January 4, 2023

The most important ophthalmology research updates, delivered directly to you.
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In this week's issue

  • Gender and race may both be predictive factors for receiving keratoplasty in Fuchs’ endothelial corneal dystrophy.
  • In the United States, Google searches for "eye doctor near me" may underrepresent ophthalmologists.
  • Merkel cell polyomavirus status in Merkel cell carcinoma is useful for the diagnosis and choice of therapy for eyelid carcinoma.
  • A systematic review and meta-analysis found that diabetes mellitus patients with metformin usage were at lower odds of developing AMD.

Predictive factors for receiving keratoplasty in Fuchs’ endothelial corneal dystrophy


Who will get the keratoplasty? The goal of this retrospective cohort study was to determine predictive factors associated with receiving endothelial keratoplasty (EK) and penetrating keratoplasty (PK) in those with Fuchs’ endothelial corneal dystrophy (FECD). FECD is a degenerative disease of the innermost endothelial cell layer of the cornea that affects nearly 300 million people worldwide. The study analyzed 31,372 Medicare patients who were diagnosed with FECD from 2011-2019. The study found that 31,372 (4.4%) patients received EK and 2,426 (0.3%) patients received PK. The results showed that, compared to White individuals, it was less likely for Black (0.76 [0.72-0.80]), Asian or Pacific Islander (0.54 [0.48-0.61]), and Hispanic/Latino individuals (0.62 [0.55-0.70]) to receive an EK. Black, Asian/Pacific Islanders, and Hispanic/Latino were more likely to receive a PK (1.32, 1.46, and 1.62, respectively). In addition, females were less likely than males to receive EK or PK (adjusted OR 0.83 and 0.84, respectively). Overall, this study found that women are less likely than their male counterparts to receive either EK or PK. Furthermore, non-white individuals are more likely to receive PK, and white individuals are more likely to receive an EK, which indicates that gender and race may both be predictive factors.

Google searches for eye doctors may underrepresent ophthalmologists

JAMA Ophthalmology

Is catching the patient’s eye the key to accessibility? A pivotal element of medical access is the process by which the public seeks out healthcare professionals. The Google search engine represents a predominant mechanism for how patient’s explore eye care options. This study performed a geographic analysis of Google searches of eye doctor in various areas of the United States and cross-referenced these searches with available ophthalmologists and optometrists within these respective areas to determine exposure to these specialists. The overall mean proportion of ophthalmologists represented by Google searches (28.91%) was found to be less than the real available proportion (37.58%). Furthermore, ophthalmologists were underrepresented in 35/52 (67%) of states/territories studied. These results imply that several aspects of ophthalmology ranging from expanding access to care, effectively running a business, enhancing marketability, and clearly defining scope of practice differences may all be improved by appropriate search engine optimization.

Eyelid Merkel cell carcinoma: A rare form of rarity and viral host

American Journal of Ophthalmology

The murky make-up of Merkel cell carcinoma? Malevolent microbes! Merkel cell carcinoma (MCC) is a rare and aggressive malignancy that typically affects the skin of the head and neck with a small minority (2.5%) residing on the eyelid. Among risk factors such as UV exposure and immunosuppression, Merkel cell polyomavirus (MCPyV) infection is a known risk factor and critical pathogenetic event in the development of MCC. Due to the rarity of this cancer, research about prognosis and response to therapy is in its infancy. As eyelid MCC proves even more rare, there is little information on the behavior and features of this cancer, particularly with respect to MCPyV status. This retrospective study conducted in Tokyo Medical University identified 10 cases treated for MCC arising from the eyelid. Clinical data including MCPyV infection status was collected and analyzed. All patients were Japanese, and none had immunosuppressed status. Determined through PCR, all ten cases were MCPyV-positive MCC. Using American Joint Committee on Cancer (AJCC) staging, 30% of patients had tumors that were stage T2 (greater than 2 cm and less than 5 cm across.) One patient (10%) died of distant metastasis to the peritoneum. Ultimately, there is much left to discover about the characteristics and behavior of eyelid MCC with respect to Merkel cell polyomavirus infection status. Future studies may benefit from finding a comparison between MCCs with and without MCPyV infection.

Associations between metformin and age-related macular degeneration


Could this be another health benefit of the anti-diabetic “wonder drug?” Metformin, the first-line treatment for type 2 diabetes mellitus, has anti-oxidative and anti-inflammatory properties that have been suggested to prevent or treat age-related macular degeneration (AMD), but have been found to have inconsistent results up to this point within the current literature. This systematic review looked into 9 observational studies with 1,446,284 participants that described associations between metformin and AMD. Meta-analysis revealed a significant decrease in the odds of AMD for oral metformin use (pooled ORs = 0.81, 95% CI = 0.70-0.93). Subgroup analysis based on ethnicity demonstrated a significant decrease in the odds of AMD in Black (pooled ORs = 0.61, 95% CI = 0.58-0.64) and Hispanic populations (pooled ORs = 0.85, 95% CI = 0.81-0.89), indicating a highest potential benefit for these patients. However, stratified analysis showed no significant association between metformin use and either dry (pooled ORs = 0.98, 95% CI = 0.62-1.57) or wet AMD (pooled ORs = 1.03, 95% CI = 0.80-1.22). Further prospective studies are needed to confirm these encouraging associations and investigate metformin dosage effects as well as mechanisms relating to dry and wet AMD pathogenicity.


Association between risk of obstructive sleep apnea and glaucoma in Singapore

Journal of Glaucoma

We’ll wait while you catch your breath… Obstructive sleep apnea (OSA) affects over 14.3% of the world’s population (i.e., that’s 1 billion people!). It is hypothesized that decreased blood flow and hypoxia from OSA damages the optic nerve, which may result in glaucomatous changes. However, current evidence is inconclusive, perhaps due to small sample sizes, study design, and lack of differentiation between primary open angle glaucoma and primary angle closure glaucoma. In this population-based, cross-sectional study, investigators identified 3,126 participants in Singapore over the age of 40. From 2011-2015, subjects underwent both a standard ophthalmological exam and standardized interviewer-administered questionnaire to assess risk of glaucoma and OSA respectively. Participants with intermediate or high risk for OSA had a 50% increased risk of having glaucoma, with a 2-fold higher risk observed in the Malay population vs. Indian population. Given the strong association, detection and early treatment of OSA may reduce the likelihood of developing glaucoma, particularly primary open angle glaucoma.

Lens Landmarks

An anti-VEGF a month keeps the ophthalmologist away, but which one? The CATT trials looked to assess the relative safety and efficacy of two treatments for subfoveal neovascular Age-Related Macular Degeneration (AMD). Most AMD-related blindness is attributable to choroidal neovascularization and therefore anti-VEGF therapy treatment was a crucial development in the fight to improve visual outcomes. In the CATT trial, patients with AMD (n=1185) were randomized to receive either intraocular injections of ranibizumab or bevacizumab (a cheaper, off-label alternative) at either a monthly or as needed regimen. Those patients in the monthly arm of the trial were equally divided again after 1 year to either remain monthly or switch to as needed.

Key Points:
  • Ranibizumab and bevacizumab had similar effects on visual acuity (mean increase in letters of visual acuity from baseline was 8.8 in the ranibizumab-monthly group, 7.8 in the bevacizumab-monthly group, 6.7 in the ranibizumab-as-needed group, and 5.0 in the bevacizumab-as-needed group)
  • Switching to as-needed treatment after one year of monthly treatment yielded outcomes nearly equal to those obtained with as-needed treatment for the full two years, with the mean number of injections was 5.0 for ranibizumab-treated patients and 5.8 for bevacizumab-treated patients
  • There were no differences between the two drugs in rates of death or arteriothrombotic events, which are sometimes associated with systemic anti-VEGF treatment for cancer
The CATT was the first multicenter and largest trial to compare bevacizumab to ranibizumab (the more expensive, yet standard of the time). This study was crucial to establish the differences and similarities of the two drugs, primarily the non-inferiority of bevacizumab on similar treatment frequencies.

Question of the Week

In our global ophthalmology efforts to fight blindness, providing adequate early cataract surgery, which constitutes 50% of world preventable blindness, is critical.

Which one of these conditions are public health measures, according to the Vision2020 initiative, still least effective in treating:
A. Trachoma 
B. Xerophthalmia  
C. Onchocerciasis
D. Glaucoma

Keep scrolling for answer or click here

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Quiz Answer: D
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