Loss of colour vision discrimination may accompany retinal damage following light exposure. This is usually a differential loss of sensitivity to blue light. A test particularly suitable for distinguishing colour vision losses, and blue losses in particular, is the Famsworth D15 test. The test consists of 15 movable colour samples placed in a box with a fixed reference sample. The patient's arrangement of the colour is plotted on a circular diagram.
Major errors give rise to lines which cross the circle.
In general terms, the skin can tolerate a great deal more exposure to laser beam energy than the eye can tolerate. This may not be followed by erythema. If the irradiance is extremely high, pigmentation, ulceration, and scarring of the skin and damage of underlying organs may occur. Latent or cumulative effects of laser radiation have not been found prevalent. However, some limited research has suggested that under special conditions, small regions of human tissue may be sensitised by repeating local exposures with the result that the exposure level for minimal reaction is changed and the reactions in the tissues are more severe for such low level exposure.