The eyelids are fundamental so that the eyeball is protected against external aggressions, but above all they are important to allow an adequate distribution of the tear film on the ocular surface so that it does not dry out and allows a good visual acuity.
A palpebral disease can produce blurred vision. That is, to be able to see clearly the eyelids must be positioned correctly allowing protecting the eyeball and, at the same time, enabling the tear and its components to be distributed appropriately on the surface of the eye.
When an upper eyelid is excessively drooping (what we know as palpebral ptosis ), it will partially or totally impede the vision of the upper half of the visual field. Another illustrative example we can observe in those patients who can not completely blink (what we know as lagophthalmos ), so that their ocular surface is dried causing wounds that cause blurred vision. Finally, in those eyelids with considerable tumors, these can alter the curvature of the cornea and develop an astigmatism that could worsen the patient's visual acuity.
Although each case should be individualized and should be explored by an ophthalmologist specializing in diseases of the eyelids and the lacrimal pathway ( specialist in Oculoplastic Surgery ), effectively the eyelids are essential to ensure that the eyes do not cry excessively. They must have an appropriate tension and position to be able to fulfill their function of distribution of the tear on the ocular surface and to enhance their drainage towards the lacrimal way. A flaccid eyelid or eyelid that is not well positioned over the eye will most likely be a tearful eye.