NurseReview.Org - Eyes

Eyes

External Anatomy

Sensory Organ for vision

-Situated in bony, orbital cavity for protection

Eyelids= shades that add protection form injury, strong light , dust

Eyelashes= hairs to filter dust & dirt

External Anatomy External Anatomy

Limbus – border b/t the cornea & sclera

Palpebral fissures – elliptical open space b/t lids

Canthus- corners of the eye where the lids meet, inner & outer

Caruncle – sm. Fleshy mass containing sebaceous glands at inner canthus

Within the upper eyelid

Tarsal plates, connective tissue gives upper lid shape

Meibomian glands, in the plates, lubricate the lids, stops overflow of tears, airtight seal when lids closed

Exposed part of the eye

Conjunctiva, folded envelope b/t eyelids & eyeball

thin mucous membrane, transparent protective covering of the exposed part of the eye.

Palpebral conjunctiva lines the lids, is clear but has sm .bld. Vessels

Bulbar conjunctiva is over eyeball, white sclera show through, merges at limbus with cornea

Cornea – clear, covers & protects iris & pupil

Lacrimal apparatus – irrigates conjunctiva & cornea

3 parts

Lacrimal gland, upper, outer corner of eye = tears

Puncta= inner canthus, tear drainage

Nasolacrimal duct= allows tears to drain from puncta to nasolacrimal sac. Tears then empty into the inferior meatus of the nose

Extraoccular muscles

6 muscles

Attach eyeball to orbit

Straight and rotary movement

Four straight muscles

Superior rectus

Inferior rectus

Lateral rectus

Medial rectus

Two slanting/ oblique muscles

Superior

Inferior

Humans have a Binocular, single – image visual system – Eyes normally move as a pair

Eye movement stimulated by Cranial Nerves

III Oculomotor

IV Trochlear

VI Abducens

Internal Anatomy

The eye has 3 layers, the outer & inner layer can be viewed using opthalmascope

Sclera (outer layer) tough, protective, white covering connects with the -

Cornea – transparent, protects pupil & iris – helps focus light on retina

Middle layer

Choroid – dark pigmentation to prevent internal light reflection, supplies bld. to retina

Pupil – PERRLA

Lens – biconvex disc, transparent, thickness controlled by ciliary body, bulges = near; flattens = distant

Anterior chamber – posterior to cornea, anterior to iris & lens, has aqueous humor supplies nutrients & drains wastes

Inner layer – Retina – visual receptive layer – light waves changed to nerve impulses

Retinal structures

Optic disc – retinal fibers meet & form optic nerve, nasal side of retina, creamy yellow orange to pink, round or oval shape, physiologic cup inside the disc for bld.vessels to enter & exit

Retina vessels – paired arteries & veins

Macula – temporal side of fundus, darker pigmented region, surround the fovea centralis

Fovea Centralis- area of sharpest & keenest vision, Very sensitive to light

Visual Pathways & Fields

Objects reflect light

Rays refracted by cornea, aqueous humor, lens, vitreous body and onto retina.

Light stimulus is changed to nerve impulses, travel thru optic nerve to visual cortex in occipital lobe

Image on retina is upside down & reversed. At the optic chiasm retinal fibers cross over. Right side of brain looks at left side of world.

Visual reflexes

Pupillary light reflex – bright light = constriction

Direct light reflex

Consensual light reflex

Fixation – ability to track an object & keep image on the fovea, can be impaired by drugs, alcohol, fatigue & inattention

Accomodation – for near vision = pupil constriction & convergence of eyes

Subjective data

Vision difficulty

Pain

Strabismus, diplopia

Redness, swelling

Watering, discharge

Past history ocular problems

Glaucoma

Glasses/ contacts

Medications

Vision loss- coping mechanisms

Self–care behaviors

Objective data The Physical Exam

Preparation

Position- sitting, head at eye level

Equipment

Snellen eye chart- visual acuity

Handheld visual screener-near vision

Opaque card

Penlight

Applicator stick

Ophthalmoscope

Test visual acuity Snellen eye chart

Stand 20 ft. from chart

Glasses / contacts (Document )

Remove eye wear, retest

Normal visual acuity is 20/20 – top # is distance person is standing from the chart

Vision 20/30 refer to opthalmologist or optometrist

If unable to see largest letters, move to 10 feet – record as 10/200

Test for near vision

Vision screener

People > 40yrs or difficulty reading

Test each eye with glasses

Hold card 14in. from eyes

Normal result 14 / 14

Test using any available reading material if no card available

Presbyopia is a normal physiological change in near vision occurs with aging = note if the person moves the card farther away

Test visual fields Confrontation test

Compares peripheral vision with a tester who has normal peripheral vision

2 ft. apart, eye level

Tester & client cover opposite eyes

Tester advances finger in the periphery

Superiorly ( 50 degrees )

Inferiorly ( 70 degrees )

Temporally ( 90 degrees )

Inspect Extraoccular Muscle Function

Corneal light reflex

Cover test

Diagnostic positions test

6 Cardinal Positions of Gaze

Inspect Extraocular Muscle Function

Corneal Light Reflex ( The Hirschberg Test) assesses parallel eye alignment

Shine light toward person’s eyes

Tell to stare directly ahead

Hold light 12 in. away

Light should reflect on both corneas in same spot

Cover Test- detects deviated alignment

Stare straight at examiner’s nose

Cover 1 eye of the person being examined with opaque card

Normally the uncovered eye should maintain a steady, fixed gaze

Covered eye- should stare straight ahead when covered & then uncovered. If muscle weakness exists the covered eye will relax and then jump to fixed position when uncovered..

Diagnostic Positions Test

6 cardinal positions of gaze –

Determines muscle weakness during movement

Person must hold head steady

Follow movement of object (examiner’s finger, pen etc) only with eyes

Hold object 12 in. from person

Move thru each position, clockwise, hold , then back to center

Normal response= parallel tracking with both eyes

During this test be aware of Nystagmus- fine jerky movement seen around the iris

Mild nystagmus in extreme lateral gaze is normal but not normal in any other position

Inspect External Structures

General – movement & facial expression (squinting?)

Eyebrows – 2(bilateral), symmetrical (look the same; move the same)

Eyelids & Lashes – present, approximate when closed, no redness, swelling, discharge, lesions?

Eyeballs- alignment, ? Protrusion? Sunken?

Conjunctiva & Sclera – moist, glossy, clear, white sclera

Eversion of the upper eyelid FYI – we will not do this examine in lab see pg. 312 for technique – usually done for complaint of eye pain due to foreign body

Lacrimal Apparatus

Person looks down

Using thumbs, slide outer part of upper lid along bony orbit

Note redness or swelling

Press index finger against lacrimal sac at inner canthus

Normal response is slight eversion of lower lid, no tearing or discharge

Anterior Eyeball Structures

Cornea & lens

Iris & pupil

Size & shape

Pupillary light reflex

Accommodation

Cornea & Lens

Shine light from side across cornea

Check smoothness, clarity

Normally no opacities

Iris and Pupil

Iris = flat, round, regular, even color bilaterally.

Pupils = PERRLA

Resting size norm = 3-5mm

5% population have pupils of 2 diff. Sizes called Anisocoria

Pupillary Light Reflex

Darken room

Person gazes straight ahead

Advance light from the side

Direct light reflex

Consensual light reflex

Measure pupil size before & after light reflex

Measurement R3/1 L3/1 =both pupils measure 3mm in resting state & 1mm with light

Accomodation

focus on distant object -dilatation of pupils

Shift gaze to near object – pupils constrict & converge

Record the normal response to these tests as

PERRLA = Pupils Equal, Round, React to Light and Accomodation

Ocular Fundus (internal surface of retina)

Use Opthalmoscope- try keeping both eyes open- practice looking at a ring on your finger. Become familiar with the instrument before you examine your partner’s eyes