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Modified Femtosecond Laser–Assisted Sutureless Anterior Lamellar Keratoplasty
Gustavo Bonfadini, MD,*†
Hamilton Moreira, MD, PhD,‡§ Albert S. Jun, MD, PhD,* Mauro Campos, MD, PhD,† Eun Chul Kim, MD, PhD,*¶ Eduardo Arana, MD,‡ Márcio Zapparoli, MD,‡Jurandir M. Ribas Filho, MD, PhD,§ and Peter J. McDonnell, MD*
Abstract: A variation of the femtosecond laser–assisted sutureless anterior lamellar keratoplasty technique using a femtosecond laser incision for surgical management of anterior corneal disease is described. Six patients with corneal scars were treated with the laser to create a horizontal lamellar bed interface in the cornea of the donor and recipient eyes, with a manual partial-thickness vertical trephination to complete the excisions. This technique allows matching of donor and host tissue dimensions with precise tissue apposition and greater surface area for healing. No intra- operative adverse events were observed. One patient developed epithelial ingrowth, requiring a successful surgical intervention.
Key Words: femtosecond anterior lamellar keratoplasty, femtosec- ond laser–assisted sutureless anterior lamellar keratoplasty, lamellar keratoplasty, femtosecond laser, corneal transplant.
(Cornea 2013;32:533–537)
Lamellar keratoplasty (LK) is a surgical technique used to treat corneal pathologies affecting the corneal stroma. It is an extraocular procedure, and it provides improved wound strength postoperatively and rapid visual rehabilitation with minimal risk of corneal allograft rejection and other long-term complications compared with conventional full thickness corneal transplantation.1
Lamellar dissection of the stroma can be performed by a manual technique using a variety of instruments, including lamellar knives and dissectors. Traditionally, manual dissection techniques have resulted in suboptimal visual outcomes because of interface haze and scarring, and the acceptance of this technique has therefore been limited.
In recent years, the femtosecond laser has been used successfully in a variety of corneal procedures, including the preparation of laser in situ keratomileusis (LASIK) flaps, the creation of channels for intracorneal rings, and the preparation of donor and host tissue in anterior lamellar keratoplasty (ALK).2–5 This last application is ideally suited for ALK. A newer approach to anterior corneal disease has been the use of the 30-kHz IntraLase FS laser (AMO, Irvine, CA) to assist in sutureless ALK (FALK), which was first described in 2008 by Yoo et al.4,5
Our report describes the use of a different laser (Ziemer Ophthalmic Systems AG, Port, Switzerland) to perform FALK in patients with anterior corneal scarring. This report also describes the use of this technique with 2 different dissection depths: midstromal (>250m of posterior residual corneal bed thickness) and pre-Descemet (approximately 50m of posterior residual corneal bed thickness).
SURGICAL TECHNIQUE
The surgical procedures were performed at Hospital de Olhos do Paraná, Curitiba, Brazil, and approved by the ethics committee. All the tenets of Declaration of Helsinki were followed. Six consecutive patients (4 men, 2 women) aged 41 to 67 years with anterior corneal scars were enrolled for the series. Written informed consent was obtained in all cases.
All procedures were performed under topical anesthesia. Anterior segment optical coherence tomography (RTVue-100; Optovue, Fremont, CA) was used preoperatively in all patients to measure the depth of the corneal opacity and the central and peripheral thicknesses of the recipient cornea (Fig. 1).
Visual loss from acquired corneal opacifications can be because of irregular astigmatism and/or the corneal opacity itself. To rule out irregular astigmatism as a cause of visual loss, a rigid gas-permeable contact lens refraction was performed before recommending LK. Corneal opacity contributed significantly to the loss of visual acuity in all cases.
The 6 patients (Tables 1 and 2) underwent treatment with a 1000-kHz FEMTO LDV laser (Ziemer Ophthalmic Systems AG), creating a horizontal lamellar bed interface in the cornea of the donor and recipient eyes. No sutures were used in all 6 FALK procedures of the study. Patients 1, 2, and 3 were treated with the laser programmed to leave at least 250m of posterior residual corneal bed thickness. Patients 4, 5, and 6 underwent FALK with the laser programmed to leave at least 50m posterior residual corneal bed thickness overlying the thinnest part of the cornea (Tables 1 and 2). Criteria for deeper excisions included: (1) increased depth of opacity (Table 2) and (2) absence of patient or family history of corneal ectasia.
To create the donor grafts, corneoscleral donor tissue was removed from storage solution (Optisol-GS; Bausch & Lomb Surgical, Irvine, CA) and mounted on an artifi cial anterior chamber (LDV; Ziemer Ophthalmic Systems AG). The femtosecond laser keratoplasty software was programmed as follows: donor lenticule thickness of 280 to 500m, applanation 8.5 to 9.5 mm, vacuum value 750 mbar, total cut time for patients ranged from 55 to 76 seconds, total cut time in donor tissue ranged from 36 to 45 seconds, applanation time 57 to 63 seconds in patients, and applanation time ranged from 57 to 63 seconds in the donors. For patients, we programmed 2.5 to 3.5 mm/s velocity of the stroma (adjusted according to the severity of the corneal scar) and 30 mm/s velocity of the border. For donors, we used 4.0 mm/s velocity of the stroma and 30 mm/s velocity of the border.
Depending on the donor tissue quality and edema, 10% to 20% additional thickness was added to the donor lenticule to adjust for donor tissue swelling. Vertical incision was made in the donor and recipient tissues using a manually held 8.0-mm trephine blade (Katena Products, Denville, NJ). The host corneal button and the donor graft were gently separated from the underlying stroma using a Sinskey hook and a spatula, and the donor graft was immediately placed on the recipient residual corneal stromal bed. The vertical incision was dried with methylcellulose sponges and the flap was checked for adhesion by depressing the peripheral host cornea and ensuring that the resulting indentation radiated into the lenticule (similar to checking for flap adhesion after LASIK with the striae test). A bandage contact lens was fitted over the cornea and left in place for 1 week.
Patients were placed on a topical moxifloxacin hydrochloride 0.5% ophthalmic solution (Vigamox; Alcon Laboratories, Fort Worth, TX) 4 times daily for 1 week. Topical prednisolone acetate 1.0% eye drops (Pred-Forte; Allergan, Irvine, CA) were initially used 4 times daily and slowly tapered over 4 months. Additionally, we used 0.1% nepafenac ophthalmic solution (Nevanac; Alcon Laboratories) 4 times daily for 1 week. All patients were treated with artificial tears (Systane Ultra; Alcon Laboratories) after surgery to ensure adequate lubrication of the ocular surface. The follow-up visits for the patients were 1, 2, and 4 weeks, 2, 4, and 6 months, and 1 year after FALK (Fig. 2).
RESULTS
The characteristics of patients included in the study are summarized in Table 1. In this case series, no intraoperative complications occurred. At 1 week postoperatively, all eyes were white and quiet, the corneas were clear and reepithelial- ized, and intraocular pressures were normal. Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) improved in all patients compared with preoperative visual acuity, and all the eyes had clear grafts at the 1-year follow-up (Video, Supplemental Digital Content, http://links.lww.com/ICO/A81 and Table 2). The mean difference between preoperative and postoperative UCVAs was a gain of 4.3 lines (range, 3–8 lines). BCVAs were improved in all eyes compared with preoperative levels. The mean difference between preoperative and postoperative BCVAs was a gain of 8.0 lines (range, 4–13 lines).
No intraoperative complications, graft rejection, or infection were found in this series of patients at 1-year follow-up. Patient 3 was noted to have epithelial ingrowth in the graft–host interface 2 weeks after FALK (Fig. 3). The epithelial ingrowth was debrided surgically, and the graft was sutured into position. Topical steroids were tapered slowly until removal of the last suture 11 months after the original procedure. At 1-year follow-up, no recurrence of the epithelial ingrowth was noted. At 1-year follow-up, 5 of 6 patients showed regular astigmatism, and 1 patient showed irregular astigmatism (patient 3, Table 2). None of the patients showed topographic or clinical evidence of ectasia.
The characteristics of patients included in the study are summarized in Table 1. In this case series, no intraoperative complications occurred. At 1 week postoperatively, all eyes were white and quiet, the corneas were clear and reepithelial- ized, and intraocular pressures were normal. Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) improved in all patients compared with preoperative visual acuity, and all the eyes had clear grafts at the 1-year follow-up (Video, Supplemental Digital Content, http://links.lww.com/ICO/A81 and Table 2). The mean difference between preoperative and postoperative UCVAs was a gain of 4.3 lines (range, 3–8 lines). BCVAs were improved in all eyes compared with preoperative levels. The mean difference between preoperative and postoperative BCVAs was a gain of 8.0 lines (range, 4–13 lines).
No intraoperative complications, graft rejection, or infection were found in this series of patients at 1-year follow-up. Patient 3 was noted to have epithelial ingrowth in the graft–host interface 2 weeks after FALK (Fig. 3). The epithelial ingrowth was debrided surgically, and the graft was sutured into position. Topical steroids were tapered slowly until removal of the last suture 11 months after the original procedure. At 1-year follow-up, no recurrence of the epithelial ingrowth was noted. At 1-year follow-up, 5 of 6 patients showed regular astigmatism, and 1 patient showed irregular astigmatism (patient 3, Table 2). None of the patients showed topographic or clinical evidence of ectasia.
DISCUSSION
The use of the femtosecond laser to produce corneal incisions has improved the precision of lamellar corneal transplantation surgery. Although mechanical microkeratomes have been used for this purpose, femtosecond flaps have stronger adhesion than microkeratome flaps,6,7 and this may provide additional graft stability during the early postoperative period. The fit between donor and recipient lenticules in our series was highly reproducible, allowing all patients to have sutureless ALK completed without difficulty.
Our series is unique, to our knowledge, in that we had 2 depths of femtosecond laser lamellar excision. Patients 1, 2, and 3 were left with at least 250 m of posterior residual corneal bed thickness, and patients 4, 5, and 6 were left with 50m of posterior residual corneal bed thickness based on anterior segment optical coherence tomography measurements on the recipient eye (Table 2).
Our rationale for not suturing the grafts for the deeper FALK dissections in patients 4, 5, and 6 included: (1) avoidance of suture-related complications, (2) relative stability of graft placement in femtosecond laser–prepared tissue as in a femtosecond laser–prepared LASIK flap and in LK reported by Yoo et al,4,5 and (3) reasonable, though not full, tectonic stability of a 50mposterior stromal layer. Although point 3 may be particularly debatable, patients with areas of chronic, severe corneal thinning with comparable levels of stromal support, that is, approximately 100m total corneal thickness including overlying intact epithelium, can be managed conservatively without surgery. Ectasia is a substantial concern in LK as removal of tissue undoubtedly reduces mechanical strength of the cornea. We did not observe any cases of ectasia in our series at 1-year follow-up. However, it is clear that ectasia can occur later than 1 year after surgery, and thus, we cannot rule out this long-term possibility in our patients. Posterior stromal bed thickness of 250m is an acknowledged guideline to minimize risk of ectasia in LASIK. However, before the acceptance of this value, LASIK cases were performed, which resulted in less posterior stromal bed thickness, and ectasia remains relatively rare even among these cases. In addition, deep ALK is routinely performed, even in naturally occurring ectatic cornea, for example, keratoconus, with less than 50m posterior stromal bed thickness, and ectasia in these grafts is also rare. Although it has been proposed that the healing response along graft sutures provides the tectonic strength needed to prevent ectasia in these grafts,8 this topic has not been studied extensively. Thus, long-term follow-up of a larger number of patients in future studies could provide more infor- mation about the likelihood of ectasia in patients undergoing FALK and whether sutures can reduce this risk.
Overall, we feel that this pilot series shows encouraging results for our described technique. It also suggests a variety of issues for further evaluation. From a safety perspective, the long-term risk of ectasia should be determined. As well, the use of sutures, either for potentially increased tectonic strength in deeper dissections as suggested by Abdelkader et al8 or in preventing complications from pathologic epithelial healing as in our diabetic patient 3, deserves study. However, the potential to avoid suturing these grafts has advantages, including earlier visual rehabilitation and potentially less induced astigmatism.4,5
FALK clearly has advantages over traditional penetrating keratoplasty (PK) or LK techniques. These include the ability to use topical anesthesia and a much faster procedure. Our results indicate that in some cases sutures are not required, although this will require further validation. In addition, compared with PK, the procedure is extraocular with no concern for endothelial graft rejection. Compared with previous reports of FALK, we feel that our technique using deeper dissections has an advantage in allowing better rehabilitation of deeper scars and avoiding the need for additional procedures, such as phototherapeutic keratectomy described by Yoo et al.4,5
As mentioned above, although ectasia is a concern in these cases, suturing may provide additional tectonic support, and even still FALK may be worth considering compared with the alternative that would likely be manual/big bubble deep ALK or PK. In summary, 1-year follow-up results of our “modified” FALK technique indicate that the method is effective in the removal of corneal scars with substantial improvement in UCVA and BCVA. Although our follow-up time is limited, we did not observe any cases of corneal ectasia even for deeper dissections. We did observe one postoperative complication of epithelial ingrowth, which resolved with further treatment. These preliminary results suggest that the use of a manual partial-thickness vertical trephination in combination with femtosecond laser may be an improvement over conventional ALK and PK. Larger studies will be needed to validate our findings and to further address questions, such the need for sutures and long-term outcomes and complications.
REFERENCES
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- Shousha MA, Yoo SH, Kymionis GD, et al. Long-term results of femtosecond laser-assisted sutureless anterior lamellar keratoplasty. Ophthalmology. 2011;118:315–323.
- Knorz MC, Vossmerbaeumer U. Comparison of flap adhesion strength using the Amadeus microkeratome and the IntraLase iFS femtosecond laser in rabbits. J Refract Surg. 2008;24:875–878.
- Kim JY, Kim MJ, Kim TI. A femtosecond laser creates a stronger flap than a mechanical microkeratome. Invest Ophthalmol Vis Sci. 2006;47: 599–604.
- Abdelkader A, Esquenazi S, Shihadeh W, et al. Healing process at the flap edge in its influence in the development of corneal ectasia after LASIK. Curr Eye Res. 2006;31:903–908.
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