Associations with intraocular pressure in the Barbados Eye Study

Higher intraocular pressure is associated with leukoaraiosis among middle-aged and elderly Koreans without glaucoma or dementia

AIM

Leukoaraiosis and high intraocular pressure are strongly associated with cardiovascular disease, vascular angiopathy, and geriatric syndrome. Until now, little is known about the relationship between intraocular pressure and leukoaraiosis in its preclinical stage. The aim of this study was to evaluate the association between intraocular pressure and leukoaraiosis among middle-aged and elderly Koreans without glaucoma or dementia.

METHODS

We examined the relationship of intraocular pressure with leukoaraiosis at a preclinical stage in 753 Korean adults (474 men, 279 women; mean age 57.8 ± 6.6 years). A multiple logistic regression analysis was performed in order to determine whether intraocular pressure is an independent determinant for leukoaraiosis.

RESULTS

The overall prevalence of leukoaraiosis was 7.3%. Mean ocular pressure (±SD) was significantly higher in the leukoaraiosis group than the control group (14.3 ± 2.9 and 13.5 ± 2.9, respectively; P=0.028). In multiple logistic regression analysis, the odds ratio for leukoaraiosis was 1.18 (95% confidence interval: 1.06-1.31) for each 1 mm Hg increase in intraocular pressure.

CONCLUSION

Intraocular pressure was found to be independently and positively associated with leukoaraiosis. This finding indicates that higher intraocular pressure may be a useful additional measure in assessing the risk of leukoaraiosis in the clinical setting.

Association of smoking with intraocular pressure in middle-aged and older Japanese residents

OBJECTIVES

To clarify whether smoking was associated with elevated intraocular pressure (IOP) and to evaluate the interrelationship among IOP, blood viscosity, and smoking.

METHODS

This cross-sectional study analyzed health examination data obtained between 2001 and 2004 from 1113 individuals (829 men and 284 women), ranging in age from 28 to 79 years, who had not undergone any ocular surgery or medical treatment for hypertension, ocular hypertension, and glaucoma.

RESULTS

Multiple-regression analysis showed that systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), and number of cigarettes smoked per day had a significantly positive association with IOP in men (P < 0.05). In women also, SBP, DBP, and BMI were positively related to IOP (P < 0.05). On the contrary, age had a significant negative association with IOP in both sexes (P < 0.01). Analysis of covariance and multiple logistic regression analyses showed that the adjusted mean IOP and the multivariate odds ratios for IOP increased with increasing cigarette consumption in men (P for trend = 0.01 and 0.06, respectively). Analysis of covariance found that smoking was significantly associated with both high IOP and high hematocrit in men (P for trend <0.05); however, the adjusted mean IOP values were higher in smokers than in nonsmokers, regardless of the hematocrit level.

CONCLUSIONS

The results of this study suggested that the IOP level may be substantially affected by smoking habit in middle-aged and older Japanese men.

Postmenopausal intraocular pressure changes in South Indian females

BACKGROUND

Normal Intraocular pressure (IOP) is an essential prerequisite for the eye to serve its function as a light gathering and transducer organ. Various physiological factors which include age, gender and hormonal variations may influence IOP in normal subjects and these effects sometimes may be marked and relatively sustained. The present study was an attempt which was made to observe the effect of menopause on IOP and the contribution of altered Body Mass Index (BMI).

METHODOLOGY

A total of 120 females who were in the age group of 40 - 55 years, who were recruited for the study, were divided into two groups of 60 each: premenopausal and postmenopausal, based on their menstrual history. The BMI of the subjects was then calculated. IOP was recorded in all individuals and it was compared between the two groups by using Student's 't' test. The IOP was also correlated with BMI. A p value of < 0.05 was considered as statistically significant.

RESULTS

The results of the present study showed that there was a significant increase in the IOP in the postmenopausal group as compared to that in premenopausal women. Moreover, it showed a significant positive correlation with BMI in post menopausal women.

CONCLUSION

The higher IOP in postmenopausal women could be ascribed to dwindling levels of oestrogen and progesterone after menopause, which could act by altering any/several components of the IOP regulating mechanisms. A large body size, as was indicated by BMI, was associated with additional increases in IOP. The present study, therefore, provides further insights into the interactions between BMI and paucity of sex hormones in influencing the IOP.

Distribution of intraocular pressure and its association with ocular features and cardiovascular risk factors: the Gutenberg Health Study

PURPOSE

To describe the distribution of intraocular pressure (IOP) and its association with ocular features and cardiovascular risk factors in an adult European cohort.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

This analysis was based on a Gutenberg Health Study (GHS) cohort that included 4335 eligible enrollees from among 5000 subjects who participated in the survey from 2007 through 2008. The age range was 35 to 74 years at enrollment.

METHODS

Participants underwent a standardized protocol with a comprehensive questionnaire; ophthalmic examination including slit-lamp biomicroscopy, noncontact tonometry, fundus photography, central corneal thickness measurement, and visual field testing; and a thorough general examination focused on cardiovascular parameters, psychological evaluation, and laboratory tests, including genetic analysis.

MAIN OUTCOME MEASURES

Mean and reference interval of IOP stratified by age, gender, and eye.

RESULTS

Mean ± standard deviation (SD) IOP was 14.0 ± 2.6 mmHg in both eyes, 13.9 ± 2.7 mmHg in right eyes, and 14.0 ± 2.7 mmHg in left eyes. Mean ± SD IOP in men (n = 2216) and in women (n = 2119) was 14.1 ± 2.7 mmHg and 13.9 ± 2.5 mmHg with an intersex difference (P = 0.009). Positive univariate associations with higher IOP were detected for brown iris color, central corneal thickness, hypertension, diabetes, smoking, obesity, dyslipidemia, body mass index, weight, hip size (women only), waist circumference, and waist-to-hip ratio. Multivariate testing revealed male gender, central corneal thickness, brown iris color, hypertension, smoking, and waist-to-hip ratio to be correlated with higher IOP. In women, age correlated negatively with IOP in the multivariate analysis.

CONCLUSIONS

Intraocular pressure distribution in this cohort yielded a lower mean IOP than in similar white study populations. Increasing age in women correlated with lower IOP. Association analyses with several systemic characteristics revealed that cardiovascular risk factors correlated with higher IOP.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Intraocular pressure and its relationship to ocular and systemic factors in a healthy Chinese rural population: the Handan Eye Study

PURPOSE

To describe the distribution of and factors related to intraocular pressure (IOP) in a healthy adult rural Chinese population in northern China.

METHODS

The Handan Eye Study is a cross-sectional, population-based study of eye diseases among 6,830 (90.4% response rate) rural Chinese persons aged 30+ years. Participants underwent an interviewer-administered questionnaire and a complete ocular examination, including standardized measurement of IOP with Perkins applanation tonometry.

RESULTS

After excluding persons with glaucoma, or those with diseases that have a marked effect on IOP or that preclude accurate IOP measurement, 6,101 persons were included in the current analysis. Mean IOP (mean ± standard deviation) of the study population was 15.0 ± 2.8 mmHg. Men had lower IOP than women (14.6 ± 2.8 mmHg versus 15.4 ± 2.7 mmHg, t = -8.37, P < 0.001). In the multivariate analysis younger age, female sex, presence of diabetes mellitus, higher blood pressure, higher body mass index, thicker central cornea and higher myopia were associated with higher IOP.

CONCLUSIONS

Mean IOP among persons living in rural northern China was similar to that recently reported in southern China. IOP appeared to be lower with increasing age in Chinese subjects, which contrasts with results in white populations.

Complications of intravitreal triamcinolone acetonide for macular edema and predictive factors for intraocular pressure elevation

AIM

To investigate the complications of intravitreal triamcinolone acetonide (IVTA) for the treatment of macular edema, and to determine the risk factors for intraocular pressure (IOP) elevation.

METHODS

Charts of patients with macular edema secondary to branch retinal vein occlusion (BRVO), diabetic retinopathy and uveitis who had received IVTA injections were reviewed to document its complications. IOP elevation was defined as a pressure of ≥24mmHg at some point during follow-up. Multivariate logistic regression analysis was performed to characterize baseline risk factors for this elevation.

RESULTS

The study included 111 eyes of 65 female and 46 male patients with a mean follow-up of (11.6±5.1) months. Of the 111 eyes, 52 (46.8%) had macular edema secondary to BRVO, 44 (39.6%) had clinically significant diabetic macular edema (CSDME) and 15 (13.5%) had non-infectious uveitis with macular edema. IOP was recorded ≥ 24mmHg in 38 eyes (34.2%) during the follow-up. Higher baseline IOP (P=0.022), younger age (P=0.003), and male gender (P=0.014) were significant risk factors for IOP elevation after IVTA injection. Eyes with prior vitrectomy were less likely to have IOP elevation (P=0.054). Two eyes (5.2% of eyes with increased IOP) underwent trabeculectomy, and 9 eyes (16.3% of the phakic eyes) necessitated cataract surgery. Other complications included branch vein occlusion (1.8%), sterile endophthalmitis (0.9%) and pseudohypopyon (0.9%).

CONCLUSION

IVTA has side effects with IOP elevation and cataract formation being the two most common. A subset of patients is more prone to developing increased IOP following IVTA, namely, younger male patients with higher baseline IOP.

Effects of body mass index on intraocular pressure and ocular pulse amplitude

AIM

To investigate the effects of body mass index (BMI) on intraocular pressure (IOP) and ocular pulse amplitude (OPA).

METHODS

Totally 140 healthy individuals without any systemic diseases were included in the study. BMI (kg/m(2)) was calculated for every individual. IOP and OPA were measured with Pascal Dynamic contour tonometer (DCT). Blood pressure was also measured along with the DCT. The patients were divided into three groups according to BMI as: Group1, BMI<25; Group2, 25≤BMI<30; Group3, BMI≥30. Mean values of IOP, OPA, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were used in statistical analysis.

RESULTS

In Group1, the means of IOP, OPA, were 16.8±2.3mmHg, 2.7±0.7mmHg respectively; and SBP, DBP were 120.0±6.1mmHg, and 77.4±5.6mmHg respectively. In group2, the mean IOP, OPA, SBP, and DBP were found to be 16.6±2.1mmHg, 2.4±0.7mmHg, 121.7±5.3mmHg, and 79.5±4.9mmHg respectively. In group3, the mean IOP, OPA, SBP, and DBP were found to be 17.3±1.7mmHg, 2.1±0.7mmHg, 122.4±5.7mmHg, and 79.7±5.2mmHg respectively. There were no statistically significant difference between groups in terms of IOP, SBP and DBP, while OPA values were significantly lower in group3 (P=0.001).

CONCLUSION

Decreased OPA values in individuals with higher BMI may indicate that subjects with higher BMI have lower choroidal perfusion and lower ocular blood flow.

Observations on degenerative changes within the optic nerve in patients with primary open glaucoma and arterial hypertension: 6-month follow-up

The authors aimed to determine the effect of the time of hypotensive drug administration on the progress of degenerative changes within the optic nerve in patients with hypertension and glaucoma. Two groups were included in the study: group A comprised patients-dippers taking drugs in the mornings, and group B comprised patients-nondippers taking drugs both in the mornings and in the evenings. After 6 months, group B showed significant drops in nocturnal diastolic blood pressure (BP) (month 1=73.27 mm Hg vs month 6=67.50 mm Hg), nocturnal mean BP (89.34 vs 84.65 mm Hg), and minimum diastolic BP (50.74 vs 44.03 mm Hg). Group B also showed significant reductions in nocturnal ocular perfusion pressure (43.0 vs 39.73), retinal nerve fiber layer thickness (131.31 vs 113.12 μm), and flow in the eye vessels. Taking hypotensive drugs in the evening may significantly decrease blood flow in the eye arteries, cause degenerative changes within the optic nerves, and result in greater loss in the field of vision.

Intraocular pressure in Japanese diabetic patients

Background

To determine whether the intraocular pressure (IOP) in diabetic patients is significantly different from that in nondiabetic patients.

Methods

The medical records of all patients who were initially examined in the Department of Ophthalmology, Kansai Medical University, Takii Hospital were reviewed. At the initial examination, patients had a detailed interview and underwent a comprehensive ophthalmic examinations. All patients were over 20 years of age and did not have glaucoma.

Results

A total of 703 patients were evaluated. The mean (±standard error) IOP of the diabetic patients was 15.5 ± 0.2 mmHg (n = 206), and was significantly higher than the 14.0 ± 0.1 mmHg (n = 497) in the nondiabetic patients (P < 0.0001). The IOP was negatively correlated with age (r = −0.202; P = 0.024) in the diabetic patients and was weakly but significantly correlated with the glycosylated hemoglobin (HbA_1c) level (r = 0.240; P = 0.015) in the group with diabetic retinopathy.

Conclusion

The significantly higher IOP in diabetic patients and positive correlation of IOP with HbA_1c levels in patients with diabetic retinopathy indicate that IOP in diabetic patients is higher, especially in those with poor control of diabetes.

Body mass index has a linear relationship with cerebrospinal fluid pressure

PURPOSE

To examine the relationship between body mass index (BMI) and cerebrospinal fluid pressure (CSFP), as low BMI and low CSFP have recently been described as risk factors for primary open-angle glaucoma (POAG).

METHODS

This was a retrospective review of the electronic medical records of patients who had CSFP measured by lumbar puncture and data to calculate BMI at the Mayo Clinic (Rochester, MN). Exclusion criteria included diagnoses, surgical procedures and medications known to affect CSFP. Mean CSFP for each unit BMI was calculated. The probabilities were two-tailed, and the α level was set at P < 0.05. Patients with documented BMI, CSFP, and intraocular pressure (IOP) were analyzed for the relationship between IOP and BMI.

RESULTS

A total of 4235 patients, primarily of Caucasian descent, met the entry criteria. Median BMI was 26 and the mean CSFP was 10.9 ± 2.6 mm Hg. The increase in CSFP with increasing BMI was linear with an r(2) = 0.20 (P < 0.001). CSFP increased by 37.7% from BMI 18 (8.6 ± 2.1 mm Hg) to BMI 39 (14.1 ± 2.5 mm Hg). The r(2) (0.21) of the model of BMI and sex was similar to the r(2) of a BMI-only model (0.20). There was no relation between IOP and BMI within a subgroup of the study population (r (2) = 0.005; P = 0.14).

CONCLUSIONS

CSFP has a positive, linear relationship with BMI. IOP is not influenced by BMI. If CSFP influences the risk for POAG, then individuals with a lower BMI may have an increased risk for developing POAG. Similarly, a higher BMI may be protective.

Intraocular pressure and its determinants in subjects with type 2 diabetes mellitus in India

Objectives

This study was conducted to show the intraocular pressure (IOP) distribution and the factors affecting IOP in subjects with type 2 diabetes mellitus (DM) in India.

Methods

We measured the anthropometric and biochemical parameters for confirmed type 2 DM patients. A comprehensive ocular examination was performed for 1377 subjects aged > 40 years and residing in Chennai.

Results

A significant difference in IOP (mean ± standard deviation) was found between men and women (14.6±2.9 and 15.0±2.8 mmHg, p = 0.005). A significantly elevated IOP was observed among smokers, subjects with systemic hypertension and women with clinically significant macular edema (CSME). After a univariate analysis, factors associated significantly with higher IOP were elevated systolic blood pressure, elevated resting pulse rate and thicker central corneal thickness (CCT). In women, elevated glycosylated hemoglobin was associated with a higher IOP. After adjusting for all variables, the elevated resting pulse rate and CCT were found to be associated with a higher IOP.

Conclusions

Systemic hypertension, smoking, pulse rate and CCT were associated with elevated intraocular pressure in type 2 DM. Women with type 2 DM, especially those with CSME, were more prone to have an elevated IOP.

Age- and gender-specific association between intraocular pressure and metabolic variables in a Taiwanese population

BACKGROUND

To analyze the relationship between intraocular pressure, metabolic variables, and components of metabolic syndrome in different age and gender groups.

METHODS

We examined 10,491 Taiwanese adults aged 21 to 79 years and categorized according to gender and age. All participants underwent examinations, including body mass index (BMI), waist circumference, blood pressure, intraocular pressure, and blood chemistry. Multiple linear regression analyses were performed to evaluate the relationships between intraocular pressure and these variables as well as to determine the relative influence of each component of metabolic syndrome.

RESULTS

Intraocular pressure showed a significant reduction with aging in men but not in women. BMI had a positive association with intraocular pressure in young adults and middle-aged men. Systolic blood pressure was positively associated with intraocular pressure in most groups, whereas diastolic blood pressure was positively associated with intraocular pressure only in middle-aged and elderly men. Fasting blood sugar levels showed a significant association with high intraocular pressure in middle-aged and elderly adults. All participants with metabolic syndrome had higher intraocular pressure levels, and each component of metabolic syndrome had a distinct effect on the intraocular pressure, with blood pressure being the strongest predictor.

CONCLUSION

Elevated intraocular pressure is associated with a number of metabolic variables, and each component of metabolic syndrome has a distinct impact on the intraocular pressure in individual age- and gender-specific groups. The present results may allow internal medicine specialists to manage metabolic risk factors while considering possible ocular involvement and potential treatment interactions.

24-hour IOP telemetry in the nonhuman primate: implant system performance and initial characterization of IOP at multiple timescales

PURPOSE

IOP is the most common independent risk factor for development and progression of glaucoma, but very little is known about IOP dynamics. Continuous IOP telemetry was used in three nonhuman primates to characterize IOP dynamics at multiple time scales for multiple 24-hour periods.

METHODS

An existing implantable telemetric pressure transducer system was adapted to monitoring anterior chamber IOP. The system records 500 IOP, ECG, and body temperature measurements per second and compensates for barometric pressure in real time. The continuous IOP signal was digitally filtered for noise and dropout and reported using time-window averaging for 19, 18, and 4 24-hour periods in three animals, respectively. Those data were analyzed for a nycthemeral pattern within each animal.

RESULTS

Ten-minute time-window averaging for multiple 24-hour periods showed that IOP fluctuated from 7 to 14 mm Hg during the day, and those changes occurred frequently and quickly. Two-hour time-window averages of IOP for multiple 24-hour periods in three animals showed a weak nycthemeral trend, but IOP was not repeatable from day-to-day within animals.

CONCLUSIONS

The measured IOP was successfully measured continuously by using a new, fully implantable IOP telemetry system. IOP fluctuates as much as 10 mm Hg from day to day and hour to hour in unrestrained nonhuman primates, which indicates that snapshot IOP measurements may be inadequate to capture the true dynamic character of IOP. The distributions, magnitudes, and patterns of IOP are not reproducible from day to day within animals, but IOP tends to be slightly higher at night when IOP data are averaged across multiple 24-hour periods within animals.

Intraocular pressure, central corneal thickness, and glaucoma in chinese adults: the liwan eye study

PURPOSE

To describe the distribution of central corneal thickness (CCT), intraocular pressure (IOP), and their determinants and association with glaucoma in Chinese adults.

DESIGN

Population-based cross-sectional study.

METHODS

Chinese adults aged 50 years and older were identified using cluster random sampling in Liwan District, Guangzhou. CCT (both optical [OCCT] and ultrasound [UCCT]), intraocular pressure (by Tonopen, IOP), refractive error (by autorefractor, RE), radius of corneal curvature (RCC), axial length (AL), and body mass index (BMI) were measured, and history of hypertension and diabetes (DM) was collected by questionnaire. Right eye data were analyzed.

RESULTS

The mean values of OCCT, UCCT, and IOP were 512 ± 29.0 μm, 542 ± 31.4 μm, and 15.2 ± 3.1 mm Hg, respectively. In multiple regression models, CCT declined with age (P < .001) and increased with greater RCC (P < .001) and DM (P = .037). IOP was positively associated with greater CCT (P < .001), BMI (P < .001), and hypertension (P < .001). All 25 persons with open-angle glaucoma had IOP <21 mm Hg. CCT did not differ significantly between persons with and without open- or closed-angle glaucoma. Among 65 persons with ocular hypertension (IOP >97.5th percentile), CCT (555 ± 29 μm) was significantly (P = .01) higher than for normal persons.

CONCLUSIONS

The distributions of CCT and IOP in this study are similar to that for other Chinese populations, though IOP was lower than for European populations, possibly due to lower BMI and blood pressure. Glaucoma with IOP <21 mm Hg is common in this population. We found no association between glaucoma and CCT, though power (0.3) for this analysis was low.

The relationship between components of metabolic syndrome and open-angle glaucoma

PURPOSE

To determine whether an association exists between various components of metabolic syndrome (diabetes mellitus [DM], systemic arterial hypertension [HTN], hyperlipidemia, and obesity) and open-angle glaucoma (OAG) in a large, diverse group of individuals throughout the United States.

DESIGN

Longitudinal cohort study.

PARTICIPANTS

All beneficiaries aged ≥40 years continuously enrolled in a managed care network who had 1 or more visits to an eye care provider during 2001 to 2007 were identified.

METHODS

Billing codes were used to identify individuals with OAG and those with components of metabolic syndrome. Cox regression was used to determine the hazard of developing OAG in enrollees with individual components or combinations of components of metabolic syndrome, with adjustment for sociodemographic factors, systemic medical conditions, and other ocular diseases.

MAIN OUTCOME MEASURES

Hazard of developing OAG.

RESULTS

Of the 2 182 315 enrollees who met the inclusion criteria, 55090 (2.5%) had OAG. After adjustment for confounding factors, those with DM (hazard ratio [HR] = 1.35 [95% confidence interval [CI], 1.21-1.50]) or HTN (HR = 1.17 [95% CI, 1.13-1.22]) alone or in combination (HR = 1.48 [95% CI, 1.39-1.58]) had an increased hazard of developing OAG relative to persons with neither of these conditions. By contrast, persons with hyperlipidemia alone had a 5% decreased hazard of OAG (HR = 0.95 [95% CI, 0.91-0.98]). Comorbid hyperlipidemia attenuated the increased hazard between HTN (HR = 1.09 [95% CI, 1.05-1.12]) or DM (HR = 1.13 [95% CI, 1.05-1.21]) and OAG.

CONCLUSIONS

At a time when the prevalence of metabolic disorders in the United States, is increasing this study furthers our understanding of risk factors associated with OAG and helps identify persons who may be at increased risk for this condition.

[Characterization of the biometric eye profile of a high myopic population: does high myopia correspond to a homogenous phenotype?]

PURPOSE

High myopia is a public health problem because of its high prevalence and is a major cause of blindness. The physiopathology of myopia remains unknown and mechanisms causing the disease are most probably complex, combining acquired environmental and genetic factors. The most recent data suggest that genetic determinisms of high myopia could be highly dependent on subject phenotype. The aim of this study was to analyse the ocular components of a high myopic population to verify whether high myopia corresponds to a homogeneous phenotype.

PATIENTS AND METHODS

We analysed the biometric characteristics of 718 myopic eyes with a spherical equivalent of less than -5 diopters. The biometric parameters (corneal radius, axial length, and intraocular pressure) were compared controlling for sex and the degree of myopia.

RESULTS

We found a difference between the phenotype of males and females. For men, axial length was the only determinant of the myopic phenotype, whereas for women, the myopic phenotype was determined by axial length and corneal radius. This difference between the phenotypes was more evident for myopia with a spherical equivalent greater than -10 diopters (moderate myopia). This difference between males and females disappeared in myopia less than -15 diopters.

CONCLUSION

There are intersex differences considering the high myopia phenotype at a spherical equivalent less than -5 diopters. However, this difference disappears for extremely high myopia with a spherical equivalence of less than -15 diopters.

Intraocular pressure and related systemic and ocular biometric factors in a population-based study in Japan: the Kumejima study

PURPOSE

To examine the distribution of intraocular pressure (IOP) and its related systemic and ocular biometric factors in a population-based study in a southwestern island of Japan.

DESIGN

Cross-sectional, population-based study.

METHODS

All residents of Kumejima Island, Japan, located in southwestern Japan (eastern longitude, 126 degrees 48 minutes and northern latitude 26 degrees 20 minutes), 40 years of age and older were asked to undergo a comprehensive questionnaire and ocular examination, including measurement of IOP with Goldmann applanation tonometry.

RESULTS

Of the 4632 eligible residents, 3762 (81.2%) underwent the examination. In 2838 non-glaucomatous subjects from whom reliable measurements of IOP were obtained, the mean IOPs +/- standard deviation in all, men, and women were 15.1 +/- 3.1 mm Hg (n = 2838), 15.2 +/- 3.1 mm Hg (n = 1450), and 15.1 +/- 3.0 mm Hg (n = 1388), respectively, with no significant intersex difference (P = .63). Multivariate regression analysis demonstrated that higher IOP was significantly correlated with younger age (P < .001), higher body mass index (P < .001), higher systolic blood pressure (P < .001), history of diabetes mellitus (P = .001), thicker central corneal thickness (P < .001), steeper corneal curvature (P < .001), and longer axial length (P < .018), but not with anterior chamber depth and the Shaffer angle width grade.

CONCLUSIONS

Younger age, higher body mass index, higher systolic blood pressure, diabetes, thicker central corneal thickness, and steeper corneal curvature were significantly correlated with higher IOP. The present results confirm that IOP is associated with systemic and ocular biometric factors and may define specific subgroups most likely to have an elevated IOP.

Anthropometric measures and their relation to incident primary open-angle glaucoma

PURPOSE

To assess the relation between anthropometric measures and incident primary open-angle glaucoma (POAG).

DESIGN

Prospective cohort study.

PARTICIPANTS

Included were 78,777 women in the Nurses' Health Study and 41,352 men in the Health Professionals Follow-up Study.

METHODS

Females and male health professionals were followed prospectively from 1980 through 2004 and 1986 through 2004, respectively. Eligible participants were 40 years of age or older, did not have POAG at baseline, and reported undergoing eye examinations during follow-up. Information regarding anthropometric measures, potential confounders, and ophthalmic status was updated using biennial questionnaires. During follow-up, 980 POAG cases were identified.

MAIN OUTCOME MEASURES

Multivariate rate ratios (MVRR) of POAG and their 95% confidence intervals (CIs).

RESULTS

There was no significant relation between cumulatively averaged body mass index (BMI) in kilograms per meter squared and POAG overall (P = 0.06, for trend). However, in relation to POAG with intraocular pressure (IOP) of 22 mmHg or less at diagnosis, each unit increase in BMI was associated with a 6% reduced risk in women (MVRR, 0.94; 95% CI, 0.91-0.98; P = 0.01), but not for men (MVRR, 1.02; 95% CI, 0.96-1.09; P = 0.57); this gender difference was significant (P = 0.03, for heterogeneity). In multivariate analyses to explore the independent effects of height and weight, weight (as height-adjusted weight residuals; P = 0.002, for trend), but not height (P = 0.10, for trend) seemed to account for most of the inverse association between BMI and POAG with IOP of 21 mmHg or less at diagnosis in women. There was no association between BMI and POAG with IOP of more than 21 mmHg at diagnosis for either gender (P> or =0.26, for trend). Among women, analyses found that the relations between anthropometric parameters and both POAG subtypes (POAG with IOP< or =21 mmHg vs. POAG with IOP >21 mmHg when diagnosed) were significantly different (P< or =0.0001).

CONCLUSIONS

Among women, higher BMI was associated with a lower risk of POAG with IOP of 21 mmHg or less at diagnosis. The factors contributing to this tendency may yield insight into the pathogenesis of POAG.

Comparison of three methods of intraocular pressure measurement and their relation to central corneal thickness

PURPOSE

The purpose of this study was to compare the reliability of the 'gold standard' Goldmann applanation tonometer (GAT), with that of the ocular response analyser (ORA), and the dynamic contour tonometer (DCT).

PATIENTS AND METHODS

A total of 694 subjects were recruited to participate from the TwinsUK (UK Adult Twin Registry) at St Thomas' Hospital, London. Intraocular pressure (IOP) was measured using GAT, ORA, and the DCT. The agreement between the three methods was assessed using the Bland-Altman method. Repeatability coefficients and coefficient of variation between first and second readings of the same eye were used to assess reliability.

RESULTS

Mean age was 57.5 years (SD, 13.1; range, 16.1-88.5). The mean IOPs, calculated using the mean of two readings from the right eye were as follows: Goldmann (GAT), 14.1+/-2.8 mm Hg; IOPg (ORA), 15.9+/-3.2 mm Hg; IOPcc (ORA), 16.6+/-3.2 mm Hg; and DCT, 16.9+/-2.7 mm Hg. The 95% limits of agreement were for ORA (IOPcc): GAT, -2.07 to 7.18 mm Hg; for DCT: GAT, -0.49 to 6.21 mm Hg; and for DCT: ORA (IOPcc), -3.01 to 4.85 mm Hg. Coefficients of variation for the three tonometers were GAT, 8.3%; ORA, 8.2%; DCT, 6.3%. The repeatability coefficients were 3.4 mm Hg for GAT, 3.57 mm Hg for ORA and 3.09 mm Hg for DCT. GAT and ORA (IOPg) readings showed a positive correlation with central corneal thickness (P<0.005).

CONCLUSIONS

This study found similar reliability in all three tonometers. Bland-Altman plots showed the three instruments to have 95% limits of agreement outside the generally accepted limits, which means they are not interchangeable. GAT measurements were found to be significantly lower than the two newer instruments.

Blood pressure, perfusion pressure, and open-angle glaucoma: the Los Angeles Latino Eye Study

PURPOSE

To examine the cross-sectional relationship between blood pressure, perfusion pressure, and prevalence of open angle glaucoma (OAG) in an adult Latino population.

METHODS

Participants aged 40 years and older (N = 6130) from the Los Angeles Latino Eye Study (LALES), a large, population-based study of self-identified adult Latinos, underwent an interviewer-administered questionnaire and a complete ocular and clinical examination. Logistic regression was used to evaluate the covariate-adjusted association of OAG with systolic, diastolic, and mean blood pressures and perfusion pressures. Covariates included age, intraocular pressure, history of glaucoma treatment including medications and surgery, and history of blood pressure and treatment of blood pressure including use of medications.

RESULTS

Low systolic (odds ratio [OR] = 2.5), diastolic (OR = 1.9), and mean (OR = 3.6) perfusion pressures and low diastolic blood pressure (OR = 1.9) were associated with a higher prevalence of OAG in LALES participants. Higher systolic blood pressure and mean arterial blood pressure were associated with a higher prevalence of OAG. There was no relationship between the prevalence of OAG and the presence of a history of cardiovascular disease.

CONCLUSIONS

Low diastolic, systolic and mean perfusion pressures, low diastolic blood pressure, and high systolic and mean arterial blood pressures are associated with a higher prevalence of OAG in adult Latinos.

Scleral biomechanics in the aging monkey eye

PURPOSE

To investigate the age-related differences in the inhomogeneous, anisotropic, nonlinear biomechanical properties of posterior sclera from old (22.9 +/- 5.3 years) and young (1.5 +/- 0.7 years) rhesus monkeys.

METHODS

The posterior scleral shell of each eye was mounted on a custom-built pressurization apparatus, then intraocular pressure (IOP) was elevated from 5 to 45 mm Hg while the 3D displacements of the scleral surface were measured with speckle interferometry. Each scleral shell's geometry was digitally reconstructed from data generated by a 3-D digitizer (topography) and 20-MHz ultrasound (thickness). An inverse finite element (FE) method incorporating a fiber-reinforced constitutive model was used to extract a unique set of biomechanical properties for each eye. Displacements, thickness, stress, strain, tangent modulus, structural stiffness, and preferred collagen fiber orientation were mapped for each posterior sclera.

RESULTS

The model yielded 3-D deformations of posterior sclera that matched well with those observed experimentally. The posterior sclera exhibited inhomogeneous, anisotropic, nonlinear mechanical behavior. The sclera was significantly thinner (P = 0.038) and tangent modulus and structural stiffness were significantly higher in old monkeys (P < 0.0001). On average, scleral collagen fibers were circumferentially oriented around the optic nerve head (ONH). No difference was found in the preferred collagen fiber orientation and fiber concentration factor between age groups.

CONCLUSIONS

Posterior sclera of old monkeys is significantly stiffer than that of young monkeys and is therefore subject to higher stresses but lower strains at all levels of IOP. Age-related stiffening of the sclera may significantly influence ONH biomechanics and potentially contribute to age-related susceptibility to glaucomatous vision loss.

Lifestyle, nutrition, and glaucoma

The only proven strategy to prevent primary open-angle glaucoma (POAG) is the use of ocular hypotensive therapy among people diagnosed with ocular hypertension. In this review, various modifiable lifestyle factors, such as exercise, diet, and cigarette smoking, that may influence intraocular pressure and that have been studied in relation to the risk of developing POAG are discussed. Epidemiologic studies on lifestyle factors are few, and the current evidence suggests that there are no environmental factors that are clearly associated with POAG; however, a few factors merit further study. This review also outlines future directions for research into the primary prevention of POAG.

Ocular perfusion pressure and glaucoma: clinical trial and epidemiologic findings

PURPOSE OF REVIEW

A possible connection between ocular perfusion pressure and open-angle glaucoma (OAG) has been hypothesized. This review summarizes the scientific rationale for the proposed relationship, presents recent data, and outlines potential implications.

RECENT FINDINGS

Population-based epidemiologic studies found strong relationships between low ocular perfusion pressure and OAG prevalence, as well as OAG incidence. Clinical studies report similar associations between low perfusion pressure and OAG progression. These consistent findings suggest that altered blood flow in the optic disc increases both the risk of OAG development and the progression of established OAG. An underlying factor would be impaired vascular autoregulation, which may lead to poor perfusion in OAG. In contrast, there is conflicting evidence on the possible link of glaucoma to blood pressure/hypertension.

SUMMARY

Current evidence supports the role of vascular factors as part of the multifactorial cause of OAG. As ocular perfusion pressure reflects the vascular status at the optic disc, it may be more relevant than systemic blood pressure alone. Although the associations of OAG to perfusion pressure are strong, consistent, and biologically plausible, they require careful interpretation. The evidence implicating a vascular cause in OAG is mounting, but the clinical implications for patient management are still uncertain.

Central corneal thickness and its associations with ocular and systemic factors: the Singapore Malay Eye Study

PURPOSE

To examine the association between central corneal thickness (CCT) and potential systemic and ocular factors affecting CCT in an Asian population.

DESIGN

Population-based cross-sectional study.

METHODS

A total of 3,280 (78.7% response) adults aged 40 to 80 years of Malay ethnicity living in Singapore underwent a standardized interview and ocular and systemic examination at a centralized study clinic. CCT was measured with an ultrasound pachymeter. Blood samples were obtained to determine serum glucose, cholesterol, and triglyceride levels, and urine samples to determine glomerular filtration rate. The presence of diabetes, hypertension, chronic kidney disease (CKD), and metabolic syndrome were defined based on a combination of investigation results and participant's history.

RESULTS

CCT was obtained from 3,239 individuals. CCT was normally distributed with a mean of 541.2 microm in the right eye. While controlling for age and gender, CCT was greater in individuals with higher body mass index (BMI) (P = .038), greater intraocular pressure (IOP) (P < .001), greater axial length (P = .005), and greater radius of corneal curvature (P < .001). Individuals with CKD (P = 0.012) and metabolic syndrome (P < .001) also had greater CCT.

CONCLUSION

CCT is associated with higher IOP, longer axial length, and greater radius of corneal curvature, as well as higher BMI, metabolic syndrome, and CKD.

The singapore 5-Fluorouracil trabeculectomy study: effects on intraocular pressure control and disease progression at 3 years

PURPOSE

To report 3-year results of a randomized, controlled trial comparing the use of a single application of 5-fluorouracil (5-FU) with placebo in trabeculectomy surgery.

DESIGN

Prospective, randomized, double-blinded treatment trial.

PARTICIPANTS

Two hundred forty-three Asian patients with primary open-angle or primary angle-closure glaucoma undergoing primary trabeculectomy.

METHODS

One eye of each patient was randomized to receive either intraoperative 5-FU or normal saline (placebo) during trabeculectomy.

MAIN OUTCOME MEASURES

Primary outcome measure was the level of intraocular pressure (IOP). Secondary outcomes were progression of visual field loss, rates of adverse events, and interventions after surgery.

RESULTS

Of the 288 eligible patients, 243 were enrolled and 228 completed 3 years follow-up; 120 patients received 5-FU and 123 received placebo. Trial failure, according to predefined IOP criteria, was lower in the 5-FU group compared with the placebo group, although the difference was only significant with a failure criterion of IOP >17 mmHg (P = 0.0154). There was no significant difference in progression of optic disc and/or visual field loss over 36 months between 5-FU and placebo (relative risk [RR], 0.67; 95% confidence interval [CI], 0.34-1.31; P = 0.239). Uveitis occurred more often in the 5-FU-treated group (14/115 [12%] vs 5/120 [4%]; P = 0.032).

CONCLUSIONS

This is the first masked, prospective, randomized trial reporting the effect of adjunctive 5-FU in trabeculectomy surgery in an East Asian population. The trial shows that an increased success rate can be achieved for several years after a single intraoperative treatment with 5-FU. We conclude that 5-FU is relatively safe and can be routinely used in low-risk East Asian patients.

FINANCIAL DISCLOSURE(S)

The authors have no proprietary or commercial interest in any materials discussed in this article.

Cigarette smoking and primary open angle glaucoma: a systematic review

PURPOSE

To evaluate the epidemiologic evidence for a causal association between tobacco smoking and primary open angle glaucoma (POAG).

METHODS

Systematic review, including quality assessment, of published analytical epidemiologic studies and evaluation of the evidence using established causality criteria (strength, consistency, temporality, dose response, reversibility, and biologic plausibility).

RESULTS

Eleven papers describing 9 case-control studies, 1 prospective cohort study, and a paper describing a pooled analysis based on 2 prospective cohort studies were included in the review. The methodologic quality of most included studies was poor. The strongest studies methodologically were the cohort studies on which the pooled analysis was based. Neither the prospective cohort study (rate ratio not reported) nor the pooled analysis of 2 prospective cohort studies (adjusted rate ratio 0.9) found an association between smoking and POAG. There was a significant positive association between smoking and POAG in only 2 of the case-control studies (adjusted odds ratio 2.9 and 10.8). There was no evidence of a dose-response relationship with smoking or of reversibility of effect in the studies where this was assessed.

CONCLUSIONS

This systematic review provided little evidence for a causal association between smoking and development of POAG. Given the limited evidence from high quality studies, and the possibility that flaws in many of the studies reviewed biased the results toward the null, further high quality research to confirm our conclusions is needed. However, it remains important to warn ophthalmic patients of the dangers of smoking and provide cessation support owing to the clear evidence of links between smoking and other ocular and systemic diseases.

Intracranial pressure in primary open angle glaucoma, normal tension glaucoma, and ocular hypertension: a case-control study

PURPOSE

To compare intracranial pressure (ICP) in subjects with primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG; subset of POAG), and ocular hypertension (OHT) with that in subjects with no glaucoma.

METHODS

The study was a retrospective review of medical records of 62,468 subjects who had lumbar puncture between 1985 and 2007 at the Mayo Clinic. Of these, 57 POAG subjects, 11 NTG subjects (subset of POAG), 27 OHT subjects, and 105 control subjects met the criteria and were analyzed. A masked comparison of the relationship between ICP and other ocular and nonocular variables was performed by using univariate and multivariate analyses.

RESULTS

ICP was significantly lower in POAG compared with age-matched control subjects with no glaucoma (9.1 +/- 0.77 mm Hg vs. 11.8 +/- 0.71 mm Hg; P < 0.0001). Subjects with NTG also had reduced ICP compared with the control subjects (8.7 +/- 1.16 mm Hg vs. 11.8 +/- 0.71 mm Hg; P < 0.01). ICP was higher in OHT than in age-matched control subjects (12.6 +/- 0.85 mm Hg vs. 10.6 +/- 0.81 mm Hg; P < 0.05).

CONCLUSIONS

ICP is lower in POAG and NTG and elevated in OHT. ICP may play an important role in the development of POAG and NTG and in preventing the progression of OHT to POAG. Further prospective and experimental studies are warranted to determine whether ICP has a fundamental role in the pathogenesis of glaucoma.

Premise and prediction-how optic nerve head biomechanics underlies the susceptibility and clinical behavior of the aged optic nerve head

We propose that age-related alterations in optic nerve head (ONH) biomechanics underlie the clinical behavior and increased susceptibility of the aged ONH to glaucomatous damage. The literature which suggests that the aged ONH is more susceptible to glaucomatous damage at all levels of intraocular pressure is reviewed. The relevant biomechanics of the aged ONH are discussed and a biomechanical explanation for why, on average, the stiffened peripapillary scleral and lamina cribrosa connective tissues of the aged eye should lead to a shallow (senile sclerotic) form of cupping is proposed. A logic for why age-related axon loss and the optic neuropathy of glaucoma in the aged eye may overlap is discussed. Finally, we argue for a need to characterize all forms of clinical cupping into prelaminar and laminar components so as to add precision to the discussion of clinical cupping which does not currently exist. Such characterization may lead to the early detection of ONH axonal and connective tissue pathology in ocular hypertension and eventually aid in the assessment of etiology in all forms of optic neuropathy including those that may be purely age-related.

Associations with intraocular pressure in Latinos: the Los Angeles Latino Eye Study

PURPOSE

To evaluate the association of biologic factors with intraocular pressure (IOP) in a Latino population.

DESIGN

Population-based cross-sectional study.

METHODS

Latinos 40 years and older (n = 5,958) from the Los Angeles Latino Eye Study without a history of ocular hypotensive treatment underwent an interviewer-administered questionnaire and a complete ocular and clinical examination. IOP was obtained by applanation tonometry and was based on the mean of three measurements. Multivariable regression models were used to evaluate the independent association of biological factors with IOP.

RESULTS

Higher systolic blood pressure, higher central corneal thickness, and diabetes mellitus were the major factors associated with elevated IOP. Other positively correlated variables included age, female gender, higher diastolic blood pressure, larger body mass index, darker colored irides, and nuclear sclerosis. Axial length and family history of glaucoma had no association with IOP.

CONCLUSIONS

Several systemic and ocular characteristics are associated with elevated IOP in Latinos. By identifying and recognizing these risk factors, we can define subgroups of the population that may be most at risk of having elevated IOP.

Predicting intraocular pressure change before initiating therapy: timolol versus latanoprost

PURPOSE

To study intraocular pressure (IOP) reductions with timolol and latanoprost reached in clinical practice, taking into account data that are routinely collected by the ophthalmologist; to predict IOP reduction from these variables.

METHODS

A cohort of patients with primary open-angle glaucoma (suspect) or ocular hypertension was recruited from nine Dutch centres. Mean absolute and relative IOP reduction was calculated in order to compare timolol to latanoprost. IOP reduction was calculated by comparing patients with certain characteristics to those who had none.

RESULTS

One hundred and fifty-six persons started on timolol and 76 started on latanoprost monotherapy. Mean [95% confidence interval (CI)] absolute reduction was 7.2 mmHg (7.9; 6.5) for timolol and 6.9 mmHg (8.0; 5.8) for latanoprost. Mean relative reduction (95% CI) was 27.2% (29.3; 25.1) for timolol and 26.6% (30.2; 22.9) for latanoprost. No significant difference in IOP reduction between timolol and latanoprost was found when adjusting for data that are routinely collected by the ophthalmologist. At the time of starting treatment, none of these items normally used for the management of glaucoma, except IOP at baseline, could predict change in IOP.

CONCLUSION

In clinical practice, timolol and latanoprost achieve similar IOP reductions that are comparable to those achieved in randomized trials. No clinically relevant information for glaucoma management can be used to predict IOP reduction accurately.

The association between intraocular pressure and predictors of coronary heart disease risk in Koreans

Elevated intraocular pressure (IOP) is one of the major risk factors for glaucomatous visual field defects. Each individual systemic risk factor of coronary heart disease (CHD) is associated with elevated IOP, although no reports have argued for a correlation between the risk factors for CHD and IOP after a comprehensive or collective analysis. The National Cholesterol Education Program Adult Treatment Panel III presented the Framingham projection, which can predict the risk of CHD quantitatively. We investigated the association between IOP and the Framingham projection in 16,383 Korean subjects. The Framingham projection was applied using the indicated risk factors. The associations between the Framingham projection and IOP and the influences of the risk factors on the IOP were examined. The Framingham projection was correlated with the mean IOP in women (p<0.05). The relationship between IOP and systemic variables other than smoking was significant (p<0.05). The mean IOP was significantly higher in the high-risk CHD group than in the low-risk group based on the Framingham projection (p<0.05). Because an elevated IOP was associated with cardiovascular risk factors, subjects with a high CHD risk based on the Framingham projection need continuous monitoring for IOP to prevent glaucomatous visual field defects.

Factors associated with intraocular pressure before and during 9 years of treatment in the Collaborative Initial Glaucoma Treatment Study

PURPOSE

To evaluate, both at initial glaucoma diagnosis and during treatment, the role of demographic and clinical factors on intraocular pressure (IOP).

DESIGN

Cohort study of patients enrolled in a randomized clinical trial.

PARTICIPANTS

Six hundred seven patients with newly diagnosed open-angle glaucoma (OAG) were enrolled at 14 centers in the United States.

METHODS

After randomization to initial surgery or medications, patients were followed at 6-month intervals. Intraocular pressure was measured by Goldmann applanation tonometry. Predictive factors for IOP at baseline and during follow-up were analyzed using linear mixed models.

MAIN OUTCOME MEASURE

Intraocular pressure at baseline and during follow-up.

RESULTS

The mean baseline IOP was 27.5 mmHg (standard deviation, 5.6 mmHg). Predictive factors for higher baseline IOP included younger age (0.7 mmHg per 10 years), male gender (2.4 mmHg higher than females), pseudoexfoliative glaucoma (5.4 mmHg higher than primary OAG), and pupillary defect (2.2 mmHg higher than those without a defect). During 9 years of follow-up, both surgery and medications dramatically reduced IOP from baseline levels, but the extent of IOP reduction was consistently greater in the surgery group. Over follow-up years 2 through 9, mean IOP was 15.0 versus 17.2 mmHg for surgery versus medicine, respectively. Predictive associations with higher IOP during follow-up included higher baseline IOP (P<0.0001), worse baseline visual field (mean deviation; P<0.0001), and lower level of education (P = 0.0019). Treatment effect was modified by smoking status: nonsmokers treated surgically had lower IOP than smokers treated surgically (14.6 vs. 16.7 mmHg, respectively; P = 0.0013). Clinical center effects were significant (P<0.0001) in both the baseline and follow-up models.

CONCLUSIONS

In this large cohort of newly diagnosed glaucoma patients, predictors of pretreatment IOP and IOP measurements over 9 years of follow-up were identified. Our findings lend credence to the postulate that sociodemographic, economic, compliance, or other environmental influences play a role in IOP control during treatment.

Sociodemographic, family history, and lifestyle risk factors for open-angle glaucoma and ocular hypertension. The Los Angeles Latino Eye Study

PURPOSE

To evaluate the relationship between sociodemographic, family history, and lifestyle risk factors and open-angle glaucoma (OAG) and ocular hypertension (OHT) in Latinos.

DESIGN

Population-based cohort study.

PARTICIPANTS

Latinos 40 years and older from 6 census tracts in La Puente, California.

METHODS

Participants underwent an in-home interview and in-clinic examination. Demographic, lifestyle, and family history variables were analyzed as risk factors using multivariable regression models to identify independent associations with OAG or OHT.

MAIN OUTCOME MEASURES

Open-angle glaucoma and OHT.

RESULTS

Two hundred eighty-nine participants were diagnosed as having OAG, 219 were found to have OHT, and 5624 persons had no evidence of either OAG or OHT. After adjustment for intraocular pressure, stepwise logistic regression analyses revealed that older age, male gender, unmarried marital status, and being a first-degree relative were independent risk factors for OAG. For age, the relative risk doubled with each decade. Males and unmarried participants had a higher risk of having glaucoma than females and those who were married (odds ratio [OR], 1.73; 95% confidence interval [CI], 1.30-2.30, and OR, 1.39; 95% CI, 1.03-1.87, respectively). A positive family history of glaucoma in first-degree relatives was a risk factor for OAG (OR, 1.92; 95% CI, 1.25-2.94). Smoking, alcohol use, and female reproductive hormone use were not associated with OAG. Additionally, increasing age, Native American ancestry, unemployed status, and family history of glaucoma were found to be independent factors for increased risk of OHT.

CONCLUSIONS

Although the mechanisms whereby age and family history lead to increased risk are partly understood, further study is needed to understand the biological significance of the other demographic risk factors identified such as male gender and unmarried status.

Incident open-angle glaucoma and intraocular pressure

PURPOSE

To evaluate the role of baseline intraocular pressure (b-IOP) as a risk factor for incident open-angle glaucoma (OAG) in participants of African origin from the Barbados Eye Studies.

DESIGN

Population-based 9-year cohort study.

PARTICIPANTS

Three thousand two hundred twenty-two persons examined during the study period who were free of glaucoma at baseline and at risk of developing OAG during the 9-year follow-up.

METHODS

Study protocols were standardized and included ophthalmic and other measurements, automated perimetry, applanation tonometry, fundus photography, and comprehensive ophthalmologic examination for those referred. The product-limit approach was used to estimate incidence. Relationships between b-IOP and incidence were evaluated by adjusted relative risk ratios (RRs) with 95% confidence intervals (CIs), based on Cox regression models.

MAIN OUTCOME MEASURE

The 9-year incidence of OAG was based on both visual field and optic disc abnormalities, with ophthalmologic evaluations to exclude other possible causes.

RESULTS

The overall 9-year incidence of OAG was 4.4% (95% CI, 3.7%-5.2%), and the mean (standard deviation) b-IOP among persons at risk was 18.0 mmHg (4.1). Among the 125 incident OAG cases, the mean b-IOP was 21.9 mmHg and 46% had b-IOP of >21 mmHg. In contrast, the nonincident group had a mean b-IOP of 17.8 mmHg and only 12% had b-IOP of >21 mmHg. Overall, OAG risk increased by 12% with each 1-mmHg increase in IOP (RR, 1.12; 95% CI, 1.08-1.16). Incidence steadily increased from 1.8% (95% CI, 1.2%-2.7%) for persons with b-IOP of < or =17 mmHg (referent group) to 22.3% (95% CI, 15.8%-31.1%) for those with b-IOP > 25 mmHg, resulting in an adjusted RR of 13.1 (95% CI, 7.1-24.1) among the latter group. The attributable risk for IOP of >25 mmHg was 19%. Using 21 mmHg as a cutoff, the RR was 7.9 (95% CI, 3.8-16.2) and the attributable risk was 37%.

CONCLUSIONS

After 9 years' follow-up, the risk of OAG was positively related to IOP levels at baseline. Although persons with b-IOP of >25 mmHg had a 13-fold RR of developing OAG, most cases arose with lower b-IOP. This study thus confirms the role of IOP as an influential risk factor, yet at the same time underscores its limitations in predicting OAG.