Endokeratoplasty as an alternative to penetrating keratoplasty for the surgical treatment of diseased endothelium: initial results

Twenty-Two-Year Clinical Outcome of a Case of Endokeratoplasty

PURPOSE

The purpose of this study was to report the 22-year clinical outcome of a patient who underwent endokeratoplasty.

METHODS

To report the clinical outcomes of 37-year-old male who underwent endokeratoplasty for decompensated Fuchs endothelial dystrophy in 1998.

RESULTS

After subsequent cataract surgery and iridoplasty, at 22 years post endokeratoplasty, the Snellen best spectacle-corrected visual acuity is 20/20 (-5.50 sphere -3.00 cylinder at 135 degrees), endothelial cell count is 645 cells/mm 2 , central corneal thickness is 644 μm, and the cornea remains clear with no evidence of graft rejection or failure.

CONCLUSIONS

To the best of our knowledge, this is the longest reported outcome for selective endothelial replacement. The patient undergoing endokeratoplasty can achieve an excellent visual acuity and long-term graft survival.

Loss of endothelial cells in viral DNA-positive grafts after keratoplasty: a 2-year follow-up study

BACKGROUND

To compare endothelial loss between recipients who received viral DNA-positive grafts and controls 2 years after corneal transplantation.

METHODS

We retrospectively analysed the clinical data and endothelial cell density of recipients of viral DNA-positive grafts and age-, sex-, aetiology- and operation-matched controls from April 2017 to July 2019 at the Peking University Third Hospital, Beijing, China.

RESULTS

A total of 23/942 (2.44%) donor corneal buttons tested virus-positive by real-time PCR. A total of 27 recipients (except for 2 recipients) of viral DNA-positive grafts and 48 recipients of viral DNA-negative grafts were included in this study. Recipients of viral DNA-positive grafts had a higher endothelial cell (EC) loss rate post-penetrating keratoplasty and post-descemet stripping automated endothelial keratoplasty (p<0.05), but post-deep lamellar keratoplasty, the EC loss rate was similar to that of the controls. Recipients of herpes simplex virus-1-, cytomegalovirus- and varicella-zoster virus-positive grafts all had a higher EC loss rate than the controls during the 12- and 24-month follow-up periods (p<0.05).

CONCLUSION

We inferred that viruses might be hidden in corneal grafts and mainly incubate in the corneal endothelium. Viral DNA-positive grafts do not need to be replaced immediately and can be followed up for a long time.

Cost-Effectiveness Analysis of Descemet's Membrane Endothelial Keratoplasty Versus Descemet's Stripping Endothelial Keratoplasty in the United States

PURPOSE

To determine the cost-effectiveness of Descemet's membrane endothelial keratoplasty (DMEK) compared with Descemet's stripping automated endothelial keratoplasty (DSAEK) in the United States.

DESIGN

Cost-effectiveness analysis in a surgical center in the United States.

PARTICIPANTS

Binocular adult patient undergoing endothelial keratoplasty.

METHODS

A base case of a 70-year-old man undergoing his first endothelial keratoplasty for bilateral Fuchs endothelial dystrophy. The cost-effectiveness of DMEK was compared with DSAEK over a 15-year time horizon. The incidences and costs of complications were derived from PubMed English literature searches, Medicare reimbursements, and average wholesale prices. All costs were discounted 3% per annum and adjusted for inflation to 2018 U.S. dollars. Uncertainty was evaluated using deterministic and probabilistic sensitivity analyses.

MAIN OUTCOME MEASURES

Incremental cost-effectiveness ratios and incremental cost-utility ratios, measured in cost per quality-adjusted life-years (QALYs).

RESULTS

Performing a DMEK instead of a DSAEK generated an extra 0.4 QALYs over a 15-year period. From a societal and third-party payer perspective, DMEK was cost-saving when compared with DSAEK in improving visual acuity in the base case. Probabilistic sensitivity analyses with variations in the costs and rebubble rates revealed that DMEK was cost-saving compared with DSAEK in 38% of iterations and was within a societal willingness-to-pay threshold of $50 000 in 98% of models.

CONCLUSIONS

From the societal and third-party payer perspectives in the United States, DMEK generated greater utilities and was less costly than DSAEK. Therefore, DMEK was the dominant procedure and was cost-saving with respect to DSAEK. The economic model was robust based on sensitivity analyses.

[Effect of donor graft characteristics on clinical outcomes in Descemet stripping automated endothelial keratoplasty (DSAEK)]

INTRODUCTION

The purpose of our study was to evaluate the progression of lamellar corneal grafts after endothelial keratoplasty by Descemet stripping automated endothelial keratoplasty (DSAEK) and the effect of their characteristics on the clinical and functional results.

MATERIALS AND METHODS

This was a prospective study in which 74 patients who had undergone endothelial keratoplasty by DSAEK were included. The corneal grafts were obtained from a French tissue bank and were delivered in a preservation medium containing a deturgescent agent (Corneajet^® or Stemalpha 3^®). Pachymetry of the corneal graft was measured ex vivo by ultrasonic pachymetry prior to dissection, then after the 1st or 2^nd cut as necessary. Corrected visual acuity in logMAR, total graft pachymetry, measured by anterior segment OCT (Spectralis^® HRA+SDOCT, Heidelberg engineering, Inc., Heidelberg, Germany) and corneal density (Pentacam^®, Oculus, Inc., Wetzlar, Germany) were obtained for each patient preoperatively, at D5, M1, M3, M6, M9 and M12.

RESULTS

Overall, 74 corneal grafts, from donors of mean age 69.7±13.3 years (37 to 92 years) were transplanted into 67 patients aged 70.3±12.1 years. Predissection pachymetry was statistically significantly thicker in the case of short deturgescence time (r=-0.383, P=0.001). For the same deturgescence time, predissection pachymetry was statistically significantly thicker in the Stemalpha 3^® medium (691±89μm for Corneajet^® vs. 760±100μm for Stemalpha 3^®, P=0.01), with the same final pachymetry (168±31μm vs. 166±25μm, P=0.833). Graft pachymetry and total corneal pachymetry decreased significantly between the preoperative measurement and M12 (168±29μm vs. 92±57μm, P=0.0008 et 665±124μm vs. 566±73μm, P=0.027 respectively). Preoperative endothelial cell density (2938±418 cells/mm²) did not correlate with postoperative visual acuity. There was a positive correlation between visual acuity at D5 and donor age (r=0.3, P=0.04). Postoperative visual acuity correlated positively with preoperative visual acuity (P<0.05). Corneal densitometry was statically higher than normal postoperative densitometry. Corneal density at M1 correlated positively with time since obtaining the donor tissue (r=0.373, P=0.043). There was no significant difference between the sub-groups of over or under 130μm. Seven patients experienced graft failure with no statistically significant graft risk factor.

DISCUSSION

The preservation medium affects predissection pachymetry with no consequence on clinical results. In our study, preoperative visual acuity and donor age were correlated with visual acuity after DSAEK.

CONCLUSION

Although donor age was associated with better visual acuity at D5, the other donor characteristics had no effect on clinical results.

Comparison of treatments for bullous keratopathy in rabbits

The aim of the present study was to compare deep lamellar endothelial keratoplasty (DLEK) and penetrating keratoplasty (PK) treatments for bullous keratopathy (BK). In total, 36 healthy New Zealand white rabbits were randomly divided into 3 groups termed the experimental, DLEK and PK groups. The experimental control group received no treatment. The DLEK and PK groups were observed for corneal astigmatism at 1, 2, or 3 months post-surgery using a corneal topography instrument and a slit lamp microscope. The incidence of immune rejection after 3 months of recovery was determined using hematoxylin and eosin (H&E) staining. The corneal specimens from the surgery groups were compared with those from the control group. In the 12 rabbit eyes that underwent the DLEK surgery, the central cornea became clear after 1 week. After 3 months, these corneas were almost transparent and no eye infections or other complications were observed in 10 of the eyes, while surgical perforations in 2 eyes led to surgical lamellar failure. In the PK surgery group, in which 12 rabbit eyes were also treated, nine were almost transparent after 3 months of recovery, while three eyes were immunologically rejected due to the corneal grafts. The occur-rences of corneal astigmatism that were observed following DLEK and PK treatment were significantly different after 1, 2 and 3 months of recovery (P<0.05). Normal corneal staining was observed in the DLEK and PK rabbits subjected to H&E staining after 3 months of recovery. A BK animal model was established by curetting the Descemet’s membrane (DM film). In comparison with PK, DLEK is a superior surgical treatment for BK.

Split cornea transplantation for 2 recipients - review of the first 100 consecutive patients

PURPOSE

To evaluate the feasibility of split cornea transplantation for 2 recipients by combining deep anterior lamellar keratoplasty (DALK) and Descemet membrane endothelial keratoplasty (DMEK).

DESIGN

Interventional case series.

METHODS

Fifty consecutive eyes with anterior stromal disease suitable for DALK and 50 eyes with endothelial disease suitable for DMEK were scheduled for split cornea transplantation combining both procedures within 72 hours. Main outcome measures included success of using a single donor cornea for 2 recipients, best spectacle-corrected visual acuity (BSCVA), and complication rates within 6 months' follow-up.

RESULTS

A single donor cornea could be used for 2 recipients in 47 cases (94%). In 3 eyes (6%), the DALK procedure had to be converted to penetrating keratoplasty (PK) requiring a full-thickness corneal graft. Thereby, 47 donor corneas (47%) could be saved. Six months after surgery, mean BSCVA was 20/36 in the 47 eyes that underwent successful DALK, 20/50 in the 3 eyes that underwent conversion from DALK to PK, and 20/29 in the 50 eyes that underwent DMEK. Postoperative complications after DALK included Descemet folds in 5 eyes (11%) and epitheliopathy in 3 eyes (6%). After DMEK, partial graft detachment occurred in 26 eyes (52%) and was managed successfully with intracameral air reinjection. All corneas remained clear up to 6 months after surgery. No intraocular infections occurred.

CONCLUSION

Split use of donor corneal tissue for combined DALK and DMEK procedures in 2 recipients within 3 subsequent days is a feasible approach to reduce donor shortage in corneal transplantation in the future.

Split cornea transplantation for 2 recipients: a new strategy to reduce corneal tissue cost and shortage

PURPOSE

To evaluate the feasibility of using a single donor cornea for 2 recipients by combining deep anterior lamellar keratoplasty (DALK) and Descemet's membrane endothelial keratoplasty (DMEK) surgeries on the same day.

DESIGN

Single-center, nonrandomized, prospective, interventional case series.

PARTICIPANTS

Twelve consecutive donor corneas were scheduled for split cornea transplantation combining DALK for a keratoconus patient and DMEK for a Fuchs' endothelial dystrophy patient on the same surgery day.

METHODS

First, a big-bubble DALK procedure was performed for the keratoconus eye. When bare Descemet's membrane was prepared successfully requiring no conversion to penetrating keratoplasty (PK), then during surgery the donor, endothelium-Descemet's membrane layer was removed and stored for subsequent DMEK in a second patient, and the remaining anterior lamella of the donor cornea was used to complete the DALK surgery. Afterward, a DMEK procedure was performed on the second patient with Fuchs' endothelial dystrophy, grafting the stored endothelium-Descemet's membrane layer of the original donor button.

MAIN OUTCOME MEASURES

Success of using a single donor cornea for 2 recipient eyes, best spectacle-corrected visual acuity (BSCVA), and complication rates within 6 months follow-up.

RESULTS

A single donor cornea could be used for 2 recipients in 10 of 12 donor buttons (83%). In 2 cases (17%), the DALK procedure had to be converted to PK requiring a full-thickness corneal graft. Therefore, 10 donor corneas (45%) could be saved. Six months after surgery, mean BSCVA was 20/35 (range, 20/50-20/25) in 10 eyes that underwent successful DALK, 20/50 (range, 20/63-20/40) in 2 eyes that underwent conversion from DALK to PK, and 20/31 (range, 20/50-20/16) in 10 eyes that underwent DMEK. Postoperative complications after DALK included Descemet's folds in 3 eyes (30%) and epitheliopathy in 2 eyes (20%). After DMEK, partial graft detachment occurred in 5 eyes (50%) and was managed successfully with intracameral air reinjection. All corneas remained clear up to 6 months after surgery.

CONCLUSIONS

Split use of donor corneal tissue for combined DALK and DMEK procedures in 2 recipients on the same surgery day is a promising strategy to reduce donor shortage and cost in corneal transplantation surgery in the future.

[Survey of complications in Descemet stripping automated endothelial keratoplasty in 32 eyes]

OBJECTIVE

To report complications during and after Descemet stripping automated endothelial keratoplasty (DSAEK) in 32 eyes at a single academic center with two techniques for delivering the endothelial corneal graft.

PATIENTS AND METHODS

Outcomes from a single center of 32 consecutives cases of DSAEK were analyzed prospectively. In the first 23 patients, the endothelial graft underwent single-fold delivery with forceps, and in the remaining nine patients, the graft was delivered with the Busin glide-based technique. The complications of DSAEK were noted from the intra- and postoperative periods.

RESULTS

Graft detachment was the most common type of complication encountered. In seven of 32 eyes (22%), graft detachments were observed. Three of the 32 eyes (9.5%) were considered to have failed DSAEK, meaning that persistent edema was present after DSAEK. One of the 32 eyes had a late corneal decompensation. Three eyes (9.5%) demonstrated graft rejection. Four eyes with detached grafts were successfully rebubbled after surgery. Two of the 32 eyes (6.2%) underwent repeat DSAEK and three eyes (9.5%) underwent penetrating keratoplasty.

CONCLUSIONS

DSAEK is becoming the preferred method for treating endothelial dysfunction because it maintains the structural integrity of the eye and provides rapid visual recovery with minimal refractive change. However, we experienced some complications. Graft detachment is the most common complication, but postoperative rebubbling allows for graft reattachment in most cases. Other common complications found in this series were graft failure and graft rejection.

Descemet's stripping endothelial keratoplasty: safety and outcomes: a report by the American Academy of Ophthalmology

OBJECTIVE

To review the published literature on safety and outcomes of Descemet's stripping endothelial keratoplasty (DSEK) for the surgical treatment of endothelial diseases of the cornea.

DESIGN

Peer-reviewed literature searches were conducted in PubMed and the Cochrane Library with the most recent search in February 2009. The searches yielded 2118 citations in English-language journals. The abstracts of these articles were reviewed and 131 articles were selected for possible clinical relevance, of which 34 were determined to be relevant to the assessment objectives.

RESULTS

The most common complications from DSEK among reviewed reports included posterior graft dislocations (mean, 14%; range, 0%-82%), followed by endothelial graft rejection (mean, 10%; range, 0%-45%), primary graft failure (mean, 5%; range, 0%-29%), and iatrogenic glaucoma (mean, 3%; range, 0%-15%). Average endothelial cell loss as measured by specular microscopy ranged from 25% to 54%, with an average cell loss of 37% at 6 months, and from 24% to 61%, with an average cell loss of 42% at 12 months. The average best-corrected Snellen visual acuity (mean, 9 months; range, 3-21 months) ranged from 20/34 to 20/66. A review of postoperative refractive results found induced hyperopia ranging from 0.7 to 1.5 diopters (D; mean, 1.1 D), with minimal induced astigmatism ranging from -0.4 to 0.6 D and a mean refractive shift of 0.11 D. A review of graft survival found that clear grafts at 1 year ranged from 55% to 100% (mean, 94%).

CONCLUSIONS

The evidence reviewed is supportive of DSEK being a safe and effective treatment for endothelial diseases of the cornea. In terms of surgical risks, complication rates, graft survival (clarity), visual acuity, and endothelial cell loss, DSEK appears similar to penetrating keratoplasty (PK). It seems to be superior to PK in terms of earlier visual recovery, refractive stability, postoperative refractive outcomes, wound and suture-related complications, and intraoperative and late suprachoroidal hemorrhage risk. The most common complications of DSEK do not appear to be detrimental to the ultimate vision recovery in most cases. Long-term endothelial cell survival and the risk of late endothelial rejection are beyond the scope of this assessment.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Descemet's stripping automated endothelial keratoplasty and penetrating keratoplasty for Fuchs' endothelial dystrophy

PURPOSE

To compare the outcome of Descemet's stripping endothelial keratoplasty (DSAEK) to that of penetrating keratoplasty (PK) in patients with Fuchs' endothelial dystrophy.

METHODS

The first 20 patients who underwent DSAEK at the Department of Ophthalmology, Aarhus University Hospital were compared to 20 patients treated with classic PK. Best-corrected visual acuity, subjective spectacle refraction and corneal thickness were registered before surgery and 1, 3, 6 and 12 months after DSAEK surgery; they were also measured before surgery and 12 months and 2-3 years after PK. Endothelial cell density was measured 12 months after surgery in both groups.

RESULTS

Two primary graft failures were observed in the DSAEK group; no failures were seen in the PK group. Best spectacle-corrected visual acuity (BSCVA) at 12 months after surgery was significantly better in the DSAEK group (0.56 +/- 0.04) than in the PK group (0.33 +/- 0.06). At this time, 70% of the DSAEK-treated eyes but only 25% of PK-treated eyes had obtained a BSCVA of 0.5 or better. Two to three years after surgery, BSCVA was 0.5 or better in 55% of PK-treated eyes. Refractive ametropia and astigmatism were significantly smaller in DSAEK-treated eyes than in PK-treated eyes, even after suture removal and arcuate keratotomy. Endothelial cell density (cells/mm2) after 1 year was lower in DSAEK-treated (1.338 +/- 113) than in PK-treated eyes (1.610 +/- 124), but the difference was not statistically significant.

CONCLUSION

DSAEK seems to be superior to PK in treating Fuchs' endothelial keratoplasty, although primary graft failure may be more common. Visual recovery is faster, and major ametropia and astigmatism is not induced. Long-term follow-up studies are essential to assess whether this conclusion also holds true more than 1 year after surgery.

Surgical alternatives to penetrating keratoplasty II: endothelial keratoplasty

Penetrating keratoplasty (PK) became the standard of care for optical and tectonic rehabilitation of corneal blindness and visual impairment in the second half of the twentieth century. Posterior corneal disorders or endotheliopathies are the reason for one-third to one-half of all corneal transplants today in the US. Any procedure that replaces the endothelium ideally should accomplish the following results: (1) a smooth surface topography without significant change in astigmatism, (2) a highly predictable corneal power, (3) a healthy donor endothelium that resolves all edema, (4) a tectonically stable globe, safe from injury and infection, and (5) an optically pure cornea. Although PK consistently can achieve results 3 and 5 above, the other goals of stable topography, predictable corneal power and tectonic stability, have remained elusive despite our best efforts at ingenious suturing and trephination techniques. Endothelial keratoplasty (EK) is a new surgical procedure designed to replace diseased corneal endothelium with healthy donor endothelium through either a lamellar corneal flap approach or through limbal scleral incision, leaving the surface of the recipient cornea untouched by surface corneal sutures. This manuscript evaluates the impact and future of EK in ophthalmology.

Early Postoperative Complications of Deep Lamellar Endothelial Keratoplasty

PURPOSE

To report and discuss the early postoperative complications of deep lamellar endothelial keratoplasty (DLEK).

METHODS

The records of the first 44 patients who underwent DLEK by 1 surgeon were reviewed. Complications occurring between the first day and eighth week after surgery were recorded.

RESULTS

In 6 patients (13.6%), the donor disc was floating in the anterior chamber on the first postoperative day and was repositioned with a 30-gauge needle. Fluid was present between the cornea and the disc in 8 patients (18.2%); in 6 of them, the fluid absorbed spontaneously. In 2 patients, the fluid was aspirated 1 month after surgery, but fibrosis developed in the interface. Two patients (4.5%) had persistent corneal edema. In 1 of them, the edema resolved after 2 months, but the other needed penetrating keratoplasty. One patient (2.3%) developed endothelial graft rejection when steroid treatment was discontinued because of exacerbation of preexisting glaucoma. Ten patients (22.7%) had elevated intraocular pressure (IOP) before surgery. The pressure was controlled with topical medication after surgery in 7 patients, 1 patient (mentioned above) suffered graft rejection, 1 patient underwent repeat trabeculectomy, and 1 patient needed insertion of a glaucoma valve. Three patients (6.8%) who did not have glaucoma before surgery developed elevated IOP postoperatively, which was controlled with topical medication.

CONCLUSION

Non-adhesion of the disc and elevated IOP were the most common complications after DLEK. The mechanical preparation of a thinner donor disc and more experience may lead to fewer postoperative complications and their more efficient management.

Microkeratome-assisted Posterior Lamellar Keratoplasty in Pseudophakic and Aphakic Corneal Edema

PURPOSE

To evaluate the outcome of microkeratome-assisted posterior lamellar keratoplasty for replacing diseased endothelium in pseudophakic and aphakic corneal edema.

METHODS

Microkeratome-assisted posterior lamellar keratoplasty was performed on 10 eyes with pseudophakic or aphakic corneal edema. A nasal hinged 130- to 250-microm-thick flap was created with an automated microkeratome. The underlying 7.0-mm trephined button of deep stroma and endothelium was substituted with the same size donor button prepared by removing a same-sized flap and trephination of the remaining donor bed. The donor lenticule was fixated without sutures in position; the retracted flap was repositioned and sutured to the peripheral recipient tissue. The viscoelastic content of the anterior chamber was replaced by air to hold the graft in position.

RESULTS

All surgeries were uneventful except for one case of donor button posterior dislocation forming a secondary anterior chamber, which was corrected through donor button exchange 1 month postoperatively. All uncomplicated cases had stable refraction and corneal topography as early as 1 month after surgery, which was maintained in follow-up examinations. In two eyes, corneal astigmatism > 5.00 diopters was recorded. One case of prolonged re-epithelialization and two cases of epithelial interface ingrowth occurred.

CONCLUSIONS

Microkeratome-assisted posterior lamellar keratoplasty is an alternative to conventional penetrating keratoplasty for patients with diseased corneal endothelium, significantly reducing the time of visual rehabilitation. Determination of the relative advantages of this technique over penetrating keratoplasty and other recent alternative endothelial graft procedures relies on controlled prospective studies.

Pseudophakic corneal edema: A review of mechanisms and treatments

PURPOSE

To review the pathological mechanisms and treatments for pseudophakic corneal edema (PCE), one of the most common indications for penetrating keratoplasty.

METHODS

The literature was examined for the molecular biology associated with PCE and for the surgical and medical treatments for this disorder.

RESULTS

The incidence of PCE has recently been decreasing because of improved surgical instrumentation, including improvements in intraocular lens designs that cause less trauma to the corneal endothelium. Extracellular matrix and growth factor abnormalities occur in PCE corneas and recently, the role of aquaporins, which are involved in the regulation of fluid movement across cells, has been investigated.

CONCLUSIONS

Although newer treatment options have been suggested, penetrating keratoplasty still remains the most definitive treatment and has the highest success rate.

In Vivo Femtosecond Laser-Assisted Posterior Lamellar Keratoplasty in Rabbits

PURPOSE

To develop a rabbit model for femtosecond laser-assisted posterior lamellar keratoplasty.

METHODS

The femtosecond laser was used to make the posterior corneal lamellar interface and trephine (side) cut in 12 eyes of 11 rabbits. Laser parameters were energy 6.0 to 8.7 (lamellar cut) and 6.0 to 8.8 microJ (trephination cut), spot size 2.4 microm, firing rate 15 kHz, and trephination diameter 6.0 to 7.0 mm. In all eyes, the posterior corneal disc was removed from the eye after laser treatment through a blade incision in the peripheral cornea. The same excised corneal disc was repositioned into the posterior stromal bed to simulate posterior lamellar transplantation. Four eyes of 3 rabbits were enucleated immediately after surgery, and 8 eyes of 8 rabbits were enucleated after a mean follow-up of 17.9 +/- 6.5 weeks. The corneal cut surfaces were examined by light microscopy and scanning electron microscopy.

RESULTS

The femtosecond laser was successful in producing posterior lamellar and trephination cuts in rabbit eyes. The thickness of the posterior corneal discs was 204.3 +/- 21 microm (56.9% of central corneal thickness), and postoperative keratometry was 49.1 +/- 5.8 D. Clinical appearance consistent with corneal ectasia was noted in 3 eyes.

CONCLUSION

The femtosecond laser can make nonmechanical cuts for posterior lamellar keratoplasty with relative ease and reliability in rabbit eyes. A minimum residual anterior corneal thickness may need to be maintained to prevent ectasia.

Finite-Element Modeling of Posterior Lamellar Keratoplasty: Construction of Theoretical Nomograms for Induced Refractive Errors

PURPOSE

To estimate the theoretical corneal refractive error induced by mechanical weakening effects from posterior lamellar keratoplasty (PLKP) in the human cornea.

METHODS

The refractive effects of PLKP are simulated by finite-element modeling (FEM) as a mathematical function of the thickness of the excised posterior lamellar corneal button, with a nonlinear formulation of stress-strain relation for the corneal material. A theoretical nomogram was developed to correlate the refractive changes to button thickness.

RESULTS

The predicted refractive change after PLKP is less than 1 dpt for a 170-microm thickness posterior corneal button over a broad range of Young's modulus. Thicker buttons result in greater surgically induced refractive errors.

CONCLUSIONS

According to FEM analysis, the excision of a posterior lamellar button of less than 170 microm thickness produces a minimal predicted refractive change (< 1 dpt) in the cornea after PLKP.

Microkeratome assisted deep lamellar keratoprosthesis

AIMS

To establish a keratoprosthesis (Kpro) surgical technique that maintains an intact superficial corneal layer.

METHODS

A manual microkeratome (Moria LSK-1) was used to create a 130 mum flap of approximately 10 mm diameter in the right eye of Japanese white rabbits. The stoma beneath the flap area was dissected before the removal of a 5.0 mm stromal disc. A 5.0 mm collagen I immobilised poly(vinyl alcohol) (COL-PVA) disc was placed on the exposed posterior stroma close to Descemet's membrane. The flap was repositioned and fixed using 10-0 nylon sutures, which were removed 2 days following surgery. The corneas were followed clinically by slit lamp microscopy and photographs. Rabbits were sacrificed after 6 months, and the transplanted corneas were examined histologically by haematoxylin and eosin staining and immunohistochemistry against vimentin and alpha-smooth muscle actin (alpha-SMA).

RESULTS

The transplanted COL-PVA discs remained transparent throughout the study, with no complications related to the flap or overlying epithelium. The interface between COL-PVA and Descemet's membrane remained clear without signs of opacification caused by scarring or cellular deposition. Pathology revealed the intact COL-PVA polymer in the posterior stroma, with minimal cellular infiltration along the anterior and posterior interfaces. Immunohistology shows vimentin and alpha-SMA staining at levels comparable to lamellar keratoplasty control.

CONCLUSIONS

Microkeratome assisted deep lamellar keratoprosthesis may be a safe technique for the transplantation of artificial hydrogels for therapeutic purposes.

Biomechanical Model of Corneal Transplantation

PURPOSE

Refractive consequences of corneal transplants are analyzed using corneal biomechanical models assuming homogeneous and inhomogeneous stiffness distributions across the cornea. Additionally, refractive effects of grafts combined with volume removal procedures are also evaluated to develop methods to reduce postoperative refractive management of patients.

METHODS

Refinements of a two-dimensional finite element model are applied to simulate the biomechanical and refractive effects of different corneal transplant procedures: anterior lamellar keratoplasty, posterior lamellar keratoplasty, and penetrating keratoplasty. The models are based on a nonlinearly elastic, isotropic formulation. Predictions are compared with published clinical data.

RESULTS

The model simulating the penetrating keratoplasty procedure predicts more change in the postoperative corneal curvature than models simulating anterior lamellar keratoplasty or posterior lamellar keratoplasty procedures. When a lenticle-shaped tissue with a central thickness of 50 microns and a diameter of 4 mm is removed from the anterior corneal surface along with the anterior lamellar keratoplasty or posterior lamellar keratoplasty, the models predict a refractive correction of -8.6 and -8.9 diopters, respectively.

CONCLUSIONS

Simulations indicate that a posterior lamellar keratoplasty procedure is preferable for obtaining a better corneal curvature profile, eliminating the need for specific secondary treatments.

Initial results of small incision deep lamellar endothelial keratoplasty (DLEK)

PURPOSE

To evaluate the results of replacing the posterior stroma and endothelium, using small incision deep lamellar endothelial keratoplasty (DLEK) surgical technique, in patients with corneal endothelial dysfunction.

DESIGN

Noncomparative case series.

METHODS

Fifteen eyes of 15 patients (six males and nine females) with endothelial dysfunction were included in this study. Through a 5-mm scleral incision, a deep lamellar pocket was created across the cornea, followed by excision of an 8.0-mm disk of posterior lamellar corneal tissue. Same size lamellar donor disk was prepared and placed in position without the need of suture fixation. Best spectacle-corrected visual acuity (BSCVA), refraction, endothelial cell density, corneal topography, and corneal thickness were analyzed.

RESULTS

Average BSCVA preoperative was 20/200 (range 20/40 to hand movements (HM)), improving to 20/50 (range 20/20 to 20/120) at a mean follow-up of 7.2 months. Average refractive astigmatism at last follow-up was 1.46+/-1.21 diopters (range, 0 to 4 diopters). Preoperative average donor endothelial cell density was 2047+/-311 cells/mm2, and that at last follow-up was 1732+/-514 cells/mm2. Preoperative average pachymetry was 801.4+/-211.3 microm, improving to 553+/-90.4 microm at last follow-up.

CONCLUSIONS

Initial results with small incision DLEK procedure indicate that it is a safe procedure that provides healthy donor endothelial cell count and function postoperatively, with encouraging visual results.

Lamelläre Keratoplastik

In 1840 Mühlbauer was the first to describe a technique for anterior lamellar keratoplasty (LKP). However, in the second half of the twentieth century penetrating keratoplasty (PKP) became the gold standard. Although it is associated with a higher risk for serious complications -- it is technically easier to perform and avoids wound healing reactions in the lamellar interface and thus resulting in better visual acuity. In view of the pathology, replacing all layers of the cornea including healthy parts can be considered therapeutic "overkill" for many corneal graft indications. Several innovative surgical techniques have recently been described which allow the lamellar dissection of recipient and donor cornea with good reproducibility in almost every desired depth. This now allows the recipient endothelium and Descemet's membrane to be selectively replaced or preserved and to avoid formation of an optical barrier in the lamellar interface in eyes undergoing lamellar keratoplasty for optical indications. The most important principal advantage of an anterior LKP -- to minimize the risk of an immune reaction in the graft -- is even more important in tectonic indications. From the large number of variations, the surgical technique, results, and problems with anterior and posterior LKP for optical indications as well as lamellar segment keratoplasty and epikeratoplasty for tectonic indications are discussed.

Central Penetrating Keratoplasty With Peripheral Intrastromal Tuck

PURPOSE

To report a new technique of central penetrating keratoplasty with peripheral intrastromal tuck in cases of chronic corneal decompensation.

METHODS

Central penetrating keratoplasty with peripheral intrastromal tuck was undertaken in 8 eyes with chronic corneal decompensation. An 8-mm donor tissue with a peripheral flange of 2 mm was fashioned and sutured into a 7.5-mm recipient bed having a 2-mm intralamellar pocket. Sixteen full-thickness interrupted sutures were passed. Suture removal was possible as early as 1 month, and all sutures were removed by 4 months.

RESULTS

Postoperative BCVA improved to 20/40 to 20/80 in all eyes, and astigmatism was <4 diopters in all cases at the last follow-up, which ranged from 5 to 16 months.

CONCLUSIONS

Central penetrating keratoplasty with peripheral intrastromal tuck is a useful technique because it allows early suture removal and visual rehabilitation.

A risk score as part of an evidence-based approach to the selection of corneal replacement surgery

PURPOSE

There is currently no standardized methodology that permits preoperative prediction of the surgical technique or drug regimen for corneal grafting most likely to succeed for an individual patient. A score factor related to the chance of successful penetrating keratoplasty (PK) may assist in standardization of graft outcome reporting and evidence-based management.

METHODS

The Risk Score (RS) is based on factors shown to reduce the probability of 1-year survival of conventional PK in increments, using published Australian Corneal Graft Registry data. To asses its validity, Kaplan-Meier survival curves from 156 corneal replacement surgeries, stratified by preoperative RS, were used to derive the probability of survival at 1 year for donor PK, with or without systemic immunosuppression, and for synthetic PK with the AlphaCor artificial cornea. The probability of survival was then plotted against RS for each regimen, producing a family of curves.

RESULTS

The mean RS for immunosuppressed cases was higher than for nonimmunosuppressed cases. The AlphaCor group had the highest scores. AlphaCor survival is little affected by the factors that affect the risk of graft survival, whereas the probability of donor graft survival, immunosuppressed or not, is inversely related to RS.

CONCLUSIONS

This study was designed to test a method that allows objective comparison of outcomes of different methods of corneal replacement for different risk categories. Analysis of this small dataset supports the validity of the concept and suggests that the Risk Score is a useful descriptive statistic. With a sufficient sample size, statistically significant evidence of the optimum management method for an individual patient with a particular risk profile could be determined such that a prospective patient's preoperative RS could be used to assist management decisions. In particular, data allowing separation of different immunosuppression regimes would be useful. Functional outcomes such as visual acuity would be more significant clinically than the survival end point used in this study and the system also could be adapted to different follow-up periods.

Femtosecond Laser Posterior Lamellar Keratoplasty

PURPOSE

To evaluate feasibility of femtosecond laser application in posterior lamellar keratoplasty.

METHODS

To evaluate the laser's effectiveness through opaque corneas, anterior corneal caps were resected from opaque corneas induced with 80% acetone solution. To evaluate the femtosecond laser posterior lamellar keratoplasty surgical procedure, human corneoscleral rims were mounted on an artificial anterior chamber. After corneal pachymetry, the femtosecond laser was used to create a 6-mm-diameter, 200-microm-thick endostromal lenticule. Access to the lenticule was provided by a small perilimbal surface opening, also created by the laser. The lenticule was removed using a pair of corneal forceps. A donor lenticule of similar dimensions was created, its endothelial surface coated with viscoelastic, inserted, and positioned on the recipient bed. Two sutures were placed to seal the small surface opening.

RESULTS

The femtosecond laser produced an effective and smooth dissection through opaque corneas even at deeper settings. Graft transplantation was fairly simple and effective.

CONCLUSION

Femtosecond laser posterior lamellar keratoplasty is a procedure that may provide an alternative to penetrating keratoplasty or the technically challenging manual posterior lamellar keratoplasty.

Long-term outcome of iron-endocytosing cultured corneal endothelial cell transplantation with magnetic attraction

The long-term efficacy and safety of transplanting iron-endocytosing cultured corneal endothelial cells (CECs) with magnetic attraction were evaluated. Rabbit corneas were subjected to cryo-injury to detach CECs. Cultured rabbit CECs (RCEC) were exposed to spherical iron powder and then injected into the anterior chamber, after which a neogium magnet was fixed on the eyelid for 24 hr to attract the cells to Descemet's membrane (RCEC-iron group, n=4). An RCEC group (cryo-injury and injection of normal cultured RCEC, n=4) and a Cryo group (cryo-injury without injection of RCEC, n=4) served as controls. Intraocular pressure was measured for 12 months after surgery. Corneal findings on slit lamp biomicroscopy, RCEC density, the electro-retinogram (ERG), and residual iron in the ocular tissues were evaluated at final assessment. Intraocular pressure did not increase in any group throughout 12 months of observation. At the final assessment, the average corneal edema score of the RCEC-iron group was significantly lower than that of the RCEC or Cryo groups (p=0.021). The average CEC density of the RCEC-iron group was 2581+/-230 cells mm(-2) (mean+/-SD), whereas no CECs were observed on the inner surface of the central cornea in the RCEC and Cryo groups. No significant differences of the ERG (a- and b-wave amplitudes, and b-wave/a-wave ratio) were detected among the groups. Iron powder was not detected by Berlin blue staining in the ocular tissues of the RCEC-iron group. Apoptotic cells were not observed in the endothelium by terminal transferase-mediated nick-end labeling. Transplanted iron-endocytosing RCEC remained viable for 12 months after surgery. There were no detectable ocular complications after the transplantation of iron-endocytosing cultured RCEC. Magnetic attachment of iron-endocytosing CECs can be an effective and safe method for corneal endothelial repair.

Transplantation of corneal endothelium with Descemet's membrane using a hyroxyethyl methacrylate polymer as a carrier

AIMS

To evaluate the histology and function of Descemet's membrane transplanted with intact endothelium.

METHODS

Japanese white rabbits and human eyebank eyes were used as donors and recipients of Descemet's membrane transplantation. Donor endothelium was hydrodissected by injecting indocyanine green from a limbal incision, and then processed as a corneal scleral button. A 6 mm diameter donor sheet was trephined, and folded in half using a 6 mm diameter polymer as a carrier. Recipient endothelium was also hydrodissected from the limbus using trypan blue to stain the Descemet's membrane. Continuous curvilinear descemetorhexis (CCD) was performed to remove a circular section of the Descemet's membrane using a 27 gauge cystotome. Donor tissue was inserted into the anterior chamber through a 5 mm limbal incision and apposed to the host stroma. Polymers were removed following transplantation. Similar surgical procedures were performed in both rabbits and eyebank eyes. Haematoxylin eosin stains were performed after 28 days in rabbits, and eyebank eyes were fixed immediately following surgery for endothelial cell counts.

RESULTS

Rabbit control eyes demonstrated stromal oedema caused by loss of Descemet's membrane, whereas transplanted eyes had clear corneas. The mean (standard deviation) pachymetry of operated eyes was 376.6 (SD 32.5) mum compared with 389.6 (SD 25.1) mum in the unoperated eye. Mean endothelial density immediately following surgery in eyebank eyes was 2749 (SD 288) cells/mm(2).

CONCLUSIONS

Transplantation of Descemet's membrane by CCD produces a functional graft with an optically clear interface similar to control cornea.

A technique to harvest Descemet's membrane with viable endothelial cells for selective transplantation

PURPOSE

To describe a surgical technique using an artificial anterior chamber to facilitate harvest of Descemet's membrane (DM) and endothelium for corneal endothelial cell transplantation.

DESIGN

Laboratory investigation.

METHODS

Corneoscleral buttons of seven human donor eyes were mounted endothelial side up on an artificial anterior chamber. Keeping the endothelial side with its usual concavity, a manual trephination was made on the posterior surface with a 9.0-mm trephine, inside the Schwalbe line and just past the DM in depth. The chamber was filled with air, causing the endothelial side of the donor cornea to assume a convex configuration. The DM along with its endothelium was separated from the posterior stroma using a blunt cyclodialysis spatula. Drops of trypan blue 0.3% and alizarin red S 0.2% (n = 6) were applied. The stained DMs were examined under a light microscope and photographed to calculate the percentage of endothelial cell damage. Histology was done on the unstained cornea.

RESULTS

The DM carrying endothelium was successfully removed from the posterior stroma in all seven eyes. Although the DM appears to be very friable, all samples were removed in toto without rupture. Vital staining showed a mean endothelial cell loss of 8.46% (standard deviation (SD) 6.9). Direct light microscopy demonstrated the preservation of endothelial cell morphology.

CONCLUSIONS

This technique appears to be a safe and straightforward method to harvest DM for endothelial cell transplantation. Further studies are underway to determine the optimal method of insertion of the obtained healthy DM with endothelial cells through small corneal incisions.

Component Surgery of the Cornea

Penetrating keratoplasty (PKP) has long been the standard procedure for treating irreversible opacification of the cornea from various diseases. The success rate of PKP is high compared with those in other organ transplants because of the low incidence of immunologic rejection. However, once rejection does occur, secondary procedures are inevitably less successful. Cases with vascularized corneas are also prone to undergo rejection, and severe disease causing total destruction of limbal tissue is considered a contraindication for surgery. Recent advances in corneal surgery aim at reducing surgical trauma to the host cornea by replacing only necessary cells and tissue. This approach not only reduces the risk of immunologic rejection but may also yield better refractive results. The various transplantable "components" of the cornea include the epithelium, epithelial stem cells, stroma, and endothelium. Cells from these components can be transplanted as lamellar sections of donor cornea or as sheets using biologic carriers and scaffolds. Procedures such as epithelial sheet transplants using amniotic membrane carriers, deep lamellar keratoplasty, and endothelial lamellar keratoplasty are already in clinical practice. Further refinements in technology will certainly take the limits of corneal surgery to new horizons.

Corneal Endothelial Transplantation

PURPOSE

We present the results of our clinical series replacing posterior stroma and endothelium only by deep lamellar endothelial keratoplasty (DLEK) in patients with corneal endothelial diseases.

METHODS

Through a 9.0-mm superior scleral incision, a deep stromal pocket was created across the cornea. A 7.5-mm posterior lamellar disc of recipient tissue was excised and replaced by same-size donor posterior disc without suture fixation. Three cases were followed for 12 months after DLEK. Best spectacle-corrected visual acuity (BSCVA), endothelial cell density, and corneal thickness were examined.

RESULTS

At 12 months after surgery, all transplants were clear and in position. In the 3 cases, BSCVA at 12 months was 20/200 (hand motion before operation), 20/50 (6/200 before operation), and 20/60 (20/250 before operation), respectively. In one patient, postoperative endothelial cell density was 533 cells/mm(2) with a very thin donor disc. In the other two patients, postoperative endothelial cell density was >2000 cells/mm(2). Corneal thickness (+/-SD) averaged 0.51 +/- 0.06 mm.

CONCLUSIONS

DLEK in the setting of corneal endothelial diseases is an effective surgical procedure without corneal surface incisions and sutures.

A Portable Microkeratome for Harvesting the Human Anterior Corneal Surface

A portable, gas-driven turbine microkeratome device capable of harvesting the entire anterior corneal surface for lamellar transplantation on human donor globes was evaluated. The device consisted of a modified LASIK microkeratome with an enlarged suction ring, head, and blade. Vacuum was achieved by a simple hand pump. Lamellar keratectomy was performed on 5 fresh human donor globes. Lenticule dimensions were measured on days 0, 3, 6, and 9 after storage in preservation media at 4 degrees C. On day 0, the obtained lenticules were 13.9 +/- 0.9 mm and 13.5 +/- 0.4 mm, vertical and horizontal diameters, respectively. The average central lenticule thickness was 152.2 +/- 52 microm. Each lenticule was uniform in thickness over 5 measurement points (P = 0.74). Repeat measurements of corneal thickness over the 9 days showed no statistically significant difference (P = 0.51). On day 9 lenticules were 14.6 +/- 0.3 mm and 14.6 +/- 0.4 mm, vertical and horizontal diameters, respectively. When day 0 was compared to day 9, vertical diameter also showed no statistically significant difference (P = 0.16), whereas horizontal diameter was significantly different (P < 0.001). This device proves to be an economical alternative to electric-powered systems for the harvest of transplantable corneal sections.

A Technique to Excise the Descemet Membrane From a Recipient Cornea (Descemetorhexis)

OBJECTIVE

To describe a technique for excision of the Descemet membrane (DM) from the recipient eye for preparation of a recipient stromal bed in posterior lamellar keratoplasty.

METHODS

In 10 human eye bank eyes and 3 patients, recipient eyes had a 5.0-mm scleral tunnel incision made extending 1.0 mm into the peripheral cornea at the 12 o'clock surgical position. The anterior chamber was completely filled with air, and a reflective glide was placed through the incision onto the iris, to better visualize DM. A 9.0-mm mark was made onto the corneal epithelium to outline the area from which the Descemet membrane was to be removed. With a custom-made scraper, the DM was then carefully stripped off the posterior stroma by loosening the membrane at the 6 o'clock position and pulling it toward the incision at 12 o'clock. The excised DMs were evaluated by light and electron microscopy.

RESULTS

In all recipient eyes, DM could be easily and completely removed from the posterior corneal stroma. Microscopy showed isolated DMs without stromal tissue elements.

CONCLUSION

With the technique described, DM can be excised in a controlled fashion without damaging the posterior corneal stroma, to quickly create a recipient stromal bed before implantation of a donor posterior lamellar disk in posterior lamellar keratoplasty.