Anwar versus Melles deep anterior lamellar keratoplasty for keratoconus: a prospective randomized clinical trial

Descemetic Deep Anterior Lamellar Keratoplasty versus Penetrating Keratoplasty in Advanced Keratoconus: Comparison of Visual and Refractive Outcomes

Purpose

To assess and contrast the visual and refractive results of Descemetic deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) in the treatment of advanced keratoconus.

Design

Retrospective, comparative, interventional study.

Methods

This study enrolled eyes affected by keratoconus with preoperative mean keratometry ≥60 diopters (D) that were treated with either Descemetic DALK (30 eyes) or PK (29 eyes) by using always the same corneal diameters (8.00mm recipient; 8.25mm donor cornea) and the same suture technique (10-0 nylon double-running 12-bites continuous suture). The outcome measures were postoperative uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (CDVA), subjective refractive astigmatism (SRAst), and keratometric astigmatism at 3mm area (SimK), spherical equivalent (SEq).

Results

Postoperative visual acuity significantly improved in both groups. Mean CDVA was higher in the DALK group 3 months (DALK 0.61, PK 0.42, p<0.05), 6 months (DALK 0.69, PK 0.44, p<0.05), and 12 months (DALK 0.72, PK 0.45, p<0.05) postoperatively. However, 6 months after suture removal, CDVA was not statistically different between the two groups (DALK 0.71, PK 0.75, p>0.05). Final SRAst and SimK also were comparable between the two groups (respectively DALK 2.97, PK:2.81, p>0.05; DALK 3.91, PK 2.37, p>0.05). No significant statistical differences were noted for UCVA and SEq data during the entire follow-up period between the two groups.

Conclusion

Both methods of corneal transplantation resulted in a notable enhancement of visual and refractive outcomes in eyes afflicted by advanced keratoconus. Descemetic DALK demonstrated superior visual acuity before suture removal, whereas DALK and PK exhibited comparable results in terms of visual acuity, refractive correction, and keratometric astigmatism after suture removal.

Keratoconus: exploring fundamentals and future perspectives - a comprehensive systematic review

Background

New developments in artificial intelligence, particularly with promising results in early detection and management of keratoconus, have favorably altered the natural history of the disease over the last few decades. Features of artificial intelligence in different machine such as anterior segment optical coherence tomography, and femtosecond laser technique have improved safety, precision, effectiveness, and predictability of treatment modalities of keratoconus (from contact lenses to keratoplasty techniques). These options ingrained in artificial intelligence are already underway and allow ophthalmologist to approach disease in the most non-invasive way.

Objectives

This study comprehensively describes all of the treatment modalities of keratoconus considering machine learning strategies.

Design

A multidimensional comprehensive systematic narrative review.

Data sources and methods

A comprehensive search was done in the five main electronic databases (PubMed, Scopus, Web of Science, Embase, and Cochrane), without language and time or type of study restrictions. Afterward, eligible articles were selected by screening the titles and abstracts based on main mesh keywords. For potentially eligible articles, the full text was also reviewed.

Results

Artificial intelligence demonstrates promise in keratoconus diagnosis and clinical management, spanning early detection (especially in subclinical cases), preoperative screening, postoperative ectasia prediction after keratorefractive surgery, and guiding surgical decisions. The majority of studies employed a solitary machine learning algorithm, whereas minor studies assessed multiple algorithms that evaluated the association of various keratoconus staging and management strategies. Last but not least, AI has proven effective in guiding the implantation of intracorneal ring segments in keratoconus corneas and predicting surgical outcomes.

Conclusion

The efficient and widespread clinical translation of machine learning models in keratoconus management is a crucial goal of potential future approaches to better visual performance in keratoconus patients.

Trial registration

The article has been registered through PROSPERO, an international database of prospectively registered systematic reviews, with the ID: CRD42022319338.

Comparison of Femtosecond Laser Assistance and Manual Trephination in Deep Anterior Lamellar Keratoplasty in the Treatment of Keratoconus: A Meta-Analysis

PURPOSE

To compare the efficacy and safety of femtosecond laser-assisted deep anterior lamellar keratoplasty (F-DALK) with those of manual-trephination DALK (M-DALK) in treating keratoconus.

DESIGN

Systematic review and meta-analysis.

METHODS

Through November 2022, we comprehensively searched PubMed, EMBASE, the Cochrane Library, and 4 Chinese databases. Studies that involved comparisons between F-DALK and M-DALK groups and that reported on relevant efficacy and/or safety parameters were included. Primary outcomes were uncorrected- and corrected-distance visual acuity and intraoperative complication rates. Secondary outcomes were spherical equivalent, topographic astigmatism, refractive cylinder, mean keratometry, endothelial cell density, suture removal time, and postoperative complication rates. These data were analyzed using Cochrane Review Manager software version 5.3.

RESULTS

This meta-analysis included 9 nonrandomized controlled studies involving 1713 eyes. In eyes treated with F-DALK, corrected-distance visual acuity at 1 to 6 months (weighted mean difference = -0.07 [95% confidence interval {CI} -0.10 to -0.03]; I2 = 0%; P < .001) after surgery was better and intraoperative Descemet membrane perforation occurred less often (odds ratio = 0.53 [95% CI 0.31-0.92]; I2 = 6%; P = .02) than in eyes treated with M-DALK. No clinically significant differences in other outcomes were found among the groups.

CONCLUSIONS

Both F-DALK and M-DALK are safe and efficacious for patients with keratoconus. Compared with M-DALK, F-DALK can provide better early visual acuity and reduce the intraoperative perforation rate, and its likely improvements to long-term visual quality and endothelial cell preservation warrant further investigation. In addition, the 2 techniques seem to be comparable regarding refractive outcomes and other complications.

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.

In Vivo Biomechanical Measurements of the Cornea

In early corneal examinations, the relationships between the morphological and biomechanical features of the cornea were unclear. Although consistent links have been demonstrated between the two in certain cases, these are not valid in many diseased states. An accurate assessment of the corneal biomechanical properties is essential for understanding the condition of the cornea. Studies on corneal biomechanics in vivo suggest that clinical problems such as refractive surgery and ectatic corneal disease are closely related to changes in biomechanical parameters. Current techniques are available to assess the mechanical characteristics of the cornea in vivo. Accordingly, various attempts have been expended to obtain the relevant mechanical parameters from different perspectives, using the air-puff method, ultrasound, optical techniques, and finite element analyses. However, a measurement technique that can comprehensively reflect the full mechanical characteristics of the cornea (gold standard) has not yet been developed. We review herein the in vivo measurement techniques used to assess corneal biomechanics, and discuss their advantages and limitations to provide a comprehensive introduction to the current state of technical development to support more accurate clinical decisions.

Update on Pediatric Corneal Diseases and Keratoplasty

Managing pediatric corneal disorders is challenging as the prognosis of pediatric keratoplasty depends on several factors. Advancements in the genetic basis of congenital corneal diseases and investigations in congenital corneal conditions provide a better understanding of pediatric corneal conditions. Surgeons performing keratoplasty in children now have a choice of various techniques. Evolving surgical techniques of anterior lamellar and endothelial keratoplasties has expanded the management interventions in these pediatric corneal morbidity conditions; however, considerable concerns still exist in association with corneal transplantation in infants and children. Outcomes in pediatric keratoplasty depend upon the preoperative indications, the timing of surgical intervention, intraoperative and postoperative factors including the patient/care givers' compliance. Factors such as low scleral rigidity, higher rate of graft failure, need for frequent examinations under anesthesia, and difficulty in optimal visual acuity assessment still remain a considerable challenge in pediatric scenarios. In children, deprivation amblyopia as a result of the corneal opacification can adversely affect visual development, causing dense amblyopia. Outcomes to surgical interventions for management of corneal opacification in children is further compromised by the pre-existing amblyopia apart from the concerns of refractive outcome of the graft. Graft rejection, graft infection, amblyopia, and glaucoma continue to be serious concerns. In recent years both anterior and posterior lamellar keratoplasty techniques are being increasingly performed in pediatric eyes, which offer advantages in the form of lower risk of graft rejection. The timing of surgery, careful case selection, cautious intraoperative approach, and optimal postoperative management can improve the anatomical and functional outcome in difficult cases.

Assessment of Corneal Densitometry in Big-Bubble Dissection Versus Manual Dissection Deep Anterior Lamellar Keratoplasty

PURPOSE

The aim of this study was to assess corneal densitometry and visual outcomes after big-bubble deep anterior lamellar keratoplasty (BB-DALK) and manual dissection deep anterior lamellar keratoplasty in patients with keratoconus.

METHODS

This retrospective comparative observational study included 40 keratoconic patients who underwent DALK surgery: 22 eyes had BB-DALK (group I) and 18 eyes had failed BB technique and DALK was completed by manual dissection (group II). Best -corrected visual acuity (BCVA), corneal topographic parameters, residual stromal tissue thickness, and endothelial cell count were recorded at 1, 3, 6, and 12 months postoperatively. Densitometric analysis of different corneal layers and zones was performed using Scheimpflug tomography at each visit; values were recorded and compared between the 2 groups.

RESULTS

At 1 and 6 months postoperatively, BCVA was better in group I than in group II, but with no statistically significant difference. At 12 months, the visual acuities became nearly similar in both groups (0.30 ± 0.13 vs. 0.30 ± 0.14 logarithm of the minimum angle of resolution, P = 0.888). Regarding corneal densitometric analysis, the recorded values for the posterior corneal layer were significantly higher in group II compared with group I at 3, 6, 9, and 12 months postoperatively in the 0- to 2-mm zone (P < 0.001) and the 2- to 6-mm zone (P = 0.029, 0.028, 0.001, and <0.001).

CONCLUSIONS

Manual dissection DALK after failed BB technique may affect the interface stromal reflectivity up to 12 months postoperatively. However, this does not significantly affect the visual acuity in comparison with successful BB-DALK.

Clear Cornea Femto DALK: a novel technique for performing deep anterior lamellar keratoplasty

PURPOSE

A new femtosecond laser assisted deep anterior lamellar keratoplasty technique (Clear Cornea Femto DALK or CCF DALK) can be performed with less technical challenges compared to conventional procedures. This paper reports on a preliminary case series to evaluate the technique.

METHOD

First, through a clear cornea approach, Descemet's membrane (DM) is completely separated from posterior stroma by injection of balanced salt solution/viscoelastic substance through a special cannula inserted into the deep stroma and positioned right above the DM without perforating. The injection creates a liquid chamber that detaches the DM while preserving a reasonably transparent corneal stroma. Afterwards, a complete posterior/anterior trephination of the stroma, from the liquid chamber to the epithelium, is done using a femtosecond laser system under optical coherence tomography control.

RESULTS

This technique was successfully performed in a preliminary series of 10 eyes/10 patients. All patients had the DM completely bared and kept their own endothelial cell population with minimal cell loss (< 15%) after 6 months. Postoperative interface reaction was minimal, and no immune reactions were observed thus far.

CONCLUSION

Clear Cornea Femto DALK is a promising alternative to previous Femto DALK procedures with good acceptance of the tissue seen to date.

Comparison of deep anterior lamellar keratoplasty and corneal cross-linking in patients with advanced keratoconus

PURPOSE

To compare outcomes of deep anterior lamellar keratoplasty (DALK) and corneal cross-linking (CXL) in patients with advanced keratoconus, with the primary aim of assessing CXL as a potential therapeutic alternative.

STUDY DESIGN

Retrospective, multi-center, comparative study.

METHODS

Patients with advanced keratoconus (maximum keratometry reading (K-max) > 58D, best spectacle-corrected visual acuity worse than 0.52logMAR), undergoing either DALK or CXL treatment at four tertiary ophthalmic centers in Wenzhou, Hangzhou, Nanjing and Wuhan were included. Visual acuity, refractive error, corneal topography and complications were evaluated at baseline and at least 2 year postoperatively.

RESULTS

75 eyes of 72 patients were included, of which 37 eyes underwent DALK and 38 eyes, CXL. A larger reduction in Kmax was observed in the DALK group (-18.18 ± 9.44 D versus -1.10 ± 2.70D, p < 0.001). Seven eyes (18%) in the CXL group showed progression of keratoconus. No disease progression was observed in the DALK group. Greater improvements in best spectacle-corrected visual acuity (logMAR) were observed in the DALK group (-0.59 ± 0.25 versus -0.24 ± 0.44, p < 0.001).

CONCLUSIONS

Compared to CXL, DALK leads to larger reductions in Kmax and better improvement in visual acuity in advanced keratoconus.

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.

Comparison of corneal biomechanical properties following penetrating keratoplasty and deep anterior lamellar keratoplasty for keratoconus

IMPORTANCE

Keratoplasty is a surgical procedure to create a more regular optical surface following biomechanical weakening of the cornea in keratoconus. The ideal keratoplasty procedure should also restore corneal biomechanics to that of the healthy cornea.

BACKGROUND

This study aimed to evaluate and compare the biomechanical properties of corneas following penetrating keratoplasty (PKP) and predescematic deep anterior lamellar keratoplasty (DALK) to those of healthy eyes.

DESIGN

Prospective cross-sectional study.

PARTICIPANTS

Two cohorts of post-keratoplasty eyes (42 eyes with PKP and 27 eyes with DALK) with each other, and with a cohort of 152 healthy eyes.

METHODS

All eyes were examined by slit-lamp biomicroscopy, tomography, anterior segment-OCT and non-contact tonometry CorVis ST (CST).

MAIN OUTCOME MEASURES

CST biomechanical parameters, maximum corneal deformation (MCD) and corneal energy dissipation were compared between keratoplasty techniques, and with healthy eyes.

RESULTS

The mean age of participants with PKP and DALK were 35 ± 13.7 and 36.1 ± 12.6 years, respectively. None of the CST parameters were significantly different between PKP and DALK eyes. However, when compared to healthy corneas, numerous parameters were significantly different for both keratoplasty techniques. Of note, MCD was significantly higher in PKP compared to DALK and healthy corneas, after controlling for co-factors.

CONCLUSIONS AND RELEVANCE

Neither type of keratoplasty technique utilized in keratoconus completely restored corneal biomechanical properties to that of healthy corneas. However, PKP resulted in a greater number of parameters significantly different to healthy corneas, compared to DALK.

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.

Incidence and Outcomes of Intraoperative Descemet Membrane Perforations During Deep Anterior Lamellar Keratoplasty

PURPOSE

To report the incidence and outcomes of intraoperative Descemet membrane (DM) perforations during deep anterior lamellar keratoplasty (DALK).

DESIGN

Retrospective, consecutive, interventional case series.

METHODS

A retrospective audit of all DALK cases performed from 2004 to 2015 in a tertiary center, with and without intraoperative DM perforations. We excluded cases with preexisting corneal perforations before surgery.

RESULTS

There were a total of 540 eyes, of which 101 (18.7%) had intraoperative DM perforations. These included 79 eyes (78.2%) with microperforations and 15 eyes (14.9%) with macroperforation. The most common steps at which DM perforation occurred intraoperatively were during deep lamellar dissection (32 cases; 31.7%), air injection (27 cases; 26.7%), and suturing (21 cases; 20.8%). Management of the DM perforations included a combination of intracameral air tamponade (49 cases; 48.5%), stromal patching (10 cases; 9.9%), fibrin glue (8 cases; 7.9%), and suturing of the defect (1 case; 1.1%). There were 2 eyes (2/540; 0.37%) that were converted to penetrating keratoplasty (PK). There were no significant differences in the postoperative unaided or best-corrected visual acuity, or in the numbers of patients with postoperative graft failure, graft rejection, or subsequent surgery at postoperative years 1 and 3.

CONCLUSIONS

DALK cases with DM perforations intraoperatively are often able to be managed without conversion to PK. Cases with DM perforations intraoperatively have equivalent visual acuity outcomes compared to those without DM perforations, and did not have any increased risk of graft failure, rejection, or subsequent surgery at postoperative years 1 and 3.

Evaluation of Big Bubble Technique for Deep Anterior Lamellar Keratoplasty in Patients With Radial Keratotomy

PURPOSE

To report the outcome of deep anterior lamellar keratoplasty (DALK) and success rates of the big-bubble (BB) technique or manual dissection after a failed use of the BB technique in eyes that underwent prior radial keratotomy (RK).

METHODS

A retrospective chart review of patients who underwent DALK after RK at Toronto Western Hospital, Canada, between 1999 and 2017 was performed. Demographic characteristics, success rates of the BB technique and manual dissection, intraoperative and postoperative complications, and best spectacle-corrected visual acuity before and after corneal transplant were analyzed.

RESULTS

Ten eyes of 9 patients were included in the analysis. The average age was 64 ± 10 years (range 49-82). The average time between the RK surgery and the corneal transplant was 20 ± 5 years (range 8-24). Indications for corneal transplant were significant irregular astigmatism in 5 eyes (50%), central scarring or haze in 4 eyes (40%), and progressive hyperopia with visual fluctuation in one eye (10%). BB was successfully achieved in one eye (10%). In 6 eyes (60%), manual dissection was performed, and in 3 eyes (30%), DALK surgery was converted to penetrating keratoplasty. The average best spectacle-corrected visual acuity on the last follow-up visit was 0.26 ± 0.08 logMAR (Snellen equivalent 20/36). One eye that underwent manual DALK and one eye that underwent penetrating keratoplasty developed a rejection episode 4 and 2 months after keratoplasty, respectively. In both cases, rejection resolved with topical steroids.

CONCLUSIONS

In eyes that underwent prior RK, DALK by manual dissection should be considered as a preferable surgical technique.

Deep anterior lamellar keratoplasty: A surgeon's guide

Purpose

To review and highlight important practical aspects of deep anterior lamellar keratoplasty (DALK) surgery and provide some useful tips for surgeons wishing to convert to this procedure from the conventional penetrating keratoplasty (PK) technique.

Methods

In this narrative review, the procedure of DALK is described in detail. Important pre, intra, and postoperative considerations are discussed with illustrative examples for better understanding. A comprehensive literature review was conducted in PubMed/Medline from January 1995 to July 2017 to identify original studies in English language regarding DALK. The primary endpoint of this review was the narrative description of surgical steps for DALK, its pitfalls, and management of common intraoperative complications.

Results

A standard DALK procedure can be successfully performed taking into consideration factors such as age, ophthalmic co-morbidities, status of the crystalline lens, retina, and intraocular pressure. Careful trephination and dissection of the host cornea employing appropriate technique (such as big bubble technique, manual dissection, visco-dissection, etc.) suitable for the specific case is important to achieve good postoperative outcomes. Prompt identification of intraoperative complications such as double bubble, micro and macroperforations, etc. are vital to change the management strategies.

Conclusion

Although there is a steep learning curve for DALK procedure, considering details and having insight into the management of intraoperative issues facilitates learning and reduces complication rates.

Femtosecond laser-assisted deep anterior lamellar keratoplasty in phototherapeutic keratectomy versus the big-bubble technique in keratoconus

AIM

To compare the functional and anatomic results of femtosecond laser (FSL)-assisted deep anterior lamellar keratoplasty (DALK) associated with phototherapeutic keratectomy (PTK) and FSL-assisted DALK performed using the big-bubble technique in keratoconus.

METHODS

During the first phase of the study, an electron microscopy histopathology pilot study was conducted that included four unsuitable donor corneas divided into two groups: in FSL group, FSL lamellar cuts were performed on two corneas and in FSL+PTK group, PTK was performed at the stromal beds of two corneas after FSL lamellar cuts were made. During the second phase of the study, a randomized clinical trial was conducted that included two treatment groups of patients with keratoconus: group 1 (n=14 eyes) underwent FSL-assisted DALK associated with PTK and group 2 (n=12 eyes) underwent FSL-assisted DALK associated with the big-bubble technique. The main outcome measures were the postoperative visual acuity (VA) and optical coherence tomography (OCT) measurements, confocal microscopic findings, and contrast sensitivity.

RESULTS

In the pilot study, histopathology showed a more regular stromal bed in the FSL+PTK group. In the clinical trial, group 1 had significantly worse best spectacle-corrected VA and contrast sensitivity (P<0.05 for both comparisons). The residual stromal bed measured by OCT was significantly (P<0.05) thicker in group 1. Confocal microscopy detected opacities only at the donor-receptor interface in group 1.

CONCLUSION

Patients with keratoconus treated with FSL-assisted DALK performed using the big-bubble technique fare better than treated with FSL-assisted DALK associated with PTK.

Comparison of densitometric profile after deep lamellar keratoplasty with two different techniques for treatment of keratoconus

PURPOSE

To compare densitometric outcome of two techniques of deep lamellar keratoplasty using Pentacam HR corneal densitometry software.

METHODS

Postoperative outcomes of 31 patients with big bubble (BB) and 28 patients with Melles (M) surgery for the treatment of keratoconus were evaluated. Data were gathered at least 3 months after the removal of all sutures including demographic data, uncorrected distance visual acuity (UCDVA), best spectacle-corrected visual acuity (BSCVA), refraction and endothelial cell count. Moreover, the Scheimpflug images were taken by Pentacam^® HR to assess keratometric profile, densitometric outcomes in different depths and zones of the cornea and central corneal thickness. Anterior segment OCT was performed in ten cases of M group.

RESULTS

Thirty-one eyes with BB and 27 eyes M surgery were enrolled. Comparison of densitometric profile between groups revealed no statistical significance in zone 0-2 mm, zone 2-6 mm and zone 10-12 mm in all depths (all P values >  0.05). Zone 6-10 mm of M group had lower densitometric readings (more transparent) in anterior, central and posterior layers of the cornea in comparison with BB group (all P <  0.05). Also no statistical difference was found in UCDVA, BSCVA, spherical or cylindrical refractive error, and spherical equivalent, keratometric readings, endothelial cell count and central corneal thickness in two groups (all P values >  0.05).

CONCLUSION

Densitometric profiles were identical in both methods in visually important zones so as visual and refractive outcomes.

Avoiding big bubble complications: outcomes of layer-by-layer deep anterior lamellar keratoplasty in children

BACKGROUND/AIMS

To describe the visual and clinical outcomes of manual layer-by-layer deep anterior lamellar keratoplasty (DALK) in a paediatric population.

METHODS

The charts of all children who underwent DALK surgery between January 2007 and January 2015 were reviewed retrospectively. Data collected included preoperative and postoperative spectacle-corrected distance visual acuity (CDVA), intraoperative and postoperative complications including graft rejection and failure. Residual posterior lamellar thickness (RPLT) and endothelial cell density (ECD) were measured in eyes with follow-up longer than 6 months.

RESULTS

Fifty-one eyes of 42 patients were included in the study. The mean patient age at surgery was 11.2±5.2 years and the mean follow-up time was 36.5±23.7 months. The most common indications for surgery were mucopolysaccharidosis (29.4%) and keratoconus (23.5%). Nine eyes (17.6%) had intraoperative microperforation, none of which were converted to penetrating keratoplasty (PKP). Only one eye (2.0%) was converted to PKP. Five eyes (9.8%) had a stromal rejection episode of which one eye failed. Another four eyes (7.8%) experienced graft failure among which three eyes (75%) had infectious keratitis. Three of the five failed grafts had a successful repeat DALK. The average RPLT was 81.9±36.5μm. ECD was significantly lower in the operated eye compared with the normal eye (3096±333 cells/mm² vs 3376±342 cells/mm², n=11, P=0.003). The mean postoperative CDVA was 0.5±0.4 logarithm of the minimum angle of resolution (logMAR) reflecting a gain of 0.3 logMAR (P<0.001).

CONCLUSION

Manual dissection DALK is a safe procedure in children with stromal opacities. Despite successful structural rehabilitation, functional recovery is still suboptimal mostly due to amblyopia.

Component corneal surgery: An update

Several decades ago, penetrating keratoplasty was a challenge to corneal surgeons. Constant effort by the corneal surgeon to improve the outcomes as well as utilization of the available resources has led to a revolutionary change in the field of keratoplasty. All these efforts have led to the evolution of techniques that allow a corneal surgeon to disease-specific transplant of individual layers of corneal “so-called component corneal surgery” depending on the layer of cornea affected. This has led to an improvement in corneal graft survival as well as a better utilization of corneal tissues. This article reviews the currently available literature on component corneal surgeries and provides an update on the available techniques.

Comparison of femtosecond laser-assisted descemetic and predescemetic lamellar keratoplasty for keratoconus

PURPOSE

The purpose of this study is to compare the outcomes following femtosecond laser-assisted deep anterior lamellar keratoplasty (DALK) with 75% of stromal dissection (predescemetic group) and femtosecond laser-assisted DALK using big-bubble technique with total stromal resection (descemetic group) for the treatment of keratoconus.

SUBJECTS AND METHODS

Twenty eyes of 17 patients with keratoconus were studied. There were 10 eyes of 9 patients in predescemetic group and 10 eyes of 8 patients in descemetic group. The postoperative best-corrected visual acuity (BCVA), manifest refraction, keratometry, endothelial cell density (ECD), and central corneal thickness (CCT) were analyzed.

RESULTS

All surgeries were performed uneventfully. At 1 year after surgery, the BCVA, corneal astigmatism, keratometry, CCT, and ECD between two groups were not statistically significant (all P > 0.05). However, the mean manifest refraction was -9.43 ± 7.44 diopter (D) and -1.03 ± 1.13D in predescemetic and descemetic groups, respectively, which was statistically significant between two groups (P < 0.05).

CONCLUSIONS

The results of BCVA and corneal astigmatism, keratometry, ECD, and CCT were comparable between two groups. However, the mean postoperative manifest refraction was lower in descemetic group.

Femtosecond laser-assisted in situ keratomileusis for the correction of residual ametropia after deep anterior lamellar keratoplasty: a pilot investigation

PurposeTo evaluate the refractive and visual results of one-stage laser-assisted in situ keratomileusis with femtosecond laser (Femto-LASIK) for the correction of residual ametropia after deep anterior lamellar keratoplasty (DALK).MethodsThis retrospective study included 13 eyes of 12 patients, who underwent corneal Femto-LASIK to correct refractive errors after DALK. IntraLase FS150 was used to create a lamellar flap and excimer laser ablation for refractive correction was performed using the Star S4 IR Excimer Laser in eight cases and the Technolas 217z Excimer Laser in Tissue Saving mode in five cases. Perioperative variables of interest included uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction and corneal topography.ResultsThe mean spherical equivalent preoperatively was -4.85±2.82 (range, -9.5 to 0 D). At the last visit the mean postoperative spherical equivalent (SE) was -0.44±0.67 D (P<0.05). The mean postoperative UDVA was 0.12±0.12 logMAR. There was a statistically significant increase in CDVA 6 months after Femto-LASIK (P<0.05). Intraoperative and postoperative complications did not develop in this series of eyes.ConclusionsCorrecting the preoperative manifest refractive error with Femto-LASIK led to a significant improvement in the UDVA and CDVA without surgical complications.

Systematic review comparing penetrating keratoplasty and deep anterior lamellar keratoplasty for management of keratoconus

AIM

Perception of reduced incidence of graft rejection after deep anterior lamellar keratoplasty (DALK) has attracted many surgeons towards this technique in keratoconus. This review aims to compare the visual, refractive and graft outcomes after penetrating keratoplasty (PK) and DALK for keratoconus.

METHODS

Electronic searches of PubMed, MEDLINE, EMBASE, Latin American and Caribbean Health Sciences Literature database (LILACS), metaRegister of Controlled Trials (mRCT), ClinicalTrial.gov and the WHO International Clinical Trials Registry Platform (ICTRP) were performed. We included randomized control trials (RCTs) and comparative studies to assess primary and secondary outcomes after PK and DALK in eyes with keratoconus. Primary outcome was best-corrected visual acuity (BCVA) LogMAR at ≥6 months. Secondary outcomes included number of patients with BCVA≥0 LogMAR, uncorrected visual acuity (UCVA) LogMAR, spherical equivalent (SE), refractive and keratometric astigmatism, endothelial cell density (ECD) cell/mm², graft rejection and graft survival.

RESULTS

Eighteen studies (including 2 RCTs) compared DALK (965 eyes) and PK (2402 eyes) for keratoconus. There was strong evidence through RCTs suggesting better LogMAR BCVA at ≥6 months and better LogMAR UCVA with PK; reduced refractive astigmatism and rejection with DALK and no difference in SE and keratometric astigmatism. Moreover, there was weak evidence to suggest better BCVA≥0 LogMAR after PK and no difference in ECD between the two techniques.

CONCLUSIONS

Despite the popularity of DALK amongst corneal surgeons for keratoconus, there is a paucity of high quality RCTs. The existing limited evidence confirms reduced rejection and refractive astigmatism with DALK but better visual outcomes with PK. Internationally agreed data sets and follow-up protocol are warranted.

Corneal surgery in keratoconus: which type, which technique, which outcomes?

Keratoconus is a disease characterized by progressive thinning, bulging, and distortion of the cornea. Advanced cases usually present with loss of vision due to high irregular astigmatism. A majority of these cases require surgical intervention. This review provides an update on the current treatment modalities of corneal surgery available for the management of advanced corneal ectasias.

Aetiology-specific comparison of long-term outcome of deep anterior lamellar keratoplasty for corneal diseases

AIMS

To evaluate the long-term outcome of deep anterior lamellar keratoplasty (DALK) for the treatment of herpetic keratitis, keratoconus, stromal scars and corneal dystrophies.

METHODS

This retrospective consecutive case study includes 275 consecutive eyes of 254 patients who underwent DALK; 35 eyes with herpetic keratitis, 114 eyes with stromal scar, 93 eyes with keratoconus and 67 eyes with corneal dystrophy. Exclusion criteria included therapeutic DALK for the treatment of descemetocele or infectious keratitis, and eyes with limbal stem cell deficiency. Patients were examined at 1, 3 and 6 months, and 1, 3 and 5 years after DALK. Graft survival rate, best corrected visual acuity (BCVA), endothelial cell density (ECD) and postoperative complications were evaluated.

RESULTS

The mean postoperative follow-up duration was 51±41 months. The graft survival rate of all subjects was 96.8% at 1 year, 89.9% at 3 years, 83.5% at 5 years and 74.1% at 10 years. At 6 months, BCVA significantly improved from 1.14±0.54 to 0.22±0.21 in the keratoconus group, from 1.13±0.60 to 0.44±0.54 in the herpes group, from 1.00±0.59 to 0.49±0.38 in the stromal scar group and from 1.04±0.52 to 0.32±0.29 in the corneal dystrophy group (all, p<0.0001). BCVA stabilised after 6 months thereafter up to 5 years. ECD decreased just after DALK and maintained >1000 cell/mm(2) at 5 years in all groups.

CONCLUSIONS

DALK provides good visual acuity with slight ECD decrease over long term in all groups.

A year of cornea in review: 2013

PURPOSE

The goal of this study was to provide an update of significant corneal literature published in 2013.

DESIGN

This study is a systematic literature review.

METHODS

We conducted a systematic review of the English-language literature published from January 1, 2013, to December 31, 2013, using the following PubMed search and Medical Subject Headings terms: cornea transplantation, keratoplasty, Descemet membrane endothelial keratoplasty, Descemet stripping endothelial keratoplasty, cross linking, pre-Descemet's layer, Rho-associated kinase, keratoprosthesis, infectious keratitis, corneal dystrophy, corneal astigmatism, and keratoconus.

RESULTS

This review summarizes relevant and innovative original articles, review articles, and novel techniques from the following journals: American Journal of Ophthalmology, British Journal of Ophthalmology, Cornea, Graefe's Archive for Clinical and Experimental Ophthalmology, Investigative Ophthalmology & Visual Science, JAMA Ophthalmology, Journal of Cataract and Refractive Surgery, Journal of Refractive Surgery, and Ophthalmology. Case reports, abstracts, letters to the Editor, and unpublished work were excluded, as well as articles e-published ahead of print in 2012 that were discussed in the previous review. One hundred twenty-seven articles met the criteria for this review.

CONCLUSIONS

This review summarizes significant cornea-related literature from 2013.

[Corneal transplantation in keratoconus: penetrating keratoplasty versus deep anterior lamellar keratoplasty with Melles technique]

OBJECTIVES

To evaluate the effectiveness of deep anterior lamellar keratoplasty (DALK) using Melles technique (technique B) in patients with advanced keratoconus versus a classic technique, penetrating keratoplasty (technique A).

METHODOLOGY

Retrospective descriptive comparative study between technique A and technique B in homogeneous groups.

RESULTS

Best corrected visual acuity (Snellen test decimal scale) was 0.77±0.32 for group A and 0.62±0.29 for group B, with no statistically significant differences. The mean spherical final refraction in group A was 1.73±5.1 diopters, and the mean spherical equivalent was -3.92±5.1. Technique B group gave values -2.67±4.02 diopters and -4.55±4.08 diopters, respectively, with no statistically significant differences. The residual cylinder after removal of the sutures was 4.47±2.47 diopters for group A and 3.77±1.63 for group B, with no statistically significant differences.

CONCLUSION

No statistically significant differences were found for any of the studied variables when comparing both groups using the t -test for independent samples. More studies on the homogeneity and residual stromal bed thickness could provide the key to determine whether this technique is closer to the visual acuity of penetrating keratoplasty or DALK by a descemet technique.

The ocular surface chemical burns

Ocular chemical burns are common and serious ocular emergencies that require immediate and intensive evaluation and care. The victims of such incidents are usually young, and therefore loss of vision and disfigurement could dramatically affect their lives. The clinical course can be divided into immediate, acute, early, and late reparative phases. The degree of limbal, corneal, and conjunctival involvement at the time of injury is critically associated with prognosis. The treatment starts with simple but vision saving steps and is continued with complicated surgical procedures later in the course of the disease. The goal of treatment is to restore the normal ocular surface anatomy and function. Limbal stem cell transplantation, amniotic membrane transplantation, and ultimately keratoprosthesis may be indicated depending on the patients' needs.

Deep anterior lamellar keratoplasty with a manual spatula: anatomical and functional results

Objective:

Evaluate the anatomical, refractive, and functional results of an innovative technique of deep anterior lamellar keratoplasty with a manual spatula.

Materials and Methods:

We evaluated the results and examinations of 16 eyes from 14 patients who underwent deep anterior lamellar keratoplasty using the technique described by Ferrara. Residual bed thickness after keratoplasty was evaluated postoperatively using Visante. The measurement was performed using a technique similar to that used to measure flap thickness after laser in situ keratomileusis refractive surgery. The measurements were performed at the center of the cornea in an area comprising the central 3-mm in the 45° and 135° meridians.

Results:

Best-corrected visual acuity was 0.34 ± 0.18 LogMar (0.09 to 0.60 LogMar), the spherical equivalent was -4.31 ± 3.38 D (+0.25 to -9.50 diopters), and keratometry was 45.75 ± 2.77 D (41.11 to 52.48 diopters) postoperatively. Corneal astigmatism was 3.19 ± 2.78 D (0.18 to 11.81 diopters). Residual stromal bed thickness measured by optical coherence tomography showed values of 67.1 ± 24.3 μm (30 to 109 μm). The statistical correlation by Spearman's test between the best-corrected visual acuity and the residual stromal bed thickness was 0.11 (P = 0.67).

Conclusion:

Deep anterior lamellar keratoplasty, in which manual dissection was performed using an instrument similar to that used to implant corneal rings, provided good visual and anatomical results.

One Year of Cornea Research in Review-2012

PURPOSE

The purpose of this study was to provide an update of significant cornea literature published in the past 1 year.

DESIGN

This was a literature review.

METHODS

The authors conducted a 1-year English-language literature search on PubMed, from January 1, 2012, to December 31, 2012, using the following terms: corneal transplantation, anterior lamellar keratoplasty, penetrating keratoplasty, endothelial keratoplasty, Descemet stripping automated endothelial keratoplasty, Descemet membrane endothelial keratoplasty, Descemet membrane endothelial transfer, ocular surface epithelial transplantation, limbal epithelial transplantation, cultivated oral mucosal epithelial transplantation, keratoprosthesis, infectious keratitis, cross-linking, keratoconus, corneal neovascularization, corneal imaging, optical coherence tomography, Pentacam Scheimpflug imaging, and in vivo confocal microscopy.

RESULTS

This review includes original articles and review articles that contain significant updates and novel aspects in the field of cornea from the following journals: American Journal of Ophthalmology, British Journal of Ophthalmology, Ophthalmology, Investigative Ophthalmology and Visual Science, and Cornea. Letters to the editor, unpublished work, manuscripts not in English, and abstracts were not included.

CONCLUSIONS

This review highlights significant literature that is applicable to the practicing ophthalmologist.

Corneal Allograft Rejection: Immunopathogenesis to Therapeutics

Corneal transplantation is among the most successful solid organ transplants. However, despite low rejection rates of grafts in the ‘low-risk’ setting, rejection can be as high as 70% when grafted into ‘high-risk’ recipient beds. Under normal homeostatic conditions, the avascular cornea provides a unique environment that facilitates immune and angiogenic privilege. An imbalance in pro-inflammatory, angiogenic and lymphangiogenic mediators leads to a breakdown in corneal immune privilege with a consequent host response against the donor graft. Recent developments in lamellar and endothelial keratoplasties have reduced the rates of graft rejection even more, while providing improved visual outcomes. The corneal layer against which an immune response is initiated, largely determines reversibility of the acute episode. While epithelial and stromal graft rejection may be treated with topical corticosteroids with higher success, acute endothelial rejection mandates a more aggressive approach to therapy due to the lack of regenerative capacity of this layer. However, current immunosuppressive regimens come with the caveat of ocular and systemic side effects, making prolonged aggressive treatment undesirable. With the advent of biologics, efficacious therapies with a superior side effect profile are on the horizon. In our review we discuss the mediators of ocular immune privilege, the roles of cellular and molecular immune players in graft rejection, with a focus on human leukocyte antigen and antigen presenting cells. Furthermore, we discuss the clinical risk factors for graft rejection and compare rates of rejection in lamellar and endothelial keratoplasties to traditional penetrating keratoplasty. Lastly, we present the current and upcoming measures of therapeutic strategies to manage and treat graft rejection, including an overview of biologics and small molecule therapy.