RELATION BETWEEN PRESSURE DETERMINED BY OPHTHALMODYNAMOMETRY AND AORTIC PRESSURE IN THE DOG

Aims-Ophthalmodynamometry has been used extensively since the last cen tury; however, controversy surrounds what it actually measures. This s tudy was set up to determine the relation between ophthalmodynamometri c (ODP) and systemic blood pressures. Methods-Aortic pressure was cont inuously monitored and altered by phlebotomy in six anaesthetised dogs , while ophthalmodynamometry was performed, by directly altering intra ocular pressure. Maxillary artery pressure was monitored in two animal s. All pressure transducers were zeroed at eye level. Results-Mean ODP was 96.6% (1.6%) (95% confidence interval, n = 49) of aortic pressure . Mean maxillary artery pressure was 95.7% (5.5%) (95% CI, n = 16) of aortic pressure. ODP was 1.9 (0.6) mm Hg (95% CI, n = 33) higher than maxillary artery pressures. Conclusion-ODP was only slightly below aor tic pressure and not significantly different hom maxillary artery pres sure, the analogue of the internal carotid artery in humans. These res ults also suggest a retinal artery collapse pressure of at least 1.9 m m Hg.