Dry eye syndrome is a multifactorial pathology of the ocular surface. Epidemiological studies report a prevalence of 15% in adults aged between 50 and 95. Depending on the severity of the disease, different treatment strategies may be proposed. The use of autologous serum eye drops (AS) represents an interesting therapeutic alternative for the most severe forms of the disease, due to the serum's composition, which is similar to that of tears. The mechanism of action of AS is still controversial, but is probably multifactorial and seems to be based on growth factors, vitamin factors and anti-inflammatory factors. The clinical response of patients could be dependent on the protein composition of the eye drops. The investigators are aiming to highlight a difference in serum protein composition that could explain the differences in clinical response between patients treated with autologous serum eye drops and to identify the proteins that would be involved in a clinical response or non-response.