Question
A 42-year-old welder pre- sents to employee health services complaining of tearing eye pain and photophobia. A photokeratocon- junctivitis is diagnosed. The most likely cause of this condition is
| A. |
Infrared radiation
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| B. |
Visible radiation
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| C. |
Ultraviolet radiation A
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| D. |
Ultraviolet radiation B
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Show Answer
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Correct Answer � D
Explanation
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Answer: d. Ultraviolet radiation B
Ultraviolet radiation covers the spectrum between visible radiation (light) and ionizing radiation (100400 nm). Ultraviolet radiation B ranges from 280 to 315 nm, the range to which the eye is particularly sensitive and where most injuries occur. Acute exposure to UV of less than 315 nm results in photokerato- conjunctivitis, with symptoms appearing 6 to 12 hours after exposure. Pro- longed exposures to UV between 295 and 320 nm can result in cataract formation. Ultraviolet A ranges from 315 to 400 nm. Injuries caused by visible radiation (light), which covers the spectrum between infrared and ultraviolet radiation (400750 nm), affect primarily the retina, which is most sensitive to blue light (eclipse blindness). Infrared light covers the spectrum between visible light and radiofrequency (750 to 3 million nm).
It is given off by any material of a temperature greater than absolute zero. Thermal injury can occur with intense exposure to infrared light of less than 2000 nm and has been associated with cataract formation.
