More than 40 million people worldwide are blind or visually impaired; of that, more than two-thirds are women. An estimated 3.4 million people are visually impaired in the
As the population ages, these numbers will rise over the next 20 years, which will have a significant impact on the health and well-being of the population as a wholeas well as the entire eye care community.
The Women"s Eye Health Task Force Worldwide, two-thirds of blindness and visual impairment occurs in women. Three-quarters of visual impairment is estimated to be preventable or correctable. One-third of age-related macular disease and cataract cases may be linked to smoking. Four-fifths of blindness and visual impairment occurs in developing countries. Are intrinsically more prevalent in women. Occur more often in women because they live longer than men. Are exacerbated by nutritional habits, smoking and/or environmental insult.
Did you know:
In 2001, researchers from Schepens Eye Research Institute joined forces with colleagues from around the
Specifically, the mission of the Womens Eye Health Task Force is to educate people regarding those eye diseases that:
For more information on the Womens Eye Health Task Force, go to www.womenseyehealth.org.
The Women"s Eye Health Task Force
Worldwide, two-thirds of blindness and visual impairment occurs in women.
Three-quarters of visual impairment is estimated to be preventable or correctable.
One-third of age-related macular disease and cataract cases may be linked to smoking.
Four-fifths of blindness and visual impairment occurs in developing countries.
Are intrinsically more prevalent in women.
Occur more often in women because they live longer than men.
Are exacerbated by nutritional habits, smoking and/or environmental insult.
Women Arent Small Men
Over the last 20 years, there has been increasing interest in furthering the understanding of womens health issues. Major studies, such as the NIH-funded Womens Health Initiative, have shed light on health concerns that differentiate men from women.
In eye-care research, gender has been evaluated as a risk factor for numerous eye disorders, such as dry eye, cataract and macular degeneration, although a formal gender-based review in ocular disease has not yet been performed. But, the prevalence of eye disorders in women, the leading causes of blindness, and the impact of hormones on womens ocular health may be related since more women in the world are visually impaired than men.
Health Care Utilization
Men and women are different when it comes to health care. For example, women utilize the health care system more frequently than do men.
Exempting referral for cataract surgery, the ophthalmologic literature is limited in studies of gender-based differences. Studies have shown, however, that health care providers refer more women than men for cataract surgery, and cataract extraction is performed more frequently in women.
Gender-based differences in systemic disease have been widely examined in North America and
Cataracts: More Common in Women?
Visual impairment can be attributed to a number of ocular disordersmany of which are treatable or preventable. For example, cataract remains the leading cause of blindness and visual impairment worldwide, excepting most developed countries.6 Also, even though gender differences related to visual impairment have only recently been explored, it is now generally accepted that in every region of the world, females from all age groups have a significantly higher risk of being visually impaired than males, according to the World Health Organization (WHO).
Unlike other causes of blindness, cataracts can be treated successfully with refractive or intraocular lens surgery. The impact of hormones on the lens is one possible factor. Also, after adjustment for age, cigarette smoking and higher body-mass index have been associated with increased risk of cataracts in both men and women.7,8
In women, diabetes, a clinical history of diabetes and/or hypertension also are associated with an increased risk of cataract extraction.7,8 The Wisconsin Epidemiologic Study of Diabetic Retinopathy also demonstrated that diabetes and the severity of diabetes have been associated with an increased risk for cataract development.9
Cataract extraction is performed more frequently in females than males.10,11 But, do women have more cataracts, or do they just report more problems with visual symptoms? Preoperatively, women report more subjective problems with distance estimation and orientation in unfamiliar surroundings, as well as visit the doctor more frequently for other medical complaints.12,13 In that regard, they have greater opportunity to mention visual problems or verbalize complaints more than men.12,13
It remains unclear, however, whether women develop cataracts faster or more severely than men. Some evidence suggests that using hormone replacement therapy (HRT) may have an impact on the development of nuclear cataracts.14
Currently, use of postmenopausal estrogen is associated with a decreased risk of more severe nuclear sclerosis; being at a younger age at the time of the initial menstruation period is also associated with a protective effect.14
On the other hand, being of older age at menopause is associated with a decreased risk of cortical opacities.14 Estrogen seems to have a modest protective effect against cataract development; therefore, loss of estrogen during the menopause process may impact cataract development. Follow-up studies in the
AMD: The Influence of Hormones
Unlike cataracts, efforts to manage age-related macular degeneration (AMD) are more preventative in nature. Several studies on the impact of antioxidants and other supplements on the development and progression of AMD have been reported in both the literature and popular press over the last 10 years. To a lesser degree, the impact of hormones on the progression of the disease has been exploredbut, it is challenging to separate the two.
Age-related macular degeneration is the most common cause of irreversible blindness in developed countries among persons age 65 and older. In addition, AMD ranks second after diabetic retinopathy as the leading cause of blindness in people between 45 and 65 years of age. Nearly 30% of those older than 75 years of age are affected by AMD.16
Numerous risk factors have been postulated for AMD. These include: heredity, gender (more women are affected than men), light ocular pigmentation, hypertension and cardiovascular disease, dermal elastic degeneration in sun-protected skin, cigarette smoking and phototoxicity. Meta-analysis of large studies indicates that smoking and serum cholesterol levels are related to an increased risk for the development of macular degeneration in both men and women, while an older age at menopause for women may be positively associated with incident geographic atrophy.17
Clinically, it has been hypothesized that women are more likely to have macular degeneration. But, large population-based studies have failed to consistently find female gender as a factor associated with macular degeneration when controlled for age.17 Though smoking, cardiovascular disease and soft drusen all play a role in the development of AMD in women, age is the most important factor. With women living longer, eye-care professionals will likely see more older women with macular changes and degeneration.
The effect of hormone replacement therapy on AMD progression has also been evaluated. Two studies address the association between AMD and hormone replacement therapy using estrogen. The Eye Disease Case-Control Study found that the risk of neovascular AMD was reduced by 70% in women currently using HRT, and by 40% in women who had used it prior to the study. Adjustment for covariates did not affect these associations.17
A report from the Beaver Dam Eye Study based on cross-sectional data also suggested a small protective effect of HRT on neovascular maculopathy.18 But, a report from the Womens Health Initiative demonstrated that while progestin-estrogen HRT may reduce the risk of soft drusen and neovascular AMD, neither estrogen-only nor progestin-estrogen HRT affect early or late-stage AMD.19 The impact of hormonal control in macular degeneration is complex, and it is most likely influenced by additional systemic, dietary and environmental factors.
Even though diabetes and diabetic retinopathy have been studied extensively, conflicting reports of gender differences appear in the literature. Some population-based studies have demonstrated no significant gender difference in the prevalence of diabetic retinopathy, but severe vision loss related to high-risk proliferative retinopathy has been associated with females.20
Various predictors of diabetic retinopathy exist; however, it has been well established that the best indicator of retinopathy is the duration of the diabetes itself.21
Patients who have had type 1 diabetes (insulin-dependent diabetes mellitus) for five years or less rarely show any evidence of diabetic retinopathy, while 71% to 90% of those who have had type 1 for longer than 10 years have diabetic retinopathy.21 After 20 to 30 years, the incidence rises to 95%, and of these patients, roughly one-third to one-half have proliferative diabetic retinopathy (PDR).
In cases of type 2 diabetes, determining the role of the duration of diabetes as a predictor of retinopathy is more difficult, due to the uncertainty of onset in many patients. The Wisconsin Epidemiologic Study of diabetic retinopathy showed that 10 years after a diagnosis of type 2 diabetes, 67% of patients had retinopathy and 10% had PDR.21
Diabetic complications may occur during pregnancy, and the care of pregnant women with pre-existing diabetes or diabetes that developed during pregnancy is within the scope of the optometric profession.
In women with diabetes who begin a pregnancy with no retinopathy, the risk of subsequently developing retinopathy is between 10% and 26%.22 Of women with diabetes and non-proliferative retinopathy (of any severity) who become pregnant, 4% to 22% will progress to PDR.22 But, there is usually some regression of retinopathy after delivery and after treatment with laser photocoagulation. The physiological role of hormonal changes on the vascular system of the eye during pregnancy is not clearly defined; however, the increased incidence of retinopathy in pregnancy indicates a likely role.
Glaucoma: No Gender Relation?
Is glaucoma linked to gender? Discrepancies exist in the research. For example, the Rotterdam Study (
However, after adjusting for age, several longitudinal studies, such as the Beaver Dam Eye Study, the Baltimore Eye Study, and the Melbourne Visual Impairment Project, all found no difference between males and females.
So, at this time, the evidence does not definitively support or refute a gender difference or hormonal association in glaucoma. But, as our understanding of the disease continues, so will our understanding of its predisposing factors.
Dry Eye: A Womens Disease?
Tear composition and stability deteriorate with increasing age.26 But, in addition to the effect of age, hormones may also play a role in cases of dry eye.
Postmenopausal women may suffer more frequently from dry eye than younger women.27-29 While the etiology of dry eye in postmenopausal women is unclear, the influence of hormones seems likely. Postmenopausal women with dry eye symptoms present often in clinical practice, and usually report increasing difficulty with contact lens wear and decreased quality of life due to visual complaints.30
Androgens, progestins and estrogens may exert significant influence on the structure and function of many ocular tissues, including those pertinent to dry eye, such as the lacrimal gland and anterior surface of the eye.31 The lacrimal gland has receptors for androgen and prolactin; both of these affect tear production.32,33
Topical hormones have been used experimentally for the treatment of dry eye, and FDA clinical trials using topical androgens are underway. Topical estrogen gel and 17B-oestradiol have been evaluated in smaller studies with postmenopausal women. These resulted in improvement of symptoms, although large scale clinical trials have not been performed.34
On the other hand, oral HRT has been found to be a risk factor for dry eye.35 Estrogen-only HRT resulted in a 69% higher risk than progestin-estrogen HRT, which only increased risk of dry eye by 29%. Symptoms of dryness increased with duration of HRT.35 Local estrogen and androgen control at the meibomian and lacrimal glands may play a role in these dry eye cases, and evidence to date has been compelling in demonstrating the impact of androgens in dry eye.36
Together, these findings demonstrate that local ocular surface tissue hormonal control may be related to circulating blood hormone levels but remains separate from them. Future studies regarding hormonal control may lead to a breakthrough in dry eye management for both women and men.
Regarding some ocular conditions, such as dry eye, cataracts and possibly AMD, female gender is a risk factor. In other cases, there is some evidence of a hormonal link, as was shown with a slight decrease in risk of nuclear cataracts in women taking estrogen-only HRT and the progression of diabetic retinopathy in pregnancy.
In other cases, such as glaucoma and visual impairment, the existing data is inconclusive.
As studies that focus on womens health, such as the Womens Health Initiative, conclude, there will be a significant increase in the volume of publications addressing womens health issuesincluding the effect of hormone replacement therapy on macular degeneration, cataract, diabetic retinopathy and dry eye syndrome.
As this new information becomes available, some of the current questions that researchers are grappling with will be answered, while other questions will emerge. More importantly, the answers will be translated into improved quality of care, improved health care, and hopefully, improved quality of life for women.
Dr. Nichols is an associate professor at the Ohio State University College of Optometry, where she studies dry eye in postmenopausal women.
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