Postmenopausal Hormone Therapy Increases Retinal Blood Flow and Protects the Retinal Nerve Fiber Layer

Micheline C. Deschênes, Denise Descovich, Michèle Moreau, Louis Granger, George A. Kuchel, Tomi S. Mikkola, Gordon H. Fick, Sylvain Chemtob, Elvire Vaucher, Mark R. Lesk
2010 Investigative Ophthalmology and Visual Science  
PURPOSE. To investigate whether postmenopausal hormone therapy (HT) increases retinal and ONH blood flow (BF) and protects ONH topography and the function of retinal ganglion cells in postmenopausal women (PMW). The effect of estradiol (E 2 ) treatment on retinal tissue perfusion was also investigated in ovariectomized rats, an animal model for menopause. METHODS. Sixty-four healthy PMW were recruited, 29 of whom never used HT (AHT) and 35 of whom had used HT (ϩHT) continuously since the onset
more » ... ly since the onset of menopause. Blood flow of the inferotemporal retinal artery (ITRA), peripapillary retina, and ONH rim were measured in one eye. The ONH stereometric parameters and the pattern electroretinogram (PERG) were also measured. In ovariectomized rats, the retinal tissue perfusion was assessed using the BF tracer N-isopropyl-p-[ 14 C]-iodoamphetamine ([ 14 C]-IMP) in rats treated with either E 2 (n ϭ 7) or placebo (n ϭ 5). RESULTS. Compared with the AHT group, the ϩHT group presented significantly greater BF of the ITRA (P ϭ 0.006), greater rim volume for the entire ONH region (P ϭ 0.032), and greater rim volume (P ϭ 0.042), height variation contour (P ϭ 0.011), mean thickness (P ϭ 0.033), and cross-sectional area (P ϭ 0.020) of the retinal nerve fiber layer for the inferotemporal region of the ONH when adjusted for age, ocular perfusion pressure, and age at menarche. In ovariectomized rats, E 2 treatment significantly increased retinal perfusion in a range of 22% to 45%. CONCLUSIONS. These findings indicate that estrogens and HT increase retinal blood flow and protect the retinal nerve fiber layer. (Invest Ophthalmol Vis Sci. M enopause is the permanent cessation of menstruation resulting from the loss of ovarian follicular activity 1 that leads to a decline in endogenous estrogens and progesterone (P) production in aging women. Postmenopausal hormone therapy (HT), consisting of estrogens alone or combined with progestogens, is frequently prescribed to women to alleviate postmenopausal symptoms. Estrogens have the ability to influence the vascular tone and blood flow in organs and tissues 2 and to have neuroprotective effects via nonvascular mechanisms. 3 In postmenopausal women, the use of HT has been shown to increase blood flow in the femoral artery 4 and brain parenchyma, 5,6 and to improve the pulsatility and/or resistivity indexes in the common carotid, 7 internal carotid, 8 -10 and middle cerebral arteries. 9 The use of HT has also been shown to have a protective effect in some regions of the brain in postmenopausal women by preventing cerebral tissue atrophy. 11, 12 There is increasing evidence that impaired ocular blood flow is a contributing factor in the etiology and progression of glaucoma and age-related macular degeneration (ARMD). 13, 14 Recently, there has been an increasing interest in investigating possible associations between endogenous estrogens and the use of HT with glaucoma and ARMD. Epidemiologic population-based studies have indicated that increased duration of exposure to endogenous estrogens (early menarche, late menopause onset, and increasing reproductive years) significantly decreases the odds ratio of developing primary openangle glaucoma 15, 16 and ARMD. 17 With regard to the use of HT, it has been shown to decrease the odds ratio of open-angle glaucoma by half, but the decrease did not reach statistical significance, 15 and no associations were found with intraocular pressure (IOP), cup/disc ratio, or the prevalence of increased IOP and glaucoma. 18 In ARMD, HT has been reported to significantly decrease the odds ratio of advanced 19 and neovascular ARMD, 20 whereas no associations were found between the use of HT or its duration and ARMD risk. 21 These somewhat divergent findings regarding the possible protective effect of HT against glaucoma and ARMD have also been reported in cardiovascular diseases. 22, 23 The divergent findings in cardiovascular disease have been explained by the variable time of HT initiation after menopause. To be effective against cardiovascular disease, HT must be prescribed to menopausal women during the "window of opportunity" (i.e., in the first five to six From the
doi:10.1167/iovs.09-3710 pmid:20019375 fatcat:ip4ilztzprfzrnmqt4j57omyea