The effect of posture on the intraocular pressure and pulsatile ocular blood flow in patients with nonarteritic anterior ischaemic optic neuropathy

Abstract

Intraocular pressure (IOP) and pulsatile ocular bloodflow (POBF) have been recorded in 15 patients with unilateral non-arteritic anterior ischaemic optic neuropathy (na-AION) and in 28 healthy subjects of comparable age. Measurements were obtained in both the upright and lying postures with a pneumotonometer linked to a Langham ocular bloodflow system.By comparison with the healthy subjects, patients with na-AION were found to have a significantly greater postural pressure change in IOP (3.9 ± 0.4 mmHg in the affected eye and 3.6 ± 0.6 mmHg in the unaffected eye of the patients with na-AION compared to 2.2 ± 0.4 mmHg in the right eye of the healthy subjects P<0.01 and <0.05 respectively). There was no significant difference between the IOP in the affected and unaffected eyes of patients with na-AION nor between this group and the healthy subjects in either posture. Pulsatile ocular bloodflow measurements were similar in both groups and in both eyes of the patients with na-AION. In both groups POBF fell significantly on lying down (healthy right eyes -84 ± 16 ul/min p<0.01, na-AION affected eye -84 ± 24 ul/min p<0.01, unaffected eye -83 ± 26 ul/min p<0.001). These figures represent decrements of 19% in all groups.These findings suggest that assumption of the supine posture may be associated with a reduction in the pulsatile component of ocular perfusion. The importance of this in the pathogenesis of na-AION is discussed. © 1991, College of Ophthalmologists. All right reserved.