OPTIC-NERVE HEAD CIRCULATION IN UNTREATED OCULAR HYPERTENSION

Aims-The laser Doppler technique was used to compare the capillary blo od speed measured at localised sites of the optic nerve head in stable , untreated ocular hypertensive patients with that measured in healthy normal subjects. The stereophotogrammetric technique was also used to measure the retinal nerve fibre layer thickness at the disc margin in the eyes of the patients. Methods-Doppler broadening measurements wer e made at superior and inferior temporal disc sites in 18 eyes of 10 o cular hypertensive patients and in 12 eyes of seven age and sex-matche d normal subjects. Results-On average, Doppler broadening and, hence, capillary blood speed were significantly higher (p=0.018) in the patie nts than in the normal subjects. The largest values of Doppler broaden ing in the patients were measured at sites adjacent to the thinnest re tinal nerve fibre layer. Linear regression analysis showed a significa nt inverse relation (p=0.0004) between Doppler broadening and nerve fi bre layer thickness in left eyes, and a nearly significant relation (p =0.06) in right eyes. At temporal sites of the optic nerve head there is a compensatory relation between a thinning nerve fibre layer and a locally increasing blood supply to the optic nerve head. Conclusion-To gether with previous observations of fluorescein filling defects in si milar patients, these results indicate that there is spatial heterogen eity of blood flow in the optic nerve head in stable, untreated ocular hypertensive patients.