The Effect of Head Position on the Optik Nerve Sheath Diameter in Patients During Thyroid Surgery

Inclusion Criteria: * Patients aged between 18 and 65, with an ASA score between 1 and 2 according to the American Society of Anesthesiologists (ASA) physical status classification system * whose surgery duration was expected to be less than 4 hours were included in our study. Exclusion Criteria: * liver failure * kidney failure * intracranial masses * history of hydrocephalus, * migraine * chronic hypoxemia or hypercarbic lung disease * additional heart disease * hemodynamic insufficiency * neurological and psychiatric diseases, * glaucoma * patients in whom ocular USG could not provide adequate images * patients with pathological problems involving the eyelid and its surrounding area * patients with diseases such as periorbital cellulitis * patients with preoperative headache complaints * patients with known diseases that could cause increased intracranial pressure * patients who refused to participate in the study were excluded from the study.