CHAPTER 40. Ophthalmological Care
Seema Hussain and Kenneth Wichter
OBJECTIVES
At the conclusion of this chapter, the reader will be able to:
1. Identify the important functions of the eye.
2. Describe the structure of the eye.
3. Describe common ophthalmological surgical procedures.
4. List drugs frequently used for ophthalmological surgical procedures.
5. Identify possible complications of ophthalmological surgery.
6. Describe perianesthesia nursing care for the ophthalmological surgery patient.
I. ANATOMY AND PHYSIOLOGY OF THE EYE (Figure 40-1)
A. Orbit
1. Pyramid-shaped bony cavity that functions as protection for the eye
2. Consists of seven fused bones
a. Ethmoid
b. Sphenoid
c. Frontal
d. Lacrimal
e. Zygomatic
f. Palatine
g. Maxilla
3. Orbit contains
a. Eyeball
b. Six extraocular muscles
c. Ophthalmic artery veins
d. Cranial nerves
(1) The second (optic)
(2) Third (oculomotor)
(3) Fourth (trochlear)
(4) Fifth (trigeminal)
(5) Sixth (abducens)
e. Lacrimal gland
f. Lacrimal sac
g. Orbital fascia, fat and ligaments
B. Eyelids are continuous with the conjunctiva lining the inner aspect of the lid
1. Act as protection for
a. Anterior portion of the eyes
b. Epithelium of the lids
2. Spread lubricating solutions over globe
a. Keep eyes moist
b. Prevent evaporation of secretion
3. Eyelashes situated along the margins and act as protective fibers
4. Two muscle groups
a. Orbicularis oculi sphincter responsible for closing eye
b. Levator palpebrae responsible for raising eyelids
c. Movements can be both involuntary and voluntary.
5. Function of the eyelids
a. Cover eyes during sleep
b. Protect eyes from excessive light
c. Protect eye from injury
d. Protect eye from foreign objects
e. Lubricate the anterior surface of the eye
6. Lined with mucous membrane called palpebral conjunctiva
C. Conjunctiva
1. Thin, transparent mucous membrane covering sclera and inner lids
2. Lining upper and lower eyelids—palpebral conjunctiva
3. Extends over sclera to corneal margin—bulbar conjunctiva
4. Function of the conjunctiva
a. Produces the mucin layer of the tear film, reducing the rate of tear evaporation
b. Protects the eye against damage and infection
c. Facilitates movement by moistening the surface of the eye and lids
D. Lacrimal apparatus: produces and drains tears
1. Consists of:
a. Lacrimal gland—located in upper outer aspect of each orbit and produces tears that:
(1) Empty through lacrimal ducts onto conjunctiva of upper lid
(2) Spread across eyeball by blinking
(3) Enter lacrimal puncta
b. Lacrimal puncta—two small openings located in the inner canthus of each upper and lower eyelid
(1) Pass into lacrimal canals, lacrimal sac, nasolacrimal duct, and finally into inferior meatus of the turbinate bone of the nose
c. Lacrimal sac—collects tears
d. Nasolacrimal duct—drains tears from lacrimal sac to nose
2. Tears
a. Contains
(1) Water
(2) Protein
(3) Glucose
(4) Sodium
(5) Potassium
(6) Chloride
(7) Urea
(8) Lysozyme (bacterial enzyme)
b. Purpose of tears
(1) Aid refraction by providing an optically smooth corneal surface
(2) Lubricate the anterior surface of the eye to aid movement
(3) Clean dust particles from the eye
(4) Protect against infection by the action of lysozymes
c. Emotional stimulus of parasympathetic nervous system triggered
E. Muscles controlling the eye (Figure 40-2)
1. Extraocular muscles (six)
a. Attached to outside of eyeball and to bones of the orbit
b. Consist of voluntary skeletal muscle
(1) Four rectus
(a) Superior—oculomotor nerve
(b) Inferior—oculomotor nerve
(c) Medial—oculomotor nerve
(d) Lateral—abducens nerve
(2) Two oblique muscles
(a) Superior—trochlear nerve
(b) Inferior—oculomotor nerve
c. Action
(1) Muscles move eyeball through cranial nerves.
(a) Third (oculomotor)—moves eyeball and upper eyelid
(b) Size of iris (i.e., constriction and dilation of pupil to regulate amount of light admitted)
(c) Control of ciliary muscle to regulate degree of refraction by lens
(d) Fourth (trochlear)—movement of eyeball by superior oblique muscles
(e) Sixth (abducens)—movement of eyeball by lateral rectus muscle
(2) Muscles work in pairs.
(3) Movement caused by:
(a) Increase in tone of one set of muscles
(b) Decrease in tone of antagonistic (opposite set) muscles
2. Movement of upper eyelid
a. Raised (opened) by levator palpebrae superioris muscle
(1) Controlled by cranial nerve III and sympathetic nervous system
b. Closed by orbicularis oculi muscle
(1) Controlled by cranial nerve VII
3. Iris and ciliary muscles
a. Smooth, involuntary muscles
b. Work inside eyeball
(1) Regulate size of pupil
(2) Control shape of lens during accommodation
(3) Controlled through neural network
(a) Optic nerve (cranial nerve II)
(b) Oculomotor nerve (cranial nerve III)
 |
| FIGURE 40-2 ▪
The six cardinal directions of gaze and the muscles responsible for each. The six cardinal directions are (1) right, (2) left, (3) up and right, (4) up and left, (5) down and right, and (6) down and left.
(From Black JM, Matassarin-Jacobs E: Medical-surgical nursing clinical management for continuity of care, ed 5, Philadelphia, 1997, WB Saunders, p 936.)
|
 |
| FIGURE 40-1 ▪
Structure of the eyeball.
(From Drain CB, ed: Perianesthesia nursing: A critical care approach, ed 4, St Louis, 2003, WB Saunders, p 453.)
|
F. Globe (eyeball): supported in orbital cavity on a cushion of fat and fascia; composed of three layers
1. External, corneal-scleral layer (fibrous, protects other two layers)
a. Cornea
(1) Anterior, transparent, avascular part of the external layer
(2) Serves as a window through which light rays pass to retina
(3) Supplied by branches of ophthalmic division of fifth cranial nerve
(4) Composed of five layers
(a) Epithelium
(i) Cell layers and nerve endings
(ii) Account for corneal sensitivity
(b) Bowman’s membrane
(i) Composed of connective tissue fibers
(ii) Forms a barrier between trauma and infection
(iii) Does not regenerate if damaged
(iv) Will leave a permanent scar
(c) Stroma
(i) Accounts for 90% of corneal thickening
(ii) Composed of multiple lamellar fibers
(d) Descemet’s membrane
(i) Thin layer between endothelial layer of cornea and substantia propria (fibrous, tough, and transparent main part of the cornea)
(ii) If inflamed, called descemetitis
(iii) If protrudes, called descemetocele
(e) Endothelium
(i) Single layer of hexagonal cells
(ii) Does not regenerate
(iii) Responsible for proper state of dehydration that keeps cornea clear
(iv) Damage causes corneal edema and loss of transparency.
b. Sclera: posterior opaque part of the external layer; tough white outer coat of eyeball
(1) Portion of sclera can be seen through the conjunctiva as the white of the eye.
(2) Made up of collagenous fibers loosely connected with fascia, which receives the tendons of the muscles of the globe
2. Middle layer: middle covering of the eye comprises the choroid, ciliary body, and iris (referred to as uveal tract).
a. Choroid
(1) Most posterior portion of middle coat
(2) Contains many blood vessels; highly vascular
(3) Deeply pigmented
(4) Purpose
(a) Absorbs light rays
(b) Prevents reflection within eyeball
(c) Main source of nourishment to retina (through its blood supply)
b. Ciliary body
(1) Consists of an extension of the choroidal blood vessels, a mass of muscle tissue, and an extension of the neuroepithelium of the retina
(2) Composed of ciliary muscle and ciliary processes
(3) Ciliary muscle
(a) Affects accommodation
(b) Alters shape of lens as needed to focus light rays from near or distant objects on retina
(4) Ciliary processes
(a) Produce aqueous humor
c. Iris
(1) Colored area of eye
(2) Anterior portion of the middle layer
(a) Thin membrane situated in front of the lens
(3) Peripheral border attached to ciliary body
(4) Central border is free.
(5) Divides the space between the cornea and the lens
(a) Anterior and posterior chambers
(b) Chambers filled with aqueous humor
(6) Regulates the amount of light entering the eye
(a) Muscles contract and relax.
(b) Changes size of opening in center (pupil)
(c) Assists in obtaining clear images
3. Internal layer: innermost layer of neural coat (retina)
a. Retina
(1) A thin transparent membrane extending from the ora serrata to the optic disc
(2) Consists of network of nerve cells and fibers
(a) Receives images of external objects
(b) Transfers the impressions to the occipital lobe of cerebrum via
(i) Optic nerve
(ii) Optic tracts
(iii) Lateral geniculate body
(iv) Optic radiations
(c) Nerve fibers from retina converge to become optic nerve.
(i) Point at which optic nerve enters eyeball called optic disc (anatomic blind spot)
(3) Covers choroid
(4) Found only in back of eye
b. Retina composed of layers
(1) Outer pigment
(a) Stores vitamin A; needed to produce photopigment rhodopsin
(2) Inner neural
(a) Consists of photoreceptor cells (rods and cones)
(i) Visual receptors that develop generator potentials
(ii) Relays sensory information to ganglion cells of retina
(b) Rods
(i) Located in peripheral retina
(ii) Allow for vision in dim light
(iii) Responsible for perception of different shades of light and dark, shapes, and movement
(c) Cones
(i) Stimulated by bright light only
(ii) Responsible for color vision and visual acuity
G. Refractive apparatus (cornea, aqueous humor, lens, and vitreous body)
1. Cornea
a. Has greatest refractive power of the ocular structures
b. Variations in curvature of cornea change its refractive power.
2. Aqueous humor
a. Fluid responsible for maintaining intraocular pressure
b. Produced by ciliary processes
c. Secreted by ciliary body into posterior chamber
d. Flows from posterior chamber through pupil into anterior chamber
e. Flows into anterior chamber angle and is filtered out through the trabecular meshwork into Schlemm’s canal
f. Channeled into capillary network and into episcleral veins
g. Maintenance of normal intraocular pressure
(1) Occurs as long as there is a balance between:
(a) Aqueous production
(b) Aqueous humor outflow
3. Lens
a. Suspended behind the iris
b. Anterior and posterior surfaces separated by rounded border
c. Does not shed cells; as it grows, the cells compress and harden.
d. Lens expands and retracts through zonular fibers (accommodation).
e. Accommodation power lost with aging process
f. Hardening eventually causes opacity of lens (cataract).
4. Vitreous body
a. Glasslike transparent gelatinous mass (vitreous humor)
b. Composed of 99% water and 1% collagen and hyaluronic acid
c. Fills the posterior four fifths of the eyeball
d. Supports the posterior cavity
e. Keeps the retina in place
H. Nerve and blood supply
1. Optic nerve (second cranial nerve)
a. Extends between posterior eyeball and optic chiasma
b. Carries visual impulses and sensations of pain, touch, temperature from eye to brain
2. Muscle innervation
a. Oculomotor (third cranial nerve): primary motor nerve to all rectus muscles (except lateral rectus)
b. Abducens (sixth cranial nerve) innervates lateral rectus.
c. Trochlear (fourth cranial nerve) innervates superior oblique muscle.
3. Ophthalmic artery
a. Main arterial supply to orbit and globe
b. Branch of internal carotid artery
II. COMMON OPHTHALMIC SURGICAL PROCEDURES
A. Blepharoplasty—repair of the upper or lower eyelids to remove redundant skin; may be cosmetic or therapeutic when the eyelid interferes with vision
1. Types
a. Upper blepharoplasty (upper eyelid only)
b. Lower blepharoplasty (lower eyelid only)
c. Quadrilateral blepharoplasty (involving all four eyelids)
2. Preoperative considerations
a. Patient may be examined by ophthalmologist before procedure to rule out ocular symptomatology.
3. Surgical procedure
a. Excess skin and muscle resected; periorbital fat trimmed
b. Requires meticulous hemostasis
c. Closed using fine nonabsorbable or absorbable sutures
4. Postoperative considerations
a. Iced saline dressings applied immediately to control edema
B. Removal of chalazion—granulomatous inflammation of a meibomian gland in eyelid, frequently caused by Staphylococcus aureus
1. Surgical procedure
a. Surgical incision and curettage
b. Most commonly done under local anesthesia in physician’s office
c. Occasionally requires operating room (OR) setting
C. Repair of entropion
1. Entropion
a. Eyelid margins turn in, especially the lower lid
b. Caused by spasm of the orbicularis oculi muscle
c. Scarring of the conjunctiva
d. Lashes scrape across cornea with each eye blink, which is painful and results in
(1) Corneal abrasions
(2) Scarring
(3) Ulcer
2. Surgical procedure
a. Surgical removal of excision of skin and/or muscle and/or the tarsal plate
(1) Correction of the muscular fibers of the lid, everting the lid margins and eyelashes
(2) Performed under local or general anesthesia
b. Cryotherapy—may be used to freeze and remove lashes, which destroys lash follicle and prevents regrowth of lashes
(1) Preferred method of treatment
D. Repair of ectropion
1. Ectropion—outward turning or eversion of eyelid, usually bilateral
a. Caused by:
(1) Relaxation of orbicularis oculi muscle
(2) Scarring of the face near the eye
(3) Normal aging process
(4) Bell’s palsy
(5) Exposure of underlying conjunctiva
(6) Congenital
b. Can lead to keratitis (inflammation or infection of the cornea)
2. Surgical procedure
a. Shortening of lower lid in a horizontal direction
b. Mild case can be treated with deep electrocautery 4 to 5 mm from the lid margins.
(1) Resulting scar formation will draw lid to its normal position.
c. Lateral tarsal strip procedure—lateral canthal tightening
(1) Preferred method of treatment
(2) Performed under local anesthesia
d. Upper lid gold weight implantation for paralytic ectropion
E. Ptosis
1. Drooping of the upper eyelid; can affect one or both eyes; caused by weakness of levator muscle, or less frequently, Muller’s muscle
2. Three types of ptosis
a. Congenital—caused by failure of levator muscle to develop, weakness of superior rectal muscles
b. Acquired—associated with loss of superior visual field in primary gaze
(1) Causes
(a) Mechanical failure—weight of eyelid neoplasms
(b) Trauma—caused by laceration of third cranial nerve, the levator, or both
(c) Myogenic, by disease—muscular dystrophy
(d) Neurological disorders—myasthenia gravis
(e) May be caused by a tumor
(f) Aponeurotic ptosis—senescence, dehiscence, or chronic inflammation
(2) Treatment based on cause and severity
c. Senile
3. Surgical procedure
a. Objective is to create a good upper lid fold with elevation of the lid.
b. Surgical procedures based on advancement of
(1) Levator muscle
(2) Frontalis muscle
(3) Superior rectus muscle
F. Excision of pterygium
1. Thick triangular growth of epithelial tissue
a. Extends from corner of cornea to the inner canthus
b. Appearances may be pale or white.
c. May grow over the pupillary opening
d. Cause thought to be exposure to constant irritant such as
(1) Wind
(2) Dust, including sand
(3) Ultraviolet light
2. Surgical procedure
a. Growth dissected off the cornea and conjunctiva down to the sclera
b. Low-dose radiation on surgical wound may be used to prevent regrowth.
(1) Regrowth rate 20% to 40%
G. Lacrimal duct disorders
1. Dacryocystorhinostomy (DCR)—establishment of a new tear passageway for drainage directly into the nasal cavity
a. Dacryocystitis is an infection in the lacrimal sac and its mucous membranes that extends to the surrounding connective tissue, resulting in localized cellulitis.
Buy Membership for Anesthesiology Category to continue reading. Learn more here
