Suyuti, in his “Medicine of the Prophet” said,
“Anyone who seeks good health must avoid heat and cold in excess, violent winds, smoke and dust, much crying, straining of the eyes in transcribing and too much reading of tiny manuscript. This last should indeed be done but rarely; although if done in small amount it renders the vision keen. A man should also avoid looking at shining objects, at the orb of the sun, and at whatever is pure black or pure white.”