Clinical usefulness of the measurement of blood flow in myopic optic nerve heads in patients with normal-tension glaucoma

AIM: Diagnosis of glaucoma is often difficult in patients with myopic changes in the optic nerve head. We investigated the clinical usefulness of measuring blood flow in myopic optic nerve heads for the diagnosis of glaucoma, particularly normal-tension glaucoma. METHODS: Forty eyes, including 20 with normal-tension glaucoma and 20 without glaucoma, of 40 patients with myopic optic nerve heads (oval and tilting to the temporal side with crescent peripapillary atrophy) and visual field defects were evaluated. Blood flow in the optic nerve head was assessed by laser speckle flowgraphy, and the mean blur rates for the entire optic nerve head and for its vessels and tissue were analyzed. The mean deviation and the circumpapillary retinal nerve fiber layer thickness were determined using the Humphrey Field Analyzer and optical coherence tomography, respectively. The mean blur rates were compared between the two groups, and their correlation with the mean deviation and circumpapillary retinal nerve fiber layer thickness were verified using simple regression analyses. RESULTS: The mean blur rates for the entire optic nerve head and for its tissue were significantly lower in glaucomatous eyes than in nonglaucomatous eyes, and both values correlated with the mean deviation only in the former group. The mean blur rate for the optic nerve head tissue did not depend on the circumpapillary retinal nerve fiber layer thickness in glaucomatous eyes. CONCLUSION : Blood flow in the optic nerve head, particularly the tissue, may be useful for the differential diagnosis of normal-tension glaucoma in patients with myopia.