Caterpillars' eyes, as would be expected from what is, after all, an evolved insect, are multi-faceted. The main defect in caterpillar eyesight is the loss of sight in certain of the facets. Caterpillar glasses, which hook onto the antennae and cover the large eyes, work by compensating for the faulty facets, carrying optical information directly to the retina, along microscopic fibre optics, which were actually implanted onto the surface of the eye, but could be removed with the ease of a human's glasses. In extreme cases, corrective surgery could be employed in order to repair or replace damaged facets, but as a rule this was only used as a last resort, and in mild eyesight disorders, glasses would be constructed from a strong, ductile polymer, to feed the facet's signal to the clouded receptor. If the nerve itself had burnt out, not just the facet scratching or becoming otherwise damaged, surgery was less likely to help the sight of the caterpillar, although it was becoming possible to repair damaged nerve endings in optical nerves. It was conceivably possible to replace the rods and cones in the optic nerve, or indeed to replace the entire optic nerve, but only in the way that it is conceivably possible for humans to clone themselves in a laboratory set up in the shed, in other words, possible, but not likely.
Copyright 1999 Ian Rennie, for Remiel Productions.