Comparison of deep lamellar keratoplasty and penetrating keratoplasty for lattice and macular corneal dystrophies

Corneal Allograft Rejection: Immunopathogenesis to Therapeutics

Corneal transplantation is among the most successful solid organ transplants. However, despite low rejection rates of grafts in the ‘low-risk’ setting, rejection can be as high as 70% when grafted into ‘high-risk’ recipient beds. Under normal homeostatic conditions, the avascular cornea provides a unique environment that facilitates immune and angiogenic privilege. An imbalance in pro-inflammatory, angiogenic and lymphangiogenic mediators leads to a breakdown in corneal immune privilege with a consequent host response against the donor graft. Recent developments in lamellar and endothelial keratoplasties have reduced the rates of graft rejection even more, while providing improved visual outcomes. The corneal layer against which an immune response is initiated, largely determines reversibility of the acute episode. While epithelial and stromal graft rejection may be treated with topical corticosteroids with higher success, acute endothelial rejection mandates a more aggressive approach to therapy due to the lack of regenerative capacity of this layer. However, current immunosuppressive regimens come with the caveat of ocular and systemic side effects, making prolonged aggressive treatment undesirable. With the advent of biologics, efficacious therapies with a superior side effect profile are on the horizon. In our review we discuss the mediators of ocular immune privilege, the roles of cellular and molecular immune players in graft rejection, with a focus on human leukocyte antigen and antigen presenting cells. Furthermore, we discuss the clinical risk factors for graft rejection and compare rates of rejection in lamellar and endothelial keratoplasties to traditional penetrating keratoplasty. Lastly, we present the current and upcoming measures of therapeutic strategies to manage and treat graft rejection, including an overview of biologics and small molecule therapy.

Outcomes of deep anterior lamellar keratoplasty using the big-bubble technique in various corneal diseases

PURPOSE

To report clinical outcomes of deep anterior lamellar keratoplasty (DALK) using the big-bubble technique in various original diagnoses.

DESIGN

Prospective interventional study.

METHODS

Single hospital study of 115 unselected consecutive patients (131 eyes) with various diagnoses undergoing DALK using the big-bubble technique. The main outcome measures were intraoperative and postoperative complications, postoperative best spectacle-corrected visual acuity (BSCVA), and endothelial cell density (ECD).

RESULTS

Descemet membrane was exposed successfully in 25 eyes (80.6%) with advanced keratoconus, 11 (73.3%) with chemical or thermal burns, 20 (71.4%) with corneal dystrophy, 21 (70%) with a herpes simplex (HSK) keratitis scar, 4 (36.4%) with moderate keratoconus, and 5 (31.3%) with a bacterial keratitis scar (P < .05). Loosening of the sutures occurred in 24 eyes (23.8%) between postoperative4 and 7 months. Epithelial rejection was observed in 2 eyes and stromal rejection occurred in 5 eyes. BSCVA was improved in HSK scarring and corneal dystrophy vs keratoconus and corneal burns at 1 year (P < .05), but not after a mean follow-up of 21.4 months (P < .05). Patients who experienced stromal rejection had lower ECD than patients with no rejection at 18 and 24 months (P < .05). At all follow-up times after 6 months, patients with multiple air injection attempts had lower ECD than patients with 1 injection attempt (P < .05).

CONCLUSIONS

Different Descemet membrane exposure rates were observed in different diagnoses using the big-bubble technique. Both severe stromal rejection and additional manipulation may have a deleterious effect on the corneal endothelium.

Long-term results of deep anterior lamellar versus penetrating keratoplasty

OBJECTIVE

To compare deep anterior lamellar keratoplasty (DALK) with penetrating keratoplasty (PK) in eyes with corneal diseases not involving the corneal endothelium (keratoconus, scars after infectious keratitis, stromal dystrophies, and trauma).

DESIGN

Retrospective, comparative case series.

PARTICIPANTS

One hundred forty-two consecutive DALK (DALK group; big-bubble technique or manual lamellar dissection using a slitlamp) and 142 matched PK (PK group).

METHODS

Three models were used to describe the postoperative outcomes of the endothelial cell density. A joint regression model was used to predict long-term graft survival. Visual acuity, ultrasound pachymetry, specular microscopy, and optical coherence tomography (OCT) findings were recorded.

MAIN OUTCOME MEASURES

Postoperative endothelial cell loss and long-term predicted graft survival.

RESULTS

The average 5-year postoperative endothelial cell loss was -22.3% in the DALK group and -50.1% in the PK group (P<0.0001). The early- and late-phase annual rates of endothelial cell loss were -8.3% and -3.9% per year, respectively, in the DALK group and -15.2% and -7.8% per year in the PK group (P<0.001; biphasic linear model). The median predicted graft survival was 49.0 years in the DALK group and 17.3 years in the PK group (P<0.0001). The average visual acuity was lower in the manual dissection subgroup compared with the PK group (average difference, 1.0 to 1.8 line) and with the big-bubble subgroup (average difference, 2.2 to 2.5 lines). The average central corneal thickness at 12 months was 536 μm in the PK group, 523 μm in the big-bubble subgroup, and 562 μm in the manual dissection subgroup (P<0.001). The average thickness of the residual recipient stroma measured by OCT was 87±26 μm in the manual dissection subgroup. No correlation was found between this figure and logarithm of the minimal angle of resolution at any postoperative time point (P>0.05).

CONCLUSIONS

Long-term, model-predicted graft survival and endothelial densities are higher after DALK than after PK. The big-bubble technique gives better results than manual dissection and PK. Compared with PK, manual dissection provides higher survival of both the corneal endothelium and graft, but lower visual acuity.

Deep anterior lamellar keratoplasty: indications, surgical techniques and complications

The concept of lamellar keratoplasty (LK) is not new. However, it had been abandoned and largely replaced by the time-honored technique of penetrating keratoplasty (PK) because LK is technically demanding, time consuming and gives suboptimal visual outcomes due to interface irregularity arising from manual lamellar dissection. Recent improvements in surgical instruments and introduction of new techniques of maximum depth of corneal dissection as well as inherent advantages such as preservation of globe integrity and elimination of endothelial graft rejection have resulted in a re-introduction of LK as an acceptable alternative to conventional PK. This review article describes the indications, different techniques, clinical outcomes and complications of deep anterior LK.

Incremental cost-utility analysis of deep anterior lamellar keratoplasty compared with penetrating keratoplasty for the treatment of keratoconus

PURPOSE

This study sought to determine the cost effectiveness of deep anterior lamellar keratoplasty (DALK) compared with penetrating keratoplasty (PK) for the treatment of keratoconus. DALK is associated with lower rates of postoperative complications compared with PK, but is a more expensive procedure; whether it is cost effective compared with PK is unknown.

DESIGN

The study was an incremental cost-utility analysis from a health systems perspective using retrospective data on a cohort of patients with severe keratoconus.

METHODS

The analysis was conducted using 1-year cost and outcomes data from 148 keratoconus patients, representing 102 PK and 46 DALK cases, seen for corneal grafts between January 1991 and January 2009 at the Singapore National Eye Center. The main outcome assessed was the incremental cost-utility ratios associated with PK and DALK for the treatment of keratoconus.

RESULTS

Over a 20-year period, PK was the lower cost procedure and had an incremental cost-utility ratio of $3,750 per quality-adjusted life-year compared with no surgical treatment. Compared with PK, DALK has an incremental quality-adjusted life-year gain of 0.8 and an incremental cost of $2,420, for an incremental cost-utility ratio of $3,025 per quality-adjusted life-year.

CONCLUSIONS

Compared with PK, DALK has a favorable cost-effectiveness ratio and, resources permitting, should be considered as a first-line treatment for keratoconus. Additional studies are needed to confirm the expected advantages of DALK over PK when it comes to long-term graft failure rates.

Graft rejection and graft failure after anterior lamellar versus penetrating keratoplasty

PURPOSE

To compare anterior lamellar keratoplasty (ALK) with the reference surgical technique (penetrating keratoplasty [PK]) for risk of rejection.

DESIGN

Retrospective, comparative case series.

METHODS

setting: Institutional. patients: One hundred forty-nine consecutive ALK procedures (ALK group) and 149 matched PK procedures (PK group) performed for optical indication in eyes with corneal diseases not involving the corneal endothelium (ie, keratoconus, scars after infectious keratitis, stromal dystrophies, and trauma). main outcome measures: Three-year graft survival and cumulative incidence of rejection episodes.

RESULTS

The 3-year overall graft survival was 98.3% in the ALK group and 94.3% in the PK group (P = .03). The 3-year cumulative incidence of irreversible rejection was 0.0% in the ALK group and 5.2% in the PK group (P = .02). The 3-year cumulative incidence of rejection episodes was 10.0% in the ALK group and 23.2% in the PK group (P = .01). The average graft-to-rejection episode time was 21.6 ± 22.0 months in the PK group and 19.4 ± 12.7 months in the ALK group (P = .76).

CONCLUSIONS

ALK techniques dramatically decrease the risk of irreversible endothelial and stromal rejection after corneal transplantation. Immune-mediated rejection episodes are observed after ALK, but its lower graft failure rate compared with PK is at least partly the result of the absence of endothelial rejection. In addition, the incidence of rejection episodes after ALK was 50% less than that observed after PK.

Economic evaluation of deep anterior lamellar keratoplasty versus penetrating keratoplasty in The Netherlands

PURPOSE

To evaluate the cost effectiveness of deep anterior lamellar keratoplasty (DALK) versus penetrating keratoplasty (PK) in The Netherlands.

DESIGN

Cost-effectiveness analysis alongside a randomized, multicenter clinical trial.

METHODS

Fifty-three patients with corneal stromal pathologic features not affecting the endothelium were included with 28 patients in the DALK group and 25 in the PK group. Quality of life was measured before surgery and 3, 6, and 12 months after surgery. The main outcome measures were incremental cost-effectiveness ratios per clinically improved patient on the 25-item National Eye Institute Visual Functioning Questionnaire and per patient with endothelial cell loss of maximally 20% within the first year.

RESULTS

Mean total bootstrapped costs per patient were €7607 (US$10,498) in the DALK group and €6552 (US$9042) in the PK group. The incremental cost-effectiveness ratios were €9977 (US$13,768) per clinically improved patient on the 25-item National Eye Institute Visual Functioning Questionnaire and €6900 (US$9522) per patient with cell loss of maximally 20%. In patients without perforation of the Descemet membrane, the incremental cost-effectiveness ratio was €5250 (US$7245) per patient.

CONCLUSIONS

This study shows that DALK is more costly and more effective as compared with PK. Results on the 25-item National Eye Institute Visual Functioning Questionnaire were in favor of DALK, and endothelial cell loss in DALK patients remained stable after 6 months, whereas cell loss in PK patients continued. Furthermore, DALK procedures performed without perforation of the Descemet membrane were more effective. However, because it is unknown what society is willing to pay for an additional improved patient, cost effectiveness of DALK within a limited follow-up period of 12 months is unclear. Cost effectiveness of DALK may improve over time because of lower graft failure.

Deep anterior lamellar keratoplasty as an alternative to penetrating keratoplasty a report by the american academy of ophthalmology

OBJECTIVE

To review the published literature on deep anterior lamellar keratoplasty (DALK) to compare DALK with penetrating keratoplasty (PK) for the outcomes of best spectacle-corrected visual acuity (BSCVA), refractive error, immune graft rejection, and graft survival.

METHODS

Searches of the peer-reviewed literature were conducted in the PubMed and the Cochrane Library databases. The searches were limited to citations starting in 1997, and the most recent search was in May 2009. The searches yielded 1024 citations in English-language journals. The abstracts of these articles were reviewed, and 162 articles were selected for possible clinical relevance, of which 55 were determined to be relevant to the assessment objective.

RESULTS

Eleven DALK/PK comparative studies (level II and level III evidence) were identified that compared the results of DALK and PK procedures directly; they included 481 DALK eyes and 501 PK eyes. Of those studies reporting vision and refractive data, there was no significant difference in BSCVA between the 2 groups in 9 of the studies. There was no significant difference in spheroequivalent refraction in 6 of the studies, nor was there a significant difference in postoperative astigmatism in 9 of the studies, although the range of astigmatism was often large for both groups. Endothelial cell density (ECD) stabilized within 6 months after surgery in DALK eyes. Endothelial cell density values were higher in the DALK groups in all studies at study completion, and, in general, the ECD differences between DALK and PK groups were significant at all time points at 6 months or longer after surgery for all of the studies reporting data.

CONCLUSIONS

On the basis of level II evidence in 1 study and level III evidence in 10 studies, DALK is equivalent to PK for the outcome measure of BSCVA, particularly if the surgical technique yields minimal residual host stromal thickness. There is no advantage to DALK for refractive error outcomes. Although improved graft survival in DALK has yet to be demonstrated, postoperative data indicate that DALK is superior to PK for preservation of ECD. Endothelial immune graft rejection cannot occur after DALK, which may simplify long-term management of DALK eyes compared with PK eyes. As an extraocular procedure, DALK has important theoretic safety advantages, and it is a good option for visual rehabilitation of corneal disease in patients whose endothelium is not compromised.

Deep anterior lamellar Keratoplasty

Keratoconus is a disease causing increased steepening of the cornea resulted in irregular astigmatism. Treatment options are Glasses, Hard contact lenses, Cross linking, Intracorneal Segments insertion, Refractive surgery (Gilda et al., 2008), or Keratoplasty. Lamellar Keratoplasty (LKP) can be a better choice to manage cases of moderate and some cases of severe Keratoconus without deep scarring and severe thinning, also in cases of corneal scarring not involving the deeper layers of the cornea. LKP is a corneal graft technique consisting of transplantation of partial-thickness donor tissue, devoid of endothelium, Descemet membrane (DM), and rear stroma into a recipient healthy stromal bed after dissection of pathologic anterior stroma. However, deep lamellar Keratoplasty (DLKP) is a surgical method that completely removes pathologic corneal stroma tissue down to the DM, followed by transplantation of donor cornea without endothelium over the host bed. DLKP has a number of advantages over penetrating Keratoplasty (PKP). Because it does not violate the intraocular structures of the eye, it diminishes or eliminates the chance of postoperative glaucoma, cataract formation, retinal detachment, cystoids macular edema, expulsive choroidal hemorrhage and epithelial ingrowths. Furthermore, this procedure avoids the replacement of host endothelium with donor endothelium and thus precludes endothelial graft rejection, with comparable visual outcomes and low rate of chronic endothelial cell loss compared to PKP.

A novel technique for performing full-bed deep lamellar keratoplasty

In recent years, deep lamellar keratoplasty (DLKP) has become an alternative surgical approach successfully applied to the treatment of opaque cornea with normal endothelial function. However, techniques for performing DLKP are not standardized and have not been perfected compared with penetrating keratoplasty. We developed a technique of stromal hooking and viscoelastic detaching to create a full-bed exposure of Descemet membrane (DM) for DLKP grafting. The surgical procedures include trephining the recipient stroma, exposure of DM by stromal hooking process using a forceps tooth as hook, detaching stroma from DM by injecting viscoelastic between the 2 layers, removing whole stroma around the trephined margin to obtain full-bed exposure of DM, and grafting cryopreserved donor button. Unlike previously reported techniques, our technique does not attempt directly to dissect stroma but to detach the stromal layer from DM by injecting viscoelastic. Using this technique, among 172 eyes we achieved full-bed DLKP in 1 attempt of the procedure in 42 (24.4%) eyes, in 2 attempts in 65 (37.8%) eyes, and in 3 attempts in 45 (26.2%) eyes. Eighteen of 172 (10.5%) eyes had microperforation of DM, but DLKP surgery was nonetheless completed. Two (1.2%) eyes needed conversion to penetrating keratoplasty because of large perforation of DM. We present a detailed illustration of our surgical procedures for performing full-bed DLKP in the hope that it may be of help to ophthalmologists.

Use of a "small-bubble technique" to increase the success of Anwar's "big-bubble technique" for deep lamellar keratoplasty with complete baring of Descemet's membrane

PURPOSE

To describe a quick and simple "small-bubble" technique to immediately determine the success of attaining complete Descemet's membrane (DM) separation from corneal stroma through Anwar's "big-bubble" technique of deep anterior lamellar keratoplasty (DALK) for complete stromal removal.

METHODS

A partial trephination was followed by a lamellar dissection of the anterior stroma. Deep stromal air injection was then attempted to achieve the big bubble to help separate the stroma from the DM. To confirm that a big bubble had been achieved, a small air bubble was injected into the anterior chamber (AC) through a limbal paracentesis. If the small bubble is then seen at the corneal periphery, it confirms that the big-bubble separation of DM was successful because the convex nature of the bubble will cause it to protrude posteriorly, forcing the small AC bubble to the periphery. If the small AC bubble is not seen in the corneal periphery, this means that it is present in the centre, beneath the opaque corneal stroma, and therefore the big bubble has not been achieved.

RESULTS

We used the small-bubble technique to confirm the presence of the big bubble in three (one keratoconus, one interstitial keratitis and one dense corneal scar) out of 41 patients who underwent DALK. The small-bubble technique confirmed that the big bubble was achieved in the eye of all three patients. Complete stromal removal with baring of the DM was achieved, and postoperatively all three eyes achieved best corrected vision of 6/6.

CONCLUSION

The small-bubble technique can be a useful surgical tool for corneal surgeons attempting lamellar keratoplasty using the big-bubble technique. It helps in confirming the separation of DM from the deep stroma, which is important in achieving total stromal replacement. It will help to make the transition to lamellar keratoplasty smoother, enhance corneal graft success and improve visual outcomes in patients.

Deep anterior lamellar keratoplasty by big-bubble technique for treatment corneal stromal opacities

PURPOSE

To evaluate the efficacy of using the big-bubble technique of deep anterior lamellar keratoplasty (DALK) for newer indications.

DESIGN

Prospective, noncomparative, interventional case series.

METHODS

Ten eyes of eight patients with pathologies involving the corneal stroma and sparing the Descemet membrane (DM) were included in this study conducted at a tertiary care hospital. The indications for DALK included corneal clouding attributable to mucopolysaccharidoses (n = 2), macular corneal dystrophy (n = 5), lattice corneal dystrophy (n = 1), granular corneal dystrophy (n = 1), and stromal scar attributable to infectious keratitis (n = 1). DALK was performed using the big-bubble technique in order to achieve the complete separation of DM from the corneal stromal tissue in the recipient's eye. Subsequently, the corneal stromal tissue was excised completely, and a full-thickness donor corneal lenticule without its DM was secured over the bared DM of the host. The main outcome measures of the study were the ability to successfully bare DM, the gain in visual acuity, and the presence of any complications.

RESULTS

Using the big-bubble technique, DM was bared, and DALK could be performed successfully in all eyes. No intraoperative or postoperative complications were observed. All patients achieved a best-corrected visual acuity (BCVA) of 20/40 or better at the end of six months.

CONCLUSIONS

DALK using the big-bubble technique can be useful in treating corneal stromal dystrophies, corneal clouding attributable to mucopolysaccharidoses, and stromal scar attributable to infectious keratitis.

Graft failure: I. Endothelial cell loss

Graft failure through endothelial cell loss is a constant threat throughout the lifetime of a corneal graft. It can occur at various time points after transplantation. Primary graft failure has nowadays become increasingly rare owing to meticulous eye banking methods and improved surgical techniques. Corneal graft rejection is always held responsible for endothelial cell loss. However a rejection episode that is promptly and adequately treated does not necessarily lead to a higher than expected cell loss. A more smouldering danger to ultimate graft survival is late endothelial failure. This gradual graft decompensation is secondary to a decrease in cell density below that necessary to maintain corneal deturgesence. The process of transplantation itself seems to set off a series of events (possibly immunological) that greatly exacerbates the endothelial cell loss compared to virgin corneas. This accelerated cell loss persists for at least 10-15 years after transplantation, after which a more-stable situation is reached and cell attrition returns to normal rates. This provides a strong rationale for setting high donor standards of minimal cell density. Newer transplantation techniques such as deep anterior lamellar keratoplasty and deep lamellar endothelial keratoplasty could provide possible solutions to prevent this late endothelial failure. However they still have to prove themselves in the long run.