Platelet aggregation and glaucoma

Systemic factors associated with 10-year glaucoma progression in South Korean population: a single center study based on electronic medical records

Glaucoma is a multifactorial disease where various systemic features are involved in the progression of the disease. Based on initial systemic profiles in electronic medical records, this study aimed to develop a model predicting factors of long-term rapid retinal nerve fiber layer (RNFL) thinning over 5 years in 505 patients with primary open-angle glaucoma. Eyes with faster or slower RNFL thinning were stratified using a decision tree model, and systemic and ophthalmic data were incorporated into the models based on random forest and permutation methods, with the models interpreted by Shapley additive explanation plots (SHAP). According to the decision tree, a higher lymphocyte ratio (> 34.65%) was the most important systemic variable discriminating faster or slower RNFL thinning. Higher mean corpuscular hemoglobin (> 32.05 pg) and alkaline phosphatase (> 88.0 IU/L) concentrations were distinguishing factors in the eyes with lymphocyte ratios > 34.65% and < 34.65%, respectively. SHAP demonstrated larger baseline RNFL thickness, greater fluctuation of intraocular pressure (IOP), and higher maximum IOP as the strongest ophthalmic factors, while higher lymphocyte ratio and higher platelet count as the strongest systemic factors associated with faster RNFL thinning. Machine learning-based modeling identified several systemic factors as well as previously acknowledged ophthalmic risk factors associated with long-term rapid RNFL thinning.

Platelet-generated amyloid beta peptides in Alzheimer's disease and glaucoma

Amyloid beta (Aβ) peptides have been implicated in both Alzheimer's disease (AD) and glaucoma and have been shown to be the key etiological factor in these dangerous health complications. On the other hand, it is well known that Aβ peptide can be generated from its precursor protein and massively released from the blood to nearby tissue upon the activation of platelets due to their involvement in innate immunity and inflammation processes. Here we review evidence about the development of AD and glaucoma neuronal damage showing their dependence on platelet count and activation. The correlation between the effect on platelet count and the effectiveness of anti-AD and anti-glaucoma therapies suggest that platelets may be an important player in these diseases.

Association between Platelet Parameters and Glaucoma Severity in Primary Open-Angle Glaucoma

Purpose

To evaluate platelet parameters in primary open-angle glaucoma (POAG) patients and to explore the association between platelet parameters and POAG severity.

Methods

A total of 402 consecutive POAG patients and 408 healthy control subjects from the Department of Ophthalmology and Visual Science, Eye and ENT Hospital, Fudan University, were consecutively recruited between January 2016 and October 2018. Detailed ophthalmological and systematic examinations were performed. Blood samples for platelet parameters, including platelet count (PLT), platelet distribution width (PDW), plateletcrit (PCT), mean platelet volume (MPV), and platelet large cell ratio (P-LCR), were analyzed using an automated hematology analyzer in the department of clinical laboratory science of the hospital. The POAG subgroups were classified according to age (<50, ≥50), gender, and visual field mean deviation (MD): mild (MD ≤ 6 dB), moderate (6 dB < MD ≤ 12 dB), and severe (MD > 12 dB).

Results

In POAG patients, PLT counts (207.08 ± 54.70 ∗ 10⁹/L) were significantly lower (p=0.001) than those of the control group (220.46 ± 55.85 ∗ 10⁹/L). In the POAG group, PDW (13.76 ± 3.16 fL) and MPV (10.46 ± 1.32 fL) values were significantly higher (all p < 0.001) than those of the control group (PDW 11.82 ± 2.44 fL, MPV 10.13 ± 1.10 fL). PDW and MPV values were highest in the severe POAG group (PDW 14.49 ± 2.99 fL; MPV 10.74 ± 1.39 fL), followed by the moderate group (PDW 12.50 ± 3.14 fL; MPV 10.02 ± 1.08 fL) and then the mild group (PDW 11.82 ± 2.44 fL; MPV 9.92 ± 0.76 fL), with statistically significant differences observed between mild-severe POAG and moderate-severe POAG groups by LSD post hoc test. Multiple linear regression analyses showed a significant association between PDW and MD (β = 0.430, p < 0.001) and MPV and MD (β = 0.363, p=0.001). Logistic regression analyses revealed that PDW (OR = 1.297, 95% CI = 1.011-1.663) was associated with the severity of POAG.

Conclusions

PDW and MPV values were significantly elevated in POAG patients, and PDW was positively associated with disease severity, which suggested the possibility that platelet activation be involved in pathomechanisms of POAG.

Anti-platelet effects of anti-glaucomatous eye drops: an in vitro study on human platelets

PURPOSE

Altered platelet aggregability has been implicated in the pathogenesis of glaucoma. This study aims to investigate the anti-platelet potential of intraocular pressure lowering drops, with the possibility of establishing it as an additional mechanism of anti-glaucomatous action.

MATERIALS AND METHODS

The anti-aggregating effects of a series of anti-glaucomatous eye drops were determined on human platelets in the platelet aggregation model, using four known aggregating factors (platelet activating factor [PAF], adenosine diphosphate [ADP], thrombin receptor-activating peptide [TRAP], and arachidonic acid [AA]).

RESULTS

Almost all of the tested samples inhibited platelet aggregation induced by PAF, ADP, TRAP, and AA, except for Alphagan, which did not demonstrate inhibition of ADP- and TRAP-induced aggregation at a wide range of concentrations. Trusopt, Betoptic, and Azarga eye drops were the most potent inhibitors of all four aggregating factors, while Alphagan was the least potent (P<0.05).

CONCLUSION

This study shows that anti-glaucomatous eye drops possess anti-platelet effects, and this was shown for the first time by experimenting on human platelets.

Higher intraocular pressure is associated with leukoaraiosis among middle-aged and elderly Koreans without glaucoma or dementia

AIM

Leukoaraiosis and high intraocular pressure are strongly associated with cardiovascular disease, vascular angiopathy, and geriatric syndrome. Until now, little is known about the relationship between intraocular pressure and leukoaraiosis in its preclinical stage. The aim of this study was to evaluate the association between intraocular pressure and leukoaraiosis among middle-aged and elderly Koreans without glaucoma or dementia.

METHODS

We examined the relationship of intraocular pressure with leukoaraiosis at a preclinical stage in 753 Korean adults (474 men, 279 women; mean age 57.8 ± 6.6 years). A multiple logistic regression analysis was performed in order to determine whether intraocular pressure is an independent determinant for leukoaraiosis.

RESULTS

The overall prevalence of leukoaraiosis was 7.3%. Mean ocular pressure (±SD) was significantly higher in the leukoaraiosis group than the control group (14.3 ± 2.9 and 13.5 ± 2.9, respectively; P=0.028). In multiple logistic regression analysis, the odds ratio for leukoaraiosis was 1.18 (95% confidence interval: 1.06-1.31) for each 1 mm Hg increase in intraocular pressure.

CONCLUSION

Intraocular pressure was found to be independently and positively associated with leukoaraiosis. This finding indicates that higher intraocular pressure may be a useful additional measure in assessing the risk of leukoaraiosis in the clinical setting.

Glaucoma and systemic diseases

Glaucoma management may be extremely challenging, especially in elderly patients who have a variety of systemic diseases and take multiple medications. We obtained a comprehensive medical history in patients with primary open-angle glaucoma to determine which systemic diseases are most prevalent and which systemic medications are most commonly used. We have also reviewed the literature that addresses how these concomitant diseases and medical treatments influence the management of glaucoma. Knowledge of systemic diseases and potential drug interactions, especially between various systemic and glaucoma medications, is important for the safe management of glaucoma patients.

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.

Primary open-angle glaucoma patients have reduced levels of blood docosahexaenoic and eicosapentaenoic acids

The aetiology of primary open-angle glaucoma (POAG), which is the commonest cause of non-remediable blindness and visual impairment, is not well understood. Nevertheless, increased intraocular pressure, and vascular factors such as ocular blood flow deficits are thought to be risk factors. There is evidence of decreased optic nerve blood velocity and increased red blood cell aggregability in POAG. These factors are influenced by fatty acids. We have investigated if glaucoma patients have abnormal blood fatty acid composition. Patients with POAG (n=10) and their healthy siblings (n=8) were enrolled. Compared with their healthy siblings, the glaucoma patients had reduced eicosapentaenoic (EPA, P<0.01), and docosahexaenoic (DHA, P<0.05) fatty acids and total omega3 long-chain polyunsaturated fatty acids (LCPUFA) (P<0.05) in red cell choline phosphoglycerides (CPG); decreased EPA (P<0.05) in ethanolamine phosphoglycerides (EPG); lower EPA (P<0.05) and total omega3 LCPUFA (P<0.05) in serine phosphoglycerides (SPG). Similarly, they had reduced EPA, DHA and total omega3 LCPUFA in plasma CPG (P<0.005) and triglycerides (P<0.05). These findings may be significant, since EPA and DHA could modulate impaired systemic microcirculation and ocular blood flow and optic neuropathy, which are the main physiological changes associated with glaucoma.

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.

Modulative effects of cell adhesion peptide (Arg-Gly-Asp-Ser) on the aggregation of stimulated platelets from ophthalmic patients

Adhesion proteins are cofactors in the aggregation of human platelets, and can mediate the ADP-induced response of these cells. It was shown that the synthetic cell adhesion peptide, Arg-Gly-Asp-Ser inhibits the aggregation of platelets from normal donors and ophthalmic patients with diabetic retinopathy, glaucoma and retinal vein occlusion. This effect increases in the relative order of activity retinal vein occlusion greater than or equal to glaucoma greater than or equal to diabetic retinopathy greater than control. Deaggregation due to the peptide appeared to be diminished in the order control (normal) greater than diabetic retinopathy greater than glaucoma greater than retinal vein occlusion after its addition at the maximum of aggregation curve. It is concluded that there are differences in the ability of Arg-Gly-Asp-Ser peptide to block the fibronectin adhesion receptor on ADP stimulated platelets from different clinical groups.

Biostatistical evidence for two distinct chronic open angle glaucoma populations

Twenty-six eyes of 26 patients with low-tension glaucoma and 34 eyes of 34 patients with high-tension glaucoma were studied. Fifty-one measurements were available on each patient, including visual field indices, finger blood flow measurements, as well as haematological, coagulation, and biochemical and rheological variables. Multivariate analysis revealed two statistically distinct groups of patients, with low and high tension glaucoma cases equally distributed in both. The smaller group (15 patients) showed a suggestion of vasospastic finger blood flow measurements, and had a high positive correlation between the mean deviation (MD) index of field severity and the highest intraocular pressure (r = 0.715, p = 0.0008). The second, larger group (45 patients) showed disturbed coagulation and biochemical measurements, suggestive of vascular disease, and had no correlation between the MD index and the highest intraocular pressure.

Investigations into a vascular etiology for low-tension glaucoma

Increased intraocular pressure is accepted as a primary etiologic factor for the atrophy of the optic nerve head and visual field defects of high-tension glaucoma. Other factors must be present to explain these findings in low-tension glaucoma. One of the current theories is that low-tension glaucoma is the result of decreased optic nerve perfusion on the basis of vascular disease or other factors such as altered blood viscosity. This study compared the non-invasive vascular profiles, coagulation tests, and rheological profiles of 46 consecutive cases of low-tension glaucoma with 69 similarly unselected cases of high-tension glaucoma and 47 age-matched controls. Despite the multifactorial approach and the use of previously validated objective tests, no significant group differences were detected with any of the above investigations. If vascular disease is important in the etiology of low-tension glaucoma, then it must be localized or vasospastic since this study does not support the concept of a generalized vascular etiology, either of an atheromatous or hyperviscous nature, for the genesis of low-tension glaucoma.

Fibronectin detection in drainage outflow system of human eyes in ageing and progression of open-angle glaucoma

The content of the fibronectin, an extracellular glycoprotein in the drainage outflow system of human eyes was determined by the indirect immunoperoxidase staining technique. The degree of fibronectin accumulation in ocular tissues was evaluated by quantitative morphometric analysis. It was shown that the fibronectin level was elevated in the ocular drainage outflow system of humans in ageing and was rapidly increased at different stages of primary open-angle glaucoma development. Increased deposit of fibronectin in trabecular tissues, mainly, in the inner wall of Schlemm's canal and juxtacanalicular, or cribriform part of trabecular meshwork, was demonstrated along with ageing and glaucoma disease progression. A hypothesis underlying the glaucomatous process as an adhesive impairment was proposed.