Ethambutol optic neuropathy

Visual Recovery Time in Patients with Ethambutol-induced Toxic Optic Neuropathy

PURPOSE

We aimed to investigate the visual recovery time in patients with ethambutol-induced toxic optic neuropathy (EON) and identify the factors associated with the visual recovery time.

METHODS

In this retrospective cohort study, we reviewed the medical records of 35 eyes from 35 patients with EON. Visual recovery was defined as a gain of three or more lines from the nadir.

RESULTS

Patients were observed following discontinuation of ethambutol (EMB), with the mean follow-up period of 21.0 ± 16.0 months. The visual acuity at nadir was logarithm of the minimum angle of resolution 1.4 ± 0.4, and the final visual acuity was logarithm of the minimum angle of resolution 0.6 ± 0.5. Twenty-seven eyes (77.1%) showed significant visual recovery. In Kaplan-Meier survival, the mean estimated time for visual recovery was 15.2 ± 3.0 months, and 50% of the patients experienced visual recovery at 8.3 ± 2.2 months following EMB discontinuation. Multivariate Cox regression analysis identified several significant risk factors for delayed visual recovery, including duration of EMB medication ≤6 months, period from symptom onset to EMB discontinuation >14 days, and baseline peripapillary retinal nerve fiber layer thickness >98 μm.

CONCLUSIONS

Our study indicated a mean time of visual recovery of 15 months for EON cases. Therefore, patients diagnosed with EON should be followed up for more than 1 to 2 years to evaluate their visual recovery. Delayed EMB discontinuation, short duration of EMB use, and initial peripapillary retinal nerve fiber layer thickening were associated with delayed visual recovery. Therefore, patients taking EMB should be followed up regularly for early detection of EON and immediate discontinuation of EMB to prevent severe damage to the optic nerve.

Optical Coherence Tomography Parameters and Optimal Cut-off Values for Predicting Visual Prognosis in Ethambutol-Induced Optic Neuropathy

BACKGROUND

The objective of this study was to evaluate the prognostic value of optical coherence tomography (OCT) parameters in patients with ethambutol-induced optic neuropathy (EON) and establish their optimal cut-off values for predicting visual acuity outcomes.

METHODS

A retrospective cross-sectional study was conducted on 64 eyes of 32 patients with EON who underwent OCT. Peripapillary retinal nerve fiber layer (pRNFL) and macular ganglion cell-inner plexiform layer (mGCIPL) thickness were measured using Cirrus high-definition OCT (HD-OCT) within 3 months after EON diagnosis. Visual acuity of patients was recorded and analyzed at the first visit, the 1-year visit, and the latest visit. Prognostic capacities of OCT parameters for visual prognosis were evaluated and their optimal cut-off values for predicting final visual acuity were established.

RESULTS

Increased pRNFL thickness was significantly associated with better visual acuity at 1 year postdiagnosis and the latest visit. A significant association was established between increased pRNFL thickness and a higher rate of recovery to visual acuity >20/25 at 1 year postdiagnosis. Receiver-operating characteristic curves identified ideal cut-off values for OCT parameters as follows: pRNFL thickness of 83 μm (sensitivity 100%, specificity 48.3%) and mGCIPL thickness of 74 μm (sensitivity 100%, specificity 83.3%) for visual acuity >20/25 at 1 year, mGCIPL thickness of 61 μm (sensitivity 85.7%, specificity 71.4%) for visual acuity >20/40 at 1 year, with corresponding AUCs exceeding 0.7.

CONCLUSIONS

Both pRNFL and mGCIPL thickness possess potential values for predicting visual outcomes in patients with EON. Future research should continue to explore the utility of OCT parameters in EON prognosis.

Metabolic Rewiring of Mycobacterium tuberculosis upon Drug Treatment and Antibiotics Resistance

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a significant global health challenge, further compounded by the issue of antimicrobial resistance (AMR). AMR is a result of several system-level molecular rearrangements enabling bacteria to evolve with better survival capacities: metabolic rewiring is one of them. In this review, we present a detailed analysis of the metabolic rewiring of Mtb in response to anti-TB drugs and elucidate the dynamic mechanisms of bacterial metabolism contributing to drug efficacy and resistance. We have discussed the current state of AMR, its role in the prevalence of the disease, and the limitations of current anti-TB drug regimens. Further, the concept of metabolic rewiring is defined, underscoring its relevance in understanding drug resistance and the biotransformation of drugs by Mtb. The review proceeds to discuss the metabolic adaptations of Mtb to drug treatment, and the pleiotropic effects of anti-TB drugs on Mtb metabolism. Next, the association between metabolic changes and antimycobacterial resistance, including intrinsic and acquired drug resistance, is discussed. The review concludes by summarizing the challenges of anti-TB treatment from a metabolic viewpoint, justifying the need for this discussion in the context of novel drug discovery, repositioning, and repurposing to control AMR in TB.

Ethambutol and visual assessment in England: current practice and recommendations

BACKGROUND

Standard treatment for tuberculosis (TB) in children and adults includes an initial two-month course of ethambutol, a drug that in rare cases can cause optic neuropathy and irreversible vision loss. There is a lack of clear guidance on what vision assessments are needed before and during treatment with ethambutol, with the Royal College of Ophthalmologists, National Institute for Health and Care Excellence, British National Formulary and British Thoracic Society offering different guidance. We aimed to assess how vision is routinely tested in patients treated with ethambutol in TB services across England.

METHODS

An online survey developed by Public Health England was sent to all TB services in England in 2018 to assess current practice and inform the development of best practice recommendations for visual assessment of patients treated with ethambutol for TB.

RESULTS

Sixty-six TB professionals from across England responded, a response rate of 54%. The results showed variations in practice, including when to omit ethambutol from treatment, the timing and frequency of visual assessment, the type of visual assessment, referral processes and management of visual changes.

CONCLUSION

This national survey highlights the need for clear guidelines on the testing of vision for patients taking ethambutol at recommended doses, before and during treatment. We suggest a pragmatic approach to visual assessment to reduce variation in practice, proposing a stepwise pathway for patients on standard TB treatment for local adaptation.

Ethambutol and its ophthalmic effects; is screening and collaboration the new way forward?

AIM

To screen patients on ethambutol and evaluate its role on visual functions and toxic optic neuropathy.

SETTING AND DESIGN

Retrospective, observational single tertiary centre cohort of 80 patients.

METHODS AND MATERIAL

A total of 69 from the initial 80 patients with visual complaints were categorised into two groups A and B; ongoing anti-tubercular therapy with ethambutol and having stopped ethambutol for greater than six months respectively. All patients underwent vision (V) testing on ETDRS chart and anterior and posterior segment evaluation. Additionally, patients in group A recorded color vision (CV) on Ishihara chart and visual evoked potential (VEP).

STATISTICAL ANALYSIS USED

P value was calculated using Chi square test (SPSS ver. 20).

RESULTS

Out of 69 patients in our study, 58 (84.05%) patients recorded reduced visual acuity. The mean visual acuity was 0.58 logMAR units. 33 out of our 58 (57%) patients with reduced visual acuity showed normal optic discs while 25 out of 58 (43%) showed altered optic discs. In group B, 14 out of 32 patients with vision of less than 20/20 also had optic disc pallor (p = 0.02). 12 out of 15 patients in group A recorded an altered color vision and also had a vision of less than 20/20 (p = 0.023). 15 patients who recorded altered VEP also had vision of less than 20/20 (p = 0.037).

CONCLUSION

Visual acuity, color vision and vep are sensitive and sustainable tools which can be implemented in regular screening. Ethambutol toxicity is a real problem and a collaborative approach is necessary to establish screening protocols and prevent ethambutol induced toxic optic neuropathy.

Medications and Monitoring in Treatment of Nontuberculous Mycobacterial Pulmonary Disease

In the treatment of nontuberculous mycobacteria (NTM) lung disease, clinicians must consider potential toxicities that may occur as a result of prolonged exposure to a multidrug antibiotic regimen. Frequent clinical and microbiological monitoring is required to assess response and guide treatment duration. This article summarizes toxicity profiles of the antibiotics that are most frequently prescribed for the treatment of NTM lung disease. The role of therapeutic drug monitoring during use of amikacin and linezolid is discussed. The available evidence to guide frequency and extent of medication monitoring during NTM treatment is provided.

Potential underlying mechanisms of ethambutol induced optic neuropathy: Evidence from in vitro to clinical studies

Ethambutol is an antibiotic widely used for treatment of Mycobacterium species. Although it is safe to use in patients, the ocular toxic impact, including optic neuropathy and retinopathy, can be observed in patients using ethambutol. After discontinuation of the drug, the ocular toxic effects can be reversible in some patients, but some are not. Ethambutol-induced optic neuropathy has been recognized for more than six decades and the prevalence of optic neuropathy from a standard dose of ethambutol has been reported as 0.7-1.29%. Several factors associated with ethambutol-induced optic neuropathy include dosage/duration of drug, the medical conditions of patients such as renal and hepatic dysfunction and preexisting mitochondrial mutations. Currently, there is no specific treatment and prevention of ethambutol-induced optic neuropathy. In addition, the potential underlying mechanisms of ethambutol-induced optic neuropathy is still unclear. Therefore, this review aimed to summarize and discuss evidence from clinical, in vitro, and in vivo studies in order to explore the potential pathophysiology of ethambutol-induced optic neuropathy. Any contradictory findings are also included and discussed. The insights gained from the review will facilitate the discovery of novel approaches for prevention and treatment of optic neuropathy-induced by ethambutol.

The Neuro-Ophthalmology of Tuberculosis

Tuberculosis (TB) is a global health concern and central nervous system (CNS) TB leads to high mortality and morbidity. CNS TB can manifest as tubercular meningitis, tuberculoma, myelitis, and arachnoiditis. Neuro-ophthalmological involvement by TB can lead to permanent blindness, ocular nerve palsies and gaze restriction. Visual impairment is a dreaded complication of tubercular meningitis (TBM), which can result from visual pathway involvement at different levels with varying pathogenesis. Efferent pathway involvement includes cranial nerve palsies and disorders of gaze. The purpose of this review is to outline the various neuro-ophthalmological manifestations of TB along with a description of their unique pathogenesis and management. Optochiasmatic arachnoiditis and tuberculomas are the most common causes of vision loss followed by chronic papilloedema. Abducens nerve palsy is the most commonly seen ocular nerve palsy in TBM. Gaze palsies with deficits in saccades and pursuits can occur due to brainstem tuberculomas. Corticosteroids are the cornerstone in the management of paradoxical reactions, but other immunomodulators such as thalidomide and infliximab are being explored. Toxic optic neuropathy caused by ethambutol necessitates careful monitoring and immediate drug discontinuation. Cerebrospinal fluid diversion through ventriculo-peritoneal shunting may be required in patients with hydrocephalus in stage I and II of TBM to prevent visual impairment. Early diagnosis and prompt management are crucial to prevent permanent disability. Prevention strategies, public health initiatives, regular follow-up and timely intervention are essential in reducing the burden of CNS TB and its neuro-ophthalmological complications.

Linezolid optic neuropathy

PURPOSE OF REVIEW

In this article, we reviewed 67 reported cases of linezolid optic neuropathy and describe the common characteristics and expectations for recovery with an emphasis on recent findings in the literature.

RECENT FINDINGS

Linezolid classically causes a reversible, duration-dependent optic neuropathy. However, in our review, we found only 66.7% of patients recovered complete visual function. Vision loss most commonly affected visual acuity followed by visual field and color vision. We also found patients taking higher doses of linezolid experienced full recovery less often, suggesting a dose-dependent component of linezolid optic neuropathy. Linezolid use has increased in frequency and duration, especially in the treatment of drug-resistant tuberculosis, and data indicate that these patients experience lower rates of complete vision recovery compared with patients taking linezolid for other indications.

SUMMARY

Linezolid is an effective medication for treating drug-resistant infections; however, it may result in optic neuropathy. It is reasonable for patients on linezolid to undergo screening examinations, especially those on higher doses or for prolonged duration of therapy.

Ethambutol-induced optic neuropathy

PURPOSE

A case report of a 40-year-old patient with tuberculosis treated with ethambutol is described. Within six months of starting treatment, there was a painless sudden decline in visual function. Despite the known complications of ethambutol treatment, it was discontinued after another three months.

METHODS

In the case report, we highlight the damage to the dominantly peripheral visual pathways. Using electrophysiological examinations, we showed a significant alteration in the optic nerves. Optical Coherence Tomography (OCT) showed progressive loss of vessel density and nerve fibre layer of retinal ganglion cells. Perimetric examination showed both a central decrease in sensitivity and mainly scotomas in the temporal parts of the visual fields. Although there was improvement in visual fields over time, OCT findings indicated progression of ethambutol-induced optic neuropathy (EON). Magnetic Resonance Imaging confirmed the alteration in the peripheral part of the visual pathway (intraorbital, intracranial parts of optic nerves, chiasma, and optic tracts).

CONCLUSION

Even though EON is not an unknown complication, new cases still occur and, unfortunately, with an irreversible course. Therefore, it is important to draw attention constantly to this complication and to consider it not only in ophthalmologists' surgeries.

Factors Affecting Visual Recovery in Patients with Ethambutol-Induced Optic Neuropathy

Purpose

To study visual recovery and identify the factors that may affect it in patients with ethambutol-induced optic neuropathy (EON).

Patients and Methods

Medical charts of patients who developed optic neuropathy after ethambutol (EMB) treatment for tuberculosis infection were retrospectively reviewed. Demographic details and clinical data were examined to assess visual recovery after discontinuation of ethambutol treatment. The univariate and multivariate relationships between various factors and visual recovery were evaluated using regression analysis.

Results

Of 5394 patients diagnosed with tuberculosis infection and treated with EMB, 23 patients (0.43%) were diagnosed with EON. Logistic regression analysis found that female sex was the categorical factor significantly associated with good visual recovery with an odds ratio of 12.0 (95% confidence interval 1.56, 92.29; p = 0.02), while linear regression analysis identified good initial visual acuity as the numerical factor significantly related with it (p < 0.001). After adjustment with multivariate analysis, initial visual acuity was found to be the only significant factor associated with visual recovery. All patients with initial visual acuity of better than 20/200 at first visit achieved good visual recovery.

Conclusion

The incidence of EON in patients treated with EMB was 0.43% in this hospital-based study. Good visual recovery was noted in 39.13% of these patients, and initial visual acuity was the factor that affected visual recovery. It is recommended that patients on EMB have regular screening by an ophthalmologist for early detection of the disease, and if it is discovered, that the use of the drug be immediately discontinued in order to prevent potentially devastating visual loss.

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.

Delayed and reversible ethambutol optic neuropathy

Purpose

To document an unusual example of ethambutol optic neuropathy developing three years from treatment start date in the absence of renal dysfunction.

Observations

The patient, an 82-year-old, 61-kg male undergoing treatment for Mycobacterium Avium Complex, presented with visual acuity that was significantly worse than baseline three years after beginning a treatment regimen which included ethambutol at <15 mg/kg/day. He was also found to have central and paracentral scotomas in both eyes. Ethambutol treatment was immediately halted, and the patient's visual acuity and visual fields improved in the months following.

Conclusions and Importance

It is important to have a high index of suspicion for ethambutol toxicity in any patient on this drug who presents with vision changes consistent with optic neuropathy. The development of ethambutol optic neuropathy can be delayed, and vision loss may be reversible and can continue to improve over months after cessation of therapy.

The Genetics of Ethambutol-Induced Optic Neuropathy: A Narrative Review

Tuberculosis (TB) is a global health problem with the major brunt of disease occurring in developing countries. The cornerstone of treatment of TB is anti-tubercular therapy (ATT), which includes rifampicin, isoniazid, pyrazinamide and ethambutol. Because of emerging drug resistance, treatment failures, defaulters and increasing incidence of disseminated and extrapulmonary TB, the guidelines have been modified in some countries. Ethambutol is prescribed for longer times (in some cases >8 months) and hence the incidence of ethambutol-induced optic neuropathy (EtON) is expected to rise. The fundamental question which needs explanation is why only a small subset of patients on ethambutol are prone to develop loss of vision. This review focuses on available genetic studies which provide evidence that mitochondria are the likely substrates involved in the final pathway of reactive oxidative damage of the papillo-macular bundle. Genetic analysis of mitochondrial mutations encoding genes involved in oxidative phosphorylation pathways may help in isolating the subset of patients who are genetically susceptible. If the groups having high risk of developing EtON are recognised then prolonged duration of ethambutol treatment can be avoided in these susceptible individuals. A better understanding of the pathophysiology will also pave the way for the development of management strategies in this condition.

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.

Asymmetric Synthesis of N-Substituted 1,2-Amino Alcohols from Simple Aldehydes and Amines by One-Pot Sequential Enzymatic Hydroxymethylation and Asymmetric Reductive Amination

The chiral N-substituted 1,2-amino alcohol motif is found in many natural and synthetic bioactive compounds. In this study, enzymatic asymmetric reductive amination of α-hydroxymethyl ketones with enantiocomplementary imine reductases (IREDs) enabled the synthesis of chiral N-substituted 1,2-amino alcohols with excellent ee values (91-99 %) in moderate to high yields (41-84 %). Furthermore, a one-pot, two-step enzymatic process involving benzaldehyde lyase-catalyzed hydroxymethylation of aldehydes and subsequent asymmetric reductive amination was developed, offering an environmentally friendly and economical way to produce N-substituted 1,2-amino alcohols from readily available simple aldehydes and amines. This methodology was then applied to rapidly access a key synthetic intermediate of anti-malaria and cytotoxic tetrahydroquinoline alkaloids.

BTS clinical statement for the diagnosis and management of ocular tuberculosis

The BTS clinical statement for the diagnosis and management of ocular tuberculosis (TB) draws on the expertise of both TB and and ophthalmic specialists to outline the current understanding of disease pathogenesis, diagnosis and management in adults. Published literature lacks high-quality evidence to inform clinical practice and there is also a paucity of data from animal models to elucidate mechanisms of disease. However, in order to improve and standardise patient care, this statement provides consensus points with the currently available data and agreed best practice.

Inflammatory eye disease: An overview of clinical presentation and management

Inflammatory eye diseases are responsible for a significant proportion of presentations to ophthalmic emergency facilities and knowledge of how to differentiate between broad categories of disease and refer accordingly is important for the practising physician. This review aims to provide an overview of inflammatory eye disease, with a focus on clinical presentation, diagnosis and management.

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.

Adverse Drug Reactions Related to Treatment of Drug-Susceptible Tuberculosis in Brazil: A Prospective Cohort Study

Standard anti-tuberculosis treatment is highly effective, but a great challenge is the management of adverse drug reactions (ADR). Our study aimed to characterize ADR according to type, severity and time of occurrence. A prospective tuberculosis (TB) cohort has been followed, from 2010 to 2016, at a reference center in Rio de Janeiro, Brazil. Clinical and laboratory tests information were collected in all visits. ADR were described according to the affected organ/system, classified as clinical and/or laboratory, early (first 2 months) or late. ADR’s causality and intensity were assessed. In our study 552 patients were included, 78.8% presented at least one ADR, 34% were people living with HIV (PLHIV). Most ADR were clinical (53%), early (82.5%), mild/moderate (88.7%) events and of “metabolic annutritional disorders” category. There were no significant differences in type, severity or causality between “early” and “late” groups. However, “early” group presented a higher frequency of “metabolic and nutritional disorders” (27.8%) and “gastrointestinal system disorders” (23.5%), while “skin and appendages disorders” were more frequent in the “late” group. ADR are frequent and occur at any time during treatment, although the majority are early and grade and not severe.

Ethambutol-induced optic neuropathy with rare bilateral asymmetry onset: A case report

BACKGROUND

Ethambutol-induced optic neuropathy (EON) most commonly manifests as bilateral symmetrical loss of vision and often cause serious and irreversible visual impairment because of the lack of early detection and effective treatment. We followed a case of EON with rare binocular asymmetric clinical manifestations and observed the changes of visual function and retinal structure after drug withdrawal, so as to further understand the clinical characteristics of this disease.

CASE SUMMARY

A 54-year-old man complained of gradual visual decline in the left eye. The patient presented with best-corrected visual acuity of 20/20 in the right eye and 20/50 in the left eye. Color vision examination revealed difficulty in reading green color plates in the left eye. The visual field manifested as concentric contraction in the left eye. After nearly a month of drug withdrawal, the right eye had a similar decline in visual function. At the last visit, 19 mo after drug withdrawal, the visual function significantly recovered in both eyes. During follow-up optical coherence tomography (OCT) examination, both eyes manifested the thickness of the retinal nerve fiber layer from mild thickening to thinning and finally temporal atrophy, and the ganglion cell-inner plexiform layer showed significant thinning. The difference was that a reversible structural disorder in the outer retina of the nasal macula was detected in the left eye by macular high-definition OCT.

CONCLUSION

Nephropathy and high blood pressure, which damage the retinal microcirculation, may cause damage to the outer layer of the retina. Ethambutol may influence photoreceptor as well as retinal ganglion cells.

The ocular adverse effects of oral drugs

Some commonly prescribed drugs have ocular adverse effects. Many parts of the eye can be affected by oral drugs. Some ocular adverse effects may be reversed with medical or surgical intervention whereas other drugs may cause irreversible loss of vision

The risk of visual loss can be reduced by a number of approaches, including monitoring for ocular toxicity, reducing the drug dose, or stopping the drug and looking for an alternative. This can be supported by good communication between the prescribing clinician and ophthalmologist

Infrequent or delayed ocular adverse effects may not be identified in clinical trials of new drugs. Reporting adverse events is therefore important

Asymptomatic occlusive retinal vasculitis in newly diagnosed active tuberculosis

Introduction

Worldwide, tuberculosis is the leading cause of death from an infectious disease. Ocular involvement can cause significant and permanent vision loss. Ocular manifestations of tuberculosis often present with visual symptoms. Asymptomatic ocular tuberculosis is uncommon and yet can have serious consequences if missed.

Case report

An immunocompetent 26-year-old Filipino man living in regional Australia who was diagnosed with active pulmonary tuberculosis and started on antitubercular therapy. He was referred to an ophthalmologist for baseline ethambutol screening to exclude pre-existing optic neuropathy. Despite having no visual symptoms, when examined, the patient had vision threatening occlusive retinal vasculitis. He was initially commenced on localised therapy via bevacizumab intravitreal injections and retinal photocoagulation. Following completion of antitubercular therapy, high dose prednisone was commenced and slowly tapered.

Conclusions

We present the case of an asymptomatic sight threatening occlusive vasculitis that was discovered on pre-treatment ophthalmology review. This case emphasises the need for referral for full ophthalmic screening in newly diagnosed tuberculosis to exclude vision-threatening complications.

Bilateral optic neuritis as a first presentation of lymph node tuberculosis

Tuberculosis (TB) may affect the nervous system in many ways. We describe an immunocompetent teenage girl with lymph node TB who had first presented with bilateral optic neuritis. Detailed history identified features inconsistent with immune-mediated optic neuritis. Several unusual features prompted further investigation, including transient visual obscurations without raised intracranial pressure, prominent disc swelling and absence of laboratory findings to support an immune-mediated cause. Whole body PET/MR imaging identified widespread mediastinal and supraclavicular lymphadenopathy. Despite no known TB contacts, a negative interferon gamma release assay and a normal chest X-ray, a targeted lymph node biopsy confirmed TB.

Drastically Progressive Ethambutol-induced Optic Neuropathy after Withdrawal of Ethambutol: A Case Report and Literature Review

Ethambutol-induced optic neuropathy (EON) is a well-known complication, although low-dose ethambutol seldom causes EON. An 85-year-old man with non-tuberculous mycobacterial lung disease was taking antibiotics, including low-dose ethambutol. On day 85 of treatment, the diagnosis of EON was made. Despite prior discontinuation, his best corrected visual acuity drastically deteriorated from 20/17 (right eye) and 20/20 (left eye) to 20/330 (right eye) and 20/1,000 (left eye) within 3 weeks, and this symptom did not resolve. To our knowledge, there have been no reported cases with drastically progressing and irreversible EON even after the withdrawal of low-dose and short-term ethambutol.

Ocular Complaints, Disease, and Emergencies in the General Medical Setting

Primary care physicians see nearly half of all clinical visits, and 2% to 3% of those are for eye complaints. Taking a good ocular history is essential to establishing the diagnosis. Patient complaints fall into several categories including visual change, redness, and pain. Primary care physicians can screen for patients at risk of vision loss from glaucoma, diabetes, and toxic medication and ensure that patients have appropriate eye evaluations. Examination techniques such as direct ophthalmoscopy, evaluation of the red reflex, eversion of the upper lid, checking pupillary response, and using fluorescein to stain the cornea are helpful in evaluating patients' ocular complaints.

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.

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.

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.

Infectious Optic Neuropathies

PURPOSE OF REVIEW

This article reviews common infectious optic neuropathies, focusing on the more common and globally important entities.

RECENT FINDINGS

Novel infections continue to emerge and drift geographically over time; not infrequently, these have important neurologic or ocular features. Malarial retinal findings comprise a relatively specific set of findings and serve as an invaluable aid in the diagnosis of cerebral malaria. Therapy continues to evolve and is best formulated in concert with an infectious disease expert.

SUMMARY

Infectious optic neuropathies are less common than inflammatory or ischemic optic neuropathies; may present with varied, overlapping, and nonspecific clinical appearances; and comprise an important differential consideration demanding specific therapy.

Neuro-Ophthalmic Manifestations of HIV Infection

Purpose: To review the broad spectrum of clinical neuro-ophthalmic presentations associated with human immunodeficiency virus (HIV) infection. Methods: Critical review of the literature regarding neuro-ophthalmic consequences of HIV infection and its sequelae. Results: Neuro-ophthalmological diseases are common in both asymptomatic HIV-positive patients and those who profound immunosuppression with acquired immune deficiency syndrome (AIDS). Neuro-ophthalmic manifestations of HIV infection can involve the afferent or efferent visual pathway. Common clinical presentations include headache, papilledema, chorioretinitis, optic nerve involvement, meningitis, and cranial nerve palsies. Other neuro-ophthalmic manifestations include involvement of the visual pathway in the brain producing visual field defects such as occur in progressive multifocal encephalopathy. Pupil abnormalities have also been reported. Discussion: Neuro-ophthalmic consequences of HIV are important to recognize as it is critical to identify underlying neoplastic or infectious diseases which could be amenable to treatment.

Neuromyelitis optica spectrum disorder and active tuberculosis

Tuberculosis is on the rise again. It brings with it potential for neurological involvement both as a direct infection and as a parainfectious process. Accordingly we report the development of neurological problems affecting a 48-year-old patient's vision and sensation while being treated for active tuberculosis. At its nadir her vision deteriorated to nil perception of light and she had a sensory level to T10. Neuromyelitis optica spectrum disorder was diagnosed. We discuss our management strategy with neuromodulation in the context of active tuberculosis infection.

[Drug-induced toxic optic neuropathy]

Drug-induced optic neuropathy is a group of disorders in which medications cause degeneration of the optic nerve. The true prevalence of drug-induced neuropathy has not been studied, although the percentage of patients who develop optic nerve damage is known for individual medications. The common pathophysiological mechanisms are believed to be mitochondrial damage and imbalance of intracellular and extracellular free radical homeostasis. Typical symptoms of drug-induced neuropathy are reduced visual acuity in the central area, which is often bilateral, visual field disturbances, dyschromatopsia, and edema of the optic nerve head. Early detection of drug-induced optic neuropathy can potentially prevent or minimize serious complications. For patients who develop drug-induced optic neuropathy, treatment is based on timely diagnosis and cancellation of the provoking drug. In most patients, vision usually recovers a few weeks or months after discontinuation of previous therapy, but there have been cases of irreversible vision loss. In addition to withdrawal of the drug that caused optic nerve lesion, treatment of drug-induced neuropathy may include use of drugs and treatment methods prescribed by neurologists for peripheral neuropathy, however, such treatment is seldom based on evidence.

Role of ethambutol and rifampicin in the treatment of Mycobacterium avium complex pulmonary disease

Background

A three-drug regimen (macrolide, ethambutol, and rifampicin) is recommended for the treatment of Mycobacterium avium complex pulmonary disease (MAC-PD). Although macrolide has proven efficacy, the role of ethambutol and rifampicin in patients without acquired immune deficiency syndrome is not proven with clinical studies. We aimed to clarify the roles of ethambutol and rifampicin in the treatment of MAC-PD.

Methods

Patients treated for MAC-PD between March 1st, 2009 and October 31st, 2018 were reviewed retrospectively. Rates of culture conversion, microbiological cure, treatment failure, and recurrence were compared according to the maintenance (≥6 months) of ethambutol or rifampicin with macrolide.

Results

Among the 237 patients, 122 (51.5%) maintained ethambutol and rifampicin with macrolide, 58 (24.5%) maintained ethambutol and macrolide, 32 (13.5%) maintained rifampicin and macrolide, and 25 (10.6%) maintained macrolide only. Culture conversion was reached for 190/237 (80.2%) patients and microbiological cure was achieved for 129/177 (72.9%) who completed the treatment. Treatment failure despite ≥12 months of treatment was observed in 66/204 (32.4%), and recurrence was identified in 16/129 (12.4%) who achieved microbiological cure. Compared with maintenance of macrolide only, maintenance of ethambutol, rifampicin or both with macrolide were associated with higher odds of culture conversion [odds ratio (OR), 95% confidence interval (CI): 18.06, 3.67–88.92; 15.82, 2.38–105.33; and 17.12, 3.93–74.60, respectively]. Higher odds of microbiological cure were associated with maintenance of both ethambutol and rifampicin with macrolide (OR, 95% CI: 5.74, 1.54–21.42) and macrolide and ethambutol (OR, 95% CI: 5.12, 1.72–15.24) but not macrolide and rifampicin. Maintenance of both ethambutol and rifampicin with macrolide was associated with lower odds of treatment failure (OR, 95% CI: 0.09, 0.01–0.53) compared with macrolide only, while maintenance of one of these with macrolide was not. Maintenance of both ethambutol and rifampicin or one of these with macrolide did not decrease the probability of recurrence when compared with macrolide only.

Conclusions

Maintenance (≥6 months) of ethambutol and rifampicin with macrolide was associated with the most favorable treatment outcomes among patients with MAC-PD. Given the association between ongoing ethambutol use and microbiological cure, clinicians should maintain ethambutol unless definite adverse events develop.

Toxic-Metabolic and Hereditary Optic Neuropathies

PURPOSE OF REVIEW

The diagnosis of visual loss from toxic-metabolic and hereditary optic neuropathies may be delayed in some cases because of a failure to elicit important information in the clinical history or to recognize typical examination findings. An understanding of the features specific to each type of toxic-metabolic and hereditary optic neuropathy, and of the underlying mechanism of insult to the optic nerve, could lead to earlier recognition, diagnosis, and treatment (when available).

RECENT FINDINGS

Understanding of the role of mitochondria in toxic-metabolic and hereditary optic neuropathies is growing, particularly regarding the mechanism of insult of certain agents (medications and toxins) and of vitamin B12 deficiency. New developments in the quest for treatment for hereditary optic neuropathy, specifically Leber hereditary optic neuropathy, are being seen.

SUMMARY

Toxic-metabolic and hereditary optic neuropathies present in a similar fashion, with painless, progressive, bilateral visual loss with dyschromatopsia and cecocentral visual field defects. The associated retinal ganglion cell and axonal loss is typically due to mitochondrial dysfunction caused by an exogenous agent (toxic), by insufficient or deficient substrate (metabolic or nutritional), or by abnormal proteins or mitochondrial structure determined by a genetic mutation (hereditary).

Neurological and Psychiatric Adverse Effects of Antimicrobials

Antimicrobials are a widely used class of medications, but several of them are associated with neurological and psychiatric side effects. The exact incidence of neurotoxicity with anti-infectives is unknown, although it is estimated to be < 1%. Neurotoxicity occurs with all classes of antimicrobials, such as antibiotics, antimycobacterials, antivirals, antifungals and antiretrovirals, with side effects ranging from headaches, anxiety and depression to confusion, delirium, psychosis, mania and seizures, among others. It is important to consider these possible side effects to prevent misdiagnosis or delayed treatment as drug withdrawal can be associated with reversibility in most cases. This article highlights the different neurotoxic effects of a range of antimicrobials, discusses proposed mechanisms of onset and offers general management recommendations. The effects of antibiotics on the gut microbiome and how they may ultimately affect cognition is also briefly examined.

The effects of lutein on optic nerve injury induced by ethambutol and isoniazid: an experimental study

AIM

Ethambutol and isoniazid are two major effective first line agents in tuberculosis treatment having some visual adverse effects. We aimed to determine the protective effects of lutein on oxidative optic neuropathy induced by ethambutol and isoniazid in an experimental model.

MATERIAL AND METHOD

Totally 24 albino Wistar male rats were assigned into 4 groups, with 6 rats in each group as follows: healthy controls (HC group), 50 mg/kg ethambutol +50 mg/kg isoniazid administered group (EI), 0.5 mg/kg lutein +50 mg/kg ethambutol +50 mg/kg isoniazid administered group (LEI-05) and only Lutein (0.5 mg/kg) (LUT group) administered group. From the blood samples and tissues obtained from the rats, Malondialdehyde (MDA), total glutathione (GSH), interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) levels were studied. Histopathological evaluations were performed at the end of the study.

RESULTS

Serum and tissue IL-1β, TNF-α and MDA levels were the highest in EI group which were significantly lower in lutein administered group. On the other hand, serum and tissue total GSH levels were the lowest in EI group which were significantly higher in Lutein administered group. In histopathological evaluations, there were significant differences between EI group and all other three groups with edema and hemorrhage in connective tissue covering optic nerve, dilated and congested capillary, decrease in astrocytes and oligodendrocytes.

CONCLUSION

Isoniazid and ethambutol induced toxic optic neuropathy although not common, may have some potential devastating effects on vision. Lutein is determined as an effective agent in prevention of isoniazid and ethambutol induced toxic optic neuropathy.