Open-Angle vs Closed-Angle Glaucoma: Anatomical and Gonioscopic Differentiation

A 62-year-old hyperopic woman with a family history of glaucoma presents with acute onset of severe ocular pain, blurred vision, and halos around lights in her right eye. Examination reveals a mid-dilated pupil, corneal edema, and intraocular pressure of 58 mmHg. Gonioscopy performed after resolution of corneal edema shows a narrow angle with peripheral anterior synechiae. Which of the following findings would BEST differentiate this acute presentation from a chronic open-angle glaucoma patient with similar IOP elevation?