Correlation of peripapillary retinal nerve fibre layer thickness with visual acuity in paediatric patients affected by optic pathway glioma

Purpose: To evaluate peripapillary retinal nerve fibre layer (RNFL) thickness, measured by spectral-domain optical coherence tomography (SD-OCT), as a surrogate of visual function in a population of paediatric patients affected by optic pathway glioma (OPG) associated with neurofibromatosis type 1 (NF1). Methods: A total of 38 paediatric patients (66 eyes) affected by MRI-proven OPG were included. Each patient underwent complete ophthalmological examination, including age-appropriate visual acuity (VA) assessment and RNFL analysis by SD-OCT. Visual acuity was classified as normal or pathologic using age-based normative data. Visual acuity was correlated to mean RNFL thickness of the whole peripapillary area and of each single analyzed sector (nasal, superior, temporal, inferior). Results: Visual acuity was normal in 43 (65%) and pathologic in 23 (35%) eyes. Mean parapapillary RNFL thickness of each analyzed sector was significantly lower in eyes with abnormal VA (p < 0.05). The best balanced cut-off value of global RNFL thickness allowing to discriminate between eyes with normal and pathologic VA was 76.25 μm (91%, 76%, 67% and 94% of sensitivity, specificity, positive and negative predicting value, respectively). Considering best balanced cut-off values of other analyzed RNFL sectors, the superior (p = 0.0029) and the inferior (p = 0.0024) sectors reached the higher sensitivity (87% and 87%, respectively) and specificity (81% and 79%, respectively). Conclusion: Retinal nerve fibre layer thickness is directly related to VA in children affected by NF1-related OPG, and should be considered as a potential surrogate marker of VA. Retinal nerve fibre layer thickness cut-off values can be used in paediatric patients to discriminate false-positive results obtained by VA measurement.