Incidence of ethambutol-related visual impairment during treatment of active tuberculosis [Review article]

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.

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-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.

The efficient induction of human retinal ganglion-like cells provides a platform for studying optic neuropathies

Retinal ganglion cells (RGCs) are essential for vision perception. In glaucoma and other optic neuropathies, RGCs and their optic axons undergo degenerative change and cell death; this can result in irreversible vision loss. Here we developed a rapid protocol for directly inducing RGC differentiation from human induced pluripotent stem cells (hiPSCs) by the overexpression of ATOH7, BRN3B, and SOX4. The hiPSC-derived RGC-like cells (iRGCs) show robust expression of various RGC-specific markers by whole transcriptome profiling. A functional assessment was also carried out and this demonstrated that these iRGCs display stimulus-induced neuronal activity, as well as spontaneous neuronal activity. Ethambutol (EMB), an effective first-line anti-tuberculosis agent, is known to cause serious visual impairment and irreversible vision loss due to the RGC degeneration in a significant number of treated patients. Using our iRGCs, EMB was found to induce significant dose-dependent and time-dependent increases in cell death and neurite degeneration. Western blot analysis revealed that the expression levels of p62 and LC3-II were upregulated, and further investigations revealed that EMB caused a blockade of lysosome-autophagosome fusion; this indicates that impairment of autophagic flux is one of the adverse effects of that EMB has on iRGCs. In addition, EMB was found to elevate intracellular reactive oxygen species (ROS) levels increasing apoptotic cell death. This could be partially rescued by the co-treatment with the ROS scavenger NAC. Taken together, our findings suggest that this iRGC model, which achieves both high yield and high purity, is suitable for investigating optic neuropathies, as well as being useful when searching for potential drugs for therapeutic treatment and/or disease prevention.

Incidence, risk factors and ophthalmic clinical characteristic of ethambutol-induced optic neuropathy: 7-year experience

Background

The purpose of this research was to investigate the characteristics, clinical manifestations, incidence, and risk factors in ethambutol-induced optic neuropathy (EON) in the Thai population.

Methods

Patients treated with ethambutol for tuberculosis (TB) were retrospectively identified in the medical record of a tertiary hospital in Thailand from January 2012 to August 2019. Development of EON was determined through review of ophthalmology records. Comparison was made between patients with EON and those without EON to identify possible risk factors. Ophthalmic outcomes were characterized.

Results

Among 4,141 patients who received ethambutol for TB treatment, 1,062 had an ophthalmology encounter, and 20 (0.5% overall, 1.88% with ophthalmology encounters) developed EON. In unadjusted analysis, compared to patients without EON, those with EON had a similar daily dose, but longer duration of ethambutol treatment (P=0.02). They were older (mean 43.74 vs. 58.60 years, P=0.001), more likely to have hypertension (P=0.02) and smoke (p=0.01). There were no differences in gender, body mass index, diabetes, dyslipidemia, HIV infection or glomerular filtration rate. The peripapillary retinal nerve fiber layer, ganglion cell analysis, and vascular density as measured using retinal optical coherence tomography were impacted by EON. In adjusted logistic regression analysis, age greater than 60 (OR = 8.71, p = 0.01) and smoking (OR = 7.06, p = 0.01) were independent risk factors for EON.

Conclusion

In patients treated with ethambutol, the incidence proportion of EON was 0.5% among those with ethambutol administered and 1.88% among those with ethambutol and an eye visit. Potential EON risk factors were age, hypertension, smoking, and duration of ethambutol medication. Smoking has not been associated with EON in prior studies.

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.

Clinical Characteristics and Outcomes in Chronic Kidney Disease Patients with Tuberculosis in China: A Retrospective Cohort Study

Background

The diverse manifestations of tuberculosis (TB) in chronic kidney disease (CKD) patients can cause difficulty in diagnosis, delayed treatment, even death. Therefore, this study investigated the clinical characteristics and the risk factors for mortality in CKD patients with TB.

Methods

This retrospective study included 167 patients diagnosed with active TB at two tertiary medical centers in Chongqing within six years. Clinical characteristics and outcomes of anti-TB treatment in patients with and without CKD were collected, and the predictive mortality values of variables were analyzed.

Results

Of the 167 patients, 66.7% (44/66) hemodialysis (HD), 41.1% (21/51) pre-HD, and 32.0% (16/50) non-CKD patients had extrapulmonary TB. The pleura and lymph node were the common sites in CKD patients. Clinical presentations of cough and hemoptysis in CKD patients were less common than those in non-CKD patients, 13.7% (16/117) of CKD patients even not having any clinical symptoms. The positive rates of tuberculin skin test, TB-polymerase chain reaction and acid-fast bacilli in sputum in HD patients were lower than those in pre-HD and non-CKD patients (p<0.05). CKD patients were more prone to gastrointestinal and neurological side effects during anti-TB treatment. The mortality rates of non-CKD, pre-HD and HD patients was 6.1%, 31.9% and 37.3%, respectively. Multivariate Cox analysis revealed that age≥40 years (HR: 5.871; p=0.019), hypoalbuminemia (HR:2.879; p=0.004), CKD stage 4–5 (HR:4.719; p=0.018) and HD (HR:6.13; p=0.005) were associated with mortality.

Discussion

CKD patients with TB have atypical clinical manifestations and high mortality. Age, hypoalbuminemia, CKD stage 4–5, and HD were independent predictors of mortality.

From Scylla to Charybdis: Fixed drug combinations for tuberculosis and increased ethambutol-induced optic neuropathy in India

Purpose

To describe the increase in prevalence of ethambutol-induced optic neuropathy (EON) in patients presenting to a single tertiary referral eye care center in India after introduction of weight-based fixed dose combinations and an increase in duration of ethambutol use from 2016 in the Revised National Tuberculosis Control Program.

Methods

This was a retrospective, observational, referral hospital-based study of 156 patients with a diagnosis of EON presenting to a single tertiary referral eye care center between January 2016 and December 2019. The main outcome measure was to assess the increase in prevalence of EON cases presenting to our tertiary care institute.

Results

During the 4-year study period, 156 new patients were diagnosed with EON. A total of 101 patients (64.7%) were males and 55 (35.3%) were females. The most common age group affected was 41-60 years. The significant complaint at presentation was decreased vision in all the patients. A rising trend in the number of patients diagnosed as EON was seen, with the prevalence increasing from 16 cases in 2016, 13 cases in 2017, and 31 cases in 2018 to 96 cases in 2019.

Conclusion

The results of this study indicated an alarming increase in the trend of EON cases presenting to our tertiary care institute.

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.

Treatment in Latent Tuberculosis Uveitis-Is Immunosuppression Effective or Is Conventional 3- or 4-Drug Antituberculosis Therapy Mandatory?

Background/Aims: Controversy exists regarding 3- or 4 drug antituberculosis therapy (conventional ATT) in uveitis patients having latent tuberculosis (LTB), especially while initiating therapy with corticosteroids and/or other immunosuppressants. Methods: We performed a monocentral retrospective analysis of posterior uveitis patients with latent TB. Latent TB was diagnosed, in case of a positive QuantiFERON®-TB-Gold test and normal chest imaging, after ruling out other causes of infectious and noninfectious uveitis. Patients with active TB were excluded. From 2016 to 2020 we included 17 patients. Ophthalmological evaluation consisted of Best corrected visual acuity (BCVA), slit lamp examination, fundoscopy, OCT, and fluorescein- and indocyaningreen- angiography before and at months 3, 6, 12, 24, and the last follow-up after treatment. Results: Initially, all patients had active posterior uveitis with occlusive (n = 5 patients) and nonocclusive retinal vasculitis (n = 12 patients). Mean follow up was 28 ± 15 months. Therapy was started with systemic corticosteroids (mean prednisolone equivalent 71.3 mg/d) and already after 3 months it could be tapered to a mean maintenance dosage of 8.63 mg/d. Additional immunosuppressive treatment with cs- or bDMARDs was initiated in 14 patients (82%) due to recurrences of uveitis while tapering the corticosteroids <10 mg per/day or because of severe inflammation at the initial visit. While being on immunosuppression, best corrected visual acuity increased from 0.56 logMAR to 0.32 logMAR during follow-up and only three patients had one uveitis relapse, which was followed by switch of immunosuppressive treatment. As recommended, TB prophylaxis with 300 mg/d isoniazid was administered in 11 patients for at least 9 months while being on TNF-alpha-blocking agents. No patient developed active tuberculosis during immunosuppressive therapy. Conclusion: Mainly conventional ATT is strongly recommended—as monotherapy or in combination with immunosuppressives—for effective treatment in patients with uveitis due to latent TB. Although in our patient group no conventional ATT was initiated, immunosuppression alone occurred as an efficient treatment. Nevertheless, due to possible activation of TB, isoniazid prophylaxis is mandatory in latent TB patients while being on TNF-alpha blocking agents.

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.

Campimetry and visual changes after RHZE treatment for tuberculosis

Background

Tuberculosis (TB) caused by Mycobacterium tuberculosis has a high prevalence in Brazil (Global tuberculosis report 2020. Geneva: World Health Organization; 2020). The ethambutol-induced optic neuropathy damage is partly reversible, making its early diagnosis essential to reduce permanent visual damage.

Purpose

To observe alterations in the computerized campimetry, Ishihara test and visual acuity secondary to rifampicin, isoniazid, pyrimethamine, ethambutol (RHZE) treatment.

Methods

Patients undergoing treatment with RHZE at the tuberculosis service of the Federal University of São Paulo were recruited from March 2019 to December 2020. The best-corrected visual acuity (VA) measurements, Ishihara test and visual fields were performed at baseline, monthly, until 2 weeks after treatment.

Results

Twenty-five patients were included. The VA decreased significantly (P = 0.0129) post-treatment compared to month 1. The mean deviation (MD) did not decrease significantly (P > 0.05); the pattern standard deviation (PSD) decreased post-treatment compared to month 1 (P = 0.0371). Changes in the Ishihara test increased significantly (P < 0.0001) in the second month.

Conclusion

The VA and PSD decreased significantly after RHZE treatment. Changes in the Ishihara test were observed in the second month.

Trial registration: The Research Ethics Committee of Federal University of São Paulo, Paulista School of Medicine approved the study in March 2019. CAAE 04297018.4.0000.5505.

Analysis of Peripapillary Vessel Density in Ethambutol-induced Optic Neuropathy Using Optical Coherence Tomography Angiography

Purpose: To investigate the changes in peripapillary and macular vessel density in ethambutol-induced optic neuropathy using optical coherence tomography angiography (OCTA).Methods: The medical records of patients diagnosed with ethambutol-induced optic neuropathy were analyzed retrospectively. Patient age, sex, daily dose (mg/day/kg), treatment duration, best-corrected visual acuity (logMAR), color vision (Ishihara color plate tests), and mean deviation of visual field test were evaluated in non-pathological individuals with age and sex controlled as the normal control group. Peripapillary retinal nerve fiber layer (RNFL) thickness, macular ganglion cell/inner plexiform layer (GC/IPL) thickness, radial peripapillary capillary (RPC) density, and macular superficial capillary plexus (SCP) density were also compared between the patient and control groups.Results: The study included 22 patient eyes and 31 control group eyes. Comparing the OCTA results between the groups, there were no significant differences in peripapillary RNFL thickness, but the temporal RPC density was significantly (p = 0.025) lower in the patient group (48.00 ± 8.23%) than in controls (52.39 ± 5.58%). For macular structures, the mean GC/IPL thickness and whole SCP density were lower in the patients (p = 0.001 and p = 0.008, respectively). In the patients, the changes in peripapillary RNFL thickness and RPC density were significantly positively correlated (r = 0.811, p < 0.001), as were the mean macular GC/IPL thickness and whole SCP density (r = 0.445, p = 0.037).Conclusions: Patients with ethambutol-induced optic neuropathy had significantly lower temporal RPC and macular SCP densities. Ethambutol toxicity may affect not only axonal degeneration but also peripapillary and macular vascular function.

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.

Memantine and its benefits for cancer, cardiovascular and neurological disorders

Memantine is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist that was initially indicated for the treatment of moderate to severe Alzheimer's disease. It is now also considered for a variety of other pathologies in which activation of NMDA receptors apparently contributes to the pathogenesis and progression of disease. In addition to the central nervous system (CNS), NMDA receptors can be found in non-neuronal cells and tissues that recently have become an interesting research focus. Some studies have shown that glutamate signaling plays a role in cell transformation and cancer progression. In addition, these receptors may play a role in cardiovascular disorders. In this review, we focus on the most recent findings for memantine with respect to its pharmacological effects in a range of diseases, including inflammatory disorders, cardiovascular diseases, cancer, neuropathy, as well as retinopathy.

Mitochondrial Mutations in Ethambutol-Induced Optic Neuropathy

Background: Ethambutol-induced optic neuropathy (EON) is a well-recognized ocular complication in patients who take ethambutol as a tuberculosis treatment. The aim of the current study was to investigate the presence of mitochondrial mutations, including OPA1 and Leber's hereditary optic neuropathy (LHON)-mitochondrial DNA (mtDNA), in patients with EON and to determine their effect on clinical features of these patients. Methods: All 47 patients underwent clinical evaluations, including best-corrected visual acuity, fundus examination, and color fundus photography; 37 patients were then followed up over time. Molecular screening methods, including PCR-based sequencing of the OPA1 gene and LHON-mtDNA mutations, together with targeted exome sequencing, were used to detect mutations. Results: We detected 15 OPA1 mutations in 18 patients and two LHON-mtDNA mutations in four patients, for an overall mutation detection rate of 46.8%. The mean presentation age was significantly younger in the patients with the mitochondrial mutations (27.5 years) than in those without mutations (48 years). Fundus examination revealed a greater prevalence of optic disc hyperemia in the patients with mutations (70.5%) than without mutations (48%). Half of the patients with mutations and 91% of the patients without mutations had improved vision. After adjusting for confounders, the logistic regression revealed that the patients with optic disc pallor on the first visit (p = 0.004) or the patients with the mitochondrial mutations (p < 0.001) had a poorer vision prognosis. Conclusion: Our results indicated that carriers with OPA1 mutations might be more vulnerable for the toxicity of EMB to develop EON.

Active surveillance for adverse events in patients on longer treatment regimens for multidrug-resistant tuberculosis in Viet Nam

OBJECTIVE

Management of multidrug-resistant tuberculosis (MDR-TB) is a significant challenge to the global healthcare system due to the complexity and long duration of the MDR-TB treatment. This study analyzed the safety of patients on longer injectable-based MDR-TB treatment regimens using active pharmacovigilance data.

METHOD

We conducted an observational, prospective study based on active pharmacovigilance within the national TB program. A total of 659 MDR-TB patients were enrolled and followed up at 9 TB- hospitals in 9 provinces of all 3 regions in Vietnam between 2014 and 2016. Patients received a treatment regimen (standardized or individualized) based on their drug susceptibility test result and their treatment history. Baseline and follow-up information was collected at the start and during treatment. Adverse events (AE) were defined and classified as serious adverse events (SAEs) or otherwise. Multivariate Cox regression following the Iterative Bayesian Model Averaging algorithm was performed to identify factors associated with AE occurrence.

RESULTS

Out of 659 patients assessed, 71.3% experienced at least one AE, and 17.5% suffered at least one SAE. The most common AEs were gastrointestinal disorders (38.5%), arthralgia (34.7%), and psychiatric disorders (30.0%). The proportion of patients with nephrotoxicity and hearing loss or vestibular disorders were 7.4% and 15.2%, respectively. 13.1% of patients required modifications or interruption of one or more drugs. In 77.7% of patients, treatment was completed successfully, while 9.3% lost to follow-up, in 3.0% treatment failed, and 7.4% died. Some significant risk factors for nephrotoxicity included diabetes mellitus (HR = 8.46 [1.91-37.42]), renal dysfunction (HR = 8.46 [1.91-37.42]), alcoholism (HR = 13.28 [5.04-34.99]), and a higher average daily dose of injectable drugs (HR = 1.28 [1.14-1.43]).

CONCLUSION

While a majority of patients on the longer injectable-based regimens experienced non-serious AEs during MDR-TB treatment, one in six patients experienced at least an SAE. Active TB drug-safety monitoring is useful to understand the safety of MDR-TB treatment and explore the risk factors for toxicity. All-oral, shorter MDR-TB regimens might be able to reduce the inconvenience, discomfort, and toxicity of such regimens and increase adherence and likelihood of successful completion.

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.

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.

Characterisation of macular superficial vessel density alteration in preclinical ethambutol-induced optic neuropathy using optical coherence tomography angiography

AIM

To investigate the changes in macular vessel density (mVD) and its relationship to macular ganglion cell-inner plexiform layer (mGCIPL) thickness in patients receiving ethambutol (EMB) therapy for tuberculosis without recognisable clinical symptoms or signs of EMB-induced optic neuropathy (EON).

METHODS

A total of 23 eyes of 13 patients using EMB therapy for 6 months without EON (preclinical EON) as the EMB group, 40 eyes of 23 healthy individuals as the normal control group and 18 eyes of 10 patients with tuberculosis before receiving EMB therapy as the blank control group were retrospectively analysed. The mean peripapillary retinal nerve fibre layer (pRNFL) and mGCIPL thicknesses and mVD were measured using optical coherence tomography angiography. Patients in the EMB group were compared with individuals in the normal and blank control groups, and changes in macular parameters were evaluated.

RESULTS

Central circle mVD (cCVD) was significantly lower in the EMB group than in both control groups (generalised estimating equation (GEE), p=0.003 and 0.029, respectively). The mGCIPL thickness in all regions and the mean pRNFL thickness were not significantly different between the EMB group and both control groups (GEE, p=1.000 for all). There were no significant differences in mVD, mGCIPL thickness and mean pRNFL thickness between the normal control and blank control groups (p>0.05). In the generalised linear model analyses, the minimum and inferonasal mGCIPL thicknesses were positively correlated with cCVD in the EMB group (β=1.285, p=0.003 and β=0.770, p=0.024, respectively).

CONCLUSIONS

cCVD decreased with no changes in mGCIPL and mean pRNFL thicknesses in patients with preclinical EON. The minimum and inferonasal mGCIPL thicknesses were positively correlated with cCVD. cCVD might be an early indicator for monitoring early-stage EMB toxicity.

Optimizing ethambutol dosing among HIV/tuberculosis co-infected patients: a population pharmacokinetic modelling and simulation study

BACKGROUND

Reduced ethambutol serum concentrations are commonly observed among TB patients co-infected with HIV and may lead to treatment failure.

OBJECTIVES

To perform a population pharmacokinetic study of ethambutol in HIV/TB patients, and to evaluate an intensified ethambutol weight-based dosing strategy to support pharmacokinetic target attainment.

METHODS

We conducted a prospective study of ethambutol pharmacokinetics among HIV/TB patients administered first-line TB treatment in Botswana, with study visits before and after initiation of ART. Clinical and disease status markers, including HIV-associated systemic immune activation and gut dysfunction biomarkers, were evaluated as covariates of ethambutol pharmacokinetic parameters in non-linear mixed effects analysis. Monte Carlo simulations were performed to compare pharmacokinetic target attainment under standard and intensified weight-based ethambutol dosing strategies.

RESULTS

We studied 40 HIV/TB patients prior to initiation of ART, of whom 24 returned for a second visit a median of 33 days following ART initiation. Ethambutol serum concentrations were best explained by a two-compartment model with first-order elimination, with a significant improvement in oral bioavailability following ART initiation. In Monte Carlo simulations, a supplementary ethambutol dose of 400 mg daily led to >2-fold improvements in pharmacokinetic target attainment probabilities in lung tissue, both before and after ART initiation.

CONCLUSIONS

Low serum ethambutol concentrations were commonly observed among HIV/TB patients in Botswana, and the oral bioavailability of ethambutol increased following ART initiation. Supplementary ethambutol dosing among HIV/TB patients may provide a strategy to optimize anti-TB treatment regimens in this high-risk population.

The Impact of Concurrent Antiretroviral Therapy and MDR-TB Treatment on Adverse Events

BACKGROUND

South Africa has among the highest incidence of multidrug-resistant tuberculosis (MDR-TB) and more than 70% of patients are HIV co-infected. MDR-TB treatment is associated with frequent adverse events (AEs). Although guidelines recommend concurrent treatment of MDR-TB and HIV, safety data on concurrent therapy are limited.

METHODS

We conducted a prospective observational study of MDR-TB patients with and without HIV-coinfection in South Africa between 2011 and 2015. Participants received standardized MDR-TB and HIV regimens. Participants were followed monthly for the duration of MDR-TB therapy and screened for clinical and laboratory AEs. Audiometry was performed monthly during the intensive phase; color discrimination testing was performed every 2 months.

RESULTS

We enrolled 150 HIV-infected and 56 HIV-uninfected participants. Nearly all experienced at least one clinical (93%) or laboratory (96%) AE. The most common clinical AEs were peripheral neuropathy (50%) and difficulty sleeping (48%); the most common laboratory AEs were hypokalemia (47%) and decreased creatinine clearance (46%). Among 19 clinical and lab AEs examined, there were no differences by HIV status, except for diarrhea (27% HIV-infected vs. 13% HIV-uninfected, P = 0.03). Hearing loss was experienced by 72% of participants (8% severe loss). Fourteen percent experienced color discrimination loss (4% severe loss). There were no differences in frequency or severity of hearing or vision loss by HIV status.

CONCLUSIONS

AEs were common, but not more frequent or severe among MDR-TB/HIV co-infected participants receiving concurrent antiretroviral therapy. Given the favorable treatment outcomes associated with concurrent treatment, antiretroviral therapy initiation should not be delayed in MDR-TB patients with HIV-coinfection.

[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.

Early discontinuation of ethambutol in pulmonary tuberculosis treatment based on results of the GenoType MTBDRplus assay: A prospective, multicenter, non-inferiority randomized trial in South Korea

No studies have investigated whether discontinuation of ethambutol (EMB) based on the susceptibility to isoniazid and rifampin as determined by the GenoType MTBDRplus assay would be appropriate. We aimed to determine the feasibility of discontinuing EMB before the end of intensive phase treatment based on the result of MTBDRplus assay in patients with pulmonary tuberculosis (PTB). This prospective, multicenter non-inferiority randomized trial was conducted at 12 referral centers in South Korea in drug-susceptible PTB patients who initiated the standard four-drug regimen for PTB. Based on the results of the assay, EMB was discontinued in the MTBDRplus group after the confirmation that M. tuberculosis isolate was susceptible to isoniazid and rifampin. The timepoint for EMB discontinuation in the Guideline group was determined using the results of the phenotypic drug susceptibility test based on the Korean National TB Guidelines. The primary outcome was treatment success. Secondary outcomes included the 1-year rates of recurrence and adverse events. Of 600 randomized patients, the treatment outcome analysis was performed for 493 patients (MTBDRplus group, 244; Guideline group, 249). Treatment success rates were 93.9% (229/224) in the MTBDRplus group and 93.6% (233/249) in the Guideline group and did not differ between groups; relative risk 1.00 (95% CI 0.95-1.06). The 1-year recurrence rate between the two groups (0.9% vs. 0.5%, respectively) and differences in adverse drug reactions did not differ between groups. In conclusion, early discontinuation of EMB based on the results of the MTBDRplus assay did not affect the treatment outcomes in PTB.

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.

Bilateral primary optic neuropathy as the presenting manifestation of tuberculosis in an immunocompetent patient

Vision impairment is one of the devastating complications of central nervous system tuberculosis (CNS TB). Optic atrophy is a sequelae of various forms of CNS TB which, ultimately, is responsible for vision impairment. It is usually the secondary optic atrophy which occurs in CNS TB. In this case report, we present the story of an immunocompetent woman presenting as bilateral visual loss. She was found to have primary optic atrophy. Neuroimaging revealed features of chronic meningitis. Polymerase chain reaction test for Mycobacterium tuberculosis was positive in cerebrospinal fluid. Although secondary optic atrophy is common in the CNS TB, as a complication of meningitis, primary optic atrophy per se is infrequently reported.

Longitudinal evaluation of visual function and structure for detection of subclinical Ethambutol-induced optic neuropathy

Purpose

To longitudinally evaluate the visual function and structure of patients taking ethambutol by various modalities and identify useful tests for detection of subclinical ethambutol-induced optic toxicity.

Methods

This retrospective study enrolled 84 patients with newly diagnosed tuberculosis treated with ethambutol. Best-corrected visual acuity (BCVA), color vision, contrast sensitivity, fundus and retinal nerve fiber layer (RNFL) photography, automated visual field (VF) test, and optical coherence tomography (OCT) were performed: prior to starting; every month during administration, and 1 month after stoppage. We longitudinally compared visual function and structure with the baseline and identified the occurrence of subclinical toxicity.

Results

BCVA, color vision, and contrast sensitivity showed no change from the baseline. Mean temporal RNFL thickness was significantly increased at 6 months (p = 0.014). Subclinical toxicity was found in 22 eyes of 14 patients (i.e., 13% of 168 eyes), in the forms of VFI decrease (VF index, 9 eyes of 6 patients), quadrant RNFL thickness increase (5 eyes of 4 patients), and VF pattern defect (12 eyes of 6 patients). 73% of the patients showed recovery to the baseline at 1 month post-stoppage. The risk factors for occurrence of subclinical toxicity were age, cumulative dose, and medication duration.

Conclusion

Mean temporal RNFL thickness increased after administration. The VFI, quadrant RNFL thickness, and VF pattern defect could prove useful in assessment of subclinical toxicity. Medication duration was shown to be a strong risk factor for occurrence of subclinical toxicity.

Patterns of Ethambutol Ocular Toxicity in Extended Use Therapy

We report the clinical and perimetric findings of three patients with ethambutol toxicity with an extended use regimen. In this observational case series, we extracted data from case records that included age, sex, complaints, details of the current disease, anti-tubercular therapy, ocular findings, and perimetric findings. We identified three patients, two female and one male with ages ranging from 16 to 65 years (mean: 37 years). The perimetric patterns we observed were incomplete homonymous hemianopia in two patients and bitemporal hemianopia in one. Incomplete hemianopia was the predominant perimetric finding, suggesting that the likely lesions were chiasmal or post-chiasmal rather than pre-chiasmal.

The use of optical coherence tomography for the detection of ocular toxicity by ethambutol

Objectives

To evaluate, through (OCT), alterations in retinal thickness, secondary to use of ethambutol in the treatment of patients with tuberculosis. In addition to studying the use of simpler semiological tools, such as Amsler and Ishihara, in the screening of these cases.

Methods

Thirty patients with ethambutol were recruited from the reference service of tuberculosis treatment at the Federal University of Espírito Santo from May 2015 to July 2016. After clinical history, the following parameters were analyzed; best corrected visual acuity, biomicroscopy, tonometry, photomotor reflex testing, Ishihara test, Amsler’s grid test, color digital retinography and optical coherence tomography with CIRRUS HD-OCT (Humphrey-Zeiss) every 2 months during treatment with ethambutol. They were divided into two groups according to the treatment: (1) standard group, two months of ethambutol; (2) extended group, nine to twelve months of ethambutol.

Results

There was a significant reduction in OCT thickness between the pre and post treatment times in ten eyes of the extended group, mean reduction of 7,8 microns and in seven eyes of the standard group, with an average of 5.57 microns. During the study, a significant reduction of retinal thickness was observed in both groups at two months of treatment, and the delta percentage was higher in those patients who presented reduction of visual acuity and / or change in the Ishihara test.

Conclusion

There was a significant reduction in the thickness of the nerve fiber layer by OCT in the patients studied, being more pronounced in those submitted to the extended treatment regimen. This reduction was observed two months after the start of therapy, and was more significant in the cases that presented changes in the Ishihara test.

Toxicity associated with tuberculosis chemotherapy in the REMoxTB study

BACKGROUND

The incidence and severity of tuberculosis chemotherapy toxicity is poorly characterised. We used data available from patients in the REMoxTB trial to provide an assessment of the risks associated with the standard regimen and two experimental regimens containing moxifloxacin.

METHODS

All grade 3 & 4 adverse events (AEs) and their relationship to treatment for patients who had taken at least one dose of therapy in the REMoxTB clinical trial were recorded. Univariable logistic regression was used to test the relationship of baseline characteristics to the incidence of grade 3 & 4 AEs and significant characteristics (p < 0.10) were incorporated into a multivariable model. The timing of AEs during therapy was analysed in standard therapy and the experimental arms. Logistic regression was used to investigate the relationship between AEs (total and related-only) and microbiological cure on treatment.

RESULTS

In the standard therapy arm 57 (8.9%) of 639 patients experienced ≥1 related AEs with 80 of the total 113 related events (70.8%) occurring in the intensive phase of treatment. Both four-month experimental arms ("isoniazid arm" with moxifloxacin substituted for ethambutol & "ethambutol arm" with moxifloxacin substituted for isoniazid) had a lower total of related grade 3 & 4 AEs than standard therapy (63 & 65 vs 113 AEs). Female gender (adjOR 1.97, 95% CI 0.91-1.83) and HIV-positive status (adjOR 3.33, 95% CI 1.55-7.14) were significantly associated with experiencing ≥1 related AE (p < 0.05) on standard therapy. The most common adverse events on standard therapy related to hepatobiliary, musculoskeletal and metabolic disorders. Patients who experienced ≥1 related AE were more likely to fail treatment or relapse (adjOR 3.11, 95% CI 1.59-6.10, p < 0.001).

CONCLUSIONS

Most AEs considered related to standard therapy occurred in the intensive phase of treatment with female patients and HIV-positive patients demonstrating a significantly higher risk of AEs during treatment. Almost a tenth of standard therapy patients had a significant side effect, whereas both experimental arms recorded a lower incidence of toxicity. That patients with one or more AE are more likely to fail treatment suggests that treatment outcomes could be improved by identifying such patients through targeted monitoring.

Diagnostic value of ganglion cell-inner plexiform layer for early detection of ethambutol-induced optic neuropathy

AIM

To evaluate the diagnostic value of macular ganglion cell-inner plexiform layer (mGCIPL) thickness versus peripapillary retinal nerve fibre layer (pRNFL) thickness for the early detection of ethambutol-induced optic neuropathy (EON).

METHODS

Twenty-eight eyes of 15 patients in the EON group and 100 eyes of 53 healthy subjects in the control group were included. All patients with EON demonstrated the onset of visual symptoms within 3 weeks. Diagnostic power for pRNFL and mGCIPL thicknesses measured by Cirrus spectral-domain optical coherence tomography was assessed by area under the receiver operating characteristic (AUROC) curves and sensitivity.

RESULTS

All of the mGCIPL thickness measurements were thinner in the EON group than in the control group in early EON (p<0.001). All of pRNFL thicknesses except inferior RNFL showed AUROC curves above 0.5, and all of the mGCIPL thicknesses showed AUROC curves above 0.5. The AUROC of the average mGCIPL (0.812) thickness was significantly greater than that of the average pRNFL (0.507) thickness (p<0.001). Of all the mGCIPL-related parameters considered, the minimum thickness showed the greatest AUROC value (0.863). The average mGCIPL thickness showed a weak correlation with visual field pattern standard deviations (r²=0.158, p<0.001).

CONCLUSIONS

In challenging cases of EON, the mGCIPL thickness has better diagnostic performance in detecting early-onset EON as compared with using pRNFL thickness. Among the early detection ability of mGCIPL thickness, minimum GCIPL thickness has high diagnostic ability.

Bacterial risk factors for treatment failure and relapse among patients with isoniazid resistant tuberculosis

Background

Drug resistant tuberculosis (TB) is increasing in prevalence worldwide. Treatment failure and relapse is known to be high for patients with isoniazid resistant TB treated with standard first line regimens. However, risk factors for unfavourable outcomes and the optimal treatment regimen for isoniazid resistant TB are unknown. This cohort study was conducted when Vietnam used the eight month first line treatment regimen and examined risk factors for failure/relapse among patients with isoniazid resistant TB.

Methods

Between December 2008 and June 2011 2090 consecutive HIV-negative adults (≥18 years of age) with new smear positive pulmonary TB presenting at participating district TB units in Ho Chi Minh City were recruited. Participants with isoniazid resistant TB identified by Microscopic Observation Drug Susceptibility (MODS) had extended follow-up for 2 years with mycobacterial culture to test for relapse. MGIT drug susceptibility testing confirmed 239 participants with isoniazid resistant, rifampicin susceptible TB. Bacterial and demographic factors were analysed for association with treatment failure and relapse.

Results

Using only routine programmatic sputum smear microscopy for assessment, (months 2, 5 and 8) 30/239 (12.6%) had an unfavourable outcome by WHO criteria. Thirty-nine patients were additionally detected with unfavourable outcomes during 2 year follow up, giving a total of 69/239 (28.9%) of isoniazid (INH) resistant cases with unfavourable outcome by 2 years of follow-up. Beijing lineage was the only factor significantly associated with unfavourable outcome among INH-resistant TB cases during 2 years of follow-up. (adjusted OR = 3.16 [1.54–6.47], P = 0.002).

Conclusion

One third of isoniazid resistant TB cases suffered failure/relapse within 2 years under the old eight month regimen. Over half of these cases were not identified by standard WHO recommended treatment monitoring. Intensified research on early identification and optimal regimens for isoniazid resistant TB is needed. Infection with Beijing genotype of TB is a significant risk factor for bacterial persistence on treatment resulting in failure/relapse within 2 years. The underlying mechanism of increased tolerance for standard drug regimens in Beijing genotype strains remains unknown.

Re-Treatment With Ethambutol After Toxic Optic Neuropathy

There are no data in the literature regarding the safety of re-treatment with ethambutol for recurrent mycobacterial infection after prior ethambutol-induced optic neuropathy. We describe a patient who developed optic neuropathy attributed to ethambutol, recovered fully after drug withdrawal, and tolerated a 14-month long re-treatment 10 years later without developing recurrent optic neuropathy.

Vision loss in tuberculous meningitis

Vision loss is a disabling complication of tuberculous meningitis. Approximately, 15% of survivors are either completely or partially blind. All structures of the visual pathway may be affected in tuberculous meningitis. Optic nerve and optic chiasma are most frequently and dominantly affected. Thick-gelatinous exudates lying over the base of brain, are the pathological hallmark of tuberculous meningitis and are responsible for almost all of its major complications, including vision loss. Strangulation of optic nerves and optic chiasma by the exudates, compression over optic chiasma by the dilated third ventricle, raised intracranial pressure, endarteritis, shunt failure, bacterial invasion of optic nerves and drug-induced optic nerve damage are important reasons that are considered responsible for vision loss. Prompt antituberculosis treatment is the best management option available. Immunomodulatory drugs and cerebrospinal fluid diversion procedures are of limited help. Early recognition and treatment of tuberculous meningitis is the only way forward to tackle this problem.

Official American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America Clinical Practice Guidelines: Treatment of Drug-Susceptible Tuberculosis

The American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America jointly sponsored the development of this guideline for the treatment of drug-susceptible tuberculosis, which is also endorsed by the European Respiratory Society and the US National Tuberculosis Controllers Association. Representatives from the American Academy of Pediatrics, the Canadian Thoracic Society, the International Union Against Tuberculosis and Lung Disease, and the World Health Organization also participated in the development of the guideline. This guideline provides recommendations on the clinical and public health management of tuberculosis in children and adults in settings in which mycobacterial cultures, molecular and phenotypic drug susceptibility tests, and radiographic studies, among other diagnostic tools, are available on a routine basis. For all recommendations, literature reviews were performed, followed by discussion by an expert committee according to the Grading of Recommendations, Assessment, Development and Evaluation methodology. Given the public health implications of prompt diagnosis and effective management of tuberculosis, empiric multidrug treatment is initiated in almost all situations in which active tuberculosis is suspected. Additional characteristics such as presence of comorbidities, severity of disease, and response to treatment influence management decisions. Specific recommendations on the use of case management strategies (including directly observed therapy), regimen and dosing selection in adults and children (daily vs intermittent), treatment of tuberculosis in the presence of HIV infection (duration of tuberculosis treatment and timing of initiation of antiretroviral therapy), as well as treatment of extrapulmonary disease (central nervous system, pericardial among other sites) are provided. The development of more potent and better-tolerated drug regimens, optimization of drug exposure for the component drugs, optimal management of tuberculosis in special populations, identification of accurate biomarkers of treatment effect, and the assessment of new strategies for implementing regimens in the field remain key priority areas for research. See the full-text online version of the document for detailed discussion of the management of tuberculosis and recommendations for practice.

Effect of memantine: A NMDA receptor blocker, on ethambutol-induced retinal injury

Ethambutol (ETM)-induced retinal injury is associated with a deterioration in visual function caused by a mechanism similar to many other retinal injuries; i.e. glutamate-induced N-methyl-d-aspartate (NMDA) receptor hyperexitability. Therefore, the current study was carried out to investigate the effect of memantine (MEM), NMDA receptor blocker, on ETM-induced retinal injury. A total of 36 rats were divided equally into: group I, control, group II (ETM administration, 100mg/kg/d, orally for 4 weeks) and group III (administration of ETM+MEM, 100 and 5mg/kg/d, respectively, orally for 4 weeks). Specimens of the retina were prepared for histological study by haematoxylin, eosin (H&E) as well as for immunohistochemical study by Bcl-2, cleaved caspase-3 and glial fibrillary acidic protein (GFAP). In the ETM group, the neural retina became significantly thinner (p<0.05) and the ganglion cell layer (GCL) was the main layer affected in the form of a significant decrease (p<0.001) in its cellularity, along with an obvious increase in Bcl-2 and GFAP expression as well as caspase-3 and oxidative stress markers level compared with other groups. On the other hand, on combining MEM with ETM, the retinal thickness, NFL appearance and GCL cellularity returned to amounts nearly similar to the control group coupled with a significant decrease (p<0.05) in the detected caspase-3, Bcl-2 levels and minimal GFAP expression. Therefore, memantine could be an effective neuroprotective agent in ETM-induced retinal injury by a mechanism that may involve correction of the pro/anti-apoptotic pathways and normalization of the oxidative and Müller cell stress responses.

Moxifloxacin: An Alternative to Ethambutol for the Treatment of Presumed Ocular Tuberculosis

OBJECTIVE

To present moxifloxacin as an alternative treatment option to ethambutol in an anti-tubercular therapy (ATT) regime in patients with presumed ocular tuberculosis (TB).

METHODS

We identified all cases in our hospital referred for treatment of presumed ocular TB between 2009 and 2013. Age, gender, ophthalmic examination, blood tests, treatment regimens, adverse drug reactions, and outcomes were collected and analyzed for the patients who had moxifloxacin as part of their ATT.

RESULTS

Forty-three cases of presumed ocular TB were treated with moxifloxacin as a part of ATT. Mean age was 44.18 ± 12.47 years; 62.8% were male. A response to treatment, with no evidence of disease recurrence, was seen in 72.1% of cases. Shortened ATT duration was associated with increased risk of treatment failure (p = 0.02, 95% CI: -0.77 to -0.00).

CONCLUSIONS

Moxifloxacin can be considered as a safe and effective alternative to ethambutol for the treatment of presumed ocular TB.

Incidence and prognostic factor of ethambutol-related optic neuropathy: 10-year experience in southern Taiwan

To investigate the incidence and prognostic factors of ethambutol-related optic neuropathy (EON) in one medical center of southern Taiwan, a retrospective chart review study with 4803 newly diagnosed tuberculosis cases from January 2002 to July 2011 at one medical center hospital in southern Taiwan were reviewed. Of these patients, 1004 had ophthalmic records. Sixty-two cases (1.29%) experienced visual impairment and were diagnosed as EON with mean visual acuity of 0.86 ± 0.69 by logMAR. Sixteen of the 62 patients had a follow-up time > 6 months. Of these, eight patients (50%) showed visual improvement (an increase in visual acuity of ≥ 2 Snellen lines) after ethambutol was discontinued. Another eight patients (50%) showed no visual improvement. We analyzed multiple factors between the patients with and without visual improvement by logistic regression, including body weight, daily dose of ethambutol, duration of ethambutol use, cumulative dose of ethambutol, renal function, underlying disease of diabetes mellitus, hypertension, and initial visual acuity showed no statistically significant difference. In conclusion, the incidence of EON was 1.29%. Half of the patients showed visual improvement after discontinuation of ethambutol, and no obvious prognostic factors were found to facilitate the vision recovery. Ethambutol should be discontinued as soon as EON is suspected.

Inflammatory optic neuropathies

PURPOSE OF REVIEW

The aim of this review is to highlight the clinical presentation of a variety of inflammatory optic neuropathies through a case-based format. While emphasis will be placed on optic neuritis, which represents the most common acquired inflammatory optic nerve injury, the cardinal clinical features of other demyelinating forms of optic neuropathy and potential mimics for typical optic neuritis will be discussed.

RECENT FINDINGS

Novel developments in the diagnostic evaluation, clinical associations, and treatment options for several inflammatory optic neuropathies will be described. Key points will emphasize clinical pearls and potential pitfalls that may thwart early diagnosis of underlying demyelinating, infectious, and inflammatory diseases presenting with optic nerve involvement.

SUMMARY

This review will aid the clinician in identifying potential red flags that should prompt consideration for causes of inflammatory optic nerve injury linked to neurologic and systemic disorders, and help guide safe and effective management for these conditions.