Is low dose of estrogen beneficial for prevention of glaucoma?

Postmenopausal Hormone Therapy Was Associated With Later Age of Onset Among Glaucoma Cases

Purpose

Hormonal therapy (HT) has been suggested to lower the risk of developing glaucoma. Our goal was to investigate the association between HT use and the onset of glaucoma diagnosis in postmenopausal women.

Methods

This retrospective case-only study included female veterans with open-angle glaucoma from VA records between 2000 to 2019. Propensity score matching was used to match HT (n = 1926) users to untreated (n = 1026) women on multiple covariates (e.g., age of menopause, BMI, blood pressure, antihypertensive medications, and a co-morbidity index). A simple linear regression was used to evaluate the impact of HT duration on the age of glaucoma diagnosis, and multivariate linear regression analysis was used to determine which factors contributed to the age at diagnosis of glaucoma.

Results

We found a linear relationship between the age at diagnosis of glaucoma and menopause in women with (r = 0.54) and without HT (r = 0.57) use. HT users tended to have a later diagnosis of glaucoma. Our multivariate analysis found that 0-2 years, 2-5 years, and >5 years of HT use were associated with a 2.20 [confidence interval (CI), 1.64, 2.76], 3.74 [CI, 3.02, 4.46], and 4.51 [CI, 3.84, 5.18] years later diagnosis of glaucoma. An interaction (-0.009 [-0.015, -0.003]) was observed between HT duration and age of menopause diagnosis, with the impact of HT decreasing for later menopause ages.

Conclusions

Longer duration of HT use was associated with a later diagnosis of glaucoma in postmenopausal women in this case-only analysis. The impact of HT may be modulated by menopausal age, although further study is needed. The findings support a protective role of estrogen in glaucoma pathogenesis.

The effects of female sex hormones on the human cornea across a woman's life cycle

The cornea is a hormone-responsive tissue that responds to changing levels of female sex hormones. This review focuses on the structural and functional changes in the human cornea associated with the hormonal milestones of menarche, pregnancy, and menopause, as well as consequences stemming from the use of exogenous sex hormones for fertility control and replacement. Articles were identified by searching PubMed without language or region restrictions. The primary outcomes evaluated were changes in central corneal thickness (CCT), intraocular pressure (IOP), and quality of the ocular tear film. The potential impact of hormone-associated changes on the diagnosis and surgical management of common eye diseases, as well as the potential use of sex hormones as therapeutic agents is also considered. Understanding the physiological effects of female sex hormones on the cornea is important because that knowledge can shape the management decisions physicians and women face about ocular health across their life stages.

Evidence for Menopause as a Sex-Specific Risk Factor for Glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide and is characterized by progressive loss of visual function and retinal ganglion cells (RGC). Current epidemiological, clinical, and basic science evidence suggest that estrogen plays a role in the aging of the optic nerve. Menopause, a major biological life event affecting all women, coincides with a decrease in circulating sex hormones, such as estrogen. While 59% of the glaucomatous population are females, sex is not considered a risk factor for developing glaucoma. In this review, we explore whether menopause is a sex-specific risk factor for glaucoma. First, we investigate how menopause is defined as a sex-specific risk factor for other pathologies, including cardiovascular disease, osteoarthritis, and bone health. Next, we discuss clinical evidence that highlights the potential role of menopause in glaucoma. We also highlight preclinical studies that demonstrate larger vision and RGC loss following surgical menopause and how estrogen is protective in models of RGC injury. Lastly, we explore how surgical menopause and estrogen signaling are related to risk factors associated with developing glaucoma (e.g., intraocular pressure, aqueous outflow resistance, and ocular biomechanics). We hypothesize that menopause potentially sets the stage to develop glaucoma and therefore is a sex-specific risk factor for this disease.

Application of estrogen for the treatment of stress urinary incontinence in mice

BACKGROUND

Stress urinary incontinence (SUI) is a pervasive health tissue among women, which seriously affects the quality of life. The etiology of SUI is complex and diverse in women, with past studies having demonstrated that estrogen deficiency plays an important role in pelvic floor muscle atrophy and urethral degeneration. We comprehensively investigated the effects of estrogen in the treatment of SUI in female mice at cellular and animal levels.

METHODS

L929 fibroblasts mechanical injury model was established by four-point bending device, and SUI mouse model was established by vaginal dilation method commonly used to simulate labor injury. After estrogen treatment, the expressions of Collagen I, Collagen III, Elastin, TIMP-1, TIMP-2, MMP-2, and MMP-9 were detected, the leak point pressure (LPP) and abdominal leak point pressure (ALPP) of mice in each group were detected, and both the effect of estrogen on extracellular matrix remodeling of mouse urethra and anterior vaginal wall was observed from the histological level.

RESULTS

The results revealed that an appropriate amount of estrogen can promote the expression of Collagen I, Collagen III, Elastin, TIMP-1, and TIMP-2, decrease the expression of MMP-2 and MMP-9, and maintain the dynamic balance of MMPs/TIMPs at both cellular and animal levels. Meanwhile, we determined that estrogen can increase the LPP and ALPP values of SUI mice. The collagen fibers' content in the mice treated with estrogen was significantly greater than in the control group mice.

CONCLUSIONS

The estrogen may alleviate the symptoms of SUI by reconstituting ECM, thus laying a solid foundation for further exploration of estrogen therapy.

The Role of the Stromal Extracellular Matrix in the Development of Pterygium Pathology: An Update

Pterygium is a benign fibrovascular lesion of the bulbar conjunctiva with frequent involvement of the corneal limbus. Its pathogenesis has been mainly attributed to sun exposure to ultraviolet-B radiation. Obtained evidence has shown that it is a complex and multifactorial process which involves multiple mechanisms such as oxidative stress, dysregulation of cell cycle checkpoints, induction of inflammatory mediators and growth factors, angiogenic stimulation, extracellular matrix (ECM) disorders, and, most likely, viruses and hereditary changes. In this review, we aim to collect all authors’ experiences and our own, with respect to the study of fibroelastic ECM of pterygium. Collagen and elastin are intrinsic indicators of physiological and pathological states. Here, we focus on an in-depth analysis of collagen (types I and III), as well as the main constituents of elastic fibers (tropoelastin (TE), fibrillins (FBNs), and fibulins (FBLNs)) and the enzymes (lysyl oxidases (LOXs)) that carry out their assembly or crosslinking. All the studies established that changes in the fibroelastic ECM occur in pterygium, based on the following facts: An increase in the synthesis and deposition of an immature form of collagen type III, which showed the process of tissue remodeling. An increase in protein levels in most of the constituents necessary for the development of elastic fibers, except FBLN4, whose biological roles are critical in the binding of the enzyme LOX, as well as FBN1 for the development of stable elastin. There was gene overexpression of TE, FBN1, FBLN5, and LOXL1, while the expression of LOX and FBLN2 and -4 remained stable. In conclusion, collagen and elastin, as well as several constituents involved in elastic fiber assembly are overexpressed in human pterygium, thus, supporting the hypothesis that there is dysregulation in the synthesis and crosslinking of the fibroelastic component, constituting an important pathogenetic mechanism for the development of the disease.

In vivo estimation of murine iris stiffness using finite element modeling

The iris plays an important role in certain types of glaucoma, including primary angle-closure glaucoma and pigmentary glaucoma. Iris mechanics are also important in influencing trabecular meshwork deformation in response to intraocular pressure changes in some animal species. Although mice are widely used to study ocular disease, including glaucoma, the in vivo biomechanical properties of the murine iris are unknown. Thus, the primary objective of this study was to estimate murine iris biomechanical stiffness. We used optical coherence tomography (OCT) images of the anterior segment of living mice (n = 13, age = 7.3 ± 3.2 [mean ± SD] months) at sequentially increasing IOP levels, observing IOP-dependent iris deformations. We then used an inverse finite element model to predict iris deformations under the same conditions, estimating iris stiffness by maximizing agreement between OCT data and numerical simulations. Our results show an in vivo murine iris stiffness of 96.1 ± 54.7 kPa (mean ± SD), which did not correlate with age but was dependent on gender. Our results further showed strong evidence of reverse pupillary block, with mean posterior chamber pressure remaining at approximately 12 mmHg even as anterior chamber pressure was set to much higher levels. Our approach to monitoring iris stiffness in vivo is applicable to study potential changes of iris stiffness in various pathophysiological conditions and thus has significant potential for clinical care of ocular disease involving iris biomechanics.

Ovariectomy worsens visual function after mild optic nerve crush in rodents

Glaucoma is the leading cause of irreversible blindness worldwide, and women represent roughly 60% of the affected population. Early menopause and estrogen signaling defects are risk factors for glaucoma. Recently, we found that surgical menopause exacerbated visual dysfunction in an ocular hypertension model of glaucoma. Here, we investigated if surgical menopause exacerbated visual dysfunction in a model of direct retinal ganglion cell (RGC) damage via optic nerve crush (ONC). Female Long Evans rats (n = 12) underwent ovariectomy (OVX) to induce surgical menopause or Sham surgery. Eight weeks post-surgery, baseline visual function was assessed via optomotor response. Afterwards, rats underwent monocular ONC. Visual function was assessed at 4, 8, and 12 weeks post-ONC. At 12 weeks, retinal function via electroretinography and retinal nerve fiber layer (RNFL) thickness via optical coherence tomography were measured. Visual acuity was reduced after ONC (p < 0.001), with surgical menopausal animals having 31.7% lower visual acuity than Sham animals at 12 weeks (p = 0.01). RNFL thinning (p < 0.0001) and decreased RGC function (p = 0.0016) occurred at 12 weeks in ONC groups. Surgical menopause worsens visual acuity after direct RGC damage using an ONC model. This demonstrates that surgical menopause plays a role in visual function after injury.

In vivo estimation of optic nerve sheath stiffness using noninvasive MRI measurements and finite element modeling

The optic nerve sheath (ONS) is biomechanically important. It is acted on by tension due to ocular movements, and by fluid shifts and/or alterations in intracranial pressure (ICP) in human disease, specifically in pathologies leading to intracranial hypertension. It has also been hypothesized that the ONS is acted on by altered ICP in astronauts exposed chronically to microgravity. However, a non-invasive method to quantify ONS biomechanical properties is not presently available; knowledge of such properties is desirable to allow characterization of the biomechanical forces exerted on the optic nerve head and other ocular structures due to the ONS. Thus, the primary objective of this study was to characterize the biomechanical properties (stiffness) of the human ONS in vivo as a necessary step towards investigating the role of ICP in various conditions, including Spaceflight Associated Neuro-ocular Syndrome (SANS). We acquired non-invasive magnetic resonance imaging (MRI) scans of ostensibly healthy subjects (n = 18, age = 30.4 ± 11.6 [mean ± SD] years) during supine and 15-degree head-down-tilt (HDT) postures, and extracted ONS contours from these scans. We then used finite element modeling to quantify ONS expansion due to postural changes and an inverse approach to estimate ONS stiffness. Using this non-invasive procedure, we estimated an in vivo ONS stiffness of 39.2 ± 21.9 kPa (mean ± SD), although a small subset of individuals had very stiff ONS that precluded accurate estimates of their stiffness values. ONS stiffness was not correlated with age and was higher in males than females.

Eye diseases in women

Although eye diseases are considered to be relatively less affected by patient sex, it is noteworthy that the presence of hormone receptors have been confirmed in various ocular tissues, which were considered to have few sex-based differences. Female hormone levels are known to change because of menstruation, pregnancy, and menopause. When female hormone levels markedly fluctuate in such situations, the disease state may change.The fluctuations in the levels of sex hormones affect the corneal thickness conditions of uveitis.Estrogen may be a possible therapeutic option for glaucoma because it protects the eyes from damage caused by glaucoma and reduces intraocular pressure;it is particularly promising in the treatment of postmenopausal women with glaucoma.Estrogen is considered to have a prophylactic effect against eye diseases. However, there is a report that female sex is an independent risk factor for the progression of diabetic retinopathy, so it may not always exert a prophylactic effect. Thus, caution should be exercised.Based on recent progression of studies on this field, the importance of treatment according to gender has been recognized in the treatment of eye diseases.

Impact of aromatase absence on murine intraocular pressure and retinal ganglion cells

We hypothesize that aromatase, an enzyme that regulates estrogen production, plays a significant role in the control of intraocular pressure (IOP) and retinal ganglion cells (RGCs). To begin to test our hypothesis, we examined the impact of aromatase absence, which completely eliminates estrogen synthesis, in male and female mice. Studies were performed with adult, age-matched wild type (WT) and aromatase knockout (ArKO) mice. IOP was measured in a masked fashion in both eyes of conscious mice at 12 and 24 weeks of age. Retinas were obtained and processed for RGC counting with a confocal microscope. IOP levels in both 12- and 24-week old female ArKO mice were significantly higher than those of age- and sex-matched WT controls. The mean increase in IOP was 7.9% in the 12-week-, and 19.7% in the 24-week-old mice, respectively. These changes were accompanied by significant 9% and 7% decreases in RGC numbers in the ArKO female mice, relative to controls, at 12- and 24-weeks, respectively. In contrast, aromatase deficiency did not lead to an increased IOP in male mice. There was a significant reduction in RGC counts in the 12-, but not 24-, week-old male ArKO mice, as compared to their age- and sex-matched WT controls. Overall, our findings show that aromatase inhibition in females is associated with elevated IOP and reduced RGC counts.

Quantification of the efficacy of collagen cross-linking agents to induce stiffening of rat sclera

The concept of scleral stiffening therapies has emerged as a novel theoretical approach for treating the ocular disorders glaucoma and myopia. Deformation of specific regions of the posterior eye is innately involved in the pathophysiology of these diseases, and thus targeted scleral stiffening could resist these changes and slow or prevent progression of these diseases. Here, we present the first systematic screen and direct comparison of the stiffening effect of small molecule collagen cross-linking agents in the posterior globe, namely using glyceraldehyde, genipin and methylglyoxal (also called pyruvaldehyde). To establish a dose-response relationship, we used inflation testing to simulate the effects of increasing intraocular pressure in freshly harvested rat eyes stiffened with multiple concentrations of each agent. We used digital image correlation to compute the mechanical strain in the tissue as a metric of stiffness, using a novel treatment paradigm for screening relative stiffening by incubating half of each eye in cross-linker and using the opposite half as an internal control. We identified the doses necessary to increase stiffness by approximately 100%, namely 30 mM for glyceraldehyde, 1 mM for genipin and 7 mM for methylglyoxal, and we also identified the range of stiffening it was possible to achieve with such agents. Such findings will inform development of in vivo studies of scleral stiffening to treat glaucoma and myopia.

Characterizing the "POAGome": A bioinformatics-driven approach to primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a genetically, physiologically, and phenotypically complex neurodegenerative disorder. This study addressed the expanding collection of genes associated with POAG, referred to as the "POAGome." We used bioinformatics tools to perform an extensive, systematic literature search and compiled 542 genes with confirmed associations with POAG and its related phenotypes (normal tension glaucoma, ocular hypertension, juvenile open-angle glaucoma, and primary congenital glaucoma). The genes were classified according to their associated ocular tissues and phenotypes, and functional annotation and pathway analyses were subsequently performed. Our study reveals that no single molecular pathway can encompass the pathophysiology of POAG. The analyses suggested that inflammation and senescence may play pivotal roles in both the development and perpetuation of the retinal ganglion cell degeneration seen in POAG. The TGF-β signaling pathway was repeatedly implicated in our analyses, suggesting that it may be an important contributor to the manifestation of POAG in the anterior and posterior segments of the globe. We propose a molecular model of POAG revolving around TGF-β signaling, which incorporates the roles of inflammation and senescence in this disease. Finally, we highlight emerging molecular therapies that show promise for treating POAG.

Corneal hysteresis in patients with glaucoma-like optic discs, ocular hypertension and glaucoma

Background

To compare corneal hysteresis (CH) measurements between patients with glaucoma, ocular hypertension (OHT) and glaucoma-like optic discs (GLD)- defined as a cup to disc ratio greater than or equal to 0.6 with normal intraocular pressure (IOP) and visual fields. The secondary aim was to investigate whether corneal resistance factor (CRF) and central corneal thickness (CCT) differ between patient groups.

Methods

In this cross sectional study a total of 123 patients (one eye each) were recruited from a glaucoma outpatient department to undergo ocular response analyser (ORA) testing and ultrasound pachymetry as well as clinical examination. A One-way Analysis of Covariance (ANCOVA) was conducted to evaluate the mean difference in CH between the three diagnostic groups (glaucoma, OHT and GLD) correcting for potential confounding factors, IOP and age. Analysis was repeated for CRF and CCT.

Results

There was a significant difference in mean CH across the three diagnosis groups; F(2, 115) = 96.95; p < 0.001. Mean CH significantly higher for GLD compared to glaucoma (mean difference 1.83, p < 0.001), and significantly higher for OHT compared to glaucoma (mean difference 2.35, p < 0.001). Mean CH was slightly lower in patients with GLD than those with OHT but this difference was not statistically significant. A similar pattern was seen when the analysis was repeated for CRF and CCT.

Conclusions

Higher CH in GLD and OHT compared to glaucoma suggests increased viscoelasticity of ocular tissues may have a protective role against glaucoma.

Assessment of polygenic effects links primary open-angle glaucoma and age-related macular degeneration

Primary open-angle glaucoma (POAG) and age-related macular degeneration (AMD) are leading causes of irreversible blindness. Several loci have been mapped using genome-wide association studies. Until very recently, there was no recognized overlap in the genetic contribution to AMD and POAG. At genome-wide significance level, only ABCA1 harbors associations to both diseases. Here, we investigated the genetic architecture of POAG and AMD using genome-wide array data. We estimated the heritability for POAG (h²_g = 0.42 ± 0.09) and AMD (h²_g = 0.71 ± 0.08). Removing known loci for POAG and AMD decreased the h²_g estimates to 0.36 and 0.24, respectively. There was evidence for a positive genetic correlation between POAG and AMD (r_g = 0.47 ± 0.25) which remained after removing known loci (r_g = 0.64 ± 0.31). We also found that the genetic correlation between sexes for POAG was likely to be less than 1 (r_g = 0.33 ± 0.24), suggesting that differences of prevalence among genders may be partly due to heritable factors.

Oestrogen, ocular function and low-level vision: a review

Over the past 10 years, a literature has emerged concerning the sex steroid hormone oestrogen and its role in human vision. Herein, we review evidence that oestrogen (oestradiol) levels may significantly affect ocular function and low-level vision, particularly in older females. In doing so, we have examined a number of vision-related disorders including dry eye, cataract, increased intraocular pressure, glaucoma, age-related macular degeneration and Leber's hereditary optic neuropathy. In each case, we have found oestrogen, or lack thereof, to have a role. We have also included discussion of how oestrogen-related pharmacological treatments for menopause and breast cancer can impact the pathology of the eye and a number of psychophysical aspects of vision. Finally, we have reviewed oestrogen's pharmacology and suggest potential mechanisms underlying its beneficial effects, with particular emphasis on anti-apoptotic and vascular effects.

Female reproductive factors and major eye diseases in Asian women -the Singapore Malay Eye Study

PURPOSE

To examine the association of reproductive factors and major eye diseases, including glaucoma, age-related macular degeneration (AMD), diabetic retinopathy and cataract, in Asian women.

METHODS

The Singapore Malay Eye Study is a population-based cross-sectional epidemiological study which examined 3280 persons (78.7% response) of Malay ethnicity aged 40-80 years; 1704 were female. Information on reproductive factors and use of hormone replacement therapy (HRT) was collected using an interviewer-administered questionnaire. Glaucoma was defined according to the International Society for Geographical and Epidemiological Ophthalmology criteria. Retinal photographs were graded for AMD following the Wisconsin grading system, and diabetic retinopathy according to the modified Airlie House classification system. Cataract was graded according to the Lens Opacity Classification System III.

RESULTS

A total of 1176 women reported having experienced menopause by the time of the study with 1073 (91%) having a natural menopause, 88 (7.5%) a hysterectomy and 9 (0.8%) due to other reasons; HRT was used by 70 (6%) women. Women whose age at menopause was ≤52 years were 3.5 times more likely to have glaucoma (95% confidence interval, CI, 1.23-9.98, p value = 0.02) than those whose age at menopause was ≥53 years. Age of menopause was not associated with AMD (age-adjusted odds ratio, OR, 1.22, 95% CI 0.65-2.31), diabetic retinopathy (age-adjusted OR 1.01, 95% CI 0.66-1.54) or cataract (age-adjusted OR 1.38, 95% CI 0.95-2.00). Use of HRT was not associated with any of these eye diseases.

CONCLUSION

Women who had menopause at a younger age were more likely to have glaucoma. This association needs to be confirmed in other studies.

17β-estradiol eye drops protect the retinal ganglion cell layer and preserve visual function in an in vivo model of glaucoma

Neuroprotection in glaucoma as a curative strategy complementary to current therapies to lower intraocular pressure (IOP) is highly desirable. This study was designed to investigate neuroprotection by 17β-estradiol (E2) to prevent retinal ganglion cell (RGC) death in a glaucoma model of surgically elevated IOP in rats. We found that daily treatment with E2-containing eye drops resulted in significant E2 concentration in the retina with concomitant profound neuroprotective therapeutic benefits, even in the presence of continually elevated IOP. The number of apoptotic cells in the RGC layer was significantly decreased in the E2-treated group, when compared to the vehicle-treated controls. Deterioration in visual acuity in these animals was also markedly prevented. Using mass spectrometry-based proteomics, beneficial changes in the expression of several proteins implicated in the maintenance of retinal health were also found in the retina of E2-treated animals. On the other hand, systemic side effects could not be avoided with the eye drops, as confirmed by the measured high circulating estrogen levels and through the assessment of the uterus representing a typical hormone-sensitive peripheral organ. Collectively, the demonstrated significant neuroprotective effect of topical E2 in the selected animal model of glaucoma provides a clear rationale for further studies aiming at targeting E2 into the eye while avoiding systemic E2 exposure to diminish undesirable off-target side effects.