Ophthalmic surgery

Without a natural or prosthetic lens.

Balanced salt solution used for eye irrigation.

During cataract surgery a continuous circular rent is created in the anterior capsule to allow removal or phacoemulsification of the nucleus of the opacified lens.

Cataract

Cloudy or yellowed lens of the eye.

Cyclodialysis

Surgical opening between the anterior chamber and the suprachoroidal space to decrease elevated pressure within the eye in glaucoma.

Discission

Cut into soft tissue such as a cataract.

Gonioscopy

Examination of the anterior chamber with a special lens.

Haptic

Tiny flexible prong used to secure a prosthetic intraocular lens.

IOL

Intraocular lens.

Phacoemulsification

Irrigation and aspiration of a cataract using ultrasonic vibrations.

Pneumoretinopexy

Repositioning of a detached retina by use of a gas or air bubble in the vitreous.

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• Historical Perspective

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• Flashcards

• Tips for the Scrub Person and Circulating Nurse

• Self-Assessment Activities

• Glossary

Anatomy and physiology of the eye

A thorough understanding of the anatomic structure and physiology of the eye is fundamental to a comprehension of the surgical procedures.

The eyeballs are framed bilaterally by the bony orbits. Each orbit comprises seven separate bones: the maxilla, palatine, frontal, sphenoid, zygoma, ethmoid, and lacrimal bones. Foramina, fissures, and grooves provide stability and access for vessels, nerves, and attachments. Adjacent anatomic structures include the lacrimal apparatus medially, the extraocular muscles and their attachments, and the sinuses.

The globe, or eyeball, is situated within the bony orbit and is surrounded by a padding of fatty tissue. Its position is maintained by extraocular muscles and fascial attachments. The sclera, the white outer tissue layer of the globe, is contiguous with the transparent avascular cornea anteriorly. The conjunctiva is the mucous membrane that lines the inner side of the upper and lower eyelids and the exposed portion of the sclera, except for the cornea (Fig. 39-1).

The eyeball is divided into two segments: anterior and posterior. The anterior segment of the eye includes the cornea, the anterior chamber filled with aqueous fluid (humor), the circular pigmented iris, and the lens. The lens consists of a clear, transparent, gelatinous protein encased in a capsule. It is supported by a series of suspensory ligaments called zonules. The posterior segment, the portion of the eye behind the lens, contains the vitreous fluid (which must be clear for vision), the retina, and the choroid linings, which are the vascular nourishing layers (Fig. 39-2).

FIG. 39-2 Anatomy of the eye. A, Anterior segment. 1, Cornea; 2, anterior chamber; 3, pupil; 4, iris; 5, lens; 6, ciliary body; 7, zonule. B, Posterior segment. 8, Vitreous body; 9, retina; 10, choroid; 11, sclera; 12, optic nerve; 13, central retinal artery.

Innervation of vision and sensory transmission is derived from the second cranial nerve (optic nerve) (Fig. 39-3). Motor innervation extends from the third cranial nerve (oculomotor nerve) to the rectus muscles. The superior oblique muscles are innervated by the fourth cranial nerve (trochlear nerve). The lateral rectus muscle is innervated by the sixth cranial nerve (abducens nerve).

FIG. 39-3 Location of optic nerve in relation to eye muscles.

The arterial supply of the eyeball, muscles, and eyelids comes from the ophthalmic artery, which is a branch of the internal carotid artery and drains into the superior and inferior ophthalmic veins. The retina has a separate blood supply that is derived from the central retinal artery. Drainage is through the retinal vein.

The physiology of vision requires the following:

• Functioning visual apparatus

• Source of light

• Intact neurovascular communication with the brain

• Interpretation by the brain of what is seen

The eye resembles a camera with a compound lens system. Light rays emanating from an object in the field of vision are transmitted to the eye, where they traverse the optical system to reach the retina. The retina corresponds to the film of the camera. The area of highest sensitivity for details is called the macula, which is located approximately in the center of the retina at the posterior pole. The intensity of light is automatically determined by the size of the pupil, which is controlled by the iris muscles. The iris functions like the shutter of a camera.

The optical system comprises the transparent cornea, or window of the eye; the aqueous fluid behind the cornea; the pupil, or opening in the colored iris; and the lens. The naturally flexible lens focuses light rays by bending them to form an image on the retina—the innermost layer of the eye that contains the visual sensory nerve endings. These cells are connected to nerve fibers that converge toward the brain to become the optic nerve. The sensory cells translate patterns of light into nervous impulses, which are transmitted to the brain via the optic nerve. The occipital portion of the brain interprets the images of light rays registered on the retina.

Ophthalmic surgical patient care

Impaired vision may produce prolonged severe stress and alter the patient’s self-image. Most patients with impaired vision are older adults. When caring for these patients, the health care provider should reassure them, exercise patience, give directions clearly, anticipate needs, and check their comfort level. Specific patient care considerations include but are not limited to the following:

1. Urinary urgency can be a problem in geriatric patients or in patients receiving diuretic medication. Although the patient should void before coming to the OR, offer the patient the use of a bedpan or urinal before he or she transfers to the operating bed. Severe urinary urgency can cause increased intraocular pressure (IOP) during the procedure. Strain and gross movement are dangerous and are to be avoided.

2. The surgeon and circulating nurse verify the intended surgical site with the patient and with the office records. After confirmation and to avoid error, some surgeons place an indelible mark on the side of the patient’s neck that corresponds to the affected eye.

3. The patient is placed in the supine position on the operating bed so the head and body are aligned. Most ORs use a dedicated ophthalmic operating bed that can be used during the procedure and to transport the patient to the postprocedural recovery area (Fig. 39-4). The top of the head is in line with the edge of the operating bed for accessibility. The head should not be turned greatly in either direction; the head is stabilized in a ring-shaped pillow (donut). The patient’s gown is untied at the neck to prevent pressure. Any obstruction to venous circulation can cause undue increased IOP, which can produce a loss of vitreous humor when the eye is opened. To assist venous return from the head, the operating bed is tilted so the patient’s head is elevated by 5 to 10 degrees. For long procedures, an egg crate–type or gel pad mattress may be placed on the bed. Additional padding may be needed to position kyphotic or lordotic patients.

4. Skin preparation and draping procedures are performed according to routine. Sterile plastic drapes are often placed over woven textile drapes to contain lint, especially before lens implantation. A patient with a drape over the face is often apprehensive and afraid of suffocating. To help eliminate the feeling of claustrophobia, the drape can be placed over a Mayo stand or clipped to an intravenous pole to create a tentlike space above the patient’s nose and mouth (Fig. 39-5). Oxygen is delivered via nasal prongs or insufflated to the facial area beneath the drape at 6 to 8 L/min. An electrosurgical unit (ESU) is not to be used in an oxygen-rich environment because of the increased risk for ignition.

FIG. 39-5 Creating a tent with the surgical drape and the Mayo stand for patient comfort.

5. A quiet, stimulant-free environment is provided for the awake patient who is receiving a local anesthetic.

6. Because the patient has no defensive blink reflex to protect the retina from light exposure, some surgeons use a sterile, opaque pupillary shield to protect the patient’s retina from phototoxic damage caused by prolonged exposure to illumination of the microscope. Some scopes have a sensor near the eyepiece that dims the light source when the surgeon is not looking directly into the scope. The light reverts back to the desired intensity when the surgeon is positioned at the eyepiece.

7. The team should prepare for emergencies by anticipating problems. Fast action can make the difference between a seeing eye and a nonseeing eye postoperatively. The following are potential complications:

a. A systemic reaction to medications or local anesthetic drugs and cardiac arrest.

b. A loss of vitreous, which requires the removal of vitreous from the anterior chamber with a vitreotome to prevent prolapse of the wound, severe inflammation, or an updrawn pupil.

c. An expulsive hemorrhage or an expulsion of ocular contents, which requires a sharp knife (e.g., Beaver blade, Wheeler knife) for fast cutdown into the pars plana area and an 18-gauge needle or cannula attached to a syringe to aspirate blood and reduce pressure in the vitreal compartment in an effort to save the eye and vision (Fig. 39-6).

FIG. 39-6 Pars plana vitrectomy for emergency bleeding.

d. Instrument failure. Hand aspiration devices should be available for immediate use.

8. A wide variety of fine-size absorbable and nonabsorbable sutures is used. The scrub person follows the manufacturer’s recommendations for handling these delicate materials and needles with the appropriate needle holders. Special techniques are used in microsurgery.

9. Hemostasis is attained with bipolar cautery and a bipolar eraser pencil. Sponges are spear shaped and consist of precut compressed cellulose on sticks (Fig. 39-7).

FIG. 39-7 Instruments for hemostasis of the eye.

10. No foreign material should be introduced into the surgical wound. In intraocular procedures, no portion of any instrument or item intended to enter the eye should be touched by a gloved hand. To remove any debris or impurity, intraocular lenses (IOLs) are soaked and rinsed in balanced salt solution (BSS) and sometimes lubricated with sodium hyaluronate (Healon) before insertion.

11. Inflammation should be kept as minimal as possible because even slight inflammation may result in total functional loss. Steroids are often administered locally, subconjunctivally, and, sometimes, systemically. The eye may respond violently to the slightest amount of trauma.

12. Antibiotic drops are often instilled topically for 24 hours preoperatively and postoperatively.

13. A sterile eye pad is commonly applied at the conclusion of the surgical procedure. A protective plastic or metal shield may be secured over the eye pad to guard against mechanical injury. Absorbable corneal shields may be used.

14. The patient should not be permitted to participate in the move from the operating bed after intraocular procedures; this prevents a sudden rise in IOP and/or dislocation of the IOL implant.

15. Arm restraints are essential for infants and young children. Restraints are applied to adults only under extreme circumstances, such as disorientation. The use of side rails is standard procedure for all patients undergoing ophthalmic surgery.

An important aspect of postoperative care is informing the patient not to get out of bed alone. A fall or injury to the eye can nullify an otherwise successful surgical procedure. The patient must not do anything to increase IOP (e.g., bend over at the waist, lift heavy objects). Deep breathing postoperatively is encouraged, but coughing is avoided because it could increase IOP and rupture the suture line. The patient should report any postoperative pain, swelling, redness, or discharge. The outcome of ophthalmic procedures includes a cosmetic as well as a functional aspect.

Special features of ophthalmic surgery

The patient undergoing ophthalmic surgery faces impairment or loss of vision if the outcome of the surgical intervention is unfavorable. Special features of ophthalmic surgery aim to prevent such a loss. Surgical procedures on the eye are extremely delicate and require precision instrumentation, a steady hand, and quiet surroundings. The operating microscope, all accessory equipment, and microinstruments should be set up and checked before the surgical procedure. The outcome of the procedure depends on the condition of the instruments.

Ophthalmic instrumentation

The tips of these expensive, fragile microinstruments should be protected and handled with extreme care before, during, and after use. Eye instrumentation is unique to the specialty. With rare exception are any of the following used in any other type of surgery:

• Self-retaining lid retractors and scissors (Fig. 39-8)

FIG. 39-8 Eye instrumentation: self-retaining lid retractors and scissors.

• Graspers and manual retractors (Fig. 39-9)

FIG. 39-9 Eye instrumentation: graspers and manual retractors.

• Enucleation and measuring devices (Fig. 39-10)

FIG. 39-10 Eye instrumentation: enucleation and measuring devices.

• Punctum plug and forceps (Fig. 39-11)

• Corneal trephine (Fig. 39-12)

FIG. 39-12 Corneal trephine for cadaver tissue procurement.

Operating microscope

Ophthalmic surgeons use the operating microscope for intraocular procedures. When the operating microscope is used, the operating bed should be mechanically secure, and the patient’s head should be stabilized. Inadvertent movement is not tolerated because of the minute surgical field. The headrest should be narrow so that it does not obstruct the surgeon’s approach to the surgical site from the sides of the vertical column of the microscope. The patient is instructed about the importance of remaining still during the surgical procedure. Otherwise, the patient could easily move out of the field of vision under the microscope or precipitate a complication.

The assistant observes the surgical procedure through an assistant’s ocular and irrigates the cornea with BSS to prevent drying (Fig. 39-13). The assistant should bring to the surgeon’s attention any potentially unsatisfactory situation that the surgeon cannot observe from his or her position. Some scrub persons are trained to first-assist. The surgeon and the assistants should limit their caffeine intake before the procedure to promote steady hands when using microinstrumentation under the microscope.

FIG. 39-13 Surgeon and first assistant using a ceiling-mounted microscope.

Ophthalmic drugs

Many drugs are critical to the preparation of the eye for the surgical procedure. Orders for patient preparation often contain common abbreviations that identify the eye(s) to receive drops: OD (right eye), OS (left eye), and OU (both eyes); however, the Joint Commission (TJC) has advised that the use of abbreviations can lead to human error and recommends not using them in the interest of patient safety. Before skin preparation, the circulating nurse instills the medications and anesthetic drops as ordered. The following procedures should be observed when instilling eye- drops:

1. Wash your hands.

2. Identify the correct medication, eye, and patient.

3. Check for allergy or sensitivity.

4. Explain the procedure to the patient.

5. Tilt back the patient’s head, and tell the patient to look up. While gently pulling down on the lower lid, instill the medication in the middle third of the inner aspect of the lower lid. Release the lid while the patient slowly closes the eye to retain the drop; let the patient close the eye between repeated drops. In a struggling child, have a parent tilt the child’s head back and close both eyes. Instill the medication at the inner canthus. The drop will roll into the eye as the child opens it.

Some medications, such as atropine, may have a systemic effect. To prevent drainage into the tear duct, nose, and stomach, gently blot excess fluid. In small infants or young children, systemic absorption is avoided by applying finger pressure over the lacrimal sac region (inner canthus) of both eyes simultaneously for 1 minute.

6. Administer only the specified number of drops.

7. Read the label on the vial before each instillation.

8. Each patient should receive a fresh, single-use, disposable vial of medication that is discarded after use.

Mydriatic and miotic drugs

Medications may be given to alter the size of the pupil (Fig. 39-14), including the following:

FIG. 39-14 Effects of miotic and mydriatic drugs.

• Mydriatic drops: 2.5% or 10% phenylephrine (Neo-Synephrine) to dilate the pupil.

• Mydriatic-cycloplegic drops: 1% cyclopentolate hydrochloride (Cyclogyl), 1% atropine, and 0.25% scopolamine (Isopto-Hyoscine) to dilate the pupil, paralyze the ciliary body, diminish the reaction to trauma, and prevent anterior synechiae (e.g., adherence of iris to the lens). These drugs are longer acting than phenylephrine.

• Miotic drops: 2% pilocarpine to constrict the pupil.

Local and topical anesthesia

Except in children and select patients, local and topical anesthetics are commonly used for ophthalmic surgical procedures. Most surgical procedures are scheduled as monitored anesthesia care or attended local.⁴ An anesthesia provider monitors the patient and administers oxygen and/or supplements the local anesthetic if necessary. Intravenous midazolam (Versed) and/or fentanyl (Sublimaze) or propofol (Diprivan) is often given to relax the patient. The sedative effects of these agents increase the patient’s tolerance to procedures. If a general anesthetic is used, the usual general anesthesia routines are followed.

Local anesthesia consists of the following:

1. Topical instillation of anesthetic drops. The drug used may be 0.5% proparacaine (Ophthaine), 0.5% tetracaine (Pontocaine), or 2% lidocaine (Xylocaine MPF [methylparaben-free]). Most surgeons prefer to use this method in combination with moderate sedation.

2. Local infiltration by injection of the lids and tissue around the eyes with anesthetic medication.

3. Retrobulbar block. An absolutely quiet eye is necessary, especially at high magnifications of the microscope. When general anesthesia is used, some surgeons administer a retrobulbar block for immobility and to lower IOP.⁴ A popular solution for this block consists of a mixture of equal parts of 2% or 4% lidocaine and 0.75% bupivacaine, 3.75 units/mL, for penetration. A 25-gauge × 1½-inch (3.8-cm) needle with a sharp, rounded point (e.g., Atkinson needle) and a 5-mL syringe are used. The surgeon inserts the needle behind the eyeball to anesthetize the globe and paralyze the muscles. The patient is asked to look up and away from the injection site and is told that a slight burning sensation may accompany the injection. Up to 5 mL of solution may be slowly and carefully injected.

Retrobulbar block may be followed by intermittent massage of the eye to soften it, lower IOP, and facilitate surgical manipulation during cataract extraction, especially when insertion of an IOL is being contemplated. Massage is continued until the IOP is lowered to a satisfactory level (e.g., 10 to 12 scale reading on sterile Schiøtz tonometer). Some surgeons apply the Honan balloon pressure device to soften the eyeball after a retrobulbar block (Fig. 39-15). In using this device, a small inflatable balloon is placed directly over the closed eyelid and is secured with a strap around the head. The balloon is inflated to 30 to 40 mm Hg for 5 to 10 minutes to lower intravitreal pressure.

FIG. 39-15 Honan apparatus for softening the eyeball preoperatively.

4. Peribulbar anesthesia. This is an alternative to retrobulbar injection. With this method, injections are made in the soft tissue superior and inferior to the globe rather than behind it. A greater amount of the same anesthetic solution used for retrobulbar injection is used for peribulbar anesthesia. With this procedure, adequate anesthesia is obtained without the risk for retrobulbar hemorrhage.

Ophthalmic solutions

Extreme and constant care must be used with ophthalmic solutions. Nearly all of these solutions are colorless and may be stored in similar receptacles. These solutions are immediately and individually labeled by the scrub person; the solution is discarded if the identification is missing. Solutions for intraocular use must be separated from all other solutions. Ideally, these solutions should be filtered with micropore filters before injection.

Epinephrine or other sympathomimetics may have side effects when used with some anesthetic agents. Therefore, the surgeon should check with the anesthesia provider before using medications intraoperatively. Medications that may induce vomiting are also avoided. Any straining or gross movement may cause intraocular hemorrhage, a sudden rise in IOP that results in a loss of vitreous, or the expulsion of ocular contents through the wound; all of these conditions can cause blindness.

Ocular surgical procedures

For convenience, surgical treatment of the eye can be divided into two main classifications:

1. Extraocular. Conditions affecting the exterior surface of the eye, eyelid, or the orbit.

2. Intraocular. Conditions pertaining to the interior contents of the eye.

Extraocular procedures

Eyelid

The anatomy of the upper and lower eyelids is described in Figure 39-16.

Excision of neoplasm of the eyelid.

Tissue may be excised with a knife, an ESU, diathermy, or cryosurgery. An extremely common but benign tumor of the lid is the chalazion—a cystic alteration of one of the oil-secreting meibomian glands in the lid (Fig. 39-17, A). The resulting accumulation of oil forms a hard tumor of the lid and requires excision. The excision is usually an office or ambulatory surgical procedure. Chalazion is differentiated from a stye by the location on the lid. Styes are small infected lash follicles (see Fig. 39-17, B).

FIG. 39-17 Common benign lesions of the eye commonly treated with surgery.

After removal of a malignant lesion of the lid, plastic procedures such as Z-plasty, sliding flaps from adjacent areas, or full- or partial-thickness flaps from the opposing lid are used to close the defect.

Correction of ptosis.

Ptosis, a drooping of the upper lid, may be acquired in adulthood but is more commonly congenital. For the levator aponeurosis procedure, an incision is made on the front surface of the lid to expose the tarsus and the aponeurosis. The tarsus is sutured to the aponeurosis, and the skin incision is closed.

For the frontalis suspension procedure, the anterior surface of the upper lid is incised at the crease, and two smaller incisions are made above the eyebrow. A graft of fascia or synthetic material is attached to the tarsus and passed through the deep lid tissue and brought out through the eyebrow incisions. The graft material is secured, and the skin incisions are closed.

Repair of acquired malformation of the eyelid.

Conditions such as senile ectropion or entropion most commonly affect the lower lid (Fig. 39-18). Ectropion is a condition in which either the upper or lower lid is everted (turned out) to expose the conjunctival surface. Entropion is the opposite condition, in which the lid margin is inverted (turned in). As a result, the eyelashes often abrade the cornea. Various procedures may be used to correct both conditions.