Relationship between retinal nerve fibre thickness, suprasellar extension and post-operative visual outcome in pituitary macroadenoma

To evaluate the relationship between retinal nerve fibre layer (RNFL) thickness, suprasellar extension (SSE), tumour volume (TV) and visual outcome after pituitary adenoma surgery.

A prospective observational study was conducted in a tertiary teaching hospital which included patients with pituitary macroadenoma who required surgical resection between December 2015 to February 2020. Agreeable subjects underwent complete ocular examination, Humphrey visual field (HVF) and RNFL measurement using spectral domain optical coherence tomography preoperatively and 3-month postoperatively. Post-operative visual outcome was evaluated using both best-corrected visual acuity (BCVA, logMAR) and HVF mean deviation (MD). TV was estimated by multiplying the transverse, anteroposterior, and craniocaudal maximum diameter; and SSE by measuring tumour extension beyond the supraclinoid internal carotid artery from magnetic resonance imaging.

Thirty-eight patients (18 males) were recruited. The mean age was 47.6±14.8y. The median and interquartile range (IQR) was 10.78 (6.45–16.94) cm³ and 14.05 (4.99–22.90) mm for TV and SSE, respectively. While postoperative RNFL significantly reduced in all sectors, significant improvement was seen in median BCVA in logMAR (from 0.301 to 0.176, P<0.001) and MD of HVF (from -10.04 to -3.91, P<0.001). Pre-operative global RNFL was significantly correlated with post-operative logMAR (r=-0.303, P=0.015) and MD (r=0.510, P<0.001). Only SSE showed significant negative correlations with all RNFL sectors. Each 10 µm thicker pre-operative global RNFL was associated with 0.13 lower (better) postoperative logMAR (β=-0.013, P<0.001) and 0.83 dB higher (better) MD (β=0.083, P=0.008). Patients with normal RNFL had better post-operative MD [median (IQR)=-2.35 (-1.45, -5.94)] than with thinned RNFL [median (IQR)=-6.63 (-2.80, -8.77), P=0.009].

SSE shows stronger association with RNFL thinning than TV, and thicker pre-operative RNFL predicted better post-operative visual outcomes.