The relationship between intraocular pressure and random blood glucose levels with open angle glaucoma

INTRODUCTION

It is characterized by optic neuropathy, including glaucoma, chronic axonal damage and retinal nerve cell (RGC) damage.¹ It affects the eye and is associated with increased intraocular pressure (IOP), which is the only risk factor for glaucoma treatment.² If left untreated, patients may develop visual impairment and even blindness. It is the number one cause of blindness loss and the second cause of blindness worldwide.^3,4 Glaucoma involves cell loss of retinal ganglion cells (RGCs) and is characteristic of neural retinal organization in the optic nerve head (ONH), along with visual disturbances (VF).^5,6 This eye disease is the leading cause of blindness worldwide and has created a significant public health problem. Intraocular pressure (IOP) is determined by the balance between aqueous humour production and outflow, and IOP homeostasis is primarily maintained by changes in aqueous humour outflow resistance.⁷ Epidemiological studies have suggested that IOP is affected by several factors, including non-modifiable risk factors, such as age, race, refraction, and central corneal thickness (CCT), and modifiable risk factors, such as blood pressure (BP), physical activity, and obesity.⁸ High intraocular pressure can lead to glaucomatous optic nerve damage and subsequent blindness.⁹ Examination of the optic disc is indicative of glaucoma.¹⁰ The optic disc is a small blind area of the retina formed by RGC axons that curve from the disc and exit the eye from the cribriform plate.¹¹ In primary open-hole glaucoma, the trabecular meshwork underwent morphological changes over time and caused significant fluid obstruction despite remaining anatomically open. Primary open-angle glaucoma (POAG) accounts for 74% of all glaucoma cases.¹⁰ As a result of the increase in the height of the nerve, it is sent to the optic disc and eventually causes atrophy and nerve damage.¹¹ The main risk factors for POAG are high intraocular pressure, usually greater than 21 mmHg, strong genetic predisposition, and advanced age, mostly elderly and elderly people. It is chronic, usually bilateral, failure and poor onset.⁶ POAG is generally asymmetrical, with a visual difference of more than 0.2, more severe in one eye than the other, and without side effects.¹² It is asymptomatic until blindness occurs. In POAG, the iris-corneal (filtering) angle is usually open or wide with no narrow bias and has a normal chamber depth Its main feature is glaucomatous optic neuropathy with thinning of the temporal disc margin. Because the disease progresses slowly, POAG is asymptomatic until the underlying cause is not identified. It does not cause headaches, eye pain or vision loss. This increases the challenges of diagnosing and treating open-angle glaucoma.¹³ Diabetes is a chronic disease caused by the body's inability to produce insulin or absorb sugar.¹⁴ In people with diabetes, the pancreas does not produce enough insulin or the cells do not respond properly to insulin. Hyperglycaemia, also known as high blood sugar or high blood sugar, is the result of uncontrolled blood sugar and over time can cause serious damage to many organs in the body, especially veins and arteries.¹⁵ Diabetes mellitus (DM) is an important public health problem with increasing morbidity. An estimated 451 million people (18-99 years old) worldwide had diabetes in 2017, this number could rise to 693 million by 2045.¹⁴ According to the World Health Organization, the number of people with diabetes increased from 108 million in 1980 to 422 million in 2014.^16,17 Diabetes was estimated at 476 million people worldwide in 2017 and is expected to increase to 571 million by 2025.¹⁸ According to the International Diabetes Federation, the incidence of diabetes will be 9.9% and the number of people with diabetes will reach 9.9%. In 2030, the number of people with diabetes will reach 552 million.¹⁸ The objective of this study was to investigate the correlation between intraocular pressure and random blood glucose levels in patients with primary open-angle glaucoma.

METHODS

This was an observational study conducted for about 10 month (December 2016 to September 2017) at the department of optometry GSVM Medical College, Kanpur, UP, India. All participants in this study obtained informed consent. This study was approved by the ethics committee of the faculty of health technologies and the department of optometry GSVM Medical College, Kanpur Uttar Pradesh state, India. Patients diagnosed with open-angle glaucoma were recruited to participate in this study.

Inclusion criteria

This study included patients of all genders and 20 years of age or older.

Exclusion criteria

Section excluded patients under 20 years of age with a family history of glaucoma, myopia, or pseudo exfoliation syndrome, section with a history of previous trauma/surgery and long-term steroid use.

74 patients who met the inclusion criteria were included in the study. Written informed consent was taken from the patients. Detailed history of patients regarding name, age, sex, occupation, address, drug history, presenting symptom, duration, associated conditions and past history was recorded. History of diabetes such as symptoms, duration, and type of treatment was enquired. Overall control was assessed by lab parameters.

Intraocular pressure was measured using the Perkins applanation tonometer while their blood glucose level was measured using the Accu-Chek glucometer. Before each measurement the tonometer was set to 10 mmHg and pressure was recorded. Gonioscopy and perimetry was planned if IOP>21 mmHg or optic disc changes suggestive of glaucoma were present. Dilated fundus examination was done by direct ophthalmoscopy and with +90D lens.

Statistical methods

The data obtained from the study was uploaded into the Statistical Package for Social Sciences (SPSS) version 23 software. The Pearson product moment correlation coefficient was used to test the correlation of intraocular pressure and blood glucose levels at 0.05 level of significance and 95% confidence interval.

RESULTS

A total of 74 patients diagnosed with open-angle glaucoma were included in this study.

Table 1 shows the age and gender distribution of the subjects. Of these, 28 were men and 46 were women. The prevalence of men aged 39 to 58 years (mean age) was 13.51%. Among people aged 79-98 years, the incidence was lowest in men and women, both at 2.7%. For people aged 20-38 years (adults), the rate for men and women was 10.81%.

Table 2 shows the frequency and mean IOP values in different variables. Tonometry was performed on 70 eyes of 37 patients, one (1) eye ranging from 26 to 30 mmHg; 3 eyes with an average of 9.67 mmHg in the 5-10 mmHg range. In 29 eyes, IOP was in the range of 16-20 mmHg, with a mean of 17.76 mmHg.

Table 3 shows the frequency and average of patients’ blood glucose levels. Of the 21 subjects whose RBG was measured, 3 had the lowest range of 1-100 mg/dl, and the mean random BGL was 74.33 mg/dl; 2 subjects ranged from 401 to 500 mg/dl, mean random BGL 431.50 mg/dl; The blood glucose level of 14 people was between 100-200 mg/dl and the average fasting BGL was 132.57 mg/dl.

n =Number, Max =Maximum, Min =Minimum, SD = Standard deviation.

Table 4 shows IOP and descriptive IOP statistics. The lowest IOP value was 9 mmHg; the maximum value was 26 mmHg, the range was 17 mmHg, the mean value was 16.57 mmHg, and the standard deviation was 3.97 mmHg.

Blood tests for anemia were performed on 21 patients. Minimum 42 mg/dl, maximum 458 mg/dl maximum 416 mm/dl. The mean was 168.43 mg/dl and the standard deviation was 108.4.

Table 5 shows the SPSS data analysis using Pearson’s product-moment correlation coefficient (significance 0.05, 95% confidence) to assess the relationship between RBG and IOP. It revealed a p value of 0.745 and a Pearson correlation of -0.076. There was no correlation between IOP level and RBG (p>0.05) among the subjects.

DISCUSSION

The results showed that there was no relationship between blood glucose and intraocular pressure (p>0.05). Mean IOP values of various age groups show that IOP gradually increases with age. High IOP is the main determinant of primary open-angle glaucoma. A study on diabetes and hypertension showed that the incidence of glaucoma increases with age.²⁰ However, the same study also found no association between age and IOP. The difference in IOP between male and female subjects in our study showed that female subjects with a mean IOP of 17.51 mmHg had higher IOP than men with a mean IOP of 14.88 mmHg. Although Khalaj et al showed an insignificant difference in mean IOP between genders both with diabetic and non-diabetic patients, Khachatryan, et al asserted that the male gender was significantly associated with the risk of primary open-angle glaucoma among African-Americans 35 years and older.^20,21 A study to predict fasting glucose provided evidence for the role of genetic determinants of fasting glucose in the development of high IOP.²² A study to predict fasting glucose provided evidence for the role of genetic determinants of fasting glucose in the development of high IOP.²² Intraocular pressure should be monitored in patients without diabetes mellitus and with high blood sugar. High IOP is an important indicator of primary open-hole glaucoma and increased eye pressure. Cui et al in a study on fasting blood glucose levels and risk in open-angle glaucoma patients, patients with the highest fasting blood glucose (≥160 mg/dl) were more likely to have the lowest (<80 mg/dl) blood glucose levels).²³ The hazard ratio (HR 2.189) and correlation (p<0.001) for open-angle glaucoma were higher in patients with and without type 2 diabetes compared with those with type 2 diabetes. This is in contrast to our study, perhaps because our subjects did not register high blood sugar levels. In addition, body mass index (BMI), presence or absence of high blood pressure, smoking, alcohol consumption, exercise, etc. We excluded other factors such as from statistics, a negative Pearson correlation value (-0.076) emerges when testing hypothesis, which shows the relationship between IOP and blood glucose levels, and vice versa. However, a negative value close to zero indicates that the relationship is not significant. Intraocular pressure has been shown to be an independent risk factor for POAG and is currently the only modifiable risk factor. Many other risk factors are involved in the pathogenesis of glaucoma because IOP is not the only risk factor that puts a patient at risk of developing POAG. Other factors that have been shown to be associated with the development of POAG include cup-to-disc ratio, visual acuity, intervertebral disc haemorrhage, myopia, central corneal thickness (CCT), ocular perfusion pressure, intracranial pressure (ICP), and translaminar cribriform, pressure gradient, diabetic hypertension, blood flow to the eye, vascular status, genetic factors and age.^24-27 Gender and race are risk factors for POAG, but how these affect an individual’s risk of POAG has not been determined. Several studies have shown that glaucoma development has a stronger vascular tone in diabetic glaucoma patients compared to non-diabetic POAG patients.^23,26 Specifically, diabetes affects structural and hemodynamic factors related to blood flow. In POAG patients with diabetes mellitus, changes in retinal blood flow have been associated with changes in ONH (e.g., volume, cup-to-disc area ratio, margin area, pit area, cup shape, linear c/d ratio) four years.²⁸ Additionally, changes in retinal blood flow in patients after four years were associated with changes in macular thickness. This suggests that POAG patients with diabetes may have a strong vascular contribution to their glaucomatous structural damage.

It is important to note that vascular changes are also associated with RNFL and macular deterioration in POAG patients with DM.²⁹ Amato et al used the DBA/2J mouse (D2) model of glaucoma to analyze the effect of early diabetes on glaucomatous RGC dysfunction before IOP rises, and found that intraocular pressure (IOP) did not affect duration or blood pressure.³⁰ In contrast, RGC activity in the D2 group gradually decreased independently of increased intraocular pressure (IOP) and peripheral retinal dysfunction. The result of our study is comparable with that of the study conducted by Neeetans et al in 1997.³¹ The positive relationship between diabetes and increased intraocular pressure has been well documented in several other studies.^31-34

A population-based study in the Netherlands found that newly diagnosed diabetes and hypertension were associated with weight gain.³⁵ Jian et al in 2000, it was reported that IOP increased in patients with diabetic retinopathy and hypertension.³⁶ Pimentel et al in 2015, there was a significant relationship between diabetes and eye pressure. This study also found that postprandial IOP was higher than random IOP.³⁷ Traisman and colleagues found that patients with blood glucose levels above × 200 mg/dl had higher IOP readings.³⁸

CONCLUSION

This suggests that POAG patients with diabetes may have a strong vascular contribution to their glaucomatous structural damage. It is important to note that vascular changes are also associated with RNFL and macular deterioration in POAG patients with DM.²⁹ Amato et al used the DBA/2J mouse (D2) model of glaucoma to analyze the effect of early diabetes on glaucomatous RGC dysfunction before IOP rises and found that intraocular pressure (IOP) did not affect the duration or blood pressure.³⁰ In contrast, RGC activity in the D2 group gradually decreased independently of increased intraocular pressure (IOP) and peripheral retinal dysfunction.

ACKNOWLEDGEMENTS

We would like to thank the heads of the institution, the teachers, the staff and more so the students for having been very cooperative in the collection of the data. We thank our entire department faculty for being encouraging and supportive throughout this study.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

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