Problem:

Sunlight doesn't penetrate beyond a couple of hundred feet from the surface of the ocean. Species that exist at greater depth probably live in a state of perpetual night; yet from a quick google image search (i agree it isn't a very authoritative source) for deep ocean species I see that plenty of these have eyes.

Required:

Question 1: Are the sight organs in deep oceans species merely a remnant from an earlier era?

Question 2: If they are a remnant, has evolution/mutation modified these organs over time?

Regardless of whether the organs of sight are vestigial organs for deep ocean species,

Question: how do the eyeballs withstand the extreme pressure of water in the deeps?

Please give some suggestion on this.