COVID-19 News: SARS-CoV-2 Also Causes Acute Macular Neuroretinopathy But Many Are Unaware Their Eyes Are Affected!

COVID-19 News: The global impact of the COVID-19 pandemic extends far beyond respiratory concerns, as emerging research sheds light on unexpected complications affecting diverse organs, including the eyes. Recent findings from the Beijing Institute of Ophthalmology have uncovered a significant association between COVID-19 infection and the development of Acute Macular Neuroretinopathy (AMN), a rare condition known for causing transient or permanent vision loss.


SARS-CoV-2 Also Causes Acute Macular Neuroretinopathy 

Unknown to many, SARS-CoV-2 infections can cause a wide array of eye or ocular issues and many are not even aware that their eyes are affected till conditions worsen and they finally get their eyes checked by ophthalmologists. In some cases, permanent blindness results as a result of unchecked disease progression. Thailand Medical News had already covered some of the common eye issues as a result of COVID-19 such as dry eyes, optic neuritis, conjunctivitis, macular degeneration and even glaucoma!
 
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This COVID-19 News report delves into the nuanced details of a retrospective observational study conducted at Beijing Tongren Hospital, providing an in-depth exploration of the characteristics, patterns, and potential mechanisms underlying AMN following COVID-19 infection.
 
Understanding the Complexity of Acute Macular Neuroretinopathy (AMN)
AMN stands out as a rare disorder that primarily affects the outer layers of the retina, leading to distinct symptoms such as paracentral scotomas, decreased vision, and blurry vision. Clinically, AMN is characterized by reddish-brown, wedge-shaped lesions around the fovea, making multimodal imaging a crucial component of its diagnosis. Despite its self-limited course, AMN leaves a lasting impact on some patients, with persistent scotomas over months. While the exact etiology of AMN remains elusive, hypotheses suggest vascular dysregulation in the deep retinal plexus or disruptions in choroidal blood flow. Previous studies have linked AMN to various factors, including vascular issues, optic neuritis, and infections such as those caused by influenza viruses.
 
COVID-19-Related AMN - A Case Series Unveiled
The retrospective study under scrutiny included 11 patients (20 eyes) diagnosed with AMN within one month of testing positive for COVID-19. The majority of patients were young females, with an average age of 33.8 years. The interval between a positive COVID-19 PCR test and the onset of ocular symptoms was approximately 2.8 days. The range of visual symptoms reported by patients included paracentral scotomas, visual acuity decline, and blurred vision.
 
Multimodal imaging techniques, including near-infrared reflectance (NIR) imaging, optical coherence tomography (OCT), and visual field examinations, were systematically employed to analyze the nuanced characteristics of COVID-19-related AMN. The imaging characteristics revealed areas of low reflectivity on NIR imaging, hyperreflective lesions at the outer plexiform layer (OPL) and outer nuclear layer (ONL) on SD-OCT, and disruption of the ellipsoid zone (EZ). Visual field examinations corroborated these findings, confirming parafoveal scotomas corresponding to the clinical lesions. Optical coherence tomography angiography (OCT-A) further demonstrated impaired perfusion in the deep retinal vascular plexus.
 
Long-Term Impact and Clinical Outcomes
The study documented persistent retinal damage in some patients, with no improvement in visual field scotomas during follow-up. Despite achieving a best-corrected visual acuity (BCVA) of 20/40 or better in all patients at the final follow-up, 81.8% continued to experience persistent scotomas. Imaging techniques, particularly SD-OCT, proved invaluable in tracking structural changes, revealing thinning of the ONL and partial reversal of EZ defects.
 
Discussion on COVID-19-Related Ocular Complications
In addition to its respiratory impact, COVID-19 has been associated with a myriad of extrapulmonary manifestations, including ocular complications. Ophthalmologists have documented a spectrum of ocular manifestations, ranging from anterior segment involvement to retinal and optic nerve diseases. COVID-19-related retinal lesions, such as flame-shaped retinal hemorrhages and cotton-wool spots, have been reported.
 
AMN, traditionally linked to factors like dengue fever and influenza, has now emerged as a notable complication following COVID-19 infection. The study emphasizes a direct link between the onset of AMN and the pathogenesis of COVID-19, with young females being predominantly affected. The potential impact of SARS-CoV-2 on retinal cells, including the role of angiotensin-converting enzyme 2 (ACE2), is discussed as a potential mechanism contributing to AMN.
 
Exploring Mechanisms and Pathophysiology
The study attempts to unravel the complex interplay between COVID-19 infection and the development of AMN. Understanding the potential mechanisms involves delving into the impact of SARS-CoV-2 on the retina. Notably, ACE2, the primary receptor for SARS-CoV-2 entrance into host cells, has been detected in the retina, hinting at a potential target for viral attack on retinal cells. Animal studies have further demonstrated the penetration of SARS-CoV-2 through retinal cells, although the presence of the virus in the retina of COVID-19 patients remains a subject of controversy.
 
The study suggests that the inactivation of ACE2 mediated by SARS-CoV-2 may lead to an imbalance in the ACE Ang II/ACE Ang (1–7) axis, resulting in vasoconstriction. Endothelial dysfunction and a prothrombotic state observed in COVID-19, along with the presence of coagulation abnormalities and antiphospholipid antibodies, may contribute to inadequate perfusion of the deep retinal capillary plexus, playing a significant role in the pathogenesis of COVID-19-related AMN.
 
Limitations and Future Directions
While the study provides valuable insights, it acknowledges limitations such as the inability to definitively confirm AMN as a direct consequence of COVID-19. The study suggests that further research, particularly involving the analysis of inflammatory biomarkers in aqueous humor and vitreous samples using RT-PCR, could reveal immune mechanisms. However, due to ethical considerations, invasive procedures such as intraocular sampling were not performed in this study. The retrospective nature of the study and its relatively short follow-up duration (averaging 12 weeks) are additional limitations, emphasizing the need for longer-term investigations to comprehend the disease's course and its potential relationship with systemic factors.
 
Conclusion and Future Perspectives
In conclusion, this detailed exploration of COVID-19-related ocular complications, particularly AMN, sheds light on the intricate manifestations of the virus beyond its well-documented respiratory impact. The study underscores the importance of comprehensive retinal evaluation, including imaging techniques like SD-OCT, in detecting the presence of AMN in patients experiencing visual difficulties during COVID-19 infection.
 
As we navigate the ongoing complexities of the pandemic, ongoing research will play a pivotal role in enhancing our understanding of the diverse manifestations of COVID-19 and informing effective management strategies. Future studies with larger sample sizes, extended follow-up durations, and a focus on immune mechanisms are warranted to provide a more comprehensive understanding of the intricate relationship between COVID-19 and ocular complications like AMN. As researchers continue to unravel the mysteries surrounding the virus, the knowledge gained will contribute to better-informed clinical practices and improved patient outcomes.
 
The study findings were published in the peer reviewed journal: BMC Opththalmology.
https://bmcophthalmol.biomedcentral.com/articles/10.1186/s12886-024-03283-2
 
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