NZ Optics March 2024
Excerpt from “Regarding menopause and eye health” by Layal Naji
Glaucoma
There is an ongoing debate about whether menopause should be considered a sex-specific risk factor for glaucoma. One meta-analysis found an inverse linear relationship between age of onset of menopause and the risk of developing open angle glaucoma (OAG)^2. This could indicate that early menopause (occurring in those aged <45, which can be due to chromosome issues, autoimmune conditions such as thyroid disease, epilepsy or individual genetics, or lifestyle factors such as history of smoking and low BMI) can be associated with an increased risk of developing OAG.
Preclinical rat studies found induction of ocular hypertension, larger vision loss (as measured by optomotor response) and retinal ganglion cell (RGC) loss (as measured by OCT) was associated with surgically induced menopause via ovariectomy^3,4. One study also found oestrogen administration played a protective role in RGC layer integrity^5; however, more studies are needed to confirm the relevance of oestrogen in glaucoma prevention.
Other animal studies investigated the effects of menopause on aqueous outflow and ocular compliance (related to the elastic properties of the sclera and cornea as well as blood circulation) to better understand whether these factors could play a role in the association between menopause and increased intraocular pressure (IOP). They found menopausal rats had a 34% decrease in aqueous outflow and 19% increase in ocular compliance when compared to controls^6, which could result in some of the physiological factors associated with glaucoma. Overall, the literature seems to indicate that in animal studies, surgically induced menopause is related to increased IOP, increased aqueous outflow resistance and ocular biomechanics – factors we know can be associated with glaucoma. Thus, it could be possible that menopause sets the stage for glaucoma to develop^5.
Human studies are limited. One found that in postmenopausal women there was an increase in IOP and biomechanics measures (resistivity index of vasculature, measures of retrobulbar blood flow), while menopausal hormone therapy (MHT) was associated with a decrease in IOP and resistivity index^7. However, a far more recent meta-analysis and systematic review of randomised control trials (RCT) found that MHT did not result in a significant reduction in IOP^8.
Studies have shown that early menopause doubles the risk of developing glaucoma, said Dr Noor Ali, a Canberra-based specialist in glaucoma, retinal disease and uveitis. “In age-matched female patients, those who have undergone menopause had average IOPs of 1.5-3.5mmHg greater than their premenopausal counterparts,” she said. “In addition, in vitro studies have suggested greater RGC loss after menopause^5. While there are many confounding factors to be considered, as a practical note, postmenopausal women would benefit from a full assessment if there are any signs (of glaucoma) in screening.”
You can read this article in full within the March 2024 issue of NZ Optics – The Magazine for New Zealand’s Ophthalmic community.