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 ^ Taurine An amino acid which is essential in retina health. It is synthesized in humans except for premature babies, who may need supplements. Cats display retinal abnormalities when taurine is deficient in their diet.


 ^ TaqMan A rapid fluorophore-based real-time quantitative polymerase chain reaction method.

Li YM, Wang JY, Chen Y, Shao JB, Wang J, Tong Y. [Detection of mtDNA*LHON G11778A mutation by real-time polymerase chain reaction using TaqMan-MGB probe technology] Zhonghua Yan Ke Za Zhi. 2006 Aug;42(8):728-32. PMID 17081446


 ^ Terpene


 ^ Thalamus


 ^ Thyroid optic neuropathy See Dysthyroid optic neuropathy

 ^ Tissue, ~ specificity A group of cells organized into a typical structure based on cell type and relationships among cells and groups of cells. Most diseases are limited to certain tissue types. The reasons for this specificity are sometimes not clear. For example, mitochondria exist in every cell type. Yet mitochondrial based disease is sometimes very tissue specific. A paradox yet to be solved.


Wikipedia cellular differentiation

 ^ Tobacco-alcohol amblyopia Optic neuropathy syndrome associated with heavy use of one or both of these substances. Care must be taken to look for LHON masquerading as Tobacco-alcholol amblyopia.

See Tobacco+alcohol+amblyopia PubMed search

 ^ Tocotrienol A group of Vitamin E substances, working as antioxidants useful in neuronal protection.


 ^ Tonometer


 ^ Toxic Optic Neuropathy Optic nerve disease contributed to by an ingested substance or radiation. Some may wish to include nutritional and metabolic causes in this group. It is highly recommended that those with a family history of optic nerve or retinal disease enquire themselves and with their health professional about possible eye toxicity before being exposed to any drug or substance. Mechanisms of toxicity vary with the substance and the patient.

Medications with demonstrated adverse effects on mitochondria in LHON [* strong evidence]:
Antimicrobials: Erythromycin*, Ethambutol*, Linezolid*, Chloramphenicol*, Aminoglycosides, Tetracyclines. Hyperbaric oxygen; Quaternary ammonium compounds; Ringer’s lactate.

Classes of drugs with potential for adverse mitochondrial effects in LHON:
Antidepressants; Antipsychotics; Barbiturates; Anxiety medications; Anticonvulsants; Cholesterol medications; Inflammatory/analgesic medications; Anti-arrhythmic medications; Beta blockers; Antiviral medications; Chemotherapeutics; Diabetes medications.

Eye Neurotoxins - A sample list.
Tobacco smoke Known to be associated with colour vision defects. LHON gene carriers are more likely to lose vision.
Alcohol (Ethanol) Tobacco-alcohol amblyopia syndrome. LHON gene carriers are more likely to lose vision.
Ultra violet radiation Excessive amounts implicated in adult onset macular degeneration
Methyl Alcohol Acutely toxic
Carbon monoxide Seen in accidental or suicide attempt exposure. Possibly part of the mechanism of tobacco smoke neurotoxicity. Binds to heme groups in blood hemoglobin, metabolic regulatory proteins and the mitochondial electron transport chain.
Toluene Excessive amounts implicated in adult onset macular degeneration
Erythromycin Antibiotic. Can cause mitochondrial dysfunction in LHON carriers.
Ethambutol Anti tuberculosis antibiotic. Can cause mitochondrial dysfunction in LHON carriers.
Chloramphenicol Antibiotic. Can cause mitochondrial dysfunction in LHON carriers.
Linezolid Antibiotic. Can cause mitochondrial dysfunction in LHON carriers.
Isoniazid Anti tuberculosis antibiotic.
Chloroquine Anti malarial and anti rheumatic.
Tetracycline antibiotics Possibly can precipitate Mitochondrial Dysfunction in LHON carriers.
Aminoglycoside antibiotics Possibly can precipitate Mitochondrial Dysfunction in LHON carriers.
Suramin sodium Anti HIV drug. Causes optic neuropathy.
Ziduvodine Anti HIV drug. Causes retinopathy.
Vigabatrin Anti epilepsy drug associated with visual field defects. GABA transaminase inhibitor.
Chlorpropamide Anti diabetes tablet.
Metformin Anti diabetes tablet. Theoretical issue with LHON.
Digitalis Heart antiarhythmic acting as a Na+,K+-ATPase (sodium pump) inhibitor.
Amiodarone Heart antiarhythmic.
Propranolol Heart antiarhythmic/ Beta-blocker/anti high blood pressure drug. Lowers intraocular pressure and may predispose to anterior ischemic optic neuropathy.
Prazosin (Minipress) and Terazosin (Hytrin) Alpha blocker/anti High Blood Pressure/counter prostatism drugs. Low night time blood pressure and may predispose to anterior ischemic optic neuropathy.
Quinineanti malarial
Sildenafil (Viagra) Anti impotence drug. One report of associated anterior ischemic neuropathy.
5-FU Anti cancer drug.
Taxane Anti cancer drug. Can induce glaucomatous optic nerve disease.
Vioform Antibiotic topical and antidiarrheal.
Benzalkonium Chloride Common eye drop preservative and household disinfectant. Potently induces mitochondrial dysfunction and preferentially affects LHON mutant cells.
Hyperbaric oxygen Can precipitate mitochondrial dysfunction in LHON carriers.
Ringer's lactate or Hartmanns solution Can precipitate Mitochondrial Dysfunction in LHON carriers.

Kailenn Tsao, Phil A Aitken, Donald R Johns. Smoking as an aetiological factor in a pedigree with Leber's hereditary optic neuropathy [full text] Br J Ophthalmol 1999;83:577-581 ( May )

The Eye Drop Preservative Benzalkonium Chloride Potently Induces Mitochondrial Dysfunction and Preferentially Affects LHON Mutant Cells. Sandipan Datta; Christophe Baudouin; Francoise Brignole-Baudouin; Alexandre Denoyer; Gino A. Cortopassi. Investigative Ophthalmology & Visual Science April 2017, Vol.58, 2406-2412. doi:10.1167/iovs.16-20903

Toxic medications in Leber's hereditary optic neuropathy. Kogachi K, Ter-Zakarian A, Asanad S, Sadun A, Karanjia R. Mitochondrion. 2019 May;46:270-277. doi: 10.1016/j.mito.2018.07.007. Epub 2018 Aug 4. PMID: 30081212

toxic+optic+neuropathy PubMed search


 ^ Toxocariasis


 ^ Trabeculectomy An operative procedure for glaucoma. It diverts the aqueous humor of the anterior chamber through the trabecular meshwork between the iridocorneal angle and the sinus venosus in order to reduce intraocular pressure.


 ^ TranscriptionTranscription is the first of several steps of DNA based gene expression in which a particular segment of DNA is copied into RNA (especially mRNA) by the enzyme RNA polymerase. Nuclear DNA transcription varies in detail from mitochondrial DNA transcription.


Caterina Garone, Michal Minczuk, Aaron R. D’Souza, Michal Minczuk; Mitochondrial transcription and translation: overview. Essays Biochem 20 July 2018; 62 (3): 309–320. doi:

Shokolenko IN, Alexeyev MF. Mitochondrial transcription in mammalian cells. Front Biosci (Landmark Ed). 2017 Jan 1;22:835-853. doi: 10.2741/4520. PMID: 27814650; PMCID: PMC5653244.

 ^ Transcription factor


 ^ Translation


 ^ Transporter, neurotransmitter


 ^ Transverse myelitis


 ^ Trial, clinical A test of outcomes of an intervention on a sample group of one or more individuals. Trials are done to test treatments for example. The significance of a trial on predicting outcomes on other individuals depends on application and interpretation of statistics.


 ^ Tricarboxylic Acid (Krebs) Cycle


 ^ Tumour Necrosis Factor-alpha A trophic (growth-death) factor which may play a role in optic nerve axonal degeneration.

Wikipedia tumor necrosis factors

Wikipedia tumor necrosis factor alpha

 ^ Tumours, Optic Nerve Some growths which may be considered in the differential diagnosis of optic neuropathy include optic nerve gliomas(the most common), optic nerve sheath meningiomas, craniopharyngiomas, pituitary adenomas, dermoids, retinoblastomas, melanocytomas, malignant melanomas, neurofibromas, bone tumours, vascular aneurysms (of anterior cerebral or internal carotid arteries) and metastatic tumours. See:

CHORUS entries: Optic nerve glioma Optic nerve meningioma Neurofibromatosis

Richard Woodcock, MD. Optic Gliomas. eMedicine Article.

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