s visual field with the patient’s

• Automated – done in optometrist’s or ophthalmologist’s office

• Abnormal in glaucoma

Visual fields by confrontation

Eyelids

Inspect • Symmetry – skin creases• Opening and closing completely• Eyelash position• Ptosis• Tremor or fasciculations • Swelling or infection• Flakiness

cataract

• Ophthlmoscope set on +4

• Shadows against Red reflex

Direct light vs Coaxial light on the lens

Eyelids

Palpate • Eyelids for nodules• Intraocular pressure

Evert upper and lower lids and inspect • Color • Discharge• Lacrimal system

Conjunctiva and Sclera

Inspect • Redness• Vessels• Growths or lesions, foreign bodies• Proptosis• enophthalmos

Cornea

Inspect• Clarity – scars obscure part of the iris.• Light reflex – reflex is scattered in edema• Corneal sensitivity• Arcus• Depth of anterior chamber – iris shadow• Abrasions or foreign bodies – use fluorescein stain

with blue light to examine the cornea for defects

Iris and pupilInspect Iris

• Color• Angle• lesions

Inspect Pupil • Size• Shape • Reaction to light• Reaction to near • Consensual response• PERRLA

Ophthalmoscope examLens clarity – lens opacity is a cataractRed reflex – ophthlmoscope set on + 4Vitreous clarity – floaters, sclerotic bandsRetinal color and backgroundRetinal vessels – hemhorrage, cotton wool spots,

AV nicking, neovascularization, Optic disc – cup/disc ratioOptic nerve head – papilledema, cupping or

atrophyMacula for drusen or changes

Retina

Retina