Deep Anterior Lamellar Keratoplasty as an Alternative to Penetrating ...

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Ophthalmology Volume 118, Number 1, January 2011● Endothelial cell loss secondary to air/synthetic gas.● Interface haze or irregularity if all stroma is not removedin the visual axis.● Interface debris, hemorrhage, vascularization, microbialinfections, and epithelial ingrowth.● Wrinkles of DM or the residual stroma and DM layer.● Sequestered OVD in the interface.● Mydriasis from air block glaucoma usually complicatinganterior chamber gas injection to treat DMdetachment.● Recurrence of stromal cornea dystrophy in the residualbed.● Occasional re-epithelialization problems.The most common complication involves puncturingDM with either small perforations of 1 mm or less, ormacroperforations that usually lead to immediate operativeconversion to PK. This can occur with either big-bubbletechniques using air, OVD, or fluid injection, or micro ormacro DM perforation during direct dissection using asurgical blade with or without the injection of fluid, air, orOVD injection. Conversion to a conventional PK may beadvisable unless the perforation is small.Lamellar splits in DM with stromal pressure dissectionusing air, fluid, or OVD are uncommon and may not berecognized by the operating surgeon, but they do increasethe risk of DM perforation because of the thinness of theremaining DM. If a perforation occurs, but a DALK iscompleted, then air or other gas placement in the anteriorchamber to tamponade the perforation may lead to additionalECD loss, gas pupillary block with a fixed dilatedpupil, 41,42 or eventual failure of the DALK graft and theneed for a delayed conversion to PK. Although perforationsare common at an average rate of 11.7%, intraoperative PKconversions of 2.0% and delayed PK conversions of 0.4%suggest that most DALK cases will be completed asplanned. If a DM perforation occurs before DM has beenexposed in the central optical zone of 5 mm or so, residualstroma may be left and the donor graft placed on top, withpossible reduced visual acuity from residual stroma in thissituation.Microperforations of DM that do not preclude a lamellaronlay graft can occur during DALK, although there is a riskof postoperative DM detachment and pseudo double anteriorchamber formation. Double anterior chamber is usuallya consequence of DM perforations, but has also been describedin the absence of known perforations. This also maypersist if the endothelium has not been removed from thedonor graft and may complicate subsequent cataract surgerywith DM detachment. 43 Endothelial cell loss secondary toair/synthetic gas after anterior chamber injection to manageintraoperative DM tears or postoperative double anteriorchamber may occur. 44Interface haze is rarely a problem with DM-baring proceduresand sometimes even experienced observers cannotdistinguish between a PK and a DALK eye if DM has beenexposed in the entire recipient bed. Interface haze maycause glare or decreased visual acuity. Interface debris,hemorrhage from host stromal vascularization, interfacevascularization, microbial infections, and interface epithelialingrowth are rare complications. 22,45,46 Wrinkles of DMare more common in keratoconus eyes with advanced cones,presumably from compression of the cone when placing thedonor graft. 47 Wrinkles may also contribute to glare ordecreased vision. If noted at the time of surgery, manipulatingthe donor graft may displace the wrinkles out of thevisual axis and decrease their effect on vision.Retained OVD can complicate the Melles or limbalpocket techniques where an OVD is used to expand thelimbal entrance pocket dissection to enable safe trephination.48 Often OVD is also used to reexpand the collapsed airbubble in the big-bubble techniques before removing theremaining stroma. In any case, the surgeon needs to bediligent in gently irrigating OVD from the lamellar bedbefore placing the donor graft to avoid potential donor graftedema or donor failure.Postoperative DM detachment or a double anteriorchamber leads to poor vision from an edematous graft andthe need to inject air or another gas into the anterior chamberto tamponade the tear. Larger or inferior tears are moredifficult to tamponade with gas and may require suturereattachment or delayed conversion to PK. Complicationsof a large gas bubble in the anterior chamber include loss ofendothelial cells; air block glaucoma, which, in its mostsevere form, can result in permanent pupillary mydriasisdue to iris ischemia, iris peripheral anterior synechiae, andglaucomflecken because of anterior lens epithelial/lens corticalinfarcts (a group of complications usually referred to as“Urrets–Zavalia syndrome”); 49 and, rarely, ischemic damageto the optic nerve or retina. These complications arerelated to elevated IOP and are likely also related to theduration of the IOP elevation. Prompt diagnosis of thepupillary block glaucoma and management with pupil dilationor paracentesis to reduce the size of the gas bubble,deepen the anterior chamber, and eliminate the pupillaryblock will often prevent these complications.Recurrence of the corneal stromal dystrophies in theanterior portion of a corneal graft is expected for PK orDALK. However, recurrence in the interface has been aproblem with LASIK surgery and can also occur withDALK. It is suspected that recurrence of a stromal dystrophysuch as lattice dystrophy in the deep lamellar bed is dueto retained host stroma and would be unlikely with theDM-baring techniques.Occasional re-epithelialization problems can occur ifcryolathed or lyophilized donor lamellar tissue is used,although re-epithelialization can also complicate PK whenthe epithelium is often not viable after longer corneal donorstorage times.Complications unique to PK are as follows:● Immune rejection of donor corneal endothelium.● Prolonged topical corticosteroid use necessary in somecases.● Microbial endophthalmitis.● Trephine complications (iris damage, damage to thecrystalline lens, and retained DM).● Open eye complications (positive vitreous pressure,expulsive choroidal hemorrhage, and damage to theiris and/or lens).214
Reinhart et al Deep Anterior Lamellar Keratoplasty● Penetrating wound complications (flat anterior chamberfrom wound leak, iris synechiae to wound, andpoor vertical wound apposition).● Elevated IOP from retained OVD.● Anterior chamber epithelial ingrowth.● Primary donor graft endothelial failure.● Accelerated donor graft endothelial cell loss (instrumenttrauma to the donor endothelium, trauma to theendothelium at surgery from iris or lens contact, andpostoperative biphasic accelerated loss).Immune corneal endothelial rejection can be a majorproblem with high-risk corneal transplant recipients, usuallyinvolving significant corneal stromal vascularization, inflammation,and anterior segment abnormalities. These eyesare occasional candidates for DALK if the host endotheliumis normal, as it might be in ocular surface chemical injuries,ocular mucous membrane pemphigoid, Stevens–Johnsonsyndrome, inactive interstitial keratitis with corneal scarringfrom varicella zoster virus or herpes simplex virus, andvascularized corneas after treatment for microbial keratitis.Deep anterior lamellar keratoplasty or even a therapeuticLK would be the preferred procedure if ocular surfaceproblems can be managed. However, for keratoconus, immunerejection is not a major problem, because in keratoconusa graft rarely fails as the result of immune endothelialrejection if treated promptly and appropriately. Whether theaccelerated long-term loss of ECD in PK is related tosubclinical immune endothelial rejection or other causes hasnot yet been determined.Prolonged topical corticosteroid use may be needed insome cases with recurrent immunologic graft reactions.Corticosteroid-induced IOP increases may require use oftopical glaucoma medications or filtration surgery to controlthe IOP. There may be loss of vision from secondaryglaucoma, and the patient may not be able to wear contactlenses during times of significant immunosuppression of theocular surface with topical corticosteroids because of theincreased risk of infectious keratitis. There is also an increasedcost associated with prolonged use of topical corticosteroidor glaucoma medications.Some of the complications unique to PK, such as microbialendophthalmitis, expulsive choroidal hemorrhage, andepithelial downgrowth, can be devastating. These severecomplications are fortunately rare, particularly for phakicPK surgery that would usually be the alternative to DALKsurgery (because most eyes with keratoconus, nonpenetratingcorneal scars, herpes simplex virus, corneal scars, and soforth are phakic).Complications related to the anterior chamber penetratingnature of PK surgery are also uncommon in experiencedhands, although when they do occur, they can result incompromised visual outcomes.Complications common to PK and DALK include thefollowing:● Ametropias, astigmatism of excessive amount, irregularastigmatism.● Suture-related problems (sterile inflammation, microbialabscess, problems with epithelialization, prematureloosening, induced astigmatism, delayed absorption,and unpredictable breakage).● Immune donor epithelial and stromal rejection.● Recurrence of corneal dystrophies.● Corneal ectasia (recurrent keratoconus) of the graft,progressive host ectasia in keratoconus eyes.● Donor endothelial cell loss in PK and loss of host ECDin DALK, especially with DM perforations or anteriorchamber injection of air or gas.● Decreased resistance to globe rupture from blunt oculartrauma; usually the transplant wound remains theweakest part of the eyeball tunic.● Ocular surface disease.● Donor-to-host transmission of infection.Sutures can be removed much earlier in DALK proceduresthan in PK, potentially leading to fewer suture-relatedproblems after DALK. Stromal and epithelial immune rejectioncannot occur in those DALK procedures wherecryolathed or lyophilized donor corneal tissue has been usedto prepare the lamellar donor tissue because all keratocytesand epithelial cells are killed in the processing of the donortissue. However, most surgeons use corneal tissue preservedin short- or intermediate-term corneal preservation media,which usually preserves stromal keratocytes and, to a variabledegree, donor corneal epithelium. Stromal graft rejections,which are uncommon in the first place, become morerare as postoperative time increases.In general, low-risk PK eyes with a diagnosis such askeratoconus are usually tapered off topical corticosteroidsby 6 months after surgery, and corticosteroid-related glaucomais rarely a major management problem. However, fora few patients with repeated immune graft rejections, therequired use of corticosteroids for immunosuppression canresult in corticosteroid-induced glaucoma and posterior subcapsularcataract formation. The need for topical corticosteroidsin DALK eyes is unusual after 6 months postoperatively.Even if corticosteroids are needed to treatsubepithelial infiltrates or stromal graft rejection in DALKeyes, topical corticosteroids rarely have to be used forextended periods of time if there is no other source ofinflammation.Corneal dystrophies are known to recur after PK, usuallyinvolving the anterior part of the graft, and they would beexpected to recur in similar fashion after anterior lamellarcorneal procedures including DALK.Late postoperative corneal ectasia after DALK has beenreported. 50 This was a true keratoconus recurrence in aDALK cornea from lyophilized donor tissue in a schizophrenicpatient with habitual eye rubbing, an apparent causeof recurrent keratoconus, 51 and a repeat DALK was successful.Late-onset keratoconus has also been reported forPK in keratoconus eyes. True keratoconus as a complicationof a PK has been documented, 52 although most cases describedas late-onset keratoconus are probably due to continuedectasia of a portion of the residual host cornea,usually inferiorly, and is not true keratoconus where thegraft itself undergoes central thinning and ectasia. It remainsto be determined whether keratoconus after a PK or aDALK graft is due to undiagnosed keratoconus in the donor215
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