|Year : 2010 | Volume
| Issue : 5 | Page : 457-463
Advances in keratoplasty procedures: A review
Rajesh Sinha1, Noopur Gupta1, Namrata Sharma1, Jeewan S Titiyal1, Rasik B Vajpayee2
1 R. P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
2 Centre for Eye Research Australia, Melbourne, Australia
|Date of Web Publication||2-Aug-2010|
S-7, RP Centre, All India Institute of Medical Sciences (AIIMS), New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sinha R, Gupta N, Sharma N, Titiyal JS, Vajpayee RB. Advances in keratoplasty procedures: A review. Indian J Ophthalmol 2010;58:457-63
|How to cite this URL:|
Sinha R, Gupta N, Sharma N, Titiyal JS, Vajpayee RB. Advances in keratoplasty procedures: A review. Indian J Ophthalmol [serial online] 2010 [cited 2015 Jul 5];58:457-63. Available from: http://www.ijo.in/text.asp?2010/58/5/457/67064
The procedure of corneal transplantation has evolved with time. Various innovative techniques in partial thickness as well as full thickness keratoplasty have been reported in the literature. This review aims to highlight the recent refinements in microsurgical techniques published over the last couple of years such as increased precision in deep stromal dissection, sophisticated automation, and advanced processing available for the donor tissue that have lead to the expansion of application of corneal transplantation especially the lamellar keratoplasty for treating various corneal disorders.
| Evolution and Recent Advances|| |
Ritter et al. (Expert Rev Clin Immunol. 2009;5(6):749-64) reviewed novel therapeutic strategies using recombinant viruses as gene-transfer vehicles and, more recently, the use of gene-modified dendritic cells or regulatory T cells to protect the graft from immune-mediated rejection. They observed that the genetic modification of the graft or cells prior to transplantation is an attractive approach to protect the graft from allogeneic rejection.
Tan et al. (Ann Acad Med Singapore. 2009;38(4):332-8) in their review highlighted the main advantages and disadvantages of the new lamellar corneal procedures. Selective lamellar surgical replacement of only the diseased corneal layers while retaining unaffected layers represents a new paradigm shift in the field. Recent advancements in surgical techniques and instrumentation have resulted in several forms of manual, microkeratome, and femtosecond laser-assisted lamellar procedures. While significant technical and surgical challenges are involved in performing lamellar micro-dissection of a tissue which is only 0.5 mm thick, the benefits of a more controlled surgical procedure and improved graft survival rates have resulted in a shift away from conventional penetrating keratoplasty (PK).
| Deep Anterior Lamellar Keratoplasty|| |
Awan et al. (Br J Ophthalmol. 2010 Jun 15 [Epub ahead of print]) determined the visual outcome, graft survival, and complications after deep anterior lamellar keratoplasty (DALK) in 18 patients with herpes simplex virus (HSV)-related corneal scarring. Fifty percent of the eyes achieved visual acuity of 6/12 or better postoperatively. Six eyes (33%) had recurrence of HSV-related inflammation, eight eyes (including four eyes with recurrence of HSV) developed graft rejection, and four eyes (including two eyes with recurrence of HSV) had bacterial keratitis. The graft survival rate was 83%.
Jhanji et al. (Int Ophthalmol. 2010;30(3):291-5) analyzed the reasons for intraoperative perforation of Descemet's membrane (DM) in DALK during learning curve. The main reasons for perforation of DM were excessive air injection (four eyes) and improper surgical maneuvers (three eyes), requiring the need for conversion to PK.
Feizi et al. (Cornea 2010;29(2):177-82) evaluated the visual and refractive outcomes after DALK using the big-bubble technique in 129 eyes with keratoconus. The mean preoperative best corrected visual acuity (BCVA) was 1.27 ± 0.4 logarithm of the minimum angle of resolution (logMAR), increasing to 0.25 ± 0.2 logMAR at final follow-up examination (P < 0.001). The postoperative mean spherical equivalent (SE) refractive error, refractive astigmatism, and keratometric astigmatism were −3.41 ± 3.1 diopters (D), 3.04 ± 2.3 D, and 3.67 ± 2.1 D, respectively. Bared DM was achieved in 103 eyes, whereas in 23 eyes pre-Descemet dissection was performed. DM perforation occurred in five eyes.
Sarnicola et al. (Cornea 2010;29(1):60-4) in their experience with DALK in HSV scars reported 3.8% of DM rupture. The postoperative BCVA was 20/20 in 52% and 20/30 in 80%.
Sarnicola et al. (Cornea 2010;29(1):53-9) reported the outcomes of DALK in 236 eyes with keratoconus. There was no difference in visual acuity between the predescemetic (pd) DALK and descemetic DALK (dDALK) groups at an average follow-up of 30.4 months, although the eyes in the dDALK group seemed to have faster visual recovery. The visual outcomes were comparable to standard PK, avoiding the risk of endothelial rejection.
Lake et al. (Cornea 2009;28(5):489-92) evaluated the outcome of DALK for ectasia within or outside the graft-host interface in eyes with previous PK. Seven eyes had DALK, four developed
DM tears, and two eyes had deep graft-host dehiscence from the previous PK intraoperatively. At 12 months, mean uncorrected visual acuity (UCVA) improved from 1.157 to 0.74. They concluded that DALK can be successfully performed over a previous PK.
Farias et al. (Cornea 2008;27(9):1030-6) compared the efficacy of lyophilized corneas for DALK in patients with keratoconus with optisol cornea and found similar outcome in terms of visual acuity (VA), topography, pachymetry, specular microscopy, contrast sensitivity, and confocal microscopy.
Bahar et al. (Am J Ophthalmol. 2008;146(6):905-12) compared the visual outcomes following DALK, PK, and manual top-hat PK (TH-PK) in eyes with keratoconus and found them to be comparable. Although DALK and TH-PK induce more HOA, they speed up the time to suture removal and provide higher endothelial cell density at 1 year of follow-up.
Noble et al. (Cornea 2007;26(1):59-64) reviewed the visual outcome and complications of DALK using Melles technique in 80 eyes. Perforation of DM occurred in 11 eyes, of which 7 required conversion to PK. At latest follow-up, BCVA of 6/6 or better was present in 24.7%, 6/9 or better in 69.9%, and 6/12 or better in 84.9% of the eyes. Rejection episodes occurred in 9.6% of the eyes but were successfully reversed in all eyes.
Leccisotti (J Cataract Refract Surg. 2007;33(5):825-9) evaluated the functional and endothelial prognosis after DM perforation during DALK in a series of 35 eyes. In all eight eyes, DALK could be completed. The mean postoperative BCVA was 0.8 ± 0.13 and the mean postoperative refractive astigmatism was 2.09 ± 0.98 D. The mean endothelial cell loss, evaluated in seven eyes, was 12 ± 11% at 1 month (P < 0.05) and 14 ± 12% at 12 months. However, eyes with perforation requiring reformation of the anterior chamber had more than 20% of endothelial loss.
| Enzyme-assisted DALK|| |
Bonci et al. (Eur J Ophthalmol. 2010 Mar 22. [Epub ahead of print]) described a new surgical technique of dDALK with the help of the enzymatic hyaluronidase solution. There were no perforations and minimal complications (second anterior chamber in four eyes) on the first day, which spontaneously resolved after 7 days. The enzyme application to the recipient cornea made stromal dissection easier.
Corneal morphology and function post-DALK
Feizi et al. (Cornea 2010 May 20) compared the cellular changes of donor corneal tissue after DALK and PK by a confocal microscope. The keratocyte density in the PK group was comparable to those in the normal group in all three layers, whereas it was significantly reduced in the DALK group. The arrangement of keratocyte was also profoundly altered after DALK.
Jafarinasab et al. (Cornea. 2010 Feb 15 [Epub ahead of print]) in their study reported that the dissection plane in DALK using the big-bubble technique can be within corneal stroma rather than exactly between stroma and DM.
Ceccuzzi et al. (Ophthalmologica. 2010;224(4):247-50) reported that the average percentage of recovery of corneal sensitivity was 91% at 2 years after DALK.
DALK versus PK
Javadi et al. (Cornea 2010 Feb 17 [Epub ahead of print]) compared big-bubble DALK technique to PK in patients with keratoconus. The mean postoperative SE and BCVA were comparable.
Jones et al. (Invest Ophthalmol Vis Sci. 2009;50(12):5625-9) reported a higher overall failure rate of DALK than PK.
Han et al. (Am J Ophthalmol. 2009;148(5):744-51) compared outcomes after PK and two techniques of DALK, modified Anwar technique (descemetic or DALKa group), and manual predescemetic (DALKm group), in patients with keratoconus. There was no significant difference in BCVA, mean SE (P = 0.72) and astigmatism (P = 0.88) between the groups. The DALK group had a significantly lower incidence of complications, including allograft rejection and glaucoma. The graft survival rate of both PK and DALKa groups was 100%, whereas that of the DALKm group was 73% at 3 years (P = 0.000 between PK and DALKm groups).
Ardjomand et al. (Am J Ophthalmol. 2007;143(2):228-35) concluded that the main parameter for good visual function after DALK for keratoconus is the thickness of the residual recipient stromal bed. A residual bed of <20 μ can achieve a similar visual result as PK.
Parthasarathy et al. (Cornea 2007;26(8):1021-3) reported that DALK with total removal of infected stromal tissue may be performed in medically unresponsive cases of Acanthamoeba keratitis, with no recurrence of Acanthamoeba infection.
Cataract surgery post-DALK
Leccisotti et al. (Eur J Ophthalmol. 2010;20(4):680-3) performed phacoemulsification and intraocular lens (IOL) implantation after DALK in 16 patients. No intraoperative or postoperative complications were noted and endothelial cell loss was not significant.
Mannan et al. (Cornea 2007;26(5):636-8) reported a case of DM detachment (DMD) after cataract surgery in an operated case of DALK, which required intracameral gas injection.
DALK after Intacs
Titiyal et al. (J Ophthalmol. 2010 Mar 23 [Epub ahead of print]) performed DALK with Intacs explantation in two patients with poor visual outcome after Intacs implantation for keratoconus correction. DALK could be successfully completed without any postoperative complications. At 2 years of follow-up, the grafts were clear in both patients, with a BCVA of 20/25.
DALK after laser in situ keratomileusis
Javadi et al. (J Cataract Refract Surg. 2010;36(7):1156-60) evaluated big-bubble DALK to manage keratectasia after laser in situ keratomileusis (LASIK) in 11 eyes of 10 patients. The mean UCVA increased from 20/400 to 20/160 after DALK (P = 0.39) and BCVA, from 20/160 to 20/40 (P = 0.007).
Urrets--Zavalia syndrome post-DALK
Niknam et al. (Cornea 2009;28(10):1187-90) reported four cases that developed fixed dilated pupil after DALK was performed for treating keratoconus and granular corneal dystrophy.
Astigmatism correction post-DALK
Javadi et al. (Cornea 2009;28(10):1130-4) reported that relaxing incisions and suturing at the steep meridian followed by selective suture removal can effectively and predictably reduce post-DALK astigmatism in patients with keratoconus.
DALK in corneal dystrophy
Salouti et al. (Cornea 2009;28(2):140-3) observed that although granular corneal dystrophy is likely to recur after DALK, this technique can restore and preserve useful visual function for a significant period in patients.
Park et al. (Cornea 2007;26(9):1132-5) reported good results of DALK in patients with recurrent Avellino dystrophy after phototherapeutic keratectomy (PTK).
Vajpayee et al. (Am J Ophthalmol. 2007;143(6):954-7) successfully performed big-bubble DALK in mucopolysaccharidoses (n = 2), macular corneal dystrophy (n = 5), lattice corneal dystrophy (n = 1), granular corneal dystrophy (n = 1), and stromal scar attributable to infectious keratitis (n = 1). No intraoperative or postoperative complications were observed. All patients achieved a BCVA of 20/40 or better at the end of 6 months.
Automated lamellar therapeutic keratoplasty
Vajpayee et al. (Acta Ophthalmol Scand. 2006;84(6):771-3) observed that automated lamellar therapeutic keratoplasty (ALTK) is safe and effective for diseases affecting the anterior to mid-stroma of the cornea.
Tan et al. (Am J Ophthalmol. 2004;138(6):1067-9) performed ALTK for the treatment of post-photorefractive keratectomy (PRK) corneal scarring and thinning with significant residual myopia. ALTK was first performed to remove the scar and to augment corneal thickness, and a subsequent LASIK procedure was performed to correct the residual myopia with good results.
Tan (Cornea 2006;25(10):1217-9) described a modified ALTK technique and concluded that ALTK combined with Hanna trephination enables precise control of both the depth and diameter of lamellar dissection during surgery, removes the need for any form of manual dissection, and may therefore improve optical and visual outcomes in lamellar keratoplasty.
Chawla et al. (Ophthalmic Surg Lasers Imaging. 2010;9:1-3) reported a case of graft infection with Aureobasidium pullulans following ALTK for trachomatous keratopathy which ultimately required a therapeutic PK to salvage the eye.
Kawashima et al. (J Med Case Reports. 2007;1:10) described the development of presumed immune-mediated stromal rejection after ALTK and its reversal after the initiation of intensive topical corticosteroid therapy.
"Tuck in" lamellar keratoplasty
Kaushal et al. (Br J Ophthalmol. 2008;92(2):286-90) performed "tuck in" lamellar keratoplasty (TILK) that included a central lamellar keratoplasty with intrastromal tucking of the peripheral flange in patients with corneal ectasia with peripheral corneal involvement. A significant decrease in the mean refractive astigmatism from 5.93 ± 3.06 D to 3.23 ± 1.14 D (P = 0.037) was seen and all patients had a BCVA ≥20/80.
| Endothelial Keratoplasty|| |
Deep lamellar endothelial keratoplasty
Fillmore et al. (Cornea 2010;29(6):601-6) reported that deep lamellar endothelial keratoplasty (DLEK) provides good VA (≥20/40) for the majority of patients at 1 year with stable refractive error compared with baseline.
Wandling Jr et al. (Cornea 2010 May 28 [Epub ahead of print]) reported an escalation of glaucoma therapy after DLEK in 16.3% eyes during a mean follow-up period of 27.1 months.
McLaren et al. (Am J Ophthalmol. 2009;147(6):959-65) evaluated high-order aberrations (HOA) induced by the anterior corneal surface after DLEK and PK in 25 patients with Fuchs dystrophy. HOAs from the anterior corneal surface were higher after PK.
Huang et al. (Cornea 2009;28(2):157-62) noted that in cases of complex bullous keratopathy with severe vision loss, DLEK combined with other intraocular surgeries is a feasible and effective procedure to significantly improve VA to a functional level in most patients.
Huang et al. (Arch Ophthalmol. 2009;127(1):33-6) further reported that DLEK is efficacious in the treatment of ICE syndrome in phakic eyes, with rapid visual rehabilitation and low incidence of postoperative complications.
Yepes et al. (Cornea 2007;26(5):530-3) evaluated visual acuity, topography, and endothelial cell density (ECD) 1 year after DLEK in 35 patients. The BCVA was 0.33 ± 0.12 compared with 0.15 ± 0.15 preoperatively and the mean endothelial cell loss was 45%.
Terry et al. (Ophthalmology 2007;114(4):631-9) reported endothelial survival over a 2-year period after two techniques of DLEK: large-incision (n = 36) and small-incision (n = 62) DLEK. The average cell loss from preoperative donor cell measurements was 26 ± 16% at 12 months, and 37 ± 27% at 24 months. The cell loss from small-incision DLEK surgery was significantly greater than that from large-incision DLEK surgery at 12 months (P = 0.013) and 24 months (P < 0.001), which they attributed to the folding of tissue in the small-incision DLEK technique.
Mashor et al. (Ophthalmology 2010;117(4):680-6) evaluated the long-term outcome of small-incision DLEK in 60 eyes. The mean SE and refractive astigmatism were −0.18 ± 1.62 D and 1.67 ± 1.36 D, respectively, at 1 year after surgery and remained stable at 2, 3, and 4 years.
The number of patients, who achieved ≥20/40, increased from a preoperative level of 13.5% to 44.1%, 40%, 48.4%, and 50% at 1, 2, 3, and 4 years after surgery, respectively. The mean ECD decreased by 43% at 1 year after surgery; an additional yearly decrease by 14%, 4%, and 1% was found at 2, 3, and 4 years, respectively. Complications included 4 graft dislocations, 2 primary graft failures, 5 rejections, and 12 secondary failures, with 27.5% graft failure at 4 years.
Terry et al. (Trans Am Ophthalmol Soc. 2007;105:530-63) performed a study on small-incision DLEK and reported good visual outcome with minimal refractive astigmatic change; however, progressive ECD decrease over time was of concern. Complications included one primary graft failure and four dislocations into the anterior chamber.
DLEK with anterior chamber intraocular lens
Chen et al. (Cornea 2010;29(2):162-6) assessed the impact of a retained open-loop anterior chamber intraocular lens (ACIOLs) on endothelial cell loss after DLEK. Mean endothelial cell loss was 37% at 6 months (n = 9, P = 0.001), 36% at 1 year (n = 6, P = 0.001), and 41% at 2 years (n = 5, P = 0.002) after surgery.
Corneal morphology post-DLEK
Ferre et al. (Cornea 2010;29(7):737-44) assessed the DLEK wound anatomy and its evolution 12 months postoperatively, using optical coherence tomography (OCT) in eight eyes. A posterior gap was observed in four eyes. At 12 months, the mean gap, depth, and width were 242 ± 67, 101 ± 45, and 87 ± 29 μ, respectively. A step was documented in all DLEK eyes (average step height 108 ± 24 μ). A micrograft detachment was observed in one case and tissue compression in another. OCT was found to be a very useful tool for DLEK corneal wound architecture analysis.
DLEK versus PK
Heidemann et al. (Cornea 2008;27(2):161-7) observed that DLEK surgery resulted in more rapid visual recovery, significantly less regular and irregular astigmatism, and less change in SE than PK surgery. Endothelial cell loss was not significantly different.
Descemet stripping endothelial keratoplasty
Holz et al. (J Cataract Refract Surg. 2008;34(2):211-4) evaluated changes in the corneal profile after Descemet stripping endothelial keratoplasty (DSEK) using anterior segment OCT. Monthly graft thinning rates were 5.2 μ per month at the vertex, 7.9 μ per month 1.5 mm from the vertex, and 26 μ per month at the edges, with the edges thinning significantly faster than the cornea vertex (P = 0.0024) and the points on either side of the 3.0 mm visual axis (P = 0.0018). The mean SE showed an initial hyperopic shift that decreased over time. The results suggest that IOLs should be targeted to −1.00 to −1.25 D of myopia for combined DSEK and cataract procedures.
Vajaranant et al. (Ophthalmology 2009;116(9):1644-50) characterized the pattern of intraocular pressure (IOP) changes after DSEK in patients without preexisting glaucoma. Out of 400 eyes enrolled, 315 eyes had no glaucoma (C); 64 had glaucoma with no previous glaucoma surgery (G); and 21 eyes had prior glaucoma surgery (GS). The incidence of postoperative IOP elevation by the study criteria was 35%, 45%, and 43% for groups C, G, and GS, respectively.
Lee et al. (Ophthalmology 2009;116(9):1818-30) in their review reported that the most common complication from DSEK included posterior graft dislocations, followed by graft rejection, primary graft failure, and iatrogenic glaucoma. The mean endothelial cell loss was 37% at 6 months, and 42% at 12 months. The graft survival at 1 year ranged from 55% to 100%.
Variations in surgical technique
Unterlauft et al. (Cornea 2010 Jun 30 [Epub ahead of print]) reported that DSEK with donor tissue of 10.0 mm diameter obtained from a normal-sized donor button can be performed safely and effectively in cases of unilateral buphthalmos and secondary corneal decompensation.
Huang et al. (Zhonghua Yan Ke Za Zhi. 2010;46(3):233-7) used temporary anchor sutures for endothelial graft fixation in DSEK in aphakic eyes and reported that the technique was easy to perform and effectively prevented graft dislocation and detachment into the vitreous cavity.
Cataract surgery post-DSEK
Price et al. (Br J Ophthalmol. 2010 May 27) performed cataract extraction after DSEK in 22 eyes without complication and all grafts remained clear with median follow-up of 18 months.
Descemet stripping automated endothelial keratoplasty
Knecht et al. (Am J Ophthalmol. 2010 Jun 28 [Epub ahead of print]) evaluated the intraoperative use of handheld Fourier-domain OCT during Descemet stripping automated endothelial keratoplasty (DSAEK) to assess the donor-host interface. The central 3 mm of each cornea was scanned. All patients had no detectable interface gap on day 1. They concluded that donor adherence can occur in spite of residual interface space at the end of surgery.
Chen et al. (Cornea 2010 Jun 10) reported that the mean endothelial cell loss after DSAEK using a modified 40/60 underfolding technique was 26% at 6 months and 27% at 12 months. The decrease in the cell count from 6 months to 12 months was not statistically significant.
Muftuoglu et al. (Ophthalmology 2010;117(5):878-84) compared the corneal higher order aberration (HOA) after DSAEK and PK and in age-matched controls. Although the mean anterior corneal total HOAs of the central 4 and 6 mm were significantly higher in eyes that underwent PK than in eyes that underwent DSAEK and in controls (P < 0.01), there was no significant difference in anterior corneal total HOAs of the central 4 and 6 mm between eyes that underwent DSAEK and controls. Although posterior corneal HOAs were significantly higher in eyes that underwent DSAEK, anterior corneal HOAs were not significantly different in eyes that underwent DSAEK than those of age-matched controls.
Phillips et al. (Cornea 2010;29(5):534-40) in their study observed that DSAEK surgeries in eyes with previous glaucoma filtering procedures were performed without primary graft failure and with reasonably low dislocation (3.6%) and graft decentration (3.6%) rates.
Price et al. (Cornea 2010;29(5):523-7) assessed the effect of incision width (5.0 and 3.2 mm) on graft survival and endothelial cell loss 6 months and 1 year after DSAEK. One-year graft survival rates were comparable (98% versus 97%) in the 5.0- and 3.2-mm groups, respectively (P = 1.0). Complications included graft dislocation, graft rejection episodes, and elevated IOP occurring at similar rates in both groups (P ≥ 0.28). Percent endothelial cell loss was 27 ± 20% (n = 55) versus 40 ± 22% (n = 71; 6 months) and 31 ± 19% (n = 45) versus 44 ± 22% (n = 62; 12 months) in the 5.0- and 3.2-mm incision groups, respectively (both P < 0.001). One year after DSAEK, overall graft success was comparable for the two groups; however, the 5.0-mm incision width resulted in substantially lower endothelial cell loss at 6 and 12 months.
Lombardo et al. (Graefes Arch Clin Exp Ophthalmol. 2010;248(3):421-7) observed that the DSAEK triple procedure provides negligible changes in the surface topography, however with a variable amount of hyperopic shift postoperatively.
Kumar et al. (Cornea 2010;29(1):13-8) measured corneal sensation after DSAEK in 52 eyes of 29 patients in the early postoperative period (<6 months). Although there was mild hypesthesia of the corneal epithelium overlying the donor lenticule, they found no statistically significant difference in corneal sensation compared to controls.
Shih et al. (Am J Ophthalmol. 2009;148(6):837-43) reported graft detachment as the most common complication after DSAEK followed by idiopathic graft failure, graft rejection, choroidal effusion, epithelial ingrowth, endophthalmitis, pupillary block, and suture abscess.
Scorcia et al. (Ophthalmology 2009;116(9):1651-5) observed that DSAEK grafts were significantly thicker in the periphery and mid-periphery than in the center at all examination times. The difference in thickness between center and periphery of the DSAEK graft induces a change in posterior corneal curvature, resulting in a hyperopic shift that decreases with time.
Koenig (Ophthalmic Surg Lasers Imaging 2010;41(4):485-6) described a technique to improve centration of the trephination of the donor corneal lenticula during DSAEK. Following resection of the anterior corneal lamella with the microkeratome, a 10-mm trephine stained with gentian-violet dye is used to mark the perimeter of the resection bed. The remaining donor cornea is centered on the Barron-Hessburg punching block endothelial side-up using the easily seen annular mark as a guide. This simple technique allows the surgeon performing DSAEK to consistently punch the donor lenticule within the margins of the anterior lamellar resection.
Bahar et al. (Am J Ophthalmol. 2009;147(2):220-6) compared two insertion methods in DSAEK: Busin guide-assisted versus forceps-assisted insertion of the corneal lenticule graft. No significant differences were noted in the intraoperative or postoperative complications. Endothelial cell loss was significantly lower in the Busin guide-assisted DASEK group: 25% loss versus 34.3% loss in the forceps-assisted DSAEK group (P = 0.04).
DSAEK versus PK
Yamaguchi et al. (Cornea 2010 Jun 18. [Epub ahead of print]) noted that the regular astigmatism and tilt components of the anterior surface, and HOAs of anterior surface were significantly lower after DSAEK than after PK at 1 and 3 months (P < 0.001), whereas there was no difference in astigmatism of the posterior surface between the groups (P = 0.07, 0.22).
Price et al. (Ophthalmology 2010;117(3):438-44) in another study reported that percent endothelial cell loss was 34 ± 22% versus 11 ± 20% (6 months) and 38 ± 22% versus 20 ± 23% (12 months) in the DSAEK and PK groups, respectively (both P < 0.001). At 1 year, the overall graft success was comparable in both groups but endothelial cell loss was higher with DSAEK.
Bahar et al. (Cornea 2009;28(5):485-8) compared the visual outcomes and complications rate after PK and DSAEK in the fellow eye of the same subjects. All the patients in this study preferred the DSAEK operation. The UCVA, BCVA, astigmatism, and contrast acuity were significantly better in the DSAEK operated eyes.
DSAEK versus DLEK
Bahar et al. (Br J Ophthalmol. 2009;93(2):186-90) studied records of 14 patients (28 eyes) who underwent DLEK in one eye and DSAEK surgery in their fellow eye between 2003 and 2007. Nine (75%) of the 12 patients perceived better vision in the DSAEK operated eye. Ten (83%) of them preferred the outcomes of the DSAEK surgery. The intra- and postoperative complications were comparable between both procedures. However, the DLEK procedure was associated with a significantly higher degree (P < 0.05) of higher order aberrations (HOA).
DSEK versus DSAEK
Terry et al. (Ophthalmology 2008;115(3):488-96) reported that the average endothelial loss at 6 months and 12 months after DSEK was 34 ± 12% and 35 ± 13%, respectively. There was no statistical difference between cell loss from DSEK and DSAEK procedures at 6 or at 12 months.
DSAEK with cultured endothelial cells
Honda (Arch Ophthalmol. 2009;127(10):1321-6) investigated the feasibility of DSAEK using cultured human corneal endothelial cells (HCECs) in an animal model and concluded that it may be a novel therapeutic approach to treat corneal endothelial dysfunction.
Comparison of PK, DLEK, DSEK, and DSAEK
Bahar et al. (Ophthalmology 2008;115(9):1525-33) compared the outcome after PK, DLEK, DSEK, and DSAEK and noted that the mean BCVA at 1 year was 20/53 in the PK group, 20/80 in the DLEK group, 20/56 in the DSEK group, and 20/44 in the DSAEK group. The mean SE was similar in all the groups, but tended toward hyperopia in DSEK and DSAEK groups. Early postoperative donor disc dislocations occurred in 8.8% patients in DLEK, 12.5% in DSEK, and 15.6% in the DSAEK group (P = 0.0004). Primary graft failure occurred in 2.1% of PK cases, 2.9% of DLEK cases, and 2.2% of DSAEK cases. Endothelial cell loss was similar.
Descemet membrane endothelial keratoplasty
Cursiefen et al. (Ophthalmologe 2010;107(4):370-6) concluded that visual rehabilitation seems to be faster and better with Descemet membrane endothelial keratoplasty (DMEK) compared to PK.
Kwon et al. (J Refract Surg. 2010;25:1-8) observed that CCT after DMEK in Fuchs' dystrophy decreased significantly and the posterior corneal surface displaced forward, without a significant change in anterior keratometric values or keratometric astigmatism.
Price et al. (Ophthalmology 2009;116(12):2361-8) noted that compared with DSAEK, DMEK provided a significantly higher rate of 20/20 and 20/25 vision, with comparable endothelial loss.
Ham et al. (Am J Ophthalmol. 2009;148(4):521-7) observed that DMEK may be associated with a decrease in donor ECD of approximately 25% in the early postoperative phase.
Balachandran et al. (Am J Ophthalmol. 2009;148(2):227-34) reported spontaneous recovery of corneal transparency in two cases with nearly complete graft detachment after DMEK. The VA improved to 20/50 and 20/25 at 3 months to 20/28 and 20/20, respectively, at 9 months.
Ham et al. (Arch Ophthalmol. 2009;127(3):252-5) reported that visual recovery after DMEK may be faster and more complete than with other endothelial keratoplasty techniques.
Dapena et al. (Curr Opin Ophthalmol. 2009;20(4):299-307) opined that DMEK may have higher clinical potential with 75% of cases reaching 20/25 or better within 1-3 months.
Studeny et al. (Br J Ophthalmol. 2010;94(7):909-14) described a novel technique for the preparation and transplantation of posterior corneal lamellae consisting of endothelium and bare DM with a stromal supporting rim (DMEK-S). At the end of the follow-up, 10 out of 18 eyes achieved a BCVA of 1.0 or better, and 17 reached 0.5 or better. Primary graft failure occurred in two eyes. The average endothelial cell loss was 44%.
McCauley et al. (J Cataract Refract Surg. 2009;35(10):1659-64) described an endothelial keratoplasty technique in which DM is transplanted with a peripheral ring of corneal stroma. The graft's stromal rim allows it to spontaneously unfold once inside the eye.
Lie et al. (J Cataract Refract Surg. 2008;34(9):1578-83) opined that Descemet grafts for transplantation in DMEK procedures can be surgically prepared from organ-cultured corneal rims and stored for an additional 3 weeks with acceptable endothelial cell loss.
| Femtosecond Laser in Corneal Surgery|| |
Maier et al. (Klin Monbl Augenheilkd. 2010;227(6):453-9) reviewed the therapeutic applications of the femtosecond (FS) laser in corneal surgery. In this context it is used for profiled trephinations in PK where various profiles of the cutting edge can be designed (e.g., top-hat profile, mushroom profile, zig-zag profile) and also for lamellar procedures.
Choi et al. (Cornea 2010 May 26) reported that eccentric lamellar keratolimbal allografting with FS laser is an effective and a time-saving surgical method to treat peripheral corneal pathologies.
Femtosecond laser-assisted PK versus conventional surgery
Kim (Cornea 2009;28(7):812-6) in an animal study reported that FS laser use is safe for the endothelium at the graft center and has less harmful effects on the endothelium at the incision area than does conventional trephination.
Bahar et al. (Br J Ophthalmol. 2009;93(1):73-8) compared the outcomes of IntraLase-enabled TH-PK (IEK) versus manual TH-PK and conventional PK. At 12 months, the mean logMAR BCVA was 0.32 ± 0.31 in the IEK group, 0.53 ± 0.36 in the TH-PK group (P = 0.03), and 0.39 ± 0.30 in the conventional PK group (P = 0.4). The complications rate and HOA were similar; however, the mean endothelial cell loss was significantly lower at 12 months in IEK and TH-PK groups versus conventional PK (32.4% and 22.3% versus 40.8%, respectively, P = 0.05).
Por et al. (Am J Ophthalmol. 2008;145(5):772-4) reported that the Femtec laser reliably trephines both donor and recipient corneas for PK, with good visual outcomes and relatively low degrees of astigmatism. Trephination cuts were straight and performed 90° to the corneal surface. Tissue bridges were bluntly separated with a Barrett phacochopper.
Bahar et al. (Cornea 2008;27(2):209-11) in their study noted that FS laser-assisted top-hat wound configuration for PK was found to be the most mechanically stable compared with the traditional method and mushroom, zig-zag, and Christmas tree configurations.
Sutureless anterior lamellar keratoplasty
Yoo et al. (Ophthalmology 2008;115(8):1303-7) reported the technique of FS laser-assisted sutureless anterior lamellar keratoplasty for anterior corneal pathology with good results.
Buzzonetti et al. (J Refract Surg. 2010;10:1-6) reported that a combination of FS laser lamellar dissection with the big-bubble technique can improve the standardization of DALK.
Chan et al. (Cornea 2010;29(3):290-5) reported that the use of the FS laser to perform corneal cuts in a mushroom configuration for DALK is feasible. The mechanical stability and wound healing advantages for stepped corneal wounds should be considered in lamellar surgery.
Farid et al. (J Cataract Refract Surg. 2009;35(5):809-13) described a variation of big-bubble DALK technique using the FS laser zig-zag incision. This technique allowed precise depth visualization for air-needle placement in the posterior stroma based on the lamellar and posterior laser cuts, thus minimizing the risk for perforation of DM. The matching donor and host tissue zig-zag cut allows more precise tissue apposition and greater surface area for healing.
Cheng et al. (Transplantation 2009;88(11):1294-302) reported that FS laser-assisted endothelial keratoplasty (FLEK) effectively reduces postoperative astigmatism. However, VA is lower as compared with conventional PK, and there is a high level of endothelial cell loss.
Mehta et al. (J Cataract Refract Surg. 2008;34(11):1970-5) evaluated the accuracy of the thickness and diameter of corneal disks obtained with FS laser for DSEK. The mean deviation from the attempted thickness was 15 ± 14 μ. The FS laser produced posterior stromal ablations that were accurate in depth of ablation and circularity.
Kumar et al. (Ophthalmology 2010;117(6):1228-35) determined the refractive predictability, stability, efficacy, and complication rate of FS laser-enabled astigmatic keratomy (AK) for post-keratoplasty astigmatism. The UCVA and BCVA improved significantly and the value of absolute astigmatism reduced from 7.46 ± 2.70 D to 4.77 ± 3.29 D postoperatively (P = 0.0001).
Fibrin Glue in Corneal Surgery
Sutureless full-thickness patch graft
Gupta et al. (Cornea 2010 May 26) described an innovative technique to seal large paracentral corneal melts with a full-thickness patch graft punched using a dermatological trephine and secured with the fibrin-aprotinin biological tissue adhesive, supplanting the need for sutures. Successful tectonic support with postoperative BCVA of 6/24 was achieved in both cases.
Bahar et al. (Cornea 2007;26(10):1235-8) observed that the use of fibrin glue in TH-PK was found to be more mechanically stable than traditional sutures.
Duarte et al. (Cornea. 2007;26(9):1127-8) reported a case where fibrin glue was applied with a modified approach to secure the graft to the host bed in lamellar keratoplasty.
Deep anterior lamellar keratoplasty
Narendran et al. (Cont Lens Anterior Eye. 2007;30(3):207-9) described a case where DALK was performed successfully using overlay sutures and fibrin glue alone, without the need to directly suture the corneal button and then a bandage contact lens was inserted.
Lamellar keratoplasty and sclera patch adhesion
Kaufman et al. (Ophthalmology 2003;110(11):2168-72) opined that fibrin adhesive provided satisfactory attachment without sutures for lamellar keratoplasty and amniotic patching.
Jacob et al. (Eye Contact Lens. 2010;36(2):130-6) reported a technique using a new biosynthetic graft to treat diffuse anterior staphyloma and cataractous lens with compromised zonules. At 6 months, the outcome was anatomically and cosmetically satisfactory.