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.

Inclusion Criteria:

• Age over 18 years
• Patients with severe dry eye with an Oxford score > 1
• Patients with dry eye syndrome refractory to conventional treatments: tear substitutes, immunosuppressive eye drops or corticosteroids.
• AS-naïve patients followed by an ophthalmologist at Saint-Etienne University Hospital
• Patients affiliated to or entitled under a social security scheme
• Patients who have received informed information about the study

Exclusion Criteria:

• Severe ocular dryness due to a genetic disease
• Patients not under the care of an ophthalmologist at Saint-Etienne University Hospital.
• Patients not eligible for treatment with AS (pregnant women, anaemia, current infection, progressive disease, serological results contraindicating blood sampling).
• Patients under protective measures