Approximately 38% of postmenopausal women in the United States used hormone replacement therapy by 2002. While US Food and Drug Administration-approved indications for hormone therapy include relief of menopausal symptoms and prevention of osteoporosis, long-term use has been in vogue to prevent a range of chronic conditions, especially heart disease.
The Women's Health Initiative (WHI) was a major trial studying Hormone Replacement Therapy (HRT). The trial was stopped in July 2002 because women receiving combination estrogen & progesterone had an increased risk of invasive breast cancer and overall the treatment was causing more harm than good. In practical terms the increased risk translates like this: In 10,000 women taking the drug for a year, there will be 7 more coronary heart disease events, 8 more invasive breast cancers, 8 more strokes, and 8 more pulmonary emboli, but 6 fewer colorectal cancers and 5 fewer hip fractures.
So the current recommendation is to not to prescribe combination estrogen/progesterone HRT. The other portion of the HRT trial, which used estrogen alone in women who have had hysterectomies with was not stopped, so it is reasonable to assume that to date, estrogen alone HRT in these women may be safe. Estrogen alone was the dominant hormone until the increased risk of endometrial cancer led to the addition of progesterone for women with an intact uterus.

On this page we highlight the affect of HRT on the aging eye. Given what we now know from the HRT trial, there probably is no circumstance where HRT will be considered solely for aging eye related diseases. This review would primarily interest those women who have made a informed choice to be on HRT and wish to learn more about its other affects.
HRT seems to help in cataract, glaucoma and macular degeneration but may increase dry eye symptoms.

Hormone Replacement Therapy (HRT) & Aging Eye Diseases

HRT & Cataract
Longer duration of reproductive period i.e. longer exposure to endogenous estrogen and/or use of estrogen replacement after menopause may delay or reduce the severity of cortical and nuclear lens opacities in women. The evidence for reducing posterior subcapsular opacities is weaker.

  ● Current users of HRT aged 65 years or older have a lower prevalence of cortical cataract.
  ● Early age at menarche is associated with a lower prevalence of all three cataract types.
  ● Older age at menopause is associated with a lower prevalence of cortical cataract.
  ● Use of oral contraceptives is associated with a lower prevalence of cortical cataract.

Possible Mechanism of Action:
There is evidence that receptors of estrogen are present in human lens epithelial cells. This suggests a possible mechanism for a direct estrogen effect on the lens. Estrogen inhibits TGF-beta ( Transforming growth factor -beta) TGF-beta has been shown to induce cataract. Several estrogens have also been shown to have significant antioxidant properties and therefore it may protect against free radical damage (like carotenoids, vitamin C etc).
References:
Blue Mountain Eye Study (Am J Epidemiol 2002;155:997-1006, Am J Epidemiol 1997;145:242-9).
Beaver Dam Eye Study (Arch Ophthalmol 1994;112:85-91, Trans Am Ophthalmol Soc 1993;91:517-44).

HRT & Dry Eyes
A study published in the Journal of American Medical Association reported that women who use HRT, particularly estrogen alone, are at increased risk of dry eye syndrome (JAMA 2001;286:2114-9). The odds of having dry eyes were 70% more if postmenopausal women used HRT. Each 3-year increase in the duration of HRT use was associated with a 15% increase in risk of having dry eyes.
In this study 3 questions were used to diagnose dry eye syndrome: 1). How often do your eyes feel dry (not wet enough)? 2). How often do your eyes feel irritated? and 3). Have you ever been diagnosed by a clinician as having dry eye syndrome? Interestingly questions 1 and 2 alone are claimed to have a sensitivity of 60% coupled with a specificity of 94% compared with clinical diagnosis of dry eye syndrome, and to provide nearly the same predictability as a 14-item questionnaire.

There are other published studies wherein the findings seem to be at odds with the findings of this study (Maturitas 2003;44:63-8, J Assoc Acad Minor Phys 2000;11:44-9). Perhaps this is because these other studies relied on dry eye tests and eye examination and not on symptoms alone, so the information they analyzed was different. It is clear that we do not, as of yet, know fully the interplay between the various sex hormones and ocular surface health (Cornea 1998;17:353-8, Ann N Y Acad Sci 2002;966:223-5).

AgingEye Times Position:
Given what we know so far, it seems reasonable to conclude that women taking HRT have a greater likelihood of having irritated, uncomfortable eyes. The strongest evidence linking dry eyes with HRT is based on an epidemiological study which was not primarily designed to explore this association. We do not know the biological basis of the increase in eye discomfort with HRT. It could well be that the eye is 'dryer', but other possible explanations need to be explored too.

HRT & Glaucoma
There are very few studies which have explored the question of HRT effect on glaucoma. One study found that HRT reduces eye pressure by 8 to 13% in menopausal women after about 12 weeks of HRT (Maturitas 1997;28:55-8). Supporting a role for the beneficial effect of female sex hormones is the finding that early menopause is associated with a higher risk of open-angle glaucoma, especially true if women went through menopause before reaching the age of 45 years (Am J Epidemiol 2001;154:138-44). This finding comes from the widely regarded Rotterdam Study.
The relation between primary open-angle glaucoma and gender is still controversial. In the Baltimore Eye Survey (JAMA 1991;266:369-74), the Beaver Dam Eye Study (Ophthalmology 1992;99:1499-504), and the Blue Mountains Eye Study (Ophthalmology 1996;103:1661-9), no significant difference was found between prevalence of primary open-angle glaucoma in men and women. However, in the Framingham Eye Study (Am J Epidemiol 1977;106:17-32), the Barbados Eye Study (Arch Ophthalmol 1994;112:821-9), and the Rotterdam Study (Invest Ophthalmol Vis Sci 2000;41:3309-21), up to a twofold higher prevalence was found in men. If it is true that glaucoma occurs more often in men, then it makes sense to assume that female sex hormones have a possible protective effect on glaucoma.

HRT & Macular Degeneration
The preponderance of evidence to date suggests that HRT may be beneficial in postmenopausal women who have macular degeneration.
Use of postmenopausal estrogen therapy appears to reduce the odds of advanced macular degeneration among postmenopausal women who have macular degeneration. Women who had used postmenopausal estrogen therapy have 54% lower odds of advanced macular degeneration compared with nonusers (Am J Ophthalmol 2002;134:842-8) Older age at menarche tends to be associated with advanced macular degeneration, which may imply a reduced exposure to estrogen. The significant decrease in early macular degeneration with increasing years from menarche to menopause also supports the concept that a shorter duration of estrogen production may increase risk of macular degeneration (Aust N Z J Ophthalmol 1997;25:S13-S15).
The Eye Disease Case-Control Study evaluated a range of possible risk factors for women, including estrogen use, oral contraceptive use, history of hysterectomy, and parity. A large protective effect was found for women who formerly or currently used HRT, and an increased risk was found for women who had one or more children (Arch Ophthalmol 1992;110:1701-1708). The Beaver Dam Eye Study found that increasing number of years of HRT use was associated with reduced maculopathy, albeit weakly (Trans Am Ophthalmol Soc 1994;92:289-95). More recent data from the Beaver Dam Eye Study did not support this association (Am J Ophthalmol 2000;130:322-6). Findings from the Rotterdam Study suggested that early menopause due to surgical removal of the ovaries increased the risk of macular degeneration which could be due to an early decline in estrogen production (BMJ 1995;310:1570-1).