Retinal OCT Changes and Biomarkers in Drug-Resistant Epilepsy

Condition(s) studied

Study summary

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).

Eligibility

Primary outcome measure(s)

• Annualized percentage change in peripapillary retinal nerve fiber layer thickness measured by OCT — Baseline to 18 months after enrollment.
  Peripapillary RNFL thickness will be assessed with Heidelberg OCT at baseline and 18 months using the optic nerve head-centered circular scan protocol. Eye-tracking and follow-up registration will ensure reproducibility. Automated segmentation will be reviewed for centration and accuracy; global and quadrant values (superior, inferior, nasal, temporal) will be recorded. Images will be checked for quality and artifacts; scans failing criteria or with uncorrectable errors will be repeated or excluded. For participants with two eligible eyes, mean thickness will be analyzed; if one eye is eligible, that measurement will be used. Annualized percentage change will be calculated as: \[((18-month pRNFL thickness - baseline pRNFL thickness) / baseline pRNFL thickness) × 100\] / 1.5 years. Unit of measure: Percent change per year
• Annualized percentage change in ganglion cell-inner plexiform layer thickness measured by OCT — Baseline to 18 months after enrollment
  Ganglion cell-inner plexiform layer (GC-IPL) thickness will be measured with Heidelberg OCT at baseline and 18 months using a fovea-centered 6 × 6 mm macular scan. Identical parameters and eye-tracking functions will ensure reproducibility. Automated segmentation will be reviewed for centration, accuracy, and artifacts; errors will be corrected when possible. GC-IPL thickness will be calculated as the sum of ganglion cell and inner plexiform layers. Scans failing quality criteria or with uncorrectable artifacts will be repeated or excluded. For two eligible eyes, mean thickness will be analyzed; if one eye is eligible, that measurement will be used. Annualized percentage change will be calculated as: {\[(18-month GC-IPL thickness - baseline GC-IPL thickness) / baseline GC-IPL thickness\] × 100} / 1.5 years. Unit of measure: Percent change per year
• Difference in annualized percentage change in peripapillary retinal nerve fiber layer thickness between drug-resistant and non-drug-resistant epilepsy groups — Baseline to 18 months after enrollment.
  Annualized percentage change in peripapillary retinal nerve fiber layer thickness measured by optical coherence tomography will be compared between participants with drug-resistant epilepsy and participants without drug-resistant epilepsy. This analysis will be performed only among participants with epilepsy. Drug-resistant epilepsy will be defined as failure of adequate trials of two tolerated, appropriately chosen and used antiseizure medication schedules to achieve sustained seizure freedom. Unit of measure: Percent change per year
• Difference in annualized percentage change in ganglion cell-inner plexiform layer thickness between drug-resistant and non-drug-resistant epilepsy groups — Baseline to 18 months after enrollment.
  Annualized percentage change in ganglion cell-inner plexiform layer thickness measured by macular optical coherence tomography will be compared between participants with drug-resistant epilepsy and participants without drug-resistant epilepsy. This analysis will be performed only among participants with epilepsy. Drug-resistant epilepsy will be defined as failure of adequate trials of two tolerated, appropriately chosen and used antiseizure medication schedules to achieve sustained seizure freedom. Unit of measure: Percent change per year

Trial sites (1)

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