Ординатура / Офтальмология / Английские материалы / Corneal Endothelial Transplant (DSAEK, DMEK & DLEK)_John_2010

Outline

•Definition

•Classification of LKP

•Indications for LKP

•Differences between ALK and PLK

•Wound architecture in LKP

•General comments.

Definition

Lamellar Keratoplasty

LKP consists of partial thickness corneal tissue replacement.

Anterior Lamellar Keratoplasty (ALK)

ALK is defined as varying amounts of anterior corneal tissue replacement with retention of the recipient Descemet’s membrane and endothelium. ALK violates the Bowman’s layer (Table 13-1).

ALK in general would include superficial-ALK (SALK), mid-ALK (MALK), deep-ALK (DALK), and total-ALK (TALK) (Table 13-2). All of these procedures relate to the thickness of the excised recipient cornea. A matching donor corneal thickness with a matching donor corneal layers

TABLE 13-1: Differences between anterior lamellar keratoplasty (ALK), posterior lamellar keratoplasty (PLK), and penetrating keratoplasty (PKP)

that are similar to the excised recipient corneal disk is used to complete the surgery.

Posterior Lamellar Keratoplasty (PLK)

PLK is defined as any corneal lamellar procedure where the Descemet’s membrane and/or endothelium are excised with or without host corneal stroma. PLK usually violates the Descemet’s membrane (Table 13-3). PLK includes the following:

•Deep lamellar endothelial keratoplasty (DLEK)

•Flap-associated DLEK (FDLEK)

•Descemet Stripping Automated Endothelial Keratoplasty (DSAEK)6,34

DSAEK [See Section 9, Descemet’s Stripping Automated Endothelial Keratoplqasty (DSAEK)] involves removal of the recipient Descemet’s membrane and endothelium and transplantation of a donor corneal disk that is about 150 µm thick and having a diameter of about 8.0 mm or 9.0 mm and rarely, 7.0 mm. This donor corneal disk comprises of deep donor corneal stroma with attached donor DM and endothelium.6,34

•Descemet membrane endothelial keratoplasty (DMEK)

•Descemet membrane automated endothelial keratoplasty (DMAEK)

•Endothelial cell transplant (ECT) (currently not possible)

•Endothelial cell activation (ECA)(currently not possible)

Penetrating Keratoplasty (PKP)

PKP is full-thickness corneal replacement procedure. PKP violates both the Bowman’s and Descemet’s membrane

(Table 13-1).

Wedefinethedifferencebetweenanteriorandposterior LKPasthepresenceorabsenceofrecipientBowman’slayer. In ALK, Bowman’s layer is always violated and absent, while in PLK, Bowman’s layer is present (Table 13.1).

Classification of LKP

General Classification

Based on Type

1.Optical

2.Tectonic

3.Therapeutic

4.Cosmetic.

Based on Location

1. Central

2.Peripheral—Circular, oval, crescentic, annular, semilunar, rectangular or strip graft

3.Total—central and peripheral

4.Corneoscleral

a.Total corneoscleral LKP

b.Partial corneoscleral LKP—Circular, crescentic, annular, or strip graft.

Central are usually round, but peripheral can adopt different configurations (see above)

Based on Stem-cell Transplantation

1.Non-stem cell LKP

2.LKP with stem cell transplantation (SCT)

Based on Number of Procedures

1.LKP only

2.LKP combined with PKP

Based on Age

1.Pediatric LKP

2.Adult LKP

Based on the Use of Microkeratome

1.Manual LKP—Here no microkeratome is utilized for the procedure.

2.Automated LKP—Here a microkeratome is used for the dissection.

Based on Surgical Approach

1.Direct

a.Cornea

2.Indirect

a.Scleral-pocket.

Based on Diameter (donor and recipient)

1.Total ( up to 11-12 mm.)

2.Subtotal (9-10 mm.)

3.Partial (less than 9 mm)

4.Corneoscleral.

Based on the Depth of the Recipient Corneal Resection

(Figure 13-1)

1.Superficial ALK (SALK): <160 µm central cornea.

2.Mid ALK (MALK): Between 160-400 µm central cornea.

3.Deep ALK (DALK): Up to pre-Descemetic level, 400490 µm central cornea, 585-620 µm peripheral cornea.

4.Total ALK (TALK): Up to Descemetic level (almost 100%), >490 µm (490-520) central cornea, 630-650 µm peripheral cornea.

Based on Donor Corneal Thickness

1.Anterior lamellar dissection (ALD) upto 160 µm.

2.Mid-stromal dissection (MSD) 160-400 µm.

3.Full-thickness donor graft with endothelium (FTDGE).

4.Full-thickness donor graft without endothelium (FTDG).

Based on Substitution or Addition of Donor Tissue

1.Substitution LKP—all ALKP procedures (see above), DLEK, and FDLEK.

2.Neutral LKP (Normal thickness)—DMEK/DECT (Synonymous).

3.Addition LKP —DSAEK/DSEK/DXEK (Synonymous).

Substitution LKP: In substitution-LKPs, the final recipient corneal thickness after surgery is in most cases, is expected to be closer to normal corneal thickness or slightly greater than normal.

Neutral LKP: Restores normal corneal thickness.

Addition LKP: Inaddition-LKP(DSAEK),thefinalrecipient cornealthicknessaftersurgerywill“always”begreaterthan thepreoperative,non-edematous,recipientcornealthickness (recipient cornea minus Descemet’s membrane and endothelium)plusthethicknessofthedonordisk(i.e.deep, donor stroma along with donor DM and endothelium).

1.Optical LKP: Lamellar keratoplasty that is performed for improving the eyesight is called optical LKP.

2.Tectonic LKP: Lamellar keratoplasty that is performed to restore structural integrity of the cornea is named as tectonic LKP. No emphasis is made here for optical outcome. Tissue addition is made in areas of corneal thinning and restoration to near normal surface contour of the cornea is carried out.

3.Therapeutic LKP: Lamellar keratoplasty that is performed to remove infected corneal tissue that has failed medical treatment. Medically failed corneal infections are usually treated with a therapeutic PKP. Therapeutic LKP may also be performed for treating Descemetocele with or without corneal perforation. Rarely, LKP is performed to remove corneal tumor that has not invaded the full-thickness of the cornea. Therapeutic LKP may also be utilized in corneal inflammatory processes, and in selected cases of fungal keratitis. Therapeutic LKP is not performed as a routine surgical procedure for fungal keratitis.

4.Cosmetic LKP: Lamellar keratoplasty that is performed to improve the cosmetic appearance of a blind or nearly blind eye.

John-Malbran ALK Classification of Optical

LKP (Figure 13-1)

I.Anterior Lamellar Keratoplasty (ALK)

1.Superficial ALK (SALK) (30%) (<160 µm) (Figure

13-1).

2.Mid ALK (MALK) (30-70%) (160-400 µm) (Figure

13-1).

3.Deep ALK (DALK) (90-95%) (400-490 µm) (Figure

13-1).

4.Total ALK (TALK) (almost 100% stromal, excludes Descemet’s membrane and endothelium) >490 µm (500-520 µm) (Figure 13-1).

John PLK Classification of Optical LKP (Figure 13-2)

Posterior Lamellar Keratoplasty (PLK) (Figure 13-2).

1A. Deep lamellar endothelial keratoplasty (DLEK) (Figure

13-2)

Without flap – no surface wound or sutures. 1B. Flap-associated DLEK (FDLEK) (Figure 13-2)

With flap – surface wound and sutures present.

2.Descemet Stripping Automated Endothelial Keratoplasty (DSAEK)/ Synonymous termDescemetorhexis with endokeratoplasty (DXEK) (Figure 13-2).

3.Descemet’s membrane endothelial cell transplantation (DECT)/Descemet membrane endothelial keratoplasty (DMEK) (Figure 13-2).

4.Endothelial cell transplantation (ECT) (Figure 13-2).

5.Endothelial cell activation (ECA) (Figure 13-2).

FDLEK—Previous terminologies included endokeratoplasty, and endothelial replacement flap approach.

ECT and ECA have not been established as a surgical procedure at the present time (at the time of writing this chapter).

Indications for LKP

A.Optical

1.Scars

a.Traumatic

b.Herpetic (Herpes simplex & zoster)

c.Surgical

d.Chemical injury with healthy endothelium

2.Dystrophies

a.Map-dot-fingerprint dystrophy with recurrent erosion and scars

b.Epithelial, Bowman’s membrane, and stromal dystrophies

3.Degenerations

a.Salzman’s nodular degeneration

4.Ectasia

a.Keratoconus

b.Keratoglobus

c.Pellucid Marginal Degeneration

5.Refractive complications

a.LASIK flap folds not responding to conventional treatment including mechanical, thermal, and hydration techniques

b.Post-LASIK ectasia (iatrogenic ectasia)

c.PRK complication with persistent haze

B.Tectonic

1.Descemetocele

2.Pellucid marginal degeneration with Descemetocele

3.Terrienn’s marginal degeneration with Descemetocele

4.Sterile corneal melt and ulceration including Mooren’s ulcer.

C.Therapeutic

1.Infective (usually PKP)

2.Tumors

3.Inflammatory

D.Cosmetic

1.Opaque, cloudy cornea with healthy endothelium in a blind or near blind eye.

Differences between ALK and PLK

There are several differences between anterior and posterior lamellar keratoplasty and these differences are listed in Tables 13-1 to 13-3. The interface in lamellar keratoplasty is important for the quality of visual outcome following such surgical procedures. In SALK, MALK, and DALK the host-donor corneal interface is stroma-to-stroma, and the location of the interface varies from superficial, mid to deep corneal stroma, while in TALK this interface is host Descemet’s membrane to the deep stroma of the donor cornea. Additionally, the interface in TALK is expected to be smoother since the DM is smooth as compared to the stroma-to-stroma interface described above. With an interface that is so deep in the cornea next to the Descemet’s membrane in TALK as compared to SALK, MALK, and DALK, the quality of vision may be expected to be better in TALK. However, recent refinements in DALK,35 can afford excellent visual results comparable to TALK with the advantage of reduced risk of Descemet’s membrane perforation, which in TALK without the use of dye [indocyanine green (ICG), trypan blue (Vision Blue)], has been reported to be between 8% - 36%.

In 1972, Josè Barraquer outlined the favorable conditions to obtain better visual results with LKP including deepest possible interface to reduce corneal scarring.36

In general, PLK procedures are technically more difficult than ALK. Among ALK procedures TALK is the most difficult procedure to perform. The surgeon attempting these surgical procedures must have adequate experience in lamellar corneal surgery.

Wound Architecture in LKP

Automated microkeratome-assisted ALK usually have a tapered lamellar disk margin with good adherence of the lamellar disk to the host corneal bed, especially in SALK. In contrast, the nearly perpendicular wound margins created by manual ALK procedures require corneal sutures to maintain the donor graft in secure position on the host

corneal bed. Use of biologic tissue adhesive is better suited for SALK with the use of a microkeratome. When fibrin glue (Tisseel, Baxter Inc., Deerfield, IL) is used for deeper lamellar keratoplasty procedures, it needs to be supplemented with sutures.

General Comments

Automated microkeratome-assisted LKP usually should not be utilized in corneal disorders with considerable variations in corneal thickness, very deep stromal opacities and in conditions where there are extensive corneal and ocular surface irregularities. This limits the use of automated LKP procedures in pathologic corneas.

The unified classification, namely, John-Malbran ALK classification for optical LKP, and the John PLK classification for optical LKP described in this chapter is expected to simplify and standardize the terminologies used in lamellar keratoplasty procedures worldwide.

References

1. John T. Descemetorhexis with endokeratoplasty. In: Surgical Techniques in Anterior and Posterior Lamellar Corneal Surgery. John T (Ed.). Jaypee Brothers Medical Publishers (P) Ltd., New Delhi, India, 2006;411-20.

2. John T (Editorial). Selective tissue corneal transplantation: a great step forward in global visual restoration. Expert Rev Ophthalmol 2006;1:5-7.

3. John T. Descemetorhexis with endokeratoplasty (DXEK). In: John T (Ed.). Step by Step Anterior and Posterior Lamellar Keratoplasty. Jaypee Brothers Medical Publishers (P) Ltd., New Delhi, India, 2006;177-96.

4. John T. Surgical management of diffuse corneal opacities (Fullthickness Grafting, Deep Lamellar Keratectomy). In: Becker MD, Davis J (Eds): Surgical Management of Inflammatory Eye Disease, Springer Publisher, ch II.A.1.2 (In Press).

5. Sinha R, Vajpayee RB, Sharma N, Tityal JS, Tandon R. Trypan blue assisted descemetorhexis for inadvertently retained Descemet’s membrane after penetrating keratoplasty. Br J Ophthalmol 2003;87:654-5.

6. Melles GR, Wijdh RH, Nieuwendaal CP. A technique to excise the descemet membrane from a recipient cornea (descemetorhexis). Cornea 2004; 23:286-8.

7. Zvi T, Nadav B, Itamar K, Tova L: Inadvertent descemetorhexis. J Cataract Refract Surg 2005; 31:234-5.

8. Busin M, Arffa RC, Sebastiani A. Endokeratoplasty as an alternative to penetrating keratoplasty for the surgical treatment of diseased endothelium: initial results. Ophthalmology 2000; 107:2077-82.

9. Vasco Posada J. Homoqueratoplastia interlaminar. Ann Inst Barraquer 1973;11:335.

10.Hamilton W, Wood TO. Inlay lamellar keratoplasty. In: Kaufman HE, McDonald MB, Barron BA, Waltman SR(Eds.): The Cornea, New York, Churchill Livingstone, 1988;683-95.

11.Panda A, Bageshwar LM, Ray M, et al. Deep lamellar

keratoplasty versus penetrating keratoplasty for corneal lesions. Cornea 1999;18:172-5.

12.Wood TO. Lamellar transplants in keratoconus. Am J Ophthalmol 1977;83:543-5.

13.Olson RJ. Corneal transplantation techniques. In Kaufman HE, McDonald MB, Barron BA, Waltman SR (Eds): The Cornea, New York, Churchill Livingstone, 1988;743-85.

14.Rich LF. Expanding the scope of lamellar keratoplasty. Tr Am Ophth Soc 1999; vol XCVII: 771-814.

15.Terry MA. The evolution of lamellar grafting techniques over twenty-five years. Cornea 2000;19:611-6.

16.Melles GRJ, Lander F, Rietveld FJ, et al. A new surgical technique for deep stromal, anterior lamellar keratoplasty. Br J Ophthalmol 1999;83:327-33.

17.Shimazaki J, Shimmura S, Ishioka M, Tsubota K. Randomized clinical trial of deep lamellar keratoplasty vs penetrating keratoplasty. Am J Ophthalmol 2002; 134:159-65.

18.Sugita J, Kondo J. Deep lamellar keratoplasty with complete removal of pathological stroma for vision improvement. Br J Ophthalmol 1997; 81:184-8.

19.Melles GR, Remeijer L, Geerards AJ, Beekhuis WH. A quick surgical technique for deep, anterior lamellar keratoplasty using visco-dissection. Cornea 2000; 19:427-32.

20.Seitz B, Langenbucher A, Hofmann-Rummelt C, et al. Nonmechanical posterior lamellar keratoplasty using the femtosecond laser (femto-plak) for corneal endothelial decompensation. Am J Ophthalmol 2003; 136:769-72.

21.Hallerman W. Verschiedenes uber keratoplastik. Klin Monatsbl, Augenh 1959;135:252-9.

22.Hallerman W. Zur technik der lamellaren keratoplastik. Klin Monatsbl, Augenh 1963; 142:243-50.

23.Hallerman W. Technik und ergebnisse einer operative behandlung des keratoglobus. Klin Monatsbl, Augenh 1975; 166:593-8.

24.Stocker FW. In discussion of McCulloch C, Thompson GA, Basu PK. Lamellar grafts using full thickness donor material. Tr Am Ophthalmol Soc 1963;61:154-80.

25.Stocker FW. Management of corneal dystrophies. Latest concepts. Highlights of Ophthalmology 1965;8:221.

26.Malbran E, Stefani C. Lamellar keratoplasty in corneal ectasias. Ophthalmologica 1972;164:50-58.

27.Malbran E, Stefani C. Lamellar keratoplasty in corneal ectasias. Ophthalmologica 1972;164:59-70.

28.Anwar M. Technique in lamellar keratoplasty. Trans Ophthalmol Soc UK 1974;94:163-7.

29.McCulloch C, Thompson GA, Basu PK. Lamellar grafts using full thickness donor material. Tr Am Ophthalmol Soc 1963;61:154-80.

30.McPherson SD, Jr. In discussion of McCulloch C, Thompson GA, Basu PK. Lamellar grafts using full thickness donor material. Tr Am Ophthalmol Soc 1963;61:154-80.

31.Vasco Posada, J Homoqueratoplastia interlaminar. Rev Soc Col Oftal 1973;4:99.

32.Malbran E. Lamellar grafts may be reflourishing. Highligths of Ophthalmology 1989;27:5.

33.Malbran E. Lamellar keratoplasty and keratoconus. International Ophthalmological Clinics 1966;1:99-109.

34.Melles GR, Lander F, Rietveld FJ. Transplantation of Descemet’s membrane carrying viable endothelium through a small scleral incision. Cornea 2002;21:415-8.

35.Malbran ES, Malbran E Jr, Malbran J. The actual scope of lamellar grafts. Highlights of Ophthalmol 2004;32:2-6.

36.Barraquer J. Lamellar keratoplasty (special techniques). Ann Ophthalmol 1972;4:437-69.

Introduction

In this chapter, we shall “travel” on the “time-line” from the beginning of corneal transplantation surgery, through the turbulent times of development of techniques and instruments and complete our journey at the final stop, namely, the present time of modern day corneal transplantation. During this review, we shall try to recognize the major and minor contributors, in most, if not all aspects of corneal transplantation. Due to the long time periods, it is possible that we may unintentionally have overlooked some contributors. Also, it is possible that there exists yet unknown ophthalmologists who may have directly or indirectly contributed to further the field of corneal transplantation. We thank each and every ophthalmologist who has contributed to furthering our knowledge and improving the surgical techniques of corneal transplantation, so that our patients, all over the world can benefit from these improved surgical techniques and hopefully, improve their quality of vision.

The history of lamellar keratoplasty is fascinating and is over 100 years old. The fathers of lamellar keratoplasty include Königshofer, von Walther, Muehlbauer, and von Hippel. It started in 1840 when Walther and Muehlbauer described the surgical principles of the technique (Table 14-1).

The history of keratoplasty can be divided into four great periods as follows:

1.The period of the precursors and the first trials, before 1900.

2.The developmental period, between 1900 and 1945.

3.The period of constant improvement and changes, from 1945 until the middle of the nineties.

4.The current period, namely, the modern era.

lamellar keratoplasty (LKP). He was of the opinion that in many cases it was enough to perform partial removal of corneal tissue, leaving behind the intact deep layers of the cornea, including Descemet’s membrane and endothelium.3

In the same year, Muehlbauer, using von Walther’s idea, tried triangular lamellar grafts taken from the sheep and implanted it into human eyes, with poor results. The grafts corresponded to 2/3rds of the corneal thickness and corneal sutures were placed at the angles of the triangular graft. Although, this surgical trial was unsuccessful, Muehlbauer is credited as being one of the pioneers to use heterografts in humans. Additionally, he also described the surgical principles of LKP.3 During this early period, one of the most important event that occurred was in 1878, when Arthur von Hippel (1841–1916) invented the mechanical trephination of the cornea and described his technique for LKP. In 1888, using his mechanical trephine, Arthur von Hippel became the first surgeon to perform a successful keratoplasty in man (Figure 14-1). He achieved permanent improvement of visual acuity, after several years of experimental failures. This surgical procedure was a lamellar corneal graft.4 The mechanical trephine of von Hippel consisted of a circular cutting trephine with blades of different diameters, and a key for winding up the watch mechanism, which was a great evolutionary step at this time.

Despite this improvement, the technique of lamellar graft continued to be rather a laborious procedure for most eye surgeons and it became an intermediate step towards penetrating keratoplasty.

The Period of the Precursors and the First Trials, Before 1900

The beginning of the nineteenth century was a period of great medical developments that included the idea of grafts, namely, keratoplasty.1 A very important author from this period was Resinger, who, in 1924, performed the first animal graft.2

In 1839, Königshofer, according to Ramon Castroviejo,2 pioneered the idea of lamellar homologous and heterologous keratoplasties in animals. To outline the graft and the host tissue, he used a double knife in order to obtain the same shape and size for both donor and host.

The history of lamellar grafting began in 1840, when von Walther had a new concept of corneal surgery namely,

Figure 14-1: First corneal transplantation. LKPLamellar keratoplasty; PKP – Penetrating keratoplasty.