Eye contact
Eye contact is one of the important parts of communication, especially in sign language. While a custom of eye contact varies across cultures, eye contact among native signers is a natural part of their communication.
Eyes among signers communicate in many ways. Eye movement includes some certain conventional pause, eye shift, intensity of eye contact, and length of time. In conversation with another signer, maintaining eye contact keeps the listener's attention. Looking away (along with a certain manual gesture) indicates a pause or thinking thus holding the listener's attention.
Etiquettes
For most people, gazing may be uncomfortable when not conversing. When eye contact is prolonged when not conversing, their eye contact may break (eg. look away).
Completely opaque sunglasses, in some inappropriate cases, can be regarded as unpolite, uncomfortable or offending for some, if not most, signers. It lacks eye communication and it may indicate a lack of respect. However, wearing sunglasses is commonly acceptable under such circumstances as beaches and harsh sunlight to the sensitive eyes.
Eye contact that is repeatedly broken, interrupted or distracted is usually annoying and may be considered as rude.