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goal of ophthalmologic surgery
restore vision lost as a result of disease, injury or congenital defect
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7 bones that come together to form the orbit
- frontal
- lacrimal
- sphenoid
- ethmoid
- maxillary
- zygomatic
- palatine
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where does optic nerve enter?
posterior orbital cavity through optic foramen
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what are eyelids composed of?
fibrous connective tissue (tarsal plate)
-
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space or interval between upper and lower lids
palpebral fissure
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juncture of eyelids
canthus
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secrete waxy oil that seals eyelids when closed
sebaceous glands located along lid margin and in lacrimal caruncle
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what do eyelashes do?
protect eye from airborne particles
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2 spaces of anterior cavity of globe
anterior and posterior chambers
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how many muscles attach sclera to bony orbit?
6
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4 rectus muscles
- superior
- inferior
- lateral
- medial
-
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vision is normally...
binocular
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what does visible area consist of?
central and peripheral vision
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thin, transparent mucous membrane that lines each eyelid and covers sclera
conjunctiva
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regions of conjunctiva
palpebral and bulbar regions
-
part of conjunctiva that is highly vascular and pink, lines eyelids and extends over cornea
palpebral conjunctiva
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part of conjunctiva that covers anterior portion of eyeball up to junction of sclera and appears white
bulbar conjunctiva
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clear tissue layer overlying the front of eyeball
cornea
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3 tissue layers of cornea
- epithelium
- stroma
- endothelium
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where does refraction take place?
in the cornea
-
where do the tissues of the cornea come together?
limbus
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initial incision of cataract surgery
at the limbus
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thick, white, fibrous tissue that encloses about 3/4 eyeball
sclera
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what part of the eye communicates with optic nerve sheath?
sclera
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highly vascular, pigmented layer that lies directly beneath the sclera
choroid layer
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primary function of choroid
to prevent reflection of light within eyeball
-
extension of the choroid layer, located at periphery of anterior choroid
ciliary body
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what is the ciliary body composed of?
smooth muscle tissue, to which suspensory ligaments are attached
-
pigmented membrane composed mainly of muscle tissue that surrounds the pupil
iris
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innermost layer of globe
retina
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what does the retina do?
- it is the photoreceptive layer of the eye
- receives and transmits images to the brain via optic nerve
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distinct area of acute vision
macula
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center of macula
fovea centralis
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area of dense neurons in which the optic nerve exits the globe
optic disc
-
how many photoreceptors does optic disc contain?
none
-
clear, biconvex disk contained in a transparent capsule, lying directly behind the iris
lens
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how is the lens held in place?
suspensory ligaments called zonules
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what fills the anterior chamber of the anterior eye?
aqueous humor (produced by ciliary epithelium)
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through what does aqueous humor pass?
through the pupil and into the canal of Schlemm
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what is the posterior chamber filled with?
vitreous humor
-
what is vitreous humor?
gel-like substance that nourishes the inner tissue layers, gives shape to the posterior globe and acts as a refractive medium for light
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what does the lacrimal apparatus do?
produces tears
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lacrimal apparatus consists of:
- lacrimal gland
- caruncle
- tear ducts
- lacrimal sac
- nasolacrimal duct
-
opening of each duct of lacrimal apparatus
lacrimal punctum
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what are tears composed of?
proteins, mucus, sodium chloride, glucose and enzymes
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bending of light rays through a transparent medium
refraction
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process in which lens continually changes shape to maintain focus of an image on the retina
accommodation
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what is test for visual acuity performed with?
photo-opter
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what is a slit lamp used for?
to examine anterior chamber of the eye
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what is used to stain the cornea and highlight irregularities of the epithelial surface?
fluorescein
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what is used to measure the intraocular pressure?
tonometer
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what is direct examination of the eyes performed with?
ophthalmoscope
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what does an ophthalmoscope do?
magnifies the focal point
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what is used extensively in the diagnosis and evaluation of retinal and choroid diseases?
fluorescein angiography
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what is used to measure the density of eye tissues and detect abnormalities?
ophthalmic ultrasonography
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what does a B-scan ultrasound do?
produces image of the target tissue that shows a series of spots, brightness of which corresponds to tissue density
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what does an A-scan ultrasound do?
depicts tissue density as amplitude on two axes
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what tests are used in the evaluation of the orbital and intracranial structures?
MRI and CT
-
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most common cause of cataracts?
aging
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inflammation or infection of lacrimal sac
dacryocystitis
-
dacryocystitis usually arises from?
obstruction of lacrimal canal
-
inversion of eyelid (lower lid)
entropion
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drooping or eversion of eyelid
ectropion
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optic nerve and visual field damage
glaucoma
-
what is glaucoma usually caused by?
inadequate drainage of aqueous humor - unrelieved pressure damages optic nerve and may result in progressive blindness
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degeneration of the rod and cone photoreceptor cells of the retina
macular degeneration
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most common cause of blindness in people over age 65
age-related macular degeneration (ARMD)
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separation or tear in retina, allowing vitreous to seep between layers and delaminate them
retinal detachment
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inability to coordinate the extraocular muscles
strabismus
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cause of strabismus
- weakness of paralysis of muscles
- can be congenital or acquired
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what condition is a medical emergency that requires surgery?
retinal detachment
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lens implants are treated in much the same way as?
medications
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what type of table is used in most facilities for a patient acquiring ophthalmic surgery?
combination stretcher-operating table because shifting the patient immediately after surgery may result in increased IOP and eye injury
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what types of anesthetic is used for most ophthalmic surgeries?
regional block and monitored sedation
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antiseptics used for eye prepping
dilute povidone-iodine (5% or as directed by MD) and hexachlorophene
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supplies needed for sterile prep setup
- small basins
- surgical towels
- plastic towel drapes
- lint-free gauze sponges
- cotton balls
- cellulose eye sponges
- balanced salt solution (BSS)
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prep area
eyelid and margins, inner and outer canthus, brows and face, ending at chin
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how is prep solution runoff prevented?
by squeezing excess solution from each sponge and a small piece of cotton placed in operative side ear
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type of anesthetic used for pediatric patients
general anesthetic
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what is lidocaine with epinephrine used for?
to maintain vasoconstriction at the operative site
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mydriatic drugs
phenylephrine (Neo-Synephrine, Mydfrin)
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what do mydriatic drugs do?
dilate the pupil
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what are mydriatic drugs used for?
- examination of the retina
- testing of refraction
- easier removal of lenses
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what does atropine do?
- dilates pupil, inhibits focusing, anticholinergic, potent
- long duration of action (7-14 days)
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what does epinephrine do?
dilates pupil, added to BSS for irrigation to maintain pupil dilation during cataract surgery or vitrectomy
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miotic drugs
- carbachol (Miostat)
- acetylcholine chloride (Miochol-E)
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what do miotic drugs do?
- constrict pupil
- used intraocularly during anterior segment surgery
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topical anesthetics
- tetracaine hydrochloride
- proparacaine hydrochloride
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onset of topical anesthetics
5-20 sec
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duration of action of topical anesthetics
10-20 min
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injectable anesthetics
- lidocaine (Xylocaine)
- bupivacaine (Marcaine, Sensorcaine)
- mepivacaine (Carbocaine)
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onset and duration of lidocaine
- onset - 4-6 min
- duration - 40-60 min, 120 min with epinephrine
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onset and duration of bupivacaine
- onset - 5-11 min
- duration - 8-12 hours with epinephrine
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onset and duration of mepivacaine
- onset - 3-5 min
- duration - 2 hour (longer with epinephrine)
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additives to local anesthetics
epinephrine (prolongs anesthesia and reduces bleeding)
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viscoelastics
Healon in sterile syringe assembly
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what is Healon used for?
- lubricant and support
- maintains separation between tissues to protect endothelium, maintain anterior chamber intraocularly and prevent postoperative increase in pressure
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requirements for Healon use
- should be refrigerated
- allow 30 min to warm to room temp
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irrigant used
BSS - used to keep the cornea moist during surgery
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hyperosmotic agent
mannitol (Osmitrol) - reduces IOP
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anti-inflammatory agent
betamethasone sodium phosphate and betamethasone acetate suspension (Celestone) - prophylaxis
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what is cocaine used for?
used on cornea to loosen epithelium before debridement and on nasal packing to reduce congestion of mucosa
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what is fluorescein used for?
- IV - diagnose retinal disorders
- topical - stains cornea
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2 types of ESU systems commonly used in eye surgery
- single-use, battery-powered cautery
- bipolar unit
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handheld battery ESU has?
very small filament tip that becomes hot when the unit is activated
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what does the filament of handheld ESU do?
coagulates very small vessels of the eye, but does not cut
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when is bipolar ESU used?
procedures in which fine cutting and coagulation are required
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what are eye sponges made of?
lint-free cellulose
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is sponge used on cornea?
never
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how does the sponge absorb fluid?
by wicking - done by holding the tip of the sponge in contact with the fluid and allowing the sponge to absorb it
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eye suture sizes
from 4-0 to 12-0
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how should eye sutures be handled?
as little as possible
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types of sutures frequently used to close circumferential incisions
double-arm sutures
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procedure in which nodal tissue arising from a sebaceous gland is excised from the tarsal plate
chalazion excision
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inflammatory, benign growth that originates in sebaceous gland of eyelid
chalazion
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how is chalazion excision performed?
lid is everted and vertical incision is made through tarsal plate
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goal of entropion repair
restore eyelid to correct anatomical position by resection
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what is entropion caused by?
weakness and imbalance of eyelid muscles
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goal of ectropion repair
restore eyelid to normal position
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how is ectropion repair performed?
wedge of tissue is removed from lower tarsal plate and canthal tendon is secured to periosteum of orbital rim
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goal of pterygium repair
membrane is surgically removed to prevent loss of vision
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patch of degenerative elastic tissue that proliferates from the conjunctiva in response to chronic irritation
pterygium - appears as a white or yellowish vascular mass
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when is pterygium surgery indicated?
when documented growth has occurred, lesion is close to the visual axis or vision is impaired
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creation of permanent opening in tear duct for drainage of tears
dacryocystorhinostomy
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inflammation of lacrimal sac, causing pain, redness and swelling of medial canthus
dacryocystitis
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2 groups of patients in which lacrimal sac inflammation and infection usually are seen
- adults over age 40
- infants
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goal of dacryocystorhinostomy
reestablish drainage into lacrimal duct system
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alternative method of dacryocystorhinostomy
stent with silicone tubing
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goal of lacrimal duct probing
lacrimal duct is opened and obstruction is removed
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most common sign of abnormality of lacrimal system
constant tearing
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how is punctum checked for patency during lacrimal duct probing?
with a 2-mL syringe and cannula
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what is done if lacrimal duct probing does not relieve obstruction?
silicone tube may be implanted
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goal of muscle resection and muscle recession
correct deviation of the eye caused by strabismus
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2 procedures commonly used to treat strabismus
- lateral rectus resection
- medial rectus recession
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what is done in lateral rectus resection?
portion of the muscle is excised and the severed end is reattached at the original site of insertion, limiting the drift of the eye
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what is done in medial rectus recession?
muscle is detached from its insertion, moved posteriorly, and reattached, releasing the eye and allowing it to move farther in lateral position
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during muscle resection/recession, what can traction on the muscles cause?
- vagal response, resulting in bradycardia
- surgeon will then temporarily release traction on muscles
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full-thickness transplantation of donor cornea to restore vision
keratoplasty
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most common causes of corneal opacification
- chemical and thermal burns
- infection
- degenerative disease
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2 types of corneal transplantation
- lamellar (partial penetrating)
- penetrating (full-thickness)
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goal of LASIK surgery
shape curvature of the cornea and correct refractory problem
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what is LASIK surgery performed with?
excimer laser
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hyperopia
- farsightedness
- anterior-posterior distance of the globe is too short
- images that are close are blurred because focal point is behind retina
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myopia
- nearsightedness
- anterior-posterior distance of the globe is too long
- focal point lies in front of retina
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astigmatism
uneven curvature of refractive medium
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activities after LASIK surgery
avoid activities requiring bending or kneeling for the first week after surgery
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fragmentation of tissue by ultrasonic vibration
phacoemulsification
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most common form of cataract removal
phacoemulsification
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goal of cataract extraction
remove opaque lens and replace with an intraocular lens implant to restore vision
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what is instilled into the eye during cataract prep for antibacterial effect?
Betadine 10%
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what complication is most common in the first 2-3 days after cataract surgery?
blood in the anterior chamber of the eye
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goal of anterior vitrectomy
to remove vitreous from anterior chamber, for example if vitreous is overhydrated during cataract surgery
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major complication of vitrectomy
retinal detachment
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when is scleral buckling performed?
when sensory layer of retina becomes separated from pigment epithelial layer
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what does a tear in the retina cause?
sudden, painless loss of vision or "shadowing" (like a curtain) with often light flashes and floaters
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what is a tear in the retina called?
rhegmatogenous detachment
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how is retinal detachment repaired?
adhesions are produced between the layers using cryotherapy or diathermy, followed by scleral buckling
-
what is involved in scleral buckling?
- Silastic or foam band is attached to the sclera
- synthetic buckles are placed over the band, causing it to indent and puts the tissue in close contact with retina during healing
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what is done when vitrectomy is performed in conjunction with scleral buckling?
vitreous gel is replaced with Healon or gas through small puncture wound - used to eliminate traction and tearing on the retina
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what does intravitreous gas injection do?
exerts pressure on the retina while subretinal fluid is reabsorbed
-
gases that are injected intravitreously
- sulfur hexafluoride
- perfluoropropane
-
why is trabeculectomy performed?
to create a channel from which the aqueous humor may drain from the anterior chamber for the treatment of glaucoma
-
group of diseases characterized by optic nerve damage and visual field loss
glaucoma
-
IOP is normally maintained by what?
aqueous humor
-
type of glaucoma with sudden rise in IOP caused by total blockage or obstruction of aqueous humor at root of iris
primary angle closure glaucoma
-
type of glaucoma that occurs in both eyes in which outflow of aqueous humor is obstructed in trabecular meshwork
primary open angle glaucoma
-
subtype of open angle glaucoma in which intraocular pressure is normal, there is retinal damage and visual field loss with migrain and optic disc hemorrhage
normal tension glaucoma
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type of glaucoma in which the fluid drainage system is abnormal at birth - infant's eye distends and corneal haziness occurs
congenital glaucoma
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goal of argon laser trabeculoplasty
shrink collagen and stretch canal of Schlemm, expanding canal, increasing drainage and reducing IOP
-
most common complication of laser surgery for glaucoma
increase in pressure in the eyes
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goal of orbital decompression
one or more bony sections of orbital cavity are removed to reduce pressure on optic nerve
-
indications for orbital decompression
- to treat hyperthyroidism (Graves' disease)
- to treat pressure on optic nerve caused by tumor or swelling
-
most common approach to orbital decompression
through the lower lid
-
complete removal of eyeball
enucleation
-
procedure in which contents of the eye are removed, but outer shell of the sclera and muscle attachments are left intact
evisceration
-
indications for enucleation
intraocular malignancy, penetrating ocular wound, painful blind eye, painless, disfigured blind eye
-
implant that is inserted to shape orbital cavity
sphere
-
placed over sphere and covers its surface
conformer
-
most common orbital implant materials
- porous polyethylene
- hydroxyapatite
-
removal of entire eye and orbital contents, including eyelids, ocular muscles and orbital fat
orbital exenteration
-
indications for orbital exenteration
cancer, only after all other therapies have failed
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