• Cornea/External Disease

    Descemet's stripping automated endothelial keratoplasty (DSAEK) is becoming the treatment of choice for corneal endothelial failure due to its better preservation of the globe's integrity, typically faster visual rehabilitation and more predictable visual outcomes compared with conventional penetrating keratoplasty.1 Nonetheless, as with any ocular surgery, intraoperative and postoperative complications can occur. Taking appropriate preventive measures and being aware of potential complications and their optimal management can greatly increase the chances of a favorable postoperative outcome. This article discusses how to prevent these complications and how best to handle them if they do occur.

    Intraoperative complications

    Endothelial damage during donor graft preparation

    During the donor preparation with the microkeratome, the artificial anterior chamber should be filled with sufficient storage media and the excess conjunctiva on the corneoscleral rim removed prior to sealing the artificial anterior chamber to minimize endothelial damage. A sufficiently large scleral rim is necessary to obtain an adequate seal on the artificial anterior chamber. Chamber collapse can be prevented by using continuous positive pressure and inverting the artificial anterior chamber when dismounting the donor tissue. For storing precut tissues, it is recommended that the anterior lamellar cap be kept in place and the tissue used immediately to reduce endothelial cell loss.2

    Paracentral trephination

    An eccentric donor trephination can result in an optically and mechanically compromised graft. Furthermore, if the punched area goes into the thicker peripheral tissue, the resulting thickened edge can interfere with graft attachment, leading to an increased risk of decentration and dislocation.3,4 In order to help center the cut, the edges of the stromal side of the donor tissue can be marked with ink prior to trephination. If the decentered cut has already been made and is sufficiently large, the tissue can be repunched slightly eccentrically. To prevent severe endothelial damage, make sure the graft has been cut through completely before disassembling the trephine.

    Retained Descemet's membrane

    DSAEK is most often performed for edematous corneas, which can obscure visualization and complicate stripping of Descemet's membrane. Incomplete removal of the recipient's Descemet's membrane may result in persistent edema, graft detachment and eventual graft failure.4 In cases of refractory postoperative corneal edema, anterior segment optical coherence tomography (ASOCT) is useful for detecting the presence of residual Descemet's membrane. If it is detected, waiting several months for edema to resolve is not beneficial and a repeat DSAEK with the removal of the residual Descemet's membrane may be warranted.

    Air in the posterior segment

    An air bubble is injected into the anterior chamber to push the donor graft against the recipient stromal bed to promote graft attachment. However, maintenance of air in the anterior chamber is challenging in aphakic eyes, pseudophakic eyes with an open posterior capsule and eyes that have undergone trabeculectomy (Figure 1) or received glaucoma drainage implants. If air does escape to the posterior chamber, angle-closure glaucoma and endothelial damage can occur because the lens and iris are pushed towards the cornea. In these cases, the patient should be kept in a strict supine position and longer-lasting, higher-buoyancy gases, such as SF6, used.5

    Sonia Yoo, MD

    Figure 1. Subconjunctival air leakage after DSAEK in a patient who had previously undergone trabeculectomy.

    Additional complications

    Following are some less common complications and issues to keep in mind when they are seen:

    • Anterior chamber hemorrhage: Preservative- free epinephrine can be helpful.
    • Lens damage: Take special care to avoid lens damage in phakic patients.
    • Iridectomies: Avoid perforating the capsule or zonules since this can lead to vitreous loss.

    Postoperative complications

    Donor dislocation

    The most common complication after DSAEK is lenticule dislocation.6-8 The causes of graft dislocation are thought to be multifactorial and include tissue storage conditions, surgical techniques, pre-existing conditions and lack of patient cooperation (e.g., improper positioning and eye rubbing). Intraoperatively surgeons should minimize the amount of viscoelastic used. After the donor tissue is positioned, interface fluid/air can be removed by massaging and smoothing the corneal surface with a cannula tip and aspiration with a 30-gauge cannula through paracentral corneal vents placed during surgery. Postoperatively, surgeons should screen for possible graft dislocations using slit-lamp biomicroscopy and ASOCT (Figure 2).6 The patient should be kept in a supine position and eye rubbing discouraged. If a detachment is observed, rebubbling and graft repositioning can be performed up to one week postoperatively. ASOCT can confirm graft reattachment. 

    Sonia Yoo, MD

    Figure 2. Pre-rebubbling, A. Slit-lamp examination, and B. Visante OCT reveals a dislocated donor graft after DSAEK. Post-rebubbling, C. Slit-lamp examination, and D. Visante OCT shows the graft has reattached.

    Graft failure and rejection

    Causes of primary graft failure include prolonged donor tissue preservation, improper tissue preparation and traumatic surgical technique. The donor graft should have at least 2000 endothelial cells/mm2 and donors over the age of 70 should be avoided.9 Causes of secondary graft failure include fluid or viscoelastic at the interface and residual Descemet's membrane. Once graft failure has occurred, regrafting may be indicated.

    Any inflammation in an eye after DSAEK is considered rejection until proven otherwise. Patients who are black or have pre-existing glaucoma or steroid-responsive ocular hypertension are at increased risk of graft rejection.10 To prevent rejection, a long-term topical corticosteroid regimen should be used: prednisolone acetate 1% four times a day for at least one month, and then a slow taper to once a day for six to twelve months. Once graft rejection is detected, a topical corticosteroid should be used every hour, with a subsequent taper once the rejection has been halted. Sub-Tenon's triamcinolone may also be helpful.

    Pupillary block glaucoma

    Although rare, pupillary block can occur after DSAEK. If not recognized promptly, the graft endothelium can become damaged and peripheral anterior synechiae (PAS) can form. PAS can lead to refractory elevated intraocular pressures and subsequent optic nerve damage. Pupillary block is usually detected on postoperative day one by the presence of a shallow anterior chamber, high intraocular pressure, PAS and iridocorneal adhesions.

    If pupillary block is detected, immediate partial evacuation of the air bubble with concurrent replacement using balanced salt solution and lysing of present PAS are necessary. Recommended preventive measures include preoperative or intraoperative iridotomy, placement of a freely mobile air bubble that does not fill the entire anterior chamber and the use of cycloplegics and mydriatic eye drops (such as cyclogyl 1% and phenylephrine 2.5%).6,11

    Additional complications

    • Refractive change: When choosing the intraocular lens power in DSAEK triple surgery, consider the postoperative hyperopic refractive shift.
    • Interface abnormalites (Figure 3): Some cases resolve spontaneously while others require regrafting.6
    • Epithelial ingrowth: If the visual axis is not compromised and the donor tissue is well-attached, the patient can be observed closely.
    • Retinal complications: Increased risk associated with a previous history of posterior pole surgery, intraocular lens exchange and scleral fixated intraocular lens.6
    • Cystoid macular edema: Topical nonsteroidal therapy or intravitreal triamcinolone may be helpful.3,6

    Sonia Yoo, MD

    Figure 3. Donor-graft interface debris seen after DSAEK. 

    The authors would like to thank Fernanda Piccoli, MD, and Artur Schmitt, MD, for their help and contributions.

    References

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    3. Bahar I, Kaiserman I, McAllum P, Slomovic A, Rootman D. Comparison of posterior lamellar keratoplasty techniques to penetrating keratoplasty. Ophthalmology. 2008;115(9):1525-1533.
    4. Kymionis GD, Suh LH, Dubovy SR, Yoo SH. Diagnosis of residual Descemet's membrane after Descemet's stripping endothelial keratoplasty with anterior segment optical coherence tomography. J Cataract Refract Surg. 2007;33(7):1322-1324.
    5. Suh LH, Kymionis GD, Culbertson WW, O'Brien TP, Yoo SH. Descemet stripping with endothelial keratoplasty in aphakic eyes. Arch Ophthalmol. 2008;126(2):268-270.
    6. Suh LH, Yoo SH, Deobhakta A, et al. Complications of Descemet's stripping with automated endothelial keratoplasty: survey of 118 eyes at One Institute. Ophthalmology. 2008;115(9):1517-1524.
    7. Terry MA, Hoar KL, Wall J, Ousley P. Histology of dislocations in endothelial keratoplasty (DSEK and DLEK): a laboratory-based, surgical solution to dislocation in 100 consecutive DSEK cases. Cornea. 2006;25(8):926-932.
    8. Mearza AA, Qureshi MA, Rostron CK. Experience and 12-month results of descemet-stripping endothelial keratoplasty (DSEK) with a small-incision technique. Cornea. 2007;26(3):279-283.
    9. Wilhelmus KR, Stulting RD, Sugar J, Khan MM. Primary corneal graft failure. A national reporting system. Medical Advisory Board of the Eye Bank Association of America. Arch Ophthalmol. 1995;113(12):1497-1502.
    10. Price MO, Jordan CS, Moore G, Price FW Jr. Graft rejection episodes after Descemet stripping with endothelial keratoplasty: part two: the statistical analysis of probability and risk factors. Br J Ophthalmol. 2009;93(3):391-395.
    11. Terry MA, Shamie N, Chen ES, Hoar KL, Friend DJ. Endothelial keratoplasty a simplified technique to minimize graft dislocation, iatrogenic graft failure, and pupillary block. Ophthalmology. 2008;115(7):1179-1186.