Optic Nerve Sheath Diameter for Predicting Post-Dural Puncture Headache in Cesarean Section Patients

Inclusion Criteria: * Women aged 18 to 45 years * Singleton pregnancy * Planned cesarean section (elective or emergency due to fetal indications) * Spinal anesthesia planned for the procedure * American Society of Anesthesiologists (ASA) physical status II-III * Normal coagulation parameters (INR less than 1.5, platelet count greater than 100,000/mm³) * Ability to provide written informed consent and cooperate with study procedures Exclusion Criteria: * Known ophthalmologic diseases affecting the optic nerve or retina (e.g., glaucoma, optic atrophy) * Active eye infection or recent ocular surgery * Known intracranial pathology affecting cerebrospinal fluid dynamics (e.g., intracranial mass, hydrocephalus, idiopathic intracranial hypertension) * History of stroke or subarachnoid hemorrhage * Hypertensive disorders of pregnancy such as preeclampsia or eclampsia * Contraindications to spinal anesthesia (e.g., coagulopathy, anticoagulant therapy, infection at puncture site) * Allergy to local anesthetics * Conversion to general anesthesia due to failed or inadequate spinal block * Presence of moderate or severe preoperative headache or active primary headache disorders such as migraine