Development of an experimental model for ocular toxicity screening in Zebrafish.

BACKGROUND: To investigate the efficacy of a novel experimental model for exploring visual function using a contrast-optomotor response (C-OMR) assay made by applying the contrast sensitivity test to the OMR assay in zebrafish. METHODS: Zebrafish larvae were treated with 0 (control), 5, 10, or 15 µM gentamicin and digoxin for 24 h at four days post-fertilization (dpf). Zebrafish larvae were assessed using the C-OMR assay with graded contrast gray-white stripes at 5 dpf, and the results were expressed as the percentage of larvae that finished swimming for 30 s (n = 20 per each group). The same C-OMR assay was repeated four times using different larvae. RESULTS: The percentage of larvae that finished swimming within 30 s was significantly reduced in larvae treated with 5, 10, and 15 µM gentamicin and 10 and 15 µM digoxin as compared to the Control groups. The C-OMR assay could distinguish that the decrease in visual function was different depending on the concentration of gentamicin and digoxin (5, 10, and 15 µM), whereas the OMR test with one contrast gray-white stripe could not. CONCLUSIONS: The method of analyzing zebrafish OMR using graded contrast gray-white stripes is more sensitive than the OMR assay alone and may be more useful for assessing the drug toxicity and eye-related diseases to improve the understanding of drug-induced ocular side effects in the clinic.

Is Ocular Toxicity Expected in Chloroquine/Hydroxychloroquine Prescription as a Therapeutic or Prophylactic Option in COVID-19?

BACKGROUND: On 11th March 2020, WHO announced novel coronavirus infectious (COVID-19) as a pandemic. New Coronavirus Pneumonia (NCP) that emerge on 31st December 2019 from China and quickly became a Public Health Emergency of International Concern (PHEIC). In the absence of evidence-based proven prophylactic or therapeutic options, chloroquine/hydroxychloroquine (CQ/HCQ) patented as first line choice in COVID- 19 treatment, which raised concerns about drug poisoning, especially ocular toxicity. OBJECTIVE: This study aims to investigate the possibility of ocular toxicity and the need for ophthalmic counseling to prescribing this therapeutic protocol. METHODS: All the articles that were most relevant to the COVID-19 therapeutic or prophylactic options and CQ derivative ocular toxicity, were founded by a literature search and were thoroughly reviewed. RESULTS: Anecdotal recent reports introduce CQ/HCQ as an effective therapeutic or prophylactic choice for COVID-19. Because of the short time prescribe and the insignificant cumulative dose of the drug on the one hand and a higher risk of cross-infection during an ophthalmic examination, on the other hand, an ophthalmologic consult is not recommended except in highrisk patients for retinal toxicity. CONCLUSION: This study recommended ophthalmic evaluation before CQ/HCQ prescription for treatment or prophylaxis of COVID-19 only in preexisting maculopathy.

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

SIGNIFICANCE: Nutritional and toxic optic neuropathies are rare disorders characterized by visual impairment due to optic nerve damage by a toxin, usually with coexisting nutritional deficiencies. Its pathophysiology is still unclear, and multiple mechanisms implicated act synergistically to bring about this condition. The decline in its incidence and its confusing clinical appearance make diagnosing nutritional and toxic optic neuropathies challenging. PURPOSE: This is an observational clinical case report of an atypical clinical case of a nutritional and toxic optic neuropathy with a subacute presentation and papilledema at the time of diagnosis. The patient provided written informed consent for medical information and images to be published. CASE REPORT: A 47-year-old man presented with progressive, painless bilateral decrease in central vision over 15 days. The patient had a long-standing history of alcohol abuse and was a heavy smoker. The examination revealed dyschromatopsia, 20/400 visual acuity on both eyes, and no relative afferent pupillary defect. Funduscopy revealed bilateral papilledema. A visual field test showed generalized depression with centrocecal involvement in the left eye. Laboratory studies evidenced decreased vitamin B12/B1 and red blood cell folate levels, increased acute phase reactants, hypertransaminasemia, and macrocytic anemia. Serologies and methanol in urine were negative. After the discontinuation of tobacco use and alcohol accompanied by vitamin supplementation, our patient's visual field, visual acuity, and papilledema improved remarkably. After 5 months, visual acuity and funduscopy were normal. CONCLUSIONS: Although some hallmark signs were visible in this case, its subacute presentation and the presence of papilledema at diagnosis caused some diagnostic uncertainty. Nutritional and toxic optic neuropathy is a rare and challenging diagnosis because of a lack of biomarkers. Eye care clinicians should consider nutritional and toxic optic neuropathies to prevent severe and irreversible visual damage resulting from underdiagnosis and mismanagement.

Toxic Optic Neuropathy From Quinine Overdose.

A 45-year-old man presented with longstanding poor vision in both eyes. His medical history was significant for a remote overdose of quinine. After the ingestion, he fell into a coma and on awakening was not able to see light out of both eyes. Several days later, his central vision began to gradually recover and continued to improve over the span of several months. Presently, he had 20/20 visual acuity in both eyes with severely constricted peripheral visual fields. There were bilateral iris transillumination defects, and both optic nerves were diffusely pale with attenuated vasculature and inner retinal thinning on ocular coherence tomography. We present a patient with the stereotypical findings and natural history of quinine toxicity, a rare and not widely known cause of toxic optic neuropathy and retinopathy.

Tobacco-Alcohol Toxic Optic Neuropathy.

Purpose. To present the case of a 34-year-old man with sudden bilateral decrease of visual acuity, followed by a complete and fast recovery. Material and methods. We reported a case of an apparently healthy 34-year-old patient with sudden and unpainful decrease of visual acuity, presumed of toxic etiology. The patient was treated at the debut of the symptomatology, thus having a favorable evolution during hospitalization, with the full recovery of his visual acuity, without complications. Conclusions. Tobacco-Alcohol Toxic Optic Neuropathy has an unknown pathophysiological mechanism that allows very good recovery of visual acuity, if treated early.