A prospective, single-blinded, randomized, controlled crossover trial was conducted in patients with severe dry eye syndrome. Topical treatment with autologous serum eye drops (ASED) diluted at 20%, undiluted ASED and conventional preservative-free artificial tears (PFAT) were compared as a treatment for severe dry eye disease. The primary outcome measure was assessment of ocular symptoms using the Ocular Surface Disease Index (OSDI) questionnaire. Secondary outcomes were Schirmer 1 test, best-corrected visual acuity (BVCA), corneal fluorescein and conjunctival lissamine green staining using the Sjögren's International Collaborative Clinical Alliance Ocular Surface Staining (SICCA OSS) score, tear break up time (TBUT), conjunctival injection score (CIS) and Meibomian gland dysfunction (MGD) grading. Additionally, serum and tear cytokine analysis and microbiological cultures were performed.