Association of demographic, familial, medical, and ocular factors with intraocular pressure

Acute alcohol consumption modulates corneal biomechanical properties as revealed by optical coherence elastography

Acute alcohol ingestion has been found to impact visual functions, including eye movement, but its effects on corneal biomechanical properties remain unclear. This study aimed to investigate the influence of acute alcohol consumption on corneal biomechanical properties using optical coherence elastography (OCE). An air-coupled ultrasound transducer induced elastic waves in mice corneas in vivo, and a high-resolution phase-sensitive optical coherence tomography (OCT) system tracked the mechanical waves to quantify the elastic wave speed. In vivo measurements were performed on three groups of age- and gender-matched mice: control, placebo (administered saline), and alcohol (administered ethanol) groups. Longitudinal measurements were conducted over a one-hour period to assess acute temporal changes in wave speeds, which are associated with inherent biomechanical properties of the cornea. The results showed a significant decrease in wave speed for the alcohol group after 10 min of ingestion in comparison to pre-ingestion values (p = 0.0096), whereas the temporal wave speed changes for the placebo group were statistically insignificant (p = 0.076). In contrast, the control group showed no significant changes in elastic wave speed and corneal thickness. Furthermore, a significant difference was observed between the wave speeds of the placebo and alcohol groups at each measurement time point between 10 and 50 min (p < 0.05), though both groups exhibited a similar trend in corneal thickness change. The findings of this study have important implications for clinical assessments and research in corneal disorders, highlighting the potential of OCE as a valuable tool for evaluating such changes.

Impact of smoking on glaucoma

PURPOSE OF REVIEW

Assessing whether lifestyle related factors play a role in causing primary open-angle glaucoma (POAG) is of great value to clinicians, public health experts and policy makers. Smoking is a major global public health concern and contributes to ocular diseases such as cataracts, and age-related macular degeneration through ischemic and oxidative mechanisms. Recently, smoking has been investigated as a modifiable risk factor for glaucoma. In the presence of an association with glaucoma, provision of advice and information regarding smoking to patients may help reduce the burden of disease caused by POAG. Therefore, the aim of this review is to summarize the current evidence regarding the effect of smoking in the pathogenesis of glaucoma and its incidence, progression as well as the benefits of smoking cessation.

RECENT FINDINGS

While the association between glaucoma development and smoking history is controversial, in the last decade, several recent studies have helped to identify possible effects of smoking, especially heavy smoking, in regard to glaucomatous progression. Smoking cessation may possibly be protective against glaucoma progression.

SUMMARY

Smoking may play a role in glaucoma progression and long-term smoking cessation may be associated with lower glaucoma progression. The dose-response relationship between smoking and glaucoma as well as therapeutic potential of smoking cessation needs to be further validated with both preclinical and rigorous clinical studies.

Towards modifying the genetic predisposition for glaucoma: An overview of the contribution and interaction of genetic and environmental factors

Glaucoma, the leading cause of irreversible blindness worldwide, is a complex human disease, with both genetic and environmental determinants. The availability of large-scale, population-based cohorts and biobanks, combining genotyping and detailed phenotyping, has greatly accelerated research into the aetiology of glaucoma in recent years. Hypothesis-free genome-wide association studies have furthered our understanding of the complex genetic architecture underpinning the disease, while epidemiological studies have provided advances in the identification and characterisation of environmental risk factors. It is increasingly recognised that the combined effects of genetic and environmental factors may confer a disease risk that reflects a departure from the simple additive effect of the two. These gene-environment interactions have been implicated in a host of complex human diseases, including glaucoma, and have several important diagnostic and therapeutic implications for future clinical practice. Importantly, the ability to modify the risk associated with a particular genetic makeup promises to lead to personalised recommendations for glaucoma prevention, as well as novel treatment approaches in years to come. Here we provide an overview of genetic and environmental risk factors for glaucoma, as well as reviewing the evidence and discussing the implications of gene-environment interactions for the disease.

Estimation of Physiologic Pressures: Invasive and Non-Invasive Techniques, AI Models, and Future Perspectives

The measurement of physiologic pressure helps diagnose and prevent associated health complications. From typical conventional methods to more complicated modalities, such as the estimation of intracranial pressures, numerous invasive and noninvasive tools that provide us with insight into daily physiology and aid in understanding pathology are within our grasp. Currently, our standards for estimating vital pressures, including continuous BP measurements, pulmonary capillary wedge pressures, and hepatic portal gradients, involve the use of invasive modalities. As an emerging field in medical technology, artificial intelligence (AI) has been incorporated into analyzing and predicting patterns of physiologic pressures. AI has been used to construct models that have clinical applicability both in hospital settings and at-home settings for ease of use for patients. Studies applying AI to each of these compartmental pressures were searched and shortlisted for thorough assessment and review. There are several AI-based innovations in noninvasive blood pressure estimation based on imaging, auscultation, oscillometry and wearable technology employing biosignals. The purpose of this review is to provide an in-depth assessment of the involved physiologies, prevailing methodologies and emerging technologies incorporating AI in clinical practice for each type of compartmental pressure measurement. We also bring to the forefront AI-based noninvasive estimation techniques for physiologic pressure based on microwave systems that have promising potential for clinical practice.

Changes in intraocular pressure after pharmacological pupil dilatation in an elderly Chinese population in Taiwan: The Shihpai eye study

BACKGROUND

Mydriatic drugs are often used in ophthalmic clinics for pupil dilatation to assess the optic nerve and retina. Clinical studies have indicated that an increase in intraocular pressure (IOP) after pupil dilation is noted in open-angle glaucoma patients, those with narrow angles and in normal subjects. Asians are more likely to have narrow angles. Moreover, age-related cataract may increase the crowdedness of the angle. This study aimed to assess the effects of mydriatic pupil dilatation on IOP in an elderly Chinese population.

METHODS

The Shihpai Eye Study was a community-based, cross-sectional survey of vision and eye diseases among noninstitutionalized subjects aged 65 years and older in Shihpai, Taipei, Taiwan. IOP was taken using noncontact tonometry. The pupil was dilated with 1% tropicamide. IOP was measured again after maximal pupil dilatation 1 hour after mydriasis.

RESULTS

Of the 2045 participants, 1361 (66.6%) participated in both the questionnaire and eye examinations. The mean IOP before pupil dilatation was 12.9 ± 3.1 mmHg and was 12.8 ± 3.4 mmHg (range: 5-36 mmHg) after pupil dilatation. IOP higher than 21 mmHg after pupil dilation was noted in 17 (1.34%) participants, of whom IOP exceeded 30 mmHg in two (0.16%). Overall, the changes in IOP before and after pupil dilatation were insignificant ( p = 0.04). In the final regression analyses, refractive status toward hyperopia ( p < 0.01) was the only significant factor associated with an increase in IOP of at least 4 mmHg after pupil dilatation.

CONCLUSION

Our results revealed that the increase in IOP after pharmacological pupil dilatation was minimal, and the incidence of acute angle-closure attack was insignificant. Hyperopic status was the only factor related to an increase in IOP of > 4 mmHg. Caution should be exercised if one is hyperopic or has a history of glaucoma and rechecking IOP in these subjects is suggested after pharmacological mydriasis.

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.

Intraocular pressure and diurnal fluctuation of open-angle glaucoma and ocular hypertension: a baseline report from the LiGHT China trial cohort

AIMS

To report the baseline intraocular pressure (IOP) characteristics and its diurnal fluctuation in the Laser in Glaucoma and Ocular Hypertension China cohort.

METHODS

622 primary open-angle glaucoma (POAG) patients and 149 ocular hypertension (OHT) patients were recruited at Zhongshan Ophthalmic Center from 2015 to 2019. Standardised ocular examinations were performed including IOP measurement using the Goldmann applanation tonometer. Daytime phasing IOP was recorded at 8:00, 10:00, 11:30, 14:30, 17:00 hour.

RESULTS

The mean baseline IOP was 20.2 mm Hg for POAG patients and 24.4 mm Hg for OHT. Multiple regression analysis revealed that thicker central corneal thickness (CCT) was correlated with higher IOP in both POAG and OHT. Male gender and younger age were correlated with higher IOP only for POAG. As for diurnal IOP fluctuation, mean IOP fluctuation was 3.4 mm Hg in POAG eyes and 4.4 mm Hg in OHT. The peak and trough IOP occurred at 8:00 and 14:30 hour in both POAG and OHT eyes.

CONCLUSIONS

Younger age, male gender and thicker CCT are correlated to higher IOP in POAG patients while only thicker CCT is related to higher IOP in OHT patients. Peak IOP appears mostly at early morning or late afternoon and trough value occurs mostly at early afternoon.

Alcohol, intraocular pressure and open-angle glaucoma: A systematic review and meta-analysis

Topic

This systematic review and meta-analysis summarizes the existing evidence for the association of alcohol use with intraocular pressure (IOP) and open-angle glaucoma (OAG).

Clinical Relevance

Understanding and quantifying these associations may aid clinical guidelines or treatment strategies and shed light on disease pathogenesis. The role of alcohol, a modifiable factor, in determining IOP and OAG risk also may be of interest from an individual or public health perspective.

Methods

The study protocol was preregistered in the Open Science Framework Registries (https://osf.io/z7yeg). Eligible articles (as of May 14, 2021) from 3 databases (PubMed, Embase, Scopus) were independently screened and quality assessed by 2 reviewers. All case-control, cross-sectional, and cohort studies reporting a quantitative effect estimate and 95% confidence interval (CI) for the association between alcohol use and either IOP or OAG were included. The evidence for the associations with both IOP and OAG was qualitatively summarized. Effect estimates for the association with OAG were pooled using random effects meta-analysis. Studies not meeting formal inclusion criteria for systematic review, but with pertinent results, were also appraised and discussed. Certainty of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework.

Results

Thirty-four studies were included in the systematic review. Evidence from 10 studies reporting an association with IOP suggests that habitual alcohol use is associated with higher IOP and prevalence of ocular hypertension (IOP > 21 mmHg), although absolute effect sizes were small. Eleven of 26 studies, comprising 173 058 participants, that tested for an association with OAG met inclusion criteria for meta-analysis. Pooled effect estimates indicated a positive association between any use of alcohol and OAG (1.18; 95% confidence interval [CI], 1.02–1.36; P = 0.03; I² = 40.5%), with similar estimates for both prevalent and incident OAG. The overall GRADE certainty of evidence was very low.

Conclusions

Although this meta-analysis suggests a harmful association between alcohol use and OAG, our results should be interpreted cautiously given the weakness and heterogeneity of the underlying evidence base, the small absolute effect size, and the borderline statistical significance. Nonetheless, these findings may be clinically relevant, and future research should focus on improving the quality of evidence.

Reported evidence of vitamin E protection against cataract and glaucoma

Cataract and glaucoma are the major causes of severe visual loss and blindness in older adults. This review article describes the currently available basic and clinical evidence regarding vitamin E protection against these eye diseases in the chronologic order of the publications. Experimental evidence has suggested both that oxidative stress due to the accumulation of free radicals plays a role in the pathogenesis of cataracts and glaucoma and that the process can be prevented or ameliorated by vitamin E. The results of observational studies have been inconsistent regarding the association between blood vitamin E levels and the risk of age-related cataract or glaucoma. Despite the encouraging effects of vitamin E from case series, case-control studies, and cross-sectional studies in humans, the effects on cataract formation and/or progression have not been consistent among prospective and randomized control studies; few randomized control studies have tested the effects of supplemental vitamin E on glaucoma development or progression. Given the high prevalence of cataract and glaucoma in the elderly population, even a modest reduction in the risk for these eye diseases would potentially have a substantial public health impact; however, the potential benefits of vitamin E on cataract or glaucoma remain inconclusive and need to be carefully considered.

Time-of-Year Variation in Intraocular Pressure

PRÉCIS

In this study conducted in Chicago, IL, intraocular pressure (IOP) level was found to have a subtle, but measurable, annual pattern. Reasonable evidence is presented for a time-of-year variation in IOP. Adequate numbers of subjects must be studied to detect this small variation.

PURPOSE

The aim was to investigate the relationship between IOP and time of year.

METHODS

During a separate investigation, patients from 2011 to 2018 (dataset A, N=3041) in an urban, academic facility in Chicago, IL received an examination that included Goldmann applanation tonometry. Regression analyses assessed the relationship between time of year and IOP. Two additional datasets, 1 collected in a similar manner during 1999 and 2002 (dataset B, N=3261) and another consisting of all first visits during 2012 and 2017 (dataset C, N=69,858), were used to confirm and further investigate trends.

RESULTS

For dataset A, peak mean IOP occurred in December/January (15.7±3.7/15.7±3.8 mm Hg) and lowest in September (14.5±3.1 mm Hg). The analysis suggested conventional quarterly analysis (January to March, etc.) can conceal time-of-year relationships because of inadequate statistical power and timing of IOP variation. Multiple linear regression analysis, with a November-to-October reordering, detected an annual, downward IOP trend (P<0.0001). Analysis of dataset B confirmed this trend (P<0.001). Fourier analysis on datasets A and B combined supported a 12-month IOP cycle for right/left eyes (P=0.01/P=0.005) and dataset C provided stronger evidence for an annual periodicity (P<0.0001). Harmonics analysis of dataset C showed a repeating pattern where IOP trended downward around April, and then back upward around October.

CONCLUSIONS

This analysis strongly supports a demonstrable annual, cyclical IOP pattern with a trough to peak variation of ≈1 mm Hg, which has a seasonal relationship.

Alcohol and the Eye

In this article, we present a review of ocular conditions related to alcohol consumption. A search of the literature published from 1952 to March 2020 was performed. The titles and abstracts were screened and the eligible studies were selected. PubMed, ISI Web of Knowledge database, Scopus, Embase, and the Cochrane Library were searched. We categorized the relationship between alcohol intake and ocular conditions by the type of ocular exposure to alcohol. Accordingly, ocular findings following acute alcohol intoxication, optic neuropathy following methanol toxicity, congenital conditions related to maternal alcohol consumption, and ocular disease related to chronic alcoholism are discussed. The main feature of alcohol intoxication in the eye is abnormal eye movement. Acute optic neuropathy secondary to methyl alcohol consumption is a serious ocular disease with permanent vision loss or scotoma. Prenatal exposure to ethanol may end in fetal alcohol spectrum disease, where ocular findings are a constant component. The association between chronic alcohol consumption and increased risks of cataract, age-related macular degeneration, diabetic retinopathy, different types of optic neuropathy, impairment of visual quality, retinal vascular disease, and ocular surface disease has also been reported. Along with detrimental medical and social effects, the role of alcohol consumption in different ocular conditions should be considered, as alcohol-induced visual disturbances may contribute to the heavy burden of alcohol abuse on the healthcare system and overall quality of life.

A Cohort Study on Associations between Fundus/intraocular Pressure Abnormality and Medical Check-up Items

PURPOSE

To evaluate the associations between medical check-up items (MCI) for fundus and intraocular pressure abnormality (FIPA) diseases in the Department of Health Management Centre, the Fifth Affiliated Hospital of Sun Yat-sen University (DHMC-FHS).

PATIENTS AND METHODS

Individuals who visited DHMC-FHS and underwent MCI between June 2017 to May 2019 were included, 3237 subjects. A total of 356 participants were diagnosed as FIPA and enrolled. The general clinical characteristics were collected. Diseases for FIPA diagnosed included five cohort, high intraocular pressure, diabetic retinopathy, hypertension fundus arteriosclerosis, large eye cup, and high myopia fundus changes. Possible impact factors of MCI included blood routine, B-ultrasound, heart rate, hypertension, hyperlipidemia, standard vision, cerebral arteriosclerosis, body mass, arterial/carotid arteriosclerosis, etc. Further, the Pearson's correlation coefficients and logistic regression analyses were used to examine associations between MCI and FIPA.

RESULTS

The weighted study population who belonged to FIPA included 356 subjects. There were significant differences in age, IOP, habitual exercise, smoking, sleep duration (P˂0.05) between FIPA and without FIPA. And RBC, Hemoglobin, B-ultrasound abnormal event, heart rate, systolic pressure, diastolic pressure, TC, LDL-C, standard vision, cerebral arteriosclerosis, body mass index, carotid arteriosclerosis were positively correlated with high intraocular pressure, hypertension fundus arteriosclerosis and high myopia fundus changes (P < .05). Possible prognosis risk factors, higher IOP, habitual exercise and more frequent smoking affect FIPA prognosis significantly [Odds ratio (OR) = 0.53, P = .01; OR = 0.13, P = .03; OR = 0.83; P = .04, respectively].

CONCLUSION

Of FIPA participants, high intraocular pressure, hypertension fundus arteriosclerosis and high myopia fundus changes were shown a positive relationship with MCI. Control IOP, habitual exercise and less frequent smoking were regarded as positive associations with decreased FIPA. These findings could help us prevent and diagnose FIPA diseases in time via MCI.

The Role of Chromosome X in Intraocular Pressure Variation and Sex-Specific Effects

Purpose

The purpose of this study was to identify genetic variants on chromosome X associated with intraocular pressure (IOP) and determine if they possess any sex-specific effects.

Methods

Association analyses were performed across chromosome X using 102,407 participants from the UK Biobank. Replication and validation analyses were conducted in an additional 6599 participants from the EPIC-Norfolk cohort, and an independent 331,682 participants from the UK Biobank.

Results

We identified three loci associated with IOP at genomewide significance (P < 5 × 10-8), located within or near the following genes: MXRA5 (rs2107482, P = 7.1 × 10-11), GPM6B (rs66819623, P = 6.9 × 10-10), NDP, and EFHC2 (rs12558081, P = 4.9 × 10-11). Alleles associated with increased IOP were also associated with increased risk for primary open-angle glaucoma in an independent sample. Finally, our results indicate that chromosome X genetics most likely do not illicit sex-specific effects on IOP.

Conclusions

In this study, we report the results of genomewide levels of association of three loci on chromosome X with IOP, and provide a framework to include chromosome X in large-scale genomewide association analyses for complex phenotypes.

Smoking Is Associated with Higher Intraocular Pressure Regardless of Glaucoma: A Retrospective Study of 12.5 Million Patients Using the Intelligent Research in Sight (IRIS®) Registry

PURPOSE

To compare the average intraocular pressure (IOP) among smokers, past smokers, and never smokers using the American Academy of Ophthalmology Intelligent Research in Sight (IRIS®) Registry.

DESIGN

Retrospective database study of the IRIS® Registry data.

PARTICIPANTS

Intelligent Research in Sight Registry patients who were seen by an eye care provider during 2017.

METHODS

Patients were divided into current smoker, past smoker, and never smoker categories. The IOP was based on an average measurement, and separate analyses were performed in patients with and without a glaucoma diagnosis based on International Classification of Diseases (Ninth Edition and Tenth Edition) codes. Stratified, descriptive statistics by glaucoma status were determined, and the relationship between smoking and IOP was assessed with a multivariate linear regression model.

MAIN OUTCOME MEASURES

Mean IOP.

RESULTS

A total of 12 535 013 patients were included. Compared with never smokers, current and past smokers showed a statistically significantly higher IOP by 0.92 mmHg (95% confidence interval [CI], 0.88-0.95 mmHg) and 0.77 mmHg (95% CI, 0.75-0.79 mmHg), respectively, after adjusting for age, gender, glaucoma, age-related macular degeneration, diabetic retinopathy, cataract, glaucoma surgery, cataract surgery, and first-order interactions. In addition, the difference in IOP between current and never smokers was the highest in the fourth decade, regardless of the glaucoma status (glaucoma group, 1.14 mmHg [95% CI, 1.00-1.29 mmHg]; without glaucoma group, 0.68 mmHg [95% CI, 0.65-0.71 mmHg]).

CONCLUSIONS

Current smokers and past smokers have higher IOP than patients who never smoked. This difference is higher in patients with an underlying glaucoma diagnosis.

Relationship between Alcohol Consumption and Ocular Pressure according to Facial Flushing in Korean Men with Obesity

Background

This study aimed to examine the relationship between alcohol consumption and intraocular pressure (IOP) according to facial flushing in Korean men with obesity.

Methods

The study included 479 Korean men with a body mass index of ≥25 kg/m² (75 non-drinkers, 174 with drinking-related facial flushing, and 230 without facial flushing) who underwent health check-ups between October 1, 2016 and March 31, 2017. Multivariate logistic regression was used to assess the relationship between alcohol consumption and high IOP (≥21 mm Hg).

Results

Flushers consuming ≤16 drinks per week had a significantly higher risk of high IOP than non-drinkers, depending on alcohol consumption (≤8 standard drinks: odds ratio [OR], 4.49; 95% confidence interval [CI], 1.05– 19.25; >8 but ≤16 standard drinks: OR, 8.14; 95% CI, 1.37–48.45). However, when the consumption was >16 drinks per week, the high IOP risk did not significantly increase (OR, 0.71; 95% CI, 0.05–10.69). In addition, there was no significant relationship between alcohol consumption and high IOP among non-flushers consuming ≤8 drinks per week (OR, 2.07; 95% CI, 0.52–8.19). However, a significantly increased risk of high IOP was observed among non-flushers consuming >8 drinks per week, depending on alcohol consumption (>8 but ≤16 standard drinks: OR, 4.84; 95% CI, 1.14–20.61; >16 standard drinks: OR, 4.08; 95% CI, 1.02–16.26).

Conclusion

This study suggests that obese men with alcohol flush reactions may have an increased risk of high IOP with the consumption of smaller amounts of alcohol than non-flushers.

Intraocular Pressure and Its Associations in a Russian Population: The Ural Eye and Medical Study

PURPOSE

To assess the normal distribution of intraocular pressure (IOP) and its associations with ocular, medical, and socioeconomic factors in a Russian population.

DESIGN

Population-based cross-sectional study.

METHODS

The Ural Eye and Medical Study conducted in a rural and urban area in Ufa/Bashkortostan included 5899 (80.5%) participants out of 7328 eligible individuals aged 40+ years. IOP was measured by noncontact tonometry.

RESULTS

After exclusion of individuals after glaucoma surgery or with antiglaucomatous therapy, mean IOP was 13.6 ± 3.8 mm Hg (median: 13 mm Hg; range: 3-49 mm Hg; 95% confidence interval [CI]: 8-23 mm Hg). The IOP range within the mean ± 2 standard deviations was 6.0-21.2 mm Hg. In multivariable analysis higher IOP was associated (regression coefficient r: 0.40) with the systemic parameters of female sex (nonstandardized regression coefficient B: 0.44; 95%CI: 0.22, 0.66; standardized regression coefficient beta: 0.06; P < .001), urban region of habitation (B: -0.27; 95% CI: 0.51, 0.03; beta: 0.03; P = .03), Russian ethnicity (B: 0.47; 95% CI: 0.20, 0.74; beta: 0.05; P = .001), higher body mass index (B: 0.06; 95% CI: 0.04, 0.08; beta: 0.08; P < .001), lower physical activity score (B: -0.02; 95% CI: -0.03, -0.002; beta: -0.03; P = .02), higher prevalence of diabetes mellitus (B: 0.42; 95% CI: 0.08, 0.76; beta: 0.03; P = .02), higher systolic blood pressure (B: 0.01; 95% CI: 0.01, 0.02; beta: 0.08; P < .001), fewer days with intake of fruits (B: -0.07; 95% CI: -0.12, -0.01; beta: 0.03; P = .01), lower blood concentration of bilirubin (B: -0.01; 95% CI: -0.02, -0.003; beta: -0.04; P = .008) and urea (B: -0.11; 95% CI: -0.17, -0.04; beta: -0.04; P = .003), worse best-corrected visual acuity (B: 0.64; 95% CI: 0.38, 0.90; beta: 0.13; P < .001), thicker central corneal thickness (B: 0.036; 95% CI: 0.033, 0.039; beta: 0.32; P < .001), higher anterior corneal refractive power (B: 0.11; 95% CI: 0.04, 0.18; beta: 0.05; P = .003), lower anterior chamber depth (B: -0.57; 95% CI: -0.83, -0.30; beta: -0.07; P < .001) (or lower prevalence of cataract surgery [B: -0.78; 95% CI: -1.44, -0.13; beta: -0.03; P = .02]), longer axial length (B: 0.30; 95% CI: 0.18, 0.42; beta: 0.07; P < .001), and higher prevalence of pseudoexfoliation (B: 1.08; 95% CI: 0.52, 1.63; beta: 1.01; P < .001). Measured IOP decreased by 0.36 mm Hg (95% CI: 0.33, 0.39) for each increase in central corneal thickness by 10 μm.

CONCLUSIONS

IOP was associated with a multitude of systemic and ocular parameters, the associations of which may be considered in defining the normal range of IOP.

Long Anterior Lens Zonules and Intraocular Pressure

Purpose

To investigate the relation between intraocular pressure (IOP) and the idiopathic long anterior zonule (LAZ) trait.

Methods

Patients presenting for primary eye care were examined for LAZ, identified as radially oriented zonular fibers with central extension >1.0 mm beyond the normal anterior lens insertion zone (estimated via slit lamp beam length). Ocular, systemic health, and lifestyle data were collected via comprehensive exam and questionnaire. Multivariate regression was used to assess the relationship between IOP (Goldmann) and LAZ.

Results

There were 2169 non-LAZ and 129 LAZ subjects (mean age: 49.8 ± 15.0 vs. 62.6 ± 10.2 years; 63.6% vs. 76.0% female; 83.2% vs. 91.5% African American). Right eyes with >trace LAZ (n = 59 of 110) had higher unadjusted mean IOP than control eyes (16.4 ± 3.3 vs. 15.0 ± 3.3 mm Hg, P = 0.005), and with control for numerous factors, LAZ eyes had an average IOP of approximately 1.3 ± 0.4 mm Hg higher (P = 0.003) than non-LAZ eyes. Final model covariates included sex (P = 0.001); spherical-equivalent refractive error (D; P < 0.0001); body mass index (kg/m²; P < 0.001); presence of diabetes (P < 0.001); having >high school education (P < 0.001); systolic blood pressure (mm Hg; P < 0.0001); being an ever smoker (P = 0.006); and having history of any site cancer (P = 0.01).

Conclusions

The LAZ trait, with potential prevalence near 2%, was associated with a higher IOP. This observation is consistent with the hypothesis that the trait is a marker for underlying mechanisms that elevate glaucoma risk.

Distribution of IOP measured with an air puff tonometer in a young population

Purpose

To determine the normal range of intraocular pressure (IOP) in the young and its association with certain corneal parameters using a non-contact device.

Methods

Subjects were selected from students of Mashhad University of Medical Sciences through stratified sampling. All participants had visual acuity testing, corneal imaging, a comprehensive slit-lamp examination by an ophthalmologist, and IOP measurement using a non-contact air-puff tonometer.

Results

Of the 1280 invitees, 1073 (83.8%) participated, and 1027 were eligible. Mean IOP was 16.38 mmHg [95% confidence interval (CI): 16.22–16.53] in the total sample, 16.14 mmHg (95% CI: 15.84–16.45) in men, and 16.48 mmHg (95% CI: 16.31–16.66) in women. There was a significant IOP difference between myopes and emmetropes (P = 0.031). Based on the multiple linear regression model, IOP associated directly with age and central corneal thickness (CCT), and inversely with corneal diameter, spherical equivalent (SE), and keratoconus. Based on standardized coefficients of the regression model, CCT and SE had the strongest association with IOP.

Conclusions

In the present study, we demonstrated the IOP distribution in a young population using a non-contact method. CCT and SE were strongly associated with IOP.

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.

Distribution of intraocular pressure, central corneal thickness and vertical cup-to-disc ratio in a healthy Iranian population: the Yazd Eye Study

PURPOSE

To determine the distribution of intraocular pressure (IOP), central corneal thickness (CCT) and vertical cup-to-disc ratio (VCDR) in the healthy Iranian population.

METHODS

This population-based, epidemiologic study evaluated Iranian aged 40-80 years, residing in Yazd, Iran, in 2010-2011. Eligible subjects were selected by cluster random sampling. Each participant underwent an interview and ophthalmologic examination including slit lamp examination, Goldmann applanation tonometry, binocular optic disc evaluation, stereoscopic fundus photography, ultrasonic pachymetry and visual field testing.

RESULTS

Of 2320 eligible individuals, 2098 subjects (response rate of 90.4%) participated in the study. One eye from 1159 subjects (total of 2262 normal eyes) were randomly selected for the purpose of the study. Mean age was 53.1 ± 9.6 years. Mean IOP, CCT and VCDR were 14.2 ± 2.5 mmHg, 543 ± 37 μm and 0.32 ± 0.14, respectively. Multiple regression analysis showed a significant correlation between IOP and age (regression coefficient = 0.02 per year, p = 0.015), CCT (regression coefficient = 0.02 per micron, p < 0.001), Spherical equivalent (regression coefficient = -0.15 per dioptre, p = 0.0.024) and smoking (regression coefficient = 0.89 higher for smokers, p = 0.009); it also showed a significant correlation between CCT with spherical equivalent (regression coefficient = 3.6 per dioptre, p = 0.002) and IOP (regression coefficient = 3.6 per mmHG, p < 0.001). There was no significant correlation with VCDR.

CONCLUSIONS

Mean IOP, CCT and VCDR were 14.2 ± 2.5 mmHg, 543 ± 35 μm and 0.32 ± 0.14, respectively, in healthy Iranians that is different from other ethnicities. It seems advisable to pay attention to ethnicity for interpretation of each person's variables.

Distribution of intraocular pressure and its determinants in an Iranian adult population

AIM

To determine the distribution of intraocular pressure (IOP) and its determinants in an Iranian population.

METHODS

In a cross-sectional survey, random cluster sampling was conducted from the 40-64 years old population of Shahroud, in the north of Iran. All participants had optometry and ophthalmic exams. IOP was determined using the Goldmann tonometry method and biometric components were measured.

RESULTS

Of the 6311 people selected for the study, 5190 (82.2%) participated. The mean age of the participants was 50.9±6.2y and 58.7% of them were female. Mean IOP was 12.87±2.27 mm Hg. In this study 0.3% of the participants had an IOP higher than 21 mm Hg. The multiple linear regression model revealed that sex (Coef=-0.30; 95% CI: -0.43 to -0.17), diabetes (Coef=0.43; 95% CI: 0.19 to 0.67), high systolic blood pressure (Coef=0.02; 95% CI: 0.01 to 0.02), high body mass index (BMI) (Coef=0.03; 95% CI: 0.01 to 0.04), higher education (Coef=0.02, 95% CI: 0.01 to 0.04), thicker central corneal thickness (Coef=0.01; 95% CI: 0.01 to 0.02), and myopic shift in spherical equivalent (Coef=-0.14; 95% CI: -0.18 to -0.10) significantly correlated with high IOP.

CONCLUSION

The IOP in this 40-64 years old population is low overall. In the north of Iran, average IOP is statistically significantly correlated with female sex, diabetes, higher BMI, systolic blood pressure, higher education, thicker cornea, and myopic refractive error.

Evaluation of the associations between changes in intraocular pressure and metabolic syndrome parameters: a retrospective cohort study in Japan

OBJECTIVE

The contributions of highly correlated cardiovascular risk factors to intraocular pressure (IOP) are not clear due to underlying confounding problems. The present study aimed to determine which metabolic syndrome parameters contribute to elevating IOP and to what extent.

DESIGN

Retrospective cohort study.

SETTING

A private healthcare centre in Japan.

PARTICIPANTS

Individuals who visited a private healthcare centre and underwent comprehensive medical check-ups between April 1999 and March 2009 were included (20,007 in the cross-sectional study and 15,747 in the longitudinal study).

PRIMARY AND SECONDARY OUTCOME MEASURES

Changes in IOP were evaluated in terms of ageing and changes in metabolic syndrome parameters. Pearson's correlation coefficients and mixed-effects models were used to examine the relationship of changes in IOP with ageing and changes in metabolic syndrome parameters in cross-sectional and longitudinal studies, respectively.

RESULTS

In the cross-sectional study, IOP was negatively correlated with age and positively correlated with waist circumference, high-density lipoprotein cholesterol (HDL-C) levels, triglyceride levels, systolic blood pressure (SBP), diastolic blood pressure (DBP) and fasting plasma glucose (FPG) levels. In the longitudinal multivariate analysis, the associated IOP changes were -0.12 (p<0.0001) mm Hg with male sex; -0.59 (p<0.0001) mm Hg with 10 years of ageing; +0.42 (p<0.0001) mm Hg with 1 mmol/L increase in HDL-C levels; +0.092 (p<0.0001) mm Hg with 1 mmol/L increase in triglyceride levels; +0.090 (p<0.0001) mm Hg with 10 mm Hg increase in SBP; +0.085 (p<0.0001) mm Hg with 10 mm Hg increase in DBP; and+0.091 (p<0.0001) mm Hg with 1 mmol/L increase in FPG levels.

CONCLUSIONS

Elevation of IOP was related to longitudinal worsening of serum triglyceride levels, blood pressure and FPG and improvement in serum HDL-C levels.

Associations with Intraocular Pressure in a Large Cohort: Results from the UK Biobank

PURPOSE

To describe the associations of physical and demographic factors with Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated intraocular pressure (IOPcc) in a British cohort.

DESIGN

Cross-sectional study within the UK Biobank, a large-scale multisite cohort study in the United Kingdom.

PARTICIPANTS

We included 110 573 participants from the UK Biobank with intraocular pressure (IOP) measurements available. Their mean age was 57 years (range, 40-69 years); 54% were women, and 90% were white.

METHODS

Participants had 1 IOP measurement made on each eye using the Ocular Response Analyzer noncontact tonometer. Linear regression models were used to assess the associations of IOP with physical and demographic factors.

MAIN OUTCOME MEASURES

The IOPg and IOPcc.

RESULTS

The mean IOPg was 15.72 mmHg (95% confidence interval [CI], 15.70-15.74 mmHg), and the mean IOPcc was 15.95 mmHg (15.92-15.97 mmHg). After adjusting for covariates, IOPg and IOPcc were both significantly associated with older age, male sex, higher systolic blood pressure (SBP), faster heart rate, greater myopia, self-reported glaucoma, and colder season (all P < 0.001). The strongest determinants of both IOPg and IOPcc were SBP (partial R(2): IOPg 2.30%, IOPcc 2.26%), followed by refractive error (IOPg 0.60%, IOPcc 1.04%). The following variables had different directions of association with IOPg and IOPcc: height (-0.77 mmHg/m IOPg; 1.03 mmHg/m IOPcc), smoking (0.19 mmHg IOPg, -0.35 mmHg IOPcc), self-reported diabetes (0.41 mmHg IOPg, -0.05 mmHg IOPcc), and black ethnicity (-0.80 mmHg IOPg, 0.77 mmHg IOPcc). This suggests that height, smoking, diabetes, and ethnicity are related to corneal biomechanical properties. The increase in both IOPg and IOPcc with age was greatest among those of mixed ethnicities, followed by blacks and whites. The same set of covariates explained 7.4% of the variability of IOPcc but only 5.3% of the variability of IOPg.

CONCLUSIONS

This analysis of associations with IOP in a large cohort demonstrated that some variables clearly have different associations with IOPg and IOPcc, and that these 2 measurements may reflect different biological characteristics.

IOP telemetry in the nonhuman primate

This review is focused on continuous IOP monitoring using telemetry systems in the nonhuman primate (NHP), presented in the context that IOP fluctuations at various timescales may be involved in glaucoma pathogenesis and progression. We use glaucoma as the primary framework to discuss how the dynamic nature of IOP might change with age, racial heritage, and disease in the context of glaucoma susceptibility and progression. We focus on the limited work that has been published in IOP telemetry in NHPs, as well as the emerging data and approaches. We review the ongoing efforts to measure continuous IOP, and the strengths, weaknesses and general pitfalls of the various approaches.

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.

The interactions of genes, age, and environment in glaucoma pathogenesis

Glaucoma, a progressive degenerative condition that results in the death of retinal ganglion cells, is one of the leading causes of blindness, affecting millions worldwide. The mechanisms underlying glaucoma are not well understood, although years of studies have shown that the largest risk factors are elevated intraocular pressure, age, and genetics. Eleven genes and multiple loci have been identified as contributing factors. These genes act by a number of mechanisms, including mechanical stress, ischemic/oxidative stress, and neurodegeneration. We summarize the recent advances in the understanding of glaucoma and propose a unified hypothesis for glaucoma pathogenesis. Glaucoma does not result from a single pathological mechanism, but rather a combination of pathways that are influenced by genes, age, and environment. In particular, we hypothesize that, in the presence of genetic risk factors, exposure to environment stresses results in an earlier age of onset for glaucoma. This hypothesis is based upon the overlap of the molecular pathways in which glaucoma genes are involved. Because of the interactions between these processes, it is likely that there are common therapies that may be effective for different subtypes of glaucoma.

The distribution of intraocular pressure and associated systemic factors in a Korean population: the Korea National Health and Nutrition Examination Survey

PURPOSE

To investigate the distribution of intraocular pressure (IOP) and its associated factors in a large Korean population based on the data from the nationwide cross-sectional survey.

METHODS

We obtained 2009-2010 data from the Korea National Health and Nutrition Examination Survey (KNHANES) (n = 17 901). After excluding individuals under 19 years of age, a total of 13 431 subjects were enrolled. All participants completed a comprehensive questionnaire and underwent an ocular examination including measurement of IOP by Goldmann applanation tonometry, as well as a systemic evaluation including blood pressure measurements, anthropometry and blood tests.

RESULTS

The mean IOP in the right eye was 13.99 ± 2.75 mmHg, and in the left eye, 13.99 ± 2.75 mmHg, representing no significant bilateral difference. There was, however, a significant difference between males (14.19 ± 2.78 mmHg) and females (13.79 ± 2.70 mmHg) (p < 0.001). Multiple regression analysis revealed that higher IOP was significantly correlated with male sex, higher myopic refractive error, higher body mass index, higher systolic blood pressure, higher fasting plasma glucose and higher total cholesterol (all p < 0.05). On the other hand, age, histories of smoking or migraine or cold hands/feet were not significantly correlated with IOP (all p > 0.05).

CONCLUSIONS

In the general Korean population, IOP increases with male sex and increasing myopia. Further, IOP is significantly correlated with systemic factors relating to cardiovascular disease and metabolic syndrome.

Human scleral structural stiffness increases more rapidly with age in donors of African descent compared to donors of European descent

PURPOSE

We tested the hypothesis that the variation of peripapillary scleral structural stiffness with age is different in donors of European (ED) and African (AD) descent.

METHODS

Posterior scleral shells from normal eyes from donors of European (n = 20 pairs; previously reported) and African (n = 9 pairs) descent aged 0 and 90 years old were inflation tested within 48 hours post mortem. Scleral shells were pressurized from 5 to 45 mm Hg and the full-field, 3-dimensional (3D) deformation of the outer surface was recorded at submicrometric accuracy using speckle interferometry (ESPI). Mean maximum principal (tensile) strain of the peripapillary and midperipheral regions surrounding the optic nerve head (ONH) were fit using a functional mixed effects model that accounts for intradonor variability, same-race correlation, and spatial autocorrelation to estimate the effect of race on the age-related changes in mechanical scleral strain.

RESULTS

Mechanical tensile strain significantly decreased with age in the peripapillary sclera in the African and European descent groups (P < 0.001), but the age-related stiffening was significantly greater in the African descent group (P < 0.05). Maximum principal strain in the peripapillary sclera was significantly higher than in the midperipheral sclera for both ethnic groups.

CONCLUSIONS

The sclera surrounding the ONH stiffens more rapidly with age in the African descent group compared to the European group. Stiffening of the peripapillary sclera with age may be related to the higher prevalence of glaucoma in the elderly and persons of African descent.

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.

Age-related changes in human peripapillary scleral strain

To test the hypothesis that mechanical strain in the posterior human sclera is altered with age, 20 pairs of normal eyes from human donors aged 20 to 90 years old were inflation tested within 48-h postmortem. The intact posterior scleral shells were pressurized from 5 to 45 mmHg, while the full-field three-dimensional displacements of the scleral surface were measured using laser speckle interferometry. The full strain tensor of the outer scleral surface was calculated directly from the displacement field. Mean maximum principal (tensile) strain was computed for eight circumferential sectors (45° wide) within the peripapillary and mid-peripheral regions surrounding the optic nerve head (ONH). To estimate the age-related changes in scleral strain, results were fit using a functional mixed effects model that accounts for intradonor variability and spatial autocorrelation. Mechanical tensile strain in the peripapillary sclera is significantly higher than the strain in the sclera farther away from the ONH. Overall, strains in the peripapillary sclera decrease significantly with age. Sectorially, peripapillary scleral tensile strains in the nasal sectors are significantly higher than the temporal sectors at younger ages, but the sectorial strain pattern reverses with age, and the temporal sectors exhibited the highest tensile strains in the elderly. Overall, peripapillary scleral structural stiffness increases significantly with age. The sectorial pattern of peripapillary scleral strain reverses with age, which may predispose adjacent regions of the lamina cribrosa to biomechanical insult. The pattern and age-related changes in sectorial peripapillary scleral strain closely match those seen in disk hemorrhages and neuroretinal rim area measurement change rates reported in previous studies of normal human subjects.

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.

Innervation pattern of the preocular human central retinal artery

The central retinal artery (CRA) is the main vessel for inner retinal oxygen and nutrition supply. While the intraocular branches lack autonomic innervation, the innervation pattern of the extra-ocular part of this vessel along its course within the optic nerve is poorly investigated. This part however is essential for maintenance of retinal blood supply, in physiological and pathological conditions. Therefore, the aim of this study was the characterization of the autonomic innervation of the preocular CRA in humans with morphological methods. Meeting the Declaration of Helsinki, eyes of body or cornea donors were processed for single or double immunohistochemistry against tyrosine hydroxilase (TH), dopamine-β-hydroxylase (DBH), choline acetyl-transferase (ChAT), vesicular acetylcholine transporter (VAChT), neuronal nitric oxide synthase (nNOS), calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP), and cytochemistry for NADPH-diaphorase (NADPH-d). For documentation, light-, fluorescence-, and confocal laser-scanning microscopy were used. TH and DBH immunoreactive nerve fibres were detected in the CRA vessel wall, although a distinct perivascular plexus was missing. Further, nerve fibres immunoreactive for ChAT and VAChT were found, while CGRP, SP, and VIP were not detected. NADPH-d staining revealed scattered nerve fibres in the adventitia of the CRA and in close vicinity; however, nNOS-immunostaining could not confirm this finding. The CRA receives adrenergic and cholinergic innervations, indicating sympathetic and parasympathetic components, respectively. Remarkably, a peptidergic primary afferent innervation was missing. Since clinical results suggest an autoregulation of intraretinal vessels, further studies are needed to clarify the impact of CRA innervation for retinal perfusion.

Distribution and associations of intraocular pressure in indigenous Australians within central Australia: the Central Australian Ocular Health Study

PURPOSE

To determine the distribution and associations of intraocular pressure (IOP) among the indigenous Australian population living in central Australia.

DESIGN

Clinic-based cross-sectional study.

PARTICIPANTS

1884 individuals living in one of 30 remote communities within the statistical local area of 'Central Australia'. This equated to 36% of those aged ≥20 years and 67% of those aged ≥40 years within this district.

METHODS

Participants aged 20 years or over were recruited as they presented to the eye clinic at each remote community. Of those recruited into the study, 1060 underwent IOP measurement using either a Perkins tonometer (Haag-Streit, Koeniz, Switzerland) or an ICare tonometer (Tiolat Oy, Helsinki, Finland) depending on the availability of equipment. Central corneal thickness (CCT) was also measured using ultrasound pachymetry.

MAIN OUTCOME MEASURES

The distribution and associations of IOP from the right eye of each participant is presented.

RESULTS

Mean IOP was 12.8 mmHg (SD 3.2 mmHg) and CCT was 512 µm (SD 36 µm). IOP was strongly associated with CCT (r(2) = 0.14, t = 3.87; P < 0.0001), showing an increase of 0.4 mmHg with every 10 µm increase in CCT. Furthermore, IOP was strongly associated with age, decreasing by 1.9 mmHg for every decade increase in age, but only for eyes with a CCT above the mean.

CONCLUSION

  IOP of indigenous Australians is lower than any other racial group previously published. This may relate to the low CCT readings found among this population. Clinicians will need to bear this in mind when examining indigenous Australians and make appropriate allowances for the measured IOP.

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.

Prevalence and risk factors for primary open-angle glaucoma in a rural northeast China population: a population-based survey in Bin County, Harbin

PURPOSE

To estimate the prevalence and associated risk factors of primary open-angle glaucoma (POAG) in a rural population in northeast China.

METHODS

A population-based survey was conducted within Bin County, Harbin of northeast China. Glaucoma was diagnosed using International Society of Geographical and Epidemiological Ophthalmology criteria. All the subjects underwent a complete ophthalmic examination.

RESULTS

A total of 4956 (86.0%) of 5762 subjects aged 40 years or older were examined. The mean intraocular pressure (IOP) of right eyes was 14.0 (95% confidence interval (CI), 13.9 to 14.1) mm Hg. The prevalence of POAG was 0.71% (35/4956, 95% CI, 0.47 to 0.93). In these POAG subjects, 17 (48.6%) had elevated IOP >21 mm Hg in either eye, 3 (8.8%) participants had been treated by laser trabeculoplasty or trabeculectomy and were known to have POAG. Vision impairment to varying degrees was present in 20 subjects (58.8%) with 1 subject blind in both eyes and 8 subjects blind in one eye. On multivariate analysis, age, family history of glaucoma, systemic hypertension, and IOP were regarded as significant independent risk factors.

CONCLUSIONS

POAG is a disease of serious consequence and of low diagnosis and treatment rates in rural northeast China. Age, family history of glaucoma, systemic hypertension, and IOP remain as significant independent risk factors for POAG.

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.

[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.

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.

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.