In this short clip, you can see the mantis shrimp using some sort of feathery arm/claw to rub its eyes. Looking at a diagram here, it appears possibly that it's using maxillipeds. Someone with knowledge of crustaceans (the behavior is probably not unique to mantis shrimp) would be appreciated.
Mantis shrimp use their first maxillipeds for grooming (maxilliped=modified appendage), which is specialized for this purpose. Details and a picture of the organ can be found in the link. The second maxilliped is their famous specialized organ for striking or spearing prey with enormous force. More about their raptoral appendage, with links to further references. Mantis shrimp also have very complex eyes, described as "...the most complicated visual system of any animal on Earth". Their eyes can see a range from ultraviolet to infra-red and has specialized regions for observing motion, form, depth, and color. More on Mantis shrimp eyes can be found in Marshall & Oberwinkler (1999).