Photopsia

Traumatic brain injury: Mechanisms, manifestations, and visual sequelae

Traumatic brain injury (TBI) results when external physical forces impact the head with sufficient intensity to cause damage to the brain. TBI can be mild, moderate, or severe and may have long-term consequences including visual difficulties, cognitive deficits, headache, pain, sleep disturbances, and post-traumatic epilepsy. Disruption of the normal functioning of the brain leads to a cascade of effects with molecular and anatomical changes, persistent neuronal hyperexcitation, neuroinflammation, and neuronal loss. Destructive processes that occur at the cellular and molecular level lead to inflammation, oxidative stress, calcium dysregulation, and apoptosis. Vascular damage, ischemia and loss of blood brain barrier integrity contribute to destruction of brain tissue. This review focuses on the cellular damage incited during TBI and the frequently life-altering lasting effects of this destruction on vision, cognition, balance, and sleep. The wide range of visual complaints associated with TBI are addressed and repair processes where there is potential for intervention and neuronal preservation are highlighted.

Case report: Visual snow as the presenting symptom in multiple evanescent white dot syndrome. Two case reports and literature review

Purpose

Multiple evanescent white dot syndrome (MEWDS) usually manifests as photopsia, enlarged blind spots, scotomas, and blurred vision, which can be classified into positive and negative visual phenomena. Visual snow and chromatopsia were rarely reported in these patients. Herein, we described two Chinese female patients with MEWDS who initially presented with visual snow, and one of them also had yellow-tinged vision.

Methods

First, we performed the chart review of two patients. Second, we reviewed the English literature for all cases of MEWDS through PubMed until December 2021, using the terms “MEWDS” or “multiple evanescent white dot syndrome.” We concluded on all the reported patients' demographic features and symptoms. The visual acuity of patients with/without positive or negative visual phenomena was compared through one-way ANOVA.

Results

Patient 1: A 27-year-old Chinese woman experienced continuous visual snow and yellow-tinged vision in the right eye for a week. She noticed tiny white and black dots involving the entire visual field and shimmering light inferiorly. Patient 2: A 22-year-old Chinese woman complained of a gray area with continuous visual snow in the temporal visual field of the left eye for 5 days. The ocular examinations, including fundus autofluorescence (FAF), optical coherence tomography (OCT), and indocyanine green angiography (ICGA), confirmed the diagnosis of MEWDS. Their symptoms resolved spontaneously without treatment. We found 60 MEWDS case reports (147 cases) in PubMed. The mean age was 31.2 years old. The mean LogMAR best-corrected visual acuity was 0.35 ± 0.39 at the first visit and 0.01 ± 0.16 at the last visit. The most common symptoms included blurred vision (72.8%), enlarged blind spot (42.2%), photopsia (37.4%), and scotoma (33.3%). We found the patients with only positive visual phenomena had significantly worse visual acuity at the first and last visit than patients with only negative visual phenomena (p = 0.008) or the patients with both positive and negative visual phenomena (p = 0.026). Four cases similar to visual snow were discovered. Compared to the MEWDS patients without visual snow, the patients with visual snow tend to have a larger proportion of females (p = 0.005) and a better visual acuity at the first visit (p = 0.007).

Conclusion

Herein, we expand upon the clinical manifestations of MEWDS with visual snow, and the symptoms attributable to visual snow could precede the onset of MEWDS. Neurologists and ophthalmologists should carefully rule out occult chorioretinopathy before diagnosing visual snow syndrome.

Visual Snow Syndrome as a Network Disorder: A Systematic Review

Aim: By reviewing the existing clinical studies about visual snow (VS) as a symptom or as part of visual snow syndrome (VSS), we aim at improving our understanding of VSS being a network disorder. Background: Patients with VSS suffer from a continuous visual disturbance resembling the view of a badly tuned analog television (i.e., VS) and other visual, as well as non-visual symptoms. These symptoms can persist over years and often strongly impact the quality of life. The exact prevalence is still unknown, but up to 2.2% of the population could be affected. Presently, there is no established treatment, and the underlying pathophysiology is unknown. In recent years, there have been several approaches to identify the brain areas involved and their interplay to explain the complex presentation. Methods: We collected the clinical and paraclinical evidence from the currently published original studies on VS and its syndrome by searching PubMed and Google Scholar for the term visual snow. We included original studies in English or German and excluded all reviews, case reports that did not add new information to the topic of this review, and articles that were not retrievable in PubMed or Google Scholar. We grouped the studies according to the methods that were used. Results: Fifty-three studies were found for this review. In VSS, the clinical spectrum includes additional visual disturbances such as excessive floaters, palinopsia, nyctalopia, photophobia, and entoptic phenomena. There is also an association with other perceptual and affective disorders as well as cognitive symptoms. The studies that have been included in this review demonstrate structural, functional, and metabolic alterations in the primary and/or secondary visual areas of the brain. Beyond that, results indicate a disruption in the pre-cortical visual pathways and large-scale networks including the default mode network and the salience network. Discussion: The combination of the clinical picture and widespread functional and structural alterations in visual and extra-visual areas indicates that the VSS is a network disorder. The involvement of pre-cortical visual structures and attentional networks might result in an impairment of "filtering" and prioritizing stimuli as top-down process with subsequent excessive activation of the visual cortices when exposed to irrelevant external and internal stimuli. Limitations of the existing literature are that not all authors used the ICHD-3 definition of the VSS. Some were referring to the symptom VS, and in many cases, the control groups were not matched for migraine or migraine aura.

Factors Associated with Ocular Injury in Orbital Fracture Patients: Who Requires Urgent Ophthalmic Evaluation?

Importance: Create validated criteria to identify orbital fracture patients at higher risk for significant ocular injuries. Objective: Determine history and physical examination findings in orbital fracture patients who are associated with ocular injury and warrant urgent assessment by an ophthalmologist. Design, Setting, and Participants: Retrospective chart review of 535 adult orbital fracture patients evaluated at a Level I emergency department between 2014 and 2017, without prior history of orbital fracture, ocular injury, or ocular/orbital surgery. Main Outcomes and Measure: Presence of ocular injury. Results: In total, 195 (36%) patients had an ocular injury. Those with and without ocular injury were compared in a multivariate logistic regression model including demographics, fracture characteristics, injury mechanism, and physical examination findings. Visual acuity change, radiographic retrobulbar hemorrhage, abnormal pupillary reaction, and inability to open the injured eye all had significant associations with ocular injury when other findings were controlled. Conclusion: This study shows a significant association between ocular injury and visual acuity change, retrobulbar hemorrhage, abnormal pupillary reaction, and inability to open the injured eye. These factors can help triage when to obtain an urgent ophthalmology consult.

Current Perspective on Retinal Migraine

Retinal migraine was first formally described in 1882. Various terms such as "ocular migraine" and "ophthalmic migraine" have since been used interchangeably in the literature. The lack of a consistent consensus-based definition has led to controversy and potential confusion for clinicians and patients. Retinal migraine as defined by the International Classification of Headache Disorders (ICHD) has been found to be rare. The latest ICHD defined retinal migraine as 'repeated attacks of monocular visual disturbance, including scintillation, scotoma or blindness, associated with migraine headache', which are fully reversible. Retinal migraine should be considered a diagnosis of exclusion, which requires other causes of transient monocular visual loss to be excluded. The aim of this narrative review is to summarize the literature on retinal migraine, including: epidemiology and risk factors; proposed aetiology; clinical presentation; and management strategies. It is potentially a misnomer as its proposed aetiology is different from our current understanding of the mechanism of migraine.

HCN1 channels: A versatile tool for signal processing by primary sensory neurons

Most primary sensory neurons (PSNs) generate a slowly-activating inward current in response to membrane hyperpolarization (I_h) and express HCN1 along with additional isoforms coding for hyperpolarization-activated channels (HCN). Changes in HCN expression may affect the excitability and firing patterns of PSNs, but retinal and inner ear PSNs do not fire action potentials, suggesting HCN channel roles may extend beyond excitability and cell firing control. In patients taking I_h blockers, photopsia triggered in response to abrupt changes in luminance correlates with impaired visual signal processing via parallel rod and cone pathways. Furthermore, in a mouse model of inherited retinal degeneration, HCN blockers or Hcn1 genetic ablation may worsen photoreceptors' demise. PSN's use of HCN channels to adjust either their firing rate or process signals generated by sensory transduction in non-spiking PSNs indicates HCN1 channels as a versatile tool with a novel role in sensory processing beyond firing control.

Headache for ophthalmologists: current advances in headache understanding and management

Patients with headache and head pain are often referred to ophthalmologists. These symptoms can either be associated with underlying ophthalmic conditions, or more often are headache disorders unrelated to the eyes. Understanding the phenotype of the headache is critical for advice, safe discharge or onward referral. This review will provide an update on the criteria for common headache disorders that are often seen by ophthalmology and embrace disorders associated with ophthalmic diseases. It will also describe the changing management of migraine and outline recent therapies that are currently available.

Retinal disease in the neurology clinic

PURPOSE OF REVIEW

Retinal disease can manifest with visual symptoms similar to those which result from central nervous system disorders. We provide a framework for considering retinal causes of common visual complaints presenting to a neurology clinic.

RECENT FINDINGS

Technological advances have afforded quicker detection and a more thorough understanding of these retinal entities and are crucial to consider when evaluating visual complaints in the neurology clinic.

SUMMARY

It is essential to maintain a working knowledge of common retinal conditions that symptomatically overlap with common neurologic conditions. Furthermore, the ophthalmoscopic exam and retinal imaging modalities can both aid in the diagnosis and workup of visual complaints and neurologic disease.