A 52-year-old man with a 6-month history of chronic bilateral conjunctival redness, mild foreign body sensation, and stringy mucoid discharge presents to the ophthalmology clinic. He denies photophobia or pain. On examination, he has mild papillary reaction on the upper tarsal conjunctiva, no follicles, and no lymphadenopathy. Schirmer test is 8 mm at 5 minutes. What is the most likely diagnosis?