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Endothelial Keratoplasty
Letters to the Editor anterior diameter of the femtosecond laser zigzag cut in the recipients and of the donor corneas. This must be somewhere between 8.5 and 9.0 mm. In the study, 17 eyes of 14 patients underwent conventional Barron suction trephination PK performed contemporaneously. Unfortunately, the mean anterior cut diameter in the recipient cornea was not mentioned in the article. I would ask the authors to report the mean anterior diameter and range of the Barron trephine cut in the recipient and of the donor corneas. Since 8.5 or 9 mm grafts are quite large for conventional blade trephination grafts, it is possible that a difference in anterior diameter between the 2 groups exists. If this is true, it would most likely mean that the mean anterior diameter of the graft in one group is larger than the anterior diameter of the graft in the other group of patients. It is obvious that a larger graft diameter results in better optical performance.2 This has nothing to do with femtosecond laser cuts or conventional cuts. Our results of manual trephination of mushroom keratoplasty with an anterior diameter of 9 mm were comparable with the results of the femtosecond laser zigzag incisions in this study.3 GABRIEL VAN RIJ, MD, PHD MARJOLIJN C. BARTELS, MD, PHD ISABEL BLEYEN, MD, PHD BART T.H. VAN DOOREN, MD, PHD ISABELLE E.Y. SAELENS, MD Rotterdam, The Netherlands References 1. Farid M, Steinert RF, Gaster RN, et al. Comparison of penetrating keratoplasty performed with a femtosecond laser zigzag incision versus conventional blade trephination. Ophthalmology 2009;116:1638 – 43. 2. Seitz B, Langenbucher A, Küchle M, Naumann GOH. Impact of graft diameter on corneal power and the regularity of postkeratoplasty astigmatism before and after suture removal. Ophthalmology 2003;110:2162–7. 3. Saelens IE, Bartels MC, van Rij G. Manual trephination of mushroom keratoplasty in advanced keratoconus. Cornea 2008;27:650 –5.
Author reply Dear Editor: We appreciate the interest from Dr. van Rij and his colleagues in our work. We respect his long-standing interest in manually shaped corneal transplant incisions. We agree that, all other factors being equal, the optical quality of penetrating keratoplasty improves as the diameter of the graft increases. Presumably this effect occurs because distortion from the sutures, and the incision itself is further from the central optical zone as graft size increases. Our paper did not report and analyze the graft size because the diameter of a zigzag-shaped femtosecond laser incision encompasses a zone of 1 mm. The most common configuration that we employ has an inner diameter of 8.0 mm and an outer diameter of 9.0 mm, but some of our femtosecond incisions had an inner diameter of 7.5 mm and an outer diameter of 8.5 mm, and a few were 7.0/8.0 mm. Donor and host diameters were equal in
all but a few early cases. In contrast, the manual trephine incisions predominantly were a mixture of 8.25 mm and 8.75 mm donor grafts into recipient beds with diameters of 8.0 mm and 8.5 mm, respectively. Therefore, a useful analysis of the effect of graft size on the optical outcome is not possible with this data set. As we gain further cases, we do intend to compare the results with differentsized zigzag incisions. Finally, we would point out that most corneal transplantation surgeons will not use a 9.0-mm manual trephine graft, except in unusually large corneas, because the sutures and the incision itself are too close to the limbus. With the different configuration of the zigzag incision, an outer diameter of 9.0 mm is feasible in more eyes, and the outer suture pass does not encroach as much on the limbus. If this is the reason for a better optical result with a zigzag incision by increasing the number of patients who are candidates for this size, we view this as a virtue of the technique. MARJAN FARID, MD ROGER F. STEINERT, MD Irvine, California
Endothelial Keratoplasty Dear Editor: We read with great interest and appreciation the paper by Price et al.1 on Descemet’s membrane endothelial keratoplasty (DMEK). They describe their technique for performing DMEK with favorable results. We offer some comments and questions. The authors report that after Descemet’s membrane (DM) was stripped from the donor cornea it forms a roll with the endothelium on the outside. As there is no histological analysis, we assume that the authors reach this conclusion based on previous studies.2,3 The formation of the roll with the endothelium outward has been described before by Melles et al.2 as mentioned by the authors, and also by Sharma et al.3 It has been our experience that the Descemet rolls were not formed immediately. This could have occurred because the sheets were immersed back into the transport media, whereas other authors used saline, balanced salt solution, or corneal storage solution (Optisol; Bausch & Lomb, Rochester, NY).2,3 A smaller diameter sheet used in our study may also have contributed to the later formation of the roll. The roll configuration is important because a surgeon would have to wait for the DM roll to form prior to transplantation in the host. It would be interesting if the authors reported the exact diameter of the donor DM used in their DMEK technique. We have used trypan blue to stain the transparent DM donor tissue so that to aid visualization and subsequent manipulation,4 but we found that these rolled sheets did not significantly stain unless they were traumatized and, therefore, staining did not help us in transplanting these sheets. The average endothelial cell loss in our study of DM preparation in cadaver eyes was 20% over 28 days.3 Also the authors report that after inserted in the eye the donor DM was oriented with the rolls of the scroll facing upward. Indeed the rotation of the roll inside the eye will determine which way the endothelium is orientated. We
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Ophthalmology Volume 117, Number 7, July 2010 have recently proposed a theoretical model5 where we suggested that if the roll is positioned with the outer free edge pointing upwards or toward the cornea and is unravelled using injected air or by other means, then the endothelium is correctly orientated to be applied to the posterior surface of the cornea. When the roll is orientated differently then unraveling of the endothelial cells’ sheet would most likely be in a direction not favorable for correct application. It would be easy accidentally to rotate this delicate and semi-transparent Descemet’s endothelial roll incorrectly inside the eye and not realize particularly if the visualization is impaired through a hazy cornea due to endothelial disease. To aid with correct rotational orientation along with the general difficulty of transplanting such material, we believe that direct endoscopic visualization of the Descemet’s endothelial roll inside the eye during transplantation would be helpful. Endoscopic visualization has been useful in visualizing the posterior surface of the cornea during the stromal air injection technique for deep anterior lamellar keratoplasty.6 IOANNIS ATHANASIADIS, MD, MRCSED ANANT SHARMA, FRCOPHTH Bedford, England References 1. Price MO, Giebel AW, Fairchild KM, Price FW Jr. Descemet’s membrane endothelial keratoplasty: prospective multicenter study of visual and refractive outcomes and endothelial survival. Ophthalmology 2009;116:2361– 8. 2. Melles GR, Lander F, Rietveld FJ, et al. Transplantation of Descemet’s membrane carrying viable endothelium through a small scleral incision. Cornea 2002;21:415– 8. 3. Athanasiadis I, DeWit D, Sharma A, et al. Comment on donor tissue preparation for Descemet membrane endothelial keratoplasty. J Cataract Refract Surg 2009;35:407– 8. 4. Sharma A, Woodman A. Comment on transplantation of Descemet’s membrane carrying viable endothelium through a small scleral incision. Cornea 2002;21:840. 5. Athanasiadis Y, De Wit DW, Sambare C, et al. Rotational importance of descemet endothelial rolls used for descemet membrane endothelial keratoplasty. Cont Lens Anterior Eye 2009;32:145– 6. 6. Moore JE, Herath G, Sharma A. Endoscopic visualisation to aid deep anterior lamellar keratoplasty. Eye 2004;18:188 –91.
Author reply Dear Editor: We appreciate the interesting comments of Athanasiadis and Sharma regarding Descemet’s membrane endothelial keratoplasty (DMEK).1 Like other investigators, we have observed that after Descemet’s membrane (DM) is stripped from the donor stroma, it curls up with the endothelium on the outside. We hypothesize that this happens because the DMEK graft is made up of 2 layers: endothelial cells (EC) and DM. The EC can expand as a result of fluid uptake, whereas DM is relatively inelastic and cannot expand proportionately. The disproportionate expansion of the EC causes the graft to curl with the EC side outward. This hypothesis is supported by the observation that DM usually curls quickly when placed in balanced salt solution (BSS, Alcon, Fort Worth, TX), which is isotonic, whereas it tends
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to curl more slowly if at all in corneal storage solution (Optisol, Bausch & Lomb, Irvine, CA), which is hypertonic. As noted in the Abstract, we used donor DM diameters of 8.5 or 9.0 mm.1 We have not observed an effect of donor diameter on rate of curling. However, we have noted that younger tissue tends to curl more tightly than older tissue, which may correlate with more compact endothelial cells or higher cell density in donors younger than 30 years old. We have used VisionBlue (Dutch Ophthalmic USA, Exeter, NH) in over 1700 endothelial keratoplasty procedures and found that it always strongly stains bare DM, lightly stains stromal tissue, and does not stain intact endothelium. We routinely use it to check for loose or detached tags of DM after stripping DM from the host cornea, as well as to stain the DM in DMEK and Descemet’s membrane automated endothelial keratoplasty (DMAEK) procedures. The strong DM staining by VisionBlue was apparent in Figures 1– 4.1 We are unfamiliar with the staining intensity of other trypan blue formulations, and wonder if you are using some other type of solution or a generic version? We agree that after implantation, the curled DM should be oriented with the rolls of the scroll facing upward so that the endothelial side will correctly face the anterior chamber after it is uncurled. As described in Methods and Discussion, we have found that a slit-lamp attachment on the operating microscope can facilitate discernment of the membrane orientation within the eye.1,2 While the direct endoscopic visualization method suggested by Athanasiadis and Sharma could be used, the efficacy may be influenced by the clock hour orientation of the DM roll relative to the placement of the endoscopic camera, and it would necessitate a more difficult 2-handed technique instead of the 1-handed technique we use. Moreover, we have not yet encountered a case in which we could not see well enough through the edematous cornea to place an EK graft. Certainly, we appreciate all observations and suggestions to help advance the field of endothelial keratoplasty. MARIANNE O. PRICE, PHD FRANCIS W. PRICE, JR. MD Indianapolis, Indiana References 1. Price MO, Giebel AW, Fairchild KM, Price FW Jr. Descemet’s membrane endothelial keratoplasty: prospective multicenter study of visual and refractive outcomes and endothelial survival. Ophthalmology 2009;116:2361– 8. 2. Giebel AW, Price FW. Descemet’s membrane endothelial keratoplasty (DMEK): the bare minimum. In: Price FW, Price MO, eds. DSEK: All You Need to Know about Endothelial Keratoplasty. Thorofare, NJ: Slack, Inc.; 2008:119 – 46.
IOP Changes after DSEK Dear Editor: We read with great interest the recently published article by Vajaranant et al.1 regarding the pattern of intraocular pressure (IOP) changes after Descemet’s stripping endothelial keratoplasty (DSEK) in patients without preexisting glaucoma and in those with preexisting glaucoma, with and without prior glaucoma surgery (GS). The authors con-
Author reply Dear Editor: We appreciate the interest from Dr. van Rij and his colleagues in our work. We respect his long-standing interest in manually shaped corneal transplant incisions. We agree that, all other factors being equal, the optical quality of penetrating keratoplasty improves as the diameter of the graft increases. Presumably this effect occurs because distortion from the sutures, and the incision itself is further from the central optical zone as graft size increases. Our paper did not report and analyze the graft size because the diameter of a zigzag-shaped femtosecond laser incision encompasses a zone of 1 mm. The most common configuration that we employ has an inner diameter of 8.0 mm and an outer diameter of 9.0 mm, but some of our femtosecond incisions had an inner diameter of 7.5 mm and an outer diameter of 8.5 mm, and a few were 7.0/8.0 mm. Donor and host diameters were equal in
all but a few early cases. In contrast, the manual trephine incisions predominantly were a mixture of 8.25 mm and 8.75 mm donor grafts into recipient beds with diameters of 8.0 mm and 8.5 mm, respectively. Therefore, a useful analysis of the effect of graft size on the optical outcome is not possible with this data set. As we gain further cases, we do intend to compare the results with differentsized zigzag incisions. Finally, we would point out that most corneal transplantation surgeons will not use a 9.0-mm manual trephine graft, except in unusually large corneas, because the sutures and the incision itself are too close to the limbus. With the different configuration of the zigzag incision, an outer diameter of 9.0 mm is feasible in more eyes, and the outer suture pass does not encroach as much on the limbus. If this is the reason for a better optical result with a zigzag incision by increasing the number of patients who are candidates for this size, we view this as a virtue of the technique. MARJAN FARID, MD ROGER F. STEINERT, MD Irvine, California
Endothelial Keratoplasty Dear Editor: We read with great interest and appreciation the paper by Price et al.1 on Descemet’s membrane endothelial keratoplasty (DMEK). They describe their technique for performing DMEK with favorable results. We offer some comments and questions. The authors report that after Descemet’s membrane (DM) was stripped from the donor cornea it forms a roll with the endothelium on the outside. As there is no histological analysis, we assume that the authors reach this conclusion based on previous studies.2,3 The formation of the roll with the endothelium outward has been described before by Melles et al.2 as mentioned by the authors, and also by Sharma et al.3 It has been our experience that the Descemet rolls were not formed immediately. This could have occurred because the sheets were immersed back into the transport media, whereas other authors used saline, balanced salt solution, or corneal storage solution (Optisol; Bausch & Lomb, Rochester, NY).2,3 A smaller diameter sheet used in our study may also have contributed to the later formation of the roll. The roll configuration is important because a surgeon would have to wait for the DM roll to form prior to transplantation in the host. It would be interesting if the authors reported the exact diameter of the donor DM used in their DMEK technique. We have used trypan blue to stain the transparent DM donor tissue so that to aid visualization and subsequent manipulation,4 but we found that these rolled sheets did not significantly stain unless they were traumatized and, therefore, staining did not help us in transplanting these sheets. The average endothelial cell loss in our study of DM preparation in cadaver eyes was 20% over 28 days.3 Also the authors report that after inserted in the eye the donor DM was oriented with the rolls of the scroll facing upward. Indeed the rotation of the roll inside the eye will determine which way the endothelium is orientated. We
1459
Ophthalmology Volume 117, Number 7, July 2010 have recently proposed a theoretical model5 where we suggested that if the roll is positioned with the outer free edge pointing upwards or toward the cornea and is unravelled using injected air or by other means, then the endothelium is correctly orientated to be applied to the posterior surface of the cornea. When the roll is orientated differently then unraveling of the endothelial cells’ sheet would most likely be in a direction not favorable for correct application. It would be easy accidentally to rotate this delicate and semi-transparent Descemet’s endothelial roll incorrectly inside the eye and not realize particularly if the visualization is impaired through a hazy cornea due to endothelial disease. To aid with correct rotational orientation along with the general difficulty of transplanting such material, we believe that direct endoscopic visualization of the Descemet’s endothelial roll inside the eye during transplantation would be helpful. Endoscopic visualization has been useful in visualizing the posterior surface of the cornea during the stromal air injection technique for deep anterior lamellar keratoplasty.6 IOANNIS ATHANASIADIS, MD, MRCSED ANANT SHARMA, FRCOPHTH Bedford, England References 1. Price MO, Giebel AW, Fairchild KM, Price FW Jr. Descemet’s membrane endothelial keratoplasty: prospective multicenter study of visual and refractive outcomes and endothelial survival. Ophthalmology 2009;116:2361– 8. 2. Melles GR, Lander F, Rietveld FJ, et al. Transplantation of Descemet’s membrane carrying viable endothelium through a small scleral incision. Cornea 2002;21:415– 8. 3. Athanasiadis I, DeWit D, Sharma A, et al. Comment on donor tissue preparation for Descemet membrane endothelial keratoplasty. J Cataract Refract Surg 2009;35:407– 8. 4. Sharma A, Woodman A. Comment on transplantation of Descemet’s membrane carrying viable endothelium through a small scleral incision. Cornea 2002;21:840. 5. Athanasiadis Y, De Wit DW, Sambare C, et al. Rotational importance of descemet endothelial rolls used for descemet membrane endothelial keratoplasty. Cont Lens Anterior Eye 2009;32:145– 6. 6. Moore JE, Herath G, Sharma A. Endoscopic visualisation to aid deep anterior lamellar keratoplasty. Eye 2004;18:188 –91.
Author reply Dear Editor: We appreciate the interesting comments of Athanasiadis and Sharma regarding Descemet’s membrane endothelial keratoplasty (DMEK).1 Like other investigators, we have observed that after Descemet’s membrane (DM) is stripped from the donor stroma, it curls up with the endothelium on the outside. We hypothesize that this happens because the DMEK graft is made up of 2 layers: endothelial cells (EC) and DM. The EC can expand as a result of fluid uptake, whereas DM is relatively inelastic and cannot expand proportionately. The disproportionate expansion of the EC causes the graft to curl with the EC side outward. This hypothesis is supported by the observation that DM usually curls quickly when placed in balanced salt solution (BSS, Alcon, Fort Worth, TX), which is isotonic, whereas it tends
1460
to curl more slowly if at all in corneal storage solution (Optisol, Bausch & Lomb, Irvine, CA), which is hypertonic. As noted in the Abstract, we used donor DM diameters of 8.5 or 9.0 mm.1 We have not observed an effect of donor diameter on rate of curling. However, we have noted that younger tissue tends to curl more tightly than older tissue, which may correlate with more compact endothelial cells or higher cell density in donors younger than 30 years old. We have used VisionBlue (Dutch Ophthalmic USA, Exeter, NH) in over 1700 endothelial keratoplasty procedures and found that it always strongly stains bare DM, lightly stains stromal tissue, and does not stain intact endothelium. We routinely use it to check for loose or detached tags of DM after stripping DM from the host cornea, as well as to stain the DM in DMEK and Descemet’s membrane automated endothelial keratoplasty (DMAEK) procedures. The strong DM staining by VisionBlue was apparent in Figures 1– 4.1 We are unfamiliar with the staining intensity of other trypan blue formulations, and wonder if you are using some other type of solution or a generic version? We agree that after implantation, the curled DM should be oriented with the rolls of the scroll facing upward so that the endothelial side will correctly face the anterior chamber after it is uncurled. As described in Methods and Discussion, we have found that a slit-lamp attachment on the operating microscope can facilitate discernment of the membrane orientation within the eye.1,2 While the direct endoscopic visualization method suggested by Athanasiadis and Sharma could be used, the efficacy may be influenced by the clock hour orientation of the DM roll relative to the placement of the endoscopic camera, and it would necessitate a more difficult 2-handed technique instead of the 1-handed technique we use. Moreover, we have not yet encountered a case in which we could not see well enough through the edematous cornea to place an EK graft. Certainly, we appreciate all observations and suggestions to help advance the field of endothelial keratoplasty. MARIANNE O. PRICE, PHD FRANCIS W. PRICE, JR. MD Indianapolis, Indiana References 1. Price MO, Giebel AW, Fairchild KM, Price FW Jr. Descemet’s membrane endothelial keratoplasty: prospective multicenter study of visual and refractive outcomes and endothelial survival. Ophthalmology 2009;116:2361– 8. 2. Giebel AW, Price FW. Descemet’s membrane endothelial keratoplasty (DMEK): the bare minimum. In: Price FW, Price MO, eds. DSEK: All You Need to Know about Endothelial Keratoplasty. Thorofare, NJ: Slack, Inc.; 2008:119 – 46.
IOP Changes after DSEK Dear Editor: We read with great interest the recently published article by Vajaranant et al.1 regarding the pattern of intraocular pressure (IOP) changes after Descemet’s stripping endothelial keratoplasty (DSEK) in patients without preexisting glaucoma and in those with preexisting glaucoma, with and without prior glaucoma surgery (GS). The authors con-