Penetrating keratoplasty (PK) is one of the most common forms of tissue transplantation currently performed. It can be an extremely successful procedure, with dramatic visual improvement for the patient. However, it can also be one of the most challenging and frustrating procedures for a patient to endure, with a prolonged convalescence, delayed visual improvement, and many postoperative challenges. The technique of keratoplasty, or corneal grafting, involves removing the dysfunctional elements of the cornea and replacing those elements with healthy tissue. Full-thickness keratoplasty is termed penetrating keratoplasty, and partial-thickness keratoplasty is termed lamellar keratoplasty.

The current number of procedures performed on an annual basis is increasing slightly; according to the 2009 Statistical Report of the Eye Bank Association of America (EBAA), a total of 42,606 corneal transplants were performed in 2009, a 2.3% increase from 41,652 in 2008.¹ The total number of penetrating keratoplasties continues to decline for the fourth straight year, from 32,524 in 2008 to 23,269 in 2009. Of note, this decline may be exaggerated because the 2009 data are for tissue used domestically, whereas prior data included tissue used by both the United States and internationally. The decrease in number of PKs has coincided with an increasing number of endothelial keratoplasty (EK) procedures, of which 18,221 surgeries were performed in 2009. The decline in number of PKs from the 1980s also reflects the decrease in incidence of pseudophakic corneal edema (PCE) (Fig. 26-1) and aphakic corneal edema (ACE). This trend most likely reflects improvements in cataract removal technique, such as small-incision phacoemulsification, and intraocular lens (IOL) technology, including modifications in anterior and posterior chamber IOL designs. More recently, the percentage of PKs performed to treat PCE has remained relatively stable (from 14% in 2008 to 15% in 2009).

The indications for PK have shifted over the past several decades. Keratoconus (Fig. 26-2) and ACE were the most common indications prior to 1980, whereas PCE was the most common indication from 1980 through 2002.² In 2009, the leading indications for PK were keratoconus and other causes of corneal opacification or distortion, followed by repeat corneal transplant (regrafting). PCE was the fourth leading cause for PK, as it was in 2008 and 2007.²

Patel et al³ examined the incidence and indications at a major university setting in the northeastern United States and noted that the incidence of regraft was increasing. The number of regrafts increased from 9% to 16%, comparing the years 1983 to 1988 with 1989 to 1995, respectively. Within the regraft category, the number of multiple regrafts had also increased (11% from 1989–1991, jumping to 29% from 1992–1995). Regrafting and multiple regrafting were associated with an increased failure rate during the study period. A subsequent study at the same institution by Cosar et al⁴ showed that the incidence of regraft had increased to 18.1% from 1996 to 2000. The leading indications in their study population also included PCE (27.2%), keratoconus (15.4%), and Fuchs’ endothelial dystrophy (15.2%). Differing incidences of regraft have been noted in other reports.^5,6,7 One analysis noted only an 8.7% incidence of regraft.⁸ In this population, keratoconus (rather than PCE) was the leading indication for transplantation (45.6%).

With regard to availability of tissue, the transplant surgeon enjoys a relative abundance of donor corneal tissue, so the waiting-list experience endured by other transplant candidates (e.g., kidney or heart transplant) does not occur for the corneal transplant patient, with few exceptions. A total of 107,289 total whole globes and corneas were donated in 2009, with 94,852 recovered with intent for surgical use. The pool of suitable donor corneas may decrease in the future given the increasing incidence of refractive procedures. Donor screening (in the form of potential donor questionnaires and eye tissue analyses to detect evidence of prior refractive surgery) will likely become more important as the popularity of these corneal refractive procedures continues to increase.^9,10,11

The prognosis for graft clarity can be divided into four groups (Table 26-1). This grouping system takes into account wound healing ability, presence of vascularity at the graft–host junction, and underlying infectious processes. Keratoconus, in group 1, has an excellent prognosis for graft clarity and may account for the lower total number of regrafts reported by Edwards rt al.⁸ Most PKs are performed for optical indications, so as to improve vision by removing an optically opaque or dysfunctional cornea. Tectonic (to preserve globe integrity), therapeutic (to remove progressive conditions, such as an expanding fungal infiltrate), palliative (to improve comfort in a painful eye with bullous corneal edema), and cosmetic (to improve appearance in a blind eye) indications are less frequently encountered reasons for transplantation.

A complete patient and family history must be taken, including vision prior to onset of symptoms, presence of amblyopia, timing of prior surgery, medical treatments of the underlying condition, current ocular and systemic medications, presence of glaucoma, presence of systemic illness, and vision in the contralateral eye. The patient’s desire and ability to adhere to a prolonged postoperative course must be ascertained. A social work consultation can be extremely helpful to this end. Family and/or supportive caregiver situation, transport access, ability to receive help with administration of medications if necessary, and patient motivation can help determine the likelihood of patient compliance. Previous medical records from referring physicians detailing prior ocular health, phakic status, prior medical treatments, and prior ocular surgery can be helpful.

A complete ocular examination must be performed by the surgeon to determine prognosis and to identify factors that may need to be addressed at the time of transplantation. Preoperative visual acuity, as well as rigid gas-permeable contact lens refraction for selected patients, such as those with keratoconus or central scarring, are measured. Intraocular pressure (IOP) and gonioscopy, if possible, are performed, with the knowledge of current medications and potential need for concomitant glaucoma tube shunt surgery. Given the potential exposure to long-term corticosteroid use and possible steroid sensitivity, the possibility and status of glaucoma must be addressed. The presence or absence of a relative afferent pupillary defect in the operative eye is also documented, which is especially helpful in the glaucomatous or traumatized eye.

The patient’s underlying corneal disorder or disorders are identified during slitlamp examination. The status of the limbus and presence of corneal neovascularization or conjunctivalization is noted. This may aid in the evaluation of stem cell function and re-epithelialization potential after transplantation. Ocular surface disease, as seen in patients with limbal stem cell deficient processes (e.g., alkali burns, Stevens-Johnson syndrome, and aniridia), can be associated with impaired healing and may require adjunctive therapy at the time of corneal transplantation. In addition to limbal stem cell deficiency, abnormalities of the tear film and decreased mucin production (as seen in ocular cicatricial pemphigoid, Stevens-Johnson syndrome, and chemical burns) present a relative contraindication to PK. Adequate ocular lubrication is essential to the proper healing and functioning of a corneal graft. In these select patients, it has been found that limbal stem cell transplantation and systemic immunosuppression combined with penetrating keratoplasty has been a successful approach to ocular surface rehabilitation. Keratoprostheses, which replace diseased corneal tissue with an integrated clear plastic device, have also been used to improve visual function in patients with severe limbal stem cell deficiency and are addressed fully in a separate chapter.

The centration and extent of corneal pathology are noted, and the graft size needed to treat the condition is estimated. The Haag-Streit slitlamp is equipped with a variable-height beam, and this beam is helpful in estimating the size of corneal lesions.

The patient’s lenticular status is also very important in the preoperative evaluation. The presence of an anterior chamber lens and its role in possible contribution to the need for transplantation should be determined, with possible lens removal or exchange at the time of transplantation. If the patient is phakic, lenticular opacity is assessed, being aware that corticosteroid use in the postoperative period may hasten the progression of a cataract. Therefore, combined corneal transplantation, lens removal, and intraocular lens placement (“triple procedure”) may be considered. If lens removal and exchange are indicated, axial length measurement is performed.

Ocular inflammation must be controlled prior to consideration of surgery. The presence of anterior chamber cell and flare, keratic precipitates, peripheral anterior synechiae (PAS), and posterior synechiae are noted. In addition to controlling inflammation, inciting agents must also be identified and addressed. Herpetic eye disease, including active epithelial and/or stromal inflammation, must be adequately treated and controlled, and we recommend a time interval of at least 6 months prior to consideration of keratoplasty in these eyes.

Eyelid function and presence of scarring are noted, especially in the patient with concomitant ocular and facial burns. Inadequate lid closure and lagophthalmos can result in corneal drying and exposure, thereby placing the graft at increased risk. Patients with advanced corneal scarring and cicatrization of the fornix are also at risk for exposure keratopathy. Excessive ectropion or entropion with trichiasis can oftentimes be adequately treated by oculoplastic consultation and surgical repair. A prerequisite to oculoplastic surgical assistance, though, is control of ocular and conjunctival inflammation. Lid margin telangiectasia, meibomian gland dysfunction, lid margin hypertrophy, and other signs of rosacea are noted and treated to decrease inflammation and potential stimuli for limbal neovascularization.

Retinal status must be evaluated but may be limited by the view to the posterior pole through a diseased cornea. Contralateral retinal examination may yield information regarding glaucoma, macular degeneration, and overall retinal status. If the view is unsatisfactory, B-scan ultrasonography is indicated.

Informed consent to the procedure is obtained only after a frank discussion with the patient (and his or her family members or caregivers, if the patient so desires). The transplant surgeon should take time to discuss the diagnosis, risks, and potential complications, benefits, alternative treatment options, and details of the procedure and postoperative care. The prolonged convalescence, realistic expectations regarding visual recovery, and the timetable for possible recovery are key points in the discussion. It is important to mention the potential need for rigid gas-permeable contact lens wear to treat postoperative anisometropia and irregular astigmatism and to identify the patient’s (and/or caregiver’s) ability to handle such a lens. Dedication and commitment to follow-up examination must also be stressed. Again, social work evaluation can be helpful in gauging both the patient’s and the family’s understanding of the procedure and of the follow-up care needed for keratoplasty patients.

Penetrating keratoplasty has been found to be a safe procedure based on the patient’s overall medical health and can often be performed using regional anesthesia. At our institution, topical fluoroquinolone antibiotic drops are given every 5 minutes for three drops total preoperatively as a prophylactic measure. In phakic patients undergoing PK only, pilocarpine 2% is given every 5 minutes for three drops total to produce a miotic pupil, thus protecting the lens. Posterior chamber pseudophakic eyes also receive pilocarpine to maintain lenticular position.

In older patients, or in those with higher intrathoracic pressures (such as individuals with stout necks), intravenous mannitol 20% is given preoperatively. Prior to administration, it is essential for the anesthesia staff to assess the patient’s overall medical status. Mannitol acts as an osmotic diuretic to help deturgesce the vitreous and thereby decrease posterior vitreous pressure. In combined (keratoplasty and cataract extraction) cases, it may be prudent to place a condom-style catheter on male patients and to have a bedpan ready due to the added length of the case. A Honan balloon can be placed on the eye and inflated to a pressure of 30 mm Hg for 10 minutes, or digital massage can be performed to lower IOP. In combined procedures, we also use the cycloplegic-mydriatic combination of cyclopentolate hydrochloride 1%, phenylephrine 5%, and tropicamide 0.5% one drop every 5 minutes for three doses total for pupil dilation.

There are multiple accepted ways of performing penetrating keratoplasty, and it continues to be an evolving procedure. Surgeons may use various techniques in achieving the same goal of a successful transplant and improved visual acuity for the patient. We will present one such approach to the procedure, and we recognize that there are many other acceptable and successful approaches. We will also discuss penetrating keratoplasty in the aphakic and pseudophakic patient, as well as concurrent PK, lens removal, and intraocular lens placement.

Patient positioning is a vital step in ensuring patient comfort for a relatively lengthy procedure while maximizing surgeon access. A tense, uncomfortable patient is apt to move unpredictably during the procedure, and even the most cooperative patient may experience fatigue and strain, resulting in a Valsalva maneuver. This can lead to a rise in posterior pressure, increasing the likelihood of anterior chamber shallowing, vitreous loss, and even suprachoroidal hemorrhage. By placing the head of the bed slightly higher than the foot of the bed in a reverse-Trendelenburg position, posterior pressure can be minimized, especially in obese patients with increased intrathoracic pressure. Also essential is surgeon comfort; the surgeon should also have direct access to both a preparation table and the patient. Placing the microscope height at a level to keep the surgeon’s back and shoulders erect can help minimize surgeon fatigue. A wrist rest can be used to aid in surgeon comfort, by providing a place to rest one’s hands. It can also aid in patient comfort, by minimizing pressure placed by the surgeon on the forehead and neck. A wrist rest also improves stability and helps minimize the possibility of inadvertently applying pressure on the globe or orbit during the procedure. At some surgical facilities, an ergonomist is available to examine ideal heights for microscope, bed, and wrist rest placement. A good general rule to follow is that a more comfortable position can be maintained for longer periods of time, thereby lessening fatigue.

Adequate anesthesia is also important in maintaining patient comfort. Both general and local regional anesthetics can be used in penetrating keratoplasty. Pediatric or uncooperative patients as well as those with tremors, claustrophobia, high level of anxiety, or a history of ocular trauma with possible penetrating injury, are all candidates for general anesthesia. Most patients with nontraumatic indications for PK, however, can receive adequate anesthesia and akinesia with a local regional approach. After the administration of mild intravenous sedation by the anesthesia team while in the operating room, a local lid block and retrobulbar block can be performed. Local anesthesia consists of both retrobulbar block and lid block, such as an O’Brien or Van Lint block, to minimize orbicularis function and to decrease the risk of elevated intraorbital pressure while the globe is open. An O’Brien lid block, which consists of a 3- to 5-cc injection of an equal mix of lidocaine 2% and bupivacaine 0.75% into the orbicularis muscle along the inferior and superior orbital rim, can provide adequate lid akinesia, minimizing the posterior pressure that can occur with a vigorous lid squeeze. Retrobulbar anesthesia, consisting of 3 to 5 cc of the same mix of lidocaine and bupivacaine, can provide excellent pain control and minimize globe movement during the procedure. It is important to withdraw the plunger on the syringe immediately prior to administering the block to identify inadvertent vascular canalization. Also, monitoring the globe position by retracting the upper lid (often done by an assistant) helps to minimize the risk of optic nerve trauma. It is important to not inject too large an amount of retrobulbar anesthetic, as this increase in orbital volume can result in increased posterior pressure. After the retrobulbar block, ocular massage, if the globe is intact, can be performed. Alternatively, a Honan balloon, which consists of an inflatable chamber applied over the eye and secured with an adjustable headband, can be placed for several minutes. The eyelids and skin around the eye are then cleansed with Betadine antimicrobial solution. In the setting of Betadine allergy, benzalkonium chloride can be used as an alternative. A fenestrated drape is then placed over the operative eye. Various lid specula have been devised for penetrating keratoplasty; a common goal in all of these devices is maximal exposure with minimal pressure on the globe. A locking lid speculum, such as a Maumenee-Park speculum (Fig. 26-3), with adjustable fissure width and blade angulations, is suitable for PK because it minimizes globe pressure. Positioning the head and neck so as to make the plane of the visual axis perpendicular to the floor and to the operating microscope is exceedingly helpful in establishing a symmetric trephination and in placing corneal sutures.

In preparing the eye for trephination, the use of a scleral fixation ring, such as a Flieringa ring, sized to a diameter slightly larger than the corneoscleral limbal junction, can be helpful in maintaining the form of the globe. Although we do not routinely use these rings in adults, we have found scleral fixation rings to be helpful in the pediatric population, where, oftentimes, the globe and sclera are soft and easily distensible. This ring is secured with a series of 7-0 Vicryl sutures and is removed at the completion of the procedure. A caliper, such as a Castroviejo caliper, is used to measure the corneal diameter and the diameter of trephination needed to clear the visual axis. Paton¹² considered the ideal graft size to be between 6.5 and 9.0 mm. The smaller the trephination, the greater the distance from limbal vascularity and from the drainage structures in the angle. Therefore, the risk of rejection of a smaller graft may be lessened, in theory, given the greater distance from the peripheral limbal vasculature and the resultant immunologic response to the donor tissue. Also, by increasing the distance from the angle structures, the risks of surgeon-induced secondary angle closure, PAS, and iris incarceration are theoretically lessened. However, a smaller-diameter graft is more susceptible to decentration and higher amounts of surgically induced astigmatism. We have found that, for most patients, the visual axis may be cleared with host trephinations of 7.5 to 8.0 mm. There are instances, such as infectious keratitis and peripheral corneal melting, in which an oversized therapeutic graft is indicated. Keratoconus patients with significant peripheral and inferior thinning may also benefit from a larger trephination. We often mark the visual axis with a methylene blue marking pen to help determine centration and trephine placement. Some surgeons prefer to slightly decenter the graft inferonasally so as to approximate the usual functional visual axis. The corneal periphery is marked with an eight-blade radial keratotomy marker, and these marks can be extended manually with a methylene blue marking pen to maintain orientation and identification of the corneoscleral limbal junction. These marks should extend beyond the trephination diameter, so as to help guide the radial placement of the transplant sutures. In maximizing the radial orientation, postoperative wound torque can be minimized, with a possible reduction in postoperative astigmatism. The operative microscope light is then turned off, the light source obturator is engaged, or a corneal light shield is placed on the cornea to minimize potential photic injury to the macula. The trephination of the host cornea is performed only after the preparation of the donor corneal tissue. Therefore, at this point in the procedure, attention is turned to the donor tissue.

The donor corneal tissue is now commonly available in Optisol preservative media and placed in a viewing chamber. The tissue endothelial cell count, infectious disease status (including human immunodeficiency virus, hepatitis B and C virus, and syphilis), and overall epithelial status are reviewed prior to trephination. This information is typically shared by the supplying eye bank with the transplant surgeon 24 hours prior to the procedure, with acceptance or rejection of the tissue based on the individual patient’s needs. A higher endothelial cell count is often desirable in a younger patient, whereas a lower endothelial cell count may be acceptable for a therapeutic tectonic graft (in which the need for repeat transplantation for optical improvement is more likely). Also, the donor tissue is visually inspected by the surgeon at the slitlamp for confirmation of tissue quality prior to the procedure, noting epithelial and endothelial quality and overall graft appearance. The donor tissue identification, patient identification, and operative site are confirmed with the operating room staff, and the donor tissue container is opened. The lid to the viewing chamber is removed, and the surgeon grasps the edge of the sclera with 0.12-mm Castroviejo forceps. An assistant then pours the Optisol solution into a sterile stainless steel specimen cup. Excess Optisol is removed by touching a methylcellulose sponge perpendicularly to the edge of the scleral rim, being careful to avoid touching the endothelial donor surface. By removing the excess fluid, the potential for graft slippage during trephination is minimized. The donor tissue is then centered on a trephination platform. We now use the UltraFit Coronet Donor Punch Set to trephine the corneal donor button. There are several other trephination systems available, including the Hannah, Katena, Hessburg-Barron, and Iowa PK Press systems, in addition to freehand manual trephination, which can also be used to prepare the corneal button. The donor tissue is routinely oversized by 0.25 mm compared to the host trephination for most transplants. Donor tissue is sometimes oversized by 0.50 mm in patients with shallower anterior chambers, anterior chamber intraocular lenses, and aqueous tube shunts. The donor trephine diameter is confirmed and then the donor trephine cylinder is engaged and pressed firmly against the trephination platform. This trephination is done in a careful but brisk fashion to minimize endothelial crush artifact. A distinctive, firm end point is felt (“crunch” sensation), and the trephine is removed while the donor rim is grasped using 0.12-mm Castroviejo forceps. By oversizing the donor tissue by 0.25 to 0.50 mm, tissue apposition is maximized. In patients with keratoconus, in an effort to minimize postoperative myopia, the host and donor trephination may be of equal size, depending on the trephination system. After the trephination, a few drops of filtered Optisol solution are placed on the endothelial surface to prevent desiccation of the donor graft. The donor rim and Optisol solution can then be cultured for bacteria and fungi. The donor tissue is then set aside on a table in a safe location.

After the donor corneal tissue is safely secured, attention is then returned to the host cornea. Multiple host tissue trephines are available, and we have found success using the Hessburg-Barron vacuum trephine system. This trephine includes a central crosshair to help align trephination. The position of the trephine is stabilized using a manual vacuum system, which is activated by a handheld syringe. The diameter is confirmed by reading the printed mark on the top edge of the trephine. The blade is advanced completely by turning the trephine in a clockwise direction. A moistened fluorescein strip is then gently touched to the bottom of the trephine. The trephine is then centered on the host tissue by aligning the central crosshair with the previously placed central mark on the host cornea. The trephine is then gently touched to the corneal epithelium in a perpendicular fashion so as to leave an impression of fluorescein. The trephine is removed, and the centration of this marking is evaluated. Adjustments in the orientation of the trephine can then be made. The blade is then retreated in the trephine housing until it becomes flush. This step is done under direct visualization. Three turns of one-quarter rotation are then performed to draw the blade up into the housing. The vacuum syringe plunger is depressed, and the trephine placed onto the host cornea, making any adjustment of centration as is warranted. The plunger is then released rapidly, and the vacuum level is assessed. A satisfactory vacuum level is generally indicated by a vacuum of 4.5 cc or less on the 5-cc syringe, and can also be noted by spontaneous trephine adherence to the cornea and host globe movement with gentle lateral pressure on the trephine. The centration is examined by viewing the crosshair and by estimating the distance from the corneoscleral limbal junction to the trephine. This estimate is done by viewing the trephine from the sides and without aid from the operating microscope. On confirmation of centration, the edge of the trephine is grasped and a total of 10 turns of one-quarter rotation are performed (with each one-quarter turn representing approximately a 60-μm-depth cut). The trephine chamber is closely monitored, and, if any aqueous egress is noted (signifying full-thickness trephination and entrance into the anterior chamber), the trephination is halted, vacuum is released, and the trephine is removed. Early entrance into the anterior chamber may be more common in patients with ectatic disorders such as keratoconus or in patients with prior inflammation and corneal thinning.

Once the trephine is removed, it is helpful to verify the depth of trephination by tracing the edge of the incision with smooth forceps. If any corneal vascularity is present, phenylephrine 2.5% can be touched to the areas affected, using a moistened methylcellulose sponge. Limbal cautery should be used sparingly as thermal injury may distort the corneal tissue. The trephined host tissue is grasped by 0.12-mm Maumenee-Park forceps (Fig. 26-4), and tension is gently placed toward the center of the cornea to expose the deepest extent of the trephination. A sharp 15-degree straight blade is used to enter perpendicularly into the anterior chamber, making the motion of the incision away from the surgeon. Care is also taken not to enter too deeply to avoid touching the iris or lens. The incision is extended 1 to 2 clock hours. Viscoelastic material is placed into the eye to deepen the chamber to provide space into which the blades of corneal scissors can be safely placed. Katzin curved corneal transplant scissors curved to the right and to the left are used to complete the excision of the host tissue. The blades are held parallel with the trephination to minimize asymmetric tissue overlap. The scissors are gently elevated as the blades are engaged, and the iris structure is monitored to avoid iris incarceration and trauma. Also, to help maintain tension in the area cut by the scissors, the host button is grasped 180 degrees from the site of the cut. This tension is especially helpful at the end of the tissue removal, when only 1 to 2 clock hours remain. Peripheral anterior synechiae can be lysed with a cyclodialysis spatula after the removal of host tissue.

The host tissue is set aside and, on completion of the procedure, sent to pathology for histologic examination and special staining as warranted by the indication for corneal grafting. Until the donor tissue is securely sutured into place, however, the original host tissue should be available, in case it is needed to close the eye. Also, a temporary keratoprosthesis, such as the Cobo keratoprosthesis, should be available to help maintain the integrity of the globe. At this point of the procedure (i.e., when the host cornea is being removed and the globe pressure is equal to atmospheric pressure), the risk of suprachoroidal hemorrhage is greatest. This potentially devastating complication is caused by the rupture of a choroidal vessel, which results in rapid and uncontrolled bleeding in the suprachoroidal space. The hemorrhage may force the iris, lens, vitreous, retina, and other intraocular contents to prolapse out through the corneal trephination wound. Risk factors for suprachoroidal hemorrhage include previous intraocular surgery, elevated IOP, myopia, advanced age, and arteriosclerotic disease. Patients with large body habitus may be prone to increased intrathoracic pressure and may generate additional posterior pressure. These patients may be best approached with general anesthesia. Intraoperative risk factors include rapid decompression of IOP on entry into the anterior chamber, Valsalva maneuver performed by the patient at the time of trephination, or compression and occlusion of the endotracheal tube resulting in a mechanical Valsalva maneuver. Management of a suprachoroidal hemorrhage is based on when it occurs during the procedure.¹³ Rapid recognition and response afford the best chance of salvaging the eye. If the hemorrhage occurs on initial entry into the anterior chamber, the host cornea is sutured back into place, using 8-0 silk or 9-0 nylon sutures, which not only are easier to visualize and tie in rapid sequence but also have greater tensile strength than 10-0 nylon sutures. Drainage of the hemorrhage can be accomplished by entering into the choroidal space by making a sclerotomy. If the hemorrhage occurs after the host cornea has been removed, the temporary keratoprosthesis is quickly placed into the wound to compress the hemorrhage and to keep intraocular contents in their correct anatomic positions. Our routine during host tissue removal is to have the assistant hold the temporary keratoprosthesis for rapid placement, and the assistant returns it to the instrument table only when all four cardinal sutures have been placed and tied. In the absence of a temporary keratoprosthesis, a surgeon may use his or her finger to tamponade the hemorrhage. Pressure is maintained until the hemorrhage stabilizes. Sclerotomy can be performed to drain the suprachoroidal hemorrhage, and then the donor or host tissue is sutured into place. Alternatively, sclerotomy and drainage of the suprachoroidal hemorrhage can be done at a later date if the intraocular contents can be successfully reposited at the time of surgery. If possible, irrigating fluid can be placed into the anterior chamber via keratoprosthesis attachment or anterior chamber maintenance port. This fluid can help deepen the anterior chamber, resulting in more anatomic orientation of intraocular contents and may also facilitate evacuation of the hemorrhage.

On successful entry into the anterior chamber and removal of the host tissue, the donor tissue can then be secured to the patient. We will describe standard phakic keratoplasty and will then discuss specific situations, such as combined keratoplasty and cataract removal and also keratoplasty in the pseudophakic patient. Up to this point in the description of the procedure, the steps taken for combined procedures are similar to those in standard phakic keratoplasty.

If the host cornea is not vascularized, a running suture technique can be used (Fig. 26-8). We often use an 8-bite interrupted and 16-bite running combination, but various techniques can be used effectively. One alternative is a 12-bite interrupted and 12-bite running combination, and another is a 20- to 24-bite single running suture. Each provides the opportunity for modification of astigmatism in the postoperative period; the 12 and 12 combination provides selective interrupted suture removal whereas the running suture allows adjustment of local suture tension. We will first describe the 12 and 12 technique in which we use an Alcon CU-5 4-mil needle with 10-0 nylon for the interrupted sutures. In this technique, a 12-blade radial keratotomy marker is used to mark the peripheral cornea prior to trephination. The first suture is placed at the 12 o’clock position. The sutures are placed using the method described in the section on simple penetrating keratoplasty, proceeding to the 6 o’clock, 9 o’clock, and 3 o’clock positions, and then to all 12 clock-hour positions, alternating suture placement at 180 degrees to the previously placed suture.

It is at this point that we take what is the last of a series of intraoperative steps designed to minimize astigmatism. Before placing the running suture, we perform qualitative keratoscopy using a von Luhnen keratoscope. Other methods may be employed, such as the use of a circular metal loop on a handle (Fig. 26-10), or an operating microscope-mounted qualitative keratometer. The Flieringa ring, if present, is removed. Intraocular pressure is adjusted by filling the anterior chamber. The keratoscope or wire loop is held about 2 cm directly above and parallel to the plane of the cornea. Irrigation of the graft will smooth the surface enough to see a reflection of the loop on the cornea. Most commonly, the reflection is ovoid, which indicates astigmatism of the graft; the short axis represents the steepest curvature of the cornea. Suture tension is adjusted by loosening or tightening the slip knots. Keratoscopy is repeated with additional suture adjustment as needed to minimize the corneal astigmatism. When the adjustments are completed, a final throw is placed on each suture and the knots cut short with Vannas scissors. Burying the knots in any type of corneal surgery is essential. The knots are buried into the donor stroma in an attempt to keep them as far away from any vascularization as possible. Anteroposterior graft–host disparity in alignment can also induce astigmatism and should be identified. Sometimes a meridian is flat because the donor is anteriorly displaced or steep secondary to posterior displacement. Resuturing is then necessary to correct the problem. It is not uncommon to inadvertently take superficial bites on the recipient side when suturing away from oneself.

The running suture is then placed, starting on the graft side at the 11:30 position. We use 10-0 nylon on an Ethicon Ultima CS 160 6-mil needle. The needle is passed radially through the graft and host, and about 10 cm of length is pulled up to allow for completion of the running suture. Each successive pass is taken halfway between the interrupted sutures, moving in a clockwise direction, taking care to create radial, deep, and equal-length bites. After the 10:30 pass, the needle is left in place and the exit track is expanded using a 15-degree steel blade as noted in the simple PK section. The two ends are cut about 3 cm long and a single two-loop throw is placed. Slack is then taken up from the running suture with microtying forceps by starting at one side of the knot and working back around the graft. Excessive tightening should be avoided. The suture is then tied with two square knots, and the ends are cut short. The knot is rotated to lie in the graft stroma, trying not to incarcerate it within the graft–host interface. While the anterior chamber is slowly refilled with balanced salt solution, the iris is observed to drop back away from the cornea. Any areas of iris incarceration or synechiae are released by introducing a cyclodialysis spatula through the wound 2 clock hours away from the area of concern. It is then passed over the iris peripheral to the incarceration and gently swept centrally to pull the iris from the graft–host interface. The chamber is again re-formed and the eye is dried with cellulose sponges. High magnification is used to look for the presence of any wound leaks, which, if present, are to be closed with single superficial 10-0 nylon sutures.

Another suture technique that allows earlier and possibly more significant adjustment of postkeratoplasty astigmatism is the use of a single running 10-0 nylon suture, as described by McNeill and Wessels²⁷ and by Van Meter et al.²⁸ Other surgeons have had considerable success with this technique and use it to reduce and initially stabilize astigmatism within 4 to 10 weeks after keratoplasty in most patients. Spectacle correction can be prescribed much earlier than with other techniques, thus providing visual rehabilitation to patients, many of whom are elderly. The advantages of astigmatism adjustment are balanced by the risk of reliance on a single suture for graft apposition and the flexibility of suture removal in interrupted techniques in the setting of peripheral neovascularization.