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

where the donor disc was dislocated on the first postoperative day.21, 23 All four cases were easily treated by taking the patient back to surgery, and usually under topical anesthesia, with a 15 minute operation, another air bubble is placed in the anterior chamber and the disc is repositioned. All repositioned grafts resulted in clear corneas, but the endothelial cell counts at 6 months postop are significantly lower than grafts that have not had to undergo repositioning.23 In our first 4 cases of DSEK without the benefit of scraping and roughening of the peripheral recipient bed, we experienced a 50% rate (2 of 4 eyes) of dislocation. Utilizing the modification of peripheral scraping, however, we have experienced only 4 cases (4%) of dislocation in our initial 100 DSEK cases using peripheral scraping.24 As of January 2007, we have experienced no cases of donor dislocation into the anterior chamber in the past consecutive 100 DSAEK cases, reducing our complication rate of dislocation to 2% or less (unpublished data).

If the graft is in good position on day one, it generally will heal in good position. Although we had no late dislocations in DLEK surgery, of the 4 cases of dislocation in DSEK/DSAEK surgery, 3 of those cases which were attached at day one following surgery, became dislocated on days 2, 3 and 4 after the surgery date. This has led us to recommend to patients that they lie in the supine position for one more day after DSEK (to utilize the residual air bubble in the anterior chamber) and to not rub their eye for 2 weeks after DSEK surgery. The edges of the graft seal down with solid healing some time within the first 3 months. The overlying cornea has a variable rate of clearing, but some patients are able to see as well as 20/20 only one week after DSAEK surgery with a crystal clear central cornea

(Figure 20-2).

Figure 20-2: One week following DSAEK surgery in a 43 year old phakic eye with Fuchs’ corneal dystrophy, the vision is 20/20 with a +0.50 spherical refraction.

Only prospective data with control of the variables of patient age and preoperative vision will sort out the differences in DLEK and DSEK/DSAEK surgical outcome. As a guide for DSAEK, however, we have found that the usual visual progression postoperatively of patients with minimal or no macular disease, is as follows:

One day: 20/200 One week: 20/70

One month: 20/20 to 20/40 Three months: 20/20 to 20/40 Six months: 20/20 to 20/40 One year: 20/20 to 20/30 Two years: 20/20 to 20/30

There is, of course, high variability of vision in any series of elderly patients undergoing ocular surgery, but especially, DLEK or DSEK/DSAEK surgery. The interface may clinically appear exceptionally clear following surgery. However, it is the stromal interface of the donor tissue that most likely contributes about one line of visual loss to the macular potential.13,14 Extensive work continues to be done to improve the interface in DSAEK surgery. Investigators are working in the areas of femtosecond laser preparation of the donor tissue, but currently, the interface after femtosecond resections in the deep stroma are inferior to that created by a microkeratome [See also Chapter 26, Femtosecond Laser (Intralase®) – Descemet’s Stripping Endothelial Keratoplasty (Femto-DSEK): Initial Studies of Surgical Technique in Human Eyes]. While all of these high and low technology approaches have individual appeal, the worth of any modification will have to be determined by comparing the safety level of the modified technique to the safety of the current DLEK and DSEK/DSAEK techniques. The ultimate visual results must also be compared in like fashion. If any of these modifications cause a higher dislocation rate or other complication for the grafted tissue, then any apparent advantage for the ease of surgery is “fatally” mitigated. Patient safety and improved patient results should always take precedence over the comfort level in surgery for the surgeon.

The endothelial survival after small incision DLEK/ DSEK/DSAEK surgery is quite remarkable. Even with folding the tissue and other donor manipulations described above, the average endothelial cell count after small incision DLEK surgery at 6 months is comparable to PKP surgery and is not significantly different from large incision DLEK where the tissue is not folded.14,21 However, our most recent 2 year analysis indicates that folded tissue has a more accelerated loss of endothelial cells from one to two years postoperatively than that found in eyes with large incision DLEK surgery where the tissue is inserted without folding it.

The postoperative medical therapy after DSAEK surgery is identical at this time to what is done with PKP surgery patients and in our DLEK surgery patients. Topical prednisolone acetate 1% is used four times a day for 3 months, then three times a day until 6 months, then twice a day until 9 months, and then once a day until one year postoperatively. The steroids are then tapered down further until discontinued entirely. In our first 100 cases of DLEK with follow-up between 6 months and 5 years, we have experienced only 4 episodes of graft rejection, inflammation, and only one case where the graft function was lost.24 This is a lower rate of rejection and graft loss due to rejection than that seen in a similar cohort of PKP patients. Steroid therapy after DLEK surgery, therefore, may not be as critical as after PKP surgery, but this remains speculative at this time. Fluoroquinolone antibiotics are used on a four times a day dosage for the first two weeks after DSAEK surgery and then discontinued.

Outside of a scientific protocol, DLEK/DSEK/DSAEK patients do not require the same degree of monitoring as standard PKP patients and therefore require less postoperative clinic time. With no sutures or corneal incisions to worry about, wound healing or ulcerations are not an issue. Astigmatism management is also not an issue after DLEK/DSEK/DSAEK surgery. The only critical monitoring that is required, is for steroid-induced glaucoma as long as the patient is on topical steroids, and this is done according to the clinician’s standard routine.

The DLEK/DSEK/DSAEK surgical procedure is different than PKP, and requires a commitment to exacting detail and thorough practice prior to incorporation of this procedure into the surgeon’s operative repertoire. However, with its superior topography, rapid wound healing and long term safety, the endothelial keratoplasty by DSAEK procedure is well worth the effort.

References

1. Sugar A, Sugar J. Techniques in penetrating keratoplasty: a quarter century of development. Cornea 2000;19:603-10.

2. Abou-Jaoude ES, Brooks M, Katz DG, Van Meter WS. Spontaneous wound dehiscence after removal of single continuous penetrating keratoplasty suture. Ophthalmology 2002;109:1291-6.

3. Tseng SH, Lin SC, Chen FK. Traumatic wound dehiscence after penetrating keratoplasty: Clinical features and outcome in 21 cases. Cornea 1999;18:553-8.

4. Stechschulte SU, Azar DT. Complications after penetrating keratoplasty. Int Ophthalmol Clin 2000;40:27-43.

5. Akova YA, Onat M, Koc F, Nurozler A, Duman S. Microbial keratitis following penetrating keratoplasty. Ophthalmic Surg Lasers 1999;449-55.

6. Confino J, Brown SI. Bacterial endophthalmitis associated with exposed monofilament sutures following corneal transplantation. Am J Ophthalmol 1985;99:111-3.

7. Ko WW, Frueh BE, Shields CK, Costello ML, Feldman ST. Experimental posterior lamellar transplantation of the rabbit cornea. Invest Ophthalmol Vis Sci 1993;34(4):1102.

8. Melles GR, Eggink FA, Lander F, Pels E, Rietveld FJ, Beekhuis WH, Binder PS. A surgical technique for posterior lamellar keratoplasty. Cornea 1998;17:618-26.

9. Terry MA, Ousley PJ. Endothelial replacement without surface corneal incisions or sutures: Topography of the deep lamellar endothelial keratoplasty procedure. Cornea 2001;20:14-8.

10.Terry MA, Ousley PJ. Deep lamellar endothelial keratoplasty in the first United States patients: Early clinical results. Cornea 2001;20:239-43.

11.Terry MA, Ousley 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;110:755-64.

12.Terry MA, Ousley PJ. In pursuit of emmetropia: Spherical equivalent refraction results with deep lamellar endothelial keratoplasty (DLEK). Cornea 2003;22:619-26.

13.Terry MA, Ousley PJ. Rapid visual rehabilitation after endothelial transplants with deep lamellar endothelial keratoplasty (DLEK). Cornea 2004;23:143-53.

14.Terry MA, Ousley PJ. Small incision deep lamellar endothelial keratoplasty (DLEK): 6 months results in the first prospective clinical study. Cornea 2005;24:59-65.

15.Terry MA. Endothelial replacement: The limbal pocket approach. Ophthalmol Clin North Am 2003;16:103-12.

16.Terry MA. Deep lamellar endothelial keratoplasty (DLEK): Pursuing the ideal goals of endothelial replacement. Eye 2003;17:982-8.

17.Terry MA. A new approach for endothelial transplantation: Deep lamellar endothelial keratoplasty. Int Ophthalmol Clin 2003;43:183-93.

18.Terry MA, Ousley PJ. Corneal endothelial transplantation: Advances in the surgical management of endothelial dysfunction. Contemporary Ophthalmology 2002;1(26):1-8.

19.Terry MA. “Endothelial Replacement. In: Krachmer J, Mannis M, Holland E (Eds). Cornea: Surgery of the Cornea and Conjunctiva. St. Louis: Elsevier Mosby; 2005;140:1707-18.

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

21.Terry MA, Ousley PJ. Deep lamellar endothelial keratoplasty (DLEK): Visual acuity, astigmatism, and endothelial survival in a large prospective series. Ophthalmology 2005;112:1541-9.

22.Amayem AF, Terry MA, Helal MH, Turki WA, El-Sabagh H, El-Gazayerli E, Ousley PJ. Deep Lamellar Endothelial Keratoplasty (DLEK): surgery in complex cases with severe preoperative visual loss. Cornea 2005;24:587-92.

23.Terry MA, Ousley PJ. Deep lamellar endothelial keratoplasty (DLEK): Early complications and their management. Cornea 2006;25:37-43.

24.Terry MA, Hoar KL, Wall J, Ousley PJ. The histology of dislocations in endothelial keratoplasty (DSEK and DLEK): Prevention of dislocation with a laboratory-based surgical solution in 100 consecutive DSEK cases. Cornea 2006;25:92632.

25.Terry MA, Wall JM, Hoar KL, Ousley PJ. A prospective study of endothelial cell loss during the 2 years after deep lamellar endothelial keratoplasty. Ophthalmology 2007;114:631-9.

Introduction

Descemet stripping automated endothelial keratoplasty (DSAEK) [synonymous with Descemetorhexis with endokeratoplasty (DXEK)], [See also Section 9, Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)], has been developed over the past decade and has recently established itself as the most successful alternative to conventional penetrating keratoplasty (PKP) for the surgical treatment of decompensated corneal endothelium. 1-5

DSAEK derives from the continuous improvement of the initial endokeratoplasty procedure, which we introduced in 1996.6 This technique included peeling of the recipient Descemet’s membrane, preparation of a donor lamella of deep stroma, Descemet’s membrane and endothelium, insertion of the graft into the anterior chamber through a clear-cornea tunnel, and fixation of the graft onto the bare posterior corneal surface by means of trans-corneal sutures (Figure 21-1). Results in the rabbit model (Figure 21-1) were not encouraging, as the postoperative course was complicated by frequent misplacement of the donor lenticule and high endothelial cell loss, thus making the use of this technique in humans unreasonable.

In 1999 Melles demonstrated that corneal stromal layers can adhere to each other permanently without the need for sutures and contributed substantially to the development of the new posterior lamellar keratoplasty techniques.7 However, Melles and other surgeons used hand dissection for the preparation of both the donor corneal tissue and for the recipient corneal bed, and the corneal surfaces obtained with this type of dissection create an interface with an optical quality that is very rarely compatible with 20/20 vision.

More recently, Price4,5 and others8 have substantially improved the optical quality of the DSAEK-interface by introducing the microkeratome-assisted dissection of the donor corneal tissue (See also Chapter 14, History of Lamellar and Penetrating Keratoplasty). Excellent visual results, comparable, if not superior to those of conventional PKP, have been reported by both authors. Nonetheless, the same complications encountered with the original endokeratoplasty procedure (graft displacement and, especially, endothelial cell loss up to 40-50% one year after surgery) still seem to complicate the postoperative course of DSAEK in a relatively high number of patients.

The modified surgical technique presented below was developed with the purpose of eliminating the major drawbacks of the present DSAEK technique, while retaining the major advantages of a relatively simple, reproducible and safe surgical procedure [See also Section 9, Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)].

Surgical Technique

A marker, usually 9.0 mm in diameter, is used at the beginning of the procedure to outline the limit of the internal surface, from which the endothelium will be peeled off during this surgery (Figure 21-2). The tip of a 25-gauge needle mounted on a 2.5 cc empty syringe is bent upwards (Figure 21-3) before it is introduced into the anterior chamber (AC) at the 12 o’clock position. About 0.2 to 0.4 cc of aqueous humor is aspirated and air is injected, filling-up the AC. The tip of the needle is then used to cut through endothelium and Descemet’s membrane following the contour of the superficial mark (Figure 21-4). Then the needle is retracted and a 25-gauge cannula is mounted on a syringe and

Figure 21-2: A circular mark, 9.0 mm in diameter is made on the corneal epithelium outlining the extent of Descemet’s membrane stripping.

Figure 21-3: A 25-gauge needle bent both proximally and at its tip, is used to perform Descemetorhexis.

re-inserted through the same entry site. The cannula is employed to sweep away the Descemet’s membrane and the endothelium, usually in a single piece (Figure 21-5). The blunt cannula avoids mechanical damage to the posterior bare stromal surface of the recipient cornea. Whenever air is lost through the entrance site of the needle/ cannula, the AC is reformed by injecting additional air with the syringe.

Performing the whole maneuver under air allows perfect visualization of the Descemet’s membrane and endo-

Figure 21-4: Descemetorhexis is performed under an air-bubble, using a 25 gauge needle.

Figure 21-5: A blunt 25-gauge cannula is used to remove in a single piece both the Descemet’s membrane and the endothelium under an air-bubble.

thelium without the need for any type of dye or much more importantly, for any viscoelastic substance in the AC (Figure 21-5). In fact, if viscoelastic substance is used in the AC and the viscoelastic substance is removed incompletely before insertion of the graft, it may reach the donor-recipient interface, preventing adhesion of the donor tissue to the stromal surface and causing the procedure to fail. A clearcornea tunnel, 1.0 mm in length and 5.0 mm in width is

Figure 21-6: Clear-cornea nasal tunnel is prepared with a keratome blade.

Figure 21-7: Microkeratome-assisted removal of the anterior stroma from the donor cornea mounted on the artificial anterior chamber (Moria S.A., Antony, France).

prepared nasally (Figure 21-6) [Editorial Note: For alternative techniques and instrumentation, See also Chapter 11, New/Useful Surgical Instruments in DSAEK, Chapter 32, Use of Dyes in DSAEK and DLEK, and Section 9, Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)]. The dimensions of the tunnel are critical for the uneventful insertion of the graft into the AC. If the tunnel is too long the donor tissue may remain partly trapped during insertion, while a too narrow tunnel may cause an increase in endothelial cell loss secondary to pronounced deformation of the donor corneal graft.

After coating the endothelial side of the donor cornea with viscoelastic substance, it is mounted on an artificial anterior chamber of the automated lamellar therapeutic

keratoplasty (ALTK) system (Moria S.A., Antony, France)

(See also Chapter 12, Artificial Anterior Chambers) and most of the anterior stroma is removed by means of the microkeratome with a 300 µm head, which usually cuts lamellae with a thickness of about 350 µm (Figure 21-7). The same marker that was used to mark the corneal surface is employed to mark the stromal side of the remaining tissue (usually with a thickness between 100 and 200 µm) (Figure 21-8A), which is then punched to the desired size (8.0 to 9.0 mm), as shown in Figure 21-8B. As opposed to what is being done by most corneal surgeons, the donor corneal tissue is not folded and inserted into the AC using the socalled “taco” technique. Instead, a specially designed glide is loaded with the donor corneal disk, endothelial side up

Figure 21-9: The donor tissue is pulled into the glide opening by means of a crocodile vitreous forceps.

and crocodile vitreous forceps are used to grasp the donor button and pull it into the opening of the glide (Figure 21-9). A side entry into the AC is created temporally. The glide is then inverted and positioned at the entrance of the nasal clear-cornea tunnel. The crocodile forceps is then inserted through the side entry wound and passed across the AC, exiting through the clear-cornea tunnel, to grab the donor corneal graft and drag it into the AC (Figures 21-10A and B). The donor lamella is allowed to unfold spontaneously under continuous irrigation. Gentle tapping at the inferior limbus may facilitate centring of the donor graft. The whole maneuver is performed with the aid of continuous irrigation with an AC maintainer inserted at the limbus at the 12:00 o’clock position. An iridectomy is performed, if not already present, in order to prevent pupillary block and Urrets-Zavalia syndrome, secondary to filling of the anterior chamber with air at the end of the surgery. Both the clear-cornea tunnel and the side entry are sutured water-tight with interrupted 10-0 nylon stitches (Figure 21-11). The graft is finally attached to the posterior stromal surface by means of air (Figure 21-12). Triamcinolone acetonide and gentamicin are injected subconjunctivally at the end of the procedure. The eye is patched and the patient is required to lie on his back for 6- 8 hours following the surgery.

When DSAEK is combined with other procedures (e.g. cataract surgery, secondary IOL implantation or exchange, anterior vitrectomy, etc.), these must be usually performed first, as both the donor endothelium itself and the attachment of the graft to the posterior surface of the recipient cornea may be compromised by any additional surgical maneuver (Editorial Note: In combined procedures, the editor first removes the Descemet’s membrane as a single disk, then

A

B

Figures 21-10A and B: Insertion of the graft into the anterior chamber with the “pull through” technique, using vitreous forceps and tissue glide.

performs the combined procedures such as phacoemulsification with PC IOL, etc. and finally the donor corneal disk is attached to the recipient, bare corneal stroma).

Visual and Refractive Results

The visual and refractive results obtained in 20 consecutive cases operated on with the technique described above do not differ substantially from those reported in the past.4,5,8 At a follow-up examination 3 months postoperatively, best spectacle corrected visual acuity (BSCVA) equal to or better than 20/200 was obtained in 19 of 20 cases (95%), while BSCVA better than or equal to 20/40 was recorded

Figure 21-11: The clear-cornea tunnel and the side entry are sutured with interrupted 10-0 nylon stitches, obtaining water-tight closure of both surgical wounds.

Figure 21-12: Graft perfectly centered and adherent to the posterior surface of the recipient cornea. The anterior chamber is left full with air and the patient instructed to lie on his back for 6-8 hours.

in 14 of 20 cases (70%). The outcome was not negatively affected when catarct surgery was combined with DSAEK: BSCVA of at least 20/40 was measured in all 9 patients with advanced Fuchs’ endothelial dystrophy undergoing combined DSAEK and phacoemulsification with implantation of an IOL in the capsular bag. In particular, patient in Figure 21-13 represents the most outstanding result in this series, with an uncorrected visual acuity of 20/20 as early as 1 month postoperatively.

Figures 21-13A and B: Slit-lamp photographs broad-beam (A) and narrow-beam (B), showing a clear central cornea with a well centered 9.0 mm posterior donor graft, 1 month after combined DSAEK, phacoemulsification and PC IOL implanted in the capsular bag. The uncorrected visual acuity was 20/20. The slit-lamp detail (b) outlines the excellent adherence of the graft to the posterior surface of the recipient cornea as well as the clarity of both recipient and donor corneal tissues.

On the other hand, 5 of 6 patients with BSCVA worse than 20/40 had undergone a phacoemulsification procedure complicated by rupture of the posterior capsule and had developed cystoid macular edema. BSCVA of 20/400 in the remaining patient was secondary to advanced age-related macular degeneration.

It must be noticed, that in general, younger patients with primary endothelial failure (Fuchs’ corneal endothelial dystrophy), with or without cataract, tend to have a better visual prognosis. On the other hand, patients with longstanding corneal edema require a longer period of time for visual rehabilitation and are prone to have a more limited visual improvement.

Decreasing the postoperative astigmatism represents one of the most distinctive advantages of DSAEK over conventional PKP surgery. Also in our patients, final astigmatism is low (within 2 diopters in practically all cases) and of the regular type (Figure 21-14). A limited amount of corneal distortion may be present initially in some cases, but it disappears when all corneal sutures are removed (usually 4 to 6 weeks after surgery), similar to what is seen after cataract surgery.

We have observed a slight hyperopic shift (less than 1 diopter) in most of our patients in the early postoperative period. However, this hyperopic shift has regressed completely in the majority of the patients within a few months, corresponding to the reduction of the initial amount of edema at the graft edge. As a consequence of this observation, we believe that transient hyperopic shift may be secondary to an increase in posterior corneal curvature secondary to peripheral edema at the bare edge of the

Figure 21-14: Corneal topographic map obtained from a post-DSAEK patient 1 week following surgery, showing the presence of low-degree regular astigmatism. As opposed to conventional PKP, topographic analysisi is possible as early as few days after DSAEK, confirming the negligible effect of this procedure on the corneal curvature.

grafted donor lamella. Sealing of the wound with time, leads to reduction of the posterior corneal curvature, and normalization of the refraction.

In those patients undergoing combined surgery, DSAEK was found to be particularly effective in targetting the optimal postoperative refraction. In fact, as keratometry of the recipient cornea is not affected substantially by DSAEK, the power of the IOL to be eventually implanted secondarily or exchanged may be calculated more precisely.

Endothelial Cell Density and

Corneal Transparency

To date, the relatively high postoperative endothelial cell loss (up to almost twice as much as after a conventional PKP) remains the main drawback of DSAEK surgery. Preparation of the donor lamella by means of microkeratome-assisted dissection has shown a negligible effect on donor corneal endothelial cells. Instead, intraoperative manipulation of the donor graft (i.e. folding, grabbing with forceps, inserting into the AC and finally unfolding) has shown to closely correlate with donor endothelial survival rate. Thin donor grafts (below 100 µm thickness) are especially difficult to manipulate and are therefore exposed to the risk of higher cell loss. For this reason, a too deep dissection of the donor cornea may result in a disappointing final result. Before resorting to the technique described in detail in this chapter, we operated eight patients using the “taco” technique, and we experienced early decompensation of the graft in two cases, while in the remaining six, an endothelial cell loss up to 50% was recorded (Figure 21-15A). Instead, “dragging” the graft into the AC, as illustrated in Figures 21-10A and B, has proven to minimize the loss of endothelial cells to a level comparable to that of conventional PKP. The endothelial cell counts obtained 6 months postoperatively from the first 9 patients operated on with this technique showed an endothelial cell loss of 18% to 26% of the preoperative counts (Figure 21-15B).

Postoperative transparency and the optical quality of the cornea is an “unsolved problem” of DSAEK. Although corneal clarity seems to recover to normal levels early after surgery, the clinical assessment does not always correlate with vision. Some patients continue to improve their vision, even if refraction has stabilized long before and no change in corneal transparency is clinically evident. On the other hand, some patients with perfectly transparent corneas at slit-lamp examination, still complain of “hazy” vision, with visual acuity failing to reach the expected 20/20 value. Various parameters have been investigated, albeit unsuccessfully, with the purpose of explaining these findings. Interestingly, it has been proven that visual acuity is not related to post-DSAEK corneal thickness and even an increase of up to 30% is still compatible with 20/20 vision, confirming data recorded after epikeratophakia that was published in the past. Understanding the optical properties of corneas undergoing various types of lamellar keratoplasty probably represents the key issue and the most challenging task that corneal researchers and surgeons are presently facing in an attempt to further improve the results of these lamellar procedures.

References

1. Terry MA, Ousley 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;110:755-64.

2. Melles GR, Kamminga N. Techniques for posterior lamellar keratoplasty through a scleral incision. Ophthalmologe 2003; 100:689-95.

3. Terry MA, Ousley PJ. Small-incision deep lamellar endothelial keratoplasty (DLEK): Six-month results in the first prospective clinical study. Cornea 2005;24:59-65.

4. Price FW Jr, Price MO. Descemet’s stripping with endothelial keratoplasty in 200 eyes: Early challenges and techniques to enhance donor adherence. J Cataract Refract Surg 2006;32: 411-8.

5. Price MO, Price FW Jr. Descemet’s stripping with endothelial keratoplasty comparative outcomes with microkeratomedissected and manually dissected donor tissue. Ophthalmology 2006;113:1936-42.

6. Busin M, Monks T, Arffa RC. Endokeratoplasty in the rabbit Model: A new surgical technique for endothelial transplantation. Ophthalmology 1996;103:167.

7. Melles GR, Lander F, Beekhuis WH, Remeijer L, Binder PS. Posterior lamellar keratoplasty for a case of pseudophakic bullous keratopathy. Am J Ophthalmol 1999;127:340-1.

8. Van Rij G, Bartels M. Descemet’s stripping with endothelial keratoplasty in 50 eyes: A refractive neutral corneal transplant (Comment on). J Refract Surg 2006;22:529-30.