Intraocular pressure difference in Goldmann applanation tonometry versus Perkins hand-held applanation tonometry in overweight patients

Gravitational effects on carotid and jugular characteristics in graded head-up and head-down tilt

Altered gravity affects hemodynamics and blood flow in the neck. At least one incidence of jugular venous thrombosis has been reported in an astronaut on the International Space Station. This investigation explores the impact of changes in the direction of the gravitational vector on the characteristics of the neck arteries and veins. Twelve subjects underwent graded tilt from 45° head-up to 45° head-down in 15° increments in both supine and prone positions. At each angle, the cross-sectional area of the left and right common carotid arteries (ACCA) and internal jugular veins (AIJV) were measured by ultrasound. Internal jugular venous pressure (IJVP) was also measured by compression sonography. Gravitational dose-response curves were generated from experimental data. ACCA did not show any gravitational dependence. Conversely, both AIJV and IJVP increased in a nonlinear fashion with head-down tilt. AIJV was significantly larger on the right side than the left side at all tilt angles. In addition, IJVP was significantly elevated in the prone position compared with the supine position, most likely because of raised intrathoracic pressure while prone. Dose-response curves were compared with existing experimental data from parabolic flight and spaceflight studies, showing good agreement on an acute timescale. The quantification of jugular hemodynamics as a function of changes in the gravitational vector presented here provides a terrestrial model to reference spaceflight-induced changes, contributes to the assessment of the pathogenesis of spaceflight venous thromboembolism events, and informs the development of countermeasures.NEW & NOTEWORTHY Flow stasis and thrombosis have been identified in the jugular vein during spaceflight. We measured the area and pressure of the internal jugular vein and the area of the common carotid artery in graded head-up and head-down tilt. Experimental data are used to generate gravitational dose-response curves for the measured variables, demonstrating that jugular vein area and pressure exhibit a nonlinear response to altered gravity. Gravitational dose-response curves show good agreement with spaceflight and parabolic flight studies.

Association of Metabolic Syndrome With Glaucoma and Ocular Hypertension in a Midwest United States Population

PRCIS

For patients with glaucoma, metabolic syndrome was associated with higher intraocular pressure and greater central corneal thickness. Patients with metabolic syndrome were more likely to have ocular hypertension.

PURPOSE

The purpose of this study was to determine whether glaucomatous optic neuropathy, also known as glaucoma, and ocular hypertension are more likely to occur in patients with metabolic syndrome.

PATIENTS AND METHODS

Patients in Olmsted County, MN, were identified as having metabolic syndrome based on diagnosis codes, laboratory values, and/or medication use to meet 3 or more of the 5 standard criteria for diagnosing metabolic syndrome: systemic hypertension, hyperglycemia, hypertriglyceridemia, reduced high-density lipoprotein cholesterol, and central adiposity defined by increased body mass index. Patients with glaucoma, including primary open angle, low tension, pigment dispersion, and pseudoexfoliation, were identified using diagnostic codes. The charts of patients with glaucoma were individually reviewed to collect visual acuity, intraocular pressure, cup to disc ratio, central corneal thickness, visual field mean deviation, retinal nerve fiber layer thickness, and treatment of intraocular pressure. Patients with ocular hypertension were separately identified and similarly evaluated.

RESULTS

For patients with glaucoma, those with metabolic syndrome had higher intraocular pressure and greater central corneal thickness compared with those without metabolic syndrome. After adjustment for central corneal thickness, there was no longer a significant difference in intraocular pressure between groups. Metabolic syndrome was also associated with the diagnosis of ocular hypertension, and although central corneal thickness trended higher in patients with metabolic syndrome, it did not attain statistical significance.

CONCLUSION

In Olmsted County, though metabolic syndrome was associated with ocular hypertension and higher intraocular pressure in patients with glaucoma, the results were likely related to a thicker central corneal in this patient population.

Inter-eye correlation analysis of 24-h IOPs and glaucoma progression

Purpose

To determine whether 24-h IOP monitoring can be a predictor for glaucoma progression and to analyze the inter-eye relationship of IOP, perfusion, and progression parameters.

Methods

We extracted data from manually drawn IOP curves with HIOP-Reader, a software suite we developed. The relationship between measured IOPs and mean ocular perfusion pressures (MOPP) to retinal nerve fiber layer (RNFL) thickness was analyzed. We determined the ROC curves for peak IOP (T_max), average IOP(T_avg), IOP variation (IOP_var), and historical IOP cut-off levels to detect glaucoma progression (rate of RNFL loss). Bivariate analysis was also conducted to check for various inter-eye relationships.

Results

Two hundred seventeen eyes were included. The average IOP was 14.8 ± 3.5 mmHg, with a 24-h variation of 5.2 ± 2.9 mmHg. A total of 52% of eyes with RNFL progression data showed disease progression. There was no significant difference in T_max, T_avg, and IOP_var between progressors and non-progressors (all p > 0.05). Except for T_avg and the temporal RNFL, there was no correlation between disease progression in any quadrant and T_max, T_avg, and IOP_var. Twenty-four-hour and outpatient IOP variables had poor sensitivities and specificities in detecting disease progression. The correlation of inter-eye parameters was moderate; correlation with disease progression was weak.

Conclusion

In line with our previous study, IOP data obtained during a single visit (outpatient or inpatient monitoring) make for a poor diagnostic tool, no matter the method deployed. Glaucoma progression and perfusion pressure in left and right eyes correlated weakly to moderately with each other.

Predicting intraocular pressure using systemic variables or fundus photography with deep learning in a health examination cohort

The purpose of the current study was to predict intraocular pressure (IOP) using color fundus photography with a deep learning (DL) model, or, systemic variables with a multivariate linear regression model (MLM), along with least absolute shrinkage and selection operator regression (LASSO), support vector machine (SVM), and Random Forest: (RF). Training dataset included 3883 examinations from 3883 eyes of 1945 subjects and testing dataset 289 examinations from 289 eyes from 146 subjects. With the training dataset, MLM was constructed to predict IOP using 35 systemic variables and 25 blood measurements. A DL model was developed to predict IOP from color fundus photographs. The prediction accuracy of each model was evaluated through the absolute error and the marginal R-squared (mR2), using the testing dataset. The mean absolute error with MLM was 2.29 mmHg, which was significantly smaller than that with DL (2.70 dB). The mR2 with MLM was 0.15, whereas that with DL was 0.0066. The mean absolute error (between 2.24 and 2.30 mmHg) and mR2 (between 0.11 and 0.15) with LASSO, SVM and RF were similar to or poorer than MLM. A DL model to predict IOP using color fundus photography proved far less accurate than MLM using systemic variables.

Metabolic Syndrome Is Associated With Ocular Hypertension and Glaucoma

Glaucoma remains the world's leading cause of irreversible blindness and though intraocular pressure (IOP) is the most prevalent risk factor and only reliable therapeutic target, a number of systemic disease associations have been reported. Metabolic syndrome (MetS) is a constellation of findings that includes systemic hypertension, abdominal obesity, glucose intolerance, and dyslipidemia. MetS is becoming increasingly common worldwide, with prevalence up to 40% in some countries. Not only is MetS a significant cause of morbidity, but it is also associated with an increase in all-cause mortality. Reports have been conflicting regarding the association of individual components of MetS, including systemic hypertension and diabetes, with elevated IOP or glaucoma. However, though limitations in the existing literature are present, current evidence suggests that MetS is associated with IOP as well as glaucoma. Additional studies are needed to clarify this association by incorporating additional metrics including assessment of central corneal thickness as well as optic nerve structure and function. Future studies are also needed to determine whether lifestyle modification or systemic treatment of MetS could reduce the incidence or progression of glaucoma.

Comparative Assessment of The Goldmann Applanation and Noncontact Tonometers in Intraocular Pressure Measurements in a Sample of Glaucoma Patients in the Cape Coast Metropolis, Ghana

Objectives:

The objective of the study was to explore the usage of the Goldmann applanation tonometry and noncontact tonometry interchangeably in the measurement of intraocular pressure (IOP) in glaucoma patients.

Materials and Methods:

The study involved 441 clinically diagnosed glaucoma patients receiving care at a referral facility. IOP measurements were obtained using both the Noncontact tonometer and Goldmann applanation tonometer The repeatability of the measures was analyzed by comparing the repeated measures of the devices using paired t-test and calculating the correlation coefficient. A Bland–Altman analysis was used to determine the limits of agreement between the two procedures.

Results:

There were 271 (61.5%) males and 170 (38.5%) females and their age ranged from 18 to 73 years (mean age = 49.37; standard deviation ± 14.81 years). The findings of the study showed significantly lower readings (P < 0.001) of the GAT (right eye = 17.40 ± 7.48 mmHg; left eye = 16.80 ± 7.49 mmHg) compared to the NCT (right eye = 20.15 ± 8.30 mmHg; left eye = 19.74 ± 8.31 mmHg). There was a strong positive correlation between the GAT and NCT findings in the right eye (r = 0.871, n = 441, P < 0.001) and in the left eye (r = 0.887, n = 441, P < 0.001). There was a wide limit of agreement between NCT and GAT measurements.

Conclusion:

There was statistically significant higher measures obtained with NCT than the GAT but did not exceed the allowable inter-device difference. There was a strong positive correlation between GAT and NCT measurements. However, it is strongly recommended that these devices are not used interchangeably in the monitoring of IOP in glaucoma due to the wide range of limits of agreement.

Evaluation of Changes in Intraocular Pressure with a Noncontact Tonometer in Healthy Volunteers

Purpose

We investigated whether or not intrasession or intersession fluctuations in intraocular pressure occur in healthy people using a noncontact tonometer.

Materials and Methods

A noncontact tonometer was used to measure intraocular pressure in the bilateral eyes of healthy subjects for 5 consecutive days. Paired t-tests and one- and two-way repeated-measures analyses of variance were performed for the acquired data. A p-value <0.05 was considered to indicate statistical significance.

Results

Eighty eyes of 40 healthy subjects were enrolled in the study. On day 1, intraocular pressure was significantly higher in the right eye than in the left eye (P = 0.014). The one-way repeated-measures analysis of variance revealed that intraocular pressure in the left eye was significantly lower on day 1 than on days 2 to 5 (P = 0.000–0.018); however, there were no significant differences among intraocular pressures measured on days 1 to 5 in the right eye. The two-way repeated-measures analysis of variance revealed no significant difference in intraocular pressure between the right and left eyes (P = 0.913).

Conclusion

Although measurements using the noncontact tonometer were relatively stable, intraocular pressure was high on day 1.

Systemic factors associated with intraocular pressure among subjects in a health examination program in Japan

Background

To elucidate the possible effect of various systemic factors on intraocular pressure (IOP) using a dataset from a health examination program database in Japan.

Methods

This cross-sectional study included 1569 subjects selected from the 2287 subjects who comprised the database. Various systemic parameters including age, sex, height, body weight, waist circumference, percent body fat, blood pressure (BP), pulse rate, body mass index, 28 blood examination values, intimal medial thicknesses of both carotid arteries, and intraocular pressure (IOP) values measured by non-contact tonometry in both eyes were collected. The possible correlation between the IOP and other parameters was assessed initially by univariate analyses followed by multivariate analyses.

Results

Stepwise multivariate analyses, which included all parameters extracted by the univariate analyses (p<0.1) and sex, identified the same six parameters as indicators of the IOP values for each right and left IOP model. Among the parameters, age (r = -0.05 and -0.04/year for right and left IOPs, respectively) was associated negatively and the percent body fat (r = 0.06 and 0.05/%), systolic BP (r = 0.02 and 0.03/mmHg), pulse rate (r = 0.03 and 0.03/counts/minutes), albumin (r = 1.12 and 1.00/g/dL), and hemoglobin A1c (r = 0.38 and 0.44/%) were associated positively with the IOP in each eye.

Conclusions

Older age was associated with low IOP, while factors reflecting the metabolic syndrome were associated with high IOP in our study population.

Systematic bias in real-world tonometry readings based on laterality?

AIMS

In research settings, the first eye examined tends to have a higher intraocular pressure (IOP) than the second. We sought to verify whether clinicians in Yorkshire, UK, measure IOP in right eyes before left and whether such behavioural factors affect IOP readings at the population level.

METHODS

We observed 128 IOP measurements taken by 28 ophthalmologists using Goldmann applanation tonometry (GAT) over a 4-month period in 2018, recording which eye was examined first. All IOP measurements on electronic patient records for Leeds Teaching Hospitals NHS Trust, UK, between January 2002 and June 2017 were extracted, yielding IOP readings for 562,360 eyes, analysed for evidence of systematic bias in IOP measurement.

RESULTS

Right eye IOP was measured before left in 112/128 observations (87.5% (95% CI: 75.2%-94.2%)). For IOP measured by GAT, there was no statistically significant difference (p = 0.121) between right and left eye IOP (mean IOP 16.95 and 16.96 mmHg, respectively). Even values of IOP were reported more frequently than odd values (136,503/214,628 (63.6%) were even). Identical IOP readings for both eyes were recorded in 124,392/254,380 patients (48.9%) who had both eyes measured.

CONCLUSIONS

Our study found no IOP difference based on laterality, but strong evidence of certain trends associated with IOP measurement by GAT, such as a preference for even values and the same IOP being recorded for both left and right eyes. Such effects may be explained by behavioural aspects of GAT and suggest that there are substantial opportunities for improvement in the way GAT is utilised in real world settings.

Factors associated with fluctuations in repeated measurements of intraocular pressure using the Goldmann applanation tonometer in Japanese patients with primary open-angle glaucoma

Purpose

The aim of this study was to determine whether fluctuations in intraocular pressure (IOP) occur as a result of the order of IOP measurements or successive IOP measurements in patients with glaucoma and, if so, identify the factors causing these fluctuations.

Patients and methods

Four hundred twenty-eight eyes of 214 Japanese patients with primary open-angle glaucoma (POAG) were enrolled. Patients treated with beta-blockers or prostaglandin analogs alone were included. Additionally, in the IOP measurements by noncontact tonometer, the same cases of IOP of the right and left eyes prior to this study were included in this study. Four successive IOP measurements were carried out using a Goldmann applanation tonometer as follows: IOP was measured in the first eye (right or left) and then in the fellow eye and IOP was again measured in the first eye and then in the fellow eye. Repeated-measures analysis of variance was used to test the differences in IOP between successive measurements. Generalized linear mixed models were used to test differences in IOP measurements between the right and the left eyes on repeated applanation tonometry and according to the order of measurement. Conditional binomial logistic regression analysis was used to identify factors associated with fluctuating repeated applanation tonometry measurements. A P-value of <0.05 was considered statistically significant.

Results

IOP values decreased significantly according to the number of measurements (13.8–13.0; P<0.001–0.036, respectively). There was no significant difference in IOP measurements between the right and left eyes. The first IOP measurement was significantly higher than the fourth measurement (P=0.038); however, there was no significant difference between other combinations. The use of a prostaglandin analog was the only significant contributor to fluctuating IOP measurements (P=0.002).

Conclusion

IOP measured in the first eye, either right or left, was higher than that measured in the fellow eye in Japanese patients with POAG. The use of a prostaglandin analog may be associated with fluctuating IOP on repeated applanation tonometry.

The Association between Adiposity and the Risk of Glaucoma: A Meta-Analysis

Purpose

This meta-analysis was conducted to determine the potential association between adiposity and glaucoma incidence.

Materials and Methods

A comprehensive literature search was performed in PubMed and ISI Web of Science. A meta-analysis was conducted using STATA software.

Results

Fifteen eligible studies involving 2,445,980 individuals were included to investigate the association between adiposity and glaucoma incidence. The relative risks (RRs) were pooled with 95% confidence intervals (CI) by using a random-effects model. The pooled RR between adiposity and elevated intraocular pressure (IOP) was 1.73 (95% CI, 1.18–2.54), whereas that between adiposity and open-angle glaucoma (OAG) was 0.97 (95% CI, 0.83–1.13). The pooled RR between abdominal adiposity and glaucoma was 1.28 (95% CI, 1.15–1.41), whereas that between general adiposity and glaucoma was 1.09 (95% CI, 0.87–1.37). Results of subgroup analysis by sex indicated the association between adiposity and glaucoma in the female group (RR, 1.31; 95% CI, 1.05–1.64), but not in the male group (RR, 1.11; 95% CI, 0.77–1.60). The pooled RR of cohort studies and cross-sectional studies were 1.00 (95% CI, 0.84–1.20) and 1.22 (95% CI, 0.89–1.66), respectively.

Conclusions

Adiposity has a higher risk of elevated IOP, and abdominal adiposity has a positive association with glaucoma, especially in female patients.

Associations with intraocular pressure across Europe: The European Eye Epidemiology (E3) Consortium

Raised intraocular pressure (IOP) is the most important risk factor for developing glaucoma, the second commonest cause of blindness globally. Understanding associations with IOP and variations in IOP between countries may teach us about mechanisms underlying glaucoma. We examined cross-sectional associations with IOP in 43,500 European adults from 12 cohort studies belonging to the European Eye Epidemiology (E³) consortium. Each study conducted multivariable linear regression with IOP as the outcome variable and results were pooled using random effects meta-analysis. The association of standardized study IOP with latitude was tested using meta-regression. Higher IOP was observed in men (0.18 mmHg; 95 % CI 0.06, 0.31; P = 0.004) and with higher body mass index (0.21 mmHg per 5 kg/m²; 95 % CI 0.14, 0.28; P < 0.001), shorter height (−0.17 mmHg per 10 cm; 95 % CI –0.25, −0.08; P < 0.001), higher systolic blood pressure (0.17 mmHg per 10 mmHg; 95 % CI 0.12, 0.22; P < 0.001) and more myopic refraction (0.06 mmHg per Dioptre; 95 % CI 0.03, 0.09; P < 0.001). An inverted U-shaped trend was observed between age and IOP, with IOP increasing up to the age of 60 and decreasing in participants older than 70 years. We found no significant association between standardized IOP and study location latitude (P = 0.76). Novel findings of our study include the association of lower IOP in taller people and an inverted-U shaped association of IOP with age. We found no evidence of significant variation in IOP across Europe. Despite the limited range of latitude amongst included studies, this finding is in favour of collaborative pooling of data from studies examining environmental and genetic determinants of IOP in Europeans.

The interaction between intracranial pressure, intraocular pressure and lamina cribrosal compression in glaucoma

This review examines some of the biomechanical consequences associated with the opposing intraocular and intracranial forces. These forces compress the lamina cribrosa and are a potential source of glaucomatous pathology. A difference between them creates a displacement force on the lamina cribrosa. Increasing intraocular pressure and/or decreasing intracranial pressure will increase the trans-lamina cribrosa pressure difference and the risk of its posterior displacement, canal expansion and the formation of pathological cupping. Both intraocular pressure and intracranial pressure can be elevated during a Valsalva manoeuvre with associated increases in both anterior and posterior lamina cribrosa loading as well as its compression. Any resulting thinning of or damage to the lamina cribrosa and/or retinal ganglion cell axons and/or astrocyte and glial cells attached to the matrix of the lamina cribrosa and/or reduction in blood flow to the lamina cribrosa may contribute to glaucomatous neuropathy. Thinning of the lamina cribrosa reduces its stiffness and increases the risk of its posterior displacement. Optic nerve head posterior displacement warrants medical or surgical lowering of intraocular pressure; however, compared to intraocular pressure, the trans-lamina cribrosa pressure difference may be more important in pressure-related pathology of the optic nerve head region. Similarly important could be increased compression loading of the lamina cribrosa. Reducing participation in activities which elevate intraocular and intracranial pressure will decrease lamina cribrosa compression exposure and may contribute to glaucoma management and may have prognostic significance for glaucoma suspects.

Intradevice and Interdevice Agreement Between a Rebound Tonometer, Icare PRO, and the Tonopen XL and Kowa Hand-held Applanation Tonometer When Used in the Sitting and Supine Position

PURPOSE

The aim of the study was to investigate the agreement between a new portable tonometer, Icare PRO, and the Tonopen XL and Kowa hand-held applanation tonometers (HAT).

METHODS

The right eyes of 127 healthy subjects were enrolled. Intraocular pressure (IOP) was measured in both sitting and supine positions using the Icare PRO, Tonopen XL, and Kowa HAT tonometers. The repeatability of the IOP measurements was evaluated by calculating intraclass correlation coefficients. Between-method agreements of tonometer measurements were evaluated using Bland-Altman analysis.

RESULTS

Intradevice agreement: The intraclass correlation coefficients (sitting, supine) of Icare PRO, Tonopen XL, and Kowa HAT were (0.863, 0.656), (0.845, 0.819), and (0.957, 0.956), respectively.Interdevice agreement: The Bland-Altman analysis revealed that, in the sitting position, the mean differences between Icare PRO and Tonopen XL, and between Icare PRO and Kowa HAT were -0.43 and 0.43 mm Hg, respectively (95% limits of agreement: -6.24 to 5.34 mm Hg, -4.04 to 4.90 mm Hg). In the supine position, the corresponding mean differences were -0.88 and 0.14 mm Hg (95% limits of agreement: -5.66 to 3.91 mm Hg, -4.06 to 4.33 mm Hg). IOP differences between Icare PRO and the other tonometers were unaffected by central corneal thickness.

CONCLUSIONS

The repeatability of Icare PRO was slightly lower in the supine position than in the sitting position. Although Icare PRO underestimated IOP values in eyes with higher IOP when compared with Tonopen XL and Kowa HAT in both positions, we observed good interdevice agreement between Icare PRO and both Tonopen XL and Kowa HAT.

The Association Between Primary Open Angle Glaucoma and Clustered Components of Metabolic Syndrome

Purpose :

There is conflicting evidence whether components of metabolic syndrome (MetS) increase or decrease the risk of primary open-angle glaucoma (POAG). The aim of the present study was to determine the association between metabolic syndrome and primary open-angle glaucoma.

Methods :

A total of 200 participants comprising 100 controls and 100 patients with POAG documented by clinical tests and examined by an experienced ophthalmologist using standard ophthalmologic equipment were included in the study. MetS was defined and based on ATP III criteria and POAG was defined by the criteria of the International Society of Geographic and Epidemiological Ophthalmology (ISGEO). The data were entered into the SPSS software and analyzed.

Results :

The prevalence of MetS in the glaucoma group was 53% in comparison to 38% in the control group (p=0.037). MetS was associated with an increased odds ratio for an IOP higher than 21 mmHg (OR: 1.72; 95% CI 1.03-2.79; p=0.034). The mean IOP was 24.91±4.29 mmHg in the patients without MetS, and 27.23±4.81 mmHg in those with MetS (p=0.027). The mean values of CCT were 603.64±63.16 µm in MetS patients and 579.27±72.87 µm in controls (p=0.018).

Conclusion :

Data showed an increased prevalence of components of metabolic syndrome in patients with glaucoma. The mechanisms underlying these associations need to be established in future studies. Our results support the recommendation that patients with metabolic syndrome undergo regular ophthalmological exams to monitor for the onset or progression of glaucoma.

Correlation between intraocular pressure and body mass index in the seated and supine positions

PURPOSE

Examine the relationship between intraocular pressure (IOP) and body mass index (BMI) in the seated and supine positions.

PATIENTS AND METHODS

A prospective observational study was conducted in which the IOP was measured with a Tono-Pen (Reichert Inc., Depew, NY) in seated and supine positions in eligible participants with a wide range of BMI (18 to 70 kg/m). The paired t test was used to compare seated to supine IOP. Stepwise regression analyses were used to investigate the correlation between IOP and BMI at these positions after adjusting for confounding variables of increased IOP, including age, race, mean arterial blood pressure, and central corneal thickness (μm).

RESULTS

The mean sitting IOP (16.3±2.9 mm Hg) was statistically lower than the mean supine IOP (17.7±3.1 mm Hg; P<0.0001). For each 10 unit increase in BMI, there was an increase of 0.55±0.23 mm Hg (P=0.0184) in IOP in the seated position and an increase of 0.49±0.24 mm Hg in IOP in the supine position (P=0.0409). BMI did not have a significant effect on the amount of increase in IOP observed in changing from the seated to supine position.

CONCLUSIONS

Higher BMI is correlated with higher IOP in both the seated and supine positions. However, BMI has no significant effect on the amount of increase in IOP observed in changing from the seated to supine position.

Fundamentals and Advances in Tonometry

According to the World Health Organization, glaucoma is the leading cause of irreversible blindness worldwide. Although intraocular pressure (IOP) is not considered any more to be a defining feature of the disease, its lowering remains the only treatment option for glaucoma. Therefore, accurate and precise measurement of IOP is the cornerstone of glaucoma. Intraocular pressure is a highly dynamic physiological parameter with individual circadian rhythms. The main limitation of current tonometry methods remains the static and mostly office-based nature of their measurements. This review provides a brief historical overview on tonometry and discusses current tonometry instruments. In recent years, approaches to 24-hour IOP monitoring have been introduced, and there is hope that they may become part of routine clinical management in the future.

Insulin resistance is associated with intraocular pressure elevation in a non-obese Korean population

Based on reports of an association between elevated intraocular pressure (IOP) and metabolic syndrome (MetS), and the major role of insulin resistance (IR) in MetS pathogenesis, a positive association between IOP and IR has been hypothesized. Although Asian populations tend to have lower body mass indices (BMIs) than Western populations, they tend to have a higher risk of developing MetS. This study examined the hypothesis that the association between IOP and IR differs by obesity status in an Asian population, by examining a nationally representative sample of South Korean adults. Data collected from 4,621 South Korean adults regarding demographic, lifestyle, and laboratory parameters by the 2010 Korea National Health and Nutrition Examination Survey were subjected to linear regression analysis to evaluate the relationship between IOP and metabolic profiles. After adjusting for confounding factors, the data were subjected to multiple linear regression analysis to examine the association between IR, as measured by the homeostasis model assessment of insulin resistance (HOMA-IR), and IOP. Obesity was defined as BMI≥27.5 kg/m2, and the subjects were divided into obese vs. non-obese groups for investigation of the association between IR and IOP according to obesity status. IOP was found to correlate with fasting blood sugar, total cholesterol, insulin, and HOMA-IR values in non-obese men; and with BMI, waist circumference, triglycerides, total cholesterol, HOMA-IR, and low-density lipoprotein cholesterol values in non-obese women, whereas no association between IOP and IR was found in obese men or women. IOP was significantly associated with IR in non-obese men and women after adjusting for age, and in non-obese men after adjusting for age, BMI, and lifestyle and demographic factors. These findings indicate that a positive and independent relationship exists between IOP and IR in non-obese individuals only, suggesting that other factors likely contribute to IOP elevation in obese individuals.

Intraocular pressure curves of untreated glaucoma suspects and glaucoma patients in sitting and lateral decubitus positions using the goldmann applanation tonometer

PURPOSE

Evaluation of data obtained during diurnal intraocular pressure (IOP) measurements by means of the Goldmann Applanation tonometer in sitting and lateral decubitus positions.

PATIENTS AND METHODS

Retrospective cohort study of 41 consecutive untreated subjects (82 eyes) with ocular hypertension or suspicious discs. The IOP was measured by Goldmann Applanation tonometer in sitting position at 9 AM, 12 AM, 3 PM, and 6 PM; and in right lateral decubitus position around 12:15 PM.

RESULTS

In the right eye (RE) mean peak IOP was 22.19±4.68 mm Hg. In the left eye (LE) peak mean IOP was 22.19±3.8 mm Hg. In 91.5% of the eyes, the IOP increased in the lateral decubitus position. The average change in the RE was an increment of 4.22±2.67 mm Hg (P<0.001) and in the LE an increment of 3.51±3.11 (P<0.001). This increment was significantly higher in the dependent eye (i.e., lower eye) (P=0.049). Sixty-seven percent of eyes had a positional elevation of IOP between 2 and 5 mm Hg and 23.2% of eyes had IOP elevation between 6 and 12 mm Hg. In the great majority of the eyes (80.5% RE and 78% LE) the lateral decubitus IOP was greater than maximal diurnal sitting IOP.

CONCLUSIONS

The IOP in the lateral decubitus position was significantly higher than the mean maximal diurnal sitting IOP. Over 20% of the patients had an IOP increase of ≥6 mm Hg when lying down. Timely identification of patients with excessive postural elevation of IOP could affect their management and prevent visual fields loss.

Intraocular pressure of supine patients using four portable tonometers

PURPOSE

To evaluate the congruity of intraocular pressure (IOP) measurements from supine patients, which were obtained using four portable tonometers.

METHODS

Intraocular pressure measurements were obtained from the right eye of 72 supine patients. We used the iCare (Tiolat Oy, Helsinki, Finland) rebound tonometer, the Diaton (BICOM Inc., Long Beach, NY) transpalpebral tonometer, the Tonopen XL (Reichert inc., Depew, NY), and a Kowa hand-held applanation tonometer (HAT; Kowa Company, Ltd., Nagoya, Japan). Relationships between mean IOPs were evaluated using Pearson correlation coefficients, and the mean differences between tonometers, using one-way analysis of variance followed by Tukey-Kramer post-hoc analysis. Levels of agreement were evaluated using Bland-Altman analysis.

RESULTS

The mean IOPs (mean ± SD) were 18.2 ± 3.5 mm Hg for iCare, 14.8 ± 3.4 mm Hg for Diaton, 16.7 ± 3.7 mm Hg for Tonopen XL, and 16.8 ± 2.8 mm Hg for Kowa HAT. Pearson correlation coefficients between iCare, Tonopen XL, and Kowa HAT ranged from 0.382 to 0.577, whereas those between Diaton and other tonometers ranged from 0.041 to 0.286. Post-hoc analysis indicated significant differences between all pairs except Tonopen XL and Kowa HAT. The mean difference between measurements from iCare and Diaton was 3.39 ± 3.39 mm Hg; iCare and Tonopen XL, 1.47 ± 3.52 mm Hg; iCare and Kowa HAT, 1.49 ± 2.90 mm Hg; Diaton and Tonopen XL, -1.93 ± 4.90 mm Hg; Diaton and Kowa HAT, -1.90 ± 4.15 mm Hg; and Tonopen XL and Kowa HAT, 0.02 ± 3.61 mm Hg. Computation of the width of the 95% limits of agreement resulted in a wide bias range when comparing Diaton with all tonometers. Relatively good agreements were observed between iCare, Tonopen XL, and HAT.

CONCLUSIONS

Intraocular pressure measurements obtained in a supine position by four portable tonometers were not interchangeable. Although iCare and Tonopen XL significantly overestimated IOP values in eyes with a higher IOP when compared with Kowa HAT, the agreements between iCare, Tonopen XL, and Kowa HAT were at clinically acceptable levels.

Clinical comparison of Pulsair non-contact tonometer and Goldmann applanation tonometer in Indian population

INTRODUCTION

Goldmann applanation tonometer (GAT) is the gold standard for Intraocular Pressure (IOP) measurement but has disadvantage of being contact device and problems with portability. The aim of the study was to compare the Keeler's Pulsair noncontact tonometer (NCT) with GAT in Indian Population.

MATERIALS AND METHODS

Eighty-one subjects were screened from a Glaucoma clinic of a tertiary care centre in North India. The IOP was measured by Pulsair NCT and GAT after explaining the procedure. Central corneal thickness (CCT) was measured to avoid its bias on IOP readings. The data were analyzed using SPSS software.

RESULTS

The mean age of subjects was 49.9±8.8 (mean±SD) years. The mean IOP as taken by Pulsair NCT was 15.79±4.07mmHg and that for GAT was 17.02±4.23mmHg (p=0.062). The mean CCT was 0.536±0.019mm. A positive Pearson's correlation coefficient of 0.909 (p=0.0001) was found between the two instruments. Bland and Altmann analysis showed a fair agreement between the two tonometers at lower IOP range.

CONCLUSION

Pulsair NCT can be used as a screening tool for community practices but is not reliable in the subjects with higher IOP range.

Applanation tonometry: a comparison of the Perkins handheld and Goldmann slit lamp-mounted methods

Purpose

To compare intraocular pressure (IOP) measurements, taken using Perkins applanation tonometry (PAT) and Goldmann applanation tonometry (GAT).

Methods

100 eyes of 100 patients underwent Perkins and Goldmann applanation tonometry, with a randomized order of modality, performed by a masked observer. The right eye was measured, for all subjects, and the data used in statistical analysis. The comparability of results given by the two instruments was evaluated using the Bland–Altman method.

Results

IOP measurements for 100 eyes were obtained (range: 10–44 mmHg). The mean GAT reading was 21.63 mmHg, with standard deviation (SD) 5.69 mmHg. The mean PAT reading was 21.40 mmHg, with SD 5.67 mmHg. The mean difference between readings from Goldmann versus Perkins tonometry was 0.22 mmHg (SD: 0.44 mmHg). The limits of agreement were calculated to be −0.64–+1.08 mmHg (1.96 SD either side of the bias).

Conclusion

The Perkins applanation tonometer yields IOP measurements that are closely comparable with GAT. Therefore, PAT may be used in routine clinical practice, as part of the implementation of national guidelines, or preferred practice patterns, for glaucoma and ocular hypertension.

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.

[Sources of error in Goldmann applanation tonometry]

Reliable measurements of the intraocular pressure (IOP) are necessary for glaucoma patients. The measuring procedure, anatomical changes of the eye or extraocular influences can lead to errors during applanation tonometry. The IOP is overestimated if measured through the wrong eyepiece of the slit lamp, if a force is interfering with the tonometer arm during the measurement, if the lid comes into contact with the tonometer tip, if blepharospasm occurs, if there is lid retraction or if a Valsalva maneuver is present. An underestimation of the IOP occurs if staining with fluorescein is absent or insufficient, if the illumination is not bright enough, if a corneal stromal edema is present, after LASIK, during accommodation, during repeated measures within a few minutes or during systemic blood pressure drop. Discrepancies of the IOP in both directions can appear if the calibration of the tonometer is irregular, if abnormal central corneal thickness or astigmatism is present. For correct measurements calibrations are advised once or twice a year.

Hand-held dynamic contour tonometry

PURPOSE

We present a prototype of the hand-held dynamic contour tonometer (HH-DCT) and prospectively compare this HH-DCT with the well-established Perkins applanation tonometer (PAT) and the TonoPenXL (TPXL).

METHODS

In a prospective, single-centre, randomized study, intraocular pressure (IOP) readings were taken in random order using HH-DCT, PAT and TPXL tonometers. Intra-observer variability was calculated for each observer and compared between three experienced ophthalmologists and an inexperienced medical student.

RESULTS

Ninety-two corneas of 92 healthy participants were enrolled. IOP [mean mmHg ± standard deviation (SD)] as measured by HH-DCT was 16.97 ± 2.71, by PAT 13.98 ± 2.52 and by TPXL 13.34 ± 2.68. The range of three consecutive IOP readings differed significantly between the devices [p < 0.001; mean range: 1.45 ± 1.07 (HH-DCT), 1.87 ± 0.97 (PAT) and 2.08 ± 1.77 (TPXL)]. There was no difference of the range in all devices between the ophthalmologists and the medical student (HH-DCT p = 0.68, PAT p = 0.54, TPXL p = 0.48).

CONCLUSION

IOP readings measured by HH-DCT are significantly higher than by PAT and TPXL. The differences of IOP measurements are in good accordance with previous studies using the slit-lamp-mounted DCT (SL-DCT) and Goldmann Applanation Tonometry, where SL-DCT readings were 1-3.2 mmHg higher. HH-DCT seems to give more constant results, which can be seen in the lower intra-observer variability compared to PAT and TPXL.

Continuous monitoring of intraocular pressure: rationale and progress toward a clinical device

Intraocular pressure (IOP) is a dynamic physiologic parameter with regular circadian variations and unpredictable short-term and long-term fluctuations. Current methods of measuring IOP are suboptimal with a typical clinical practice only performing periodic IOP measurements during regular office hours. Diurnal and 24-hour IOP measurements obtained on an in-patient basis can increase measurements but are inconvenient and expensive, and do not allow ambulatory monitoring of IOP. The goal of continuous IOP monitoring is to provide automated 24-hour recording of ambulatory IOP. Continuous IOP monitoring involves 2 complementary paradigms. Temporary noninvasive monitoring, possibly involving a contact lens-based pressure sensor, would be used to measure 24-hour IOP on a periodic basis. Permanent monitoring would be more invasive, using an implantable pressure sensor. Despite numerous previous attempts at continuous IOP monitoring, a device suitable for clinical use is not yet available. However, devices currently in development for permanent IOP monitoring seem to be nearly ready for human testing. The technologic issues for temporary monitoring may be greater than for permanent monitoring.

Prevalence of normal tension glaucoma in obstructive sleep apnea syndrome patients

PURPOSE

To explore the prevalence of normal tension glaucoma (NTG) among patients with obstructive sleep apnea syndrome (OSAS) and to examine OSAS as a risk factor of NTG.

PATIENTS AND METHODS

Fifty-one consecutive white patients with OSAS were compared with 40 healthy subjects. All the study subjects underwent blood gas analysis, polysomnography, oxyhemoglobin saturation, and an ophthalmologic examination including visual field, visually evoked potential (VEP), and pattern electroretinography (PERG) and disc analysis with the Heidelberg Retina Tomograph II.

RESULTS

Three of 51 OSAS patients (5.9%) had NTG. No patient in the control group had OSAS or NTG. The severity of OSAS correlated with intraocular pressure, the mean deviation of the visual field, the cup/disk ratio and the mean of the retinal nerve fiber layer thickness (P<0.01 to 0.001). Apnea hypopnea index and intraocular pressure were significantly greater in OSAS patients with abnormal VEP and PERG, compared to those with normal PERG and VEP.

CONCLUSIONS

The present study suggests that the prevalence of NTG in our OSAS patients is higher than expected in a white population of the same age and that OSAS may be an important risk factor for NTG. Our data underline the importance of taking an accurate sleep history from patients with NTG and referring patients with sleep disturbance for polysomnography.

Moderate to severe obstructive sleep apnoea patients is associated with a higher incidence of visual field defect

PURPOSE

To compare the visual fields (VFs) and optic nerve head changes between obstructive sleep apnoea (OSA) in normotensive patients and an age-matched non-OSA population.

DESIGN

Case-control study.

PARTICIPANTS

A total of 41 ethnic Chinese patients diagnosed with moderate to severe OSA referred from the Sleep Laboratory, ENT Department, Tuen Mun Hospital. A total of 35 age-matched non-OSA subjects recruited from the Ophthalmology Department, North District Hospital.

METHODS

Comprehensive ophthalmological and systemic history, complete ophthalmological examination, including central-30 computerized perimetry for all studied patients.

MAIN OUTCOME MEASURES

Polysomnographic data, VF indices, optic disc changes.

RESULTS

In the OSA arm, VF indices were significantly subnormal and the incidence of suspicious glaucomatous disc changes was four times higher than that of the control arm. None of the studied patients suffered from any form of anterior segment complications.

CONCLUSIONS

Moderate to severe OSA is associated with a higher incidence of VF defect and glaucomatous optic nerve changes.

Que savons-nous de la pression intra-oculaire dans la population togolaise ?

BACKGROUND

Intraocular pressure is a major ocular risk factor of chronic open angle glaucoma. This study aimed to describe characteristics of intraocular pressure in a defined black African population.

METHODS

Hospital outpatients were recruited for this study, and all measures were taken with a pulse air tonometer between 8 AM and 12 AM; some participants were glaucoma patients under medical treatment. On the whole, 7,042 participants (13,831 eyes) were included in this study.

RESULTS

The mean age of all participants was 41 +/- 18 years: 9.9% were under 16 years of age; 21.2% were between 35 and 44 years old. The average intraocular pressure was 17.05+/-5.93 mmHg; for the subgroup under 16 years of age. Girls had higher pressure than boys: 16.01 vs 16.32 mmHg in the right eye. For those over 16 years of age, pressures were higher in men, with an average of 17.45 mmHg vs 16.67 mmHg in the right eye. High intraocular pressure was found in 22.28% of the participants, with values ranging from 20 to 29 mmHg in 86.8% of cases. The relative prevalence of hypertony seems to increase with age, reaching 30% for those aged 55-64 years.

CONCLUSION

There is a high rate of hypertony in our findings, which seems to correlate with the increased glaucoma prevalence already described in the Togolese population. We concluded that in our setting, the prevention of glaucoma in isolated hypertonies and the management of glaucomatous cases warrant a thorough assessment of intraocular pressure at all ages.

Asymmetry of Right versus Left Intraocular Pressures over 24 Hours in Glaucoma Patients

PURPOSE

To assess the asymmetry of 24-hour intraocular pressures (IOPs) between right and left eyes of untreated open-angle glaucoma (OAG) patients, and its influence on the monocular therapeutic trial.

DESIGN

Experimental study with human patients.

PARTICIPANTS

Forty-one subjects (40-78 years old) with untreated OAG.

METHODS

Subjects were housed in a sleep laboratory for 24 hours. Intraocular pressures of both eyes were measured with a pneumatonometer every 2 hours with the patient in the sitting and supine positions from 7 am to 11 pm and in the supine position only from 11 pm to 7 am. Mean, peak, and trough IOPs were compared in right versus left eyes. The strength of association between right and left IOPs was assessed using coefficients of determination (R2). Validity of the monocular therapeutic trial was assessed by examining residual values from 2 linear regression models of right versus left IOP.

MAIN OUTCOME MEASURES

Strength of association between IOPs of right and left eyes, and residual values from linear models of IOP.

RESULTS

No statistically significant difference was found between mean, peak, or trough IOPs of right and left eyes over a 24-hour period. The strength of association for mean IOP was only moderate (R(2) = 0.421-0.623). Residual values of > or =3 mmHg were found in 14.0%+/-12.0% (mean +/- standard deviation) of IOP measurements for a symmetric linear regression model, and 8.5%+/-10.6% of IOP measurements for a best-fit linear regression model over 24 hours.

CONCLUSIONS

In this group of untreated glaucoma patients, the strength of association between the right and left eye mean IOPs is only moderate. Residual values of > or =3 mmHg were more common using a symmetric model than with a best-fit model. The current method of performing monocular therapeutic trials in glaucoma patients is unreliable, but it may be possible to improve reliability by using several IOP measurements obtained at different times of the day instead of a single office measurement.

Communicating the ocular and systemic complications of obesity to patients

BACKGROUND

Obesity has become a growing worldwide epidemic that is associated with serious medical complications. Many clinicians and patients are aware of the systemic complications of obesity, but there are few providers and patients who are aware of the ocular manifestations of obesity.

METHODS

A review of the current medical literature was performed. Ocular and systemic manifestations associated with obesity are described, and a methodology for educating the optometric patient is presented.

RESULTS

There is significant morbidity and mortality associated with obesity, which is causing serious consequences to patients and an enormous economic strain on the health care system. Optometrists have a tremendous opportunity and obligation to educate their patients on the potential sight-threatening complications of obesity and encourage them to decrease their caloric intake and increase their physical activity to help alleviate this individual and collective burden.

CONCLUSIONS

Optometrists have a duty to educate and counsel their overweight and obese patients on the devastating ocular complications that could manifest as a result of obesity.

Effect of breath-holding on pulsatile ocular blood flow measurement in normal subjects

BACKGROUND

The Valsalva maneuver is known to affect intraocular pressure (IOP). Simple breath-holding may cause IOP elevation. A recent study demonstrated a decrease in pulsatile ocular blood flow (POBF) during forcible exhalation. This study investigated whether breath-holding could affect POBF measurement.

METHODS

Thirty-eight healthy young adults were recruited. Their POBF's were measured with an ocular blood flow pneumatonometer. The first set of measurements was made using normal measurement protocol. Three consecutive readings were obtained, and the mean was used for analysis. The second set of measurements was taken after 5-min rest, and the subjects were required to hold their breath during the acquisition period.

RESULTS

As previously reported, POBF reduced with increasing myopia. There was no significant change in IOP, pulse rate, POBF, and pulse amplitude between normal protocol and breath-holding condition. POBF and pulse amplitude demonstrated a greater variation, shown by coefficient of variation, when subjects held their breath.

CONCLUSIONS

This study found a greater variation in consecutive POBF measurements during breath-holding condition. There was no significant difference in either POBF or pulse amplitude during breath-holding session, probably because of the use of three consecutive measurements, and averaged results were generated from them. It is advised to measure the POBF by taking consecutive readings, and subjects should not hold their breath.

Intraocular pressure during haemodialysis: a review

OBJECTIVES

Although several works in the past have examined the effect of haemodialysis (HD) on intraocular pressure (IOP), reported findings, theories, and conclusions are very different. The objectives of this article are to resume the reported evidence of IOP changes during HD, to review the proposed hypothesis of HD influence on IOP, and to determine if ophthalmic examination is imperative in HD patients.

METHODS

We analysed the peer-reviewed English literature and selected all possible relevant articles.

RESULTS

The influence of HD on IOP is not clear, and even in recent studies opposite findings can be found.

CONCLUSIONS

Future studies are needed to clarify the effects of HD on IOP. In patients with glaucoma or with predisposed narrow angles, or eyes with impaired aqueous outflow, the possibility of acute IOP rise during HD could be much more frequent than in normal patients. So in these patients, a more strict ophthalmic scheduled examination seems to be feasible.

Complementary and alternative medicine for glaucoma

Given the recent interest in complementary and alternative medicine (CAM), some patients may seek such treatments to supplement their traditional glaucoma management. The prevalence of CAM use for glaucoma is approximately 5%. We reviewed the literature to determine the potential benefit of various alternative treatments. Aside from a temporary osmotic effect from high dose intravenous ascorbic acid, there is no evidence that megavitamin supplementation has a beneficial effect on glaucoma. During exercise, autoregulation in healthy eyes seems to maintain a consistent blood flow rate to the optic nerve despite fluctuations in intraocular pressure (IOP). In a glaucomatous eye, the very modest IOP-lowering that follows exercise may be offset by the initial elevation in IOP that occurs when one first initiates exercise. At this time, there is no evidence to encourage or discourage the use of special diets, acupuncture, relaxation techniques, or therapeutic touch specifically for the treatment of glaucoma. Very little research has been done on the majority of herbal remedies with regard to their treatment of glaucoma. Marijuana can cause a profound lowering of IOP, but the high nonresponse rate, short half life, and significant toxicity are strong indicators that it is not an appropriate therapeutic agent. Ginkgo biloba and some other Chinese herbal remedies do not affect IOP, but may improve blood flow to the optic nerve and, as such, may have a beneficial effect on glaucoma. These agents have recognized toxicities. Although there are some well-designed studies of alternative treatments, many of the recommendations for using alternative treatments are currently unsupported by the data provided.

[Glaucoma and ocular hypertension in primary care]

OBJECTIVES

To find the distribution of intra-ocular pressure (IOP) in our population over 40 and the prevalence of glaucoma (G) and ocular hypertension (OH).

DESIGN

Descriptive.

SETTING

Primary care.

SUBJECTS

990 people >= 40 years old.Measurements. Age, sex, body mass index (BMI), ophthalmic history, risk factors, visual sharpness (optotype), ophthalmoscopy and IOP (applanation tonometry). Patients with back-of-eye disorders and/or IOP >= 21 mmHg were referred to the ophthalmologist for assessment (campimeter).

RESULTS

870 people, average age 54.66 and 45.4% of them men. Mean IOP was 12.96 in the right eye and 13.27 in the left, with significant differences between them, but not between sexes or age-groups. 70 patients were referred (11 for IOP >= 21, 54 for disturbance perceived by ophthalmoscope and 5 for both reasons). The ophthalmologist classified 9 as G, 12 as OH and 15 as suspected G. We calculated 1.81% (95% CI, 0.98-2.63) prevalence of G in the >= 40s, including 9 cases already known. OH prevalence was 1.61% (95% CI, 0.82-2.39). Through logistical regression, we found greater risk of G in people with myopia (OR adjusted for age and sex = 3.01) and Hypertriglyceridaemia (ORa, 6.34). OH risk was significantly greater in patients with BMI >= 30 (ORa, >= 4.20).

CONCLUSIONS

Glaucoma prevalence confirms published findings from other similar populations, while IOP and OH prevalence were much less here. Given that half G cases are undiagnosed, we believe its early detection in primary care should be highlighted, at least in at-risk groups.

Sleep disorders: a risk factor for normal-tension glaucoma?

PURPOSE

To determine the prevalence of sleep-related symptoms and sleep-related breathing disorders by polysomnography in patients with normal-tension glaucoma (NTG).

PATIENTS AND METHODS

This comparative case series included 23 patients with NTG, 14 NTG suspects, and 30 comparison patients without NTG. A sleep history was obtained and determined to be positive or negative. Polysomnography was offered for patients with a positive sleep history. Prevalence of a positive sleep history and prevalence of sleep disorders were the main outcome measures.

RESULTS

The NTG, NTG suspect, and comparison groups did not differ with respect to age, body mass index, systemic disease, gender, or race. Thirteen (57%) of 23 patients with NTG, 6 (43%) of 14 NTG suspects, and 1 (3%) of 30 comparison patients had a positive sleep history (P = 0.001). Nine of 13 patients with NTG and four of six NTG suspects with a positive sleep history chose to undergo polysomnography. Seven (78%) of nine patients with NTG and all four NTG suspects undergoing polysomnography were diagnosed with a sleep disorder. Five patients with NTG had sleep apnea and two had sleep hypopnea. Two NTG suspects had sleep apnea; one had sleep hypopnea; and one had upper airway resistance syndrome. The one comparison patient with a positive sleep history had upper airway resistance syndrome by polysomnography.

CONCLUSIONS

Sleep-disturbed breathing may be a risk factor for NTG. Although we do not provide evidence for a cause-and-effect relationship, various physiologic factors produced by sleep-disturbed breathing may play a significant role in the pathogenesis of this optic neuropathy. We recommend obtaining a sleep history from patients with NTG and performing polysomnography in those patients with sleep disturbance symptoms.