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A. Piccinini, C. E. Riva, B. Falsini, E. Campos; Effect of Darkness on Subfoveal Choroidal Blood Flow in Normal Subjects and Glaucoma Patients. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4605. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
A number of studies have recently shown that, in young normal subjects, subfoveal choroidal blood flow (ChBF) decreases by about 12% during 15 min of darkness following light adaptation. Recent evidence indicates that nitric oxide (NO) plays a role in this decrease. The present study aims at testing the hypothesis that this ChBF response may be altered in glaucoma, possibly due to an altered NO-mediated mechanism underlying the ChBF response.
Subfoveal ChBF was measured continuously for 30 sec approximately every 3 min by laser Doppler flowmetry, first in room light and then during 15 min of darkness. Measurements were performed in 11 (3 m, 8f) normal controls (mean age: 59 +- 11 sd y} and in 14 (8m, 6f) patients with primary open-angle glaucoma (mean age 69 +- 8 y) mostly in treatment of glaucoma (with Beta-adrenergic antagonists and/or prostaglandin analogs and/or adrenergic agonists). Mean IOP was 15 +-3 and 15 +- 2 mmHg for the normal controls and the patients, respectively. Mean ocular perfusion pressure (OPP) at the start of the experiment was 48 +- 7 mmHg for the normal subjects and 49+- 8 for the glaucoma patients.
In the normal subjects there was a significant decrease in ChBF during darkness (linear correlation r = 0.29, p < 0.01). Based on the ChBF values between 12 and 15 min, this decrease amounted to an average of 15% +- 12 (95% conf. lim.). The decrease of 1.4+- 6% in the glaucoma patient was not significant. These decreases could not be attributed to a change in OPP during the 15 min of darkness (-0.2 mmHg in controls and -2 mmHg in glaucoma patients).
In the normal control group, the decrease of ChBF during 15 min of darkness is similar to the value previously obtained in a group of younger subjects (mean age 35 y). In contrast, ChBF did not change in the group of glaucoma patients. This finding supports the hypothesis that the mechanism underlying the ChBF response to darkness is altered in this disease.
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