OBJECTIVE: To assess the frequency of open-angle glaucoma in Caucasian patients affected by idiopathic normal pressure hydrocephalus (iNPH) prior to ventriculo-peritoneal shunt surgery, and to evaluate the progression of optic nerve damage 1-year postsurgery. METHODS: Thirty-five consecutive patients diagnosed with iNPH were prospectively recruited between November 2021 and June 2023. Assessments included visual acuity, intraocular pressure, macular ganglion cell complex thickness, retinal nerve fiber layer thickness, visual field test, central corneal thickness, axial length, and corneal hysteresis. Patients with newly diagnosed open-angle glaucoma were initiated on intraocular pressure-lowering medications. Eighteen patients were re-evaluated after a mean of 1 year postshunt surgery to assess the progression of optic nerve damage. RESULTS: A total of 35 eyes of 35 iNPH patients were included. The mean age of participants was 75.75 ± 6.67 years, with 34.3% being females. Primary open-angle glaucoma was identified in 22.8% of nonshunted iNPH patients, including 11.4% who received a new diagnosis. After a mean follow-up of 14.9 ± 4.8 months postsurgery, there were no significant changes in retinal nerve fiber layer and ganglion cell complex thickness, nor were there any observed progressions in visual field defects or significant alterations in corneal biomechanics (P >
0.05). CONCLUSIONS: Approximately 1 in 5 nonshunted iNPH patients exhibited primary open-angle glaucoma, with 50% being undiagnosed. These findings indicate the importance of conducting ophthalmological evaluations at the time of iNPH diagnosis, as early intervention may mitigate optic nerve damage progression following shunt surgery.