June 30, 2021

The most important ophthalmology research updates, delivered directly to you

Innate Immunity at the Blood-Retina Barrier


Blood-borne pathogens beware! The neuroretinal barrier has long been viewed as the gatekeeper to maintaining ocular immune privilege (if you’re curious, read more about it here). Physical barriers are part of our first-line defense against invading pathogens, a key feature of innate immunity. Another important aspect of innate immunity is the production of antimicrobial peptides such as lysozyme, found in blood, saliva, tears, and mucosal surfaces among other bodily fluids. Lysozyme breaks down peptidoglycan, an important component of bacterial cell walls causing bacterial lysis. It also has antiviral properties. In this study, researchers sought to evaluate the level of expression of lysozyme at the blood-retina barrier and determine its role in bacterial killing and immune activation. Lysozyme mRNA and protein were detected in both mouse and human RPEs with enhanced lysozyme expression following treatment with compounds known to trigger innate immune signaling (LPS, Pam3CSK4, Poly(I:C), S, aureus peptidoglycan). Deletion of lysozyme in ARPE19 cells reduced their ability to respond to LPS and impaired bactericidal activity. These findings provide more insight into the immunological barrier that protects the neuronal retina from invading pathogens. Production of antimicrobial peptides such as lysozyme not only defend pathogens but could also serve as key players in modulating the immune response at the critically important blood-retina barrier.

Pneumatic Retinopexy for Retinal Detachment Repair

JAMA Ophthalmology

Do intraocular gas bubbles have 'inflated' rates of rhegmatogenous retinal detachment (RRD) repair? Pneumatic retinopexy (PR) is the only non-surgical option for RRD repair. In this clinic-based procedure, a gas bubble is injected into the vitreous chamber, apposing the detached neurosensory retina with underlying retinal pigment epithelium, allowing for adhesion and healing. A retrospective cohort study of 9,659 eyes treated with PR for uncomplicated RRD investigated the rate of single-operation success (SOS), defined as successful reattachment without subsequent surgery for RRD or repeat PR, and factors that influence this metric. A total of 6,613 eyes (68.5%) in this study achieved SOS. The odds of SOS were higher in female patients (OR 1.51, 95% CI 1.38-1.65) and lower in current smokers (OR 0.78, 95% CI 0.68-0.91). Visual acuity 9-12 months following PR was better in patients who achieved SOS (0.24 logMAR, approx. Snellen equivalent 20/35) compared to those who did not (0.43 logMAR, approx. Snellen equivalent 20/54). Few adverse outcomes were reported, with endophthalmitis occurring in 3 eyes (0.03%), vitreous hemorrhage in 307 eyes (3.2%), metamorphopsia in 14 eyes (0.1%), and epiretinal membrane formation in 2,367 eyes (24.5%). Although this study did not directly compare PR with surgical approaches, these results indicate that PR is a safe and efficacious option for RRD repair with favorable visual outcomes regardless of SOS.

Baseline RNFL Thickness Varies Among Black, Chinese, and Latinx Americans


In addition to the workplace, media, and politics, representation matters in research studies. In this population-based cross-sectional study, researchers compared RNFL thickness among 11,585 healthy eyes pooled from three studies of Black, Chinese, and Latinx American populations in order to identify determinants and modifiers of RNFL thickness. After adjusting for age and gender, the investigators found that Black Americans on average had the thinnest RNFL and smallest cup-to-disc ratio compared to Chinese Americans who were found to have the largest CDR and disc area. In addition, Latinx Americans experienced the greatest rates of RNFL thinning with age. Among other predictors, this study identified age and race or ethnicity as the two strongest determinants of RNFL thickness, further highlighting the importance of considering ethnic and racial identities in predicting glaucoma risk and progression.

Gender of Award Recipients in Major Ophthalmology Societies

British Journal of Ophthalmology

The representation of women in Ophthalmology has increased within the last decade, but do they receive the same recognition as men in professional Ophthalmology societies? Nguyen et al. conducted an observational study to assess the gender distribution of major ophthalmology society awards given by 15 major professional ophthalmology clinical and certifying societies. Out of 2,150 recipients for 78 awards, 1,606 (74.7%) were men and 544 (25.3%) were women. Additionally, they found that the proportion of women recipients increased from 0% in 1970 to 33.2% in 2020. This data shows that great strides have been made over the past several decades for recognition of female ophthalmologists' achievements; however, it also shows that overall, women are still underrepresented in many award categories and subspecialties. Another finding was that there were positive trends for early-career ophthalmologists such as residents, reflecting trends towards equity in the future. The authors call for societes to be more transparent in their award selection process, and diversify their selection committees moving forward.


Can Treatment of ESRD Affect the Development of Glaucoma?

Journal of Glaucoma

Don't forget about nephrons just yet! After comparing the structure and physiological pathways of kidney and eye disease, they seem to have more in common than previously recognized. Scientists investigated whether hemodynamic changes in patients being treated by hemodialysis (HD) for end stage renal disease has an effect on intraocular pressure (IOP) and precapillary choroidal thickness (PCT) measured by swept-source optical coherence tomography. PCT is typically decreased in patients with normal tension glaucoma. Previous studies suggest that the hemodynamic changes of HD can affect the blood flow of the eye, specifically of the choroid and overlying macula. On average, the PCT significantly decreased from 127.3 um before HD to 117.1 um after HD. (P<0.001), and these changes were found to coincide with macular choroidal thickness (P=0.002). However, the changes in mean ocular perfusion did not correlate with changes in PCT. Future studies are needed to elucidate the long-term effects of HD and the development of glaucoma, with consideration of confounding factors such as blood pressure medications. Regardless, this study highlights how systemic disease and medical treatments can have meaningful effects on the eye. 

Global Health

Vision as an income source

EClinical Medicine

Beyond the personal difficulty of blindness, what are the economic effects of vision loss? The true benefits of clear vision may be difficult to quantify, but Marques et al. modelled the annual productivity loss with reduced employment due to visual impairment. An estimated 18.1 million people of working age with blindness and 142.6 million with million people with moderate-severe visual impairment of working age (15-65) had a relative reduction in employment of 30.2% with potential productivity losses of $410.7 billion (0.3% of the global GDP). East Asia was the area with the largest productivity loss. Visual difficulty can be debilitating and employment can be an important source of economic development and fulfillment. Increasing access to treatment is imperative regardless of economic impact, but quantifying the economic loss created by visual impairment highlights this need. Beyond treatment, these data demonstrate a need for accommodations in countries with easier access to care. Technology, visual aid, and systematic hiring changes to include those with irreversible visual impairment will promote equitable access to economic productivity.

End of Month Quiz

1. Three machine learning models were found to be better than the traditional logistic regression model in predicting the chance of receiving surgery for what cause of visual impairment? 
A. Diabetic Retinopathy
B. Cataracts 
C. Refractive Error
D. Age-Related Macular Degeneration

2. In 12,1374 individuals from the UK Biobank, caffeine consumption was associated with:
A. Lower IOP in the general population
B. Higher IOP in those with genetic predispositions for higher IOP
C. A and B
D. None of the above

3. In a multivariate analysis, worse vision loss due to Herpes Zoster Ophthalmicus was associated with:
A. Better initial visual acuity
B. Younger Age
C. Immunosuppression 
D. None of the above

4. Children who did not receive indicated diabetic eye exams were more likely to:
A. Be white
B. Have Type 1 Diabetes
C. Have private insurance
D. Have household income <$25,000

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Quiz Answers: 1B, 2C, 3C, 4D
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