Toxic optic neuropathies: an updated review

Methanol Induced Optic Neuropathy: Molecular Mysteries, Public Health Perspective, Clinical Insights and Treatment Strategies

Methanol-induced optic neuropathy (MION) represents a critical public health issue, particularly prevalent in lower socioeconomic populations and regions with restricted alcohol access. MION, characterized by irreversible visual impairment, arises from the toxic metabolization of methanol into formaldehyde and formic acid, leading to mitochondrial oxidative phosphorylation inhibition, oxidative stress, and subsequent neurotoxicity. The pathogenesis involves axonal and glial cell degeneration within the optic nerve and potential retinal damage. Despite advancements in therapeutic interventions, a significant proportion of affected individuals endure persistent visual sequelae. The study comprehensively investigates the pathophysiology of MION, encompassing the absorption and metabolism of methanol, subsequent systemic effects, and ocular impacts. Histopathological changes, including alterations in retinal layers and proteins, Müller cell dysfunction, and visual symptoms, are meticulously examined to provide insights into the disease mechanism. Furthermore, preventive measures and public health perspectives are discussed to highlight the importance of awareness and intervention strategies. Therapeutic approaches, such as decontamination procedures, ethanol and fomepizole administration, hemodialysis, intravenous fluids, electrolyte balance management, nutritional therapy, corticosteroid therapy, and erythropoietin (EPO) treatment, are evaluated for their efficacy in managing MION. This comprehensive review underscores the need for increased awareness, improved diagnostic strategies, and more effective treatments to mitigate the impact of MION on global health.

Infectious eye disease in the 21st century-an overview

Infectious diseases affecting the eye often cause unilateral or asymmetric visual loss in children and people of working age. This group of conditions includes viral, bacterial, fungal and parasitic diseases, both common and rare presentations which, in aggregate, may account for a significant portion of the global visual burden. Diagnosis is frequently challenging even in specialist centres, and many disease presentations are highly regional. In an age of globalisation, an understanding of the various modes of transmission and the geographic distribution of infections can be instructive to clinicians. The impact of eye infections on global disability is currently not sufficiently captured in global prevalence studies on visual impairment and blindness, which focus on bilateral disease in the over-50s. Moreover, in many cases it is hard to differentiate between infectious and immune-mediated diseases. Since infectious eye diseases can be preventable and frequently affect younger people, we argue that in future prevalence studies they should be considered as a separate category, including estimates of disability-adjusted life years (DALY) as a measure of overall disease burden. Numbers of ocular infections are uniquely affected by outbreaks as well as endemic transmission, and their control frequently relies on collaborative partnerships that go well beyond the remit of ophthalmology, encompassing domains as various as vaccination, antibiotic development, individual healthcare, vector control, mass drug administration, food supplementation, environmental and food hygiene, epidemiological mapping, and many more. Moreover, the anticipated impacts of global warming, conflict, food poverty, urbanisation and environmental degradation are likely to magnify their importance. While remote telemedicine can be a useful aide in the diagnosis of these conditions in resource-poor areas, enhanced global reporting networks and artificial intelligence systems may ultimately be required for disease surveillance and monitoring.

Is optic nerve sheath diameter diagnostic in methanol intoxication?

BACKGROUND AND AIM

Methyl alcohol intoxication causes severe morbidity and mortality, especially in developing countries. Formic acid is formed as a result of methanol metabolism. Formic acid accumulation and inhibition of adenosine triphosphate synthesis result in ophthalmic issues. This study aimed to demonstrate that the optic nerve sheath diameter (ONSD) measurement is an accurate prognostic marker and can be helpful in the diagnosis of methanol intoxication.

MATERIALS AND METHODS

This prospective study was conducted with 52 patients who were admitted to the emergency department after alcohol consumption and agreed to participate in the study. Age, gender, comorbid diseases, vital signs, ONSD ultrasonography measurements, hospitalization and discharge status, in-hospital mortality status, dialysis need, presence of visual impairment, blood gas parameters, respiratory status, time since alcohol intake, ethanol levels, urea levels, and creatinine levels were analyzed.

RESULTS

ROC curve analysis was performed to evaluate the predictive power of ONSD to diagnose methanol intoxication. The area under the curve was 0.857 for the cut-off value of 5.05 mm (95 % CI: 0.728-0.985; p < 0.001), with a sensitivity of 80.8 % and a specificity of 100 %. In the regression analysis performed to determine the prognostic value of the parameters in estimating mortality in methanol intoxication cases, an increase in ONSD (OR: 3.619; 95 % CI: 0.057-0.199; p = 0.001), an increase in lactate levels (OR: 5.653; 95 % CI: 0.040-0.085; p < 0.001), and increased duration after alcohol intake (OR: 2558; 95 % CI: 0.004-0.034; p = 0.014) were identified as independent predictors of mortality, but pH, HCO3, and base deficit levels were not significant predictors.

CONCLUSIONS

We believe that ONSD can be helpful for the differential diagnosis and prognosis of patients with suspected methanol toxicity who presented with alcohol intake.

Unregulated medication use and complications: a case study of prolonged self-treated tuberculosis in Nepal

BACKGROUND

Tuberculosis (TB) is a global public health issue, particularly in resource-constrained countries like Nepal. This case report highlights the consequences of prolonged self-treatment and non-compliance with TB management protocols, emphasizing the need for increased awareness and intervention.

CASE PRESENTATION

A 50-year-old male from Nepal self-medicated with anti-tubercular drugs for 13 years after completing the recommended course of treatment. He experienced worsening symptoms, including respiratory distress and visual impairment. Upon evaluation, he was diagnosed with chronic cavitary pulmonary aspergillosis. The patient received comprehensive treatment, including antifungal therapy, steroids, antibiotics, and respiratory support, resulting in significant improvement.

CONCLUSIONS

This case highlights the dangers of self-treatment and non-compliance with TB management protocols. It emphasizes the importance of patient education, awareness programs, and regular follow-up to ensure treatment adherence and detect complications. The case also reveals gaps in the DOTS (Directly Observed Treatment, Short Course) program, including the need for improved surveillance, and a multidisciplinary approach. The ease of over-the-counter purchase of anti-tubercular drugs in Nepal contributed to the patient's prolonged self-medication, highlighting a concerning. The complications arising from prolonged self-medication underscore the need for increased awareness, intervention, and patient education in TB management. Improving patient education, raising awareness about the risks of self-medication, and integrating ophthalmologic evaluations into standard management are essential for better TB control in Nepal.

A Case of Syphilis with a Rare Finding: Subretinal Hypopyon

PURPOSE

To report clinical features and follow-up of a case with subretinal hypopyon due to syphilis infection.

CASE PRESENTATION

We present a case of syphilis admitted with optic neuritis and treated with intravenous pulse steroids without antibiotics. The patient was referred to the uvea clinic in the follow-up because of decreased vision and the onset of multiple retinitis foci. We determined subretinal hypopyon in the left eye and a positive TPHA test. A significant regression was observed in retinitis and hypopyon with antibiotic therapy.

CONCLUSION

Before starting a steroid treatment, infective etiologies should be considered in patients with optic neuritis. Treating with a high dosage of steroids without antibiotics in syphilis would worsen the clinical features and prognosis.

Optic nerve diseases and regeneration: How far are we from the promised land?

The retinal ganglion cells (RGCs) are the sole output neurons that connect information from the retina to the brain. Optic neuropathies such as glaucoma, trauma, inflammation, ischemia and hereditary optic neuropathy can cause RGC loss and axon damage, and lead to partial or total loss of vision, which is an irreversible process in mammals. The accurate diagnoses of optic neuropathies are crucial for timely treatments to prevent irrevocable RGCs loss. After severe ON damage in optic neuropathies, promoting RGC axon regeneration is vital for restoring vision. Clearance of neuronal debris, decreased intrinsic growth capacity, and the presence of inhibitory factors have been shown to contribute to the failure of post-traumatic CNS regeneration. Here, we review the current understanding of manifestations and treatments of various common optic neuropathies. We also summarise the current known mechanisms of RGC survival and axon regeneration in mammals, including specific intrinsic signalling pathways, key transcription factors, reprogramming genes, inflammation-related regeneration factors, stem cell therapy, and combination therapies. Significant differences in RGC subtypes in survival and regenerative capacity after injury have also been found. Finally, we highlight the developmental states and non-mammalian species that are capable of regenerating RGC axons after injury, and cellular state reprogramming for neural repair.

Oxidative Stress: A Suitable Therapeutic Target for Optic Nerve Diseases?

Optic nerve disorders encompass a wide spectrum of conditions characterized by the loss of retinal ganglion cells (RGCs) and subsequent degeneration of the optic nerve. The etiology of these disorders can vary significantly, but emerging research highlights the crucial role of oxidative stress, an imbalance in the redox status characterized by an excess of reactive oxygen species (ROS), in driving cell death through apoptosis, autophagy, and inflammation. This review provides an overview of ROS-related processes underlying four extensively studied optic nerve diseases: glaucoma, Leber's hereditary optic neuropathy (LHON), anterior ischemic optic neuropathy (AION), and optic neuritis (ON). Furthermore, we present preclinical findings on antioxidants, with the objective of evaluating the potential therapeutic benefits of targeting oxidative stress in the treatment of optic neuropathies.

Biologic therapies for psoriasis and eyes

Psoriasis is a systemic inflammatory disorder, manifested mainly by skin lesions, but the inflammation also may affect the joints and eye. Many comorbidities have been described in association with psoriasis, including metabolic syndrome and coronary plaques. The pathomechanism of psoriasis is multifaceted. Both genetic and immunologic aspects play a role in stimulating inflammation. Genetic susceptibility is conditioned by presence of the human leukocyte antigen-C*06:02 risk allele and the inflammatory reaction secondary to cytokines, such as tumor necrosis factor α, interleukin 17 (IL-17), IL-20, IL-23, and interferon alfa. Besides the conventional therapy of topical steroids and immunosuppressants, biologic therapies are widely used in the treatment of psoriasis, psoriatic arthritis, and coexisting uveitis. In the majority of cases, biologic therapy has a beneficial effect on uveitis, but in some cases, some of these drugs can lead to serious side effects threatening vision.

Ocular Manifestations After Acute Methanol Poisoning

Acute methanol poisoning is first and foremost life-threatening. Otherwise, functional prognosis is mainly based on ocular impairment. In this case series we aimed to describe the ocular manifestations after acute methanol poisoning during an outbreak in Tunisia. The data from 21 patients (41 eyes) were analysed. All patients underwent a complete ophthalmological examination including visual fields, colour vision test and optical coherence tomography with evaluation of the retinal nerve fibre layer. Patients were classified into two groups. Group 1 included patients with visual symptoms and group 2 included patients with no visual symptoms. Ocular abnormalities were seen in 81.8% of patients with ocular symptoms. They included: optic neuropathy in 7 patients (63.6%); central retinal artery occlusion in 1 patient (9.1%); and central serous chorioretinopathy in 1 patient (9.1%). Mean blood methanol levels were significantly higher in patients without ocular symptoms (p = .03).

Diagnosis of Optic Disc Oedema: Fundus Features, Ocular Imaging Findings, and Artificial Intelligence

Optic disc swelling is a manifestation of a broad range of processes affecting the optic nerve head and/or the anterior segment of the optic nerve. Accurately diagnosing optic disc oedema, grading its severity, and recognising its cause, is crucial in order to treat patients in a timely manner and limit vision loss. Some ocular fundus features, in light of a patient's history and visual symptoms, may suggest a specific mechanism or aetiology of the visible disc oedema, but current criteria can at most enable an educated guess as to the most likely cause. In many cases only the clinical evolution and ancillary testing can inform the exact diagnosis. The development of ocular fundus imaging, including colour fundus photography, fluorescein angiography, optical coherence tomography, and multimodal imaging, has provided assistance in quantifying swelling, distinguishing true optic disc oedema from pseudo-optic disc oedema, and differentiating among the numerous causes of acute optic disc oedema. However, the diagnosis of disc oedema is often delayed or not made in busy emergency departments and outpatient neurology clinics. Indeed, most non-eye care providers are not able to accurately perform ocular fundus examination, increasing the risk of diagnostic errors in acute neurological settings. The implementation of non-mydriatic fundus photography and artificial intelligence technology in the diagnostic process addresses these important gaps in clinical practice.

Electrophysiological assessment of nutritional optic neuropathy: a case report

PURPOSE

To report an unexpectedly asymmetric, progressive nutritional optic neuropathy associated with vitamin A deficient optic canal hyperostosis in a 15-year-old female with a long history of a restricted diet.

METHODS

We performed comprehensive ophthalmic assessments in a fifteen-year-old female with a long history of restricted eating who presented with suspected nutritional optic neuropathy, predominantly affecting the right eye vision.

RESULTS

A review of computerised tomography and magnetic resonance imaging revealed bilateral optic canal hyperostosis likely associated with vitamin A deficiency. Electrodiagnostic tests and optical coherence tomography provided structure-function evidence of bilateral retinal ganglion cell dysfunction and notably revealed severe loss of temporal fibres in the left eye which showed cecocentral scotoma but normal visual acuity. Although selective damage of the papillomacular bundle has been well-documented in nutritional and toxic optic neuropathies, compressive optic canal hyperostosis secondary to nutritional deficiency has been rarely reported.

CONCLUSIONS

Nutritional deficiencies are increasing in high-income countries and may be linked to the rise of gastrointestinal disorders, strict vegan and vegetarian diets and avoidant restrictive food intake disorder (ARFID) associated with conditions such as depression and autism spectrum syndrome (ASD). Our findings highlight the value of electrodiagnostic testing alongside imaging in complex nutritional optic neuropathies to help monitor, guide treatment and preserve remaining sight in a child.

The Role of Optical Coherence Tomography Angiography in Optic Nerve Head Edema: A Narrative Review

Optic nerve head (ONH) edema is a clinical manifestation of many ocular and systemic disorders. Ocular and central nervous system imaging has been used to differentiate the underlying cause of ONH edema and monitor the disease course. ONH vessel abnormalities are among the earliest signs of impaired axonal transportation. Optical coherence tomography angiography (OCTA) is a noninvasive method for imaging ONH and peripapillary vessels and has been used extensively for studying vascular changes in ONH disorders, including ONH edema. In this narrative review, we describe OCTA findings of the most common causes of ONH edema and its differential diagnoses including ONH drusen.

Clinical Characteristics of Methanol-Induced Optic Neuropathy: Correlation between Aetiology and Clinical Findings

Purpose. To show the clinical characteristics, identify the magnetic resonance imaging (MRI) and optical coherence tomography (OCT) features, and observe the visual outcome of methanol-induced optic neuropathy. Methods. Clinical data were retrospectively collected from in-patients diagnosed with methanol-induced optic neuropathy in the Neuro-Ophthalmology Department of the Chinese People’s Liberation Army General Hospital from January 2016 to January 2021. Results. Eight patients were included in this study. The exposure time was 6–34 h for ingestion, 3-4 months for inhalation, and more than ten years for skin absorption. All patients demonstrated bilateral acute visual impairment. Seven of eight patients had other accompanying systemic symptoms. Seven of eight patients demonstrated optic nerve lesions in MRI, and five presented with a hyperintense T2 signal in a “central” type. OCT showed the macular ganglion cell layer and inner plexiform layer (mGCL-IPL) thinning before the peripapillary retinal nerve fiber layer (pRNFL) thinning. The visual improvement was achieved transiently for seven of eight patients after treatment. One patient with a mitochondrial DNA mutation maintained a bilateral no-light perception (NLP) from the onset to the last visit. All patients had poor visual prognoses, with either light perception or NLP. Conclusions. Methanol-induced optic neuropathy is a rare bilateral optic neuropathy with a poor visual outcome. A centrally hyperintense T2 signal of the optic nerve is common in methanol-induced optic neuropathy. The thinning of the mGCL-IPL is more sensitive than that of the pRNFL for early diagnosis. A mitochondrial genetic defect may be a predisposing factor for methanol-induced optic neuropathy.

Visual outcomes of toxic optic neuropathy secondary to Ethambutol: A retrospective observational study from India, an endemic country

Purpose

Ethambutol (EMB) is one of the first-line drugs used for treating tuberculosis. Vision loss due to optic nerve toxicity is a well-known potential side effect of the drug. Our aim was to evaluate the clinical features and visual outcomes of patients with EMB optic neuropathy (EON).

Methods

A retrospective, observational, single-center study of all patients who were diagnosed to have EON during January 2017-December 2019 was done. All these patients were screened in the Department of Neuro-ophthalmology at a referral tertiary eye care institution in India. Clinical features, visual outcomes, and neuroimaging findings of these patients were analyzed.

Results

Two hundred and fifty-six eyes of 128 patients were included. Of these, 73 were male and 55 were female. Mean age was 50.55 ± 15 years. Mean visual acuity at presentation was 1.12 ± 0.45 logarithm of the minimum angle of resolution (logMAR). One hundred and forty three eyes had normal optic disk on presentation, 111 had disk pallor, and two eyes had disk edema. The most common field defect was central/paracentral scotoma (26.2%) followed by temporal defects (24.6%). Magnetic resonance imaging (MRI) brain and orbit showed optic nerve signals in 19.6% and chiasmal signals in 5.2%. At the final follow-up, a ≥2-line vision improvement was noted in 161 eyes (62.9%), which was statistically significant.

Conclusion

Multiple prognostic factors were analyzed to predict the visual recovery of EON. We observed that patients presenting with visual acuity worse than 6/60 had poor visual outcome and long duration of follow-up showed better visual recovery, proving the possibility of a gradual recovery pattern of EON. Interestingly, we found in our study that the chances of favorable visual outcome were directly proportionate to early diagnosis and cessation of EMB.

Ethambutol-induced optic neuropathy: Functional and structural changes in the retina and optic nerve

BACKGROUD

Ethambutol hydrochloride (EMB) is used in the treatment of tuberculosis and is used as first line modality in combination with other medications. Ethambutol optic neuropathy (EON) is a rare but well-recognised adverse ocular event in patients who receive ethambutol for the treatment of mycobacterial infections and may be potentially devastating with reversible to irreversible changes in visual acuity.

KEY FINDINGS

Optical coherence tomography has been used to evaluate the thickness of retinal nerve fibre and ganglion cell layers to look for degenerative changes and early markers. Electrophysiological tests like multifocal electroretinogram, visual evoked potentials and visual fields have been used to understand the functional changes associated with established EON and also whether these can be used to detect subclinical EON and correlate them with the structural changes. In this review, we have summarised evidence published till December 2021 related to evaluation of structural and functional changes in the retina and optic nerve in eyes with EON.

AN EYE FOR AN EYE, A TOOTH FOR A TOOTH

A 77-year-old man presented with the complaint of a painless decrease in vision in both eyes for one year. He underwent bilateral cataract surgery without improvement. Neuroimaging and genetic testing for mitochondrial disease was negative. Examination was consistent with a diagnosis of toxic-nutritional optic neuropathy. On further questioning the patient admitted chronic ingestion of mouthwash 3 times daily in the past 18 months after completion of dental work. After discontinuation of mouthwash ingestion, visual acuity and fields improved. This case shows how chronic ingestion of mouthwash can lead to a bilateral toxic optic neuropathy even in the absence of other risk factors.

Demographics and etiologic characteristics of non-glaucomatous optic atrophy: a single-center cross-sectional study from Turkey

BACKGROUND

Optic atrophy is an end-stage pathology of optic nerve diseases that is characterized by optic nerve pallor and vision loss. Because of its sight-threatening effects, understanding its epidemiology and etiology is crucial. In this study, we aimed to determine the epidemiologic features of optic nerve pathologies which lead to optic atrophy.

METHODS

This is a cross-sectional study in which, medical records of optic atrophy patients who were followed up in our clinic between 1999 and 2020 were evaluated. Three hundred and sixty eyes of 226 patients were included in the study. Demographic data were received from the patients' files. Patients with glaucomatous optic atrophy, consecutive optic atrophy and patients with less than a year follow-up were excluded from the study.

RESULTS

The most frequent reason of optic atrophy was central nervous system diseases (27.43%) followed by secondary non-arteritic ischemic optic neuropathy (26.99%). The most frequent etiology of optic atrophy was non-arteritic ischemic optic neuropathy in males and central nerve system-related pathologies in females. The highest presentation age (mean 63.6 ± 17.85 years) was observed in arteritic ischemic optic neuropathy and central nerve system-related optic atrophy had the lowest presentation age (median 14 years, IQR [34]).

CONCLUSION

Central nerve system diseases and non-arteritic ischemic optic neuropathies were the most common causes of non-glaucomatous and non-consecutive optic atrophy in Turkey. Better understanding of underlying etiologies of optic atrophy may lead us to take precautions timely for irreversible optic nerve dysfunction which is an important reason of blindness.

Toxicity induced by ciprofloxacin and enrofloxacin: oxidative stress and metabolism

Ciprofloxacin (CIP) (human use) and enrofloxacin (ENR) (veterinary use) are synthetic anti-infectious medications that belong to the second generation of fluoroquinolones. They have a wide antimicrobial spectrum and strong bactericidal effects at very low concentrations via enzymatic inhibition of DNA gyrase and topoisomerase IV, which are required for DNA replication. They also have high bioavailability, rapid absorption with favorable pharmacokinetics and excellent tissue penetration, including cerebral spinal fluid. These features have made them the most applied antibiotics in both human and veterinary medicine. ENR is marketed exclusively for animal medicine and has been widely used as a therapeutic veterinary antibiotic, resulting in its residue in edible tissues and aquatic environments, as well as the development of resistance and toxicity. Estimation of the risks to humans due to antimicrobial resistance produced by CIP and ENR is important and of great interest. Moreover, in rare cases due to their overdose and/or prolonged administration, the development of CIP and ENR toxicity may occur. The toxicity of these fluoroquinolones antimicrobials is mainly related to reactive oxygen species (ROS) and oxidative stress (OS) generation, besides metabolism-related toxicity. Therefore, CIP is restricted in pregnant and lactating women, pediatrics and elderly similarly ENR do in the veterinary field. This review manuscript aims to identify the toxicity induced by ROS and OS as a common sequel of CIP and ENR. Furthermore, their metabolism and the role of metabolizing enzymes were reported.

Toxic and Nutritional Optic Neuropathies—An Updated Mini-Review

Optic neuropathies constitute a group of conditions with various etiologies and might be caused by different factors; we can distinguish the genetic and acquired causes of optic neuropathies. Even though the symptoms are not highly specific, this condition is primarily characterized by unilateral or bilateral vision loss with worsening color detection. The loss may be acute or gradual depending on the causation. In this article, we included a specification of toxic optic neuropathy (TON) mainly triggered by alcohol abuse and also the usage of other substances, including drugs or methanol, as well as intoxication by metals, organic solvents, or carbon dioxide. Nutritional deficiencies, vitamin absorption disorder, and anemia, which usually appear during excessive alcohol intake, and their effect on the etiology of the optic neuropathy have been likewise discussed.

Bitemporal peripapillary hemorrhages: Toxic-ischemic optic neuropathy caused by ethanol and cocaine abuse

A 36-year-old man presented complaining of bilateral painless vision loss. He was admitted with chronic ethanol abuse, as well as sporadic cocaine consumption three days before symptom onset. General medical evaluation dismissed cerebral and cardiovascular events. Blood tests revealed folic acid deficiency. Visual acuity (VA) was count fingers in both eyes (OU). Fundoscopic findings included remarkable bitemporal peripapillary hemorrhages. A diagnosis of toxic-ischemic optic neuropathy was made. The hemorrhages resolved after three weeks, with VA recovering to 20/20 OU. The sequelae included bitemporal peripapillary retinal fiber loss on optical coherence tomography, and central scotomas observed on visual field tests. This is the first report of cocaine as a triggering agent for a classical presentation of toxic optic neuropathy and the presence of peripapillary hemorrhages in its initial stages.

Papilledema: A Review of the Pathophysiology, Imaging Findings, and Mimics

Increased intracranial pressure is the most common cause of papilledema. Multiple etiologies such as cerebral edema, hydrocephalus, space occupying lesions, infection, and idiopathic intracranial hypertension among others should be considered. Imaging plays a critical role in the detection of pathologies that can cause papilledema. MRI with contrast and CE-MRV, in particular, are key for the diagnosis of idiopathic intracranial hypertension. This review will focus in common and infrequent causes of papilledema, the role of imaging in patients with papilledema as well as its potential mimickers.

Methanol-induced optic neuropathy: a still-present problem

Methanol-induced optic neuropathy (Me-ION) is a serious condition that may result in long-term or irreversible visual impairment or even blindness secondary to damage and loss of function of the optic nerve and retina. Me-ION shows a tendency to occur as mass poisonings around the world with a clear predilection for poor societies in developing countries. The main mechanism underlying the molecular basis of Me-ION is the inhibition of the mitochondrial oxidative phosphorylation process through the binding of the toxic metabolite of methanol—formic acid—with the key enzyme of this process—cytochrome c oxidase. However, other mechanisms, including damage to the eye tissues by oxidative stress causing the intensification of the oxidative peroxidation process with the formation of cytotoxic compounds, as well as an increase in the synthesis of pro-inflammatory cytokines and influence on the expression of key proteins responsible for maintaining cell homeostasis, also play an important role in the pathogenesis of Me-ION. Histopathological changes in the eye tissues are mainly manifested as the degeneration of axons and glial cells of the optic nerve, often with accompanying damage of the retina that may involve all its layers. Despite the development of therapeutic approaches, persistent visual sequelae are seen in 30–40% of survivors. Thus, Me-ION continues to be an important problem for healthcare systems worldwide.

Neuro-ophthalmic manifestations of tuberculosis

Neuro-ophthalmic features are a known association in tuberculosis, especially common in central nervous system tuberculosis (CNS-TB). They are mostly the result of the visual pathway and/or ocular motor and other cranial nerve involvement. Furthermore, toxic optic neuropathy and paradoxical response to anti-tubercular drugs (ATT) are also not uncommon. The etiopathogenesis is by the complex interplay of various factors like exudates, vasculitis, arachnoiditis, presence of tuberculomas, hydrocephalus, brain infarcts and/or immune-mediated reaction. The entity often poses a diagnostic dilemma for the ophthalmologists/neuro-ophthalmologists and may lead to irreversible vision loss. The presence of neuro-ophthalmic features not only affect the visual outcome but are also predictors of systemic morbidity of the disease. Therefore, understanding and knowledge about this entity are necessary for the comprehensive management of the disease. While various forms of TB including CNS-TB have been well-dealt with in literature, little is discussed specifically about the neuro-ophthalmic manifestations of tuberculosis. Therefore, the purpose of this review is to highlight current understanding of the types of neuro-ophthalmic involvement in tuberculosis, its etiopathogenesis, diagnosis and management.

Identifying and Treating Ocular Manifestations in Psoriasis

Psoriasis is a chronic immune-mediated inflammatory skin condition that commonly presents with red, thickened, and scaling plaques. Given the prominent cutaneous manifestations of psoriasis, more subtle ophthalmic findings of the disease may initially go undetected, with the potential for significant ocular morbidity. Associated ocular disease can involve nearly any structure of the eye, with the eyelids most commonly being affected, resulting in relatively common signs and symptoms of ocular surface discomfort. The presence of intraocular inflammation (i.e., uveitis) or retinal involvement carry a heightened risk of vision loss, and are often more difficult to diagnose outside of the ophthalmology clinic. Early detection and treatment of ocular disease can limit morbidity and are critical to the management of these patients, which requires coordination of care between dermatologists and ophthalmologists. The objective of this article was to review the most common ocular conditions that affect psoriatic patients, when to consider referral to an ophthalmologist, and to summarize the adverse ocular effects of current psoriasis treatments.

Ethambutol toxicity: Expert panel consensus for the primary prevention, diagnosis and management of ethambutol-induced optic neuropathy

Ethambutol use may lead to permanent vision loss by inducing a dose- and duration-dependent optic neuropathy. This has been of concern to ophthalmologists and physicians both; however, ethambutol continues to be used because of its anti-mycobacterial action with relative systemic safety. Recently, the guidelines of the Revised National Tuberculosis Control Programme of India have been revised to allow for fixed dose and longer duration of ethambutol use; this is likely to result in an increase in vision-threatening adverse effects. Taking cognizance of this, neuro-ophthalmologists, infectious disease specialists, and scientists met under the aegis of the Indian Neuro-Ophthalmology Society to deliberate on prevention, early diagnosis, and management of ethambutol-related toxic optic neuropathy. The recommendations made by the expert group focus on early suspicion of ethambutol toxicity through screening at the physician’s office and opportunistic screening by the ophthalmologist. Further, they focus on an early diagnosis through identification of specific clinical biomarkers and on management in way of early stoppage of the drug and supportive therapy. This statement also describes the mechanism of reporting a case of toxic optic neuropathy through the Pharmacovigilance Programme of India and emphasizes the need for spreading awareness regarding vision-threatening adverse effects among patients and healthcare workers.

Methanol Poisoning Leading to Brain Death: A Case Report

Introduction

The COVID-19 pandemic has put increased stress on medical systems, infrastructure, and the public in expected and unexpected ways. This case report summarises an unexpected case of methanol poisoning from hand sanitiser ingestion due to changes in industry regulations, increased demand for cleaning products and severe psychosocial stressors brought on by the pandemic. Severe methanol toxicity results in profound metabolic disturbances, damage to the retina and optic nerves, and potentially death.

Case Presentation

The patient was a 26-year-old male with alcohol use disorder who presented with one day of nausea, vomiting, and abdominal pain after consuming hand sanitiser. Within a few hours, the patient had suffered multiple seizures, cardiac arrests and required admission to the ICU for emergent management of methanol poisoning. EEG and brain perfusion imaging were performed to confirm brain death, given concerns about the cranial nerve exam after methanol poisoning.

Conclusions

While rare, methanol toxicity remains a potentially fatal poisoning in the United States and worldwide. When healthcare and public resources are strained, healthcare professionals must consider particularly abnormal presentations. In patients suspected of brain death from methanol toxicity, cranial nerve examination may be unreliable. Therefore, additional testing is necessary to confirm brain death.

New insights into the role of autophagy in retinal and eye diseases

Autophagy is a fundamental homeostatic pathway that mediates the degradation and recycling of intracellular components. It serves as a key quality control mechanism, especially in non-dividing cells such as neurons. Proteins, lipids, and even whole organelles are engulfed in autophagosomes and delivered to the lysosome for elimination. The retina is a light-sensitive tissue located in the back of the eye that detects and processes visual images. Vision is a highly demanding process, making the eye one of the most metabolically active tissues in the body and photoreceptors display glycolytic metabolism, even in the presence of oxygen. The retina and eye are also exposed to other stressors that can impair their function, including genetic mutations and age-associated changes. Autophagy, among other pathways, is therefore a key process for the preservation of retinal homeostasis. Here, we review the roles of both canonical and non-canonical autophagy in normal retinal function. We discuss the most recent studies investigating the participation of autophagy in eye diseases such as age-related macular degeneration, glaucoma, and diabetic retinopathy and its role protecting photoreceptors in several forms of retinal degeneration. Finally, we consider the therapeutic potential of strategies that target autophagy pathways to treat prevalent retinal and eye diseases.

Management of toxic optic neuropathy via a combination of Wharton's jelly-derived mesenchymal stem cells with electromagnetic stimulation

PURPOSE

To investigate the effect of the combination of Wharton's jelly derived mesenchymal stem cells (WJ-MSC) and high frequency repetitive electromagnetic stimulation (rEMS) in the therapy of toxic optic neuropathies with severe symptoms after the available current therapy modalities which were unsucessful.

MATERIAL AND METHODS

This prospective, open-label clinical phase-3 study was conducted at Ankara University Faculty of Medicine, Department of Ophthalmology between April 2019 and April 2021. Thirty-six eyes of 18 patients with toxic optic neuropathy (TON) were included in the study. Within 1-3 months after the emergency interventions, patients with various degrees of sequela visual disturbances were studied in this clinical trial. The cases were divided into three groups according to similar demographic characteristics. Group 1: Consists of 12 eyes of 12 patients treated with the WJ-MSC and rEMS combination in one eye. Group 2: Consists of 12 eyes of 12 patients treated with only rEMS in one eye. Group 3: Consists of 12 eyes of six patients treated with only WJ-MSC in both eyes. The course was evaluated by comparing the quantitive functional and structural assessment parameters measured before and at the fourth month of applications in each group.

RESULTS

The mean best corrected visual acuity (BCVA) delta change percentages of the groups can be ranked as: Group 1 (47%) > Group 3 (32%) > Group 2 (21%). The mean fundus perimetry deviation index (FPDI) delta change percentages of the groups can be ranked as: Group 1 (95%) > Group 2 (33%) > Group 3 (27%). The mean ganglion cell complex (GCC) thickness delta change (decrease in thickness) percentages can be ranked as: Group 1 (- 21%) > Group 3 (- 15%) > Group 2 (- 13%). The visual evoked potential (VEP) P100 latency delta change percentages of the groups can be ranked as: Group 1 (- 18%) > Group 3 (- 10%) > Group 2 (- 8%). The P100 amplitude delta change percentages of the groups can be ranked as: Group 1 (105%) > Group 3 (83%) > Group 2 (24%).

CONCLUSION

Toxic optic neuropathies are emergent pathologies that can result in acute and permanent blindness. After poisoning with toxic substances, progressive apoptosis continues in optic nerve axons and ganglion cells. After the proper first systemic intervention in intensive care clinic, the WJ-MSC and rEMS combination seems very effective in the short-term period in cases with TON. To prevent permanent blindness, a combination of WJ-MSC and rEMS application as soon as possible may increase the chance of success in currently untreatable cases. Trial Registration ClinicalTrials.gov ID: NCT04877067.

Toxicity in Peripheral Nerves: An Overview

Introduction to a collection. This article is intended to introduce a collection of papers on toxic neuropathies. Toxic neuropathies can be caused by a variety of substances and by different mechanisms. Toxic agents are numerous and can be distinguished between drugs, recreational agents, heavy metals, industrial agents, pesticides, warfare agents, biologic substances and venoms. Toxic agents reach the nervous system by ingestion, transcutaneously, via the mucous membranes, parenterally and by aerosols. The most frequent types are cumulative toxicities. Other types are acute or delayed toxicities. Pathogenetic mechanisms range from a specific toxic substance profile causing axonal or demyelinating lesions, towards ion channel interferences, immune-mediated mechanisms and a number of different molecular pathways. In addition, demyelination, focal lesions and small fiber damage may occur. Clinically, neurotoxicity presents most frequently as axonal symmetric neuropathies. In this work, we present a panoramic view of toxic neuropathy, in terms of symptoms, causes, mechanisms and classification.

Infliximab-related Optic Neuritis in a Patient with Crohn&apos;s Disease: a Case Report and Literature Review

Purpose: We report a case of optic neuritis related to infliximab treatment in a patient with Crohn’s disease, along with a review of the relevant literature.Case summary: A 22-year-male patient complained of blurred vision in the left eye for 2-3 weeks. His best-corrected visual acuity was 8/20 in the left eye. Relative afferent pupillary defect was detected in the left eye and the pupils were of equal size. There was no pain on ocular movement. The results of slit-lamp and fundus examinations were normal. A visual field test revealed a central to inferior visual field defect in the left eye. Orbit magnetic resonance imaging revealed perineural enhancement of the left optic nerve. He had a 5-year history of Crohn’s disease and had been treated with intravenous infliximab (600 mg every 2 weeks). A diagnosis of retrobulbar optic neuritis associated with infliximab was made. He was infused with high-dose methylprednisolone, which was changed to per oral administration. His visual acuity and visual field defect improved after 3 months.Conclusions: Tumor necrosis factor-α inhibitors, such as infliximab, may cause optic neuritis. Therefore, history-taking is important for differential diagnosis and appropriate treatment.

ABCB1 and ABCG2 Together Limit the Distribution of ABCB1/ABCG2 Substrates to the Human Retina and the ABCG2 Single Nucleotide Polymorphism Q141K (c.421C> A) May Lead to Increased Drug Exposure

The widely expressed and poly-specific ABC transporters breast cancer resistance protein (ABCG2) and P-glycoprotein (ABCB1) are co-localized at the blood-brain barrier (BBB) and have shown to limit the brain distribution of several clinically used ABCB1/ABCG2 substrate drugs. It is currently not known to which extent these transporters, which are also expressed at the blood-retinal barrier (BRB), may limit drug distribution to the human eye and whether the ABCG2 reduced-function single-nucleotide polymorphism (SNP) Q141K (c.421C > A) has an impact on retinal drug distribution. Ten healthy male volunteers (five subjects with the c.421CC and c.421CA genotype, respectively) underwent two consecutive positron emission tomography (PET) scans after intravenous injection of the model ABCB1/ABCG2 substrate [¹¹C]tariquidar. The second PET scan was performed with concurrent intravenous infusion of unlabelled tariquidar to inhibit ABCB1 in order to specifically reveal ABCG2 function.In response to ABCB1 inhibition with unlabelled tariquidar, ABCG2 c.421C > A genotype carriers showed significant increases (as compared to the baseline scan) in retinal radiotracer influx K₁ (+62 ± 57%, p = 0.043) and volume of distribution V_T (+86 ± 131%, p = 0.043), but no significant changes were observed in subjects with the c.421C > C genotype. Our results provide the first evidence that ABCB1 and ABCG2 may together limit the distribution of systemically administered ABCB1/ABCG2 substrate drugs to the human retina. Functional redundancy between ABCB1 and ABCG2 appears to be compromised in carriers of the c.421C > A SNP who may therefore be more susceptible to transporter-mediated drug-drug interactions at the BRB than non-carriers.

A Case of Presumed Bonsai-induced Severe Toxic Optic Neuropathy

Apart from the known factors that cause toxic optic neuropathy, there may be factors that have not yet been identified. We report a 32-year-old man who presented with a complaint of decreased vision. His optic discs were diffusely covered with a black pigment, and below were atrophic. The vessels appeared to have disappeared below the pigmentation. He reported smoking tobacco, drinking alcohol, and using cannabis. His vision in both eyes began decreasing gradually after he started using bonsai, a synthetic cannabinoid, 2 years previously. No case of toxic optic neuropathy with bilateral severe vision loss and intense pigmentation with the use of bonsai has been reported before, and our case will be reinforced if other such cases are reported in the future.

Case Report: Nutritional and Toxic Optic Neuropathy: A Diagnostic Dilemma

SIGNIFICANCE

Nutritional and toxic optic neuropathies are rare disorders characterized by visual impairment due to optic nerve damage by a toxin, usually with coexisting nutritional deficiencies. Its pathophysiology is still unclear, and multiple mechanisms implicated act synergistically to bring about this condition. The decline in its incidence and its confusing clinical appearance make diagnosing nutritional and toxic optic neuropathies challenging.

PURPOSE

This is an observational clinical case report of an atypical clinical case of a nutritional and toxic optic neuropathy with a subacute presentation and papilledema at the time of diagnosis. The patient provided written informed consent for medical information and images to be published.

CASE REPORT

A 47-year-old man presented with progressive, painless bilateral decrease in central vision over 15 days. The patient had a long-standing history of alcohol abuse and was a heavy smoker. The examination revealed dyschromatopsia, 20/400 visual acuity on both eyes, and no relative afferent pupillary defect. Funduscopy revealed bilateral papilledema. A visual field test showed generalized depression with centrocecal involvement in the left eye. Laboratory studies evidenced decreased vitamin B12/B1 and red blood cell folate levels, increased acute phase reactants, hypertransaminasemia, and macrocytic anemia. Serologies and methanol in urine were negative. After the discontinuation of tobacco use and alcohol accompanied by vitamin supplementation, our patient's visual field, visual acuity, and papilledema improved remarkably. After 5 months, visual acuity and funduscopy were normal.

CONCLUSIONS

Although some hallmark signs were visible in this case, its subacute presentation and the presence of papilledema at diagnosis caused some diagnostic uncertainty. Nutritional and toxic optic neuropathy is a rare and challenging diagnosis because of a lack of biomarkers. Eye care clinicians should consider nutritional and toxic optic neuropathies to prevent severe and irreversible visual damage resulting from underdiagnosis and mismanagement.

Mild Leber hereditary optic neuropathy (LHON) in a Western European family due to the rare Asian m.14502T>C variant in the MT-ND6 gene

BACKGROUND

Leber hereditary optic neuropathy (LHON) is a mitochondrial neurodegenerative disease. The majority (>90%) is related to three primary mitochondrial DNA (mtDNA) variants: ND1 m.3460G>A, ND4 m.11778G>A and ND6 m.14484T>C. The remaining 10% is associated with >40 secondary variants with variable penetrance and incidence between different ethnic backgrounds.

MATERIALS AND METHODS

Five sisters underwent an extensive ophthalmic workup including psychophysical, electrophysiological, multimodal brain imaging, biochemical testing and molecular screening. MT-ND6 protein modelling was performed.

RESULTS

A 23-year-old woman presented with acute central visual loss to counting fingers in the right eye. She developed a central visual field scotoma, severe color vision deficiencies and impaired pattern visual evoked responses. Progressive optic atrophy ensued. The left eye was unremarkable, except for borderline thinning of the temporal retinal nerve fiber layer. Alcohol use and passive smoking were noted. MtDNA analysis revealed a rare variant, m.14502T>C in MT-ND6, exclusively known to cause optic neuropathy in an Asian population. Three sisters of the proband, two of whom reported tobacco and alcohol abuse, had bilateral temporal optic disc pallor without functional impact. A fourth non-smoker sister had a completely normal eye exam.

CONCLUSIONS

The rare Asian m.14502T>C variant in the MT-ND6 gene was linked to a mild LHON phenotype in a Western European family. Penetrance in this family was likely triggered by alcohol and tobacco abuse. A full mtDNA sequencing is warranted in the case of high clinical suspicion of LHON when mutation analysis for the three common pathogenic variants is negative.

Case Report: Long-term Structural and Functional Effects of Ethambutol Optic Neuropathy

SIGNIFICANCE

This case report demonstrates reduction in the retinal nerve fiber layer (RNFL) thickness and an abnormal electroretinogram after toxic optic neuropathy from ethambutol, more than 1 year after improvements in visual acuity (VA) and visual fields (VFs) were seen. Although many studies have described complications of ethambutol, continuing reduction in RNFL thickness 2 years after discontinuation has not been described elsewhere.

PURPOSE

It is well known that ethambutol can cause optic nerve toxicity, visual impairment, and VF loss. Visual acuity can be regained after stopping the drug; however, the amount and time frame are variable. There are few data on long-term follow-up of these cases to direct clinicians how to proceed once VA has stabilized. Here we present a case with 2 years of follow-up for a patient with ethambutol toxicity, showing the condition change even after VA becomes normal.

CASE REPORT

A 61-year-old man presented shortly after discontinuing ethambutol for Mycobacterium avium complex. Visual acuity values were 20/70 in the right eye and 20/125 in the left eye with cecocentral VF scotomas. Optical coherence tomography showed normal RNFL. Visual-evoked potentials were significantly reduced and delayed. Over the course of 2 years, the patient became asymptomatic as VA and VF returned to normal and visual-evoked potential improved. However, the optical coherence tomography RNFL was reduced from each visit to the next, and the electroretinogram showed decreased scotopic and photopic amplitudes.

CONCLUSIONS

Signs of ethambutol toxicity may remain or worsen years after discontinuation, even in the absence of patient symptoms and with normal VA and VF.

Severe visual loss by inhalation of methanol

Purpose: To describe a clinical case of toxic optic neuropathy with severe visual loss caused by inhalation abuse of methanol products. Method: A 25-year-old male student was admitted to the emergency department with an acute bilateral visual loss and headaches, nausea, and cold sweats. A complete clinical and ophthalmologic examination was performed. Results: On ophthalmic examination, visual acuity (VA) was light perception in the right eye (RE) and no light perception in the left eye (LE). Pupillary examinations demonstrated dilated, non-reactive pupils. An arterial blood gas analysis showed systemic metabolic acidosis with a pH of 7.23 and Gap anion elevated. Consequently, these results were enough to provide a substantial suspicion of methanol toxicity and start the treatment. 72 hours after, he confessed that he had been inhaling methanol-based solvent for eight years. Conclusions: Methanol-induced toxicity can cause a non-reversible toxic optic neuropathy. Blood acidemia with Gap anion elevated and a suspicious fundus ophthalmic examination allows a fast diagnosis. A quick treatment based on dialysis, intravenous ethanol, sodium bicarbonate, vitamin B12, and intravenous methylprednisolone slows the secondary intoxication damages. We presented herein a procedure to identify and manage toxic optic neuropathy caused by methanol inhalation. Abbreviations: VA = Visual Acuity, RE = right eye, LE = left eye, OCT = Optical Coherence Tomography, RNFL = Retinal Nerve Fiber Layer, CT = computed tomography, MRI = magnetic resonance imaging, VEPs = visual evoked potentials.

Analysis of structural injury patterns in peripapillary retinal nerve fibre layer and retinal ganglion cell layer in ethambutol-induced optic neuropathy

BACKGROUND

We investigated structural injury patterns in the peripapillary retinal nerve fibre layer (p-RNFL) and ganglion cell inner plexiform layer (GCIPL) caused by ethambutol treatment.

METHODS

Sixty-four patients undergoing ethambutol treatment at Zhejiang Chinese Medicine and Western Medicine Integrated Hospital were recruited. Fourteen (14) exhibited visual dysfunction (abnormal group), and the remaining 50 had no visual dysfunction (subclinical group). The thickness of the p-RNFL, total macular retina layer and GCIPL were measured using Cirrus-HD Optical coherence tomography (Cirrus-HD OCT, Cirrus high-definition optical coherence tomography), and compared with 60 healthy, age-matched controls.

RESULTS

The p-RNFL thickness was similar in both subclinical and control groups. When compared with the control group, p-RNFL thickness in the abnormal group was significantly increased in the inferior and superior quadrants (GEE, P = 0.040, P = 0.010 respectively). In contrast with the subclinical group, p-RNFL thickness in the inferior quadrant was increased in the abnormal group (GEE, P = 0.047). The GCIPL thickness in the inferonasal and inferior sectors was significantly deceased in the subclinical group when compared with controls (GEE, P = 0.028, P = 0.047, respectively). The average and minimum value of GCIPL thickness, and thickness in the superonasal, inferior, inferotemporal, superotemporal and superior sectors were significantly decreased in the abnormal group when compared with controls (GEE, P = 0.016, P = 0.001, P = 0.028, P = 0.010, P = 0.012, P = 0.015, P = 0.010, respectively). The cube average macular thickness (CAMT) in the abnormal group was significantly thinner than controls (GEE, P = 0.027).

CONCLUSIONS

GCIPL measurements using Cirrus-HD OCT detected retinal ganglion cell layer loss following ethambutol treatment, before visual dysfunction occurred.

Sulthiame impairs mitochondrial function in vitro and may trigger onset of visual loss in Leber hereditary optic neuropathy

Background

Leber hereditary optic neuropathy (LHON) is the most common mitochondrial disorder and characterized by acute or subacute painless visual loss. Environmental factors reported to trigger visual loss in LHON mutation carriers include smoking, heavy intake of alcohol, raised intraocular pressure, and some drugs, including several carbonic anhydrase inhibitors. The antiepileptic drug sulthiame (STM) is effective especially in focal seizures, particularly in benign epilepsy of childhood with centrotemporal spikes, and widely used in pediatric epileptology. STM is a sulfonamide derivate and an inhibitor of mammalian carbonic anhydrase isoforms I–XIV.

Results

We describe two unrelated patients, an 8-year-old girl and an 11-year-old boy, with cryptogenic focal epilepsy, who suffered binocular (subject #1) or monocular (subject #2) visual loss in close temporal connection with starting antiepileptic pharmacotherapy with STM. In both subjects, visual loss was due to LHON. We used real-time respirometry in fibroblasts derived from LHON patients carrying the same mitochondrial mutations as our two subjects to investigate the effect of STM on oxidative phosphorylation. Oxygen consumption rate in fibroblasts from a healthy control was not impaired by STM compared with a vehicle control. In contrast, fibroblasts carrying the m.14484T>C or the m.3460G>A LHON mutation displayed a drastic reduction of the respiration rate when treated with STM compared to vehicle control.

Conclusions

Our observations point to a causal relationship between STM treatment and onset or worsening of visual failure in two subjects with LHON rather than pure coincidence. We conclude that antiepileptic medication with STM may pose a risk for visual loss in LHON mutation carriers and should be avoided in these patients.

Electrophysiology in neuro-ophthalmology

This chapter reviews common applications of visual electrophysiology relevant to neuro-ophthalmology practice. The use of standard tests and extended protocols are described including the cortical visual evoked potential and pattern and full-field electroretinogram (PERG; ERG) methods, the latter including the photopic negative response. Abnormalities of these recordings are rarely specific but provide valuable diagnostic guidance and an objective measure of visual pathway function, difficult or impossible to infer by other methods. The electrophysiological phenotypes associated with Leber hereditary optic neuropathy, OPA1- and SSBP1-associated dominant optic atrophy, and WFS1-related syndromes are described. Typical changes in retinal and optic nerve function tests associated with acquired disease are highlighted, including those related to demyelination, ischemic, compressive, nutritional and toxic, and nonorganic etiologies. The importance of complementary testing using different electrophysiological techniques is emphasized, for the purposes of differential diagnosis and in disorders that may masquerade as optic nerve pathology.

Late-stage sequela of an isolated optic neuropathy after acute magnesium valproate overdose: A case report

BACKGROUND

Magnesium valproate is a valproic acid (VPA) derivative that is widely used for the treatment of epilepsy and bipolar disorders. Acute overdose of VPA may cause complicated systemic syndromes; however, the reports of ocular sequelae caused by toxic optic neuropathy (TON) are rare.

CASE PRESENTATION

We present a case of a 19-year-old female with bilateral damage to visual function after acute VPA overdose. She was comatose and received systemic treatments for 1 month, during which she suffered a substantial loss of visual function without any evident neurological sequelae. The first recorded visual acuity was no light perception in the right eye (OD) and hand motion in the left eye (OS). Her best-corrected visual acuity improved to 20/100 OS after 4 months of hyperbaric oxygen therapy and neurotrophic treatments. Her visual field was limited to an inferior nasal area OS. Therefore, a diagnosis of TON was made. Her visual function remained stable in the left eye, but did not recover in the right eye during the 5-month follow-up. We found damage to the optic nerve pathway during ophthalmic examinations.

CONCLUSION

We report a rare case of TON caused by acute VPA overdose. Hyperbaric oxygen therapy, and neuroprotective and neurotrophic treatments might be effective at the early stage but cannot fully reverse the damage to the optic nerve. The present case indicates the potential neurotoxicity of VPA. It is crucial to determine the severity of an isolated optic nerve sequela caused by VPA overdose, though it might be rare as observed in previous reports. Further confirmation of the likelihood of its causation and its pathophysiology is needed in the future.

COVID casualty: Bilateral blindness due to ingestion of spurious sanitizer

Intentional ingestion of alcohol-based handrub (ABHR) or sanitizer solution is uncommon. The coronavirus disease-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 has led to lockdowns being put in place in many countries across the globe and resulted in a surge in ABHR usage to maintain hand hygiene. In this communication, we report the case of a 56-year-old male, a chronic alcoholic who presented during the lockdown period, with acute bilateral loss of vision following ingestion of ABHR. The handrub was found to be a nonstandardized sanitizer with no labels mentioning its constituents. Typically, the ingestion of ABHR solutions results in isopropanol or ethanol poisoning, both of which have low toxicity. Based on the clinical history and findings in our patient, a diagnosis of optic neuropathy due to accidental ingestion of sanitizer containing methyl alcohol as an unlisted ingredient was made. Our report underscores the need for strict guidelines, toxicovigilance, and surveillance systems to be in place to prevent such adulterated ABHRs from being commercially available.

Nutritional Optic Neuropathies: State of the Art and Emerging Evidences

Nutritional optic neuropathy is a cause of bilateral, symmetrical, and progressive visual impairment with loss of central visual acuity and contrast sensitivity, dyschromatopsia, and a central or centrocecal scotoma. The clinical features are not pathognomonic, since hereditary and toxic forms share similar signs and symptoms. It is becoming increasingly common due to the widespread of bariatric surgery and strict vegetarian or vegan diets, so even the scientific interest has recently increased. In particular, recent studies have focused on possible pathogenetic mechanisms, and on novel diagnostic and therapeutic strategies in order to prevent the onset, make a prompt diagnosis and an accurate nutritional supplementation, and to avoid irreversible optic nerve atrophy. Nowadays, there is clear evidence of the role of cobalamin, folic acid, thiamine, and copper, whereas further studies are needed to define the role of niacin, riboflavin, and pyridoxine. This review aims to summarize the etiology, diagnosis, and treatment of nutritional optic neuropathy, and it is addressed not only to ophthalmologists, but to all physicians who could come in contact with a patient with a possible nutritional optic neuropathy, being a fundamental multidisciplinary approach.

Prospective study to evaluate incidence and indicators for early detection of ethambutol toxicity

AIMS

To evaluate incidence of toxic optic neuropathy in patients receiving ethambutol (EMB) for 6 months and to identify its early indicators.

METHODS

We included 50 patients on anti-tubercular therapy (ATT) including EMB (HRE regimen) based on total body weight for 6 months. Best-corrected visual acuity (ETDRS), colour vision (Ishihara pseudo-isochromatic plates), contrast sensitivity (Pelli-Robson chart), Humphrey visual field analysis (HVF 30-2 SITA FAST), pattern visual evoked response (VER) and spectral-domain optical coherence tomography (SDOCT) for ganglion cell inner plexiform layer (GCIPL) and retinal nerve fibre layer (RNFL) analysis were assessed at baseline and at 2, 4 and 6 months after starting ATT.

RESULTS

Mean age of the patients was 36.5±14.7 years with male:female ratio of 2.5:1. Mean daily dosage of EMB was 17.5±1.3 mg/kg/day. No significant change was observed in visual acuity, contrast sensitivity, color vision and mean or pattern SD on HVF at 6 months. Significant increase in VER latency of >2 SD (>125 ms) was observed in 46% eyes on follow-up indicating subclinical toxicity. Significant loss of mean RNFL (from 100.79±16.05 μm to 89.96±13.79 μm) and GCIPL thickness (from 83.1±5.60 μm to 79.85±6.45 μm) was observed at 6 months (p=0.001 for both). Patients with subclinical toxicity had significantly greater damage in temporal RNFL quadrant, supero-nasal and infero-nasal GCIPL sectors compared with others.

CONCLUSION

The incidence of clinical EMB optic neuropathy was <2%, though subclinical damage in the form of increase in VER latency, and decrease in RNFL and GCIPL on OCT was seen in 46% eyes.