Multiple factors, including increased intraocular pressure, contribute to the development of glaucoma, and the additional etiological contribution of ocular blood flow impairment has been a subject of debate for a long time. Recently, the advent of laser speckle flowgraphy (LSFG), an imaging technique that permits simple and reproducible evaluation of the ocular circulation, has accelerated research on the relationship between glaucoma pathophysiology and ocular blood flow impairment. We used LSFG to measure the ocular blood flow levels according to glaucoma stages and confirmed that the blood flow level in eyes with glaucoma was lower than that in eyes without glaucoma and that the ocular blood flow level decreased further as the glaucoma severity increased. Furthermore, we found that ocular blood flow was already impaired in eyes with preperimetric glaucoma, a stage that precedes the occurrence of visual field defects, and that ocular blood flow impairment at baseline aggravated the visual field defects at later stages. These results indicate that ocular blood flow impairment precedes the visual field defects. However, the temporal relationship between blood flow impairment and neurodegeneration in glaucoma remains unknown. Disuse as a result of neurodegeneration could not be ruled out as a cause for blood flow impairment because neurodegeneration, as a structural change, has also been reported to precede the occurrence of visual field disturbance as a functional change. To determine whether ocular blood flow impairment in eyes with glaucoma is a cause or a consequence of neurodegeneration, it is important to clarify the temporal relationship between the two. Thus, we analyzed longitudinal big data collected from patients with open angle glaucoma who underwent both LSFG and optical coherence tomography (OCT) examinations at a minimum of five different time points during a follow-up period of at least 2 years. The results revealed that the optic nerve head blood flow decreased before structural changes were observed via OCT in subjects who met at least two of the following criteria: advanced age, tachycardia, and the superotemporal optic nerve head quadrant. This study is the first to show that ocular blood flow impairment is a causative factor in some patients with glaucoma who receive treatment at our hospital depending on systemic factors and the optic nerve head quadrant.
Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 126: 941-947, 2022.