Penetrating Keratoplasty versus Deep Anterior Lamellar Keratoplasty for Keratoconus: A Systematic Review and Meta-analysis

Intrastromal Suturing Technique Compared With Interrupted Corneal Suturing Technique, Loose Suture and Knot Exposure: A Comparative Rabbit Study

PurposeThis study aimed to assess the effectiveness of an innovative intrastromal suturing technique in an experimental rabbit model, comparing it to standard interrupted suturing, loose suture, and suturing with knot exposure.MethodsFourteen adult male New Zealand White rabbits were included in this study. Each rabbit underwent suturing in both eyes, divided into four groups based on suturing techniques. The novel intrastromal suturing technique involved burying the entire suture material within the corneal stroma. Corneal neovascularisation (CoNV) areas were evaluated by image analysis and immune cell densities by in vivo confocal microscopy (IVCM).ResultsThe intrastromal suturing group demonstrated significantly smaller CoNV areas at both 1 week and 1 month post-suturing compared to other interventional groups, indicating effective mitigation of CoNV development and progression. Moreover, this group exhibited lower immune cell densities in the superficial stromal layer and endothelial layer, suggesting a reduced inflammatory response. Both the loose suture and the knot exposure groups exhibited significant levels of CoNV and heightened immune cell densities.ConclusionThis experimental study demonstrated effectiveness of intrastromal suturing technique in limiting CoNV and immune cell infiltration, common contributors to graft rejection and complications. Furthermore, the study revealed that loose sutures and those with exposed knots are likely to cause more severe CoNV and inflammation, compared to the traditional interrupted suturing technique and intrastromal suturing.

Healing the cornea: Exploring the therapeutic solutions offered by MSCs and MSC-derived EVs

Affecting a large proportion of the population worldwide, corneal disorders constitute a concerning health hazard associated to compromised eyesight or blindness for most severe cases. In the last decades, mesenchymal stem/stromal cells (MSCs) demonstrated promising abilities in improving symptoms associated to corneal diseases or alleviating these affections, especially through their anti-inflammatory, immunomodulatory and pro-regenerative properties. More recently, MSC therapeutic potential was shown to be mediated by the molecules they release, and particularly by their extracellular vesicles (EVs; MSC-EVs). Consequently, using MSC-EVs emerged as a pioneering strategy to mitigate the risks related to cell therapy while providing MSC therapeutic benefits. Despite the promises given by MSC- and MSC-EV-based approaches, many improvements are considered to optimize the therapeutic significance of these therapies. This review aspires to provide a comprehensive and detailed overview of current knowledge on corneal therapies involving MSCs and MSC-EVs, the strategies currently under evaluation, and the gaps remaining to be addressed for clinical implementation. From encapsulating MSCs or their EVs into biomaterials to enhance the ocular retention time to loading MSC-EVs with therapeutic drugs, a wide range of ground-breaking strategies are currently contemplated to lead to the safest and most effective treatments. Promising research initiatives also include diverse gene therapies and the targeting of specific cell types through the modification of the EV surface, paving the way for future therapeutic innovations. As one of the most important challenges, MSC-EV large-scale production strategies are extensively investigated and offer a wide array of possibilities to meet the needs of clinical applications.

Comparison of clinical outcomes, complications and patient satisfaction following deep anterior lamellar keratoplasty and penetrating keratoplasty

BACKGROUND

Keratoplasty is a surgical procedure in which a damaged or diseased cornea is replaced with healthy donor tissue, thereby restoring vision. Recent advancements have led to the replacement of penetrating keratoplasty (PKP) with the more selective deep anterior lamellar keratoplasty (DALK) procedure, especially for treating keratoconus. Although DALK typically has a shorter recovery time, less pain and a lower risk of rejection, PKP is still being performed for more severe corneal diseases. A comparative study of clinical profiles, treatment outcomes and patient-reported satisfaction will provide valuable insights into the cost-effectiveness, impact on quality of life and ability of each procedure to treat different pathologies of the cornea. Here, we aimed to compare the clinical and subjective outcomes of DALK with those of the PKP at a single center in the Kingdom of Saudi Arabia.

METHODS

This retrospective cohort study included eyes that underwent either PKP or DALK from January 2017 to January 2021. The demographic features, indications, best corrected visual acuity (BCVA) and complications of the patients were recorded for both groups, analyzed and compared. A subgroup of eyes with keratoconus was analyzed separately and compared to the larger group. A 6-item survey was conducted via telephone to assess patient satisfaction and expectation, and the results were compared between the two procedures. The chi-square test or Fisher's exact test for categorical variables or the t test or Kruskal‒Wallis test for continuous variables were used as appropriate for all comparisons, and the level of significance was set at α = 0.05.

RESULTS

A total of 97 patients were included. PKP and DALK were performed on 63 and 39 eyes, respectively. Patients who underwent DALK were younger (mean ± standard deviation 31 ± 10.82 years versus 43 ± 26.89 years for patients who underwent PKP). The most frequent indication for PKP was keratoconus (35.5%); however, in 97.4% of the eyes undergoing DALK, the indication was keratoconus. In both groups, visual acuity and refractive error improved, but the postoperative corrected distance visual acuity in the DALK group (0.3 log MAR) was noticeably greater than that in the PKP group (0.6 log MAR). Compared with PKP, DALK may carry a lower risk of early graft edema and rejection. Overall, the reported postoperative patient satisfaction was similar for both procedures.

CONCLUSION

The findings highlight the effectiveness of PKP and DALK in improving visual acuity and emphasize the importance of considering patient-reported outcomes in evaluating success. DALK has been demonstrated to be beneficial for protecting the corneal endothelium and lowering the risk of complications and graft rejection.

Subfoveal choroidal thickness increases after excimer laser-assisted penetrating keratoplasty but not after excimer laser-assisted deep anterior lamellar keratoplasty

To evaluate the impact of excimer laser-assisted deep anterior lamellar keratoplasty (Exc-DALK) and excimer laser-assisted penetrating keratoplasty (Exc-PKP) on subfoveal choroidal thickness (SFCT) in eyes with advanced keratoconus. A retrospective comparative clinical study, which compares the outcomes of 24 eyes treated with Exc-DALK (G1) against matched group of 43 eyes treated with Exc-PKP (G2) at both 2 months (T1) and 2 years (T2) postoperatively. Main outcomes included best-corrected visual acuity (BCVA), central macular thickness (CMT), and SFCT. Preoperatively, there were no significant differences between both groups regarding BCVA, CMT or SFCT (p > 0.05). There were no significant differences between both groups regarding BCVA at both follow-ups (p > 0.05). There were no significant differences between both groups regarding CMT at both follow-ups (p > 0.05). SFCT was higher in G2 than G1 at both follow-ups (p < 0.01). Compared to preoperative SFCT, there were no significant changes in SFCT in G1 at both follow-ups (p > 0.05). In G2, SFCT increased significantly at T1 (p < 0.01) and did not differ significantly at T2 (p = 0.17). SFCT increased significantly after Exc-PKP but not after Exc-DALK, which might indicate that Exc-DALK affects the choroid less and thus could represent a less traumatic approach to ocular tissue than Exc-PKP.

Keratoconus: imaging modalities and management

Background

Keratoconus (KCN) is characterized by gradual thinning and steepening of the cornea, which can lead to significant vision problems owing to high astigmatism, corneal scarring, or even corneal perforation. The detection of KCN in its early stages is crucial for effective treatment. In this review, we describe current advances in the diagnosis and treatment of KCN.

Methods

This narrative review focuses on recent advancements in the diagnosis and treatment of KCN, especially evolving approaches and strategies. To ensure the inclusion of the most recent literature, relevant publications discussing advanced imaging techniques and treatment options for KCN were extensively gathered from the PubMed/MEDLINE and Google Scholar databases. The following index terms and keywords were used for the online search: keratoconus, diagnosis of keratoconus, advances in the diagnosis of keratoconus, topography or tomography, anterior segment optical coherence tomography, treatment of keratoconus, advances in the treatment of keratoconus, collagen crosslinking, intrastromal ring, keratoplasty, and new techniques in keratoconus.

Results

Various screening methods such as corneal topography, tomography, anterior segment optical coherence tomography, and assessment of corneal biomechanics have been developed to identify KCN in its early stages. After diagnosis, KCN management focuses on preventing disease progression. Corneal collagen crosslinking is a minimally invasive treatment that can slow or stop the progression of the condition. Recent research has also explored the use of copper sulfate eye drops (IVMED-80) as a noninvasive treatment to prevent the progression of KCN. Current treatment options for visual improvement include scleral lenses, intracorneal ring segments, corneal allogeneic intrastromal ring segments, and deep anterior lamellar keratoplasty. Recently, novel alternative procedures, such as isolated Bowman layer transplantation, either as a corneal stromal inlay or onlay, have demonstrated encouraging outcomes. Artificial intelligence has gained acceptance for providing best practices for the diagnosis and management of KCN, and the science of its application is contentiously debated; however, it may not have been sufficiently developed.

Conclusions

Early detection and advancements in screening methods using current imaging modalities have improved diagnosis of KCN. Improvement in the accuracy of current screening or diagnostic tests and comparison of their validities are achievable by well-designed, large-scale, prospective studies. The safety and effectiveness of emerging treatments for KCN are currently being investigated. There is an ongoing need for studies to track progress and evaluate clinicians' knowledge and practices in treating patients with KCN. Artificial intelligence capabilities in management approach considering the currently available imaging modalities and treatment options would best benefit the patient.

Main issues in deep anterior lamellar keratoplasty: A systematic narrative review

Deep anterior lamellar keratoplasty (DALK) has emerged as a transformative approach in managing corneal pathologies, notably keratoconus (KC), providing a viable alternative to penetrating keratoplasty (PK). This systematic review explores the intricacies of DALK, comparing its preoperative, intraoperative, and postoperative considerations with PK. Extensive literature searches revealed a wealth of data regarding DALK's advantages and challenges, with an emphasis on graft survival, visual outcomes, and complications. In the preoperative phase, DALK showcases its versatility, catering to a wide spectrum of patients, including those with KC and ocular surface disorders. Intraoperatively, it offers innovative techniques to address emphysema, bubble formation, and Descemet's membrane perforation, all while maintaining a strong focus on patient-centered outcomes. Postoperatively, DALK's lower rejection rates and decreased complications underscore its potential superiority over PK, although unique challenges such as graft failure from nonimmunologic factors demand vigilant management. This comprehensive review not only serves as a valuable resource for ophthalmic surgeons but also sheds light on the evolving landscape of corneal transplantation, highlighting DALK's role as a transformative force in the field.

Impact of topographic localization of corneal ectasia on the outcomes of deep anterior lamellar keratoplasty employing large (9 mm) versus conventional diameter (8 mm) grafts

OBJECTIVES

Visual and topographic outcomes of large (9.0 mm) versus conventional (8.0 mm) deep anterior lamellar keratoplasty (DALK) for the treatment of keratoconus (KC) were compared in relation to the different localization of the corneal ectasia (within or beyond the central 8.0 mm).

METHODS

This is a retrospective, comparative case series. Preoperatively, the topographic extension of the conus was calculated by measuring the distance from the geometric center of the cornea and the outermost point of the corneal ectasia (ectasia <8.0 mm, group A; ectasia ≥8.0 mm, group B). DALK was performed using both small grafts (8.0 mm, group 1) and large grafts (9.0 mm, group 2). Best-corrected visual acuity and topographic astigmatism were evaluated preoperatively (T0) and postoperatively after complete suture removal (1 year, T1).

RESULTS

Data from 224 eyes of 196 patients (mean age 37.6 ± 15.1 years) were evaluated. Topographic astigmatism improved from T0 to T1 (4.94 ± 2.92 diopters (D) [95% CI, 4.56-5.33] vs 4.19 ± 2.45 D [95% CI, 3.87-4.51], p = 0.001). There was no significant difference in postoperative topographic cylinder between group 1 and group 2 when considering eyes with corneal ectasia <8.0 mm (group 1 A, 4.15 ± 2.19 D [95% CI, 3.64-4.66] vs group 2 A, 3.65 ± 2.13 D [95% CI, 2.92-4.38], p = 0.14); conversely, the difference was significant considering eyes with corneal ectasia ≥8.0 mm (group 1B, 4.74 ± 2.90 D [95% CI, 4.09-5.38] vs group 2B, 3.68 ± 1.94 D [95% CI, 3.10-4.26], p = 0.02).

CONCLUSIONS

Large 9.0-mm DALK provided better anatomical outcomes compared to conventional 8.0-mm DALK, particularly in eyes with corneal ectasia extending beyond the central 8.0 mm.

Effects of femtosecond laser-assisted minimally invasive lamellar keratoplasty (FL-MILK) on mild-to-moderate and advanced keratoconus

PURPOSE

To compare the outcomes of femtosecond laser-assisted minimally invasive lamellar keratoplasty (FL-MILK) for mild-to-moderate keratoconus (KC) and advanced KC.

METHODS

Prospective case series study. Sixty-three eyes of 56 patients with progressive KC underwent FL-MILK were divided into group 1 [mean keratometry (Kmean) ≤ 53D] and group 2 (Kmean > 53D). Best spectacle-corrected visual acuity (BSCVA), Kmean, maximum keratometry (Kmax), anterior central corneal elevation (ACE), stiffness parameter A1 (SP-A1) and deformation amplitude (DA) were evaluated preoperatively and up to 24 months postoperatively.

RESULTS

Mean BSCVA improved from 0.34 ± 0.13 logMAR preoperatively to 0.25 ± 0.13 logMAR at 24 months postoperatively in group 1 (F = 10.10, P < .0001), and from 0.54 ± 0.31 logMAR to 0.40 ± 0.26 logMAR (F = 9.06, P = .0002) in group 2. Group 2 showed an average Kmax reduction of 10.9 D and an average Kmean reduction of 3.9 D at 24 months postoperatively (both P < .0001), whereas no significant change was observed in group 1. Average ACE decreased from 19.2 ± 10.0 to 5.2 ± 8.4 at 24 months postoperatively in group 1 (F = 28.5, P < .0001), and from 46.2 ± 16.3 to 19.1 ± 9.0 (F = 49.6, P < .0001) in group 2; SP-A1 increased from 53.8 ± 12.7 mmHg/mm to 95.9 ± 20.2 mmHg/mm in group 1 (F = 70.0, P < .0001), and from 38.6 ± 13.4 mmHg/mm to 89.3 ± 18.2 mmHg/mm (F = 96.9, P < .0001) in group 2; DA decreased from 1.30 ± 0.14 mm to 1.17 ± 0.13 mm in group 1 (F = 14.0, P < .0001), and from 1.40 ± 0.16 mm to 1.18 ± 0.10 mm (F = 27.6, P < .0001) in group 2.

CONCLUSIONS

FL-MILK can stabilize progressive KC in mild-to-moderate cases and advanced cases at 24-month follow-up. Steeper corneas are more likely to undergo flattening after FL-MILK.

CLINICAL TRIAL

Date of registration: July 16, 2017. The title of the trail: www.

CLINICALTRIALS

gov Trial registration number: NCT03229239. The name of the trial registry: ClinicalTrials.gov.