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Laboratory Sciences |

Modified Microkeratome-Assisted Posterior Lamellar Keratoplasty Using a Tissue Adhesive FREE

Ashkan Pirouzmanesh, MD; Samantha Herretes, MD; Johann M. G. Reyes, MD; Olan Suwan-apichon, MD; Roy S. Chuck, MD, PhD; Dong-An Wang, PhD; Jennifer H. Elisseeff, PhD; Walter J. Stark, MD; Ashley Behrens, MD
[+] Author Affiliations

Author Affiliations: Wilmer Ophthalmological Institute (Drs Pirouzmanesh, Herretes, Reyes, Suwan-apichon, Chuck, Stark, and Behrens) and Departments of Cell Biology and Biomedical Engineering (Drs Wang and Elisseeff), Johns Hopkins University, Baltimore, Md.


Arch Ophthalmol. 2006;124(2):210-214. doi:10.1001/archopht.124.2.210.
Text Size: A A A
Published online

Objective  To compare graft stability and astigmatic change using suture vs tissue adhesive in an experimental model of microkeratome-assisted posterior lamellar keratoplasty.

Methods  A 300-μm-thick partial flap keratectomy was performed in human donor corneoscleral rims using an artificial anterior chamber and a manual microkeratome. The flap stopped at the left central opening border, providing a wide hinge to add stability. After flap reflection, a 6.25-mm trephination was performed to obtain a disc of posterior stroma, Descemet membrane, and endothelium. The disc was positioned in a sutureless fashion, and the flap secured with either 5 interrupted sutures or a chondroitin-sulfate-aldehyde–based adhesive. Increasing intrachamber pressures were created to detect graft stability. Videokeratographic data were recorded to evaluate astigmatic change.

Results  The mean (SD) astigmatic change was 3.08 (0.84) diopters (D) in the sutured group and 1.13 (0.55) D in the glued group (P = .008). Mean (SD) resisted pressures were 95.68 (27.38) mm Hg and 82.45 (18.40) mm Hg in the sutured and glued groups, respectively (P = .97).

Conclusion  This modified technique of microkeratome-assisted posterior lamellar keratoplasty showed excellent graft stability in both groups. Flaps sealed with the novel tissue adhesive had reduced astigmatic changes in our experimental model.

Clinical Relevance  Sutureless microkeratome-assisted posterior lamellar keratoplasty using tissue adhesive may become a new alternative in the surgical treatment of corneal endothelial disorders.

Figures in this Article

Endothelial cell dysfunction accounts for most penetrating keratoplasties performed in developed countries.1 Endothelial cell failure has been frequently associated with ocular trauma after intraocular lens implantation and endothelial corneal dystrophies.2,3

At present, surgical treatment of corneal endothelial decompensation is limited to penetrating keratoplasty. Penetrating keratoplasty is a safe and effective method for restoring corneal transparency in patients with disabling corneal opacities.46 However, recovery is prolonged, and visual rehabilitation is often hampered by high-degree astigmatism.7,8 Some authors have attempted endothelial cell transplantation,9,10 and present clinical applications appear to be feasible only using a posterior stromal lamellar carrier (posterior lamellar keratoplasty [PLK]). In this approach, replacement of the posterior stroma, Descemet membrane, and endothelial cell layer is accomplished through a scleral pocket.1114 The technique has shown promising results. However, it is laborious and requires a highly skilled surgeon.

Instruments used for laser-assisted in situ keratomileusis can also be used to perform posterior lamellar transplantation using a corneal flap technique.15 Several recent studies have shown promising results using these procedures in human subjects.1618 Advantages as compared with penetrating keratoplasty include preservation of the original central corneal surface, avoidance of extensive superficial suturing, and a decrease in the thickness of the tissue transplanted.

In this experimental model, we attempt to develop a modified PLK using a manually guided microkeratome and an artificial anterior chamber. The purpose of the study was to compare the graft stability and astigmatic change using 2 types of wound closure techniques: standard suturing vs a novel chondroitin-sulfate–based corneal adhesive.

DONOR TISSUE

After receiving approval by the institutional review board of the Johns Hopkins University, Baltimore, Md, we obtained donor corneoscleral rims (n = 8) not suitable for transplantation from the Central Florida Lions Eye and Tissue Bank, Tampa. Corneas were preserved under standard eye bank conditions and kept hydrated in Optisol-GS medium (Bausch & Lomb Surgical, Inc, San Dimas, Calif) at 4°C. The procedure was performed no longer than 10 days after death. Demographic data are shown in Table 1.

Table Graphic Jump LocationTable 1. Data Collected From Corneas
EXPERIMENTAL SETTING

A manual microkeratome (LSK One; Moria USA, Doylestown, Pa) was used to perform a hinged-flap keratectomy just past the central opening of the chamber in a way that created a large hinge. This opening is similar to an artificial nondilated pupil, which could be the reference point in a clinical setting. A 300-μm head thickness was used in all corneas. An artificial anterior chamber (ALTK System; Moria USA) was used to support the corneoscleral rims as described in previous reports.16,19,20 The gearless tracks on the base plate of the artificial anterior chamber were designed to fit into the microkeratome head so that its pass across the cornea maintains the same plane and direction. All discs with posterior stroma, Descemet membrane, and endothelial cell layer were obtained using a 6.25-mm freehand trephine. Intrachamber pressures were recorded using a digital manometer (Digimano 1000, Netech Corp, Hicksville, NY). The artificial anterior chamber was connected to an infusion system with a Balanced Salt Solution bag (Abbott Laboratories, Chicago, Ill). The height of the bag was adjusted accordingly using a modified pulley system to obtain the desired intrachamber pressure.

SURGICAL TECHNIQUE

An infusion of isotonic sodium chloride was released before the corneoscleral rims were placed on the base of the anterior chamber to clear the residual air from both the infusion line and underneath the cornea. The solution bottle was raised 1.5 m above the level of the chamber to obtain adequate intrachamber pressures (60-70 mm Hg) for the microkeratome pass. Corneas were centered according to circular guides in the base of the chamber. Mechanical epithelial scraping was performed with a new 2.5-mm, straight, rounded-tip crescent knife (Beaver; Beckton Dickinson Surgical Systems, Franklin Lakes, NJ) to avoid surface irregularities due to loose epithelium, which may introduce errors in pachymetric and videokeratographic measurements.

The artificial anterior chamber was set to achieve a maximal flap diameter in all cases using the diameter setting lens (ALTK System). The maneuver was intended to leave as much area in the stromal bed as possible for performing the trephination and suturing of the flap. The surgeries were all performed by the same experienced surgeon using a surgical microscope to avoid variability related to different surgeons (Ophthalmic 900S; Moeller-Wedel, Hamburg, Germany).

Several drops of 0.5% proparacaine hydrochloride were applied to the corneal surface prior to the microkeratome pass to approximate clinical conditions. A partial flap keratectomy was performed by passing the microkeratome head with its oscillating blade at a relatively constant speed across the plate, stopping just past the central opening of the chamber. A new blade was used to perform each surgery. Differing from previously published techniques, this approach attempts to obtain a wide flap hinge with a relatively less likelihood of flap slippage to provide more stability to the corneal flap and reduce the corneal opening (Figure 1).16,19,20 The remaining stroma underneath the flap hinge was severed using a 2-mm-wide Culler iris spatula (Sparta Surgical Corporation, Concord, Calif) to leave adequate space to perform a central trephination. Intrachamber pressure was returned to 18 to 20 mm Hg by lowering the height of the isotonic sodium chloride solution bottle to 25 cm above the cornea level, and the trephine was centered according to the keratectomy and “pupillary” edge provided artificially by the central opening of the chamber. A hand trephine of 6.25 mm in diameter was used to perform a circular cut of the stromal bed. The trephine blade was carefully rotated until perforation and the remaining circular cut completed with corneal scissors. Donor buttons were placed in the recipient beds and left unsutured, and the flap was repositioned.

Place holder to copy figure label and caption
Figure 1.

Surgical steps. A, After flap creation. Note the large flap hinge (arrows) in a partial flap pass. B, Dissection of the area under the hinge (arrows and line) with spatula in a shape that accommodates the trephine blade. C, Stromal bed after trephination of the posterior stroma and endothelium with flap reflected and trephination opening (arrows). D, Sutureless donor disc in place, flap repositioned, and glue (blue color) at the wound edges. The superficial wound is limited by the hinge (arrows). The corneal disc is in place without sutures (arrowheads).

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STUDY GROUPS

The experiment consisted of 2 groups of 4 corneas each. In 1 group (group 1), the flap was secured with 5 interrupted 10-0 nylon sutures (Sharpoint Surgical Specialties Corporation, Reading, Pa) (Figure 2). The suturing technique was the same in all corneas to ensure consistency. In the second group (group 2), the flap was secured using an experimental tissue adhesive based on chondroitin sulfate. The chemical basis of this adhesive is available elsewhere.21 In both groups, the transplanted disc was left without sutures or glue because it tends to stay in place by surface tension after the intrachamber pressure reaches 15 to 18 mm Hg.

Place holder to copy figure label and caption
Figure 2.

Postoperative view, suture group. The flap keratectomy is held in place by 5 interrupted 10-0 nylon sutures. The disc with posterior stroma and endothelium is secured underneath the flap without sutures.

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MEASUREMENTS

After epithelium removal, the isotonic sodium chloride infusion was closed, and corneal thickness was measured using an ultrasound pachymeter (Pach IV; Accutome Inc, Malvern, Pa). The ultrasound probe was lightly opposed to the center of each cornea, obtaining an average of 5 different readings. A second measurement was made after the hinged flap was created and reflected from the stromal bed. Central flap thickness was then calculated.

For surface curvature analysis, we used a commercial videokeratoscope (EyeSys Laboratories, Inc, Houston, Tex). The Placido disc was placed in a vertical position and the chamber centered according to the monitor control. This setting was adopted from a previous study to obtain reproducible measurements.19 Care was taken to preserve the orientation in preoperative and postoperative recordings. Three measurements were performed preoperatively and postoperatively for each cornea.

To assess graft stability, intrachamber pressure was raised progressively by changing stepwise the height of the bottle, as previously reported.19 Under visual control with the surgical microscope at ×12 magnification, presence of leakage was monitored and pressure recorded by digital manometry as described earlier in the article.

STATISTICAL ANALYSIS

Calculations were made using StatsDirect, version 1.9.0, for Windows (CamCode, Ashwell, England). Mean, standard deviation, minimum, and maximum values were described. Comparisons between groups were performed using the nonparametric Mann-Whitney U test for unpaired samples and the Wilcoxon signed rank test for paired samples. A Spearman rank correlation test was performed to assess the dependence of resisted pressure on donor size. A P value of .05 was considered statistically significant.

The surgical procedure was simple and similar to a combination of a corneal flap technique and penetrating keratoplasty. The mean (SD) flap thickness was 317.25 (51.65) μm in group 1 and 263.25 (67.73) μm in group 2 (P = .25).

There was a significant difference regarding the preoperative and postoperative change in average keratometry values between both groups. The mean (SD) change in average keratometry value for group 1 was 3.08 (0.84) diopters (D), whereas for group 2 that change was 1.13 (0.55) D (P = .008) (Table 2) (Figure 3).

Table Graphic Jump LocationTable 2. Keratometric Analysis of Corneoscleral Rims in the Artificial Anterior Chamber
Place holder to copy figure label and caption
Figure 3.

Preoperative (A) and postoperative (B) corneal topography. The representative cornea underwent a sutureless procedure using tissue adhesive for repositioning of the flap. The postoperative map shows regular astigmatism.

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In terms of stability of the graft, we observed great variability in both groups. A higher resistance was observed in group 1. The mean (SD) calculated resisted pressure was 95.67 (27.37) mm Hg (range, 56.2-119.5 mm Hg). Group 2 had a lower leaking pressure of 82.45 (18.40) mm Hg (range, 57.9-102.1 mm Hg). However, this difference was not statistically significant (P = .97).

Penetrating keratoplasty has been the only treatment of visual impairment resulting from corneal endothelial cell decompensation for many years. Recovery of vision can be delayed by corneal distortion resulting from the presence of sutures because of the degree of tension necessary to obtain a watertight wound.

Barraquer1 first reported the transplantation of posterior corneal tissue underneath an anterior lamellar flap. Melles et al1113,22 and Van Dooren et al23 reported a technique of PLK through a limbal incision creating a stromal pocket. Terry and Ousley24,25 have described a similar technique, also using a limbal incision and deep stromal dissection. Lamellar corneal surgery has become more popular recently with the use of microkeratome instrumentation, achieving a remarkable cut quality with the latest systems.26 The smoothness of the cut surface may lead to a better surgical outcome with a clearer interface, which is essential to obtaining a good optical result.27 Posterior lamellar keratoplasty is emerging as an alternative to penetrating keratoplasty in patients with endothelial cell dysfunction.

We previously reported on 2 different techniques of PLK using an artificial anterior chamber and microkeratome.19,20 In the first report, we used 8 interrupted sutures (10-0 nylon) in the stromal bed to secure the graft.19 In our second study, we used a running graft suture to secure the graft.20 However, we have observed that the transplanted corneal disc tends to remain attached to the flap stroma, without sutures, when the pressure is within physiologic limits. Now we believe that the stromal surface tension at the donor-recipient interface, together with a physiologic intraocular pressure, contributes to keep the disc in the right place. With the additional pump of endothelial cells, these adherent forces may be stronger.

Compared with penetrating keratoplasty, PLK may have several advantages, including less surgical time, less risk of intraoperative complications, less risk of high astigmatism, faster visual recovery, less frequent follow-up visits for selective suture removal, decreased risk of suture-induced neovascularization toward the graft, and less risk of wound dehiscence. Donor tissue may be used more efficiently, as with the use of corneas that might otherwise be discarded after photorefractive keratectomy.

The resultant astigmatism after penetrating keratoplasty is variable. With standard trephination methods, the mean astigmatism fluctuates between 3 and 6 D.28 With excimer laser trephination, the mean keratometric astigmatism fluctuates between 3 and 3.5 D.29 In endokeratoplasty, the mean refractive astigmatism in the small series reported was 2.9 D,18 whereas in our reported series using interrupted sutures for securing graft, the mean astigmatism was 3.3 D.19 In our last report, using a running graft suture and a sutureless hinged flap, the mean astigmatism was 1.47 D.20

The use of tissue adhesive in this study produced less astigmatism than other reports of microkeratome-assisted PLK. Furthermore, the absence of sutures made the technique simpler and considerably less time-consuming. However, one of the major concerns of this technique is the stability of the graft because of the reduced support of the sutureless disc in the posterior stroma and the wide anterior opening with the flap. It is possible that in time, there could be slippage of the glued interface, which could lead to induced astigmatism. Although videokeratographic data showed a smaller degree of astigmatic change, further studies are needed to verify this in a clinical setting.

With the particular modifications added in this study, more stability is provided to the flap with a large hinge of almost 2 quadrants of extension. The anterior opening is therefore reduced and easily sealed with sutures or corneal adhesive. Hence, sutureless microkeratome-assisted PLK with the use of tissue glue may become a new alternative in the surgical treatment of corneal endothelial disorders. Further clinical experience is required before the widespread use of this approach in patients.

Correspondence: Ashley Behrens, MD, Wilmer Ophthalmological Institute, Johns Hopkins Hospital, 600 N Wolfe St, Jefferson Building, Room 3-127, Baltimore, MD 21287-9278 (abehrens@jhmi.edu).

Submitted for Publication: December 7, 2004; final revision received April 14, 2005; accepted April 22, 2005.

Financial Disclosure: None.

Funding/Support: This study was supported by the Walter J. Stark Research Award; grant R21EB002369 from the National Institutes of Health, Bethesda, Md (J.H.E.); and Research to Prevent Blindness, New York, NY.

Acknowledgment: We thank the Central Florida Lions Eye and Tissue Bank, Tampa, for providing the corneas necessary to perform this study.

Barraquer  JI Lamellar keratoplasty (special techniques). Ann Ophthalmol 1972;4437- 469
PubMed
Aiken-O’Neill  PMannis  MJ Summary of corneal transplant activity: Eye Bank Association of America. Cornea 2002;211- 3
PubMed Link to Article
Seitz  BMuller  EELangenbucher  AKus  MMNaumann  GOH Endothelial keratopathy in pseudoexfoliation syndrome: quantitative and qualitative morphometry using automated video image analysis [in German]. Klin Monatsbl Augenheilkd 1995;207167- 175
PubMed Link to Article
von Hippel  A Über die operative Behandlung totaler stationärer Hornhauttrübungen. Albrecht Von Graefes Arch Klin Exp Ophthalmol 1877;2379- 100
Link to Article
von Hippel  A Eine neue Methode der Hornhaut Transplantation. Albrecht Von Graefes Arch Klin Exp Ophthalmol 1885;34108- 130
Link to Article
Naumann  GOH Corneal transplantation in anterior segment diseases. Eye 1995;9395- 421
PubMed Link to Article
De Molfetta  VBrambilla  MDe Casa  NArpa  PRiva  M Residual corneal astigmatism after perforating keratoplasty. Ophthalmologica 1979;179316- 321
PubMed Link to Article
Price  NCSteele  AD The correction of post-keratoplasty astigmatism. Eye 1987;1562- 566
PubMed Link to Article
Gospodarowicz  DGreenburg  GAlvarado  J Transplantation of cultured bovine corneal endothelial cells to rabbit cornea: clinical implications for human studies. Proc Natl Acad Sci U S A 1979;76464- 468
PubMed Link to Article
Jumblatt  MMMaurice  DMMcCulley  JP Transplantation of tissue-cultured corneal endothelium. Invest Ophthalmol Vis Sci 1978;171135- 1141
PubMed
Melles  GREggink  FALander  F  et al.  A surgical technique for posterior lamellar keratoplasty. Cornea 1998;17618- 626
PubMed Link to Article
Melles  GRLander  FBeekhuis  WHRemeijer  LBinder  PS Posterior lamellar keratoplasty for a case of pseudophakic bullous keratopathy. Am J Ophthalmol 1999;127340- 341
PubMed Link to Article
Melles  GRLander  Fvan Dooren  BTPels  EBeekhuis  WH Preliminary clinical results of posterior lamellar keratoplasty through a sclerocorneal pocket incision. Ophthalmology 2000;1071850- 1856
PubMed Link to Article
Terry  MA The evolution of lamellar grafting techniques over 25 years. Cornea 2000;19611- 616
PubMed Link to Article
Pallikaris  IGPapatzanaki  MESiganos  DSTsilimbaris  MKPallikaris  I A corneal flap technique for laser in situ keratomileusis: human studies. Arch Ophthalmol 1991;1091699- 1702
PubMed Link to Article
Azar  DTJain  SSambursky  RStrauss  L Microkeratome-assisted posterior keratoplasty. J Cataract Refract Surg 2001;27353- 356
PubMed Link to Article
Ehlers  NEhlers  HHjortdal  JMoller-Pedersen  T Grafting of the posterior cornea: description of a new technique with 12-month clinical results. Acta Ophthalmol Scand 2000;78543- 546
PubMed Link to Article
Busin  MArffa  RCSebastiani  A Endokeratoplasty as an alternative to penetrating keratoplasty for the surgical treatment of diseased endothelium: initial results. Ophthalmology 2000;1072077- 2082
PubMed Link to Article
Behrens  AEllis  KLi  LSweet  PMChuck  RS Endothelial lamellar keratoplasty using an artificial anterior chamber and a microkeratome. Arch Ophthalmol 2003;121503- 508
PubMed Link to Article
Li  LEllis  KRBehrens  A  et al.  Laboratory model for microkeratome-assisted posterior lamellar keratoplasty utilizing a running graft suture and a sutureless hinged flap. Cornea 2002;21192- 195
PubMed Link to Article
Reyes  JMHerretes  SPirouzmanesh  A  et al.  A modified chondroitin sulfate aldehyde adhesive for sealing corneal incisions. Invest Ophthalmol Vis Sci 2005;461247- 1250
PubMed Link to Article
Melles  GRJLander  FRietveld  FJR Transplantation of Descemet's membrane carrying viable endothelium through a small scleral incision. Cornea 2002;21415- 418
PubMed Link to Article
Van Dooren  BMulder  PGHNieuwendaai  CPBeekhuis  WHMelles  GRJ Endothelial cell density after posterior lamellar keratoplasty (Melles techniques): 3 years follow-up. Am J Ophthalmol 2004;138211- 217
PubMed Link to Article
Terry  MAOusley  PJ Endothelial replacement without surface corneal incisions or sutures. Cornea 2001;2014- 18
PubMed Link to Article
Terry  MAOusley  PJ Replacing the endothelium without corneal surface incisions or sutures: the first United States clinical series using the deep lamellar endothelial keratoplasty procedure. Ophthalmology 2003;110755- 764
PubMed Link to Article
Behrens  ALangenbucher  AKus  MMRummelt  CSeitz  B Experimental evaluation of two current-generation automated microkeratomes: the Hansatome and the Supratome. Am J Ophthalmol 2000;12959- 67
PubMed Link to Article
Haimovici  RCulbertson  WW Optical lamellar keratoplasty using the Barraquer microkeratome. Refract Corneal Surg 1991;742- 45
PubMed
Perlman  EM An analysis and interpretation of refractive errors after penetrating keratoplasty. Ophthalmology 1981;8839- 45
PubMed Link to Article
Seitz  BLangenbucher  AKus  MMKuchle  MNaumann  GO Nonmechanical corneal trephination with the excimer laser improves outcome after penetrating keratoplasty. Ophthalmology 1999;1061156- 1164
PubMed Link to Article

Figures

Place holder to copy figure label and caption
Figure 1.

Surgical steps. A, After flap creation. Note the large flap hinge (arrows) in a partial flap pass. B, Dissection of the area under the hinge (arrows and line) with spatula in a shape that accommodates the trephine blade. C, Stromal bed after trephination of the posterior stroma and endothelium with flap reflected and trephination opening (arrows). D, Sutureless donor disc in place, flap repositioned, and glue (blue color) at the wound edges. The superficial wound is limited by the hinge (arrows). The corneal disc is in place without sutures (arrowheads).

Graphic Jump Location
Place holder to copy figure label and caption
Figure 2.

Postoperative view, suture group. The flap keratectomy is held in place by 5 interrupted 10-0 nylon sutures. The disc with posterior stroma and endothelium is secured underneath the flap without sutures.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 3.

Preoperative (A) and postoperative (B) corneal topography. The representative cornea underwent a sutureless procedure using tissue adhesive for repositioning of the flap. The postoperative map shows regular astigmatism.

Graphic Jump Location

Tables

Table Graphic Jump LocationTable 1. Data Collected From Corneas
Table Graphic Jump LocationTable 2. Keratometric Analysis of Corneoscleral Rims in the Artificial Anterior Chamber

References

Barraquer  JI Lamellar keratoplasty (special techniques). Ann Ophthalmol 1972;4437- 469
PubMed
Aiken-O’Neill  PMannis  MJ Summary of corneal transplant activity: Eye Bank Association of America. Cornea 2002;211- 3
PubMed Link to Article
Seitz  BMuller  EELangenbucher  AKus  MMNaumann  GOH Endothelial keratopathy in pseudoexfoliation syndrome: quantitative and qualitative morphometry using automated video image analysis [in German]. Klin Monatsbl Augenheilkd 1995;207167- 175
PubMed Link to Article
von Hippel  A Über die operative Behandlung totaler stationärer Hornhauttrübungen. Albrecht Von Graefes Arch Klin Exp Ophthalmol 1877;2379- 100
Link to Article
von Hippel  A Eine neue Methode der Hornhaut Transplantation. Albrecht Von Graefes Arch Klin Exp Ophthalmol 1885;34108- 130
Link to Article
Naumann  GOH Corneal transplantation in anterior segment diseases. Eye 1995;9395- 421
PubMed Link to Article
De Molfetta  VBrambilla  MDe Casa  NArpa  PRiva  M Residual corneal astigmatism after perforating keratoplasty. Ophthalmologica 1979;179316- 321
PubMed Link to Article
Price  NCSteele  AD The correction of post-keratoplasty astigmatism. Eye 1987;1562- 566
PubMed Link to Article
Gospodarowicz  DGreenburg  GAlvarado  J Transplantation of cultured bovine corneal endothelial cells to rabbit cornea: clinical implications for human studies. Proc Natl Acad Sci U S A 1979;76464- 468
PubMed Link to Article
Jumblatt  MMMaurice  DMMcCulley  JP Transplantation of tissue-cultured corneal endothelium. Invest Ophthalmol Vis Sci 1978;171135- 1141
PubMed
Melles  GREggink  FALander  F  et al.  A surgical technique for posterior lamellar keratoplasty. Cornea 1998;17618- 626
PubMed Link to Article
Melles  GRLander  FBeekhuis  WHRemeijer  LBinder  PS Posterior lamellar keratoplasty for a case of pseudophakic bullous keratopathy. Am J Ophthalmol 1999;127340- 341
PubMed Link to Article
Melles  GRLander  Fvan Dooren  BTPels  EBeekhuis  WH Preliminary clinical results of posterior lamellar keratoplasty through a sclerocorneal pocket incision. Ophthalmology 2000;1071850- 1856
PubMed Link to Article
Terry  MA The evolution of lamellar grafting techniques over 25 years. Cornea 2000;19611- 616
PubMed Link to Article
Pallikaris  IGPapatzanaki  MESiganos  DSTsilimbaris  MKPallikaris  I A corneal flap technique for laser in situ keratomileusis: human studies. Arch Ophthalmol 1991;1091699- 1702
PubMed Link to Article
Azar  DTJain  SSambursky  RStrauss  L Microkeratome-assisted posterior keratoplasty. J Cataract Refract Surg 2001;27353- 356
PubMed Link to Article
Ehlers  NEhlers  HHjortdal  JMoller-Pedersen  T Grafting of the posterior cornea: description of a new technique with 12-month clinical results. Acta Ophthalmol Scand 2000;78543- 546
PubMed Link to Article
Busin  MArffa  RCSebastiani  A Endokeratoplasty as an alternative to penetrating keratoplasty for the surgical treatment of diseased endothelium: initial results. Ophthalmology 2000;1072077- 2082
PubMed Link to Article
Behrens  AEllis  KLi  LSweet  PMChuck  RS Endothelial lamellar keratoplasty using an artificial anterior chamber and a microkeratome. Arch Ophthalmol 2003;121503- 508
PubMed Link to Article
Li  LEllis  KRBehrens  A  et al.  Laboratory model for microkeratome-assisted posterior lamellar keratoplasty utilizing a running graft suture and a sutureless hinged flap. Cornea 2002;21192- 195
PubMed Link to Article
Reyes  JMHerretes  SPirouzmanesh  A  et al.  A modified chondroitin sulfate aldehyde adhesive for sealing corneal incisions. Invest Ophthalmol Vis Sci 2005;461247- 1250
PubMed Link to Article
Melles  GRJLander  FRietveld  FJR Transplantation of Descemet's membrane carrying viable endothelium through a small scleral incision. Cornea 2002;21415- 418
PubMed Link to Article
Van Dooren  BMulder  PGHNieuwendaai  CPBeekhuis  WHMelles  GRJ Endothelial cell density after posterior lamellar keratoplasty (Melles techniques): 3 years follow-up. Am J Ophthalmol 2004;138211- 217
PubMed Link to Article
Terry  MAOusley  PJ Endothelial replacement without surface corneal incisions or sutures. Cornea 2001;2014- 18
PubMed Link to Article
Terry  MAOusley  PJ Replacing the endothelium without corneal surface incisions or sutures: the first United States clinical series using the deep lamellar endothelial keratoplasty procedure. Ophthalmology 2003;110755- 764
PubMed Link to Article
Behrens  ALangenbucher  AKus  MMRummelt  CSeitz  B Experimental evaluation of two current-generation automated microkeratomes: the Hansatome and the Supratome. Am J Ophthalmol 2000;12959- 67
PubMed Link to Article
Haimovici  RCulbertson  WW Optical lamellar keratoplasty using the Barraquer microkeratome. Refract Corneal Surg 1991;742- 45
PubMed
Perlman  EM An analysis and interpretation of refractive errors after penetrating keratoplasty. Ophthalmology 1981;8839- 45
PubMed Link to Article
Seitz  BLangenbucher  AKus  MMKuchle  MNaumann  GO Nonmechanical corneal trephination with the excimer laser improves outcome after penetrating keratoplasty. Ophthalmology 1999;1061156- 1164
PubMed Link to Article

Correspondence

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The American Medical Association is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The AMA designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 CreditTM per course. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Physicians who complete the CME course and score at least 80% correct on the quiz are eligible for AMA PRA Category 1 CreditTM.
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For CME Course: A Proposed Model for Initial Assessment and Management of Acute Heart Failure Syndromes
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