I believe theses eels are adapting to a parasitic infection of a species of eel-like larvae. This parasitic species dominates the left eye, most of the leftern hemisphere of brain and large portions of the cervical nervous system. The host can "see" these larvae in the left eye as they grow, hence the adaptive skin growth influenced by the parasite to reduce hosts response to them.
These larvae are hatched from eggs, found inside certain species of crustaceans and other shellfish. Once consumed by select host species they burrow into their host and influence them similarly to Snubnossed eels(Simenchelys parasitica) and other aquatic parasites like certain nematodes.
These specific species of eels eyes are what is adaptating to the dark habitat they are found in. The shape, size, positioning and overall anatomy of the eyes are evolving/devolving, or rather adapting, to the lack of light.
Additionally these eel species are "greedy" not just due to environmental factor for prey but also due to being a host for parasites.
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