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The Geometry of Exposure of the Eye to Solar Ultraviolet Light

Lee, Pak Sang; (2004) The Geometry of Exposure of the Eye to Solar Ultraviolet Light. Masters thesis (M.Phil), UCL (University College London). Green open access

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Abstract

The lack of accurate personal ocular dosimetry remains an obstacle to the investigation of a possible association between exposure to solar ultraviolet radiation (UVR) and ocular disorders. UV-B is considered to have the most damaging effect on the eyes and skin and is thought to be an important risk factor in the development of cataract, climatic droplet keratopathy (CDK), pterygium and possibly age-related macular degeneration (AMD). Currently there is insufficient data on the range of ocular exposure in human populations who are considered to be at risk. A personal UV headband was designed to measure solar UV radiation in the range of 280nm-315nm (the UV-B region). This device consisted of two UV sensors connected to a Psion data logger. Twenty outdoor workers in Mongolia were requested to wear the personal UV headband for one day. In the Gambia the personal UV headband was used to measure the ocular UV exposure with the head in different positions in relation to the sun, and when headgear with different sized brims was worn. Consistent with previous findings, the intensity of ambient UV-B was greatest between 11am - 3pm. However, analysis of the Ocular Ambient Exposure Ratios (OAER) data averaged across all subjects revealed that OAER's were higher in the morning at 9:30 and decreased progressively during the day. Seventeen out of twenty volunteers in Mongolia went indoors for lunch break or stayed under shade during midday hours. Of the different types of brimmed hat tested for sun-protection, only wearing a hat with a 12.7 cm brim all round was found to significantly reduce the incident UV from both the front and side of the eye. A baseball cap provided good protection against UVR coming from the front of the eye but it has not provided any protection against UVR coming from the side of the eye. It is possible to measure the ocular exposure to solar UV radiation in a dynamic way through the use of the personal UV headband. The exact time interval and the dosage of solar UV exposure close to the eye can be measured enabling the OAER to be calculated over a range of different environmental circumstances. These methods could be used to validate questionnaires of life-time exposure. Environmental conditions and human behavioural factors played an important role in ocular UV exposure. Individuals may be exposed to dangerous levels of UV-B in the early part of the day and therefore need to take appropriate precautions to reduce UV exposure throughout the entire day.

Type: Thesis (Masters)
Qualification: M.Phil
Title: The Geometry of Exposure of the Eye to Solar Ultraviolet Light
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: This thesis has been digitised by ProQuest.
Keywords: Ultraviolet Light, cataract, AMD, CDK, UV-B, cancer
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/62013
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