Diagnosis of a chiasmal lesion compressing optic chiasm in patients with severe retinal degeneration: a two-case report

Optic chiasmal compression is an important cause of progressive visual dysfunction, and early diagnosis is essential to prevent irreversible vision loss. However, recognition can be delayed when patients have pre-existing ocular diseases that independently impair vision. Severe retinal degeneration may obscure the clinical signs of chiasmal compression and complicate diagnostic evaluation. Here, we report two elderly patients with advanced retinal degeneration in whom pituitary tumors compressing the optic chiasm were initially unrecognized, highlighting important diagnostic challenges and clinical considerations for improving diagnostic accuracy. Case 1: An 84-year-old woman presented with a three-year history of progressively worsening visual field defects and blurred vision. She had been under regular follow-up and treatment for longstanding polypoidal choroidal vasculopathy in the right eye and central serous chorioretinopathy in the left eye. Although fundus examination and optical coherence tomography demonstrated advanced macular changes, these findings were considered insufficient to fully explain the degree of visual decline. Visual field testing, performed to evaluate her subjective visual disturbance, revealed bitemporal hemianopia. Magnetic resonance imaging (MRI) demonstrated a large pituitary adenoma compressing the optic chiasm. Case 2: A 79-year-old man with severe myopic degeneration and pre-existing low vision presented with unexplained progressive visual decline over 1.5 years. Although fundus examination demonstrated advanced myopic changes, the severity and progression of visual loss were not fully explained by the underlying retinal findings. At initial presentation, a relative afferent pupillary defect was noted in the right eye, prompting further evaluation. Visual field testing and neuroimaging were performed at the initial visit. MRI revealed a pituitary adenoma extending into the suprasellar region with optic chiasmal compression. Optic chiasmal compression should be considered in patients with severe retinal degeneration presenting with progressive visual decline that cannot be fully explained by retinal pathology. Visual field testing and timely neuroimaging, particularly MRI, are essential for accurate diagnosis and may help prevent irreversible visual loss.