Common synonyms include:
• lentes (for “glasses,” especially in Mexico and Central America)
• anteojos (widespread in South America)
• espejuelos (colloquial in parts of Mexico)
Choose the term most familiar in your region.
Yes. Both use the impersonal se construction:
• Se me cayó un lente… implies “one lens fell off (and I lost it).”
• Se me perdió un lente… means “a lens got lost on me,” focusing on the fact that it ended up missing.
Either conveys that you no longer have that piece.