topography. Selective suture removal, the process of removing some sutures while leaving others intact, is one way of managing post-keratoplasty astigmatism. Sutures are removed in the steep topographic or refractive meridian until a desirable visual acuity is obtained. Sutures are removed until the patient obtains a desirable visual acuity. If the patient achieves a good visual acuity with less than 3D of refractive astigmatism, and some sutures remain in the graft, these remaining sutures are not removed. The patient can then be Þtted with spectacles or a contact lens.

4.1.8.1Postoperative Immunosuppressive Regimen

The postoperative topical immunosuppressive regimen will vary among surgeons, but the authors prefer to use a combination of topical prednisolone and topical cyclosporine A (Restasis, Allergan). In general, topical prednisolone is prescribed 4Ð8 times daily for an average of 2Ð3 months postoperatively. The prednisolone is tapered by one drop per month until a dose of once daily is obtained. At that time, if the patient is phakic and has experienced no rejection episodes or developed an IOP steroid response, the topical steroid is changed to loteprednol (Lotemax, Bausch & Lomb, Tampa, FL) one to two times per day. The patient is maintained on a minimum of one drop per day for at least 1 year. All patients receive topical cyclosporine A (Restasis, Allergan) twice a day for at least 1 year postoperatively. Many patients remain on topical immunosuppressive medication for an indeÞnite time period.

4.1.9 Postoperative Complications

The surgeon must be prepared to deal with postoperative complications. Some of the more common complications include wound leaks, epithelial defects, increased IOP, and difÞcult to control postoperative inßammation.

4.1.9.1 Wound Leaks

A wound leak should be suspected when a patient presents with a shallow or ßat anterior chamber, and

has a low IOP. The location of the leak can be identiÞed with the Seidel test. In the Seidel test, ßuorescein dye is placed on the surface of the cornea, and the cobalt blue light is used to view a change in color of the dye from black to bright green. Fluorescein dye appears black with a cobalt blue light and an aqueous leak appears green.

Treatment of a wound leak is as follows. If the patient has a ßat anterior chamber and the iris is in approximation to the cornea endothelium, the patient should be taken to the operating suite and the anterior chamber deepened as soon as possible. The area of the wound leak should be sutured and a Seidel test is performed under the operating microscope to ensure adequate closure. If the anterior chamber is shallow, but there is no apposition of the iris to the cornea, the surgeon may try a few nonsurgical maneuvers Þrst. A pressure patch may be used to hold the wound together until it has time to self-seal. Alternatively, a bandage contact lens may be used to reappose the wound by tamponading the leak and decreasing trauma from the eyelids to the wound. An antibiotic should be administered with the contact lens as prophylaxis against infection. If these measures fail after 24Ð48 h, the patient should be taken back to the operating suite and the wound repaired.

4.1.9.2 Epithelial Defects

Postoperative epithelial defects are more commonly encountered than wound leaks. Epithelial defects occur for a couple of different reasons. The donor epithelium may be irregular due to donor preparation factors including the death to preservation time and the preservation to use time. Donor tissue handling is also crucial and the eye bank preparing the donor tissue, as well as the surgeon using the donor tissue, must always be mindful of the epithelium and keep it well lubricated. Use of viscoelastics on the donor cornea throughout the procedure can help to preserve a preoperative intact epithelium.

If the patient has a history of ocular surface disease, this should be treated prior to cornea transplantation. Ocular surface disease includes dry eye syndrome and LSCD due to Stevens Johnson syndrome, ocular cicatricial pemphigoid, severe atopic disease, a history of chemical or thermal burn, and various others. Dry eye syndrome should be treated with anti-inßammatory

agents, and LSCD should be treated with ocular surface stem cell transplantation. These patients may also require permanent or temporary tarsorrhaphy following PK to ensure adequate and prompt epithelial healing.

An epithelial defect that does not heal promptly following PK will lead to persistent inßammation, ulceration, scarring, and graft failure. It is desirable to heal an epithelial defect within 1 week of PK. Methods of doing so include the use of a bandage contact lens with antibiotic coverage, pressure patching, or temporary or permanent tarsorrhaphy. The patient must be made aware of the need for prompt healing of any epithelial defect. Medications may need to be adjusted temporarily to decrease topical toxicity and promote healing. If the dose of topical prednisolone is reduced to aid healing of the epithelium, the surgeon should provide a short oral dose of prednisone if there are no major systemic contraindications. This will help prevent early graft rejection episodes. The possibility of an active herpes viral infection must be kept in mind when the patient has a persistent epithelial defect despite proper treatment. Topical or oral antiviral medication may be needed. The incidence, clinical diagnosis, and treatment of recurrent HSV keratitis in the graft will be discussed below.

4.1.9.3 Suture-Related Problems

Suture exposure postoperatively can be avoided by paying close attention to burying all suture knots at the end of the case. Exposed suture knots and tips are irritating and may cause foreign body sensation, pain, epiphora, excess mucus production, giant papillary conjunctivitis, dellen formation, and cornea erosions and ulcers. They act as a nidus of infection and act as a pathway for microorganisms to travel from the epithelium into the stroma. They also increase the risk of rejection by stimulating inßammation. Exposed suture knots or tails noted on slit-lamp biomicroscopy should be rotated and buried at the slit-lamp if possible. In addition, a broken or loose suture should be removed immediately.

4.1.9.4 Increased Intraocular Pressure

Increased IOP may be noted in the immediate postoperative period. Glaucoma following PK is one of the

most common causes for irreversible visual loss and the second leading cause of graft failure after rejection [5]. Control of an increased IOP is important because studies have shown that an elevated pressure is associated with endothelial cell loss. Svedbergh showed that elevated IOP could cause irreversible damage to monkey endothelial cells in vitro [1]. Bigar reported decreased endothelial cell counts in 5 of 13 eyes following an attack of acute angle closure glaucoma [1].

Post-PK ocular hypertension is deÞned as an elevated IOP greater than 21 mmHg. If there is an associated visual Þeld loss or optic nerve head change, the patient has glaucoma. It is often hard to assess the optic nerve head or visual Þeld prior to surgery due to cornea opaciÞcation. In the 1960s, instruments were developed that allowed routine monitoring of IOP after PK and post-PK glaucoma began to be recognized [5]. It was Irvine and Kaufman in 1969 that Þrst recognized increased IOP after PK and they reported a mean maximum pressure of 40 mmHg in aphakic transplants and 50 mmHg in combined transplants and cataract extraction in the immediate postoperative period [5]. The incidence of glaucoma post-PK varies among reporting authors from 9 to 31% in the early postoperative period to 18Ð35% in the late postoperative period [5]. In our study of large diameter grafts, glaucoma was noted in 1/35 graft recipients preoperatively. This patient was managed on topical IOP lowering medication preoperatively and remains on topical therapy postoperatively. Three of our remaining 34 patients developed an IOP increase postoperatively that required topical IOP lowering agents to control. This IOP increase was not related to a steroid response. The average time to IOP rise was 11.3 months (range 1Ð21 months), and all three recipients currently remain on topical therapy. Glaucomatous optic disc damage has not been detected clinically in any of the patients. None of these three patients have required a glaucoma surgery. Seven of 35 patients were steroid responders with a reduction in IOP noted following a dose decrease in the topical prednisolone or following a change to loteprednol. The incidence of glaucoma in our study of large diameter grafts was 8.8%.

Expected preoperative diagnosis that are risk factors for glaucoma in patients undergoing PK include aphakic and pseudophakic bullous keratopathy, irido- corneal-endothelial syndrome, preexisting glaucoma, perforated cornea ulcer, previous PK, posttraumatic cases, combined PK and cataract extraction, and

performance of vitrectomy during PK [5]. As mentioned DSEK is now the procedure of choice for aphakic and pseudophakic bullous keratopathy.

The pathophysiology of increased IOP is multifactorial. Zimmerman et al. proposed that mechanical collapse of the trabecular meshwork in aphakic grafts is the main problem leading to glaucoma [5]. They postulated that the trabeculum needs the posterior support of the lens and the anterior support of DescemetÕs membrane in order to prevent collapse upon itself [5].

Retained viscoelastic material is another very important cause of elevated IOP in the immediate postoperative period because these agents clog the trabecular meshwork. The initial placement of viscoelastic material into the anterior chamber during host cornea removal to push the iris back prior to inserting the beveled scissors, should be of only the smallest amount necessary. The surgeon should not use viscoelastic agents to deepen the anterior chamber during suture placement but instead should use BSS. Complete removal of these agents must be done at the end of surgery and care should especially be taken when a combined cataract extraction is part of the procedure. If the cornea has permitted adequate visualization and open-sky technique does not need to be employed for cataract removal, the surgeon must be sure to remove all viscoelastic agents from behind the lens implant at the end of the case and prior to beginning the cornea transplantation procedure.

Angle distortion can lead to an increased IOP. Factors that may lead to angle distortion include tight sutures, long suture bites, and larger diameter cornea transplants [5]. However, as mentioned, our study on large diameter cornea transplants had a reported incidence of increased IOP postoperatively within the reported literature incidence of glaucoma in patients with smaller grafts. Futhermore, no patient in our series required a glaucoma surgical procedure for correction of an IOP rise, and no patient had visible optic nerve head changes. Our patients were treated successfully with either a switch to loteprednol or the addition of an IOP lowering agent.

Postoperative inßammation and synechia formation are associated with an elevated IOP as is the use of topical steroid preparations. It is important to control IOP postoperatively and if the surgeon expects a high IOP in the immediate postoperative period, a topical IOP lowering medication or an oral carbonic anhydrase inhibitor should be given as prophylaxis.

An accurate IOP measurement postoperatively is often difÞcult via Goldmann applanation tonometry because abnormal epithelium and corneal shape will distort the mires. A tono-pen is often most helpful. The surgeon should keep in mind that corneal epithelial and stromal edema will lead to inaccurately low readings.

If a patient has a tarsorrhaphy that does not allow the IOP to be measured with the tono-pen, the IOP may be estimated by digital palpation. New tonometers are available that measure IOP through the lid (Proview Phosphene Tonometer).

Preexisting glaucoma needs to be addressed prior to PK. Reinhard et al. estimated the 3-year graft survival rate in patients with a preoperative history of glaucoma to be 71% in contrast to 89% when such a history is not present [6]. Furthermore, a high incidence of graft failure has been reported if a glaucoma operation is performed following the PK [5]. If a patient is taking more than one medication to treat their glaucoma preoperatively, we suggest discussing surgical options to manage the IOP prior to the PK. The glaucoma specialist and the cornea specialist must work together to ensure the best outcome for the patient postoperatively. A glaucoma drainage device (GDD) placed prior to the PK may be the best management strategy for the IOP postoperatively. A trabeculectomy preoperatively is another choice but we do not believe this is the best choice. Postoperative inßammation following the PK may allow the bleb to Þbrose and the surgeon performing a large diameter graft may have difÞculty avoiding the bleb when placing sutures. Our patients with preexisting glaucoma on more than one IOP lowering medication undergo GDD implantation by the glaucoma service in our department prior to PK. The cornea surgeon should wait 6Ð8 weeks following this procedure to perform the PK in order to allow postoperative inßammation to quiet so as to not put the patient at increased risk for both tube closure and graft rejection.

4.1.9.5 Post-Keratoplasty Astigmatism

Cornea transplantation is now considered a two-stage procedure. The Þrst stage is the actual cornea transplant itself. The second stage involves the correction of any postoperative irregular astigmatism. Postoperative astigmatism is the most common complication of PK.

Multiple factors affect the cylindrical component of the refraction. The tensions of each interrupted suture acts as an independent vector on the central corneal curvature. Interrupted sutures act by causing local ßattening and central steepening. The cylindrical spectacle prescription is the vector sum of forces acting on the cornea and describes simple astigmatism, but often the cornea surface is more complex than this and irregular astigmatism is present. Irregular astigmatism is the most common postoperative factor limiting the best achievable spectacle-corrected acuity.

is to attempt a RGP lens Þt. If a patient is intolerant to the contact lens then the surgeon must Þnd another way to correct the residual astigmatism. Reasons for contact lens intolerance include discomfort of the lens and poor manual dexterity such that the patient has difÞculty inserting the lens. Other ways of correcting irregular astigmatism that the surgeon may entertain include wedge resections, relaxing incisions, relaxing incisions with compression sutures, and refractive surgery: laser assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK).

4.1.10Correction of Post-keratoplasty Astigmatism

Surgical factors that lead to irregular astigmatism include suture tension, suture depth, suture length, suture radiality, and perhaps suture technique [1], although as mentioned above, some studies have not agreed that the suture technique makes much of a difference. It thus makes sense that the removal of a tight or abnormally placed suture would help decrease irregular astigmatism. Selective suture removal is the Þrst method used postoperatively to improve visual acuity. The topography of the donor cornea is not stable until 4Ð8 weeks after surgery. The surgeon should wait until after this time to begin selective suture removal and we prefer to wait until 12 weeks postoperatively.

Topography helps to guide selective suture removal. Sutures are removed according to the steep topographic axis. The amount of effect from the removal of a single suture in any one meridian cannot be predicted. Typically there are an average of two to three diopters of ßattening in the meridian of the removed suture, but this may vary and a much larger change may result [1]. Removal of one suture per postoperative visit allows more predictable adjustment and results in lower postoperative astigmatism when compared to multiple suture removal [1]. The changes usually occur immediately but there may be a continued adjustment in curvature over the ensuing weeks to months [1].

We currently place 24 interrupted 10-0 nylon sutures and begin selective suture removal at 3 months postoperatively according to topography maps.

Once all sutures have been removed and a patient has a residual amount of irregular post-keratoplasty astigmatism, the surgeon has a few options. The Þrst option

4.1.10.1Wedge Resections and Compression Sutures

A ßat cornea meridian can be steepened with wedge resections or compression sutures. Compression sutures can be placed across the graftÐhost junction in the ßat meridian to cause steepening, but they also cause a compensatory ßattening in the steep meridian. They are thus usually used with relaxing incisions. This method is not commonly used because suture materials degrade with time.

Cornea wedge resections can be performed for very high amounts of astigmatism, with the wedge being removed from the donor or the host. Increasing the width of the tissue resection leads to larger amounts of correction. Results can be unpredictable.

4.1.10.2 Relaxing Incisions

Relaxing incisions can be of the arcuate, transverse, or trapezoidal variety. They may be placed at the limbus, in the graftÐhost junction, or in the donor cornea. These incisions may steepen or ßatten the corneal meridian depending on the procedure used [1]. The degree of correction is inßuenced by the incision depth, length, and proximity to the optical axis [1]. Advantages to relaxing incisions include a rapid return of vision and the procedure can be done at the slit lamp [1]. Results again can be unpredictable.

4.1.10.3 LASIK

LASIK has been successful in reducing post-kerato- plasty astigmatism. Donnenfeld et al. have published a