Current techniques of lamellar keratoplasty for keratoconus

[Effect of keratoplasty on the quality of life of keratoconus patients]

Corneal deformations caused by keratoconus produce high levels of optical aberration (OA). Despite appropriate optical correction, these alter the quality of vision and diminish the patient's quality of life, especially since the affected population is predominantly young and of working age. When thinning is too severe or corneal transparency too impaired, a corneal transplant may be considered. In this study, we compare the quality of life of patients with keratoconus in the early (stages 1 and 2) or advanced (stages 3 and 4) stages of the Krumeich classification, as well as patients who have had keratoconus treated by keratoplasty. Quality of life was assessed using the NEI-VFQ 25 questionnaire, the most widely used for keratoconus. An aberrometric examination (OQAS®; HD Analyser, Visiometrics, Terrassa, Spain) was also performed to assess patients' quality of vision. Our results show that keratoplasty provides an improvement in quality of life compared with advanced-stage keratoconus in the areas of distance (p=0.0083) and near vision (p=0.029) activities. This improvement also applies to Best-Corrected Visual Acuity (BCVA) (p=0.032) and transparency (OSI) (p=0.049). Our study shows that keratoplasty improves corneal transparency, and it is interesting to note that it improves patients' quality of life over the long term.

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.

Visual Outcomes of Microkeratome-Assisted Anterior Lamellar Keratoplasty in Keratoconus: 5-Year Results

Purpose

To report 5-year results of microkeratome-assisted anterior lamellar keratoplasty (MK-ALK) in cases of keratoconus.

Methods

Patients with advanced keratoconus and the thinnest corneal location 300 μ or more were recruited. A Carriazo–Barraquer microkeratome was used to remove a 200-μ cap from the recipient cornea, and to prepare a 300-μ anterior stromal graft from a donor cornea. A full-thickness crescentic incision was made in the posterior stromal recipient bed using a 6.5-mm suction trephine. The donor was sutured to the recipient bed using interrupted nylon sutures. The minimum follow-up was five years.

Results

Twelve eyes of 12 patients were included. The mean age was 26 ± 8 years. None of the patients required conversion to penetrating keratoplasty. Mean logMAR uncorrected and best spectacle-corrected visual acuity, respectively, improved from 1.56 ± 0.24 and 1.18 ± 0.32 preoperatively, to 0.63 ± 0.38 and 0.18 ± 0.12, five years after surgery (P=0.001for both). There was also a statistically significant reduction of mean manifest spherical equivalent, refractive cylinder, and mean keratometry readings. Posterior stromal striations occurred in all patients immediately after surgery but resolved after a maximum of 3 months. At five-years, anterior segment optical coherence tomography revealed a clear interface in all cases and a mean graft thickness of 328 ± 27 μ.

Conclusion

MK-ALK is a safe and effective procedure for advanced keratoconus. Where feasible, it may be the best choice for patients at high risk of poor outcomes with penetrating keratoplasty, such as young patients with atopic keratoconjunctivitis or Down's syndrome.

Dendrimer as a momentous tool in tissue engineering and regenerative medicine

Dendrimers have been comprehensively used for cargo delivery, nucleic acid delivery (genes, miRNA/siRNAs), delivery of macromolecules, and other various biomedical applications. Dendrimers are highly versatile in function and can be engineered as multifunctional biomacromolecules by modifying the surface for fulfilling different applications. Dendrimers are being used for crosslinking of existing synthetic and natural polymeric scaffolds to regulate their binding efficiency, stiffness, biocompatibility, transfection, and many other properties to mimic the in vivo extracellular matrix in tissue engineering and regenerative medicine (TERM). Dendritic inter-cellular linkers can enhance the linkages between cells and result in scaffold-independent tissue constructs. Effectively engineered dendrimers are the ideal molecules for delivering bioactive molecules such as cytokines, chemokines, growth factors, etc., and other metabolites for efficaciously regulating cell behavior. Dendrimeric nanostructures have shown tremendous results in various TERM fields like stem cells survival, osteogenesis, increased crosslinking for eye and corneal repair, and proliferation in cartilage. This review highlights the role and various aspects of dendritic polymers for TERM in general and with respect to specific tissues. This review also covers novel explorations and insights into the use of dendrimers in TERM, focusing on the developments in the past decade and perspective of the future.

Effects of Perceptual Learning on Deprivation Amblyopia in Children with Limbal Dermoid: A Randomized Controlled Trial

Limbal dermoid (LD) is a congenital ocular tumor that causes amblyopia and damages visual acuity (VA) and visual function. This study evaluated the therapeutic efficacy of perceptual learning (PL) toward improving contrast sensitivity function (CSF) and VA. A total of 25 children with LD and 25 normal children were compared in terms of CSF and VA. The LD group was further randomly allocated into two arms: nine underwent PL combined with patching and eight underwent patching only; eight patients quit the amblyopia treatment. The primary outcome was the area under log CSF (AULCSF), and the secondary outcome was the best corrected VA (BCVA). The CSF was obviously reduced in the LD group compared with that in the normal group. Moreover, the difference in the changes in the AULCSF between the PL and patching groups after 6 months of training was 0.59 (95% CI: 0.32, 0.86, p < 0.001), and the between-group difference in VA at 6 months was −0.30 (95% CI: −0.46, −0.14, p < 0.001). Children suffering from LD with amblyopia exhibited CSF deficits and VA loss simultaneously. PL could improve CSF and VA in the amblyopic eye better than patching.

Biomechanical Effects of Deep Anterior Lamellar Keratoplasty and Penetrating Keratoplasty for Keratoconus: A Finite Element Analysis

Purpose

To theoretically compare corneal displacement and the von Mises (VM) stress distribution of deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) for keratoconus (KC) and to evaluate the effects of residual stromal thickness (RST) and intraocular pressure (IOP) on postoperative corneal biomechanics.

Methods

We performed DALK and PK simulations using Ansys by employing anisotropic nonlinear hyperelastic corneal material properties. We analyzed corneal displacement and VM stress in DALK and PK models under IOPs of 10, 15, 20, and 25 mmHg. We established two DALK models: The ideal-type DALK ensured that postoperative central corneal thickness was constant at 560 µm and the corneal graft thickness varied with RST. The clinical-type DALK ensured that corneal grafts had the same thickness (500 µm) regardless of RST. Then we analyzed the effects of RST and IOP on postoperative corneal displacement and VM stress.

Results

Corneal displacement and VM stress were lower in the DALK than in the PK model. In the ideal-type DALK model, an increase in RST was associated with increased deformation and decreased VM stress in the healing zone, except for a RST of 0 µm. In the clinical-type DALK model, deformation and VM stress in the healing zone decreased with an increase in RST, except for a RST of 0 µm.

Conclusions

DALK showed more stability than PK. For the ideal-type DALK model, an increase in RST resulted in decreased postoperative corneal biomechanics in the healing zone. For the clinical-type DALK model, corneal deformation and VM stress decreased with an increase in RST, which provides numerical evidence for the design of corneal transplantation for patients with KC.

Translational Relevance

In this computational modeling study, we first theoretically compared corneal biomechanics between DALK and PK for KC. Then, the effects of RST and IOP on postoperative corneal biomechanics were investigated. Our findings provide novel insights into the optimal design for corneal transplantation for patients with KC.

[Study of the antiviral activity of the liquid corneal storage medium in relation to the herpes simplex virus in vitro]

The aim of the study was to assess the antiviral activity of the 7 types of liquid corneal storage medium on an experimental model of herpesvirus infection in vitro.

MATERIAL AND METHODS

The study of antiviral activity of 7 samples of liquid corneal storage medium on a model of herpesvirus infection caused by the herpes simplex virus type 1 in Vero-cell using virological and statistical research methods was carried out.

RESULTS AND DISCUSSION

All the studied images of the corneal storage medium, including the Borzenka-Moroz base medium, did not have a cytotoxic effect on Vero cell culture. Out of of 7 samples of liquid corneal storage medium, 4 samples had reliable antiviral activity against HSV-1 when used under the therapeutic regimen (1 hour after infection) and under the preventive regimen (2 hours before infection). Antiviral activity was established in 2 samples containing the interferon inducer cycloferon at a concentration of 10 mg/kg and 30 mg/kg (sample 2, 3), in a sample containing the interferon inducer gamapren 15 mg/kg (sample 5), and in a sample containing a combination of drugs - 10 mg/kg cycloferon and an acyclic nucleoside analog-acyclovir 10 mg/kg (sample 6). According to the results of 2 test regimens, the maximum statistically significant inhibitory effect in relation to HSV-1 was detected in sample 6, containing a combination of drugs. Against the background of sample 6, the infectious activity of the test virus decreased by an average of 3.2 lg, the inhibition coefficient was 54.5%.

CONCLUSION

The results of the study indicate the prospects of using types of media with antiviral activity (samples 2, 3, 5, 6) for storing donor corneas in order to increase the effectiveness of keratoplasty in patients with ophthalmic herpes.

Comparison of femtosecond laser-assisted corneal intrastromal xenotransplantation and the allotransplantation in rhesus monkeys

Background

In our previous study, we showed that both allogeneic and autogeneic small-incision femtosecond laser-assisted corneal intrastromal transplantation are safe and effective surgeries. However, the results of small-incision femtosecond laser-assisted intrastromal xenotransplantation have not yet been explored. Additionally, we suggest that glycerol-dehydrated corneal lamellae might provide a possible alternative for this xenogenic implantation approach.

Methods

Corneal inlay lamellae were produced from rabbits and humans using femtosecond laser-assisted surgeries and were dehydrated in glycerol for 1 week at 4 °C. These xenogeneic glycerol-dehydrated grafts and fresh allogeneic monkey lamellae were then implanted into rhesus monkeys using small-incision femtosecond laser assistance. Postoperatively, clinical examinations, AS-OCT measurements and tear inflammatory mediator assays were performed.

Results

There were no significant changes in the transparency of the corneal lamellae after glycerol dehydration. Following implantation, no evidence of tissue rejection or severe inflammatory responses was observed in the monkeys, and the host corneas remained transparent throughout a 6-month observation period. The grafts were clearly visible via AS-OCT. Corneal thickness increased 1 week postoperatively but subsequently declined and remained unchanged 1 month after surgery. Significant changes were observed in all tear inflammatory mediators in the ‘Rabbit to Monkey’ group. The trends in changes of tear inflammatory mediators in the ‘Human to Monkey’ group were similar to those in the ‘Rabbit to Monkey’ group. At 1 month post-surgery, the levels of most tear inflammatory mediators had decreased, with the exception of IL-1β, TGF-β1 and IFN-γ in the allotransplantation group.

Conclusion

Small-incision femtosecond laser-assisted intrastromal transplantation minimized invasiveness and improved surgical efficiency. In addition, the host cornea maintained a high level of biocompatibility. Glycerol-dehydrated corneal lamellae might be potentially useful as an alternative inlay xenogeneic material. In this study, we also describe a new treatment that can be used in keratoconus, corneal ectasia, presbyopia, hyperpresbyopia and other diseases.