Oculus

 The children found it by the brackish crick, washed up where fiddler-crabs burrowed on the mudflats. It looked like something riddled. Rutted. They showed it to their friends. An arrowhead? An ancient coin? A spoilt marble, some said; others, an amulet or evil eye. It had a little hollow, a bowled depression with a translucent center, smooth as riverglass. Look down the prism at its heart, and it would bend the surrounding atmosphere as if the whole thing drank the ambient colors swimming over stranded clouds.
Giddy, the children peered into the oculus. A residual halo glowed above the divot in its middle, depending on your angle. Everything racing away from its ingots, made luminous in its liminal ambit. But its material had a craggy texture around the socket—grayish, lumpy, calciferous. Some mistook it for a geode. However, if you pressed your face against it and peered through the lens, you’d stare into a pockmarked moonscape, beholding indistinguishable phantoms nightwalking through a fog-rapt district, hand-in-hand like clockwork. You’d notice a blurry nematode lickerishly flickering like analphabetic ciphers. You’d witness laggard animalcules in lockstep whose see-through innards shined, captured in a bluish protoplasm. They’d squirm and spasm, splurt and waggle.
The children’s father told them that these figures were merely the throbbing of their own blood vessels: negatives of corpuscles, outlines cast by tiny particles within the vitreous humor. Those strange floating creatures, which seem like tadpoles or prokaryotes, are nothing except places where the light’s been intercepted on its way into your optic nerve. You’re merely gazing at the back of your own heads.
At this, the children wrestled, nudged, and pushed each other off it for another look. First one then the other scrutinized those dormant sparks and darkling ornaments until they felt a sharp elbow in their gut. Nascent squiggles of ideas vaunted crosswise in doubtful parallax, glitching. A troubled axis rushed open between inside and out.
Soon, the children learned they could press down on the lidded corner of their own eyeballs to witness an obscure spiderwork of veins. They understood themselves to be a crush of shadows conscious that they’re only shadows. Lost in such looking, they squinted, longer and harder, until the awkward outlines of shapes went riven and raving inside them. They exerted such pressure that for hours afterward each pebble was a star dissolving, each crevice a vortex into a peopled space not really there.