The third layer is called the Oily layer. The function of this layer is to prevent the evaporation of tears in the tear film on the cornea which can aid in preventing dry eyes. If one of these layers are not functioning properly, for instance in the case of the oily layer, ceasing to work properly, there is no oily lubrication provided to maintain moisture in the tear film. As a result of this the tears evaporate thereby causing the problem of dry eyes. Also, the eye's immune system can go haywire and compensate for the dryness in the eyes or lack of tear production by overproducing poor quality tears. ADDITIONAL CAUSES OF DRY EYES 1 Some additional causes of dry eyes include smoking, drinking coffee, wearing contact lenses and exposure to certain environmental factors such as heaters and air conditioning. 2 Certain eye diseases and health conditions such as Diabetes, Glaucoma, Asthma, Lupus and a Thyroid condition to name a few. 3 Excessive Close up Work on the Computer: When you are performing excessive close up work on the computer you tend to decrease your rate of blinking.