Retinal OCT Changes and Biomarkers in Drug-Resistant Epilepsy

This prospective, longitudinal observational study investigates whether epilepsy involves a progressive neurodegenerative process. Retinal structural and microvascular changes assessed by optical coherence tomography (OCT) and optical coherence (OCTA) will be analyzed alongside inflammatory biomarkers (sCD14, sCD163, CCL2, IL-1β). The study aims to explore their association with epilepsy pathophysiology, clinical phenotype, prognosis, and drug-resistant epilepsy (DRE). Among participants with epilepsy, seizure severity and antiseizure medication-related adverse-effect burden will also be assessed longitudinally using the National Hospital Seizure Severity Scale (NHS3) and the Turkish version of Liverpool Adverse Events Profile (LAEP-TR).

Inclusion Criteria: * Age between 18 and 40 years * Ability to provide written informed consent * For the epilepsy group: diagnosis of epilepsy for at least 1 year * For the epilepsy group: treatment with at least one antiseizure medication for at least 1 year * For the disease-control group: diagnosis of migraine, analgesic-overuse headache, or neuralgia * For the disease-control group: current treatment with at least one antiseizure medication for a non-epileptic indication * For the disease-control group: no history of epilepsy or unprovoked seizures * For the healthy-control group: no history of epilepsy, major neurological disease, ophthalmological disease, or regular antiseizure medication use Exclusion Criteria: * Age younger than 18 years or older than 40 years * Inability or unwillingness to provide written informed consent * History of ocular surgery, ocular trauma, glaucoma, retinal disease, optic neuropathy, or severe refractive error, defined as spherical equivalent greater than ±6.0 diopters * Media opacity or poor image quality preventing reliable OCT or OCTA assessment * Vigabatrin or Valproate use * Multiple sclerosis, Parkinson's disease, dementia, brain tumor, stroke, optic neuritis, or other major neurological disorders * Evidence of visual pathway lesions on MRI * Diabetes mellitus, uncontrolled hypertension, or other systemic vascular, metabolic diseases that may affect retinal or OCTA parameters * Chronic alcohol or psychoactive substance abuse * Inability to undergo OCT or OCTA examination because of cognitive, behavioral, or physical limitations