Platelet function, blood coagulability, and fibrinolysis in patients with low tension glaucoma

Association between coagulation function and patients with primary angle closure glaucoma: a 5-year retrospective case-control study

OBJECTIVE

To evaluate the association between coagulation function and patients with primary angle closure glaucoma (PACG).

DESIGN

A retrospective, hospital-based, case-control study.

SETTING

Shanghai, China.

PARTICIPANTS

A total of 1778 subjects were recruited from the Eye & ENT Hospital of Fudan University from January 2010 to December 2015, including patients with PACG (male=296; female=569) and control subjects (male=290; female=623).

OUTCOME MEASURES

Sociodemographic data and clinical data were collected. The one-way analysis of variance test was used to compare the levels of laboratory parameters among the mild, moderate and severe PACG groups. Multivariate logistic regression analyses were performed to identify the independent risk factors for PACG. The nomogram was constructed based on the logistic regression model using the R project for statistical computing (R V.3.3.2).

RESULTS

The activated partial thromboplastin time (APTT) of the PACG group was approximately 4% shorter (p<0.001) than that of the control group. The prothrombin time (PT) was approximately 2.40% shorter (p<0.001) in patients with PACG compared with the control group. The thrombin time was also approximately 2.14% shorter (p<0.001) in patients with PACG compared with the control group. The level of D-dimer was significantly higher (p=0.042) in patients with PACG. Moreover, the mean platelet volume (MPV) of the PACG group was significantly higher (p=0.013) than that of the control group. A similar trend was observed when coagulation parameters were compared between the PACG and control groups with respect to gender and/or age. Multiple logistic regression analyses revealed that APTT (OR=1.032, 95% CI 1.000 to 1.026), PT (OR=1.249, 95% CI 1.071 to 1.457) and MPV (OR=1.185, 95% CI 1.081 to 1.299) were independently associated with PACG.

CONCLUSION

Patients with PACG had a shorter coagulation time. Our results suggest that coagulation function is significantly associated with patients with PACG and may play an important role in the onset and development of PACG.

A Sick Eye in a Sick Body? Systemic Findings in Patients with Primary Open-angle Glaucoma

Despite intense research, the pathogenesis of primary open-angle glaucoma (POAG) is still not completely understood. There is ample evidence for a pathophysiological role of elevated intraocular pressure; however, several systemic factors may influence onset and progression of the disease. Systemic peculiarities found in POAG include alterations of the cardiovascular system, autonomic nervous system, immune system, as well as endocrinological, psychological, and sleep disturbances. An association between POAG and other neurodegenerative diseases, such as Alzheimer disease and Parkinson disease, has also been described. Furthermore, the diagnosis of glaucoma can affect the patient's quality of life. By highlighting the systemic alterations found in POAG, this review attempts to bring glaucoma into a broader medical context.

Plasma vascular endothelial growth factor, soluble VEGF receptor FLT-1, and von Willebrand factor in glaucoma

AIM

To investigate plasma indices of vascular permeability (vascular endothelial growth factor, VEGF-also an index of angiogenesis, as well as the soluble receptor for VEGF, sFlt-1) and endothelial damage/dysfunction (von Willebrand factor, vWf) in glaucoma.

METHODS

Citrated plasma was assayed for VEGF, sFlt-1, and vWf (all ELISA) in a cross sectional study of 50 patients (20 male; mean age 63.9 years, SD 10.5) with glaucoma: 26 had normal tension glaucoma (NTG) and 24 had primary open angle glaucoma (POAG), who were compared with 26 healthy controls (mean age 73.4 years, SD 9.2).

RESULTS

Median (interquartile range, IQR) levels of VEGF were significantly elevated in patients with NTG and POAG compared to healthy controls (Kruskal-Wallis test, p<0.001). Similarly, mean (SD) vWF levels were abnormal in NTG and POAG compared to healthy controls (one way ANOVA, p<0.001). Median levels of sFlt-1 were significantly lower in patients with NTG and POAG, when compared to healthy controls (Kruskal-Wallis test, p<0.001; p<0.05 with Tukey's post hoc test for controls v POAG). There were no significant differences in VEGF, sFlt-1 or vWf levels between the NTG and POAG groups (Tukey's test, all p=NS). In both NTG and POAG groups, there was a significant correlation between VEGF and sFlt-1 (Spearman, NTG: r=0.6517, p=0.001; POAG: r=0.6017, p=0.008). There were no significant correlations between VEGF and sFlt-1, or with vWf among the controls.

CONCLUSIONS

The pathogenesis of optic nerve damage in both NTG and POAG may be associated with abnormal vascular permeability and endothelial damage/dysfunction, as indicated by abnormal plasma VEGF and vWf levels in these patients.

Normal tension glaucoma and primary open angle glaucoma associated with increased platelet aggregation

On purpose of the present study was to evaluate platelet aggregation and fibrinolytic systems in patients with normal tension glaucoma (NTG) or primary open angle glaucoma (POAG). For platelet aggregation, we photoelectrophotometrically investigated adenosine diphosphate (ADP) or collagen-induced platelet aggregation in consecutively selected patients with glaucoma (22 patients with NTG and 13 patients with POAG) and 42 glaucoma free control subjects with normal ocular findings. The aggregation patterns of the patients' platelets reacted abnormally to ADP 1 microM or collagen 0.5 microg/ml as evidenced by secondary aggregation were compared with those of control subjects. For blood coagulative and fibrinolytic systems, we measured prothrombin time, activated partial thromboplastin time, fibrinogen, thrombin-antithrombin III complex (TAT), alpha2 plasmin inhibitor-plasmin complex. Seventeen of 22 patients (77%) with NTG and 5 of 13 patients (38%) with POAG showed abnormal secondary aggregation. A significant difference was observed between the two groups. No control subjects showed abnormal secondary aggregation. In the fibrinolytic test, all the parameters examined showed within normal ranges, although the log10(TAT) value was higher in NTG than in POAG. Results of the present study suggested that increased platelet aggregation as defined by ADP or collagen induced abnormal secondary aggregation in vitro is frequently associated with glaucoma patients and this tendency is more apparent in NTG than that in POAG.

Circulating platelet aggregates in glaucoma

PURPOSE

The aim of the study was to assess the role of circulating platelet aggregates (CPA) in advanced glaucoma.

METHOD

CPA was determined in vivo in 32 patients with advanced open-angle glaucoma accompanied by visual field loss, and in 20 healthy volunteers. The platelet aggregate ratio in glaucoma patients was significantly higher than those of normal controls (p = 0.002).

CONCLUSIONS

Our study indicates that measurement of platelet aggregate ratio might be used as an exploratory tool to assess the role of atherothrombotic events in glaucoma.

The role of age and cardiovascular disease in glaucomatous optic neuropathy

The role of systemic cardiovascular disorders in glaucomatous optic neuropathy was studied experimentally in rhesus monkeys and clinically in humans. These studies suggest that, in the multifactorial phenomenon of glaucomatous optic neuropathy, among other risk factors, age, cardiovascular disease and nocturnal arterial hypotension may play an important role in the development and progression of glaucomatous optic neuropathy in many cases, independent of intraocular pressure. In glaucomatous optic neuropathy, age may be an indirect index of cardiovascular disease rather than an independent factor per se. Nocturnal arterial hypotension, particularly among hypertensive patients taking oral hypotensive medication, may be an important risk factor. Because 24-hour ambulatory blood pressure monitoring is becoming popular among ophthalmic researchers, multiple confounding factors in ambulatory blood pressure monitoring in patients with optic nerve head ischemic disorders that can produce misleading information are discussed.

Activation of the coagulation cascade in untreated primary open-angle glaucoma

PURPOSE

The authors studied the coagulation cascade and fibrinolysis pathway in patients with untreated glaucoma (P = 0.00001 and P = 0.0003, respectively) and patients with normal pressure glaucoma ([NPG] P = 0.00001 and P = 0.03, respectively).

METHODS

Forty-two untreated patients with NPG, 25 untreated patients with primary open-angle glaucoma (POAG), and 32 age-matched normal controls were recruited. Patients taking anticoagulant therapy beta blockers or calcium channel blockers were excluded. Venous blood was assessed for markers of the coagulation and fibrinolysis pathways using enzyme-linked immunosorbent assay techniques.

RESULTS

Patients with POAG had elevated levels of prothrombin fragments 1 + 2 and D-dimer compared with both the NPG and controls (P = 0.00001 and P = 0.0003, respectively). Both glaucoma groups had more (P < 0.05) systemic vascular disease than the control group. The patients with POAG had higher (P < 0.05) systemic blood pressure (systolic and pulse pressure) than the control and NPG groups. Both glaucoma groups had greater levels of fibrinogen (which was of borderline statistical significance) than the control group.

CONCLUSION

Elevated levels of prothrombin fragments 1 + 2 and D-dimer indicate activation of the coagulation cascade and fibrinolysis pathway, respectively, leading to a hypercoagulable state in untreated POAG. These findings may contribute to the reported increased prevalence of retinal venous thrombosis in glaucoma and also to the pathogenesis of optic nerve damage in glaucoma.

Activated protein C resistance--low incidence in glaucomatous optic disc haemorrhage and central retinal vein occlusion

PURPOSE

Activated protein C (APC) resistance has recently been reported as conferring a sevenfold increase in the risk of venous thrombosis. It is linked to a genetic mutation in the factor V gene which occurs commonly (about 2% to 4% of the community have the mutation). Glaucoma patients with nerve fibre layer (NFL) haemorrhages on the optic disc and patients with central retinal vein occlusion (CRVO) were tested for APC resistance to determine if there was an association.

METHODS

Twenty-three patients with glaucomatous NFL haemorrhages and 23 patients with CRVO were tested. The CRVO cases included 11 with relatively young age of onset (mean 45.1 +/- 6.9 years) without conventional vascular risk factors. Eighty randomly selected Red Cross blood donor samples and 33 staff members were tested as controls. Clotting times with and without exogenous APC were recorded and an APC ratio determined. Cases with APC resistance were tested to confirm that they had the factor V Leiden gene.

RESULTS

No cases of APC resistance were identified in the glaucoma patients and only one of the younger CRVO patients tested positive, but four of 113 controls tested positive. The difference in prevalence between groups is not significant. The mean APC ratios for the three groups were very similar: NFL haemorrhages 5.46(+/- 1.62), CRVO 5.70(+/- 1.56), controls 5.34 ( +/- 1.19) p > 0.5.

CONCLUSION

There was not clear association detected between glaucomatous NFL haemorrhages or CRVO and APC resistance in this sample of patients. This negative finding is important due its known association with venous thrombosis elsewhere in the body.

Results of a filtering procedure in low tension glaucoma

Twenty-six eyes of twenty patients with established low tension glaucoma, who had either a 'double flap' Scheie filtering operation or a trabeculectomy, were followed over a period ranging from one to ten years, with a median of three years. These 26 eyes include two second eyes that served as a contralateral control eye until the visual field deteriorated. All 26 eyes showed progression of visual field defects preoperatively, while postoperatively only 2 eyes showed further progression. Of the 16 nonoperated contralateral eyes, 7 showed progression of visual field defects over the same follow-up period. Two of these 7 eyes had to be operated during the study-period. The difference in progression between the operated and the non-operated eyes was significant (P less than 0.01). The filtering procedure provided a reduction in IOP of 20% or more in 21 of 26 eyes. There was a significant difference in the mean intraocular pressure (IOP) between the operated and the non-operated contralateral eye of 6.8 mmHg (37%) at one year postoperatively. The diurnal variation decreased highly significantly from 4.3 to 2.1 mmHg (P less than 0.001). It is concluded that filtering surgery in low tension glaucoma may result not only in a significant lowering of IOP, but is also effective in slowing further deterioration of the visual fields.

Platelet aggregation and glaucoma

In this study platelet aggregation was determined in 79 patients with primary open angle glaucoma (POAG) and 81 patients suspected of having glaucoma (ocular hypertension). There is a positive association between high age and the presence of vascular diseases (p less than 0.01). An age dependent association between spontaneous platelet aggregation (SPA) and the presence of POAG was also observed (p less than 0.05). This indicates that the incidence of SPA in the elder group of patients with POAG is higher than in the elder glaucoma suspect group and in the group of younger patients. The association between vascular diseases and SPA and between vascular diseases and the presence of POAG were not significant at the 5% level. The incidence of SPA is not influenced by sex distribution, by the presence of diabetes, smoking or the use of timolol maleate topically.

Blood and plasma viscosity measurements in patients with glaucoma

Blood viscosity at 10 shear rates, plasma viscosity, packed cell volume, plasma fibrinogen, serum alpha 2-macroglobulin, and serum proteins were measured in 83 patients with low-tension glaucoma (LTG) and 23 patients with 'high-tension glaucoma' (HTG: at least one IOP reading above 40 mmHg) and compared with those in 50 controls. Blood and plasma viscosity values and packed cell volume were significantly higher in the LTG group than those in controls. The HTG and the LTG groups differed only in plasma viscosity, but smoking and drinking habits in the HTG patients were greatly different from those in LTG patients and controls, thus preventing interpretation of data in the HTG group. Within the LTG group viscosity values were highest in a subgroup designated earlier by us as focal ischaemic LTG, whereas another subgroup, senile sclerotic LTG, did not show significant differences compared with controls. These findings may indicate a factor in the pathogenesis of visual field defects and disc cupping in some patients with LTG.

Systemic factors in patients with low-tension glaucoma

Nineteen patients (38 eyes) with low-tension glaucoma were compared with 53 subjects (106 eyes) with ocular hypertension. Comparable for age and sex, the 2 groups were assessed with respect to haematological and biochemical criteria, physical activity, and medical history. Statistical analyses of the differences between the 2 groups highlighted the importance of diastolic ophthalmodynamometry levels, prediagnosis exercise habits, cardiovascular disease status, and possibly systolic blood pressure. Patients with low-tension glaucoma suffered a higher prevalence of multiple abnormalities of these systemic factors than did their ocular hypertensive counterparts. There were no significant differences between the 2 groups with respect to the many other factors examined.

Low tension glaucoma: a critical review and new material

Low tension glaucoma (LTG) is a condition consisting of typical gluacomatous disc and field changes, an open angle and pressures within the statisticaly normal range. The controversy surrounding low tension glaucoma pertains not only to the definition and characteristics of the entity itself, but to the fundamental questions it raises regarding the causal relationship between intraocular pressure and disc and field changes. This review of LTG is based on material from three major sources: Sjögren's review from 1857 to 1946; the author's review of the world literature from 1947 through 1979; and an analysis of 32 of the author's cases. 767 cases from clinic and private practice and 241 cases from defined populations are considered. Definitions, incidence, characteristics, differential diagnosis and management of LTG are discussed, as are its relationship to primary open angle glaucoma and its possible association with various other entities. Pathogenesis and possible mechanisms are also explored.

Indium-III: a new radionuclide label for studying human platelet kinetics

Indium-III. when complexed with 8-hydroxyquinoline (oxine), has been employed as a radioactive platelet label for thrombus imaging in animals and man. The short half-life (2.8 d) and high yield of gamma photons of 111In make it ideal for in vitro counting and external imaging. To evaluate its suitability for studies of platelet turnover in man, platelet kinetic studies were carried out on 10 healthy volunteers using 111In-and 51Cr-platelets concurrently. For 111In labelling, platelets were harvested by differential centrifugation from 43 ml of whole blood drawn into acid-citrate dextrose (ACD) solution. The platelets were washed and suspended in a mixture of ACD and isotonic saline and then incubated with 111In-oxine, rewashed, and suspended in plasma for reinfusion. 51Cr labelling was performed using standard methods. Mean labelling efficiency was 73% with 111In and 6.5% with 51Cr. In vitro studies demonstrated minimal release, elution, and reutilization of the 111In label. There was no significant difference in the aggregation response of 111In- and 51Cr-platelets to ADP and collagen. The in vivo recovery of 111In-platelets was approximately 50% greater than that of 51Cr-platelets whereas the platelet life spans were similar. These results indicate that 111In labelled platelets may be useful for thromobokinetic studies in man. The new method offers the advantages of reduced blood requirements, higher labelling efficiency, and the ability to perform external imaging of platelet distribution in vivo.

Circulating lipoprotein and blood glucose levels in association with low-tension and chronic simple glaucoma

Circulating lipoprotein and blood glucose levels were determined for 53 patients with low-tension glaucoma and 39 patients with chronic simple glaucoma. The incidence of hypercholesterolaemia was significantly higher in the low-tension group than in the chronic simple glaucoma group and control data obtained elsewhere. Preliminary follow-up results of the effects of treatment are also reported. The incidence of raised fasting blood glucose levels was not significantly increased in either group.