Glaucoma risk factor assessment and prevention: lessons from coronary heart disease

The Degrees of Coronary Heart Disease and the Degrees of New-Onset Blepharitis: A Nationwide Cohort Study

In this study, we aimed to evaluate the association between the severity of coronary heart disease (CHD) and the subsequent severity of blepharitis. This retrospective population-based cohort study was conducted using the National Health Insurance Research Database (NHIRD) of Taiwan. The participants with a CHD diagnosis were divided into mild CHD and severe CHD groups at a 1:2 ratio, according to whether percutaneous coronary intervention (PCI) was performed. The main outcomes were the development of blepharitis and severe blepharitis with the application of antibiotics. Cox proportional hazard regression was performed to obtain the adjusted hazard ratio (aHR) for blepharitis, with a 95% confidence interval (CI) between the groups. There were 22,161 and 15,369 blepharitis events plus 9597 and 4500 severe blepharitis episodes in the mild and severe CHD groups, respectively. The severe CHD group showed a significantly higher incidence of blepharitis development (aHR, 1.275; 95% CI: 1.051-1.912, p = 0.0285), whereas the incidence of severe blepharitis was not significantly different between the groups (aHR, 0.981; 95% CI: 0.945-1.020, p = 0.3453). The cumulative probability of blepharitis was significantly higher in the severe CHD group than in the mild CHD group (p < 0.001). In the subgroup analyses, the correlation between severe CHD and blepharitis was more significant in patients older than 70 years compared to the younger group (p = 0.0115). In conclusion, severe CHD is associated with a higher incidence of blepharitis than mild CHD, and this correlation is more prominent in individuals older than 70 years.

Metabolic syndrome as a risk factor for high intraocular pressure: the Korea National Health and Nutrition Examination Survey 2008-2010

BACKGROUND

High intraocular pressure (IOP) is well established as the most significant risk factor for both the development and progression of primary open-angle glaucoma. Elevated IOP is more frequently seen in the presence of metabolic disturbances that are associated with the components of metabolic syndrome (MetS). The aim of this study was to investigate the association between ocular hypertension and MetS.

PATIENTS AND METHODS

We examined the relationship between ocular hypertension and MetS in 17,160 Korean adults without glaucoma aged >19 years (7,368 men and 9,792 women) who participated in the 2008-2010 Korea National Health and Nutrition Examination Survey. Multivariate logistic regression analysis was used to assess the relationship between MetS and ocular hypertension, after adjusting for age, body mass index, smoking, alcohol consumption, and regular exercise.

RESULTS

The prevalence of MetS was 35.1% among males and 30.1% among females. The prevalence of ocular hypertension was 1.3% among males with MetS and 0.7% among females with MetS. Participants with MetS had a significantly higher IOP than those without MetS (P≤0.001), and each component of MetS had a different effect on the IOP. Hypertension was the strongest predictor of an elevated IOP. In multivariate regression analysis, ocular hypertension was significantly associated with MetS (P=0.027 for men; P=0.015 for women).

CONCLUSION

There is a statistically significant relationship between MetS and ocular hypertension.

Carbohydrate ingestion induces differential autonomic dysregulation in normal-tension glaucoma and primary open angle glaucoma

Background

It is reported that glaucoma may be associated with vascular dysregulation. Normal tension glaucoma (NTG) and primary open angle glaucoma (POAG), which feature different intraocular pressure levels, may manifest differential features of systemic autonomic dysregulation.

Methods and results

We investigated autonomic regulation to carbohydrate ingestion and postural change in 37 glaucoma patients (19 NTG and 18 POAG) and 36 controls. Subjects were age and gender-matched, normotensive, and had normal comparable insulin sensitivity. Continuous finger arterial pressure and ECG was recorded in supine and standing positions before and after carbohydrate ingestion. Low frequency (LF, 0.04–0.15Hz) and high frequency (HF, 0.15–0.4Hz) spectral power of heart rate and systolic blood pressure variability (HRV and SBPV) were calculated to estimate sympathovagal function. Overall comparison glaucoma (N = 37) and controls (N = 36) showed an increased sympathetic excitation, vagal withdrawal and unstable mean arterial pressure after carbohydrate ingestion in glaucoma patients. Glaucoma severity by retinal nerve fibre layer (RNFL) thickness is positively correlated to autonomic responses (HRV LF power and HF power in normalised units (nu), and HRV LF/HF ratio) after carbohydrate ingestion. Early (30 minutes) following carbohydrate ingestion, SBP LF power and HRV parameters remained unchanged in controls; while POAG showed abnormal autonomic responses, with a paradoxical vagal enhancement (increased HRV HF power in nu) and sympathetic inhibition (decreased HRV LF power nu and HRV LF/HF ratio), and associated hypotension. Later (60–120 minutes) following carbohydrate ingestion, HRV parameters remained unaltered in controls; whereas NTG manifested vagal withdrawal (reduced HRV HF power nu) and sympathetic hyper-responsiveness (increased HRV LF power nu and HRV LF/HF ratio), despite increased SBP LF power in both controls and NTG. Both NTG and POAG exhibited attenuated autonomic responses to postural stress.

Conclusions

NTG and POAG both manifest some systemic autonomic cardiovascular dysregulation. However, the two forms of glaucoma respond differentially to carbohydrate ingestion, irrespective of insulin resistance.

Changes in thickness of central macula and retinal nerve fibre layer in severe hypertensive retinopathy: a 1-year longitudinal study

OBJECTIVE

To analyse the longitudinal changes in the thickness of the central macula and retinal nerve fibre layer (RNFL) in patients with hypertensive retinopathy (HTNR) using spectral-domain optical coherence tomography (SD-OCT).

METHODS

This was a prospective cohort study. We studied 18 eyes of patients with HTNR of grade IV who had been followed up for more than 1 year, and 36 normal eyes (without any relevant medical history; the control group). Antihypertensive treatment successfully normalized the blood pressure of HTNR patients. The RNFL thickness and that of the central macula of HTNR patients were measured using a Cirrus HD-OCT instrument, and compared with those of the control group.

RESULTS

At 12 months of follow-up, the mean thickness of the RNFL and central macula was significantly lower in the HTNR group than in the control group (the RNFL was measured first, and then the central macular thickness (CMT): 77.4 ± 9.1 and 233.8 ± 30.8 μm versus 94.1 ± 7.8 and 256.3 ± 28.1 μm, respectively; p < 0.05). With time, the RNFL thickness and CMT became significantly less than that at the initial diagnosis (p < 0.05).

CONCLUSION

Severe HTNR causes a decrease in the thickness of the RNFL and central macula over time. Therefore, the impact of retinal changes associated with systemic diseases such as hypertension should be considered in analysing the thicknesses of the RNFL and central macula in ocular disorders, including retina, glaucoma and neuro-ophthalmologic diseases.

Metabolic syndrome: a risk factor for high intraocular pressure in the Israeli population

AIM

To evaluate the association among elevated intraocular pressure (IOP), the metabolic syndrome (MetS), body mass index (BMI), and some of their components in the Israeli population.

METHODS

We retrospectively reviewed the charts of 12 747 soldiers of the Israeli Defense Forces, aged 35y or older, who underwent a routine periodical medical examination between 1991 and 2004. None of the subjects received medical treatment for either glaucoma or ocular hypertension. High IOP (>21 mm Hg) was correlated with age, sex, arterial blood pressure, total blood cholesterol levels, triglyceride levels, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, smoking, BMI and MetS.

RESULTS

A statistically significant difference was found between the IOP of subjects with a low risk and higher risk for the development of MetS (P<0.0001 for males, P=0.0026 for females). A statistically significant positive correlation was found in male subjects between high BMI and elevated IOP (r=0.11677, P<0.0001).

CONCLUSION

MetS and BMI were significantly more prevalent in subjects with increased IOP levels. We suggest that both should be taken into consideration in the assessment of glaucoma suspects.

External validation of the OHTS-EGPS model for predicting the 5-year risk of open-angle glaucoma in ocular hypertensives

AIMS

To independently evaluate and compare the performance of the Ocular Hypertension Treatment Study-European Glaucoma Prevention Study (OHTS-EGPS) prediction equation for estimating the 5-year risk of open-angle glaucoma (OAG) in four cohorts of adults with ocular hypertension.

METHODS

Data from two randomised controlled trials and two observational studies were analysed individually to assess transferability of the prediction equation between different geographical locations and settings. To make best use of the data and to avoid bias, missing predictor values were imputed using multivariate imputation by chained equations. Using the OHTS-EGPS risk prediction equation, predicted risk was calculated for each patient in each cohort. We used the c-index, calibration plot and calibration slope to evaluate predictive ability of the equation.

RESULTS

Analyses were based on 393, 298, 188 and 159 patients for the Rotterdam, Moorfields, Dunfermline, and Nottingham cohorts, respectively. The discriminative ability was good, with c-indices between 0.69 and 0.83. In calibration analyses, the risk of OAG was generally overestimated, although for the Rotterdam cohort the calibration slope was close to 1 (1.09, 95% CI 0.72 to 1.46), the ideal value when there is perfect agreement between predicted and observed risks.

CONCLUSIONS

The OHTS-EGPS risk prediction equation has predictive utility, but further validation in a population-based setting is needed.

Dietary ω-3 deficiency and IOP insult are additive risk factors for ganglion cell dysfunction

AIM

Dietary deficiencies in ω-3 polyunsaturated fatty acids are known to effect retinal function including retinal ganglion cell (RGC) activity, which may have implications for glaucoma. In this study we consider retinal function after dietary manipulation and intraocular pressure (IOP) stress designed to compromise RGCs.

METHODS

Sprague-Dawley dams were fed either ω-3 sufficient (ω-3, n=15) or deficient (ω-3, n=16) diets 5 weeks before conception with pups subsequently weaned onto their mothers diets. At 20 weeks of age, acute IOP elevation was induced repeatedly through anterior chamber cannulation to 70 mm Hg for 1 hour on 3 separate occasions separated by 1 week. Electroretinograms were recorded 1 week after each IOP elevation to assay the photoreceptors (PIII), ON-bipolar cells (PII), and ganglion/amacrine cells (STR).

RESULTS

Repeat IOP insult results in a specific RGC dysfunction (pSTR -14.5%, P<0.035) as does ω-3 deficiency (-26.4%, P<0.01). However, the combination of both causes an even larger RGC functional loss (-40.1%, P<0.001) than does either diet or IOP insult in isolation (P<0.001).

CONCLUSIONS

Both ω-3 deficiency and repeat acute IOP insult cause RGC dysfunction and the combination of these factors results in a cumulative effect. Our data indicate that sufficient dietary ω-3 improves RGC function making it less susceptible to IOP insult.

Correlation between optical coherence tomography results and the Scoring Tool for Assessing Risk (STAR) score in patients with ocular hypertension

PURPOSE

To correlate retinal nerve fiber layer thickness (RNFL) and optic nerve head (ONH) parameters measured with optical coherence tomography (OCT) with the Scoring Tool for Assessing Risk (STAR) threshold in patients with ocular hypertension (OH).

METHODS

The study included 92 patients with OH. They were divided into low-risk (n=32), moderate-risk (n=36), and high-risk (n=24) groups according to STAR criteria. RNFL and ONH OCT protocols were used to evaluate all study participants. Major parameters for RNFL analysis were average RNFL thickness, superior quadrant, nasal quadrant, inferior quadrant, temporal quadrant, and segmental thickness per 12 o'clock hour position. ONH parameters were vertical integrated rim area (VIRA), horizontal integrated rim width (HIRW), disc diameter, disc area, cup area, rim area, cup-to-disc (C/D) area ratio, horizontal C/D ratio, and vertical C/D ratio.

RESULTS

The highest area under receiver operating characteristics curves for distinguishing the high-risk group from the other groups were vertical C/D ratio (0.88), C/D area (0.88), VIRA (0.87), and HIRW (0.81) for ONH parameters, and inferior (0.82) and 6 o'clock hour position (0.77) for peripapillary RNFL thickness measurements.

CONCLUSIONS

Inferior average, 6 o'clock hour position analyses for RNFL measurement, and VIRA, HIRW, C/D area, and vertical C/D ratio for ONH measurement were the best parameters for STAR staging in patients with OH.

Intraocular Pressure: Does it Measure Up?

The relationship between intraocular pressure (IOP) and glaucoma is complex and not fully understood. We question the validity of several claims relating to the IOP-glaucoma relationship: (1) that 12 mm Hg is an important target in IOP control; (2) that IOP variability is an important risk factor for glaucoma progression; and (3) that every millimeter of mercury of IOP lowering reduces the risk of glaucoma progression by some specific percentage amount. Further, IOP is generally accepted to be an important - if not most important - risk factor for glaucoma development and progression. Using measures of treatment effect - absolute risk reduction, relative risk, and relative risk reduction - we compare the strength of IOP as a risk factor to the strength of a cardiac risk factor in cardiovascular disease.

Evolving global risk assessment of ocular hypertension to glaucoma

PURPOSE OF REVIEW

To discuss current knowledge of global risk assessment in ocular hypertension.

RECENT FINDINGS

The ophthalmologist treating patients with ocular hypertension is frequently faced with the clinical dilemma of which patients to treat and how vigorous treatment should be. The goal of risk assessment for glaucoma is to identify patients at greatest risk for symptomatic vision loss. Risk factors can be identified by history such as age, race, and family history or can be clinically observed by examination such as elevated intraocular pressure, optic nerve head appearance, central corneal thickness, and visual field abnormalities. Risk assessment is a well accepted tool in other fields of medicine. Parallels can be drawn between the evolution of risk assessment for coronary artery disease and glaucoma. Validated risk calculators for ocular hypertension are currently available mostly derived from the Ocular Hypertension Treatment Study.

SUMMARY

The aim of assessing global risk for conversion from ocular hypertension to glaucoma is to identify patients who are most likely to benefit from early treatment. Calculation of risk should be accompanied by thorough analysis of risks, benefits, and alternatives for the individual patient.

Considerations in developing model-based economic evaluations of glaucoma treatment

PURPOSE

To facilitate future glaucoma model development and to provide guidance for decision-makers evaluating them, we provide an overview of an innovative glaucoma model and highlight important modeling considerations.

CONSIDERATIONS

The considerations that were addressed include: disease outcome that is both relevant and meaningful to current clinical practice; diversity in treatment options and practices; incorporation of therapy discontinuation; and consideration of the variability in patient response to treatment.

MODEL SCOPE

A state-transition, Monte Carlo simulation model was developed to simulate the management and treatment of patients with glaucoma and/or ocular hypertension. The model examines strategies involving sequential use of up to 6 pharmacologic interventions. Transitions are based on the monthly probability that a patient is no longer "successfully maintained" on therapy, which can be a consequence of lack of intraocular pressure control, adverse events, lack of compliance, or lack of persistence. Outputs of the model include months on each treatment, frequency of therapy switches, days of intraocular pressure control, frequency of ophthalmologist visits, frequency of surgery, and glaucoma-related costs. The model allows the user to specify country-specific treatment strategies, survival on therapy, surgical rates, practice patterns, and costs.

CONCEPT APPLICATION

The model presented offers insights into accommodating patient and clinician variability through the use of persistence distributions. It will facilitate future glaucoma model development and provide insight for decision-makers who must evaluate model-based analyses of the economic value of glaucoma interventions.

Glaucoma Medications

As with many diseases, glaucoma increases in frequency in older populations, and is very often encountered in patients taking multiple medications. While the exact mechanism of glaucomatous optic neuropathy (GON) is not known, intraocular pressure (IOP) is thought to be central to the process, and reducing IOP is the only known effective treatment. The newer definition of glaucoma is an IOP-sensitive optic neuropathy. While large, controlled studies have indicated that reducing IOP will slow the progression of disease, the contributions of other conditions and medications have not been adequately studied. As the adverse effect profiles of medical therapies for glaucoma have improved, use of these agents has increased greatly. This has resulted in a large number of older patients taking glaucoma medications. Since topical medications can easily be overlooked in a medical history, and are for the most part well tolerated, systemic complications from these agents can be missed. In addition to being a common disease requiring treatment, glaucoma is also a model system for other degenerative diseases, and many of the concepts originally developed in relation to neurodegenerative diseases such as Alzheimer's disease are under investigation for glaucoma. These include approaches targeted towards neuroprotection and excitotoxicity.

Risk assessment in the management of patients with ocular hypertension

PURPOSE

To develop a model for estimating the global risk of disease progression in patients with ocular hypertension and to calculate the "number-needed-to-treat" (NNT) to prevent progression to blindness as an aid to practitioners in clinical decision making.

DESIGN

Development of a mathematical model for estimating risk of glaucoma progression.

METHODS

Population-based studies of patients with ocular hypertension and glaucoma were reviewed by a panel of glaucoma specialists. Measures of disease progression risks derived from three long-term studies and assumptions based on the available data were used to estimate the risk of progression from ocular hypertension to glaucoma and glaucoma to unilateral blindness for untreated and treated patients over a 15-year period. Using these estimates, the NNT (1/absolute risk reduction on treatment) to prevent unilateral blindness in one patient with ocular hypertension was calculated.

RESULTS

In untreated patients, the estimated risk of progression from ocular hypertension to unilateral blindness was 1.5% to 10.5% and in treated patients, the estimated risk of progression was 0.3% to 2.4% over 15 years. From these estimates, between 12 and 83 patients with ocular hypertension will require treatment to prevent one patient from progressing to unilateral blindness over a 15-year period.

CONCLUSION

Global risk assessment that incorporates all available data plays a vital role in managing patients with ocular hypertension. A more precise understanding of long-term vision loss should be factored into decisions pertaining to the initiation of glaucoma therapy. Undoubtedly, these estimates will evolve and change with the availability of new population-based epidemiologic information and improvements in multivariable model testing.