The thin layer of mucus is needed for making the surface hydrophilic , the layer of water can then spread evenly on the corneal surface. If the mucus layer is uneven, some patches on the cornea have no mucus on the surface. The water layer rolls aside, the surface dries and wrinkles a little. This stretches the nerve endings and causes a sticking pain in the eye. Changes in the structure of the tear film are common.
Eyes are somewhat dry and irritated, now and then there is a sensation of sticking pain.
It is always advisable to use a glas rod to apply ointments and all thicker drops into the eye. Otherwise, if one applies directly from the tube or the dropper, the amount of thick fluid or ointment is too big, the layer will be too thick and vision will be blurred. Place the rod on the mucous membrane of the lower eyelid. Look upward and close the eye. Draw the rod out.