Letters 94.20

He says: “There is no reason why you should at once expose your weak vision to a dangerous glare; begin with darkness, and then go into half-lights, and finally be more bold, accustoming yourself gradually to the bright light of day. There is no reason why you should study immediately after eating; there is no reason why you should impose hard tasks upon your eyes when they are swollen and inflamed; avoid winds and strong blasts of cold air that blow into your face,”—and other suggestions of the same sort, which are just as valuable as drugs themselves. The physician’s art supplements remedies by advice.

Seneca, Letters to Lucilius 94.20, translated by Richard Mott Gummere