Eyes By Orest Kornetsky. Eye Anatomy – Why Study It?

Eyes

By Orest Kornetsky

Eye Anatomy – Why Study It?

Why should you care?

Optometrist – Doctor of optometry, 4 year undergrad + 4 year optometry school

Ophthalmologists – Medical doctors In general, optometrists practice primary

and preventive eye care, while ophthalmologists perform eye surgery

What do nurses do?

History

Vision difficulty? Halos around lights – in glaucoma Scotoma – blind spot in visual field – in

glaucoma, optic nerve, and visual pathway disorder

Night blindness – Vit A deficiency, glaucoma,

Eye pain? Photophobia – inability to tolerate light

Childhood strabismus? A history of crossed eyes? AKA “lazy eye”

Redness or swelling? Infections?

History cont.

Excessive or lack of tearing? May be due to irritants or obstruction in drainage

Past history of ocular problems? Glaucoma? Family history? Use of glasses or contact lenses? When tested last? Any medications?

Anatomy of Eyelid

Eyelids (L. palpebrae) protect the cornea and eyeball from injury

Canthi (sing. canthus) are corners of the eye, also called angles of eye

Caruncle is located near medial canthus and contains sebaceous glands

Tarsal plates are made of connective tissue and strengthen eyelid. They contain meibomian (tarsal) glands which secrete lipid to create airtight seal when closed and also prevent eyelids from sticking together

Inspecting External Ocular Structures General

Note if facial expression is relax or tense

Eyebrows Note if movement is symmetrical

Eyelids and lashes Note if any redness, swelling,

discharge or lesions Note if eyelid closes completely and if

drooping Pallor of lower lid is good indicator of

anemia For upper eyelid, use applicator stick

to fold the eyelid over (Fig 14-17)

Abnormalities in Eyelids

Ectropion Lower lid rolls out, causing an

increase in tearing The eyes feel dry and itchy due to

inappropriate itching Increase risk for inflammation Occurs mostly in elderly due to

atrophy of elastic tissue

Entropion The lower lid rolls in Foreign body sensation

Abnormalities in Eyelids

Periorbital edema May occur with local

infection of systemic condition (CHF)

Ptosis Occurs with

neuromuscular weakness (myasthenia gravis) or CN III damage

Lesions on the Eyelids

Blepharitis Inflammation of eyelids Staph or dermatitis Burning, itching, tearing,

foreign body sensation, pain

Chalazion A cyst in or an infection of

meibomian gland Nontender, firm, overlying

skin freely movable

Hordeolum (Stye) Localized Staph infection of

hair follicle at lid margin Painful, red, swollen, purulent

Anatomy of the Eye Lacrimal apparatus

provides irrigation of conjunctiva Lacrimal glands – secrete

lacrimal fluid (tears) Lacrimal ducts – lacrimal

fluid to conjunctiva Lacrimal canaliculi

(puncti) – drain fluid into Nasolacrimal duct –

conveys lacrimal fluid to nasal cavity

Inspecting the Lacrimal Apparatus

Inspect for bulges or pressure near canaliculi

Dacryocystitis Inflammation of the

lacrimal sac and/or nasolacrimal duct

Dacryoadenitis Infection of lacrimal

gland

DacryocystitisDacryoadenitis

Anatomy of Extraocular Muscles 4 rectus (straight) 2 oblique Innervations

SO4 – Superior oblique m. CN IV (trochlear n.)

LR6 – Lateral rectus m. CN VI (abducens n.)

AO3 – All other muscles CN III ( Trigeminal n.)

Extraocular muscle movement

Extraocular Muscle Dysfunction

Anatomy of the Eyeball – Outer Layer

Sclera – tough protective white covering (posterior 5/6)

Cornea – transparent part of the fibrous coat covering the anterior of the eyeball (anterior 1/5)

Conjunctiva – transparent protective covering of exposed part of eye (palpebral conjunctiva covers inside of eyelash)

Corneal reflex – lightly touching the eye with cotton stimulates a blink.

Trigeminal n. (afferent) Facial n. (efferent)

iris

Inspection

Conjunctiva Sliding the lower lids down, observe

for redness on conjunctiva and if eyeball looks moist and glossy

Reddening may be pathogenic Sclera

Should be white, although may have gray-blue hue

Might contain yellowish fatty deposits beneath the lids

Yellowing of sclera indicates jaundice

Vascular Disorders of Eye

Conjunctivitis “Pink eye” Due to bacterial, viral, allergic, or chemical

irritation Redness throughout the conjunctiva, but

usually clear around the iris Purulent discharge usually common Symptoms: itching, burning, foreign body

sensation Iritis

Red halo around the iris and cornea Pupils may be irregular due to swelling Symptoms: photophobia, blurred vision,

throbbing pain

Inspecting Cornea and Lens

Corneal abrasion Assess by shining a light

and observing from the side

Pupillary light reflex Charted according to size

of pupil Charted as a ratio of before

light/after light (3/1) A sluggish response may

be caused by increased ICP

No response may indicate neurological damage

PERRLA:Pupils Equal, Round,React to Light and Accommodation

How to chart pupillary light reflex?

Anatomy of the Eyeball – Middle Layer

Choroid – provides vascularity to retina

Pupil – variable-sized, black circular or slit shaped opening in the center of the iris that regulates the amount of light that enters the eye. Appears black because most of the light entering the pupil is absorbed by the tissues inside the eye.

Lens – biconvex disc controlled by the ciliary muscle to produce far vision when flat

Anterior chamber Aqueous humor is produced by the

ciliary body and secreted into posterior chamber of eye.

From there, aqueous humor travels to the anterior chamber where it exits through the Canal of Schlemm

Determines intraocular pressure

Canal of Schlemm

Increase leads toGlaucoma

Vascular Disorders of Eye

Glaucoma Excessive pressure in eye

due to blockage of outflow from anterior chamber

This puts pressure on optic nerve

Redness around the iris, dilated pupils

Symptoms: sudden clouding of vision, sudden eye pain, and halos around lights

Physiology review:Aqueous humor is produced by the ciliary bodyand secreted into posterior chamber of eye. From there, aqueous humor travels to the anterior chamber where it exits through the Canal of Schlemm

Disorders of Opacity of Lens

Cataract

Anatomy of the Eyeball – Inner Layer Retina – visually

receptive layer where light waves are changed to nerve impulses

Optic disc – area where the optic nerve enters the eyeball

Fovea centralis – area of most acute vision

Inspecting the Ocular Fundus

Using an ophthalmoscope to inspect the internal surface of the retina, anterior chamber, lens, and vitreous.

Darken the room to dilate the pupils Remove eye glasses, contacts may

stay in Ask person to stare at distant object Hold ophthalmoscope close to your

eye and move to within a few inches of the person’s face

A red glow filling the pupil is called the red reflex and is caused by light reflecting off the retina Cataracts appear as opaque black

areas against the red reflex

Inspecting the Optic Disc and Retina

Normal optic disc is: Yellow-orange to pink Round or oval Distinct margins

Normal retina is: Arteries in each

quadrant Arteries are bright red

Visual pathways

Testing Visual Reflexes Pupillary light reflex

Constriction of pupils when bright light shines on the retina Direct light reflex – constriction of same sided pupil Consensual light reflex – simultaneous constriction of both

pupils The impulse is carried afferently by CN II and efferently by CN III

Accommodation Adaptation of eye for near vision Ask person to focus on distant object (dilates the pupils). Then

ask person to shift gaze to near object few inches away. A normal response is pupillary constriction and convergence of axes of the eyes

Testing Visual Accuity

Snellen Eye Chart Standing 20 feet from the

chart Test one eye at a time by

covering the other eye Leave contact lenses and

glasses on, unless the glasses are reading glasses

Normal vision is 20/20 Near vision

Use Jaeger card (smaller version of Snellen chart) or just read newspaper

Testing Visual Fields Confrontation test

Measures peripheral vision compared to examiner (assuming examiner’s vision is normal)

Both examiner and pt cover one eye with a card, stand about 2 feet away, and maintain eye contact

Advance finger, starting from periphery, and ask patient to say “now” when the finger is first visible

Inability to see when the examiner sees suggests peripheral field loss

Testing Ocular Muscle Function

Cover Test Detects deviated alignment of eyes Ask pt. to stare straight at your nose and

cover one of the pt.’s eyes with a card While noting the uncovered eye, move

away the card A normal response is a steady fixed gaze

Diagnostic Position Test Ask pt. to hold head straight and move

finger in all positions, holding it about 12 inches away

A normal response is parallel tracking of the objects with both eyes

Nystagmus Fine oscillating movements around the iris Normal at extreme lateral gaze

Developmental Considerations – Infants and Children

Strabismus – must be detected and treated early to prevent permanent disability Esotropia – inward turning of eye Exotropia – outward turning of eye

Color vision – due to inherited X-linked recessive trait, occurs more often in boys

External eye structures – an upward lateral slope together with epicanthal folds occurs in Down syndrome

Ophthalmia neonatum – conjunctivitis due to bacteria, virus, or chemical irritation

Developmental Considerations – Aging Decrease in visual

acuity, diminished peripheral vision

Ectropion (drooping of lower lid) or entropion (eyelids turning in)

Pinguecula – yellow nodules due to thickening of conjunctiva as a result of prolonged exposure to sun, wind, and dust

Developmental Considerations - Aging Arcus senilis – gray-

white arc seen around the cornea. Due to deposition of lipids. No effect on vision

Xanthelasma – raised yellow plaques. Normal

THE END

EYE HOPE YOU HAVE A GREAT DAY!!!