|Year : 2016 | Volume
| Issue : 3 | Page : 587-592
The visual outcome and complications in deep anterior lamellar keratoplasty for keratoconus
Saber H El Sayed1, Mahmoud M Ismail2, Motaz F El Sawy1, Ahmed A El Hagaa1, Mohammed S Abdel Aziz1
1 Department of Ophthalmology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Ophthalmology, Faculty of Medicine, Al Azhar University, Nasser City, Egypt
|Date of Submission||24-Oct-2014|
|Date of Acceptance||10-Nov-2014|
|Date of Web Publication||23-Jan-2017|
Mohammed S Abdel Aziz
6th Maxiem St, Sheibin El Kom, Menoufia Governorate, 32511
Source of Support: None, Conflict of Interest: None
The aim of this study was to evaluate visual outcomes and complications of deep anterior lamellar keratoplasty (DALK) using the big-bubble technique in patients with keratoconus.
Keratoconus is a bilateral noninflammatory corneal thinning disorder leading to protrusion, distortion, and scarring of the cornea. Treatment options are glasses, hard contact lenses, cross-linking, intracorneal segment insertion, refractive surgery, or keratoplasty. DALK can be a better choice to manage cases of moderate and some cases of severe keratoconus without deep scarring and severe thinning.
Participants and methods
This interventional study was carried out on 47 eyes of 46 patients who presented with moderate to advanced keratoconus for DALK from December 2012 to June 2014 with a mean follow-up of 12 months. The best spectacle-corrected visual acuity, the refractive status, and intraoperative and postoperative complications were evaluated.
Thirty-seven procedures (78.7%) were completed with big-bubble formation, and six patients (12.8%) required manual intrastromal dissection. Intraoperative microperforations occurred in four cases (8.5%). The mean preoperative uncorrected visual acuity was 0.036 ± 0.017 and the final best spectacle-corrected visual acuity at 1 year had a mean value of 0.38 (P < 0.001). The postoperative mean spherical equivalent refractive error and astigmatism were − 4.9 ± 2.6 and − 3.9 ± 1.6 D, respectively. Main complications encountered included loosening of the stitches in 11 cases (23.4%), vascularization of the stitches in three cases (6.4%), double anterior chamber in two cases (4.3%), Urrets-Zavalia syndrome in one case (2.1%), stromal rejection in one case (2.1%), and suture abscess in one case (2.1%).
DALK using the big-bubble technique appears to be a safe and effective procedure in patients with keratoconus. Postoperative myopic astigmatism is observed in most of the cases.
Keywords: big-bubble technique; deep anterior lamellar keratoplasty; keratoconus
|How to cite this article:|
El Sayed SH, Ismail MM, El Sawy MF, El Hagaa AA, Abdel Aziz MS. The visual outcome and complications in deep anterior lamellar keratoplasty for keratoconus. Menoufia Med J 2016;29:587-92
|How to cite this URL:|
El Sayed SH, Ismail MM, El Sawy MF, El Hagaa AA, Abdel Aziz MS. The visual outcome and complications in deep anterior lamellar keratoplasty for keratoconus. Menoufia Med J [serial online] 2016 [cited 2020 Mar 29];29:587-92. Available from: http://www.mmj.eg.net/text.asp?2016/29/3/587/198718
| Introduction|| |
Deep anterior lamellar keratoplasty (DALK) is an alternative procedure to penetrating keratoplasty (PKP) for corneal pathologies not affecting the endothelium and Descemet's membrane (DM)  . Advantages of DALK over PKP include the elimination of endothelial graft rejection, reduction of graft failure, better preservation of the globe integrity in case of blunt trauma  , faster visual rehabilitation, and a longer graft survival due to lower rates of endothelial cell loss  . However, DALK is a time-consuming and technically demanding procedure. In addition, light scattering at the host-donor interface is a potential cause of suboptimal vision after DALK  . Compared with manual dissection, the injection of air  or the viscoelastic material  into the deep corneal stroma in DALK makes the separation of DM from the stroma much easier and leaves a smoother and more uniform host-donor interface, thereby reducing complications encountered with conventional lamellar keratoplasty such as interface opacity  .
In 2002, Anwar and Teichmann  proposed a technique, which they called the big-bubble technique, in which air is injected into the deep stroma with the aim of inducing separation by cleavage between the posterior stroma and the DM, allowing the surgeon to gain safe and direct access to this plane, with the advantages of shortening the surgical time, reducing the risk of perforation, and exposing a smooth surface of excellent optical quality.
In this study, we report the clinical outcomes of the DALK big-bubble technique in unselected consecutive patients with keratoconus.
| Participants and methods|| |
This was a noncomparative interventional case study series conducted in the Department of Ophthalmology, Menoufia University Hospital, and the Nour El Hayat eye hospital during the period from December 2012 to June 2014.
Forty-six consecutive patients (47 eyes) with keratoconus ([Figure 1]) were included in a prospective clinical study that aimed to evaluate clinical outcomes of DALK using the big-bubble technique. Inclusion criteria were patients who presented with keratoconus with a keratometric (k) reading of more than 55 D (with or without superficial opacity).
After ophthalmologic examination, the following patients were excluded from the study: DM rupture with deep corneal opacification, amblyopic eyes, the presence of cataract, the presence of glaucoma, and patients with posterior segment pathology, for example, retinal detachment.
All patients involved in the study were fully informed about the surgical technique and its possible implications. A formal consent was obtained; the protocol was approved by the Ethical Committee of the Faculty of Medicine, Menoufia University.
Preoperative eye examinations included the Snellen uncorrected visual acuity (UCVA) and the best spectacle-corrected visual acuity (BSCVA), slit-lamp examination, tonometry, fundus examination, manifest refraction, and corneal topography. The visual acuity and refraction were retested at 1, 3, 6, and 12 months after the surgery. UCVA and BSCVA were recorded as the decimal equivalent of the Snellen chart ratio. Postoperative corneal topography was performed in some cases for the management of high astigmatism. Intraoperative and postoperative complications was recorded and analyzed.
All patients were operated on by one anterior segment surgeon (Mahmoud M. Ismail) under local anesthesia using the big-bubble technique as described by Anwar and Teichmann  . The diameter of trephination was chosen according to the size of the cone and the vertical corneal diameter.
After trephination to ∼80% of the corneal thickness with a Hessburg-Barron suction trephine (Katena, Denville, New Jersey, USA), a 27-G needle, attached to a 3-ml syringe, bent at 60° (bevel facing downward) was inserted into the stroma up to the center of the cornea. Air was injected gently into the midstroma until a big bubble was formed extending to the border of trephination ([Figure 2]). If the big bubble was not formed after the first attempt, the injection was repeated until the big bubble was formed or failed.
After big-bubble formation, debulking of the anterior two-third of the corneal stroma was performed with a crescent blade (Alcon Laboratories, Forth Worth, Texas, USA). Thereafter, a peripheral paracentesis was performed to reduce the intraocular pressure; the bubble was punctured with a 15° slit-knife (Alcon Laboratories) to allow the escape of the air and the collapse of the bubble. The viscoelastic material was injected to keep DM away from manipulations. Vannas scissors were used to divide the rest of the corneal stroma into four quadrants, and each quadrant was excised completely using left and right transplantation scissors, taking care not to leave any posterior lip. The viscoelastic material was then completely washed out before proceeding to graft suturing.
The surgeon always aimed to achieve a big bubble. In cases where this was not accomplished after more than one attempt, a layer-by-layer manual stromal dissection was performed with a blunt-tipped wire spatula. The surgeon aimed to expose the DM or a plane closest possible to the DM ([Figure 3]).
The donor cornea was punched from the endothelial side using the Barron punch (Katena). The donor was oversized by 0.25 mm. The donor DM and the endothelium were stripped off gently with a dry cellulose sponge or forceps ([Figure 4]). The donor cornea was initially fixed with 4 cardinal 10-0 nylon sutures at 3, 6, 9, and 12 clock-hour positions.
|Figure 4: Preparation of the donor cornea with the stripping of Descemet's membrane.|
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The button was sutured in place using eight interrupted sutures and one continuous 10-0 nylon suture. At the end of the surgery, the air bubble was injected into the anterior chamber with special attention to the intraocular pressure ([Figure 5]).
Postoperative medication included gatifloxacin and prednisolone acetate 1% five times a day for a month and tapered over a period of 12 weeks, and artificial tears instilled six times a day for 3 months.
Statistical analysis was carried out by Windows SPSS software, version 11.0 (SPSS Inc., Chicago, Illinois, USA). As the group distributions were non-Gaussian, the UCVA and BSCVA ( Snellen fraction More Details), the manifest refraction (cylinder and SE), and corneal topography (Sim K astigmatism) were compared using the Mann-Whitney test. Values of P less than 0.05 were considered significant.
| Results|| |
During the time covered by this study, 47 eyes (46 patients) with keratoconus underwent the DALK big-bubble technique. Of these, 30 were men (65.2%) and 16 were women (34.8%). The mean age at the time of surgery was 25.7 ± 6.9 (12-44) years. The preoperative mean keratometry was 57.9 ± 16.1 (55.2-79) D.
The mean preoperative UCVA was 0.036 ± 0.017 (0.01-0.07); the Snellen chart ratio increased to a BCVA of 0.38 ± 0.1 at the final examination (P < 0.001) ([Table 1]).
|Table 1 Preoperative and postoperative visual acuity of deep anterior lamellar keratoplasty in patients with keratoconus |
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There was a statistically significant difference between the first month postoperatively and the preoperative values, as well as between the third and the first months, postoperatively. No statistically significant difference occurred between the third and the sixth months. Yet a significant change was noticed between the sixth month and 1 year postoperatively.
A bare DM was achieved successfully in 37 (78.7%) eyes, but in six (12.8%) eyes, it was necessary to perform a layer-by-layer manual stromal dissection because of the lack of big-bubble formation after several attempts. Microperforation of DM occurred in four cases out of 47 (8.5%); the procedure continued with the stripping of the residual stroma away from the area of rupture with careful manipulation to avoid the extension of the DM break, and then tight suturing of the donor cornea to the DM with air injection into the anterior chamber.
A clear graft-host interface was observed postoperatively in 38 (80.9%) patients ([Figure 6]). Postoperative complications are summarized in [Table 2]; Urrets-Zavalia syndrome occurred in one case on the second day postoperatively: the patient presented with a dilated irreactive pupil, a high intraocular pressure, and later anterior subcapsular lenticular opacity ([Figure 7]). The patient was managed by topical antiglaucoma medications and the condition resolved in 2 weeks, leaving a residual anterior subcapsular cataract that was visually insignificant.
|Figure 6: Postoperative deep anterior lamellar keratoplasty (DALK) (1 week).|
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A double anterior chamber occurred in two cases after a ruptured DM: management included air injection into the Anterior chamber. Stromal rejection was noticed in one case at the sixth month with opacification of the donor tissue due to vascularization of the stitches ([Figure 8]), and this lead to a decrease in the visual acuity: management included removal of the stitches with topical and systemic steroids.
Infective keratitis related to corneal stitches was a catastrophic complication that occurred in one case at the second month postoperatively and was managed by immediate removal of all stitches and aggressive topical fortified antibiotics; the infection resolved in 3 weeks, leaving a residual corneal scar.
Selective stitch removal was performed for the management of astigmatism or complications such as stitch vascularization or lose stitches; the mean timing was 2.8 months.
However, continuous stitch removal was also performed for the management of spherical errors or complications; the mean timing was 6.4 months.
The final refraction after suture management was calculated regarding the spherical equivalent and astigmatism. The mean residual spherical equivalent was − 4.9 D with a myopic shift. The mean astigmatism postoperatively was − 3.9 D with a range from − 2.5 to − 8 cylinder diopters.
| Discussion|| |
In this prospective study, we investigated the clinical outcomes of the DALK big-bubble technique on unselected consecutive patients with moderate to advanced keratoconus.
Our study showed that the mean preoperative unaided visual acuity using the decimal equivalent of the Snellen chart ratio was 0.036 ± 0.017, whereas the mean postoperative BSCVA was 0.08, 0.18, 0.19, and 0.38 at the first, the third, and the sixth months and at 1 year postoperatively, respectively.
Fontana et al.  showed that mean preoperative unaided visual acuity was 0.042 ± 0.046, whereas the mean postoperative BSCVA was 0.432, 0.564, 0.651, and 0.736. These results were similar to our results, with the higher levels of final BSCVA probably related to the technique of suturing, donor-to-host disparity, and a larger sample size.
Bahar et al.  reviewed medical records of 17 consecutive eyes with keratoconus that underwent DALK; the mean preoperative visual acuity was 0.078 ± 0.1 and the final BSCVA was 0.38 ± 0.8. In the research conducted by Javadi et al.  where 104 eyes of 99 patients with moderate to advanced keratoconus underwent DALK, the mean preoperative UCVA was 0.04 ± 0.3, which was improved to 0.5 ± 0.2 at the final follow-up.
We were able to form the big bubble successfully in 37 (78.7%) eyes, which is consistent with the success rate of 80-90% reported by Anwar and Teichmann, but better than that reported by Fogla and Padmanabham  and Fontana et al.  (69.2 and 64%, respectively).
Although various techniques to facilitate safe and efficient stromal dissection have been reported, perforation of the DM remains relatively common (0-50.0%), even among experienced surgeons. Although some reports have suggested that DM perforations may result in undesirable consequences, others have suggested that this event does not influence the outcome significantly  .
In our study, microperforation of DM occurred in four cases out of 47 (8.5%). Incomplete air bubble formation occurred in six cases out of 47 (12.8%), in which debulking of the superficial stroma took place, and mechanical dissection of the residual stromal fibers attached to the DM was performed with a blunt spatula and the viscoelastic material. Double anterior chamber occurred in two cases after a ruptured DM, and the management included air injection into the AC.
In a study conducted by Fontana et al.,  same-size donor graft was used in all patients with the purpose of reducing the postoperative myopia reported after PKP that uses an oversized donor button. This purpose may be sought with reasonable safety in lamellar keratoplasty because the anterior chamber is closed and there is no risk of wound leak. The postoperative spherical equivalent and astigmatism of the DALK big-bubble technique in patients with keratoconus were −1.56 ± 3.22 (+3.6 to −7.46) and 3.35 ± 1.76 (1-7.13), respectively.
In our study, the final refraction after suture management was calculated and showed a mean residual spherical equivalent of −4.9 ± 2.6 D (+0.5 to −10) with myopic shift; this is possibly because a difference of 0.25 mm between the donor and the host corneal diameters is used; the mean astigmatism postoperatively was − 3.9 ± 1.6 D (−2.5 to − 8 cylinder diopters); the results of this study compare favorably with the refractive outcomes of other studies that showed equivalent or greater myopic refraction after DALK ,, .
Regarding postoperative complications, our study shows the following complications in a decreasing frequency: loosening of the stitches in 11 cases (23.4%), vascularization of the stitches in three cases (6.4%), double anterior chamber in two cases (4.3%), Urrets-Zavalia syndrome in one case (2.1%), stromal rejection in one case (2.1%), and suture abscess in one case (2.1%).
Huang et al.  reported that in the 101 eyes in which DALK was conducted successfully for different indications, loosening of the sutures was recorded in 24 eyes (23.8%) at 4-7 months. Epithelial rejection showing an epithelial rejected line was observed in two eyes at 6 and 8 months after surgery, respectively. Stromal rejection associated with decreased vision occurred in five eyes between 6 and 15 months, characterized by stromal haze and edema. Except for one graft performed on a host with chemical burns, which failed at 7 months as a result of irreversible stromal rejection, others responded well to intensive topical corticosteroids, and grafts cleared after 2-3 weeks of treatment.
| Conclusion|| |
DALK is an appropriate alternative to PKP in patients with keratoconus; it eliminates the risk of endothelial graft rejection, preserves globe integrity, and provides acceptable visual function. Postoperative myopic astigmatism is noticed in most cases.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2]