What do both gulliver's pocket perspective-glass and his spectacles most likely symbolize in the "a voyage to lilliput"section from gulliver's travels?

In the chapter of excerpt Gulliver's Travels which is "A Voyage to Lilliput". Lemuel Gulliver, the main character of a narrative story, a surgeon in London, there are things usually found in his pocket. For him, his pocket perspective-glass and his spectacles mean to gain insight and understanding.