The Arcus Deformity is caused by the fact that a small structure beneath the lower eyelid called the Arcus Marginalis is attached to the bone of the eye socket and also attached to the lower eyelid from underneath. This attachment tethers or holds the eyelid close to the bone of the eye socket while the rest of the lower eyelid is loose and free to move. The normal fat which is beneath the eyeball pushes out against the lower eyelid which creates a visible bulge on the lower eyelid. You can see this by closing one eye and gently pressing on the closed eye. With your other eye you will see the bulging of the fat against the closed lower eyelid on the other side.

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