Blepharitis, or eyelid inflammation, one of the most common problems, is characterized by erythematous eyelids with accumulation of debris along the eyelid margin. Malignant eyelid tumors may be associated with lash loss and erosion of normal eyelid structures.
Quarter Moon, captured by NASA astronauts. Image credit: NASA. You can have a first quarter moon, when the Moon is halfway between a new moon and full moon. A new moon occurs when the Moon is directly in between the Sun and the Earth. From that perspective, the illuminated Moon is facing away from the Earth.
As the Moon orbits Earth, we see lunar phases as the amount of the Moon's sunlit face visible to us varies. At full Moon, we can see the entire illuminated side. At quarter Moon, only half the sunlit side can be seen. At new Moon, the sunlit face points away from us, and the Moon is all but invisible from Earth. The time between successive full Moons is one synodic month. The time taken for the Moon to return to the same position in the sky, relative to the stars, is one sidereal month. Because of Earth's motion around the Sun, the synodic month is about 2 days longer than the sidereal month. A lunar eclipse occurs when the Moon enters Earth's shadow.