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Chapter 63 – Corneal and Conjunctival Surgery

Chapter 63 – Corneal and Conjunctival Surgery

 

MING X. WANG

CAROL L. KARP

ROBERT P. SELKIN

DIMITRI T. AZAR

 

KERATOPLASTY

INTRODUCTION

Recent years have seen remarkable progress in the technologies involved in keratoplasty. The successful outcomes enjoyed by patients who undergo modern penetrating keratoplasty and lamellar keratoplasty are the result of advances in operating microscope design, suture technology, surgical techniques, and corneal topography and of the availability of carefully preserved corneal tissue along with a better understanding of corneal and ocular surface physiology.

HISTORICAL REVIEW

Corneal grafting techniques date back to the latter part of the 19th century and earlier part of the 20th century,[1] as exemplified by pioneer ophthalmologists such as Reisinger,[2] von Hippel,[3] and Elschnig.[4] Today, penetrating keratoplasty is the most common and successful human transplantation procedure. Over 40,000 corneal transplantations are performed in the United States each year. Optical results have improved greatly as a result of advances in tissue selection and preservation, trephines, and management of postoperative astigmatism. Corneal grafts are generally performed for two reasons—to restore globe integrity and to restore vision.

Lamellar corneal grafts date back to 1886, when von Hippel[3] successfully performed the first lamellar graft in a human. Developments in lamellar grafting techniques, surgical instrumentation, anesthetic agents, and donor tissue preservation have contributed to the success of this surgical technique. However, in the past few decades, lamellar keratoplasty has become less popular because of the remarkable success of the penetrating corneal graft technique.

ANESTHESIA

Corneal transplant surgeries may be performed using local or general anesthetic. Local anesthetic is used for adult and cooperative patients. Typically, local anesthetic consists of peribulbar or retrobulbar injection of lidocaine (lignocaine) 2%, bupivacaine 0.75%, and hyaluronidase. Peribulbar anesthetic may be preferred over retrobulbar injection to avoid globe penetration. To prevent squeezing during surgery, a lid block may be employed. General anesthetic is reserved for the pediatric age group and uncooperative adults or for use in open globes.

SPECIFIC TECHNIQUES

Lamellar Keratoplasty

Lamellar keratoplasty is a procedure in which a partial-thickness graft of donor tissue is used to provide tectonic stability and/or optical improvement. A partial-thickness section of donor stroma or sclera is used. There are generally two types of lamellar keratoplasty: anterior lamellar keratoplasty and posterior lamellar keratoplasty.

In an anterior lamellar keratoplasty procedure, the transplanted tissue does not include corneal endothelium, and thus donor tissue is obtained more easily from older eyes and this procedure avoids endothelial rejection. Indications for anterior lamellar keratoplasty mainly include anterior corneal pathology in which the posterior cornea is unaffected.

In recent years deep lamellar keratoplasty and posterior lamellar keratoplasty techniques have been developed in which the main objective is to replace diseased corneal endothelium while keeping the anterior corneal surface intact, thus reducing refractive error and irregular astigmatism.

PREOPERATIVE EVALUATION AND DIAGNOSTIC APPROACH.

Two major indications exist for anterior lamellar keratoplasty [5] [6] —tectonic graft for structural support and/or cosmesis and optical grafts. For posterior lamellar keratoplasty, the aim is to replace the diseased endothelium.

A tectonic graft is the most common type of anterior lamellar keratoplasty performed. It is used to reinforce areas of thinned cornea to prevent melting and perforation or to restore ocular surface integrity, such as after pterygium surgery.

Optical grafts are used to replace diseased anterior cornea to improve visual function and require that the posterior stroma of the recipient is healthy. Lamellar optical grafts are seldom used today because of the increased use of phototherapeutic keratectomy and the excellent outcomes with penetrating keratoplasty.

Regarding posterior lamellar keratoplasty, the main advantage is the preservation of the anterior corneal tissue and thus maintenance of the refractive character of the cornea.

The rationale for a lamellar keratoplasty must be examined carefully and the various surgical options thoroughly discussed with patients. Compared with penetrating keratoplasty, anterior lamellar keratoplasty eliminates the chance of endothelial rejection, is an extraocular procedure, and carries a lower risk of endophthalmitis. In addition, the healing period after lamellar keratoplasty is shorter than that after penetrating keratoplasty. The disadvantages of anterior lamellar keratoplasty include the technical difficulty of the surgery and the possible opacification and vascularization of the donor-recipient interface. Penetrating keratoplasty offers a significantly better visual prognosis[5] but requires careful screening of donor endothelium and carries risks of rejection and infection (see later sections on penetrating keratoplasty). With regard to posterior lamellar keratoplasty, the risk of the intraocular procedure and the increased surgical difficulty in performing posterior lamellar grafts need to be carefully considered and weighed against the risk and benefit of penetrating keratoplasty.

SURGICAL TECHNIQUES

Anterior Lamellar Dissection of the Host Tissue.

If necessary, the globe is stabilized with bridle sutures passed beneath both superior and inferior rectus muscles. A trephine is used gently to mark the extent of graft needed. After the position of the graft has been confirmed, a partial-thickness trephination is performed until the desired depth of dissection is reached (see Fig. 63-1 ). A blade or a microkeratome is then used to extend the dissection plane along the entire host corneal tissue until the

 

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Figure 63-1 Partial-thickness trephination. This is performed on the host in the desired location and to the desired depth. Care must be taken not to perforate the cornea.

dissection of the host tissue is completed. The goal is to create a smooth, uniplanar recipient bed (see Fig. 63-2 ). If globe perforation occurs, the procedure is converted into a penetrating keratoplasty. This is also generally why dissection of the host tissue is performed prior to preparation of the donor cornea when a lamellar keratoplasty is performed. In recent years, another technique has been developed for deep anterior lamellar dissection.[7] [8] In this new technique, aqueous fluid is first exchanged with air, creating an air-endothelium interface for visualization. A deep stromal pocket is then created using viscoelastic material followed by trephination of the anterior lamellar disc.

In posterior lamellar keratoplasty, there are mainly two techniques: microkeratome-assisted posterior lamellar keratoplasty [9] [10] [11] [12] [13] and posterior lamellar keratoplasty using a deep stromal pocket approach. [14] [15] [16] [17] In the first technique, a corneal flap is created using a microkeratome similar to that used in a LASIK procedure. Posterior stroma tissue is then excised by trephination and replaced by a donor disc. The anterior lamellar flap is then repositioned to its original place and sutured. In the second approach to posterior lamellar keratoplasty, a deep stromal pocket is created across the cornea through a superior scleral incision. A posterior lamellar disc is then excised using a custom-made flat trephine placed into the deep stromal pocket.

Donor Preparation.

In general, the criteria that donor tissue for anterior lamellar keratoplasty must meet are less stringent than those for donor tissue used in penetrating keratoplasty because the donor endothelium is not used; the tissue does not need to be as fresh as that used in penetrating keratoplasty. The corneal stroma may be used up to 7 days postmortem.[18] In contrast, posterior lamellar keratoplasty requires the same stringency of donor tissue as in penetrating keratoplasty because the endothelium is to be transplanted. A fresh or frozen whole donor eye should be used to fashion the anterior lamellar donor tissue.[19] In anterior lamellar keratoplasty, using a scalpel, an incision is made just inside the limbus of the donor cornea to reach the depth of the desired dissection (see Fig. 63-3 ). A Martinez dissector or a cyclodialysis spatula is used to extend the dissection plane within the corneal stroma and harvest the donor tissue (see Fig. 63-4 ). The tissue harvested may be circular, annular, or any other shape, depending on the needs of the

 

 

Figure 63-2 Dissection of diseased area. The diseased area in the host cornea is dissected gently to create a uniplanar, disease-free bed.

 

 

Figure 63-3 Peripheral incision in donor cadaveric tissue. The incision is made to the desired depth at the limbus using a scalpel.

patient ( Figs. 63-5 and 63-6 ). Both cornea and sclera may be used. Usually, donor tissue is slightly oversized (0.25–0.5?mm) compared with the recipient bed. As described previously, donor tissue suitable for penetrating keratoplasty is made available in case perforation occurs in the lamellar dissection of the host tissue. Newer microkeratomes may allow future anterior donor dissection. In posterior lamellar keratoplasty, either an inflated whole globe should be used or an artificial chamber can be used to anchor the scleral rim when only anterior corneal-sclera donor tissue is available. Donor tissue is fashioned in a manner similar to that of the recipient counterpart.

 

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Figure 63-4 Separation of cadaveric cornea. A dissector, such as the Martinez dissector or a cyclodialysis spatula, is used to separate gently the cornea along the lamellar cleavage plane through the entire cornea.

 

 

Figure 63-5 Donor tissue is harvested. A trephine is placed on the cadaveric globe in the size and the shape desired. A circular lamellar graft is being harvested here.

Suture of the Donor Lamellae to Host Bed.

In anterior lamellar keratoplasty, to improve the apposition of the graft-host junction, the edge of the host bed should be undermined to create a horizontal groove using a Paufique knife.[19] The donor lamella is placed on the recipient bed and secured with interrupted 10-0 nylon sutures ( Fig. 63-7 ). The depth of the suture is about 90% of the corneal stroma’s depth. Particular attention must be paid where the sutures are placed to avoid penetration of the globe. The donor tissue margins should not ride anterior to the rim of the recipient bed. At times, an anterior chamber paracentesis may become necessary before lamellar sutures are placed.

 

 

Figure 63-6 Horseshoe or annular lamellar graft. A combination of corneal and scleral tissue may be harvested to give a different tissue shape.

 

 

Figure 63-7 The lamellar tissue is sutured to the host bed. Suture placement is facilitated if the edge of the host bed is undermined. Traditionally, the graft is sutured with 10-0 nylon.

In microkeratome-assisted posterior lamellar keratoplasty, the posterior lamellar disc is sutured onto the recipient posterior stromal rim using 10-0 or 11-0 nylon. The knots are rotated and buried. The anterior stromal flap is then reflected back and repositioned in its original position and sutured. With the deep stromal pocket approach to posterior lamellar keratoplasty, the donor posterior lamellar disc is placed within the recipient rim via the anterior chamber but not sutured.

COMPLICATIONS AND POSTOPERATIVE MANAGEMENT.

In general, an anterior lamellar graft can be extremely successful ( Figs. 63-8 and 63-9 ). The complications are less frequent or serious

 

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Figure 63-8 Lamellar keratoplasty for granular dystrophy. A, Preoperative appearance of a patient who had granular dystrophy limited to the anterior cornea. B, Postoperative appearance following lamellar keratoplasty. (Courtesy of Dr WW Culbertson.)

in nature than those of penetrating keratoplasty. Possible complications of lamellar graft include perforation of the recipient cornea, interface scarring and vascularization, persistent epithelial defect, inflammatory necrosis of the graft and graft melting, infection, astigmatism, and allograft rejection. Careful irrigation and cleaning of the host bed may reduce the incidence of such complications. With regard to allograft rejection, lamellar keratoplasty has a significantly reduced incidence as there is no transplantation of foreign endothelium. Posterior lamellar keratoplasty carries the same risk of graft rejection as in penetrating keratoplasty. In addition, both the posterior and anterior lamellar tissues need to be sealed adequately so wound leak resulting from poor tissue apposition may occur.

Penetrating Keratoplasty

Penetrating keratoplasty refers to the full-thickness replacement of diseased corneal tissue with a healthy donor. Penetrating keratoplasty has become the most frequently performed transplant of human tissues, thanks to advances in microsurgery techniques, suture material, donor tissue handling and storage, and postoperative management.

PREOPERATIVE EVALUATION AND DIAGNOSTIC APPROACH.

Penetrating keratoplasty may be used to provide tectonic support, such as in corneal thinning and perforation, and improvement of visual outcome, such as in the replacement of a scarred cornea. Indications for penetrating keratoplasty include keratoconus, pseudophakic or aphakic bullous keratopathy, graft failure, Fuchs’ endothelial dystrophy, graft rejection, corneal scars, chemical burns, corneal ulcers (bacterial, fungal, parasitic, or viral), corneal dystrophies and degenerations, herpetic keratitis, trauma, or any other causes of corneal decompensation. The rate of success of penetrating keratoplasty for the first four indications listed is excellent, but the chance of graft rejection increases significantly in instances of active or recurrent infection, inflammation, corneal vascularization, or previous graft rejection.

Because penetrating keratoplasty involves a significant amount of postoperative care, it is important to perform a careful preoperative evaluation and thoroughly discuss with patients the surgery, visual expectation, possible complications, and, in particular, the long process of postoperative care. The recipient must be prepared for lifelong management of the eye. In general,

 

 

 

 

Figure 63-9 Lamellar keratoplasty for peripheral corneal melt and perforation. A, Preoperative appearance of a patient who had a peripheral corneal melt and perforation (see arrows). B, Postoperative appearance after the placement of a horseshoe corneal scleral lamellar graft. (Courtesy of Dr WW Culbertson.)

important considerations for preoperative evaluation for penetrating keratoplasty are as follows:

• Evaluation of visual potential—a careful ocular history, which includes strabismus, amblyopia, glaucoma, and retinal and optic nerve abnormalities, is important to assess the best potential visual outcome of the surgery.

• Ocular surface abnormality—a variety of ocular surface diseases must be recognized and treated prior to penetrating keratoplasty. These include rosacea, dry eyes, blepharitis, trichiasis, exposure keratopathy, ectropion, and entropion.

• Intraocular pressure (IOP) must be controlled adequately prior to penetrating keratoplasty to ensure a successful surgical outcome.

• Ocular inflammation—both intraocular and ocular surface inflammation may compromise graft success. Inflammatory conditions such as uveitis must be recognized and treated, as these conditions markedly increase the chance of elevated IOP, macular edema, graft rejection, and failure. Patients who suffer from active infectious processes with an inflamed “hot” eye also have an increased risk of graft rejection or failure.

• Prior corneal diseases and vascularization—a history of herpetic keratitis significantly reduces the chance of graft success as a result of several factors, which include recurrent disease in the graft, vascularization, trabeculitis with increased IOP, and persistent inflammation that causes rejection.

• Peripheral corneal melting—corneal thinning and melting, such as that associated with rheumatoid arthritis, may significantly affect the surgical outcome of penetrating keratoplasty and thus must be treated adequately prior to the surgery. Corneal surgery in these eyes can be technically difficult. Surgical complications include irregular astigmatism because of peripheral ectasia and recurrent corneal thinning.

Donor Selection.

The Eye Bank Association of America has developed a set of criteria for donor corneas.[20] Contraindications for the use of donor tissue for penetrating keratoplasty include:

• Death of unknown cause;

• Central nervous system diseases, such as Creutzfeldt-Jakob disease, subacute sclerosing panencephalitis, rubella, Reye’s syndrome, rabies, and infectious encephalitis;

• Infections such as human immunodeficiency virus, hepatitis, septicemia, syphilis, and endocarditis;

 

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• Eye diseases such as retinoblastoma, malignant tumor of anterior segment, and active ocular inflammation (e.g., uveitis, scleritis, retinitis, and choroiditis);

• Prior ocular surgery (although pseudophakic eyes may be used with good cell densities);

• Congenital or acquired anterior segment abnormalities such as keratoconus and Fuchs’ endothelial dystrophy.

Prior to penetrating keratoplasty, donor blood must be evaluated for communicable disease and donor tissues inspected by the surgeon under the slit lamp. A new factor will be donors with previous corneal refractive surgery.

SURGICAL TECHNIQUES.

Because penetrating keratoplasty involves an “open sky” exposure of the intraocular contents, adequate decompression of the globe prior to penetrating keratoplasty is an important step as excessive preoperative IOP may increase the risk of expulsive choroidal hemorrhage. Intravenous mannitol or mechanical ocular decompression, such as with the Honan balloon, may be considered. Patients who undergo a simple penetrating keratoplasty have miotics placed preoperatively to protect the lens during surgery. Scleral supporting rings are used when the surgeon is concerned about ocular collapse during the procedure—principally in aphakic eyes. These rings are sutured to the sclera with 6-0 silk or Vicryl suture, with care taken to balance the suture positions and tensions. Inadvertent misalignment of the rings may result in an irregular trephination.

Using a caliper, the horizontal and vertical diameters of the recipient cornea are measured and the size of the graft is determined based on pathology and clinical judgment. Traditionally, a size disparity in which the donor tissue is 0.25?mm larger in diameter than that of the recipient is used. In certain circumstances, a larger (0.5?mm) donor, such as in a hyperopic eye, or a same size or smaller (0.25?mm) donor button, such as in a recipient with keratoconus, may be chosen judiciously. The center of the recipient cornea is marked with a marking pen. A radial keratotomy marker stained with ink may be used to mark the peripheral cornea. A paracentesis port is made with a No. 75 Beaver blade, followed by injection of viscoelastic material into the anterior chamber. If a sclerally sutured intraocular lens (IOL) is planned, the scleral flaps are made prior to trephination, and the IOL is prepared. Alternatively, the surgeon may choose not to use scleral flaps but instead simply to rotate the Prolene suture knot into the sclera.

Attention is directed to the donor tissue, and a donor corneal button is punched. Several systems are available for donor trephination, which include a handheld trephine, the universal punch, and the Katena trephine blade attached to a gravity corneal punch ( Fig. 63-10 ). These devices all cut the donor from endothelium to epithelium. In some of these systems, the epithelium may be marked prior to trephination to help with tissue distribution. The donor may also be cut from epithelium to endothelium with a system such as the Hanna artificial anterior chamber. This has the theoretical advantage that both the donor and recipient are cut in the same fashion with the same blade, which reduces donor-recipient disparity and potentially reduces astigmatism.

 

 

Figure 63-10 The corneal button is cut. A Katena blade mounted on a gravity punch may be used to cut the button from the endothelial side. (Courtesy of Dr WW Culbertson.)

The recipient cornea may be cut using a variety of trephines, such as the Hessburg-Barron suction trephine, Hanna trephine ( Fig. 63-11 ), Castroviejo trephine, and a number of other designs, such as the Lieberman single-point corneal trephine and the Grieshaber contact lens corneal cutter. The Hessburg-Barron suction trephine consists of a circular blade assembly that has a vacuum chamber attached to a spring-loaded syringe. The Hanna trephine has a unique, funnel-shaped design with a vacuum chamber created around a circular disposable blade. The Castroviejo trephine is made of a circular blade in a handle. Ideally, to achieve optimal graft-host tissue apposition, the trephination cut lies perpendicular to the corneal surface. Use of the Hanna trephine gives a reliably perpendicular profile. However, in instances in which the recipient ocular surface is not sufficiently large to accommodate the size of the Hanna trephine, the Hessburg-Barron trephine is used—it requires less surface area to achieve an adequate vacuum. The handheld Castroviejo trephine may be used for decentered grafts in which flexibility of orientation of the trephine is desired.

A partial-thickness trephination followed by a controlled entry into the anterior chamber using a No. 75 Beaver blade or a continued trephination that is stopped as soon as aqueous egress shows the anterior chamber has been entered may be performed. Suction is released the moment entry is noted. The recipient button is then excised using forceps and corneal scissors ( Fig. 63-12 ). Alternatively, the button is removed using a blade such as a No. 75 Beaver, with care taken not to traumatize the iris inadvertently. The edge of the recipient bed is made perpendicular for optimal graft-host apposition. The anterior chamber may be reformed using a small amount of viscoelastic.

Depending on the case, the patient may need cataract extraction, IOL explantation, anterior vitrectomy, or the placement of a new IOL ( Figs. 63-13 and 63-14 ). The donor button is placed over the recipient bed and sutured in place with four cardinal sutures (see Fig. 63-15 ). The depth of suture is typically 90% of the corneal thickness. Proper tissue distribution is paramount. It is beneficial to avoid a full-thickness pass, which may increase the chance of subsequent infection or epithelial downgrowth. After

 

 

Figure 63-11 Hanna suction trephine. The anterior chamber of the patient may be filled with viscoelastic material and trephination then performed. (Courtesy of Dr WW Culbertson.)

 

 

Figure 63-12 Excision of corneal button. The corneal button is removed completely using corneal scissors. (Courtesy of Dr WW Culbertson.)

 

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placement of the 12 o’clock suture, particular attention is paid to the 6 o’clock suture such that these two sutures follow a vertical line and bisect the entire donor button. The 3 and 9 o’clock sutures are similarly placed. The marks on the recipient sclera and donor tissue may serve as guides, but the surgeon must decide the best suture placement.

The rest of the sutures are a combination of interrupted and running sutures ( Fig. 63-16 ) or solely interrupted sutures. Interrupted sutures are suited for vascularized or thinned cornea as subsequent selective removal may be necessary to prevent the advancement of vessels or to control astigmatism. Running sutures, on the other hand, have the advantage of speedy placement intraoperatively and better tension distribution and healing. Prior to the completion of all sutures, the viscoelastic material in the anterior chamber is removed. The running sutures may be adjusted intraoperatively by using a keratoscope, such as the Hyde astigmatic ruler, to project a circular image onto the donor cornea. If the ring image is oval rather than circular, excessive tightness is indicated in one meridian and the running suture adjusted accordingly. When the graft sutures are completed, the security of the wound is tested by the injection of balanced salt solution into the anterior chamber; any fluid leak through the graft-host junction is sought. If a scleral-sutured IOL is used, the surgeon must ensure that the knots are either rotated and buried or covered by a partial-thickness scleral flap.

COMPLICATIONS AND POSTOPERATIVE MANAGEMENT.

Most of the intraoperative complications can be avoided by using adequate surgical planning and techniques. Possible intraoperative complications include poor graft centration, excessive bleeding, damage to ocular structures (such as donor endothelium, iris, lens, or posterior capsule), or expulsive hemorrhage. During the process of excision of the recipient button, it is imperative to monitor continuously the depth of the anterior chamber and the red reflex. A sudden shallowing of the anterior

 

 

 

 

 

 

Figure 63-13 Removal of anterior chamber intraocular lens. A, Care is taken when the anterior chamber haptics are removed, as they may become encysted in the peripheral iris and bleeding may occur on removal. B, An anterior vitrectomy is performed—an iris hook may be used to improve visualization. C, A 10-0 Prolene suture is passed beneath the iris and through the scleral sulcus and out through the previously prepared scleral flap. This is performed on both sides. (Courtesy of Dr WW Culbertson.)

 

 

Figure 63-14 Prolene suture passed through the sclera and tied under the flap. This is carried out after the suture supported lens has been placed in the sulcus. The Prolene suture is tied to itself beneath the scleral flap. Alternatively, the knot may be rotated beneath the sclera. (Courtesy of Dr WW Culbertson.)

 

 

Figure 63-15 The corneal button is placed. Care is taken in the placement of cardinal sutures to ensure adequate tissue distribution. (Courtesy of Dr WW Culbertson.)

chamber or disappearance of the red reflex may signify an impending expulsive choroidal hemorrhage. Having Cobo prosthesis available, which can be placed quickly on the recipient bed to seal the globe in the event of expulsive choroidal hemorrhage, is recommended.

The success of penetrating keratoplasty depends significantly on adequate postoperative care and management. The surgeon must be able to recognize and manage a variety of possible complications, such as wound leak and infection, glaucoma, and graft rejection or failure. The common postoperative complications and their management are discussed in the following subsections.

Wound Leak.

A shallow anterior chamber in a soft globe the day after penetrating keratoplasty may indicate a wound leak. Measures that can be taken to manage wound leak include patching, aqueous suppressant, lubrication, or bandage contact lenses. Significant wound leak that arises from either a broken suture or poor wound apposition may require the wound to be resutured.

Flat Anterior Chamber with Increased Intraocular Pressure.

Flat anterior chamber with increased IOP may result from pupillary block, anterior rotation of the lens-iris diaphragm (such as is found in choroidal hemorrhage), choroidal effusion, or malignant glaucoma. The cause must be identified and treated.

Endophthalmitis.

Postoperative endophthalmitis may result from a variety of factors, such as contamination of donor or host tissue or postoperative infection. It is a devastating complication that requires aggressive management, which includes aqueous and vitreous cultures, intraocular antibiotics, and possibly vitrectomy ( Fig. 63-17 ).

Persistent Epithelial Defect.

Typically, an epithelial defect after penetrating keratoplasty heals within 1 week postoperatively. Persistent epithelial defects occur in eyes that have ocular surface disorders, such as dry eye, blepharitis, exposure keratopathy, and

 

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Figure 63-16 Placement of a 10-0 running suture. (Courtesy of Dr WW Culbertson.)

 

 

Figure 63-17 Endophthalmitis. This was caused by Proteus infection 5 weeks following penetrating keratoplasty. (Courtesy of Dr RK Forster.)

rosacea, or in patients who have systemic diseases, such as diabetes or rheumatoid arthritis. Frequent lubrication with preservative-free drops and lubricating ointment is applied, and all possible causes of topical toxicity must be eliminated. If the problem does not resolve, a tarsorrhaphy and/or punctal occlusion may be necessary.

Primary Graft Failure.

Primary graft failure (which is different from graft rejection—see the following) is recognized when significant edema of the donor tissue in a noninflamed eye is present on the first postoperative day and does not clear. Primary graft failure may be attributed to either poor donor endothelial function or iatrogenic damage to the donor tissue during penetrating keratoplasty. The graft is observed for several weeks and a regraft considered if the corneal edema fails to resolve.

Problems Related to Sutures.

A variety of suture-related complications may occur after penetrating keratoplasty. If found, a loose or broken suture must be removed because it may result in vascularization or abscesses.

Graft Rejection.

Graft rejection remains the most common cause of graft failure. Alldredge and Krachmer[21] reported an overall incidence of endothelial graft rejection of 21%. Symptoms of endothelial graft rejection include pain, photophobia, redness, and decreased vision. Patients must be educated carefully with regard to these symptoms, and must seek medical attention immediately should they occur.

Graft rejection may be divided anatomically into three categories:

• Epithelial rejection—may be recognized by observation of an epithelial line, which represents the replacement of the donor epithelium by that of the recipient;

• Subepithelial rejection—multiple subepithelial infiltrates limited to the corneal graft may be observed ( Fig. 63-18 );

• Endothelial rejection (the most severe type characterized by keratic precipitates, iritis, and corneal edema)—a Khodadoust line may be seen, which represents the advancing front of the host immunological and inflammatory cells against a receding front of donor endothelium ( Fig. 63-19 ).

 

 

Figure 63-18 Subepithelial infiltrates secondary to subepithelial graft rejection. (Courtesy of Dr WW Culbertson.)

 

 

Figure 63-19 Graft rejection. Note the inflammatory precipitates and Khodadoust line secondary to endothelial rejection. (Courtesy of Dr EC Alfonso.)

The treatment of graft rejection consists primarily of topical corticosteroids. For epithelial graft rejection, the frequency of the corticosteroid drops is increased to hourly; endothelial graft rejection warrants frequent (hourly or more often) topical corticosteroid until the process is reversed. Subconjunctival injection of corticosteroid may also be used. Systemic steroids (oral or intravenous) may be utilized in severe cases but are usually not necessary.

Treatment for Astigmatism.

Adequate control of postoperative astigmatism is vital to achieve the best visual acuity possible. Typically starting at 6–8 weeks after penetrating keratoplasty, the patient is followed using serial corneal topography and interrupted sutures are removed selectively or a running suture adjusted as necessary to reduce astigmatism. The continuous 10-0 nylon sutures may be adjusted at the slit lamp postoperatively to reduce astigmatism.[22] Early removal of sutures may have a more significant effect on astigmatism, although care is required with regard to wound stability if sutures are removed too early. Astigmatic keratotomy may be performed late if a significant amount of residual astigmatism remains after all the sutures have been removed and the patient is intolerant of contact lenses.

Corneal Ulcers.

Patients who have undergone penetrating keratoplasty are more susceptible to infectious keratitis. Factors such as suture abscess and persistent epithelial defect may contribute to the development of corneal ulcers.

Recurrence of Diseases.

Various corneal dystrophies and infections ( Fig. 63-20 ) may recur in grafts. Among the three stromal corneal dystrophies (macular, granular, and lattice), lattice corneal dystrophy has the highest recurrence rate. In the setting of keratic precipitates on a graft in a patient who has a history of herpes simplex virus, it is sometimes difficult to distinguish recurrence of a disease from graft rejection. It is important, however, to make such a distinction as the treatment for recurrence of herpes simplex virus (antiviral agent) is different from treatment for rejection (corticosteroid). The observation of keratic precipitates and corneal edema confined only to the donor button may suggest a graft rejection.

 

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Figure 63-20 Herpetic keratitis recurrence in graft. Note positive staining with rose bengal. (Courtesy of Dr EC Alfonso.)

Triple Procedure (Combined Procedure)

PREOPERATIVE EVALUATION AND DIAGNOSTIC APPROACH.

A combined procedure or triple procedure refers to penetrating keratoplasty, cataract extraction, and IOL implantation. The procedure is indicated for patients who have visually significant cataract and who require penetrating keratoplasty for visual rehabilitation. The leading indication for a triple procedure is Fuchs’ endothelial dystrophy, which accounts for up to 77% of eyes that require a triple procedure. [23] [24] [25] [26] Other indications for triple procedures include corneal leukoma, keratoconus, herpes simplex infection, and interstitial keratitis.

Compared with penetrating keratoplasty, a combined procedure requires the additional, appropriate calculation of the power of the IOL required to achieve the optimal refractive result. The authors use the Sanders-Retzlaff-Kraff formula ( Equation 1 ),[27] in which A is the constant for an IOL, AL is the axial length, and K is the keratometric measurement. The determination of K varies from surgeon to surgeon. The authors normally advocate one of two alternative approaches. Either the average of the past postoperative keratometric readings associated with the surgical technique or the K reading from the contralateral eye is used for IOL calculation. In the instances in which an over- or undersized graft is required, 1–2D is subtracted from the IOL power for a 0.5?mm oversized graft or 1–2D is added to the IOL power for 0.5?mm undersizing.[19]

 

 

 

SURGICAL TECHNIQUES.

The detailed surgical technique for penetrating keratoplasty is as described previously. The additional components of the surgery related to cataract extraction and IOL implantation are described here. After the recipient button has been excised, a can-opener type of anterior capsulectomy, a continuous curvilinear capsulorrhexis, or a square capsulectomy using Vannas scissors may be performed. The capsulectomy must be sufficiently large to allow subsequent expression of the lens nucleus. Care is taken during the capsulorrhexis because the lens-iris diaphragm is rotated anteriorly with an open-sky eye. No counterpressure is used on the anterior chamber to keep the anterior capsule flat, and thus the capsulectomy tends to extend peripherally if excessive IOP or insufficient use of preoperative mannitol occurs.

After hydrodissection using balanced salt solution and mobilization of the lens nucleus, the lens is expressed gently using pressure at the 6 o’clock position to tilt the superior or inferior edge of the lens anteriorly above the plane of the anterior capsular opening. The lens is rotated out using a No. 25 gauge needle or a lens loop. The remaining cortical material is removed using a manual irrigation and aspiration device, which must be carried out carefully because the anterior and posterior capsules tend to collapse together. The posterior chamber is then inflated with viscoelastic material and the appropriate posterior IOL is inserted using a lens forceps. In the event that a posterior capsular tear and anterior extension of vitreous occur, a limited anterior vitrectomy is performed and the IOL either inserted in the bag or sulcus or sutured to the sclera, depending on the available capsular support (see Figs. 63-13 and 63-14 ). An open-loop anterior chamber IOL may also be used. The remainder of the procedure for penetrating keratoplasty is the same as that described in the appropriate sections earlier. Phacoemulsification is often difficult to perform because it requires a clear view through the cornea, which is rarely the case in patients undergoing a triple procedure.

COMPLICATIONS AND POSTOPERATIVE MANAGEMENT.

Intraoperative complications of a triple procedure include capsular rupture with vitreous loss and suprachoroidal hemorrhage. Postoperatively, the complications associated with penetrating keratoplasty (as described earlier) are possible, which include failure and graft rejection, postoperative glaucoma, endothelial cell loss, cystoid macular edema, retinal detachment, and endophthalmitis.[23] [26] [28] [29] [30] In addition, posterior capsular opacification in combined procedures can occur with an incidence similar to that in routine extracapsular cataract extraction alone. [31]

OUTCOMES

Corneal grafting techniques, such as penetrating keratoplasty, lamellar keratoplasty, and triple procedures, have become reliable and popular surgical techniques. Patients who undergo these types of surgery achieve significantly improved vision in the majority of cases. Careful attention to preoperative evaluation, surgical techniques, and postoperative management will improve surgical outcome and patients’ satisfaction.

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