4.3. Conjunctival Impression Cytology

Conjunctival cells were collected using impression cytology as previously described [6]. This method consists of gently applying a polyethersulfone filter (Supor^®, Gelman, Pall Science, Ann Arbor, MI, USA) to the superior conjunctiva to collect the superficial conjunctival cells. This minimally invasive sample was taken bilaterally whenever possible for each patient after instillation of a drop of topical anesthetic (oxybuprocaine, 1.6 mg/0.4 mL, Thea Laboratory, Clermont-Ferrand, France). Conjunctival imprints were placed in a sterile tube and stored at −80°C until analysis.