Retinal nerve fiber layer thickness in epilepsy: a meta-analysis comparing affected patients with healthy controls

Objective
Emerging evidence suggests that neurophysiological alterations in epilepsy may contribute to retinal changes. This meta-analysis aimed to evaluate retinal nerve fiber layer (RNFL) thickness in patients with epilepsy compared to healthy controls, as measured by optical coherence tomography (OCT).

Methods
We systematically searched PubMed, Web of Science, and Scopus for studies published from inception to December 1, 2024, assessing RNFL thickness using OCT in epilepsy patients versus healthy individuals. Clinical studies and systematic reviews were included. The subjects were patients with epilepsy diagnosed by clinicians. Patients with suspected epilepsy were not included in this study analysis. There were no language or geographical restrictions.Two authors independently evaluated the quality of the literature, and a third party arbitrated the different evaluation results. Only literature judged to be of medium or high quality was included. This paper conducted a meta-analysis of the RNFL values collected from epilepsy patients and healthy controls, and conducted subgroup analysis and heterogeneity analysis on epilepsy type, epilepsy duration, OCT type, and study type.Data were analyzed using R studio (version 4.4.1).

Results
A total of 20 studies involving 1307 epilepsy patients and 880 controls were included. The pooled analysis revealed a significantly reduced mean RNFL thickness in epilepsy patients compared to controls (random-effects model, Standardized Mean Difference (SMD)= -0.62, 95% CI -0.82 to -0.42, I² = 73%, p < 0.01). Subgroup analysis indicated that country accounted for a part of heterogeneity (Q = 9.98, df = 2, p = 0.0068). Further analysis based on national income levels (middle or high-income) demonstrated a consistent effect (SMD = -0.62, 95% CI -0.82 to -0.42, I² = 73.5%, p < 0.0001). No significant differences were observed in subgroup analyses based on OCT type (p = 0.36) or study design (p = 0.54).

Conclusion
OCT can be used as an examination instrument to detect changes in brain nerves.This Meta-review suggests that there is an association between epilepsy and changes in the optic nerve, Mean RNFL thickness is significantly decreased in epilepsy patients relative to healthy controls.It provides a theoretical basis for utilizing RNFL alterations as potential structural indicators associated with disease progression in patients with epilepsy. Furthermore, it offers a conceptual framework for future investigations exploring the relationship between observable ocular structural changes and epilepsy-related neurological processes.