Hypertension, perfusion pressure, and primary open-angle glaucoma. A population-based assessment

Retinal vessel diameter and open-angle glaucoma: the Blue Mountains Eye Study

PURPOSE

To examine the relationship between open-angle glaucoma (OAG) and retinal vessel diameter among baseline participants in the Blue Mountains Eye Study.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

The study included 3654 persons older than 49 years, representing 82.4% of permanent residents living in an area west of Sydney.

METHODS

Participants had a detailed eye examination, including automated perimetry and stereo optic disc photography. A computer-assisted program measured retinal vessel diameters from digitized photographs of right eyes.

MAIN OUTCOME MEASURES

Open-angle glaucoma was diagnosed from matching visual field defects and optic disc cupping, without reference to intraocular pressure (IOP) level. Ocular hypertension was defined as IOP of >21 mmHg in either eye, without matching glaucomatous optic disc and field changes. Average retinal vessel diameters, measured from right eyes, were summarized as arteriolar and venular equivalents. The lowest quintile of the arteriolar equivalent or arteriole-to-venule ratio was used to define generalized retinal arteriolar narrowing.

RESULTS

The study included 3314 participants, after excluding those with incomplete data or nonglaucomatous optic nerve disease. Of persons included, 59 (1.8%) had evidence of glaucomatous damage affecting the right eye, 3065 (92.5%) had no damage to either eye, and 163 (4.9%) had ocular hypertension. Right eyes with glaucomatous damage had significantly narrower retinal arteriolar diameters (183+/-2.6 microm) than eyes without glaucoma (194+/-0.4 microm, P = 0.0001) or eyes with ocular hypertension (195+/-1.6 microm, P = 0.0002), after adjusting for age, mean arterial blood pressure, and other confounding variables, including refraction. Right eyes with glaucomatous damage were at least 2 times more likely to have generalized retinal arteriolar narrowing than eyes without glaucoma (odds ratio, 2.7; 95% confidence interval, 1.5-4.8).

CONCLUSIONS

These population-based data suggest that generalized retinal arteriolar narrowing, an indicator of localized vascular change, is significantly associated with optic nerve damage caused by OAG. It is not clear whether such a retinal arteriolar change reflects an ischemic process leading to optic nerve damage or results from loss of retinal neurons secondary to glaucoma.

Fluorescein leakage of the optic disc in glaucomatous optic neuropathy

PURPOSE

To identify and quantify the role of capillary leakage of the optic nerve head in digital fluorescein angiography in normal subjects and patients with open-angle glaucoma.

METHODS

We conducted a prospective cross-sectional study in the Department of Ophthalmology of the Technical University of Aachen. Thirty patients with primary open-angle glaucoma (POAG) and 30 healthy age-matched subjects were included. Fluorescein angiograms were performed using the scanning laser ophthalmoscope. The fluorescence of the optic nerve head and the surrounding retina (ratio of leakage) was measured using digital imaging analysis in the late phases of the angiogram (9-10 min).

RESULTS

The ratio of optic nerve head fluorescence to retinal reference loci was significantly increased (p=0.01) in patients with glaucoma (POAG, 1.38+/-0.34) compared with normal subjects (1.20+/-0.19). Intraocular pressure (p=0.0001), visual field indices (mean deviation, p<0.0001; pattern standard deviation, p<0.0001; corrected pattern standard deviation, p<0.0001), and cup to disc ratios (p=0.02) differed significantly between the groups. Age and systolic and diastolic blood pressure showed no significant differences between groups.

CONCLUSION

Fluorescein angiography revealed significantly increased vascular leakage of glaucomatous optic nerve heads. An endothelial disruption and fluorescein leakage might be the result of mechanical stress at the level of the lamina cribrosa and/or a sign of ischemic damage. This measurement approach might enable us to judge the severity of optic nerve head leakage, and it is a potential way to evaluate therapeutic regimens.

Retinal Peripapillary Blood Flow before and after Topical Brinzolamide

PURPOSE

To study the effect of topical brinzolamide on retinal capillary blood flow by the Heidelberg Retina Flowmeter (HRF) in patients with glaucoma.

METHODS

Twenty patients with glaucoma were consecutively recruited. One eye for each patient was randomly selected. Patients were classified as glaucomatous if they had an abnormal visual field and/or an abnormal optic nerve head with an intraocular pressure (IOP) greater than 21 mm Hg without any treatment. After an eye examination, baseline retinal blood flow measurements were made with confocal scanning laser Doppler flowmetry. Blood flow and IOP measurements were then repeated after 1 month of treatment. Blood flow measurements were analyzed by using an automatic full-field perfusion image analysis (AFFPIA) program. The blood flow was calculated in the superior and inferior part of the optic disk. In each area, the blood flow was calculated as temporal area, the nasal area and the rim area as for software AFFPIA.

RESULTS

The mean age of the patients was 56 +/- 7 (mean +/- standard deviation) years. The mean IOP before treatment was 23.7 +/- 1.5 mm Hg while the mean IOP after 4 weeks of treatment was 19.1 +/- 2.2 mm Hg. This difference was statistically significant (p < 0.01). Significant (p < 0.05) increases in retinal blood flow were found for the temporal and nasal areas between baseline and 1 month after the treatment. No difference was found between superior and inferior sectors.

CONCLUSION

Topical brinzolamide reduced the IOP significantly and apparently improved retinal blood flow as measured by the HRF.

Cerebral hemodynamics in ocular hypertension

PURPOSE

To evaluate the cerebral blood flow velocity in patients with ocular hypertension.

MATERIAL AND METHODS

Twenty-four ocular hypertensive patients and 24 age- and sex-matched healthy volunteers were recruited in a prospective comparative study. All subjects had normal findings on full-threshold visual field tests and clinically normal optic nerves. All patients with ocular hypertension had an intraocular pressure (IOP) of >21 mmHg on three separate occasions without treatment. Systolic and diastolic blood pressure by cuff, heart rate by palpation, IOP by Goldmann applanation tonometry, central corneal thickness by ultrasound pachymetry, blood flow velocities, and pulsatility index of the ipsilateral middle cerebral artery by transcranial color Doppler were measured.

RESULTS

Systolic and diastolic blood pressures (P=0.40 and P=0.45, respectively), heart rate (P=0.30), and central corneal thickness (P=0.23) were similar in each group. Peak and end-diastolic blood flow velocities in the middle cerebral artery did not differ between ocular hypertensives and controls (P=0.37 and P=0.87, respectively). In addition, pulsatility index did not significantly differ between ocular hypertensives and controls (P=0.61).

CONCLUSIONS

The results of this study suggest that ocular hypertension is not associated with reduction in blood flow velocity and elevation of resistance in the middle cerebral artery.

Associations between the deletion polymorphism of the angiotensin 1-converting enzyme gene and ocular signs of primary open-angle glaucoma

BACKGROUND

Primary open-angle glaucoma (POAG) is a leading cause of blindness. High intraocular pressure (IOP) has been shown to be a key risk factor for POAG. Topical application of angiotensin 1-converting enzyme (ACE) inhibitors has been shown to lower IOP, and angiotensin-induced increase in vascular tone has been implicated as a pathogenetic mechanism in glaucomatous cupping and damage to the optic nerve. The objective of this study was to investigate the association between the deletion polymorphism in the ACE gene and ocular signs of POAG.

METHODS

Baseline data from the Rotterdam Study was used. The ACE genotype was determined in 6,462 subjects. We used univariate and multiple variable statistical techniques to examine associations between ACE genotype and each of ocular hypertension, glaucomatous optic neuropathy, glaucomatous visual field defects and POAG diagnosis.

RESULTS

We found no consistent evidence between ACE genotype and ocular signs of POAG. We did, however, find evidence of an association between ACE genotype and optic disc area, subjects homozygous for the deletion allele tending to have fractionally smaller optic disc areas than those with a single deletion allele subjects, who in turn tended to have fractionally smaller optic discs than those with no deletion alleles (P=0.01).

CONCLUSIONS

The data provided little evidence of any association between ocular signs of POAG and the deletion polymorphism of ACE. There was, however, evidence that ACE may be associated with optic disc size-this was an unexpected finding.

Hypothyroidism and the development of open-angle glaucoma in a male population

PURPOSE

To determine if hypothyroidism is associated with an increased risk of glaucoma using a large cohort of patients.

DESIGN

Nested case-control study.

PARTICIPANTS

Patients seen at the Veterans Affairs Medical Center in Birmingham, Alabama with newly diagnosed glaucoma between 1997 and 2001 were selected (n = 590) and age-matched to nonglaucoma controls (n = 5897).

METHODS

Patient information was extracted from the Birmingham Veterans Affairs Medical Center data files containing demographic, clinical, and medication information. An index date was assigned to the glaucoma subjects corresponding to the time of diagnosis. Patients who had a glaucoma diagnosis before the observation period of the study were excluded. Ten controls were randomly selected for each patient and matched on age (+/-1 year) and an encounter on or before the index date of the matched case.

MAIN OUTCOME MEASURES

Odds ratios (ORs) for the association between the prior diagnosis of hypothyroidism and the risk of developing glaucoma with adjustment for the presence of diabetes, lipid metabolism disorders, hypertension, cardiovascular disease, cerebrovascular disease, arterial disease, and migraines.

RESULTS

After adjustment for the other potential risk factors, patients were significantly more likely to have prior hypothyroidism than controls (OR, 1.40; 95% confidence interval, 1.01-1.97).

CONCLUSIONS

Our study has demonstrated a significantly greater risk of subjects with a preexisting diagnosis of hypothyroidism developing glaucoma, compared with controls, in a large Veterans Affairs Medical Center population.

Short-term effect of latanoprost on ocular circulation in ocular hypertension

PURPOSE

To determine the short-term effects of latanoprost on retrobulbar circulation in ocular hypertension.

METHODS

Forty-six eyes of 23 consecutive bilateral ocular hypertensive patients with an intraocular pressure (IOP) of greater than 22 mmHg were evaluated in a prospective controlled study. All subjects received a single drop of latanoprost 0.005% in one eye and placebo in the fellow control eye. Systemic circulatory parameters, intraocular pressure, blood flow velocities, and resistance indices of the ophthalmic, short posterior ciliary and central retinal arteries were measured using colour Doppler imaging at baseline and 2 h and 8 h after dosing.

RESULTS

Latanoprost lowered IOP significantly after 2 h and 8 h (P < 0.01). The mean IOP reduction was 6.7 mmHg 8 h after dosing. At baseline, there were no statistically significant differences in any retrobulbar vessels of eyes that received a single drop of latanoprost when compared with the eyes that received placebo (P > 0.05). Comparisons with baseline and latanoprost conditions revealed that latanoprost did not alter the blood flow velocities and resistance indices in the ophthalmic (P > 0.05), posterior ciliary (P > 0.05) and central retinal (P > 0.05) arteries 2 h and 8 h after dosing. The systolic and diastolic blood pressures (p = 0.74, p = 0.29, respectively) and pulse rate (p = 0.68) remained unchanged over the 8-h period.

CONCLUSIONS

This study found that a single drop of latanoprost significantly reduces intraocular pressure 8 h after dosing. However, it does not have any short-term effects on the retrobulbar haemodynamics in ocular hypertensive eyes.

Retinal venous pulsation in glaucoma and glaucoma suspects

PURPOSE

To determine whether changes in central retinal vein pulsation characteristics occur in glaucoma, and how these are related to indices of glaucoma severity.

DESIGN

A large, consecutive, prospective, case-controlled study.

PARTICIPANTS

Ninety-four consecutive glaucoma patients and 105 glaucoma suspects seen in a tertiary referral clinic were examined. Forty-one age-matched normal subjects also were examined.

METHODS

The presence or absence of spontaneous venous pulsation was observed in these 3 groups. The ophthalmodynamometric force (ODF) required to induce venous pulsation at the optic disc was measured in those without spontaneous pulsation. Optic disc photographs were obtained and visual field testing was performed for all subjects.

MAIN OUTCOME MEASURES

The prevalence of spontaneous venous pulsation between these 3 groups was compared. The relationship between ODF and visual field mean deviation, neuroretinal rim area, age, intraocular pressure (IOP), gender, and diagnosis of glaucoma was investigated using linear mixed models fitted by Gibb's sampling.

RESULTS

Significantly fewer (chi-square, 27.7; P<0.001) glaucoma patients (54%) were observed to have spontaneous venous pulsation than suspects (75%) or normals (98%). A worse visual field mean deviation was shown to be the most significant predictor of a higher ODF (P<0.000), with younger age (P<0.000) also predictive of a higher ODF. A strong relationship between ODF and mean deviation was found in the glaucoma patients (r = 0.59; n = 52; P<0.001).

CONCLUSIONS

Spontaneous venous pulsation is less common in glaucoma. The ODF required to induce venous pulsation is increased in glaucoma, and this ODF is greater in those with more severe field loss.

Open-Angle Glaucoma and Systemic Hypertension

PURPOSE

To assess whether systemic hypertension is associated with open-angle glaucoma (OAG) in an older population.

PATIENTS AND METHODS

The Blue Mountains Eye Study examined 3654 subjects aged 49 to 97 years. Hypertension was diagnosed from history in treated subjects or from systolic blood pressure (BP) > or=160 mm Hg or diastolic BP > or=95 mm Hg. OAG was diagnosed from congruous glaucomatous optic disc rim thinning and visual field loss, without reference to intraocular pressure (IOP) level. Ocular hypertension (OH) was defined when IOP was > 21 mm Hg in either eye, among persons without OAG.

RESULTS

Hypertension was present in 45.7% of subjects, OAG in 3.0%, and OH in 5.2%. Hypertension was significantly associated with OAG, after adjustment for OAG risk factors including IOP, odds ratio (OR) 1.56, 95% confidence interval (CI) 1.01-2.40. This relation was strongest in subjects with poorly controlled treated hypertension (OAG prevalence 5.4%), compared with normotensive subjects (OAG prevalence 1.9%), independent of IOP (OR 1.88, CI 1.09-3.25). The population attributable risk for hypertension (20.4%) was higher than for other identified OAG risk factors. The prevalence of OH was 8.1% in subjects with poorly controlled treated hypertension (OR 1.81, CI 1.20-2.73) and 8.2% in untreated hypertension (OR 1.96, CI 1.31-2.95), compared with 4.2% in normotensive subjects.

CONCLUSIONS

Hypertension, particularly if poorly controlled, appears related to a modest, increased risk of OAG, independent of the effect of BP on IOP and other glaucoma risk factors. However, we could not exclude nocturnal hypotensive episodes among treated subjects. Hypertension was also associated with OH, a relationship that could in part reflect the influence of BP on IOP.

Dynamic cerebral autoregulation is impaired in glaucoma

OBJECTIVES

Autonomic and endothelial dysfunction is likely to contribute to the pathophysiology of normal pressure glaucoma (NPG) and primary open angle glaucoma (POAG). Although there is evidence of vasomotor dysregulation with decreased peripheral and ocular blood flow, cerebral autoregulation (CA) has not yet been evaluated. The aim of our study was to assess dynamic CA in patients with NPG and POAG.

MATERIALS AND METHODS

In 10 NPG patients, 11 POAG patients and 11 controls, we assessed the response of cerebral blood flow velocity (CBFV) to oscillations in mean arterial pressure (MAP) induced by deep breathing at 0.1 Hz. CA was assessed from the autoregressive cross-spectral gain between 0.1 Hz oscillations in MAP and CBFV.

RESULTS

0.1 Hz spectral powers of MAP did not differ between NPG, POAG and controls; 0.1 Hz CBFV power was higher in patients with NPG (5.68+/-1.2 cm(2) s(-2)) and POAG (6.79+/-2.1 cm(2) s(-2)) than in controls (2.40+/-0.4 cm(2) s(-2)). Furthermore, the MAP-CBFV gain was higher in NPG (2.44+/-0.5 arbitrary units [a.u.]) and POAG (1.99+/-0.2 a.u.) than in controls (1.21+/-0.1 a.u.).

CONCLUSION

Enhanced transmission of oscillations in MAP onto CBFV in NPG and POAG indicates impaired cerebral autoregulation and might contribute to an increased risk of cerebrovascular disorders in these diseases.

Nitric oxide proxies and ocular perfusion pressure in primary open angle glaucoma

BACKGROUND

To investigate the levels of nitric oxide (NO) markers in plasma and aqueous humour of patients with primary open angle glaucoma (POAG) and their relation to ocular perfusion pressure.

METHODS

Cyclic guanosine monophosphate (cGMP) and nitrite (NO(2)(-)) were determined in plasma and aqueous humour of 38 patients with POAG and 46 controls. Blood pressure and IOP were measured to calculate ocular perfusion pressure (PP).

RESULTS

cGMP and NO(2)(-) plasma levels were significantly decreased in glaucoma patients compared with controls (p = 0.001 v p = 0.004). In the aqueous humour of subjects with POAG, cGMP and NO(2)(-) concentrations were also lower than in normal eyes (p = 0.0001 v p = 0.001). There was a linear association between cGMP in plasma and aqueous humour in glaucomas and controls (r = 0.514, p = 0.029 and r = 0.558, p = 0.004) and this relation differed in the two groups (p = 0.003). Considering glaucoma patients with controls, a positive correlation was found between cGMP and PP (r = 0.379, p = 0.01) and between NO(2)(-) and PP (r = 0.339, p = 0.040). The cGMP/PP correlation was of borderline statistical significance in controls (p = 0.050), whereas it did not attain statistical significance in POAG, as well as the association between NO(2)(-) and PP when glaucomas and controls were considered separately.

CONCLUSIONS

The authors found alterations of NO markers in the plasma and aqueous humour of glaucoma patients. Primary or secondary impaired NO balance could alter ocular perfusion pressure.

Ocular blood flow alteration in glaucoma is related to systemic vascular dysregulation

AIMS

To investigate the source of ocular blood flow alterations in glaucoma.

METHODS

In 56 patients with open angle glaucoma, blood flow parameters were obtained from both eyes in the ophthalmic and central retinal artery by means of colour Doppler imaging, as well as in the choroidal circulation and the neuroretinal rim of the optic nerve by means of laser Doppler flowmetry. Based on these haemodynamic parameters, a cluster analysis (two groups) was performed and differences with regard to risk factors were assessed between clusters.

RESULTS

Ocular blood flow data in the two clusters indicated that the two groups (cluster 1 = 26 patient with higher blood flow values; cluster 2 = 30 patients with lower blood flow values) differed mainly in choroidal and optic nerve blood flow. No differences in sex distribution, propensity to have normal tension glaucoma, age, endothelin-1 plasma levels, visual field damage, intraocular pressure, or systemic blood pressure parameters were observed between the two clusters. However, 12 patients (46%) from the cluster with high ocular blood flow values showed a vasospastic response in nailfold capillaroscopy, while such a response was observed in 24 patients (80%) of the cluster with low ocular blood flow values. This difference in vasospastic propensity was statistically significant (p = 0.0121).

CONCLUSIONS

Ocular blood flow alterations in glaucoma patients seem, at least partly, to be related to a systemic vascular dysregulation.

Critical Flicker Fusion Frequency: Relation to Resting Systolic Blood Pressure

OBJECTIVE

Past studies have shown that a number of factors, both acute and chronic, influence individual differences in critical flicker fusion frequency (CFF). In this study, we assessed whether CFF co-varied with resting systolic blood pressure (SBP).

METHODS

SBP and CFF were assessed in one session in 221 subjects (mean age, 19.6 +/- 2.5 years), and SBP and CFF were assessed over 10 sessions in 12 subjects. CFF values were determined psychophysically using a 570 nm circular 1 degrees test field centrally fixated. Blood pressure was determined with an automated sphygmomanometer.

RESULTS

There was a significant (p < 0.0002) positive relation between CFF and SBP for the larger sample (n = 221). Significant within-subject relations were found for 6 of the 12 subjects tested repeatedly.

CONCLUSIONS

The combination of results strongly suggests that CFF and resting SBP are positively related.

Effect of bimatoprost on ocular circulation in patients with open-angle glaucoma or ocular hypertension

PURPOSE

To study the effect of bimatoprost 0.03% (Lumigan) on ocular hemodynamics in patients with open-angle glaucoma or ocular hypertension.

METHODS

One randomly selected eye of each of 26 patients with open-angle glaucoma or ocular hypertension was enrolled. Each patient received a drop of bimatoprost 0.03% once daily for 1 month. The effect of bimatoprost on ocular circulation was assessed by color Doppler imaging (CDI), which measured peak systolic, end-diastolic blood flow velocities and resistance indices in the ophthalmic, posterior ciliary and central retinal arteries. Retrobulbar hemodynamics by CDI, intraocular pressure by Goldmann applanation tonometer, blood pressure by cuff, and heart rate by palpation were measured at baseline and at 1 month after bimatoprost treatment.

RESULTS

Blood flow velocities and resistance indices in all retrobulbar vessels showed no statistically significant differences between baseline and bimatoprost condition (P>0.05). Bimatoprost lowered intraocular pressure significantly (P<0.001), with a mean change of 6.5 mmHg (27%) after 1 month of treatment. The systolic (P=0.38) and diastolic (P=0.74) blood pressures and pulse rate (P=0.94) did not show statistically significant differences during the study period.

CONCLUSIONS

The results of this study suggest that topical bimatoprost 0.03% significantly reduces intraocular pressure in patients with open-angle glaucoma or ocular hypertension. However, it does not have any effect on retrobulbar hemodynamics in open-angle glaucoma and ocular hypertension.

Glaucoma and mortality

PURPOSE

To compare mortality rates in glaucoma patients and matched controls from a large population screening as well as glaucoma patients diagnosed through routine clinical examination (self-selected patients).

METHODS

A population-based screening of 32,918 elderly citizens of Malmö was conducted between 1992 and 1997. Individuals with newly detected, previously untreated open-angle glaucoma were identified. Two controls of the same age and gender were chosen among the screening negative participants for each patient. From the same birth cohorts, glaucoma patients seen in routine clinical practice (self-selected patients) were identified through retrospective examination of patient records from the Eye Department at Malmö University Hospital. The number and time of deaths for each group were determined based on centrally administered registers.

RESULTS

Mean follow-up time was 7.75 years. Five-year mortality did not differ significantly between the groups, and was 9.2% among glaucoma patients from the screening (n=402), and 11.9% among the controls (n=804; p=0.7406). Self-selected glaucoma patients had a 5-year mortality of 8.5% (n=354), not significantly different from the screening-detected glaucoma patients (p=0.1361). Among glaucoma patients, neither IOP (p=0.1781) nor pseudoexfoliation (p=0.8882) was related to significantly increased mortality.

CONCLUSIONS

The results of this study strongly suggest that the life expectancy of glaucoma patients does not differ from the population at large.

Color Doppler imaging in ocular hypertension and open-angle glaucoma

PURPOSE

To quantify the retrobulbar hemodynamics of patients with ocular hypertension and open-angle glaucoma and to compare it with that of normal subjects.

METHODS

Nineteen eyes of 19 ocular hypertensive patients, 19 eyes of 19 open-angle glaucoma patients and 19 eyes of 19 normal subjects were recruited from our clinic and underwent color Doppler imaging evaluation of the ophthalmic, posterior ciliary, and central retinal arteries. The peak systolic and end-diastolic blood flow velocities and resistivity indices of all retrobulbar vessels were measured.

RESULTS

The retrobulbar blood flow velocities were lower and resistivity indices were higher in all retrobulbar vessels in ocular hypertensive patients than in normal subjects. The differences, however, did not reach statistical significance ( P>0.05). Glaucoma patients had lower end-diastolic velocities and higher resistivity indices than did normal subjects in the ophthalmic ( P=0.003 and P=0.003, respectively), posterior ciliary ( P=0.001 and P<0.001, respectively), and central retinal arteries ( P=0.03 and P=0.04, respectively). Glaucoma patients had significantly lower end-diastolic velocity and higher resistivity index than did patients with ocular hypertension in the posterior ciliary artery ( P=0.04 and P=0.001, respectively).

CONCLUSIONS

This study suggests that ocular hypertensive patients have more normal blood flow than do glaucoma patients, because all retrobulbar homodynamic measurements in ocular hypertension range between glaucoma and normal subjects. On the other hand, glaucoma is associated with blood-flow velocity reduction and resistivity index elevation in all retrobulbar arteries.

Is there a direct association between age-related eye diseases and mortality? The Rotterdam Study

PURPOSE

To study mortality in subjects with age-related maculopathy (ARM), cataract, or open-angle glaucoma (OAG) in comparison with those without these disorders.

DESIGN

Population-based prospective cohort study.

PARTICIPANTS

Subjects (n = 6339) aged 55 years and older from the population-based Rotterdam Study for whom complete information on eye disease status was present.

MAIN OUTCOME MEASURES

Vital status continuously monitored from 1990 until January 1, 2000.

METHODS

The diagnosis of ARM was made according to the International Classification System. Cataract, determined on biomicroscopy, was defined as any sign of nuclear or (sub)cortical cataract, or both, in at least one eye with a visual acuity of 20/40 or less. Aphakia and pseudophakia in at least one eye were classified as operated cataract. Definite OAG was defined as a glaucomatous optic neuropathy combined with a glaucomatous visual field defect. Diagnoses were assessed at baseline. Mortality hazard ratios were computed using Cox proportional hazard regression analysis, adjusted for appropriate confounders (age, gender, smoking status, body mass index, cholesterol level, atherosclerosis, hypertension, history of cardiovascular disease, and diabetes mellitus).

RESULTS

The adjusted mortality hazard ratio for subjects with AMD (n = 104) was 0.94 (95% confidence interval [CI], 0.52-1.68), with biomicroscopic cataract (n = 951) was 0.94 (95% CI, 0.74-1.21), with surgical cataract (n = 298) was 1.20 (95% CI, 0.86-1.68), and with definite OAG (n = 44) was 0.39 (95% CI, 0.10-1.55).

CONCLUSIONS

Both ARM and cataract are predictors of shorter survival because they have risk factors that also affect mortality. When adjusted for these factors, ARM, cataract, and OAG were themselves not significantly associated with mortality.

Comparison of ambulatory blood pressure values in patients with glaucoma and ocular hypertension

PURPOSE

To compare systemic arterial blood pressure (BP) and nocturnal hypotension in patients with normal-tension glaucoma (NTG), high-tension glaucoma (HTG), and ocular hypertension.

METHODS

Systemic BP was recorded by a portable automated BP monitoring device every 20 min during the day and every 30 min at night in patients with NTG (n=18), HTG (n=22), and ocular hypertension (n=19). Mean systolic, diastolic, and mean arterial BPs were calculated for 24 h, during the day and at night. The mean and maximum nocturnal dip rates were determined for each patient. The number of readings that declined below 90 mmHg for systolic BP and below 60 and 50 mm Hg for diastolic BP was recorded for each group. Statistical significance was set at P<0.05.

RESULTS

Minimum, maximum, and mean values of the systolic, diastolic, and mean arterial BPs were not significantly different among groups. There was no difference among groups in the nocturnal dip percentages of systolic and diastolic BPs. The number of systolic BP readings below 90 mmHg was significantly higher in the NTG group compared with the other groups (P<0.001, chi(2) test).

CONCLUSION

There may not be any difference among NTG, HTG, and ocular hypertension patients in terms of mean ambulatory BP values. On the other hand, when each individual's ambulatory reading is reviewed, readings may reveal that excessive and repetitive nocturnal drops occur more frequently in some patients with NTG. These hypotensive episodes may be related to the development of glaucomatous damage.

Intraocular pressure and visual field loss in primary angle closure and primary open angle glaucomas

AIM

To compare the correlation between visual field loss and the pretreatment intraocular pressure (IOP) in primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG).

METHODS

In a cross sectional observational study of 74 patients (43 PACG, 31 POAG), pretreatment IOP was measured at presentation, before treatment was initiated. The severity of visual field loss was assessed by AGIS score, mean deviation (MD), pattern standard deviation (PSD), and corrected pattern standard deviation (CPSD). Glaucomatous optic neuropathy was assessed from simultaneous stereo disc photographs.

RESULTS

There was a stronger correlation between pretreatment IOP and the extent of visual field loss in PACG subjects than in those with POAG for both MD (PACG: Pearson correlation coefficient (r) = 0.43, p = 0.002; r(2) = 0.19), (POAG: r = 0.21, p = 0.13; r(2) = 0.04) and AGIS score (PACG: r = 0.41, p = 0.003; r(2) = 0.17), (POAG: r = 0.23, p = 0.19; r(2) = 0.05 respectively). No such associations were seen for pattern standard deviation (PSD) or corrected pattern standard deviation (CPSD) in either group (p> 0.29). Both horizontal and vertical cup-disc ratio were well correlated with severity of field loss but not with presenting IOP for either diagnosis.

CONCLUSIONS

This is consistent with the hypothesis of a greater IOP dependence for optic nerve damage in PACG than POAG and, conversely, a greater importance of other, less pressure dependent mechanisms in POAG compared to PACG.

Primary open-angle glaucoma in blacks: a review

Glaucoma is one of the leading causes of blindness worldwide. Primary open-angle glaucoma (POAG) is the most prevalent form of glaucoma and has a particularly devastating impact in blacks. In the black American population, POAG prevalence is estimated to be six times as high in certain age groups compared to whites. POAG is more likely to result in irreversible blindness, appears approximately 10 years earlier and progresses more rapidly in blacks than in whites. Racial differences in optic disk parameters have been reported and show that blacks have larger optic disks than whites. This finding is robust and may account for the reported differences in other optic disk parameters. The existence of racial differences in intraocular pressure remains to be demonstrated, as conflicting findings are reported in the literature. Intraocular pressure may actually be underestimated in blacks, perhaps because they have thinner corneas. The prevalence of diabetes and hypertension is higher in blacks than in whites, and although no causal relationship has been established between POAG and each of these systemic diseases, some reports suggest that they often occur together, perhaps through an indirect relationship with intraocular pressure. Compounding the problem, there is evidence that blacks are less responsive to both drug and surgical treatment for POAG. Finally, they often have reduced accessibility to treatment and are less aware of the risks of having POAG. This article provides a comprehensive review of the current knowledge pertaining to POAG in blacks.

Autonomic system activity and 24-hour blood pressure variations in subjects with normal- and high-tension glaucoma

PURPOSE

As suggested by findings of abnormal responses to posture in patients with normal-tension glaucoma (NTG), cardiovascular autoregulation may also be defective in primary open-angle glaucoma (POAG).

PATIENTS AND METHODS

Both 24-hour ambulatory blood pressure monitoring and the head-up tilt test were performed in 17 subjects with NTG and in 13 subjects with high-tension POAG (ht-POAG). These groups were compared with 17 age-matched healthy individuals. Subjects undergoing cardiovascular therapy were excluded.

RESULTS

No significant differences in diurnal and nocturnal blood pressure and heart rate were found between the groups. A significant reduction in diurnal heart rate variability was found in NTG (12.1 +/- 2.8 bpm) compared with the ht-POAG (15.0 +/- 2.4 bpm, P < 0.01) and control groups (15.8 +/- 3.0 bpm, P = 0.01]). Nocturnal diastolic blood pressure variability was also reduced in NTG (6.9 +/- 2.2 mm Hg) compared with controls (8.6 +/- 2.3 mm Hg, P < 0.05]) as was heart rate variability (6.3 +/- 1.4 vs 8.3 +/- 2.6 in ht-POAG, P < 0.05), suggesting blunted blood pressure and heart rate modulation in NTG subjects. Spectral analysis of short-term heart rate variability showed a significant reduction of total power in the supine position (1064 +/- 600 in NTG vs 1688 +/- 889 ms2 in controls, P < 0.05]). This was not accompanied either by a physiological reduction in total power or in a high-frequency component during the passive orthostatic stimulus. These differences tend to become more prominent in the clinically more severe forms of NTG (as identified by scores based on the extent of optic disk excavation, visual field damage, and progression of disease). This would suggest a correlation between the extent of autonomic disorder and severity of glaucoma. The alpha index (root-square of low-frequency heart rate to low-frequency blood pressure ratio) was lower in the supine position in NTG subjects (8.1 +/- 3.1 vs 10.6 +/- 3.3 ms/mm Hg in controls, P < 0.05), confirming the reduced baroreflex sensitivity.

CONCLUSIONS

The results confirm the hypothesis that dysfunction of autonomic control of the cardiovascular response may be a contributing pathogenetic factor in NTG, inducing a chronic ischemia of the optic nerve.

Some current ideas on the pathogenesis and the role of neuroprotection in glaucomatous optic neuropathy

The primary features of glaucomatous optic neuropathy are characteristic changes in the optic nerve head, a decrease in number of surviving ganglion cells and a reduction in vision. It is now generally accepted that a number of factors, including elevated intraocular pressure, could lead to the changes seen in the optic nerve head and to obtain a pharmacological means to treat the causes will vary from patient to patient. In contrast, a cascade of events have been proposed to explain how the changes in the optic nerve head may lead to the slow and differential death of ganglion cells in the disease. It is also proposed that drugs (neuroprotectants) influencing this cascade of events can attenuate ganglion cell death and lead to the treatment of all glaucoma patients.

Reduced cerebrovascular blood flow velocities and vasoreactivity in open-angle glaucoma

PURPOSE

To compare cerebral blood flow velocities between open-angle glaucoma (OAG) patients and controls, at baseline and during hyperoxia.

DESIGN

Observational cohort study.

METHODS

A prospective study was conducted in a single institution. Sixteen OAG patients and 15 normal subjects, matched for age, were enrolled. Patients and controls were studied at baseline, while breathing room air, and during 100% oxygen breathing. The eye with the more severe visual field defect was chosen in glaucoma patients, while in controls, the study eye was chosen randomly. Subjects with history of diabetes, cardiovascular, or respiratory disease were excluded. Measurements included brachial arterial pressure, heart rate, intraocular pressure and transcranial Doppler (TCD). Mean and peak velocity and pulsatility index of the ipsilateral middle cerebral artery (MCA) were measured by TCD.

RESULTS

At baseline, MCA mean and peak systolic blood flow velocities were significantly lower in glaucoma patients compared with controls velocities were significantly lower in glaucoma patients compared with controls (mean velocity: 50.2 vs 65.3 cm/s, P <.05; peak velocity: 74.2 vs 96.8 cm/s, P <.05). Additionally, while hyperoxia significantly decreased both mean and peak systolic velocities in MCA of controls (mean velocity: 65.3 vs 57.7 cm/s, P <.05; peak velocity 96.8 vs 87.9 cm/s, P <.05), it did not cause any significant change in OAG patients.

CONCLUSIONS

Glaucoma patients were found to have lower MCA blood flow velocities and an absence of vasoreactivity to hyperoxia, compared with controls. The relationship of these cerebral hemodynamic abnormalities to glaucoma pathogenesis and progression remains to be explored.

The Finnish evidence-based guideline for open-angle glaucoma

In most patients, chronic open-angle glaucoma is a slowly progressive disease. Eyes with very high intraocular pressure (IOP > 30 mmHg) represent an exception to this and should be treated and followed extremely intensively. As lowering IOP is, so far, the only means of treating glaucoma, the majority of research reports deal with the IOP-lowering effect of the treatment. The primary goal of treatment, however, is to prevent glaucomatous damage to the structures and function of the eye. The effectiveness of treatment is monitored with optic disc and retinal nerve fibre layer imaging and with visual field examinations. If the glaucomatous changes are progressing, more effective treatment should be given. In the course of follow-up, it should be noted that the changes in the optic nerve structure and function appear and progress at different time-points with delays of up to several years. The assessment of abnormalities is dependent on the examination method and requires a great deal of experience on the part of the examiner. The important risk factors in glaucoma are elevated IOP (even if IOP is within normal range in half of patients ), age, positive family history, exfoliation, race and myopia.

Ocular pulse amplitude in patients with open angle glaucoma, normal tension glaucoma, and ocular hypertension

BACKGROUND/AIM

Intraocular pressure (IOP) is not a fixed constant value but rather has pulsatile components associated with cardiac action. The SmartLens dynamic observing tonometer (odc, Ophthalmic Development Company AG, Zurich, Switzerland) can measure and record simultaneously IOP and ocular pulse amplitude (OPA). It was the aim of this study to evaluate OPA in patients with primary open angle glaucoma (POAG) and high IOP, normal tension glaucoma (NTG), and ocular hypertension (OHT). Furthermore, the authors examined whether there were any correlations with blood pressure.

METHODS

80 subjects were divided into four groups (n=20): 20 patients each with POAG, NTG, and OHT and 20 volunteers without any ocular pathology except for cataract served as a control group.

RESULTS

The OPA of the POAG group was not statistically significant different from the control group and from the OHT group. However, OPA was statistically significant lower (p<0.01) in the NTG group compared with all other groups. The OPA of the OHT group was slightly higher compared to the healthy volunteers (p=0.09) and to the POAG patients (p=0.09). No statistically significant correlations with blood pressure could be detected. A logistic regression model was established which identified OPA as an independent risk factor for NTG.

CONCLUSIONS

The study demonstrated a decrease in OPA of patients suffering from NTG. Thus, measuring of OPA by the SmartLens dynamic observing tonometer could be helpful in the detection of NTG patients.

Interrelations among smoking habits, casual blood pressure and intraocular pressure in middle and old-aged Japanese residents

OBJECTIVES

To investigate the association of smoking habits with blood pressure (BP) and intraocular pressure (IOP), and to examine whether the smoking-BP association is related to the IOP level.

METHODS

This study was conducted on the basis of a cross-sectional design using annual health check-up data during one-year between August, 1999 and August, 2000 for 611 middle and old-aged Japanese residents living in Ibaraki prefecture, Japan.

RESULTS

After adjustment for age, gender, body mass index and alcohol intake score, the proportion of hypertensives, and the mean systolic and diastolic blood pressure (SBP and DBP) of the subjects without antihypertensive medications were the highest (50.4%, 129.6 mmHg and 75.9 mmHg, respectively) in the "smokers of 25 or more cigarettes per day with intraocular pressure (IOP)≥15 mmHg" of six subgroups crossed by three smoking categories (non-smokers, 1 to 24 cigarettes per day, and 25 or more cigarettes per day) and two IOP categories (less than 15 mmHg, and 15mmHg or greater). On the other hand, the adjusted proportion of hypertensives, and the adjusted mean SBP and DBP decreased with increasing smoking category in the individuals with less than 15 mmHg of the IOP (p for trend=0.028 for proportion of hypertensives 0.008 for the SBP, and 0.001 for the DBP, respectively).

CONCLUSIONS

Heavy smoking may be specifically related to 'high BP accompanied by high IOP', although the BP may be inversely associated with smoking under the condition without high IOP.

The impact of ocular blood flow in glaucoma

Two principal theories for the pathogenesis of glaucomatous optic neuropathy (GON) have been described--a mechanical and a vascular theory. Both have been defended by various research groups over the past 150 years. According to the mechanical theory, increased intraocular pressure (IOP) causes stretching of the laminar beams and damage to retinal ganglion cell axons. The vascular theory of glaucoma considers GON as a consequence of insufficient blood supply due to either increased IOP or other risk factors reducing ocular blood flow (OBF). A number of conditions such as congenital glaucoma, angle-closure glaucoma or secondary glaucomas clearly show that increased IOP is sufficient to lead to GON. However, a number of observations such as the existence of normal-tension glaucoma cannot be satisfactorily explained by a pressure theory alone. Indeed, the vast majority of published studies dealing with blood flow report a reduced ocular perfusion in glaucoma patients compared with normal subjects. The fact that the reduction of OBF often precedes the damage and blood flow can also be reduced in other parts of the body of glaucoma patients, indicate that the hemodynamic alterations may at least partially be primary. The major cause of this reduction is not atherosclerosis, but rather a vascular dysregulation, leading to both low perfusion pressure and insufficient autoregulation. This in turn may lead to unstable ocular perfusion and thereby to ischemia and reperfusion damage. This review discusses the potential role of OBF in glaucoma and how a disturbance of OBF could increase the optic nerve's sensitivity to IOP.

Individual factors influencing trabecular morphology in glaucoma patients undergoing filtration surgery

PURPOSE

Epidemiologic studies have shown that various lifestyle characteristics are statistically associated with the chronic open-angle glaucomas. This study was designed to investigate the influence of individual factors on the light-microscopic morphology of the trabecular meshwork in open-angle glaucomas.

METHODS

Quantitative computer-assisted topographic analysis of the trabecular meshwork was performed in meridional sections of 80 trabeculectomy specimens from patients with primary open-angle (n = 36), exfoliative (n = 30) and pigment-dispersion (n = 14) glaucoma. Measurements included inner wall length of the, central thickness of the trabecular meshwork, and compactness of the Schlemm canal and trabecular meshwork. Morphologic data were correlated with individual patient data including age, duration of the disease, maximum intraocular pressure, cup-disc ratio, refraction, height, weight, body mass index, a simple morbidity index, previous surgery, and number of topical antiglaucomatous medications used.

RESULTS

Inner wall length of the Schlemm canal was significantly lower in eyes with previous filtering surgery (P = 0.03), but not in eyes with a high number of topical medications (P = 0.17). There was a significant tendency for the inner wall length of the Schlemm canal to be shortened in patients where high maximum intraocular pressure was combined with long-term glaucoma (P = 0.027). Body mass index did not differ significantly between patients with primary open-angle, exfoliative, and pigment-dispersion glaucoma and showed no correlation with the quantitative data of the meshwork. The morbidity index correlated well with body mass index (0.0006) and age (P < 0.0001).

CONCLUSION

Contrary to findings of experimental mice studies, we found no indication that glaucoma patients with lower body mass index have a larger lumen of the Schlemm canal than patients with a higher body mass index. Although caution should be used when interpreting data from trabeculectomy studies, there is a certain probability that a history of previous filtering surgery and of a long-term high intraocular pressure will be associated with a shortening of the Schlemm canal.

Biochemical markers of the L-arginine-nitric oxide pathway in the aqueous humour in glaucoma patients

PURPOSE

To study the role of the L-arginine-nitric oxide (NO) pathway in aqueous humour dynamics by measuring nitrate, nitrite and cyclic (cGMP) levels in guanosine 3',5'-monophosphate the aqueous humour of glaucomatous and nonglaucomatous cataract patients.

METHODS

The study involved 38 glaucoma patients undergoing unilateral cataract surgery in the glaucomatous eye and 38 cataract control patients matched for sex, age, smoking habits and organic nitrate medication. All subjects underwent ophthalmic examination, and blood pressure was measured preoperatively. Nitrite, nitrate and cGMP levels were measured in aqueous humour and serum.

RESULTS

The NOx (nitrite + nitrate), nitrite and cGMP concentrations in the aqueous humour were slightly higher in the glaucoma patients than in the control patients, but the differences did not reach statistical significance. The levels of cGMP in serum were higher in the glaucoma patients (P = 0.053). The subgroup of glaucoma patients with pseudoexfoliation had lower NOx and nitrite values in the aqueous humour (P = 0.046 and P = 0.345, respectively) than the matched controls, while cGMP levels were higher (P = 0.043). Levels of NOx and nitrite in the aqueous humour were higher in patients using oral nitroglycerin (P = 0.062 and P = 0.042, respectively) than in patients without this medication. Blood pressure was higher in the glaucoma patients, with a mean of 165/89 mmHg as compared to 153/81 mmHg in the controls (P-values 0.071/0.008).

CONCLUSIONS

No differences in NO metabolites were found between glaucoma and control patients. However, any real changes may have been disguised by optimal medication of glaucoma. Low NOx and high cGMP levels in the aqueous humour of pseudoexfoliation patients warrant further evaluation in a larger study.

Factors affecting awareness and knowledge of glaucoma among patients presenting to an urban emergency department

BACKGROUND

Until advanced, glaucoma is asymptomatic. For early diagnosis to occur, patients may need to be aware of it and seek assessment regularly. People who have risk factors for glaucoma may have a greater awareness of the disease.

METHODS

Patients presenting to an urban hospital emergency department were surveyed with a brief questionnaire to assess their knowledge of glaucoma. Data was collected about their gender, age, family history of glaucoma and presence of systemic hypertension, diabetes, Raynaud's phenomenon, migraines and myopia.

RESULTS

Women (Odds ratio 2.3; 95% CI 1.4-3.7; P < 0.01), people who were 40 years or older (Odds ratio 2.2; 95% CI 1.1-4.4; P < 0.05) and those who were aware of a family history of glaucoma (Odds ratio 15.7; CI 5.5-45.3; P < 0.01) knew significantly more about the disease than others. People with other risk factors did not demonstrate significantly greater knowledge despite 89% of all participants having had a previous eye examination.

CONCLUSION

This information may be useful to predict which patients may know about glaucoma when they present for an eye examination and who should be targeted in public health campaigns.

Retrobulbar blood flow in glaucoma patients with nocturnal over-dipping in systemic blood pressure

PURPOSE

To evaluate the relationship between the circadian blood pressure rhythm and the retrobulbar blood flow in glaucoma patients.

DESIGN

Cross-sectional study.

METHODS

Circadian blood pressure measurements and color Doppler imaging (CDI) in the ophthalmic artery as well as the central retinal artery of one randomly selected eye were obtained in 193 primary open-angle glaucoma patients. CDI parameters were compared by means of analysis of covariance between patients with a nocturnal decrease in mean systemic blood pressure (MBP) below 20% of the average daytime MBP (over-dippers), patients with a decrease between 10% to 20% (dippers), and patients with a decrease of less than 10% (nondippers), using age, intraocular pressure (IOP), and MBP during color Doppler measurement as covariates.

RESULTS

An analysis of covariance disclosed, after correcting for age, IOP, and MBP during color Doppler imaging, a significantly lower EDV (P =.0096) and a significantly higher RI (P =.033) in the central artery of over-dipping glaucoma patients compared with nondippers or dippers. This effect seemed independent of the use of vasoactive drugs .

CONCLUSIONS

Glaucoma patients with a marked drop in nocturnal systemic blood pressure seem to have altered retrobulbar blood flow parameters, suggesting that an abnormal systemic blood pressure profile may be the manifestation of some kind of systemic vascular dysregulation relevant for the ocular circulation.

Neuroprotective effect of alpha(2) agonist (brimonidine) on adult rat retinal ganglion cells after increased intraocular pressure

Brimonidine, a selective alpha(2)-adrenoceptor agonist, has recently been shown to be neuroprotective as it significantly improves survival of retinal ganglion cells (RGCs) after calibrated optic nerve injury in rats. In the present study, we examined the effect of brimonidine (alpha(2)-adrenoceptor agonist) on RGC survival after increased intraocular pressure (IOP) in adult rats. RGCs were prelabeled by bilateral tectal injection of 5% Fluoro-Gold (FG). Two days later, unilaterally IOP was increased 2.2-2.5 times (28-30.5 mmHg) that of the normal pressure (12.5-14.5 mmHg) by cauterization of three episcleral veins. The elevated IOP was maintained throughout the duration of the experiment. Rats were treated intraperitoneally with brimonidine (1 mg/kg) or phosphate-buffered saline (PBS) once per week beginning either before (group A) or after (group B) increasing the IOP. Another group of rats was left as the control with elevated IOP but without any brimonidine/PBS treatment. Rats were euthanized at 3, 4 and 5 weeks after IOP elevation. Identifiable RGCs were counted and compared between control and experimental groups. Brimonidine significantly protected RGCs from elevated IOP-induced cell death. In control rats with three-vein cauterization, there was 5-6% cell death per week. Almost all RGCs were protected following brimonidine treatment for 3 weeks both in groups A and B. At 4 weeks, there was 4.5% cell death in group A and 6.5% in group B. At 5 weeks, cell death was 5.9% in group A and 6.2% in group B. The difference in cell death in groups A and B was insignificant. No significant differences were observed between PBS-treated and control groups. No significant changes in elevated IOP was found after brimonidine or PBS treatment when compared with the nontreated control group. Although pressure remained elevated throughout the length of the experiment, 3 weeks later the amount of cell death gradually increased in brimonidine-treated animals.

Blood flow in the optic nerve head and factors that may influence it

In the recent past there has been great interest in the blood supply of the optic nerve head (ONH), how to evaluate ONH blood flow, and what factors influence it, in health and disease. This is because evidence has progressively accumulated that there is vascular insufficiency in the ONH in both anterior ischemic optic neuropathy (AION) and glaucomatous optic neuropathy (GON)-two major causes of blindness or of seriously impaired vision in man. For the management and prevention of visual loss in these two disorders, a proper understanding of the factors that influence the blood flow in the ONH is essential. The objective of this paper is, therefore, to review and discuss all these factors. The various factors that influence the vascular resistance, mean blood pressure and intraocular pressure are discussed, to create a better basic understanding of the ONH blood flow, which may help us toward a logical strategy for prevention and management of ischemic disorders of the ONH.

Intraocular pressure in genetically distinct mice: an update and strain survey

BACKGROUND

Little is known about genetic factors affecting intraocular pressure (IOP) in mice and other mammals. The purpose of this study was to determine the IOPs of genetically distinct mouse strains, assess the effects of factors such as age, sex and time of day on IOP in specific strain backgrounds, and to assess the effects of specific candidate gene mutations on IOP.

RESULTS

Based on over 30 studied mouse strains, average IOP ranges from approximately 10 to 20 mmHg. Gender does not typically affect IOP and aging results in an IOP decrease in some strains. Most tested strains exhibit a diurnal rhythm with IOP being the highest during the dark period of the day. Homozygosity for a null allele of the carbonic anhydrase II gene (Car2n) does not alter IOP while homozygosity for a mutation in the leptin receptor gene (Leprdb) that causes obesity and diabetes results in increased IOP. Albino C57BL/6J mice homozygous for a tyrosinase mutation (Tyrc-2J) have higher IOPs than their pigmented counterparts.

CONCLUSIONS

Genetically distinct mouse strains housed in the same environment have a broad range of IOPs. These IOP differences are likely due to interstrain genetic differences that create a powerful resource for studying the regulation of IOP. Age, time of day, obesity and diabetes have effects on mouse IOP similar to those in humans and other species. Mutations in two of the assessed candidate genes (Lepr and Tyr) result in increased IOP. These studies demonstrate that mice are a practical and powerful experimental system to study the genetics of IOP regulation and disease processes that raise IOP to harmful levels.

Effects of metaraminol bitartrate on intraocular pressure in dogs under halothane anesthesia

The effects of metaraminol bitartrate on intraocular pressure (IOP) were studied in dogs anesthetized with halothane. Forty-five healthy, adult, mixed-breed dogs, of both sexes, were divided into three groups of 15 dogs each (GI, GII and GIII) and maintained under general anesthesia with halothane after tranquilization with levomepromazine and induction with thiopental. Saline (0.9%) was administered intravenously (IV) to GI through continuous infusion, at a velocity of 0.125 mL kg-1 min-1. GII and GIII received metaraminol 0.004% IV, at a dose of 5 &mgr;g kg-1 min-1, at 0.125 mL kg-1 min-1 and at a dose of 2 &mgr;g kg-1 min-1, at 0.06 mL kg-1 min-1, respectively. IOP was measured by applanation tonometry (Tono-Pen) before and during anesthesia. Results showed that IOP decreased in GI, increased in GII, and remained at basal levels in GIII. Continuous infusion of metaraminol at 2 &mgr;g kg min-1 maintained IOP at pretest levels, while infusion at 5 &mgr;g kg-1 min-1 produced an elevation of IOP.

Patterns of open-angle glaucoma in the Barbados Family Study

OBJECTIVE

To describe the Barbados Family Study of open-angle glaucoma (OAG) and present risk factors for OAG in siblings of study probands.

DESIGN

Observational study of families of probands with OAG.

PARTICIPANTS

Two hundred thirty probands and 1056 relatives (from 207 families).

METHODS

Probands and their family members underwent standardized examinations, including automated perimetry, applanation tonometry, ophthalmologic evaluation, fundus photography, blood pressure, interview, and genotyping. Generalized estimation equation methods were used to evaluate risk factors.

MAIN OUTCOME MEASURES

Presence of OAG in the relatives, as defined by both visual field and optic disc findings, after ophthalmologic exclusion of other causes.

RESULTS

The median ages of probands and relatives were 68 and 47 years, respectively. In the 207 families, 29% of the probands had one relative with OAG and 10% had two or more relatives affected. Of the 1056 family members, 10% had OAG, 13% had suspect OAG, and 6% had ocular hypertension. One fifth of the 338 siblings had OAG (n = 67); they tended to be older and more often were male. Multivariate comparisons between siblings with and without OAG found that age, higher intraocular pressure (IOP), myopia, and lower diastolic blood pressure-IOP differences were related to OAG, whereas hypertension and diabetes were not.

CONCLUSIONS

Based on standardized protocols and examinations, approximately one quarter of the relatives had OAG or suspected OAG, despite their relatively young age. Risk factors for OAG in siblings were similar to risk factors in unrelated individuals. Analyses are ongoing to determine OAG inheritance and to localize potential gene(s) involved.

Three Common Assumptions About Ocular Blood Flow and Glaucoma

Although substantial indirect evidence exists to link altered ocular blood flow to glaucoma, it must be remembered that the validity of investigations in this area depends on acceptance of three basic assumptions: 1) ischemia directly causes or increases the susceptibility of the optic nerve to glaucomatous damage; 2) optic nerve vascular anatomy and physiology allows identification of the critical vascular beds in optic nerve disease; and 3) current measurement techniques provide the ability to monitor important vascular beds. The hypotheses underlying these assumptions are examined.

Update on topical carbonic anhydrase inhibitors

Topical carbonic anhydrase inhibitors are a novel addition to the armamentarium of medical glaucoma treatment; dorzolamide has been available since 1995 and brinzolamide since 1998. They lower intraocular pressure by inhibiting carbonic anhydrase, a key enzyme for aqueous humor formation. Intraocular pressure-lowering activity of the substances appears to be the same and is similar to that of most other agents, but it does not reach the activity of the unselective beta-blocker timolol or the prostaglandin latanoprost. On concomitant treatment, additivity is reached with all other topical agents. A possible improvement of blood flow may offer an additional benefit, but its significance for the long-term outcome for human glaucoma remains to be shown. Side effects are mostly local. A more physiologic pH of brinzolamide appears to be advantageous.

Fludrocortisone in the treatment of systemic hypotension in primary open-angle glaucoma patients

BACKGROUND

Fludrocortisone is a potent mineralocorticoid, which has no known direct vasoactive properties, and is the first-line drug for treatment of orthostatic hypotension. The present study evaluated the systemic hemodynamic effects of fludrocortisone treatment in glaucoma patients.

PATIENTS AND METHODS

A retrospective analysis of the charts of glaucoma patients of the University Eye-Clinic Basel was performed. Twenty-two patients with open-angle glaucoma under treatment with fludrocortisone were selected. The selected patients had one 24-h blood pressure recording immediately prior to treatment with fludrocortisone and one recording at least 2 months after starting the treatment. Parallel to blood pressure recordings, diurnal intraocular tension curve recordings and visual field testings were carried out. In addition, twelve patients also had nail-fold video-capillaroscopy.

RESULTS

IOP and visual fields remained stable. The average values for all systemic blood-pressure readings showed an improvement in the follow-up compared to primary examination. Mean (+/- SD) night-to-day ratio ('nocturnal dips') of systolic, diastolic and mean arterial blood pressure decreased from 13.6 +/- 4.3%, 16.9 +/- 5.2% and 15.9 +/- 3.5%, respectively, to 9.9 +/- 5.9% (p = 0.01), 13.2 +/- 4.3% (p = 0.044) and 11.7 +/- 3.9% (p = 0.0004). Baseline capillary blood-flow velocity increased and capillary blood-flow standstill time after cold provocation decreased significantly under fludrocortisone therapy.

CONCLUSION

Hemodynamic parameters show a tendency towards improvement in a magnitude which might be of clinical relevance.

The acute effect of pilocarpine on pulsatile ocular blood flow in ocular hypertension

PURPOSE

To determine the acute effects of application of 2% pilocarpine on pulsatile ocular blood flow.

METHODS

In a randomised prospective controlled study of an exploratory nature, 18 subjects with ocular hypertension had pilocarpine 2% eye drops instilled into a randomly chosen eye three times at 10 min intervals. Physiological saline was instilled into the contralateral control eye. Intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) measurements were taken before the first application and 90 min after the last application using the OBF tonometer (OBF Laboratory, Wilts, UK). Statistical analysis was performed using the Wilcoxon signed rank test.

RESULTS

Of the 18 patients who entered the trial, 2 were suggested by the OBF system software as having 'poorly reliable' data. The analysis was made on the remaining 16. There was a significant reduction in IOP at 90 min for the treated eye in comparison with the contralateral control eye (p = 0.001; median difference -4.25 mmHg; 95% confidence interval, -5.85 to -2.40). There was a significant increase in POBF at 90 min in the treated eye in comparison with the contralateral control eye (p < 0.001; median difference 4.60 microl/s; 95% confidence interval, 2.35 to 6.75).

CONCLUSION

Acute application of pilocarpine 2% drops increased POBF to a significant extent in untreated ocular hypertension.

Retrobulbar hemodynamics in normal-tension glaucoma with asymmetric visual field change and asymmetric ocular perfusion pressure

PURPOSE

To investigate retrobulbar hemodynamics by means of color Doppler imaging in normal-tension glaucoma with asymmetric visual field change and asymmetric ocular perfusion pressure.

METHODS

Forty-nine consecutive patients who met the enrollment criteria were enrolled in a prospective study. We measured intraocular pressure at 2-hour intervals for 24 hours and performed color Doppler imaging of the orbital arteries, 48-hour ambulatory blood pressure monitoring, and visual field testing. Color Doppler parameters were compared between subjects with higher ocular perfusion pressure in the eye that had a better mean deviation (concordant group) and worse mean deviation (discordant group).

RESULTS

In the eyes with the better mean deviation, the end-diastolic velocity of the ophthalmic artery was significantly slower in the discordant group (P=.0145), while in the eyes with the worse mean deviation, the peak systolic and end-diastolic velocities of the ophthalmic artery were significantly slower and the resistance index of the ophthalmic artery was significantly higher in the discordant group (P=.0395, P=.0088, and P=.0324, respectively). In the concordant group, the end-diastolic velocity of the central retinal artery was slower in eyes with a worse mean deviation.

CONCLUSION

Retrobulbar hemodynamics are significantly altered in patients with normal-tension glaucoma who have better ocular perfusion pressure in the eye that has a worse mean deviation.

Relationship between intraocular pressure and obesity in Japan

BACKGROUND

Some cross-sectional studies have suggested that age, systolic blood pressure and obesity are positively related to intraocular pressure (IOP), but few longitudinal studies have examined this relationship. This study was carried out to evaluate the association between intraocular pressure and obesity by cross-sectional and longitudinal analyses in a large Japanese population.

METHODS

Data were collected from annual health examinations between 1989 and 1997 and reviewed retrospectively. Subjects of the cross-sectional analysis were 70 139 males and females aged 14-94 years. Among these subjects, 25 216 males and females who had undergone IOP measurements more than three times were analysed longitudinally. The association between IOP and obesity was examined cross-sectionally and longitudinally.

RESULTS

Cross-sectional analysis: The mean IOP at the last visit was 11.6 mmHg. The IOP decreased gradually with age and was significantly higher in males than in females in almost all age groups. Body mass index (BMI) significantly correlated with IOP after controlling for age, gender and blood pressure. Longitudinal analysis: There was a significant association between longitudinal change in IOP and change in weight. This relationship remained significant after controlling for initial BMI, initial blood pressure, change in blood pressure, gender and age.

CONCLUSION

This study showed a significant association between IOP and obesity in both cross-sectional and longitudinal analysis. These findings suggest that obesity is an independent risk factor for increase in IOP.

Why study vascular factors in glaucoma?

There is clinical and experimental evidence that both increased intraocular pressure and disturbed circulation are involved in the pathogenesis of glaucomatous damage. Among the many factors discussed, decreased blood pressure and vasospasm are the most important, and these factors may, at least in part, be therapeutically influenced. The basic underlying disorder might be a vascular dysfunction leading to local vasospasm and to systemic hypotension.

Glaucoma

In 2000 an estimated 66.8 million people worldwide will have glaucoma, 6.7 million of whom will be bilaterally blind from irreversible optic-nerve damage. Yet even in developed countries with public educational programmes that target glaucoma, half of the individuals with glaucoma remain undiagnosed. Patients with even mild visual impairment secondary to glaucoma may have difficulties with mobility, driving, and social interactions. Although glaucoma may be associated with increased eye pressures, its diagnosis does not rely on a specific level of eye pressure. Diagnosis of glaucoma often relies on examination of the optic disc and assessment of the visual field. The two most common types of glaucoma--primary open-angle glaucoma and primary angle-closure glaucoma--have different risk factors. Although similar medications can be used to treat these two types of glaucoma, the overall management of patients differs in important ways. Until recently, there were no randomised clinical trials that showed the effectiveness of lowering eye pressures with medications or surgery in patients with glaucoma. However, in 1998 a randomised clinical trial showed the benefit of lowering eye pressure in patients with glaucoma who had eye pressures of 24 mm Hg or less. Because glaucoma is treatable, and because the visual impairment from glaucoma is irreversible, early detection of the disease is critically important.

High intraocular pressure and survival: the Framingham Studies

PURPOSE

To examine whether high intraocular pressure (greater than or equal to 25 mm Hg) or a history of treatment for glaucoma is associated with decreased survival and, if so, how such ocular markers might be explained.

METHODS

Eye examinations, including applanation tonometry, were conducted on members of the Framingham Eye Study cohort from February 1, 1973, to February 1, 1975. Participants who reported a history of treatment for glaucoma were identified. Survival data, including information on the date of death, were available from the time of the Eye Study through March 31, 1990.

RESULTS

Of the 1,764 persons under the age of 70 years at the baseline eye examination, 1,421 persons had low intraocular pressure (< or =20 mm Hg), 264 persons had medium intraocular pressure levels (20 to 24 mm Hg), and 79 persons had high intraocular pressure (> or =25 mm Hg) or history of glaucoma treatment. During the follow-up period, 29%, 30%, and 47% died in the groups with low, medium, and high intraocular pressure (or history of glaucoma treatment), respectively. In an age-and-sex adjusted Cox proportional hazards analysis, the death rate ratio for the group with medium intraocular pressure relative to the group with low intraocular pressure was 1.04. The corresponding death rate ratio for the group with high intraocular pressure was 1.56 with a 95% confidence interval of 1.11 to 2.19 (P < .001). After adjustment for age, sex, hypertension, diabetes, cigarette smoking, and body mass index, a positive relationship remained, but at a borderline level of significance (P = .075).

CONCLUSIONS

High intraocular pressure or the presence of glaucoma is a marker for decreased life expectancy in the Framingham Eye Study cohort. The relationship is present even after adjustment for risk factors known to be associated with higher mortality such as age, sex, hypertension, diabetes, cigarette smoking, and body mass index. Special attention to the general health status of patients with high intraocular pressure or glaucoma seems warranted.

Optic nerve blood flow in glaucoma

Vascular disorders of the anterior optic nerve, historically, have been described as potential etiologic factors in the development of glaucomatous optic neuropathy. During the past several decades, clinical and experimental evidence of the involvement of vascular aberrations as a potential causative factor or associated risk factor have increased. However, the direct evidence that optic nerve ischemia contributes to glaucomatous optic neuropathy remains limited. Several questions about our current knowledge arise. Can ischemia alone or in combination with other factors cause glaucomatous optic neuropathy? Does our current knowledge of the vascular anatomy and physiology of the optic nerve allow us to understand vascular changes observed in individuals with glaucoma? Can we rely on current measurement techniques to assess and monitor the vascular beds of the optic nerve? This article summarizes the complex nature of the microcirculation in the anterior optic nerve, discusses the possible contribution of vascular factors in the development of glaucoma optic neuropathy, and examines the measurement techniques used in current studies.

Red blood cell membrane integrity in primary open angle glaucoma: ex vivo and in vitro studies

PURPOSE

There is increasing evidence that abnormal perfusion of the optic nerve head is an important factor involved in the pathophysiology of glaucoma. Transport and distribution of oxygen to the tissues takes place through the erythrocyte membrane. Red blood cell (RBC) acetylcholinesterase (AChE) is a marker of RBC membrane integrity. The aim of this study was to find out whether RBC membrane integrity is preserved in primary open angle glaucoma (POAG), and whether it is modified by the use of topical timolol maleate and pilocarpine.

METHOD

RBC AChE activity was determined ex vivo by Kaplan's spectrophotometric method in 19 POAG patients undergoing topical treatment for glaucoma with timolol, pilocarpine or a combination of the two drugs, and compared with that in 20 controls. To assess the effect of antiglaucomatous therapy in our findings, we carried out an in vitro study in 26 non-glaucomatous patients in which we measured RBC AChE activity after incubation of blood with either timolol maleate, pilocarpine or a combination of the two drugs, using the same spectrophotometric method.

RESULTS

There was a significant increase in RBC AChE enzyme activity in POAG patients compared with the control group (p < 0.002). However, timolol and pilocarpine, individually or in combination, have the opposite effect, significantly decreasing RBC AChE activity (p < 0.05).

CONCLUSION

This change in RBC AChE enzyme activity could suggest alterations in RBC membrane integrity in primary open angle glaucoma. Whether or not this finding has implications regarding the microcirculation at the optic nerve head needs to be investigated further.