Optic nerve and choroidal circulation in glaucoma.
OBJECTIVE
To investigate the circulation of the optic nerve head and choroid in patients with glaucoma.


METHODS
Laser Doppler flowmetry was used to determine optic nerve head relative blood velocity (ONVel), volume (ONVol), and flow (ONFlow) in 19 primary open-angle glaucoma patients and 15 age-matched healthy control subjects. In each subject, determinations were obtained from four sites on the neuroretinal tissue and from the center of the cup. A mean of the ONVel, ONVol, and ONFlow for these five measurement sites were calculated for each subject and defined as ONVel5, ONVol5, and ONFlow5. Circulatory parameters were correlated with measures of disease progression such as cup-to-disc ratio and Humphrey visual field indices. Measurements of relative choroidal blood velocity, volume, and flow were also obtained from the foveola.


RESULTS
In glaucoma patients, mean ONFlow5 was significantly lower than in control subjects (24%; P = 0.001; independent, two-tailed Student's t-test). This decrease was caused by a significant decrease in ONVol5 (15%; P = 0.04) and a nonsignificant decrease in ONVel5 (10%; P = 0.07). In glaucomatous eyes, mean ONFlow was significantly reduced from normal, by 28% in the inferior temporal neuroretinal rim location (P = 0.001) and by 24% in the superior temporal location (P = 0.001). Although mean ONFlow was also decreased by 33% in the cup, the difference was not statistically significant after a Bonferroni correction was applied. No significant differences from normal were observed in the superior and inferior nasal rim tissues. In glaucoma patients, ONFlow5 was significantly and inversely correlated with the corrected pattern standard deviation (R = -0.53; P = 0.02) and with the cup-to-disc ratio (R = -0.65; P = 0.002). Choroidal blood flow measurements obtained in the foveola of glaucomatous eyes showed no statistically significant differences from normal.


CONCLUSIONS
ONFlow5 is reduced by approximately 24% in glaucoma patients. In the inferior temporal rim, the area in which nerve bundle defects most commonly occur, blood flow is reduced by 28%. Patients with more advanced glaucomatous damage, as detected by visual field corrected pattern standard deviation and measurement of the cup-to-disc ratio, tend to have lower ONFlow5. These results suggest a decrease in optic nerve blood flow that is correlated with functional and morphologic measures of glaucomatous progression. However, from these results we cannot conclude whether this decrease in flow has a primary role in the etiology of glaucoma or whether it is the result of the loss of neural components caused by this disease.
Grunwald
J E
JE
Department of Ophthalmology, Scheie Eye Institute, School of Medicine, University of Pennsylvania, Philadelphia 19104, USA.
Piltz
J
J
Hariprasad
S M
SM
DuPont
J
J
D000328:Adult; D000368:Aged; D001775:Blood Circulation; D001783:Blood Flow Velocity; D001810:Blood Volume; D002829:Choroid / Q000098:blood supply*; D005260:Female; D005902:Glaucoma, Open-Angle / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000098:blood supply; D009900:Optic Nerve / Q000098:blood supply*; D009901:Optic Nerve Diseases / Q000209:etiology / Q000503:physiopathology