Use of deep anterior lamellar keratoplasty (DALK) for keratoconus: indications, techniques and outcomes

Comparison of visual outcomes, keratometric parameters and biomechanical profiles between deep anterior lamellar keratoplasty with big-bubble technique vs. Melles technique for keratoconus: a retrospective study

OBJECTIVE

Comparing results of two different DALK surgery techniques (big bubble vs. Melles) in patients with advanced keratoconus.

DESIGN

a retrospective comparative clinical study.

PARTICIPANTS

This study conducted on 72 eyes of 72 participants.

INTRODUCTION

This study designed to compare the results of two different DALK surgery techniques (big bubble vs. Melles) in patients with advanced keratoconus.

METHOD

Thirty-seven eyes were treated using the big bubble DALK method, while 35 eyes were treated using the Melles approach. Uncorrected visual acuity (UCVA), best corrected spectacle visual acuity (BCSVA), manifest refraction, keratometric characteristics, contrast sensitivity, corneal aberrations, corneal biomechanical characteristics, and endothelial cell profile are the outcome measurements.

RESULTS

Mean UCVA in big bubble group was 0.61 ± 25 LogMAR and in Melles group was 0.89 ± 0.41 LogMAR (p-value 0.043). Mean BCSVA in big bubble group (0.18 ± 0.12 Log MAR) was significantly better than Melles group (0.35 ± 0.16 Log MAR). Mean of sphere and cylinder refraction showed no significant difference between two groups. Comparing the endothelial cell profile, corneal aberrations, corneal biomechanical properties and keratometry had no significantdifferences. Contrast sensitivity reported as modulation transfer function (MTF) showed higher values in big bubble group and differences with Melles group weresignificant. Results of point spread function (PSF) in big bubble group had superiority to Melles group with considerable statistical P value of 0.023.

CONCLUSION

When opposed to the Melles approach, the big bubble technique generates a smooth interface with less stromal residue, which results in higher visual quality and contrast sensitivity.

Case series of staged lamellar corneal grafting with thin manual Descemet's stripping endothelial keratoplasty, followed by manual deep anterior lamellar keratoplasty, as an alternative to penetrating keratoplasty

The purpose of this report is to present the outcomes of Descemet's stripping endothelial keratoplasty (DSEK), followed by deep anterior lamellar keratoplasty (DALK), as an alternative to penetrating keratoplasty (PKP) for different indications. Patients in this retrospective case series underwent manual DSEK, followed by manual DALK, for tectonic and/or visual reasons. It includes three cases that underwent DSEK followed by DALK as an alternative to PKP for the following conditions: failed PKP and stromal scarring, aphakic bullous keratopathy and herpetic stromal scarring, and herpetic corneal perforation. All cases had successful anatomical repair with visual improvement. Many corneal conditions involving endothelium and stroma have been traditionally managed with PKP. However, in certain settings with high risk of complications, this might not be an appropriate option. Therefore, for these cases, we propose management with DSEK followed by DALK as an alternative approach in a 'closed anterior chamber' fashion, which can reduce the risk of significant, sometimes irreversible, complications.

A new collagen scaffold for the improvement of corneal biomechanical properties in a rabbit model

Although collagen based materials are widely used in corneal tissue engineering with promising results. The usage of such materials for the improvement of corneal biomechanical properties is still unclear. In this study, we aimed to investigate a new Viscoll collagen-based membrane for the improvement of corneal biomechanical characteristics.The right eyes of 15 Chinchilla rabbits were implanted with the membrane via an intrastromal pocket, with the contralateral intact eyes as controls. At 7, 30, 90, and 180 days post-surgery, the rabbits underwent anterior segment optical coherence topography, clinical examination, and slit-lamp microscopy. Additionally, the corneal samples also underwent histological examination followed by the assessment of the biomechanical characteristics of four treated and non-treated corneas at 30, 90, and 180 days, including keratometry at 180 days, post operation. Data are presented as means ± confidence intervals with a 95% confidence level. All the operated corneas retained their transparency throughout the study. Implantation approximately doubled the central corneal thickness. Corneas became stronger by approximately 87% between 1 and 6 months after surgery (maximum fracture load, 13.3 ± 0.8 and 24.9 ± 1.4 N, respectively), and their elasticity increased by approximately 27% over the same time frame (maximum slope of the elastic region of the stress-strain curve, 11.5 ± 0.2 and 14.6 ± 1.4 N/mm respectively). We have thus proposed a new method to increase corneal thickness and strengthen the corneal tissues while preserving their transparency and demonstrated its safety and efficacy in a rabbit model over 6 months. This may be a suitable alternative to the existing corneal collagen crosslinking procedure.

[Methods of surgical treatment of keratectasia and analysis of postsurgical quality of vision]

Keratectasias are non-inflammatory dystrophic diseases of the cornea characterized by progressive bilateral thinning of the cornea that lead to deterioration in the quantitative and qualitative characteristics of vision reducing patient's quality of life. The changes can be asymmetrical and destructive. A number of surgeries have been proposed to reduce the negative effects of keratectasia including penetrating keratoplasty and its modifications, implantation of corneal ring segments, corneal cross-linking - alone and in combination with other methods, intrastromal keratoplasty. These methods can improve visual acuity to a certain degree and help slow the progression of keratectasia. This article studies various surgical methods used for treating keratectasia and analyses possible assessment of the quality of vision before and after the treatment.

Clinical outcomes of double continuous suture in femtosecond laser-assisted lamellar keratoplasty for keratoconus

To assess the surgical outcomes in patients who underwent femtosecond laser-assisted lamellar keratoplasty with double continuous suture for keratoconus, 100 patients (102 eyes) with keratoconus in advanced stages undergoing femtosecond laser-assisted lamellar keratoplasty in Shandong Eye Hospital were studied. In the management of keratoconus, 50 patients (52 eyes) received double continuous suture, and 50 patients (50 eyes) underwent interrupted suture. The follow-up duration was 1 year. Best-corrected visual acuity (BCVA), corneal astigmatism, cosmetic outcomes, and surgical complications were measured as outcome indicators. The epithelium healed at 3 ± 2 days and 4 ± 2 days in the double continuous suture group and the interrupted suture groups, respectively (P > 0.05). At 6 months after surgery, the average visual acuity was 20/125 and 20/100 (P > 0.05), and the average BCVA was 20/32 and 20/40 (P > 0.05), respectively. At 1 year after surgery, the average visual acuity was 20/63 and 20/80 (P > 0.05), and the average BCVA was 20/32 and 20/25 (P > 0.05), respectively; the mean curvature was 43.24 ± 5.15 D and 43.31 ± 5.58 D (P > 0.05), the mean astigmatism was 3.21 ± 1.74 D and 5.35 ± 1.37 D (P < 0.05).The looseness of sutures were found in 2 patients and 15 patients in both groups, respectively (P < 0.05). No postoperative infection or immune rejection occurred in either group during the follow-up. Comparing with the interrupted suture, using the continuous suture in femtosecond laser-assisted lamellar keratoplasty for keratoconus markedly limited the looseness of sutures with lesser corneal astigmatism and better visual quality postoperative.

Outcomes of big-bubble deep anterior lamellar keratoplasty for pediatric keratoconus

PURPOSE

To evaluate the outcomes and complications of deep anterior lamellar keratoplasty (DALK) performed for pediatric keratoconus.

METHODS

This retrospective study enrolled 44 consecutive eyes of 39 keratoconus-affected children (≤ 18 years of age). All patients underwent big-bubble DALK from March 2004 to June 2016. The outcome measures included postoperative best spectacle-corrected visual acuity (BSCVA), manifest refraction, keratometry readings, and complications.

RESULTS

The mean participant age was 16.8 ± 1.4 years, and the mean follow-up period was 68.5 ± 39.9 months. Successful big bubble was achieved in 33 eyes (75.0%), while the surgical technique was predescemetic DALK in 11 (25.0%). The mean BSCVA changed from 1.34 ± 0.49 LogMAR preoperatively to 0.24 ± 0.10 LogMAR postoperatively (P < 0.001). The mean keratometry decreased from 59.54 ± 5.17 D preoperatively to 46.23 ± 2.17 D postoperatively (P < 0.001). The complications encountered during the study period were intraoperative Descemet's membrane perforation (n = 5, 11.4%), the Urrets Zavalia syndrome (n = 1, 2.3%), graft epithelial problems (n = 3, 6.8%), subepithelial graft rejection (n = 5, 11.4%), high intraocular pressure (n = 8, 18.2%), and traumatic wound dehiscence (n = 2, 4.6%). Suture-related complications included premature loosening (n = 13, 29.6%), broken sutures (n = 12, 27.3%), suture-tract vascularization (n = 6, 13.6%), suture-associated abscesses (n = 5, 11.4%), and suture cheese wiring (n = 2, 4.6%). A clear graft was found in 40 eyes (90.9%) at the last follow-up examination.

CONCLUSION

This study showed promising results with big-bubble DALK in keratoconus-affected children. A frequent and close follow-up with dedicated parental involvement is essential for the early recognition and management of postoperative complications.

Approaches toward enhancing survival probability following deep anterior lamellar keratoplasty

The greatest advantage of deep anterior lamellar keratoplasty over full-thickness corneal transplantation is the elimination of graft failure caused by endothelial rejection. Despite this advantage, a deep anterior lamellar keratoplasty graft can fail because of several factors, such as complications related to the donor-recipient interface, graft epithelial abnormalities, graft vascularization, stromal graft rejection, and recurrence of herpetic keratitis. Increased deep anterior lamellar keratoplasty graft survival is mainly built upon optimization of the ocular surface to provide a hospitable environment for the graft. Any predisposing factors for graft epithelial abnormalities, corneal neovascularization, and preexisting vernal keratoconjunctivitis should be identified and treated preoperatively. Prompt recognition and appropriate treatment of interface-related complications and stromal graft rejection usually result in good anatomic outcomes, with no detrimental effects on vision.

Effect of Keratoconus Severity on Clinical Outcomes After Deep Anterior Lamellar Keratoplasty

PURPOSE

To evaluate the effect of keratoconus severity on the visual and refractive outcomes and complications after deep anterior lamellar keratoplasty (DALK).

DESIGN

Consecutive interventional case series.

METHODS

This study enrolled 227 keratoconus-affected eyes that underwent DALK. Amsler-Krumeich keratoconus classification was used to categorize the patients: stage II, 47 eyes; stage III, 60 eyes; and stage IV, 120 eyes. The outcome measures, including postoperative best spectacle-corrected visual acuity (BSCVA), spherical equivalent refraction, mean keratometry, keratometric astigmatism, and complications, were analyzed and compared based on keratoconus stage.

RESULTS

The mean patient age was 27.6 ± 8.0 years, and the mean follow-up period was 38.0 ± 19.8 months. No significant differences were observed in postoperative BSCVA (P = .55), spherical equivalent refraction (P = .27), mean keratometry (P = .09), and keratometric astigmatism (P = .14) among the groups. Improvement in BSCVA were significantly greater in stage III and stage IV compared with stage II (P = .04 and P < .001, respectively). The decrease in spherical equivalent was significantly greater in stages III and IV compared with stage II (P = .04 and P = .001, respectively). Mean keratometry decreased to a greater degree in stage IV compared with stages II and III (P < .001 for both comparisons). The study groups were comparable with respect to intraoperative Descemet membrane perforation, the rate of successful big-bubble formation, suture-related complications, and graft rejection.

CONCLUSIONS

DALK is a safe and effective procedure for the treatment of all stages of keratoconus. This technique of corneal transplantation is more effective in eyes with severe keratoconus compared with those with moderate keratoconus.

Effect of Suture Removal on Refraction and Graft Curvature After Deep Anterior Lamellar Keratoplasty in Patients With Keratoconus

PURPOSE

To evaluate the effect of suture removal on refraction and keratometry measurements after deep anterior lamellar keratoplasty (DALK).

METHODS

This retrospective study enrolled 54 keratoconus-affected eyes that underwent DALK. A combined suturing technique consisting of a 16-bite single running and 8-bite interrupted 10-0 nylon sutures was used at the time of keratoplasty. Selective interrupted suture removal was performed in a subgroup of patients to reduce postkeratoplasty astigmatism. In another subgroup, all sutures were removed at a single session. Adjustment of the running suture tension was not performed in any case. The effect of suture removal on refractive outcomes was investigated in the entire study group, and the 2 subgroups were compared.

RESULTS

Mean patient age was 26.6 ± 6.7 years at the time of keratoplasty. The mean interval from surgery to complete suture removal was 17.4 ± 5.9 months. Compared with the pre-suture removal values, there was a significant increase in the magnitude of myopia (-1.12 ± 1.73 D, P = 0.001), refractive astigmatism (-0.89 ± 2.47 D, P = 0.04), mean keratometry (1.39 ± 1.64 D, P = 0.001), and keratometric astigmatism (2.61 ± 2.43 D, P < 0.001) after complete suture removal. Subgroup analysis revealed that selective removal of interrupted sutures was effective as long as remaining interrupted and running sutures were left in place.

CONCLUSIONS

Complete suture removal was followed by an unpredictable and significant increase in post-DALK refraction and keratometry readings. In the subgroup that underwent early selective removal of interrupted sutures before complete suture removal, the desirable effects of this procedure significantly diminished after all remaining sutures were completely removed.

Updates on Managements for Keratoconus

Purpose

Keratoconus is a progressive disease of the cornea which can lead to blindness as irregular astigmatism increases. Currently, a variety of methods are available for the treatment of keratoconus, and in certain cases, it may be difficult to choose the most appropriate option. This article reviews available treatment modalities for keratoconus to provide the practitioner with practical and useful information for selecting the most suitable option for each individual patient.

Methods

To review treatment methods for different stages of keratoconus, PubMed (United States National Library of Medicine) and Scopus (Elsevier BV) databases were searched using the keywords “keratoconus”, “contact lens”, “cross-linking”, “Intacs”, “keratoplasty”, “gene therapy”, and “irregular astigmatism”, and related articles were reviewed based on disease assessment parameters and treatment methods.

Results

Various methods are available for the treatment of keratoconus: eyeglasses and contact lenses in the early stages, cross-linking for stabilizing disease progression, intrastromal corneal ring segments (ICRS) for reducing refractive errors or flattening the cornea, and penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK), conductive keratoplasty, gene therapy and more recently, bowman layer transplantation (BL transplantation) in advanced stages of the disease. To achieve optimum results, it is essential to choose the best option for each individual patient.

Conclusions

A commonality of the reviewed papers was the advancement of novel diagnostic and treatment methods in ophthalmology, which can delay the need for corneal grafting. A better understanding of keratoconus treatment options can help enhance visual rehabilitation and prevent blindness in keratoconus patients.