The relationship between ciliary muscle fatigue and the type of artificial light used to illuminate the area of visual work.

The relationship between the degree of eye fatigue resulting from visual work and type of light source used to illuminate the field of work was assessed. The tests were performed using artificial light sources: fluorescent lamps, incandescent lamps, high pressure mercury (vapour) and high pressure sodium (vapour) lamps. The assessment was performed on two groups of 10 women each, of which one included women without, and the other with, refraction errors. On the basis of changes of nearer vision point and dispersing lens tolerance, it was found that sodium light produced the highest visual fatigue in the test women, especially in those with refraction errors.