The effect of 5-isosorbide mononitrate (ISMO) on optic nerve head and foveal choroidal blood flow
Purpose. A recent report has suggested that nitrates may delay the progression of glaucoma (IOVS, 36: S219, 1995). The purpose of this study was to assess the effects of ISMO, a long-acting nitro-vasodilator widely used in ischémie cardiovascular diseases, on optic nerve head (ONBF) and choroidal (ChBF) blood flow. Methods. Laser Doppler flowmetry was used to determine relative ONBF and ChBF in 12 normal volunteers with a normal eye examination. In a doublemasked, randomized, cross-over design, each subject received orally either 20 mg of ISMO or placebo. Measurements were obtained on two separate days (washout period > 4 days). Following pupil dilatation, ChBF was determined aiming the laser beam at the fovea. ONBF was calculated as the average of measurements from two locations at the temporal rim. In all subjects, determinations were done in one eye at baseline, and 1 hr after dosing. In the 6 last subjects, an additional measurement was obtained 3 hrs after dosing. Results. No significant change in ONBF was observed following placebo (baseline: 15.2 ±1.1 arbitrary units [AU], ±1 SEM; 1 hr; 14.5 ±0.8 AU; 3 hrs: 14 7 ±1.4 AU), whereas following ISMO, ONBF increased from 15.8 ±2.3 AU at baseline to 17.2 ±1.2 AU at 1 hr (p=0.43; n=12) and 17.7 ±1.7 AU at 3 hrs (p=0.009, n=6). Compared to placebo, ISMO produced an average ONBF increase from baseline of 19-8 ±9.3% at 1hr (p=0.058), and of 33.1 ±7.5% at 3 hrs (p=0.007). in contrast, no significant change in ChBF was observed. Conclusions. Our results suggest that in normal subjects, ISMO increases significantly ONBF, but not ChBF. Further studies are needed to determine whether ISMO may have a role in the treatment of glaucoma and other ischémie conditions of the optic nerve head.
Iannaccone, A; Grunwald, JE; Dupont, J
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