Chronic open-angle glaucoma and ocular hypertension. An epidemiological study

Eccentricity Dependency of Retinal Electrophysiological Deficits in People With Episodic Migraine

Purpose

During the non-attack period, people with migraine may show retinal dysfunction. This study builds on previous work by exploring the possibility of foveal and non-foveal visual field and electroretinographic deficits and determining the overlap in eccentricity of such localized visual deficits in people with migraine.

Methods

Visual fields and multifocal electroretinography (mf-ERG) were tested in 27 people with migraine (aged 19-45 years) and 18 non-headache controls (aged 20-46 years). Data were averaged according to 5 concentric rings at < 1.5 degrees (foveal) and 5 degrees, 10 degrees, 15.5 degrees, and 22 degrees eccentricities (non-foveal). Linear mixed effects modelling was used to predict mf-ERG amplitude, mf-ERG peak time, and visual field sensitivity with fixed effects of eye, group, and eccentricity.

Results

Foveal mf-ERG responses, and visual field sensitivity across all eccentricities (foveal and non-foveal) were similar between the migraine and control groups (P > 0.05). In contrast, the non-foveal mf-ERG was reduced in amplitude in people with migraine relative to controls (P < 0.001), and this group difference depended on eccentricity (P < 0.001) - most prominently, in the parafoveal region (ring 2, P = 0.001).

Conclusions

Retinal electrophysiological deficits were observed in people with migraine in the parafoveal region (between 1.5 degrees and 5 degrees eccentricity), without corresponding visual field deficits. This suggests a spatially localized area of retinal neuronal dysfunction in people with migraine that is insufficient to manifest as a visual field sensitivity loss using standard perimetric methods. Our study highlights the added confound of migraine when conducting standard clinical retinal electrophysiological tests for conditions such as glaucoma, particularly non-foveally.

Smoking and progressive retinal nerve fibre layer thinning in glaucoma

BACKGROUND/AIMS

To investigate the relationship between smoking and smoking intensity, and the rate of retinal nerve fibre layer (RNFL) thinning in patients with primary open angle glaucoma (POAG).

METHODS

In this longitudinal study, patients with POAG who had at least 3 years of follow-up with a minimum of 5 visits of optical coherence tomography (OCT) were enrolled. The smoking intensity was calculated as the pack-year at the baseline OCT. Univariable and multivariable linear mixed models were used to determine the effect of each parameter on the rates of RNFL thinning over time. Non-linear least-squares estimation with piecewise regression model was used to investigate the cut-off point for the relationship between circumpapillary RNFL thinning and smoking intensity.

RESULTS

A total of 466 eyes of 314 patients were included over the mean (95% CI) follow-up of 6.6 (6.4 to 6.7) years. Of the 314 patients, 121 (39%) had reported any history of smoking. Greater smoking intensity was associated with faster RNFL thinning (-0.06 (95% CI -0.11 to 0.00) µm/year per 10 pack-year higher; p=0.031) after adjusted for confounding factors. RNFL thinning became significantly faster when smoking intensity was >8 pack-year.

CONCLUSIONS

Smoking intensity is associated with faster rates of RNFL thinning. Evaluation of smoking intensity might add information to the assessment of risk of glaucoma progression. Future studies are required to explore if withdrawing smoking as a modifiable risk factor can decrease progression in patients with glaucoma.

Impact of Smoking on Visual Field Progression in a Long-term Clinical Follow-up

PURPOSE

To investigate the effect of smoking on rates of progressive visual field (VF) damage over time in glaucoma.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Five hundred eleven eyes of 354 patients with glaucoma followed up from multicenter glaucoma registries.

METHODS

In this longitudinal study, 354 patients with primary open-angle glaucoma with a minimum of 3 years of follow-up and 5 VF tests were enrolled from the Diagnostic Innovations in Glaucoma Study and the African Descent and Glaucoma Evaluation Study. Univariate and multivariate linear mixed models were used to investigate the effects of smoking on rates of 24-2 VF mean deviation loss. Visual field progression was defined using pointwise linear and significant negative VF mean deviation loss. Logistic regression was used to identify baseline factors and whether different levels of smoking intensity were associated with VF progression. Kaplan-Meier survival analysis and the log-rank test were used to compare the cumulative risk ratio of progression between smoker and never smoker groups.

MAIN OUTCOME MEASURES

Visual field progression.

RESULTS

Five hundred eleven eyes of 354 patients were included over the median follow-up of 12.5 years. Median baseline age was 64.8 years. Of the 354 patients, 124 (35%) were Black, and 149 (42.1%) and 168 (59.8%) had reported a history of smoking or alcohol consumption, respectively. In a multivariate model, higher smoking intensity was associated with faster VF loss (coefficient, -0.05 decibels (dB)/year per 10 pack-years; 95% confidence interval [CI], -0.08 to -0.01 dB/year per 10 pack-years; P = 0.010). Developing VF progression in eyes of heavy smokers (≥ 20 pack-years) was 2.2 times more than in eyes of patients without smoking history (odds ratio, 2.21; 95% CI, 1.02-4.76; P = 0.044). Statistically significant differences were found between heavy smokers (≥ 20 pack-years) and never smokers by Kaplan-Meier analysis (P = 0.011, log-rank test).

CONCLUSIONS

Heavy smokers are more likely to sustain VF loss in eyes with glaucoma. The prospective longitudinal design of this study supports the hypothesis that levels of smoking may be a significant predictor for glaucoma progression. Additionally, this information can be used for clinically relevant tobacco prevention and intervention messages.

Relationship between blood pressure and intraocular pressure in the JPHC-NEXT eye study

Although a positive link between hypertension and intraocular pressure (IOP) has been suggested, the individual effects of systolic and diastolic blood pressure (SBP and DBP, respectively) on IOP remain unclear, particularly among Japanese populations. Here, we conducted a large-scale, cross-sectional study to determine individual and combined effects of SBP/DBP and hypertension on IOP. In total, 6783 Japanese people aged over 40 years underwent systemic and ophthalmological examinations, including measurements of blood pressure and IOP, conducted using non-contact tonometers. After adjusting for a priori known confounding factors, SBP and DBP levels were found to be positively correlated with IOP levels. The multivariable-adjusted odds ratio when comparing the hypertensive and normotensive groups for the prevalence of ocular hypertension was 1.88 (95% confidence interval, 1.14-3.08). When analysing the combined effects of SBP and DBP on ocular hypertension, SBP elevation had a greater effect on ocular hypertension than DBP increase. In conclusion, SBP and DBP levels and the prevalence of systemic hypertension were found to be positively associated with IOP levels and the prevalence of ocular hypertension in an ophthalmologically healthy Japanese population. Our findings suggest that systemic blood pressure control may be key for controlling IOP.

Ocular Surface Squamous Neoplasia Managed With Primary Interferon α2b: A Comparative Analysis of 212 Tumors in Smokers Versus Nonsmokers

PURPOSE

To explore clinical features and outcomes of ocular surface squamous neoplasia (OSSN) treated with primary interferon (IFN)-α2b, based on patient cigarette smoking status.

METHODS

Retrospective nonrandomized, interventional cohort study on 212 consecutive tumors in 194 patients, all of whom were treated with topical and/or injection IFNα2b.

RESULTS

There were 88 tumors in 76 patients with current or past smoking history (smokers) and 124 tumors in 118 nonsmoking patients (nonsmokers). A comparison (smokers vs. nonsmokers) revealed smokers with more frequent bilateral disease (16% vs. 3%, P = 0.003), more frequent involvement of inferior forniceal (34% vs. 21%, P = 0.03) and inferior tarsal conjunctiva (38% vs. 24%, P = 0.04), greater mean number of clock hour involvement (4.1 vs. 3.5 clock hours, P = 0.04), and greater dome growth pattern (30% vs. 15%, P = 0.01). There was no difference regarding method of IFNα2b administration as topical (61% vs. 71%, P = 0.14), injection (10% vs. 6%, P = 0.32), or combination topical/injection (28% vs. 23%, P = 0.33). A comparison revealed smokers with more frequent recurrence after initial response (23% vs. 13%, P = 0.04). There was no difference regarding initial tumor response or time to response, treatment side effects, or systemic outcomes.

CONCLUSIONS

Regarding ocular surface squamous neoplasia, smokers more often display bilateral, dome-shaped tumors with inferior forniceal or tarsal involvement, and greater extent than nonsmokers. After treatment with topical and/or injection IFNα2b, control is equivalent, but smokers show greater recurrence.

The eye in migraine: a review of retinal imaging findings in migraine

Migraine is a common headache disorder with neurovascular involvement. Because eyecare practitioners are likely to encounter people with migraine in their everyday practice, it is important to understand how migraine might impact on ocular health. In this narrative review, we provide an update on the latest ophthalmic imaging evidence for retinal involvement in migraine, derived from studies of retinal structure and retinal vascular perfusion using spectral domain and swept source optical coherence tomography (OCT) and OCT angiography. Combined structural OCT evidence from a recent meta-analysis indicates subtle and non-specific thinning of the peripapillary retinal nerve fibre layer (RNFL) in people with migraine, whereas there is little consistent evidence for structural abnormalities of the macular region. Recent advances in OCT angiography technology have also provided an opportunity to visualise microstructural damage and vascular dysregulation in the eyes of people with migraine. However, given that OCT and OCT angiography studies have been exclusively cross-sectional, it is not possible to demonstrate the causal effect of migraine events. Furthermore, the lack of common methodology (different ophthalmic imaging devices and analysis algorithms), and very limited datasets (small samples, heterogenous migraine groups), lead to an inability to make strong conclusions regarding the nature of altered retinal structure and vascular perfusion in migraine. Nevertheless, we discuss the clinical implications of such observations for eyecare practitioners and provide practical advice for the monitoring and management of patients with a history of migraine.

Oxidative Stress and the Role of NADPH Oxidase in Glaucoma

Glaucoma is characterised by loss of retinal ganglion cells, and their axons and many pathophysiological processes are postulated to be involved. It is increasingly understood that not one pathway underlies glaucoma aetiology, but rather they occur as a continuum that ultimately results in the apoptosis of retinal ganglion cells. Oxidative stress is recognised as an important mechanism of cell death in many neurodegenerative diseases, including glaucoma. NADPH oxidase (NOX) are enzymes that are widely expressed in vascular and non-vascular cells, and they are unique in that they primarily produce reactive oxygen species (ROS). There is mounting evidence that NOX are an important source of ROS and oxidative stress in glaucoma and other retinal diseases. This review aims to provide a perspective on the complex role of oxidative stress in glaucoma, in particular how NOX expression may influence glaucoma pathogenesis as illustrated by different experimental models of glaucoma and highlights potential therapeutic targets that may offer a novel treatment option to glaucoma patients.

Functional and Structural Changes of the Retinal Nerve Fiber Layer and Ganglion Cell Complex in Heavy Smokers

PURPOSE

To assess the functional and structural changes in the retinal nerve fiber layer (RNFL) and the ganglion cell complex (GCC) in heavy smokers using pattern electroretinogram (PERG), photopic negative response(PhNR) and spectral domain optical coherence tomography (SD-OCT).

PATIENTS AND METHODS

Sixty eyes of 30 heavy smokers (at least 15 cigarettes/day for 10 years) (study group) and 60 eyes of 30 age and gender-matched healthy non-smoker subjects (control group) were included. After full ophthalmologic examination (PERG), (PhNR) using RETI-port/scan 21 (Roland Consult, Brandenburg, Germany) and (SD-OCT using Topcon 3D OCT model 2000 FA version.8.30) were tested for all participants. Statistical analysis was performed to compare GCC, RNFL thicknesses, PERG and phNR values between groups.

RESULTS

The mean age was 36.67±4.13 years in the study group and 36.0±4.76 years in the control group. There were no statistical significant differences between the two groups regarding intraocular pressure (p=0.43), axial length (p=0.37), and central corneal thickness (p=0.86). There were significant differences of GCC thickness values between the study group (88.4±6.6 µm) and control group (94.83±5.25 µm) (p<0.001). The mean RNFL values of study and control groups were 97.87±5.88 and 106.43±6.59 µm, respectively (p<0.001). In the study group the superior and inferior quadrants of RNFL were significantly thinner, but there were no significant differences between the two groups in nasal and temporal quadrants. There were no significant differences of PERG-P50 amplitude (p=0.49) and latency (p=0.71); however, PERG-N95 amplitude and latency showed significant differences between the two groups (p<0.001).There were significant differences of phNR amplitude and latency between the two groups (p<0.001). Multiple regression analyses demonstrated that the PhNR, PERG amplitude and latency are the most important determinants for both RNFL and GCC thicknesses.

CONCLUSION

In heavy smokers RNFL thickness was decreased, the PhNR, PERG-N95 amplitudes were diminished and the implicit times were prolonged compared to non-smokers. PhNR and PERG reflect both dysfunction and loss of ganglion cells and their axons.

Heterogeneity in arterial hypertension and ocular perfusion pressure definitions: Towards a consensus on blood pressure-related parameters for glaucoma studies

PURPOSE

Glaucoma studies have long taken into account the blood pressure (BP) status of patients. This study summarizes and evaluates the impact of the different criteria that have been used for BP-related variables in glaucoma research.

METHODS

Studies included in two meta-analyses that reviewed the role of BP in glaucoma were analyzed. Additional studies published after the search periods of the meta-analyses were also included. Criteria for the definition of arterial hypertension and other BP-related variables, such as mean arterial pressure (MAP) and mean ocular perfusion pressure (MOPP), were retrieved.

RESULTS

Sixty-four studies were evaluated. One-third used 140 mmHg as a systolic BP cut-off to define hypertension, 20% used 160 mmHg and the remaining half used various other criteria. Less than 20% of studies reported MAP and/or MOPP. While eight of the ten studies reporting MAP used a correct formula that only happened for five of the eleven studies reporting MOPP. Using as an example average blood pressure values, incorrectly used formulas could have led to an overestimation of more than 100% of the expected values.

CONCLUSION

Considerable heterogeneity exists in BP-related variables in glaucoma research and different definitions can lead to large disparities. Glaucoma research would benefit from a consensus regarding blood pressure parameters.

Migraine as a risk factor for primary open angle glaucoma: A systematic review and meta-analysis

Migraine is increasingly being reported as a risk factor for primary open angle glaucoma (POAG). However, studies aimed to investigate this association yielded conflicting results. To assess the consistency of the data on the topic, we performed a systematic review and meta-analysis. A systematic literature search from Embase, Web of Science, and PubMed was performed to identify relevant studies on the relationship between migraine and POAG. Random effects models were used to estimate the pooled relative risks (RRs) with 95% confidence intervals (95% CIs) in this meta-analysis. A total of 11 studies meeting the inclusion criteria were included in this meta-analysis. Our findings showed an RR of developing POAG of 1.24 (95% CI = 1.12-1.37) in migraine patients. No evidence of significant heterogeneity was detected across studies (P = .071; I = 41.7%). This association was not modified by the glaucoma type of the included patients. A significant association was observed in case-control design studies, but not in cohort design studies. Little evidence of publication bias was found. The findings of this meta-analysis suggest that migraine can significantly increase the risk of the development of POAG. However, the cohort study design failed to identify this association. Whether migraines can significantly increase the risk of developing POAG is still controversial.

An Overview of the Eye in Diabetes

The three papers in this symposium are based on presentations to an RSM meeting on the Diabetic Eye, held on 9 April 2003. The matter is particularly topical because the National Service Framework for Diabetes calls for a high-quality retinal screening programme. After a review of the various ophthalmic conditions likely to be encountered in diabetic patients (A Negi, S A Vernon) we proceed to the most important, diabetic retinopathy, with a discussion of screening methods (D M Squirrell, J F Talbot) and an account of laser treatments (J G F Dowler). Colour versions of the clinical photographs are available online [www.jrsm.org]. Publication was coordinated by Professor Susan Lightman, of Moorfields Eye Hospital, London, UK.

The association between cigarette smoking and primary open-angle glaucoma: a systematic review

Glaucoma is one of the most common causes of irreversible blindness, globally. Findings from the Blue Mountain Eye Study suggest a moderate positive association between smoking and increased IOP (a significant risk factor for glaucoma). The previous two reviews investigating the association between smoking and primary open-angle glaucoma (POAG) show inconsistent findings and do not include recent studies investigating the dose-response effect of smoking. The current study aims to conduct an up-to-date, comprehensive evaluation of the existing literature. Identification of relevant existing literature was performed by an online search in MEDLINE for studies published from 1st January 1946 to 5th February 2015. The MESH headings (keywords) included "open-angle glaucoma" and "cigarette" or "smoking" or "tobacco". Two independent reviewers assessed the eligibility of each report based on predefined inclusion criteria. Odds ratios and 95 % confidence intervals (95 % CIs) were obtained from studies, for the change in risk of glaucoma due to both past and current smoking. Of the 26 abstracts reviewed, 17 papers were included in the final analysis. Nine of these were case-control studies, five cohort studies and three cross-sectional in design. Six of the case-control studies found a positive association between smoking and POAG, unlike the remaining studies. However, two relatively recent, large studies (including one prospective cohort study) investigating the effect of smoking dose have found a significant increase in risk of POAG in very heavy smokers. There is limited evidence for a causal association between tobacco smoking and POAG. The evidence for a link between current smoking and POAG appears stronger than that of past smoking, but recent studies suggest that heavy smoking may increase the risk of POAG. Future studies must further investigate the possible positive association between heavy smoking and POAG by stratifying participants by pack years and age.

Smoking and incidence of glaucoma: The SUN Cohort

Smoking is a serious global public health concern that has been related to many chronic diseases. However, the effect of smoking on eye disorders has been less studied. The aim of this cohort study was to assess the association between current tobacco smokers and the risk of developing glaucoma and furthermore to evaluate the relationship between passive or former smokers and glaucoma.In this prospective and dynamic cohort, 16,797 participants initially who were found not to have glaucoma were followed up for a median of 8.5 years. Validated data on lifestyle, including tobacco consumption, were assessed at baseline. Information about new diagnosis of glaucoma was collected by follow-up questionnaires every 2 years. The outcome was the incidence of self-reported glaucoma during the follow-up. A subsample was used to validate the glaucoma diagnosis.During the 8.5 years of follow-up, 184 new glaucoma cases were identified. Current smokers had a significantly higher risk of glaucoma compared to participants who had never smoked after controlling for potential confounders (Hazard ratio [HR] 1.88 [95% coefficient interval (CI): 1.26-2.81]; P = 0.002). A nonsignificant increased risk was found among former smokers (HR 1.27 [95% CI: 0.88-1.82]; P = 0.198). When we assessed the exposure as per the number of cigarette pack-years, a dose-response relationship between pack-years and the risk of glaucoma was found (HR for the 5th quintile versus the 1st quintile: 1.70 [95% IC: 1.10-2.64], P for trend, 0.009). However, no relationship was found between passive smokers and glaucoma. (HR 0.67 [95% CI: 0.37-1.21]; P = 0.189).Our results suggest a direct association between current smokers and the incidence of glaucoma. In particular, this association was related to the number of pack-years, which was not found in the case of former smokers nor in the case of passive smokers.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The longitudinal changes of retinal nerve fiber layer thickness after panretinal photocoagulation in diabetic retinopathy patients

PURPOSE

To investigate longitudinal changes in retinal nerve fiber layer (RNFL) thickness after panretinal photocoagulation (PRP) in diabetic retinopathy patients.

METHODS

This prospective study examined 31 eyes in 25 patients undergoing PRP, who were diagnosed with severe nonproliferative diabetic retinopathy or non-high-risk proliferative diabetic retinopathy. Optical coherence tomography was conducted before PRP and at 3, 6, 12, and 24 months after PRP to investigate changes in peripapillary RNFL thickness.

RESULTS

Superior, nasal, inferior, temporal, and mean peripapillary RNFL thickness increased until 6 months after PRP and then decreased. Superior RNFL thickness increased significantly at 3 and 6 months and decreased significantly at 24 months compared with the baseline RNFL thickness. Nasal RNFL thickness declined significantly at 24 months compared with the baseline RNFL thickness without any significant increase in thickness during the follow-up period. Inferior RNFL thickness increased significantly at 6 months and decreased significantly at 24 months compared with its baseline RNFL thickness. Temporal thickness increased significantly at 3, 6, 12, and 24 months compared with the baseline RNFL thickness. Mean RNFL thickness increased significantly at 6 months and decreased significantly at 24 months. Central subfield thickness increased significantly at 3, 6, 12, and 24 months compared with its baseline thickness.

CONCLUSION

Peripapillary RNFL thickness increased at 6 months after PRP and then decreased at 24 months after PRP compared with baseline peripapillary RNFL thickness in diabetic retinopathy patients. This finding suggests that in addition to diabetes itself, diabetic retinopathy, and associated glaucoma, PRP may be a cause of RNFL thickness loss in patients with diabetes.

Absence of altered expression of optineurin in primary open angle glaucoma patients

PURPOSE

To investigate the expression level of the optineurin gene (OPTN) in the blood of primary open angle glaucoma (POAG) patients to determine if altered expression is playing a role in primary open angle glaucoma systemically.

METHODS

Patients (n=47) were eligible for inclusion if they met standard clinical criteria for POAG, including age greater than 40 years, intraocular pressure ≥21 mmHg in at least one eye before treatment, normal-appearing anterior chamber angles bilaterally on gonioscopy, and optic nerve injury characteristic of POAG. Control subjects (n=27) were recruited who were free from glaucoma by examination. DNA from patient was sequenced to look for possible mutations in the coding region of OPTN or its promoter. RNA was extracted from leukocytes of patients and controls and converted to cDNA by reverse transcriptase enzyme, and quantitative PCR was used to assess expression levels of OPTN and the β-globulin gene. The ratio of OPTN expression to β-globulin gene expression for POAG patients was compared to that of controls and to clinical characteristics of POAG patients.

RESULTS

No mutation(s) were detected in any of the patients after sequencing the full OPTN gene and its promoter region. Mean OPTN (p≤0.35), and β-globulin (p≤0.48) gene expression values were statistically similar in POAG patients and controls. OPTN/β-globulin (p≤0.83) ratios were also indistinguishable between POAG patients and controls. OPTN/β-globulin ratios were not significantly associated with age, sex, or ethnicity of patients within the POAG group. Similarly, OPTN/β-globulin ratios were not significantly affected by ethnicity or clinical parameters related to POAG severity including maximum intraocular pressure, vertical cup-to-disk ratio, static perimetry mean deviation, or static perimetry pattern standard deviation.

CONCLUSIONS

OPTN expression is not altered in the blood of POAG patients, suggesting that OPTN expression is not changed systemically and implying that other mechanisms are involved in POAG pathogenesis.

A prospective study of diabetes, lifestyle factors, and glaucoma among African-American women

PURPOSE

To evaluate the association of self-reported type 2 diabetes, anthropometric factors, alcohol consumption, and cigarette smoking with risk of primary open-angle glaucoma (POAG) in a prospective cohort study of African-American women.

METHODS

From 1995 through 2007, 32,570 Black Women's Health Study participants aged 21 to 69 years at baseline were followed for incident POAG. Questionnaires were mailed biennially to update exposures and identify incident cases of POAG. Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were derived from Cox regression models.

RESULTS

During 416,171 person-years of follow-up, 366 incident POAG cases were confirmed by physician report. After adjustment for potential confounders, the IRR comparing women with and without type 2 diabetes was 1.58 (95% CI, 1.17-2.13), and the IRR comparing current with never alcohol consumers was 1.35 (95% CI, 1.05-1.73). Among women younger than 50, associations with diabetes and alcohol consumption were stronger, and POAG was significantly associated with body mass index, waist circumference, waist-to-hip ratio, and both long-duration and high-intensity current smoking.

CONCLUSIONS

These results suggest that type 2 diabetes and current alcohol consumption are independent risk factors for POAG among African-American women, and that in addition to those factors, overall and central adiposity and smoking may be associated with increased risk of early-onset POAG.

Down-regulation of OPA1 in patients with primary open angle glaucoma

PURPOSE

Heterozygous optic atrophy type1 (OPA1) mutations are responsible for dominant optic atrophy, and the down regulation of OPA1 expression in patients with Leber hereditary optic neuropathy may imply that Opa1 protein levels in mitochondria play a role in other spontaneous optic neuropathies as well. Mitochondrial and metabolic abnormalities may put the optic nerve at risk in primary open angle glaucoma (POAG), and this preliminary study was designed to investigate whether altered OPA1 expression might be present in the progressive optic neuropathy of POAG.

METHODS

Patients were eligible for inclusion if they met standard clinical criteria for POAG, including age greater than 40 years, intraocular pressure ≥ 21 mmHg in at least one eye before treatment, normal-appearing anterior chamber angles bilaterally on gonioscopy, and optic nerve injury characteristic of POAG. RNA was extracted from leukocytes and converted to cDNA by reverse transcriptase enzyme, and real time PCR was used to assess expression levels of OPA1 and the β-globulin (HBB) housekeeping gene. The ratio of OPA1 expression to HBB expression (OPA1/HBB) for POAG patients was compared to that of controls and to clinical characteristics of POAG patients.

RESULTS

Forty-three POAG patients and 27 controls were completely phenotyped with a full ophthalmologic examination and static perimetry. Mean age (POAG 67.9 years; controls 61.8 years) and sex (POAG 26 males/17 females; controls 11/16) were similar for the two groups. Mean OPA1/HBB of POAG patients (1.16, SD 0.26) was 18% lower than controls (1.41, SD 0.50), and this difference was statistically significant (p≤0.021). OPA1 expression differed between the groups (p≤0.037), but HBB expression did not differ (p≤0.24). OPA1/HBB was not correlated with any clinical feature of POAG patients.

CONCLUSIONS

Transcriptional analysis of peripheral blood leucocytes is a limited model system for studying the consequences of mitochondrial abnormalities in the optic nerve. Nevertheless, OPA1 is known to affect mitochondrial stability and has now been implicated in several spontaneous optic neuropathies. Decreased OPA1 expression in POAG patients is another indication that mitochondrial function, and possibly mitochondrially-induced apoptosis, may play a role in the development of POAG.

Intraocular pressure fluctuations in professional brass and woodwind musicians during common playing conditions

BACKGROUND

We investigated the effects on intraocular pressure (IOP) and blood pressure (BP) of playing brass and woodwind instruments by monitoring IOP and BP in a representative group of professional musicians under a variety of common playing conditions.

METHODS

IOP and BP measurements were recorded from 37 brass and 15 woodwind instrument players, before and after playing tones of low, middle and high frequency. We also measured IOP and BP before and during playing common exercises of 10 minutes duration, as well as after playing a sustained high-pitched tone, to test for changes in IOP under conditions of maximum effort.

RESULTS

Playing tones on brass and woodwind instruments causes a temporary elevation in IOP and BP, depending on the tone frequency: brass instrument players showed a significant elevation after playing high and middle frequency tones (p < 0.0001) whereas woodwind instrument players showed a significant increase only for high frequencies (e.g., oboe, 17 ± 2.9 mm Hg to 21 ± 4.4 mm Hg; p = 0.017). Playing a typical exercise of 10 minutes temporarily increased IOP in both groups of musicians. Finally, playing a sustained tone of high pitch caused a significant elevation in IOP in brass instrument players only (16.6 ± 3.5 mm Hg to 23.3 ± 8.9 mm Hg; p < 0.0001).

CONCLUSIONS

The temporary and sometimes dramatic elevations and fluctuations in IOP observed in this study, coupled with daily exposure to instrument play, puts professional wind instrument players at increased risk of developing glaucoma. Consequently, these musicians should be monitored for signs of glaucoma, especially those with co-existing risk factors.

OPA1 increases the risk of normal but not high tension glaucoma

BACKGROUND

Primary open angle glaucoma is a progressive optic neuropathy characterised by the selective loss of retinal ganglion cells, pathological optic disc cupping and visual field defects. The OPA1 gene encodes an inner mitochondrial membrane protein crucial for normal mitochondrial function, and pathogenic mutations cause autosomal dominant optic atrophy by specifically targeting retinal ganglion cells. This raises the distinct possibility that more subtle genetic variations in OPA1 could alter the risk of developing glaucoma.

METHODS

137 patients with primary open angle glaucoma (67 patients with high-tension glaucoma (HTG), 70 patients with normal-tension glaucoma (NTG)) and 75 controls from the North East of England were studied. Three single-nucleotide polymorphisms in intron 8 (IVS8+4c-->t and IVS8+32t-->c) and exon 4 (c.473A-->G) of the OPA1 gene were genotyped in the study group. In addition, the entire OPA1 coding region was sequenced in 24 individuals with the CT/TT compound genotype using standard BigDye chemistries.

RESULTS

There was no difference in either allele or genotype frequency for the IVS8+32t-->c single-nucleotide polymorphisms between patients and controls, but there was a significant association between the T allele at IVS8+4c-->t and the risk of developing NTG (OR=2.04, 95% CI=1.10 to 3.81, p=0.004), but not HTG. Logistic regression analysis also confirmed a strong association between the CT/TT compound genotype at IVS8+4 and IVS8+32 with NTG (OR=29.75, 95% CI=3.83 to 231.21, p=0.001).

CONCLUSIONS

The CT/TT compound genotype at IVS8+4 and IVS8+32 is a strong genetic risk determinant for NTG but not HTG.

Mitochondrial haplogroup U is associated with a reduced risk to develop exfoliation glaucoma in the German population

Background

Various lines of evidence demonstrate the involvement of mitochondrial dysfunction in the pathogenesis of glaucoma. Therefore, mitochondrial DNA is a promising candidate for genetic susceptibility studies on glaucoma. To test the hypothesis that mitochondrial haplogroups influence the risk to develop glaucoma, we genotyped 12 single-nucleotide polymorphisms that define the European mitochondrial DNA haplogroups in healthy controls and two German patient cohorts with either exfoliation glaucoma or the normal tension subgroup of primary open angle glaucoma.

Results

Mitochondrial haplogroup U was significantly under-represented in patients with exfoliation glaucoma (8.3% compared with 18.9% in controls; p = 0.004).

Conclusions

People with haplogroup U have a lower risk to develop exfoliation glaucoma. Our results substantiate the suggestion that mitochondrial alterations have an impact on the etiology of glaucoma.

Lifestyle, nutrition, and glaucoma

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

Twenty-four hour blood pressure pattern in patients with normal tension glaucoma in the habitual position

PURPOSE

To investigate the relationship between blood pressure (BP) parameters in the habitual position and glaucomatous damage at initial presentation in patients with untreated normal tension glaucoma (NTG).

METHODS

Fifty-four eyes from 54 subjects diagnosed with NTG were consecutively enrolled. BP was measured with an automated ambulatory monitoring device in the habitual position during 24-hour in-hospitalization. Patients were classified into three groups: non-dippers, dippers, and over-dippers. corresponded to the degree of reduction in their nocturnal mean arterial pressure (MAP) compared with their diurnal MAP. Regression models were used to evaluate potential risk factors, including: age, pre-admission office intraocular pressure (IOP), central corneal thickness (CCT), and BP parameters. Functional outcome variables for glaucomatous damage included mean deviation (MD) and pattern standard deviation (PSD) on a Humphrey field analyzer (HFA). Anatomic outcome variables were TSNIT score (temporal, superior, nasal, inferior, and temporal) average, superior average, inferior average, and nerve fiber indicator (NFI) score on scanning laser polarimetry with variable corneal compensation (SLP-VCC; GDx-VCC).

RESULTS

Marked systolic blood pressure (SBP), diastolic blood pressure (DBP), and MAP fluctuation were noted in the over-dipper group (p<0.05). A linear regression analysis model revealed that nocturnal trough DBP and MAP, average nocturnal SBP, and MAP were all significantly associated with a decreased average TSNIT score and an increased NFI score.

CONCLUSIONS

Nocturnal BP reduction estimated in the habitual position was associated with structural damage in eyes with NTG. This finding may suggest systemic vascular etiology of NTG development associated with nocturnal BP reduction.

Cigarette smoking and primary open angle glaucoma: a systematic review

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

What can we learn from the disc appearance about the risk factors in glaucoma?

The author has been involved in 3 studies, the multicentre collaborative normal-tension glaucoma study, a study of 4 phenotypes of glaucomatous disc appearances and their associations, and a study reporting on biostatistical evidence for 2 distinct chronic open-angle glaucoma populations. These studies have some common threads whose clinical implications are discussed.

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

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

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

PURPOSE

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

DESIGN

Population-based cohort study.

PARTICIPANTS

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

METHODS

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

MAIN OUTCOME MEASURES

Open-angle glaucoma and OHT.

RESULTS

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

CONCLUSIONS

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

The role of mitochondrial haplogroups in primary open angle glaucoma

AIM

To investigate a possible association between mitochondrial haplogroups and primary open angle glaucoma (POAG).

METHODS

Genomic DNA was extracted from 140 POAG patients and 75 healthy individuals. Restriction enzyme digest analysis of polymerase chain reaction (PCR) amplified fragments was used to determine the mitochondrial haplogroup of each patient and control.

RESULTS

The median age was 73 years for the POAG patients (range 51-87, SD 8.01) and 78 years for the controls (range 68-90, SD 4.4). Mean IOP was 20.8 mm Hg for the patients (SD 2.6) and 16.2 mm Hg for the controls (SD 3.4). Median cup/disc ratio was 0.8 and 0.3 for patients and controls respectively. No statistically significant difference was found in the haplogroup distribution between the POAG patients and the healthy individuals (Fisher's exact test).

CONCLUSION

In this cohort, mitochondrial haplogroups do not appear to contribute to the pathogenesis of POAG.

Diabetes mellitus as a risk factor for glaucomatous optic neuropathy

Open-angle glaucoma (OAG) is an optic neuropathy characterized by progressive retinal ganglion cell (RGC) death and optic disk excavation. Evidence is accumulating that RGC apoptosis is the fundamental pathology of OAG. Among several risk factors for development and progression of OAG, inclusion of comorbid diabetes has been controversial. Some large population-based prevalence and incidence studies found a positive association between diabetes and OAG, whereas others did not. This inconsistency is derived from selection-, recall-, or survival-bias or misclassification due to low incidence of the two diseases. On the other hand, recent basic studies have shown that diabetes not only affects vascular tissues but also compromises neuronal and glial functions and metabolism in the retina, which ultimately gives rise to apoptotic death of retinal neurons including RGCs. The impaired metabolism of neurons and glia by diabetes may render RGCs susceptible to additional stresses related to OAG such as elevated intraocular pressure. In fact, our latest data demonstrate that retinas taken from rats with streptozotocin-induced diabetes, which underwent cauterization of three episcleral veins to become a chronic glaucoma model, had significantly more apoptotic cells than those from rats with diabetes alone or with chronic glaucoma alone. In this regard, diabetes is a 'risk factor' for glaucomatous optic neuropathy. Additionally, prospective studies are needed to determine if OAG patients with diabetes have a more aggressive course than those without diabetes.

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.

Epidemiological association between cigarette smoking and primary open-angle glaucoma: a meta-analysis

OBJECTIVE

The role of cigarette smoking as a risk factor for primary open-angle glaucoma (POAG) remains controversial. The aim of this study was to examine this association by conducting a detailed meta-analysis of studies published in peer-reviewed literature on the subject.

METHODS

A comprehensive search for articles published up 31 December 2002 was performed, reviews of each study were conducted, and data were abstracted. Prior to meta-analysis, the studies were evaluated for publication bias and heterogeneity.

RESULTS

Our analysis was based on seven reports. We found no evidence of publication bias or heterogeneity among the studies. The summary odds ratios from a fixed-effects model were 1.37 (95% CI: 1.00-1.87) for current smokers and 1.03 (95% CI: 0.77-1.38) for past smokers.

CONCLUSIONS

Our meta-analysis results suggest that current smokers are at significantly increased risk of developing POAG. Efforts should be directed towards augmenting the campaign against smoking by adding the increased risk of POAG to the better-known arguments against smoking.

Longevity-associated mitochondrial DNA 5178 A/C polymorphism is associated with intraocular pressure in Japanese men

BACKGROUND

Mitochondrial DNA 5178 adenine/cytosine (mt5178 A/C) polymorphism has been reported to be associated with longevity in Japanese individuals, with experimental findings concluding that mt5178 A is an anti-atherogenic genotype. The aim of this study was to determine whether mt5178 A/C polymorphism influences intraocular pressure (IOP), and its relationship with the development of arteriosclerosis.

METHODS

Four hundred and forty-nine male volunteers who had visited a general hospital for medical check-up between August 1999 and August 2000 were enrolled. Of these, 386 Japanese men who had not undergone any medical treatment for hypertension, ocular hypertension or glaucoma were selected as subjects of this study. After these subjects were genotyped, a cross-sectional study regarding the relationship between genotype and IOP was conducted.

RESULTS

Mean IOP was significantly higher in men with mt5178 C (13.3 mmHg) than in those with mt5178 A (12.7 mmHg) (P = 0.037). This significant difference in mean IOP between the two genotypes remained evident after adjusting for age, body mass index, blood pressure, habitual smoking and habitual drinking. Interactions between mt5178 A/C polymorphism and habitual smoking or daily alcohol consumption with regard to IOP were observed. According to multiple regression analysis, habitual smoking was significantly associated with IOP in men with mt5178 A (P for trend = 0.020), while daily alcohol consumption was significantly associated with IOP in those with mt5178 C (P for trend = 0.021).

CONCLUSION

Longevity-associated mitochondrial DNA 5178 A/C polymorphism may be associated with IOP in Japanese men.

Risk factors for progressive visual field loss in primary open angle glaucoma

PURPOSE

The aim of this study was to evaluate routine ophthalmic data to identify clinically useful risk factors for progressive visual field loss in patients with primary open-angle glaucoma (POAG) already receiving intraocular pressure-lowering treatments.

METHODS

A retrospective cohort study design was used. Routine ophthalmic data for all subjects were obtained from case records with the knowledge that baseline clinical data had been collected in a standardised manner. Progression was defined according to the AGIS visual field defect scoring system. Variables evaluated as candidate risk factors for progression were assessed by survival analysis. Factors exerting a significant effect on survival were subsequently tested in a Cox proportional hazards model.

RESULTS

A cohort of 108 eligible POAG patients was followed over an average of 3.6 years, with an average visual field intertest interval of 8 months. The incidence rate of progressive loss among the cohort was 5.4 cases per 100 person years. Increasing age was found to be independently associated with a small but significantly increased risk of glaucomatous visual field defect progression (hazard ratio 1.07, P=0.022), and a borderline association was also demonstrated with being male (hazard ratio 2.76, P=0.057).

CONCLUSIONS

This retrospective investigation has provided preliminary information on factors associated with increased risk of progressive glaucomatous visual field loss that may inform clinical care strategies. Lack of concordance with other studies suggests that further prospective investigations are needed if risk stratification strategies are to be employed in caring for patients with chronic open-angle glaucoma.

Diabetes mellitus as a risk factor for primary open-angle glaucoma: a meta-analysis

AIM

The association of diabetes mellitus with primary open-angle glaucoma has been controversial. The study aimed to examine the strength of this association through a detailed meta-analysis of studies published in peer-reviewed journals.

METHODS

A comprehensive search for articles published through 2002 was performed and data were abstracted. Prior to meta-analysis, all studies were evaluated for publication bias and heterogeneity. Pooled odds ratio (OR) was calculated using the random and the fixed-effects model.

RESULTS

Twelve studies published between 1987 and 2001 were included (five case-control studies and seven cross-sectional studies). Significant heterogeneity among the studies was detected (P = 0.023). No evidence of publication bias was found (P = 0.37). The association of diabetes mellitus with primary open-angle glaucoma was statistically significant assuming either a random effects [OR = 1.50, 95% confidence interval (CI) 1.16, 1.93], or a fixed-effects model (OR = 1.27, 95% CI 1.10, 1.45).

CONCLUSIONS

Our meta-analysis results suggest that diabetic patients are at significantly increased risk of developing primary open-angle glaucoma. Clinicians should be aware of this possibility.

An overview of the eye in diabetes

The three papers in this symposium are based on presentations to an RSM meeting on the Diabetic Eye, held on 9 April 2003. The matter is particularly topical because the National Service Framework for Diabetes calls for a high-quality retinal screening programme. After a review of the various ophthalmic conditions likely to be encountered in diabetic patients (A Negi, S A Vernon) we proceed to the most important, diabetic retinopathy, with a discussion of screening methods (D M Squirrell, J F Talbot) and an account of laser treatments (J G F Dowler). Colour versions of the clinical photographs are available online [www.jrsm.org]. Publication was coordinated by Professor Susan Lightman, of Moorfields Eye Hospital, London, UK.

Does smoking affect intraocular pressure? Findings from the Blue Mountains Eye Study

PURPOSE

To assess the relationship between smoking and intraocular pressure.

MATERIALS AND METHODS

The Blue Mountains Eye Study examined 3654 residents aged 49 years and older in an area west of Sydney, Australia from 1992 to 1994. A trained interviewer collected a detailed history of smoking. Intraocular pressure was measured using Goldmann applanation tonometry; as the correlation between right and left eyes was very high, only right-eye data are presented. Participants using glaucoma medications or who had evidence of previous cataract surgery were excluded.

RESULTS

Current smokers (15.8% of participants) had slightly higher mean intraocular pressures (16.34 mm Hg) than nonsmokers (16.04 mm Hg). Intraocular pressure (in the right eye) was significantly associated with current smoking, after adjusting for age and sex (P = 0.03). This association remained unchanged after simultaneous adjustment for other variables associated with intraocular pressure, including blood pressure, diabetes, myopia, glaucoma, family history, and pseudoexfoliation (P = 0.02).

CONCLUSIONS

This study identified a modest cross-sectional positive association between current smoking and intraocular pressure.

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.

Intraobserver reproducibility of a two-dimensional mapping of the optic nerve head perfusion

PURPOSE

To evaluate the intraobserver reproducibility of a software designed to assess retinal blood flow with the Heidelberg Retina Flowmeter (HRF).

METHODS

Ten subjects were consecutively recruited, and one eye of each patient was randomly selected for study. Blood flow measurements were analyzed by using an automatic full field perfusion image analysis (AFFPIA) program, which calculates the Doppler frequency shift and hemodynamic variables (flow, volume, and velocity) for each pixel. The resulting perfusion image is processed with respect to underexposed and overexposed pixels, saccades, and retinal vessel tree. Intraobserver reproducibility was calculated for the AFFPIA program. All the optic nerve heads were horizontally divided into three sections (superior, central, and inferior). The retinal blood flow was calculated in the superior and inferior section, and each section was further divided into three areas (temporal, nasal, and rim). The blood flow was evaluated for each area.

RESULTS

When the same observer analyzed the same image five times (intraobserver intraimage reproducibility), the AFFPIA coefficient of variation ranged from 0.5% to 5% in the temporal area, from 0.1% to 5.3% in the nasal area, and from 0.5 to 28% in the rim area. When the same observer analyzed three different images of the same section once (intraobserver interimage reproducibility), the AFFPIA coefficient of variation of flow measurements ranged from 1% to 7.3% in the temporal area, from 1.5% to 10% in the nasal area, and from 2 to 30% in the rim area.

CONCLUSION

Retinal blood flow measured by HRF and analyzed by AFFPIA had good intraobserver reproducibility. The reproducibility was significantly better in the temporal and nasal areas than in the rim area.

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.

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.

Glaucoma incidence in an unselected cohort of diabetic patients: is diabetes mellitus a risk factor for glaucoma? DARTS/MEMO collaboration. Diabetes Audit and Research in Tayside Study. Medicines Monitoring Unit

AIMS

To evaluate whether diabetes mellitus is a risk factor for the development of primary open angle glaucoma or ocular hypertension (OHT).

METHODS

A historical cohort study of an unselected population comprising all residents of the Tayside region of Scotland was performed using record linkage techniques followed by case note review. Ascertainment of prevalent diabetes was achieved using the Diabetes Audit and Research in Tayside Study (DARTS) validated regional diabetes register. Glaucoma and treated OHT were defined by encashment of community prescriptions and the statutory surgical procedure coding database.

RESULTS

The study population comprised 6631 diabetic subjects and 166 144 non-diabetic subjects aged >40 years without glaucoma or OHT at study entry. 65 patients with diabetes and 958 without diabetes were identified as new cases of glaucoma or treated OHT during the 24 month study period, yielding a standardised morbidity ratio of 127 (95% CI, 96-158). Case note review demonstrated non-differential misclassification of prevalent glaucoma and OHT as incident disease (diabetic cohort 20%, non-diabetic cohort 24%; p=0.56) primarily as a result of non-compliance in medically treated disease. Removing misclassified cases and adjusting for age yielded an incidence of primary open angle glaucoma in diabetes of 1.1/1000 patient years (95% CI, 0.89-1. 31) compared to 0.7/1000 patient years (95% CI, 0.54-0.86) in the non-diabetic cohort; RR 1.57 (95% CI, 0.99-2.48).

CONCLUSIONS

This study failed to confirm an association between diabetes mellitus and primary open angle glaucoma and ocular hypertension. A non-significant increase in diagnosed and treated disease in the diabetic population was observed, but evidence was also found that detection bias contributes to this association.