Comparative profile of ocular surface microbiome in vernal keratoconjunctivitis patients and healthy subjects

The Microbiome, Ocular Surface, and Corneal Disorders

The ocular surface microbiome is an emerging field of study that seeks to understand how the community of microorganisms found on the ocular surface may help maintain homeostasis or can potentially lead to disease and dysbiosis. Initial questions include whether the organisms detected on the ocular surface inhabit that ecological niche and, if so, whether there exists a core microbiome found in most or all healthy eyes. Many questions have emerged around whether novel organisms and/or a redistribution of organisms play a role in disease pathogenesis, response to therapies, or convalescence. Although there is much enthusiasm about this topic, the ocular surface microbiome is a new field with many technical challenges. These challenges are discussed in this review as well as a need for standardization to adequately compare studies and advance the field. In addition, this review summarizes the current research on the microbiome of various ocular surface diseases and how these findings may impact treatments and clinical decision-making.

Role of the ocular surface microbiome in allergic eye diseases

PURPOSE OF REVIEW

The purpose of this review is to provide an update on emerging literature on the role of the ocular surface microbiome (OSM) in allergic eye diseases.

RECENT FINDINGS

Findings in the literature suggest that the ocular surface microbiome plays a role in the pathophysiology and course of allergic disease of the ocular surface.

SUMMARY

Knowledge regarding the role of the ocular surface microbiome in allergic disease is important to guide development of targets for future therapeutic interventions.

Vernal Keratoconjunctivitis: A Systematic Review

Vernal keratoconjunctivitis (VKC) is a chronic, bilateral corneal and conjunctival problem which typically presents in young individuals. VKC is characterized by itching, photophobia, white mucous discharge, lacrimation, foreign body sensation, and pain due to corneal involvement of shield ulcers. Vernal keratoconjunctivitis is categorized within ocular diseases. The diagnosis is clinical, as no sure biomarkers pathognomonic of the disease have yet been identified. The VKC therapy relies on different types of drugs, from antihistamines and topical steroids to cyclosporine or tacrolimus eye drops. In extremely rare cases, there is also the need for surgical treatment for the debridement of ulcers, as well as for advanced glaucoma and cataracts, caused by excessive prolonged use of steroid eye drops. We performed a systematic review of the literature, according to PRISMA guideline recommendations. We searched the PubMed database from January 2016 to June 2023. Search terms were Vernal, Vernal keratoconjunctivitis, and VKC. We initially identified 211 articles. After the screening process, 168 studies were eligible according to our criteria and were included in the review. In this study, we performed a systematic literature review to provide a comprehensive overview of currently available diagnostic methods, management of VKC, and its treatments.

Conjunctival Autograft for Tarsal Keratinization in a Case of Chronic Vernal Keratoconjunctivitis

This report describes the clinical features and management in a case of vernal keratoconjunctivitis (VKC) with bilateral tarsal conjunctival keratinization. A 32-year-old male presented with VKC since childhood that had exacerbated in the eight years prior to presentation. Examination revealed partial limbal stem cell deficiency in both eyes, with keratinization of the superior tarsal conjunctiva. The corresponding areas of the cornea exhibited punctate keratopathy in both eyes. To address this, the patient underwent excision of the conjunctival keratinization in both eyes. The resultant bare areas were covered with conjunctival autografts (CAGs). Postoperatively, the grafts were well apposed, and there was no recurrence of keratinization observed during the period of follow-up of four years. Resolution of corneal epitheliopathy was also noted. Although keratinization can occur in eyes with VKC, it is usually limited to the bulbar conjunctival areas. This is the first report of tarsal conjunctival keratinization in such cases. Milder cases may be observed or managed with scleral contact lenses. In more severe forms, there is associated corneal epitheliopathy, which may progress to corneal vascularization and scarring. Surgical excision of the lesion is recommended in these eyes. Following excision, several options exist to cover the bare area, which include a CAG, an amniotic membrane, or an oral mucous membrane. Of these, a CAG is an autologous tissue that can be harvested with a simple surgical technique and yields stable long-term results. Thus, tarsal conjunctival keratinization is a rare complication of chronic VKC. Excision of the lesion followed by a CAG is a viable approach for treatment, which reestablishes and maintains a stable ocular surface.

Characterization of Conjunctival Sac Microbiome from Patients with Allergic Conjunctivitis

Conjunctival sac microbiome alterations have been reported to be closely associated with many ocular diseases. However, the characteristic of conjunctival sac microbiome in allergic conjunctivitis (AC) was scarcely described. In this study, we aimed to identify the differences of the conjunctival sac microbiome composition in AC patients compared with normal controls (NCs) using high-throughput 16S rDNA sequencing metagenomic analysis. The conjunctival sac microbiome samples from 28 AC patients and 39 NC patients were collected. The V3-V4 region of 16S rRNA gene high-throughput sequencing was performed on the illumina MiSeq platform. Alpha diversity, beta diversity and the relative abundance at the phylum and genus levels were analyzed using QIIME. Alpha diversity demonstrated by Chao1, Observed_species and PD_whole_tree indexes did not show significant difference between the AC and NC groups, while the Shannon index was higher in the AC group. Beta diversity showed divergent microbiome composition in different groups (p < 0.005). The top five abundant phyla were Firmicutes, Proteobacteria, Actinobacteriota, Bacteroidota and Cyanobacteria in both groups. The top five abundant genera were Bacillus, Staphylococcus, Corynebacterium, Acinetobacter and Ralstonia in the AC group and Acinetobacter, Staphylococcus, Bacillus, Clostridium_sensu_stricto_1, Corynebacterium and Geobacillus in the NC group. The Firmicutes/Bacteroidetes (F/B) ratio at the phylum level was similar between groups (p = 0.144). The Bacillus/Acinetobacter (B/A) ratio at the genus level was higher in the AC group (p = 0.021). The dysbiosis detected in this study might provide further evidence to investigate the mechanism and treatment methods for allergic conjunctivitis.

Review of Loteprednol Etabonate 0.5%/Tobramycin 0.3% in the Treatment of Blepharokeratoconjunctivitis

Use of a combination corticosteroid and antibiotic in a single formulation is common in the treatment of ocular inflammatory conditions for which corticosteroid therapy is indicated and there exists a risk of superficial bacterial infection. Loteprednol etabonate (LE) is a corticosteroid engineered to maintain potent anti-inflammatory activity while minimizing the risk of undesirable class effects of corticosteroids, such as elevated intraocular pressure and cataract. Tobramycin is a broad-spectrum aminoglycoside antibiotic that is considered generally safe and well tolerated. An ophthalmic suspension combining LE 0.5% and tobramycin 0.3% (LE/T) is approved in the US and several other countries. Use of a combination therapy increases convenience, which may promote patient adherence. A systematic literature review was conducted to examine the efficacy and safety of LE/T for ocular inflammatory conditions within the scope of its labeled indications. Results of published studies indicate that LE/T is effective in the treatment of blepharokeratoconjunctivitis in adults, with similar efficacy as dexamethasone 0.1%/tobramycin 0.3%, but is associated with a lower risk of clinically significant increases in intraocular pressure as demonstrated in both efficacy and safety studies and studies with healthy volunteers. Furthermore, studies in children with blepharitis or blepharoconjunctivitis indicate LE/T was well tolerated in this population, although efficacy vs vehicle was not demonstrated, potentially due to improvements in all groups overall and/or limited sample size. Separately, tobramycin demonstrated potent in vitro activity against most bacterial species associated with blepharitis. In conclusion, published data demonstrate the utility of LE/T for the treatment of the various clinical manifestations of blepharokeratoconjunctivitis in adults.