Eyeworld

16 August 2018 EW NEWS & OPINION by Vanessa Caceres EyeWorld Contributing Writer found that patients with glaucoma had higher bacterial oral counts compared with controls (P<0.017) and that low-dose LPS administra- tion in glaucoma animal models resulted in enhancement of axonal degeneration and neuronal loss. "Microglial activation in the optic nerve and retina as well as upregula- tion of TLR4 signaling and comple- ment system were observed. Phar- macologic blockade of TLR4 partially ameliorated the enhanced damage," the researchers wrote. The finding that commensal bacteria may have a role in glaucoma pathology could be relevant to other chronic neurode- generative disorders, the researchers concluded. Uveitis and ocular inflammatory disease A review article concluded that intestinal microbiota are potentially crucial in propagating inflamma- tory diseases of the eye and can be targeted for therapeutic benefit. 5 The author shares how several research- ers have shown the importance of the intestinal microbiome in the pathogenesis of uveitis and that in some studies, alteration of the mi- crobiota with oral antibiotics led to decreased uveitis severity. Yet other researchers showed that a com- mensal bacterial antigen activates retina-specific autoreactive T cells, which may indicate a commensal uveitis trigger. "Strategies that might be effective for targeting the intesti- nal microbiota might involve several approaches, including the use of antibiotics, drugs that supplement beneficial bacterial components or target inflammatory bacterial strains, dietary strategies, or microbial trans- plantation," Lin concluded. Contact lens wear and ocular microbiota To help determine if contact lens wear is associated with ocular micro- biota changes, Shin et al. compared the bacterial communities of the conjunctiva and skin under the eye from 58 subjects. 6 Dry conjunctival swabs from contact lens wearers had more variable and skin-like bacterial community structures, with a higher cally, researchers tested Lactobacillus gasseri KS-13, Bifidobacterium bifidum G9-1, and Bifidobacterium longum MM-2 as a probiotic capsule com- pared with placebo to measure the effects on the Mini Rhinoconjunc- tivitis Quality of Life Questionnaire (MRQLQ). There were 173 partic- ipants in the study. There was an improvement in the MRQLQ global score from baseline to pollen peak in the probiotic group (–0.68) com- pared with the placebo group (–0.19; P=0.0092). The associated mecha- nism for how the probiotics helped patients was unclear to researchers. Glaucoma The findings of a study from Astafurov et al. suggested that the oral microbiome may contribute to glaucoma pathophysiology. 4 The researchers used mouthwash specimens from glaucoma and control subjects and analyzed them for the amount of bacteria. Also in the study, low-dose subcutaneous lipopolysaccharide (LPS) was given in two separate animal models of glaucoma to determine a possible pathogenic mechanism. Researchers also assessed glaucomatous neuro- degeneration in the retina and optic nerve 2 months later and analyzed changes in gene expression of toll- like receptor (TLR) 4 signaling path- way and complement along with microglial numbers and morphology in the retina and optic nerve. They ing dry eye syndrome, according to Chisari et al. 1 They used a mix of Saccharomyces boulardii MUCL 53837 and Enterococcus faecium LMG S-28935 and after a run-in period, randomized patients into a control group (n=30) receiving a substitute tear and a treatment group (n=30) receiving the substitute tear and the probiotic. Schirmer test I and II test results improved in the treatment group, and there was a reduction in bacterial growth strains. In a prospective, cross-sectional study by Watters et al. that focused on meibomian gland dysfunction (MGD), 157 participants were clas- sified as normal or as having mild or moderate to severe MGD. 2 Lid margin swabs both before and after gland expression were isolated and identified. Both participants with and without MGD showed a similar microbiome; there also was a higher incidence of Staphylococcus aureus than anticipated across all severity groups. "Similarity in microbiome profile, irrespective of meibomian gland dysfunction severity, anterior blepharitis presence, or contact lens wear suggests potential for common- ality in treatment," the researchers wrote. Rhinoconjunctivitis A group of individuals using pro- biotics had an improvement in rhinoconjunctivitis-specific quality of life during allergy season. 3 Specifi- Does current research provide insights to help with treatment of common eye problems? G rowing knowledge about the human microbiome has provided insights into bowel disease, autoim- mune conditions, glyce- mic control, and a variety of other areas. "The human microbiome has benefited from probiotic research that preceded it, as it provided a basis to go and examine the micro- bial contents of human sites," said Gregor Reid, PhD, chair of human microbiology and probiotics, Law- son Health Research Institute, and professor of microbiology & immu- nology and surgery, University of Western Ontario, London, Canada. Dr. Reid has studied probiotics for 35 years. "The Human Microbiome Proj- ect told us exactly what we expect- ed, that humans harbor many mi- crobes and the composition differs in all of us, while many functions are shared," Dr. Reid explained. Yet are there any implications within microbiome research for eye health? Although the number of studies is still small, some researchers are discovering more about the ocular microbiome and its effects on dry eye disease, uveitis, infection, and other ocular conditions. Last month, EyeWorld described how human microbiome research has slowly moved its way into ocular research. This month, EyeWorld shares more examples of studies that focus on the eye's microbiome and specific implications, both present and future, for ophthalmology. Here is a sampling of the research under- way to investigate the ocular micro- biome and its effects on specific eye diseases and conditions. Dry eye and MGD A pilot study that evaluated the effects of probiotic supplementa- tion on the tear film found that the strains were effective in reduc- Eyeing the ocular microbiome " The opportunity to reduce inflammation, improve healing, and potentially deliver treatments for various conditions exists, but it will require low doses to be used, and only after safety is assured. " —Gregor Reid, PhD

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