Tanzanian Endemic Optic Neuropathy (TEON): A pilot case control study of genetic, nutritional and environmental determinants

Brief Lay background

Tanzanian Endemic Optic Neuropathy (TEON) causes irreversible vision loss in young people, resulting in significant disability and huge educational and economic implications. The condition, which is centred around the city of Dar es Salaam in East Africa, affects up to 40,000 people under the age of 40.

Despite being a relatively common disease, the cause of TEON is still frustratingly unclear. TEON is caused by damage to the optic nerve which connects the eye to the brain. This nerve needs a lot of energy to work properly. Therefore, optic nerve cells are very susceptible to damage to mitochondria, the portion of a cell that produces energy.

TEON is clinically similar to the mitochondrial disease Leber’s Hereditary Optic Neuropathy, yet previous work has failed to identify the common mutations seen in Europeans within the African population. Based on recent research in other fields we think that TEON is the result of damage to mitochondria via a number of lifestyle (diet) and environmental (low sunlight exposure) factors in individuals with a genetic susceptibility.

Rapid urbanisation in East Africa has led to reduced skin ultraviolet light (sunlight) exposure together with a carbohydrate-based diet low in protein and micronutrients. An unpublished pilot study has shown low vitamin D status, which is a proxy for reduced sunlight exposure, in patients with TEON. Vitamin D influences many cellular processes, including mitochondrial functioning. In addition, exposure to indoor cooking fumes have been shown to be associated with TEON.

What problem/knowledge gap does it help address

Researchers are working on the hypothesis that reduced sunlight exposure, combined with altered dietary habits in a genetically susceptible population leads to mitochondrial dysfunction, and ultimately the development of TEON and irreversible vision loss.

Aim of the research project

The research aims  to understand more about the environmental, lifestyle and genetic causes of TEON.

Key procedures/objectives

1. To further explore how lifestyle (with a focus on diet and sun exposure), genetics and biochemical status are associated with TEON.
2. To investigate TEON in Dar es Salaam and to inform larger scale studies.

Potential impact on people with sight loss

The project will benefit the population of East Africa by establishing the causes of TEON, which could be a large step towards developing an intervention to prevent this neglected condition and irreversible sight loss. This could in turn prevent the significant economic, social, and educational implications associated with the condition.