The Relationship Between the Ganglion Cell–Inner Plexiform Layer, Retinal Nerve Fiber Layer, and Photopic Negative Response in Newly Diagnosed Pituitary Macroadenoma: 12-Month Prospective Follow-Up Study

Background/Objectives: This prospective study evaluates the relationship between the ganglion cell–inner plexiform layer (GCIPL), retinal nerve fiber layer (RNFL), and photopic negative response (PhNR) in patients with newly diagnosed pituitary macroadenomas over 12 months. Methods: A total of 40 patients (80 eyes) were included, divided into a treatment group of 27 patients (54 eyes), receiving pharmacological and/or surgical intervention, and an observation group of 13 patients (26 eyes), with non-functional pituitary adenomas (NFPAs) that did not require treatment. Results: Key findings indicate a significant improvement in best corrected visual acuity (BCVA) after 12 months in the treatment group (p = 0.02) and a significant reduction in RNFL thickness in multiple quadrants (p < 0.01). Moreover, PhNR amplitude and W-ratio significantly increased in the treatment group (p < 0.0001). In the observation group, only GCIPL Inferior (p = 0.0470) and PhNR W-ratio (p = 0.0015) showed significant differences. Between-group comparisons showed significant differences in RNFL Nasal quadrant at baseline (p = 0.0017) and after 12 months (p = 0.0150). PhNR amplitude and W-ratio also differed significantly between groups at 12 months (p = 0.0012 and p = 0.0016, respectively). Correlations between OCT and ERG parameters were weak at baseline and diminished over time. Conclusions: These findings suggest that GCIPL, RNFL, and PhNR analyses may be useful for monitoring disease progression and guiding treatment decisions in patients with pituitary macroadenomas.