In Vitro Antifungal Effect of Acrylic Corneal Glue (N-Butyl-2-Cyanoacrylate)

Breaking-Down Barriers: Proposal of Using Cellulose Biosynthesis Inhibitors and Cellulase Enzyme as a Novel Treatment Modality for Vision Threatening Pythium Insidiosum Keratitis

Pythium insidiosum, an Oomycete, causes severe keratitis that endangers vision. Its clinical, morphological, and microbiological characteristics are often indistinguishable from those of fungal keratitis, earning it the moniker "parafungus". Distinctive clinical hallmarks that set it apart from other forms of keratitis include radial keratoneuritis, tentacles, marginal infiltration, and a propensity for rapid limbal spread. The therapeutic approach to Pythium keratitis (PK) has long been a subject of debate, and topical and systemic antifungals and antibacterials have been tried with limited success. Approximately 80% of these eyes undergo therapeutic keratoplasty to salvage the eye. Hence, there is a need to innovate for alternative and better medical therapy to safeguard these eyes. The resistance of Pythium to standard antifungal treatments can be attributed to the absence of ergosterol in its cell wall. Cell walls of plants and algae have cellulose as an essential constituent. Cellulose imparts strength and structure and acts as the "skeleton" of the plant. Fungal and animal cell walls typically lack cellulose. The cellular architecture of Pythium shares a similarity with plant and algal cells through the incorporation of cellulose within its cell wall structure. Inhibitors targeting cellulose biosynthesis (CBI), such as Indaziflam, Isoxaben, and Quinoxyphen, serve as critical tools for elucidating the pathways of cellulose synthesis. Furthermore, the enzymatic action of cellulase is instrumental for the extraction of proteins and DNA. To circumvent this issue, we hypothesize that CBI's and cellulase enzymes can act on the Pythium cell wall and may effectively treat PK. The available literature supporting the hypothesis and proof of concept has also been discussed. We have also discussed these drugs' molecular mechanism of action on the Pythium cell wall. We also aim to propose how these drugs can be procured and used as a potential medical management option for this devastating entity.

Alternaria fungus growing on top of cyanoacrylate glue in a patient with perforated corneal ulcer

Purpose

To demonstrate a case where Alternaria fungus grew on top of cyanoacrylate glue used to seal a perforated corneal ulcer.

Observations

We document the clinical course of a rare case of Alternaria keratitis over the course of 6 months. Despite the purported antifungal properties of cyanoacrylate glue demonstrated in vitro, this case provides in vivo evidence that this substance can serve as a scaffold on which pathogenic fungi may grow.

Conclusion

This report demonstrates the importance of close follow up of patients with corneal glue patches in place. Ophthalmologists should continue to inspect the cornea and glue for possible development of secondary infection, particularly with concomitant contact lens and/or steroid use.

Update on the management of fungal keratitis

PURPOSE

The aim of this article is to introduce the recent advance on the studies of fungal keratitis published over past 5 years.

METHODS

We performed literature review of articles published on PubMed, Google Scholar, CNKI and Web of Science relevant to the diagnosis, pathogenesis and novel treatment of fungal keratitis.

RESULTS

Excessive inflammation can lead to stromal damage and corneal opacification, hence the research on immune mechanism provides many potential therapeutic targets for fungal keratitis. Many researchers discussed the importance of earlier definitive diagnosis and were trying to find rapid and accurate diagnostic methods of pathogens. Develop new drug delivery systems and new routes of administration with better corneal penetration, prolonged ocular residence time, and better mucoadhesive properties is also one of the research hotspots. Additionally, many novel therapeutic agents and methods have been gradually applied in clinical ophthalmology.

CONCLUSION

The diagnosis and treatment of fungal keratitis are still a challenge for ophthalmologist, and many researches provide new methods to conquer these problems.

Surgical alternatives to keratoplasty in microbial keratitis

Penetrating keratoplasty is often required in microbial keratitis not responding to the standard treatments available or the development of complications like corneal perforation. Performing keratoplasty in microbial keratitis has several challenges, the major ones being the availability of donor corneal tissue and the poor success of the corneal graft performed in such a setting. For overcoming these challenges, several alternatives to keratoplasty have been described. Broadly, these options could be categorized into autologous tissues such as conjunctival and tenon tissue, synthetic products like tissue adhesives and therapeutic contact lenses, or biological tissues like amniotic membrane graft. These alternative modalities are not universal. They have their specific indications in microbial keratitis. Most of these alternatives are useful only for small corneal perforations. While autologous tissues are cost-effective and readily available, lack of tectonic support is a significant limitation. Tissue adhesives are excellent alternatives in terms of tectonic support, but surface irregularity and tissue reaction are their potential limitations. The amniotic membrane is useful for small corneal perforations, but availability, cost, and poor tectonic support restrict its use. Herein, we discuss these various alternatives to keratoplasty in microbial keratitis, their indications, advantages, disadvantages, and the various techniques of performing these procedures.

Efficacy of cyanoacrylate tissue adhesive in the management of corneal thinning and perforation due to microbial keratitis

PURPOSE

Report the efficacy of cyanoacrylate tissue adhesive (CTA) application in the management of corneal thinning and perforations associated with microbial keratitis.

METHODS

A retrospective review of consecutive patients who underwent CTA application for corneal thinning and perforation secondary to microbiologically proven infectious keratitis between 2001 and 2018 at a single center. We defined successful CTA application as an intact globe without tectonic surgical intervention.

RESULTS

The cohort included 67 patients, and 37 presented with corneal perforation while 30 had corneal thinning. The perforation/thinning was central/paracentral in 43 eyes and peripheral in 23 eyes. The underlying infectious etiologies were monomicrobial in 42 cases (35 bacterial, 3 fungal, 2 viral, and 2 acanthamoeba cases) and polymicrobial in 25 cases (22 polybacterial cases and 3 cases with a combination of Gram positive bacteria and fungus). The median duration of glue retention was 29 days. The CTA success rate was 73%, 64%, and 44% at 10, 30, and 180 days, respectively. CTA application appears more successful in monomicrobial (vs. polymicrobial) and Gram positive bacterial (vs. Gram negative) keratitis but the differences are statistically non-significant. The location of perforation/thinning and the use of topical corticosteroid were not associated with CTA failure.

CONCLUSION

CTA was moderately effective in restoring globe integrity in severe corneal thinning and perforation secondary to microbial keratitis in the short term. However the majority of patients require tectonic surgical intervention within 6 months. CTA application success is not significantly associated with the location of thinning/perforation or the use of topical corticosteroid.