Assessing the function of the optic nerve is paramount during various neurosurgical procedures. Effective optic nerve monitoring has remained elusive as Visual Evoked Potentials (the current existing tool) provides only diffuse and delayed assessment of nerve function. Here, the investigators propose a prospective study involving adult patients (aged 18 years and older) undergoing endonasal or open cranial approaches around the optic nerves, who will receive pre- and post-operative visual evaluations. During surgery, the optic nerve and chiasm will be stimulated, and the response will be recorded in both eyes and the occipital cortex via skin electrodes. The investigators aim to utilize anterograde optic nerve microstimulation to assess the nerve's integrity during open and endoscopic cranial approaches. Electrophysiological readings will be acquired, as is routine in the operating room, by our team of experts, and intraoperative findings will be correlated with post- surgical clinical outcomes. Our objective is to utilize existing technology in the operating room to safely and effectively monitor optic nerve function during surgery.

Our hypothesis is that utilizing anterograde optic nerve microstimulation during open and endoscopic cranial approaches will allow for more accurate and real-time assessment of optic nerve function compared to the current standard of Visual Evoked Potentials. The investigators predict that this novel approach will lead to improved intraoperative monitoring and better correlation with post- surgical clinical outcomes.

The study design proposed is interventional and prospective. It involves implementing a novel approach, anterograde optic nerve microstimulation, during surgical procedures to assess optic nerve integrity. This design entails actively intervening during the surgical process to stimulate the optic nerve and record responses, indicating an interventional approach.

Inclusion Criteria:

• Patients diagnosed with suprasellar tumors including meningiomas, craniopharyngiomas and pituitary adenomas.
• Must not present with any permanent or temporal visual deficit.
• Must receive an open or endoscopic endonasal procedure as part of their care.

Exclusion Criteria:

• Preexisting visual impairments unrelated to the tumor.
• History of prior cranial surgeries or radiation therapy.
• Significant cognitive impairment or inability to provide informed consent
• Contraindications to microstimulation procedures such as uncontrolled coagulopathy or active infection.
• Patients with tumors located outside the sellar region or those requiring emergent or urgent surgery due to life-threatening complications.
• Additionally, individuals with systemic conditions or comorbidities that may significantly impact visual function or surgical outcomes, such as uncontrolled diabetes mellitus or severe cardiovascular disease.