Purpose: To investigate and present a comprehensive account of the clinical features, pathogenesis, and management of posterior ischaemic optic neuropathy (PION).
Methods: This retrospective study is based on 53 consecutive eyes of 42 patients with PION seen in my clinic since 1973, who fulfilled the inclusion criteria. They were systematically evaluated, treated, and followed by me. All patients had initially detailed ophthalmic evaluation of the anterior and posterior segments, including visual field with Goldmann perimeter and fluorescein fundus angiography. All patients aged 50 years and older were also investigated for giant cell arteritis (GCA). Every attempt was made to rule out other causes of visual loss. Follow-up evaluation was similar to the initial evaluation except angiography. Aetiologically, PION can be divided into three types: arteritic due to GCA, nonarteritic not due to GCA, and surgical following a surgical procedure. Steroid therapy was given to only those nonarteritic PION patients who opted to try that, but was given to all arteritic PION patients.
Results: PION was nonarteritic in 28 patients (35 eyes), arteritic in 12 (14 eyes), and surgical in three (four eyes). Visual acuity varied between 20/20 and no light perception--it was count fingers or less in 19 of 35 eyes with nonarteritic PION, four of 14 in arteritic, and all four with surgical PION. The most common visual field defect was central visual loss, alone or in combination with other types of visual field defects. Initially, optic disc and fundus showed no abnormality but the disc usually developed pallor in about 6-8 weeks. Aggressive treatment with high-dose systemic steroid during the very early stages of nonarteritic PION produced significant improvement of visual acuity as well as visual fields, but not so in arteritic or surgical PION. However, some spontaneous visual improvement also occurred in some untreated nonarteritic PION cases.
Conclusions: PION is a distinct clinical entity but should be diagnosed only after exclusion of all other causes of visual loss. In all patients older than 50, GCA must be ruled out. There is usually marked visual loss, with central field defect being the most common. The study suggests that high-dose steroid therapy in nonarteritic PION, soon after the onset of visual loss, resulted in significant visual improvement compared to the untreated cases, but not in arteritic and surgical PION.