Association between ocular pressure and certain health parameters

Metabolic Health, Obesity, and Intraocular Pressure

Obesity has been associated with increased intraocular pressure (IOP), but the results are inconsistent. Recently, a subgroup of obese individuals with good metabolic profiles were suggested to have better clinical outcomes than normal-weight individuals with metabolic diseases. The relationships between IOP and different combinations of obesity and metabolic health status have not been investigated. Therefore, we investigated the IOP among groups with different combinations of obesity status and metabolic health status. We examined 20,385 adults aged 19 to 85 years at the Health Promotion Center of Seoul St. Mary's Hospital between May 2015 and April 2016. Individuals were categorized into four groups according to obesity (body mass index (BMI) ≥ 25 kg/m²) and metabolic health status (defined based on prior medical history or abdominal obesity, dyslipidemia, low high-density lipoprotein cholesterol, high blood pressure, or high fasting blood glucose levels upon medical examination). ANOVA and ANCOVA were performed to compare the IOP among the subgroups. The IOP of the metabolically unhealthy obese group (14.38 ± 0.06 mmHg) was the highest, followed by that of the metabolically unhealthy normal-weight group (MUNW, 14.22 ± 0.08 mmHg), then, the metabolically healthy groups (p < 0.001; 13.50 ± 0.05 mmHg and 13.06 ± 0.03 mmHg in the metabolically healthy obese (MHO) and metabolically healthy normal-weight groups, respectively). Subjects who were metabolically unhealthy showed higher IOP compared to their counterparts who were metabolically healthy at all BMI levels, and there was a linear increase in IOP as the number of metabolic disease components increased, but no difference between normal-weight vs. obese individuals. While obesity, metabolic health status, and each component of metabolic disease were associated with higher IOP, those who were MUNW showed higher IOP than those who were MHO, which indicates that metabolic status has a greater impact than obesity on IOP.

The Impact of Systemic Health Parameters on Intraocular Pressure in the Western Region of Saudi Arabia

Background

A normal intraocular pressure (IOP) is essential for maintaining the normal structure and function of the eyes. Furthermore, an elevated IOP is a known risk factor for glaucoma. As the results from studies addressing the relationship between IOP and systemic health parameters are conflicting, researchers have not reached a consensus. This study aimed to evaluate the relationship between IOP and health parameters among non-glaucomatous participants in the western region of Saudi Arabia.

Method

We retrospectively reviewed the medical records of 255 participants aged 20 years and above who had not received any medical treatment for ocular hypertension or glaucoma at King Abdulaziz University Hospital (KAUH), Jeddah, Saudi Arabia, from January 2019 to April 2021. The patients were categorized into age groups, divided by decades (ranging from 20-29 years to 80+ years); the most prevalent age group was 60-69 years. The data were entered using Microsoft Excel 2016 (Microsoft Corporation, Redmond, Washington), and Statistical Package for the Social Sciences (SPSS) software was used for univariate analysis. The relationship between continuous variables was analyzed by the Pearson correlation coefficient. The differences between continuous and categorical variables were assessed by the t-test and one-way analysis of variance (ANOVA) test, respectively.

Results

The mean (standard deviation) IOP in the right and the left eyes was 15.7 mmHg (4.0) and 15.6 mmHg (3.9), respectively. There were no significant associations between IOP and lipid profile parameters (p > 0.05). There was a statistically significant difference in the right IOP, in relation to the age groups (p = 0.006). Moreover, the mean IOP in the left eye was significantly higher among patients with diabetes than in the patients without diabetes (p = 0.007) as well as in patients with hypertension than in the patients without hypertension (p = 0.023).

Conclusion

The effect of total cholesterol, triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), BMI, and sex on IOP could not be established in our study. However, over the past years, people's diets have incorporated higher cholesterol and fat content, leading to higher BMI levels. Therefore, further studies of the association between BMI and IOP are critical to determine if BMI is certainly a significant risk factor for increased IOP and glaucoma.

Variation in intraocular pressure by sex, age, and geographic location in China: A nationwide study of 284,937 adults

OBJECTIVE

To investigate the distribution characteristics of intraocular pressure (IOP) by sex, age, and geographic location in China and to build the corresponding reference intervals (RIs).

MATERIAL AND METHODS

A cross-sectional, multi-centered, population-based study was conducted. All data were collected from participants without eye diseases who underwent ophthalmological examinations in 170 Health Screening Centers in mainland China in 2018. The non-contact tonometer was used to measure IOP. The age-, sex-, and province-specific RIs of IOP were investigated. The IOP of different age-sex groups was further explored by stratifying according to height, body mass index (BMI), blood pressure, altitude, and geographic area.

RESULTS

During the study, a population-based sample of 284,937 participants was included. The distribution of measured IOP followed an approximately Gaussian distribution, with a higher mean value in men than in women. The IOP showed a general trend of decline with age for both men and women and varied across geographical locations. The mean IOP was 15.4 (95% CI: 9.1-21.6) mmHg for men and 14.9 (95% CI: 9.0-20.8) mmHg for women. For men, it decreased from 11.0-23.5 mmHg at age 18-24 years to 10.5-20.5 mmHg at age ≥70 years. For women, it decreased from 10.5-22.0 to mmHg at age 18-24 years to 10.0-21.0 mm Hg at age ≥70 years.

CONCLUSIONS

The IOP varied with age, sex, metabolic disorders and geographic location. These RIs should be considered in the clinical process of glaucoma diagnosis and treatment.

Effect of Blood Pressure Reduction on Intraocular Pressure and Ophthalmic Artery Blood Flow Velocity in Hypertension

Purpose: To evaluate the effect of reducing blood pressure (BP) by atenolol and amlodipine on (1) intraocular pressure (IOP) and (2) ophthalmic artery blood flow (OAF) velocity in new hypertensives. Methods: A prospective, observational cohort study conducted at a tertiary care center in India after IRB approval. New hypertensives treated with atenolol 25 mg or amlodipine 5 mg were divided into 2 groups of 30 patients each. BP, IOP by Goldmann applanation tonometry and OAF velocity by transcranial doppler sonography was performed before medication and post medication on day 1, 7, and 30. Results: There was a significant decrease in IOP with both drugs; the effect was greater with atenolol. Atenolol: premedication IOP - 16.06 ± 2.13 mmHg and day 30-12.46 ± 1.94 (22.4%) [P < 0.001], amlodipine: premedication IOP-15.13 ± 2.55 mmHg and day 30- 13.06 ± 2.14 (13.68%) [P < 0.001]. A decrease of 0.5 mmHg in IOP with every 10 mmHg (95% CI: 0.121-0.826, P value = 0.01) decrease in systolic BP was noted after oral atenolol. The OAF peak systolic velocity and mean flow velocity were equally reduced with both drugs (P < 0.001). The end-diastolic velocity, reduced only with atenolol (P = 0.049) but returned to baseline with amlodipine at 1 month. Conclusions: BP reduction by atenolol and amlodipine led to decreases in IOP and OAF velocity, greater with atenolol. The IOP decrease was likely due to reduced blood flow. A slight decrease in the diastolic flow of the ophthalmic artery was noted with atenolol.

Cross Sectional Study among Intraocular Pressure, Mean Arterial Blood Pressure, and Serum Testosterone according to the Anthropometric Obesity Indices in Korean Men

Purpose

To investigate the association between intraocular pressure (IOP) and serum testosterone according to the severity of obesity.

Materials and Methods

We investigated the correlation of IOP-testosterone according to the anthropometric obesity indices, such as obesity index (OI), body mass index (BMI), and waist circumference to height ratio (WtHR). Each of the obesity indices was classified into three groups: normal, overweight, and obesity. In additional, the association of IOP-testosterone was compared between testosterone 3.0 ng/mL below and above.

Results

Total of 3,949 participants, the mean age was 58.86±10.06 years, mean IOP was 14.40±2.61 mmHg, mean arterial blood pressure (MAP) was 93.67±11.47 mmHg, and mean serum testosterone was 4.21±1.83 ng/mL. The association of MAP and IOP was significantly positively correlated according to the severity of obesity, but testosterone showed a significant negative relationship (p<0.05). IOP was significantly correlated with OI and BMI, but MAP and testosterone were correlated with all anthropometric obesity indices (p<0.05). The relationship of IOP and testosterone was significantly associated with only normal groups according to the degree of obesity (p<0.05). The IOP in patients with testosterone above 3.0 ng/mL was significantly higher than testosterone below 3.0 ng/mL (p<0.05).

Conclusions

The correlation of IOP-testosterone has a significantly positive relationship, in case of healthy men with normal weight by OI or BMI.

The Association of Intraocular Pressure With Obesity and Cardiometabolic Risk in a Young Farmworker Population

PRCIS

Intraocular pressure (IOP) was found to be significantly correlated with body mass index (BMI), waist circumference, and diastolic blood pressure (DBP) in a farmworker population located in the southeast Georgia, USA. BMI was correlated with IOP, independent of systemic blood pressures.

PURPOSE

Elevated IOP is a known risk factor for glaucomatous optic neuropathy and is believed to be associated with obesity and cardiometabolic diseases. The high prevalence of these conditions in the United States necessitates an evaluation of the relationship among obesity, cardiometabolic risks, and IOP among understudied younger populations.

MATERIALS AND METHODS

Farmworker data were collected from the annual Costa-Layman Health Fair between 2013 and 2017. Correlations of IOP with demographic factors, obesity, and cardiometabolic risks were analyzed using analysis of covariance, partial Pearson correlations, and linear regressions.

RESULTS

In the farmworker population (n=346), the mean IOP was 15.5 mm Hg and the prevalence of ocular hypertension (IOP>21 mm Hg) was 5.5%. BMI, waist circumference, and DBP were significantly correlated (r=0.192, P=0.001; r=0.128, P=0.017; r=0.142, P=0.007, respectively) with IOP when adjusted for age, sex, and ethnicity. Each 10 mm Hg increase in DBP corresponded with a 0.51 mm Hg increase in IOP. With adjustment for age, sex, ethnicity, systolic blood pressure, and DBP, BMI remained significantly correlated with IOP (r=0.166, P=0.002).

CONCLUSIONS

Higher IOP is associated with obesity measures including BMI and waist circumference and is correlated with DBP. These findings suggest that BMI is an independent risk factor for elevated IOP.

Positional Change of the Eyeball During Eye Movements: Evidence of Translatory Movement

Purpose: To investigate the positional change of the eyeball induced by horizontal and vertical gazing to deduce translatory movement, using three-dimensional (3D) magnetic resonance imaging (MRI).

Methods: In this prospective observational study participants underwent orbital MRI during central, right, left, up, and down gazing. MRI scans were processed using self-developed software; this software enabled 3D MR image reconstruction and the superimposition of reconstructed image sets between different gazes. After acquiring the coordinates of the eyeball centroid in each gaze, the changes in centroid coordinates from central gaze to the other gazes were estimated, and correlations with associated factors were evaluated.

Results: The mean distance of centroid movement was 0.69 ± 0.27 mm in abduction, 0.68 ± 0.27 mm in adduction, 0.43 ± 0.23 mm in elevation, and 0.44 ± 0.19 mm in depression. The mean angle of centroid movement in horizontal gaze, measured in terms of the movement of the left eye centroid in the axial plane, was 228.7° in abduction and −4.2° in adduction. In vertical gaze, the mean angle of centroid movement was −96.8° in elevation and 101.8° in depression. Axial length and ocular volume were negatively correlated with the distance of centroid movement in horizontal gaze.

Conclusions: The position of the eyeball moved in the same direction as the gaze during horizontal gaze, but in the opposite direction during vertical gaze. For accurate eye movement analyses, such as the measurement of the deviation angle in strabismus, translation should be considered in addition to rotation.

Evaluation of the 24-hour intraocular pressure and systemic blood pressure at the same time

PURPOSE

To obtain simultaneous 24-hour contact lens voltage and systemic arterial blood pressure values with the Sensimed Triggerfish system and Holter monitoring device.

METHODS

Ten primary open-angle glaucoma (POAG) and 8 pseudoexfoliation glaucoma (PXG) patients were included in the study. The Sensimed Triggerfish contact lens device was used to calculate the 24-hour IOP, and a Holter sphygmomanometer device was used for simultaneous 24-hour blood pressure measurements. We define the 8:00 am-11:00 pm period measurements as diurnal values and the other measurements as nocturnal values.

RESULTS

The mean nocturnal systolic values (nocturnal SBP 120.5±3.4 for POAG and 122.8±5.3mmHg for PXG) and diastolic BP (nocturnal DBP 70.2±1.9 for POAG and 68.1±1.2mmHg for PXG) were lower than the diurnal (diurnal SBP 134.6±5.3 for POAG, 145.9±41.7mmHg for PXG, diurnal DBP 79.4±5.8 for POAG and 78.6±5.1mmHg for PXG) values, and these differences were statistically significant in both groups (P=0.001 in DBP in PXG and P<0.001 for other values). In addition, nocturnal CL voltage values (228.8±41.1 for POAG and 214.3±47.0mVEq for PXG) were higher than the diurnal values (55.8±77.2 for POAG and 145.9±41.7mVEq for PXG) in the POAG and PXG groups, and these were statistically significant as well (P<0.001 for all). In the POAG and PXG groups, CL voltage had a statistically significant negative correlation with systolic (respectively, r: -0.248, P=0.001 and r: -0.272, P˂0.001) and diastolic (respectively, r: -0.115, P=0.036 and r: -0.160, P=0.028) BP values.

CONCLUSION

We observed that CL voltage values rose during the nocturnal period, with a concomitant decrease in systolic and diastolic BP.

A common humoral background of intraocular and arterial blood pressure dysregulation

BACKGROUND

It has been postulated that intraocular pressure, an important glaucoma risk factor, correlates positively with arterial blood pressure (blood pressure). However, results of experimental and clinical studies are often contradictory. It is hypothesized that, in some hypertensive patients, disturbances in intraocular pressure regulation may depend on biological effects of blood borne hormones underlying a particular type of hypertension, rather than on blood pressure level itself.

REVIEW

This review compares the effects of hormones on blood pressure and intraocular pressure, in order to identify a hormonal profile of hypertensive patients with an increased risk of intraocular pressure surge. The PUBMED database was searched to identify pre-clinical and clinical studies investigating the role of angiotensin II, vasopressin, adrenaline, noradrenaline, prostaglandins, and gaseous transmitters in the regulation of blood pressure and intraocular pressure.

RESULTS

Studies included in the review suggest that intraocular and blood pressures often follow a different pattern of response to the same hormone. For example, vasopressin increases blood pressure, but decreases intraocular pressure. In contrast, high level of nitric oxide decreases blood pressure, but increases intraocular pressure.

CONCLUSIONS

Arterial hypertension is associated with altered levels of blood borne hormones. Contradicting results of studies on the relationship between arterial hypertension and intraocular pressure might be partially explained by diverse effects of hormones on arterial and intraocular pressures. Further studies are needed to evaluate if hormonal profiling may help to identify glaucoma-prone patients.

Factors Affecting Intraocular Pressure Measured by Noncontact Tonometer

Purpose

To investigate the mean values of intraocular pressure (IOP) measured with non-contact tonometer (NCT) and evaluate the factors that may affect IOP.

Methods

A total of 850 subjects who were admitted to our clinic between March 2005 and February 2006 were recruited for the study. Subjects having blepharitis, conjunctivitis, corneal diseases, glaucoma suspicion, or glaucoma were not accepted to the study. All subjects were questioned about systemic diseases. IOP measurement with NCT and central corneal thickness (CCT) with ultrasound pachymetry were performed for each patient between 9 and 11 AM.

Results

The mean ages of 367 (43.2%) male subjects and 483 (56.8%) female subjects were 43.9±18.1 and 40.7±18.0 years ± SD, respectively. Since right and left eye IOP, CCT, and keratometric values were significantly correlated, right eye values were used for statistical purposes. Mean IOP values in males and females were 13.2±3.0 and 13.5±2.9 mmHg, respectively. Mean CCT values were 552.5±34.7 μm for males and 550.1±34.3 μm for females. In multiple regression analysis, IOP was found to be associated with gender, refractive error, CCT, and the presence of diabetes mellitus (DM).

Conclusions

Gender, CCT, the presence of DM, and refractive error may be significantly associated with IOP in this particular population.

Risk of Ocular Hypertension in Adults with Noninfectious Uveitis

PURPOSE

To describe the risk and risk factors for ocular hypertension (OHT) in adults with noninfectious uveitis.

DESIGN

Retrospective, multicenter, cohort study.

PARTICIPANTS

Patients aged ≥18 years with noninfectious uveitis seen between 1979 and 2007 at 5 tertiary uveitis clinics.

METHODS

Demographic, ocular, and treatment data were extracted from medical records of uveitis cases.

MAIN OUTCOME MEASURES

Prevalent and incident OHT with intraocular pressures (IOPs) of ≥21 mmHg, ≥30 mmHg, and increase of ≥10 mmHg from documented IOP recordings (or use of treatment for OHT).

RESULTS

Among 5270 uveitic eyes of 3308 patients followed for OHT, the mean annual incidence rates for OHT ≥21 mmHg and OHT ≥30 mmHg are 14.4% (95% confidence interval [CI], 13.4-15.5) and 5.1% (95% CI, 4.7-5.6) per year, respectively. Statistically significant risk factors for incident OHT ≥30 mmHg included systemic hypertension (adjusted hazard ratio [aHR], 1.29); worse presenting visual acuity (≤20/200 vs. ≥20/40, aHR, 1.47); pars plana vitrectomy (aHR, 1.87); history of OHT in the other eye: IOP ≥21 mmHg (aHR, 2.68), ≥30 mmHg (aHR, 4.86) and prior/current use of IOP-lowering drops or surgery in the other eye (aHR, 4.17); anterior chamber cells: 1+ (aHR, 1.43) and ≥2+ (aHR, 1.59) vs. none; epiretinal membrane (aHR, 1.25); peripheral anterior synechiae (aHR, 1.81); current use of prednisone >7.5 mg/day (aHR, 1.86); periocular corticosteroids in the last 3 months (aHR, 2.23); current topical corticosteroid use [≥8×/day vs. none] (aHR, 2.58); and prior use of fluocinolone acetonide implants (aHR, 9.75). Bilateral uveitis (aHR, 0.69) and previous hypotony (aHR, 0.43) were associated with statistically significantly lower risk of OHT.

CONCLUSIONS

Ocular hypertension is sufficiently common in eyes treated for uveitis that surveillance for OHT is essential at all visits for all cases. Patients with 1 or more of the several risk factors identified are at particularly high risk and must be carefully managed. Modifiable risk factors, such as use of corticosteroids, suggest opportunities to reduce OHT risk within the constraints of the overriding need to control the primary ocular inflammatory disease.

The association between intraocular pressure and different combination of metabolic syndrome components

BACKGROUND

Although the association between metabolic syndrome and intraocular pressure is well known, the relationship between the intraocular pressure and different combination of the components of metabolic syndrome has not been actively researched yet. The study aimed to investigate the relationship between the intraocular pressure and metabolic syndrome components with their different combinations.

METHODS

Thirty-one thousand two hundred seventy one healthy people aged 19-79 who attended a community hospital for a health check-up between January 2011 and December 2013 were enrolled in the study. Subjects with a history of intraocular disease, at least in one eye and those receiving medical treatment for glaucoma were excluded. Metabolic syndrome was diagnosed following the criteria defined in Circulation 2009.

RESULTS

Subjects with combination of three metabolic syndrome components of triglycerides, abdominal obesity, and fasting glucose had the highest intraocular pressure. And subjects with the combination of four components of blood pressure, high-density lipoproteins, triglycerides, fasting glucose had a significantly higher intraocular pressure than ones with the combination of all five metabolic syndrome components.

CONCLUSIONS

The difference in the risk of high intraocular pressure according to the different combination of the metabolic syndrome components could be confirmed. If additional follow-up studies are conducted, the findings can be used as an indicator for predicting intraocular pressure increases in patients with metabolic syndrome.

Relationship of Intraocular Pressure with Central Aortic Systolic Pressure

PURPOSE

To examine the relationship between central aortic systolic pressure (CASP) and intraocular pressure (IOP), and to compare the strength of any association with that of peripheral blood pressure and IOP.

METHODS

Adults ranging in age from 40 to 80 years were consecutively recruited from the population-based Singapore Chinese Eye Study. We measured CASP using arterial tonometry (BPro) and IOP using Goldmann applanation tonometry. All participants had a standardized examination including a complete ophthalmic and systemic examination. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured using peripheral blood pressure cuff. Univariable and multiple linear regression analyses were performed to examine the relationship between CASP and IOP. Standardized regression coefficients (sβ) were calculated to compare the associations between CASP and SBP with IOP.

RESULTS

A total of 372 consecutive Chinese participants were analyzed. After adjusting for age, gender, body mass index, total cholesterol, use of antihypertensive medication and central corneal thickness, each 10 mmHg increase in CASP was associated with 0.32 mmHg of IOP elevation [95% confidence interval (CI): 0.10-0.53, sβ = 0.160, p value = 0.004]. SBP also had a positive relationship with IOP (β = 0.279, 95% CI: 0.079-0.479, sβ = 0.152, p value = 0.006). Associations between IOP and CASP, SBP and DBP were similar in participants using antihypertensive medication to participant not using antihypertensives.

CONCLUSIONS

Increased CASP, as measured by arterial tonometry, is associated with higher IOP. Our results strengthen the relationship between systemic blood pressure and IOP.

Intraocular pressure and influencing systemic health parameters in a Korean population

Aim:

To evaluate the relationship between intraocular pressure (IOP) and systemic health parameters such as age, gender, body mass index (BMI), total cholesterol, high density lipoprotein (HDL), and triglyceride (TG) in a Korean population.

Materials and Methods:

A total of 30,893 healthy subjects underwent automated multiphasic tests, including non-contact tonometry, automated perimetry, fundus photography, and blood samplings for total cholesterol, HDL, and TG. Seven age groups were divided by decades ranging from 20 to 29 years to 80 + years. The association between IOP and BMI, plasma lipid profiles was examined using cross-sectional analysis.

Results:

The mean age of subjects was 47.7 years. The mean IOP of subjects was 15.4 ± 3.2 mmHg for both eyes. The mean IOP of men was significantly higher than women (P = 0.000). By multiple linear regression analysis, IOP was positively associated with gender (male), BMI, total cholesterol, and TG and negatively associated with age (P = 0.000). BMI, total cholesterol, and TG had significantly positive correlations with IOP after adjusting for age, gender, and other variables which can influence the IOP (P = 0.000).

Conclusions:

In a Korean population, the mean IOP, total cholesterol, TG, and BMI values of men were higher than women. IOP was found to increase with total cholesterol, TG, BMI, and to decrease with only age regardless of sex.

Apolipoprotein B: novel indicator of elevated intraocular pressure

PURPOSE

Many studies have reported associations between elevated intraocular pressure (IOP) and systemic health parameters, which suggest a common mechanism links IOP elevation and various related cardiometabolic risk factors. Furthermore, according to a recent study, serum apolipoprotein B (APO B) level is a predictor of coronary artery disease. This study was undertaken to analyse the relationship between serum apolipoprotein levels and IOP.

METHODS

Healthy people (28,852) who attended a community hospital for a health checkup between January 2011 and December 2013 were enroled in the study. We measured age, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), serum levels of total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and apolipoprotein A1 (APO A1) and APO B, APO B/APO A1 ratios, and IOP.

RESULTS

Univariate regression analysis showed IOP was positively correlated with BMI, SBP, DBP, TC, LDL-C, TG, APO B, and APO B/APO A1 (P<0.001), and negatively correlated with HDL-C (P<0.001). On the other hand, multivariate regression analysis adjusted for age, BMI, SBP, and DBP, revealed IOP was positive correlated with TC, TG, LDL-C, APO B, and APO B/APO A1, and negatively correlated with HDL-C (all <0.05).

CONCLUSIONS

Among the various lipid profiles investigated, APO B was found to be most strongly correlated with IOP, regardless of sex. Additional studies are required to confirm the validity of apolipoprotein level as an index for predicting IOP.

Longitudinal analysis of age-related changes in intraocular pressure in South Korea

PURPOSE

To assess the changes in intraocular pressure (IOP) with age in South Korea.

METHODS

Subjects aged 20-79 who had been receiving health examinations at a university hospital were enrolled. They completed physical and ophthalmic examinations. Subjects with ocular disease that could possibly affect their IOP were excluded. The relationships between IOP and age, blood pressure, heart rate, body mass index, blood chemistry, and electrolyte were analyzed using a linear mixed model.

RESULTS

Of the 33 712 subjects, 31 857 participants were enrolled. In a cross-sectional analysis, IOP also showed a negative correlation in all age groups (respectively, P<0.001). In particular, patients in their 60s~80s had a less steep decreasing slope of IOP with age than patients in their 20s~30s (correlation coefficient -0.260 and -0.168, respectively). In longitudinal analysis, negative trend was shown in the slope of tendency in total subjects. When analyzing the effect of gender on the relationship between age and IOP, females had a less steep decreasing slope of IOP with age than males by 0.05 mm Hg. With regard to systemic parameters, systolic blood pressure and heart rate were positively correlated with IOP (P<0.001).

CONCLUSION

IOP was significantly decreased with age, although the amount of change was small. In women and older age groups, IOP was less decreased than that of men and young age groups. In addition, IOP was positively associated with systolic blood pressure and heart rate.

Intraocular pressure and coronary artery calcification in asymptomatic men and women

OBJECTIVE

We evaluated the relationship between intraocular pressure (IOP) and the risk of coronary artery calcification as a predictable marker of cardiovascular disease (CVD) in a large study of asymptomatic men and women.

METHODS

A cross-sectional study was performed in 10 732 asymptomatic men and women without diagnosed CVD or glaucoma. Coronary artery calcium (CAC) was measured by cardiac CT. The IOPs of all participants were measured by experienced nurses with a non-contact tonometer and automatic air puff control. Logistic regression was used to estimate the OR (95% CI) for the presence of CAC (score >0) with IOP quartiles.

RESULTS

The prevalence of detectable CAC was 13.7% in men and 4.3% in women. Increasing levels of right IOP were significantly associated with an increased prevalence of CAC. After adjusting for age, sex, smoking, alcohol intake, physical activity, body mass index, educational level, centre, family history of CVD, use of dyslipidaemia medication, diabetes, hypertension, total cholesterol, high density lipoprotein cholesterol and triglycerides, the ORs for CAC score >0, comparing 2-4 quartiles of the right IOP to the lowest quartiles, were 1.32 (95% CI 1.09 to 1.59), 1.20 (95% CI 0.98 to 1.46), and 1.28 (95% CI 1.05 to 1.56), respectively. These associations did not differ by clinically relevant subgroups.

CONCLUSIONS

A higher IOP is significantly associated with the presence of CAC regardless of conventional cardiovascular risk factors. The present study provides more insight into understanding the process of subclinical atherosclerosis in CVD and the relationship with a higher IOP as a common pathophysiology.

Metabolic syndrome as a risk factor for elevated intraocular pressure

Objective: The aim of this study was to investigate the association between intraocular pressure and metabolic syndrome by comparing central corneal thicknesses.

Methods: One hundred sixty-two subjects were enrolled in this cross-sectional study, with 89 subjects in a metabolic syndrome group and 73 subjects in a control group. Ophthalmological examinations, including intraocular pressure and central corneal thickness measurements, were performed on each subject. Serum fasting glucose, triglyceride and HDL cholesterol levels were measured, and waist circumference, systolic and diastolic blood pressure of all patients were recorded.

Results: Participants with metabolic syndrome had a significantly higher intraocular pressure than those without metabolic syndrome (p = 0.008), and there was no statistically significant difference between the central corneal thicknesses of the two groups (p = 0.553). Most of the metabolic syndrome components were associated with higher intraocular pressure (p < 0.05).

Conclusions: There is a relationship between metabolic syndrome and intraocular pressure, but no association between metabolic syndrome and central corneal thicknesses. Intraocular pressure is affected by central corneal thicknesses, and intraocular pressure is used to correct according to the central corneal thicknesses measurement. To our knowledge, this is the first study that determines the positive relationship between metabolic syndrome and intraocular pressure by comparing the central corneal thicknesses of the groups.

High intraocular pressure is associated with cardiometabolic risk factors in South Korean men: Korean National Health and Nutrition Examination Survey, 2008-2010

OBJECTIVE

Elevated intraocular pressure (IOP) contributes to the progression of visual defects such as glaucoma. This study determined whether metabolic syndrome (MetS) and cardiovascular risk factors are associated with IOP in South Korean men.

METHODS

We analyzed data on 4875 men who participated in the Korean National Health and Nutrition Examination Survey 2008-2010. We recorded the values for age, weight, height, body mass index (BMI), waist circumference (WC), systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting blood glucose (FBG), insulin, homeostasis model assessment of estimated insulin resistance (HOMA-IR), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), non-HDL-C (NHDL-C), and TG/HDL-C, as well as sociodemographic factors. IOP was measured using Goldmann applanation tonometry.

RESULTS

Weight, BMI, WC, SBP, DBP, FBG, insulin, HOMA-IR, TC, LDL-C, TG, NHDL-C, TG/HDL-C, and the prevalence of MetS differed significantly among the three groups with IOP (P<0.05). Mean IOP was higher in subjects who were obese and had hypertension, diabetes mellitus, MetS, abdominal obesity, high TG, high FBG, or high BP compared with normal subjects (P<0.005). Analysis using Pearson's correlation coefficient showed that all cardiometabolic risk factors were significantly associated with IOP (P<0.005), with the exception of WC and HDL-C. A multivariate linear regression analysis showed that IOP was positively correlated with BMI, SBP, DBP, FBG, HOMA-IR, TC, LDL-C, TG, NHDL-C, and TG/HDL-C after adjusting for all covariates (all P<0.05).

CONCLUSIONS

Cardiometabolic risk factors, including the components of MetS, are associated with increased 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.

Increased iris-lens contact following spontaneous blinking: mathematical modeling

The purpose of this work was to study in silico how iris root rotation due to spontaneous blinking alters the iris contour. An axisymmetric finite-element model of the anterior segment was developed that included changes in the iris contour and the aqueous humor flow. The model geometry was based on average values of ocular dimensions. Blinking was modeled by rotating the iris root posteriorly and returning it back to the anterior. Simulations with maximum rotations of 2°, 4°, 6°, and 8° were performed. The iris-lens contact distance and the pressure difference between the posterior and anterior chambers were calculated. When the peak iris root rotation was 2°, the maximum iris-lens contact increased gradually from 0.28 to 0.34mm within eight blinks. When the iris root was rotated by 6° and 8°, the pressure difference between the posterior and anterior chambers dropped from a positive value (1.23Pa) to negative values (-0.86 and -1.93Pa) indicating the presence of reverse pupillary block. Apparent iris-lens contact increased with steady blinking, and the increase became more pronounced as posterior rotation increased. We conclude that repeated iris root rotation caused by blinking could maintain the iris in a posterior position under normal circumstances, which would then lead to the clinically observed anterior drift of the iris when blinking is prevented.

Epidemiologic characteristics of intraocular pressure in the Korean and Mongolian populations: the Healthy Twin and the GENDISCAN study

PURPOSE

The purpose of this study was to demonstrate a negative association between intraocular pressure (IOP) and age in 2 Asian populations. In addition, we evaluated genetic and nongenetic factors associated with IOP.

DESIGN

Family-based cohort study.

PARTICIPANTS

Study subjects >10 years of age from one Korean (The Healthy Twin; n = 1431) and 2 Mongolian populations (The GENDISCAN; n = 859 and 806) with IOP values.

METHODS

The IOP values were measured with a noncontact tonometer. Each participant received a standard health examination and received questionnaires, which include candidate risk factors on IOP. Mixed models were used to identify risk factors for IOP. Variance-component methods were applied to estimate the heritability of IOP.

MAIN OUTCOME MEASURES

The negative trend of IOP with aging and evaluation of impact of genetic and nongenetic components on IOP.

RESULTS

The mean ages were 43.6, 34.1, and 36.3 years for the Korean, Orhontuul, and Dashbalbar populations, respectively. The mean IOPs were 14.4 mmHg (95% confidence interval [CI], 14.3-14.6) in the Koreans and 14.1 mmHg (95% CI, 13.9-14.3) and 12.6 mmHg (95% CI, 12.4-12.9) in the Orhontuul and Dashbalbar populations, respectively. In the 3 populations, the IOP decreased as age increased. We replicated an association of systolic blood pressure (SBP) with IOP. In addition, components of the metabolic syndrome (MS), such as plasma glucose, lipid level, and body mass index, showed positive associations with IOP, after adjusting for age and SBP. The IOP also had strong genetic contributions in all populations (heritability, 0.47-0.51).

CONCLUSIONS

Negative associations between age and IOP were observed in all 3 populations, which cannot be explained by the increasing prevalence of myopia in the younger generation. The different age trend in IOP may in part be responsible for differences in the prevalence of glaucoma subtypes. Our findings suggest that associations between IOP and MS components were independent of established risk factors such as SBP or age. In addition, the importance of inherited risks requires further genetic dissection of IOP determinants for biological understandings of underlying pathophysiology.

Computational simulation of altitude change-induced intraocular pressure alteration in patients with intravitreal gas bubbles

PURPOSE

To study the impact of altitude on the intraocular pressure (IOP) in an eye with an intravitreal gas bubble.

METHODS

A mathematical model was developed to simulate intravitreal gas bubble expansion caused by change in altitude. Mechanical deformation of the eye was simulated using a finite-element model. Intraocular pressure-driven changes in aqueous humor flow were also considered. Two cases were studied: 1) ascent from sea level to 3,000 ft followed by immediate return to sea level and 2) ascent to 3,000 ft followed by prolonged exposure to 3,000 ft. The effect of IOP-lowering medications was studied by changing the model parameters.

RESULTS

The IOP increase was directly related to the initial bubble size when ascent to 3,000 ft was simulated. When prolonged exposure to high altitude was modeled, loss of aqueous humor led to a less elevated value of IOP. In a typical simulated case, when the outflow facility was increased, the predicted IOP rise was reduced by 28%.

CONCLUSION

Theoretical modeling of an eye with an intravitreal gas bubble can help an ophthalmologist evaluate the impact of altitude-induced IOP changes. Our model suggests that IOP-lowering drugs could help manage altitude-induced IOP changes in the presence of intravitreal gas bubbles.

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.

Reverse pupillary block slows iris contour recovery from corneoscleral indentation

Corneoscleral indentation changes the iris contour and alters the angle between the iris and cornea. Although this effect has long been observed, the mechanism by which it occurs remains poorly understood. Previous theoretical research has shown that corneoscleral indentation can deform the eye globe and consequently rotate the iris root. In this work, we studied the fluid-structure interaction between the iris and aqueous humor, driven by iris root rotation. The iris root rotation obtained from our previous whole-globe model was used as a boundary condition for a fluid-structure interaction finite element model of the anterior eye. We studied the effect of two parameters-rotation angle and indentation speed-on the iris contour and aqueous humor dynamics. We found that posterior rotation of the iris root caused posterior bowing of the iris. After the iris root was returned to its original orientation, the aqueous humor was trapped in the anterior chamber because the iris tip pinned against the lens (reverse pupillary block). After 0.5-2 min of simulation, aqueous humor secretion into the posterior chamber and outflow from the anterior chamber allowed the system to return to its original steady state flow condition. The faster or farther the iris root rotated, the longer it took to return to steady state. Reverse pupillary block following corneoscleral indentation is a possible explanation for the clinical observation that prevention of blinking causes the iris to drift forward.

Relation between central corneal thickness and intraocular pressure in Punjabi population

OBJECTIVE

The motive of this study was to determine the variation of central corneal thickness (CCT) in the Punjabi population and to examine its relationship with intraocular pressure (IOP) using a non-contact tonometer. The study and results emphasize the effects of age, sex and refraction on this relationship, which is important for the diagnosis and prevention of glaucoma in adequate time.

METHODS

The study design was a cross-sectional, population-based survey. The participants were 279 females and 253 males of Punjab Province, India, in the age group of 21-70 years. The CCT was measured using an ultrasonic pachymeter, and the IOP was measured using an air-puff tonometer in all subjects.

RESULTS

The mean values of CCT and IOP were observed to vary imprecisely with age. The measurement of both parameters was also affected by sex and refraction. The linear regression analysis suggests that the mean value of CCT grows progressively with increasing value of mean IOP. A significant positive correlation was identified between CCT and IOP in the age group of 21-70 years. The authors inferred that this correlation value varies prominently with age for both sexes, which needs to be investigated further.

CONCLUSIONS

The authors suggest that CCT is a noteworthy source of variation in IOP measurements for males as well as females belonging to different age groups, when assessing IOP as a risk for glaucoma in the Punjabi population.

Influence of lens material and intra-ocular pressure on the outcome of non-contact tonometry over soft contact lenses

PURPOSE

To quantify the influence of soft lens rigidity and power on the difference between intraocular pressure values (DeltaIOP) obtained by non-contact tonometry through soft lenses in situ and over the cornea (IOP).

METHODS

Both eyes of 25 patients, attending for either routine contact lens check up, were fitted with a (I) low water content silicone hydrogel lenses of relatively high modulus of rigidity (modulus of rigidity 1.2MPa, Focus Night and Day, Cibavision) and (II) high water content daily disposable of relatively low modulus of rigidity (0.91MPa, Focus Dailies, Cibavision). IOP measurements were taken over the cornea and repeated over the lens after insertion. Lens powers ranged from -7.50D to +6.00D.

RESULTS

ANOVA revealed DeltaIOP was associated with both lens power and material (p<0.05). Multiple linear regression revealed relationships between DeltaIOP (y) lens power (x(1)) and IOP (x(2)) as follows (I), right eyes, y = 0.899x(1) - 0.172x(2) + 5.659 (F = 15.615, r = 0.766, p < 0.001, n = 25) (I), left eyes, y = 0.993x(1) - 0.101x(2) + 4.694 (F = 23.368, r = 0.825, p < 0.001, n = 25) (II) right eyes, y = 0.399x(1) - 0.370x(2) + 6.595 (F = 11.804, r = 0.719, p < 0.001, n = 25) (II) left eyes, y = 0.561(1) - 0.225x(2) + 4.153 (F = 28.736, r = 0.723, p < 0.001, n = 25)

CONCLUSION

DeltaIOP appears to be related to lens power, material and to a lesser extent IOP. Practitioners should derive their own empirical relationship between DeltaIOP, lens power and IOP for the specific types of soft lenses they commonly use. This would improve efficiency in the screening of IOP in more susceptible soft lens wearers.

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.

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.

High Altitude and the Eye: A Case Controlled Study in Clinical Ocular Anthropometry of Changes in the Eye

Tribal natives of two spatially separate districts of Lahaul-Spiti (mean altitude = 3300 m) and Kinnaur (mean altitude = 1,700 m) in the Himalayan state of Himachal Pradesh have lived for centuries as closed isolated groups, marrying within the local community up to the recent past. Studies on highland natives in the Andes have shown differences in chest diameters, lung volumes, hematocrit, and the like, in those living at high altitudes. We wanted to study whether stay at high altitude for generations confers any change in the ocular anthropometry. No study of this nature is available in the literature. We studied the ocular parameters using Snellen's charts, Standard Royal-Air-Force Rule, A-2,500 Sonomed A-Scan, Goldmann's aplanation tonometer, and S-7,000 Autorefractometer on 50 healthy volunteers at the Indira Gandhi Medical College Out Patient Department at Shimla (mean altitude = 2,100 m). Those living at higher altitudes in Lahaul-Spiti [LS] (n = 10) had significantly wider nose bridge width (p < 0.05); inter-inner canthal distance [IICD] (p < 0.05); inter-outer canthal distance [IOCD] (p < 0.05); and interpupillary distance [IPD] (p < 0.05) than the group living at Kinnaur (n = 40) at lower elevation. The LS group also had narrower palpebral fissure length in the vertical dimension (p = 0.05) and a lower IOP (p = 0.002) than the Kinnaur group. The axial length, lens thickness, and anterior chamber depth were comparable in the two groups. It appears that the eye and its adnexa respond to hypoxia, ultraviolet radiations, and persistent snow cover at high altitude by altering its anthropometry in a subtle but discernible manner. This was a hitherto unexplored area in the literature. Further studies to elucidate and substantiate the findings of the study are indicated.

Elevated intraocular pressure is associated with insulin resistance and metabolic syndrome

BACKGROUND AND AIM

Elevated intraocular pressure (IOP), a well-known risk factor for glaucoma, has recently been shown to be associated with some metabolic complications and obesity. We investigated the link between IOP and metabolic disturbances, focusing especially on metabolic syndrome and insulin resistance.

METHODS

Eye examinations, including IOP measurement, were conducted on 943 subjects (533 men and 410 women). Body mass index (BMI), percent body fat, waist circumference, systolic and diastolic pressure, fasting insulin, glucose, lipids, and other metabolic parameters were measured. The homeostasis model assessment (HOMA) score and McAuley index were calculated to assess whole-body insulin resistance.

RESULTS

Both of these insulin resistance indices showed positive associations with IOP (p < 0.05), even after statistical adjustment for other risk factors. IOP was higher in participants with metabolic syndrome, as compared to those who did not have metabolic syndrome. The mean IOP tended to increase linearly with the presence of increasing numbers of components for metabolic syndrome.

CONCLUSIONS

These results suggest that insulin resistance might contribute to an explanation that would account for many previous findings concerning the association between IOP and obesity, hypertension, and diabetes.