There are several schools of meditation in which the eyes are closed, the idea being to turn the awareness inward and shield it from sensory distractions. Sometimes this is called pratyahara, withdrawal of the senses. There is even a yogic mudra in which the fingers block the eyes, ears, and nostrils.
But in Zen our direction is to wake up to this world and perceive directly that there is no inside and no outside, that we are not separate from all beings. Zen Master Seung Sahn taught that when we sit everything that we see becomes clear, everything that we hear and smell and taste and touch, every bodily sensation, pleasurable or painful or neutral — all becomes clear. A Buddha is literally someone who is fully awake. Being awake to this world as it actually is naturally gives rise to compassion. So if we sit with our eyes open, our ears open, all our senses open, our minds and our hearts will also open.