FP924 : Relationship of Systemic Hypertension, Ocular Perfusion Pressure and Glaucoma in North India.

Dr. Tripti Choudhary, C16809, Dr. Swarnali Sen

Abstract

Purpose: To study the relationship between systemic hypertension, ocular perfusion pressure and glaucoma by:-

Comparing the prevalence of POAG in hypertensive and control group in a hospital.

Studying the association between mean ocular perfusion pressure(MOPP) and glaucoma status (as evident from Mean Deviation, average RNFL thickness) in both the groups.

Studying and comparing the association between MAP and IOP in hypertensive and control group.

Methods: The participants were divided into two groups-

1. Hypertensive group- 100 patients(200eyes)
2. Normotensive group-100 patients(200eyes)

Detailed ocular, systemic and family history was taken. Single measurement of BP was taken. Complete ocular examination including visual acuity, anterior and posterior segment examination and Goldmann Applanation tonometry was done.

Mean arterial pressure (MAP) was calculated as DBP + 1/3 (SBP–DBP). MOPP was calculated using a standardized formula (MOPP = 2/3 × MAP–IOP). OCT and visual field analysis was also done in patients with high IOP (>21 mm of Hg) or C: D ratio ≥ 0.5 or asymmetry of > 0.2. These patients were further evaluated with gonioscopy, optic disc photography. Statistical tests were applied as follows-

1. Quantitative variables were compared using Unpaired t-test/Mann-Whitney Test (when the data sets were not normally distributed) between the two groups and ANOVA/Kruskal Wallis test(for non-parametric data) between more than two groups.
2. Qualitative variables were correlated using Chi-Square test /Fisher’s exact test.
3. Pearson correlation coefficient/Spearman correlation coefficient was used to assess the association of between quantitative variables.
4. Relative risk was calculated of history of treatment for presence of glaucoma and Odds ratio with 95% CI was calculated of MOPP with Glaucoma presence as dependent variable.

A p value of <0.05 was considered statistically significant.

The data was entered in MS EXCEL spreadsheet and analysis was done using Statistical Package for Social Sciences (SPSS) version 21.0.

Results: The prevalence of primary open angle glaucoma in patients with systemic hypertension is higher (36.5%) than in normal population(28%).

Mean Ocular Perfusion Pressure in hypertension patients was found to be higher (47.54mm Hg) than in normal individuals (42.55mm Hg). Mean arterial pressure of the hypertension group was 99.74mm of Hg and that of normotensive group was 89.78mm of Hg. The mean IOP in the hypertension group was 18.84mm of Hg and 17.33mm of Hg in the normotensive group. More severe glaucoma was associated with a lower mean ocular perfusion pressure in both the groups and was also associated with lower mean arterial pressure. Patients on antihypertensive medication were at a higher risk of developing glaucoma Relative risk(RR)=1.388,95%CI=1.0468-1.8403, P=0.023 However the relationship of antihypertensive medication use with severity of glaucoma was not found to be statistically significant.

Conclusion: The prevalence of primary open angle glaucoma in patients with systemic hypertension is higher than in normal population. Mean ocular perfusion pressure in hypertension patients was found to be higher than normal individuals. More severe glaucoma was associated with a lower mean ocular perfusion pressure in both the groups and was also associated with lower mean arterial pressure. Patients on antihypertensive medication were at a higher risk of developing glaucoma. Therefore it is important to screen systemic hypertension patients for glaucoma.

Key Words: Glaucoma, Hypertension, Perfusion Pressure, Intra Ocular Pressure

INTRODUCTION

Glaucoma is the second leading cause of blindness worldwide. Primary open angle glaucoma (POAG), the most common form of glaucoma, accounts for 60-70% of all glaucomas and 90-95% of primary glaucomas.¹Risk factors related to glaucoma include intraocular pressure (IOP), age, familyhistory, clinical appearance of the optic nerve, race, and potential vascular disease.^2-5Although the mechanism of retinal ganglion cell death in glaucoma is not fully understood, elevated IOP is considered the most important risk factor.^{6, 7}

Several large randomized clinical trials showed a relationship between IOP and glaucoma development and progression.^6–10Besides the mechanical effect of raised IOP on the optic nerve head (ONH), several vascular factors have also been identified as risk factors.^{11, 12} The process of autoregulation in a vascular bed maintains constant or nearly constant blood flow through a wide range of perfusion pressures. However, if autoregulation is impaired, elevated IOP may reduce optic nerve perfusion. In systemic hypertension, chronically elevated BP may result in arteriosclerosis, changes in the size of the precapillary arterioles, and capillary dropout leading to increased resistance to blood flow and thus, reduced perfusion.¹³

To our knowledge, no studies have examined the relationship of systemic hypertension with IOP, perfusion pressure, RNFL loss in primary open angle glaucoma in North India.

The purpose of our study is to evaluate the relationship between systemic hypertension, perfusion pressure and glaucoma in North Indian patients.

METHODS

This was prospective, observational, comparative study done during December 2015 to November 2016. It comprised 200 subjects divided in two groups. Hundred subjects were enrolled in each group, with and without hypertension.

Inclusion criteria for hypertensive group

• Patient age group 35 years and above
• Essential hypertension, either self-reported hypertension or newly diagnosed cases (defined as ≥140 mm Hg systolic BP [SBP] and/or ≥90 mm Hg diastolic BP [DBP])

 

Inclusion criteria for control group

• Patient age group 35 years and above
• Patients not having any history of hypertension and SBP <140mm Hg and /or DBP<90mm Hg

Exclusion criteria for hypertensive group

• Participants with hypertension due to secondary causes (endocrine or kidney disease/steroid induced) were excluded.
• Angle Closure glaucoma
• Secondary glaucoma

Exclusion criteria for control group

• Angle Closure glaucoma
• Secondary glaucoma

Detailed ocular, systemic and family history was taken. Single measurement of BP was taken. Complete ocular examination including visual acuity, anterior and posterior segment examination and Goldmann’sApplanation tonometry was done.

Mean arterial pressure (MAP) was calculated as DBP + 1/3 (SBP–DBP). MOPP was calculated using a standardized formula (MOPP = 2/3 × MAP–IOP). OCT and visual field analysis was also done in patients with high IOP (>21 mm of Hg) or C: D ratio ≥ 0.5 or asymmetry of > 0.2. These patients were further evaluated with gonioscopy, optic disc photography.

RESULTS

The mean age of the study group was 56.99±12.22 years and of the control group was 51.97±12.2 years. Maximum number of patients were found in the age group of 41-50 years and least number of patients in >80 years age group. There was a significant association between increasing age and presence of hypertension (P=0.001).

In our study the number of males and females was equal. Glaucoma was present in 33.5% of the males of which 56% had hypertension and 31% of the females of which 44% had hypertension. There was no relationship of gender with glaucoma.

Glaucoma was present in 36.5% of the patients with hypertension belonging to the study group and 28% in the control group.

H/O TREATMENT	GLAUCOMA	Total	P value
PRESENT	ABSENT
	PRESENT	64 (38.55%)	102 (61.45%)	166 (100.00%)	0.023
ABSENT	65 (27.78%)	169 (72.22%)	234 (100.00%)
Total	129 (32.25%)	271 (67.75%)	400 (100.00%)

Chart 1: Prevalence of Glaucoma in Hypertensive and Control group.

Table 1: Correlation between Glaucoma and Use of Antihypertensive Medication

There was a statistically significant association between antihypertensive use and glaucoma. Relative Risk (RR)=1.388,95%CI=1.0468-1.8403,P=0.023.However the relationship of antihypertensive medication use with severity of glaucoma was not found to be statistically significant.

On comparing the glaucoma status (as evidenced by mean deviation on visual fields) and MOPP a moderate negative correlation was found between these two variables which was statistically significant in the control group ie, as the MOPP decreased, the mean deviation  increased.The patients with severe glaucoma had MOPP 36.78 compared to MOPP of 43.78 in non-glaucoma patients. There was no such correlation between MOPP and glaucoma status in the hypertensive group.

		Sample size	Spearman’s coefficient of rank correlation (rho)	P value
Total	Mean deviation and MOPP	400	0.106	0.034
	MAP and IOP	400	0.238	<.0001
Hypertensive	Mean deviation and MOPP	200	0.004	0.9558
	MAP and IOP	200	.022	.752
Normotensive	Mean deviation and MOPP	200	-0.321	<.0001
	MAP and IOP	200	0.255	0.0003

Table 2:  Correlation of MOPP, MAP and IOP in both groups

 

Variable	Odds ratio	95% CI	P value
MOPP	0.9639	0.9338 to 0.9949	0.0226

Table 3: Odds Ratio

The chances of Glaucoma significantly decrease by 3.61% with the increase in MOPP by 1 unit.

Chart 2: Correlation between MOPP and Glaucoma

Chart 3: Correlation between MAP and IOP in both the Groups

DISCUSSION

In our study the prevalence of glaucoma in the hypertensive group was 36.5% and in the study group was 28%.It is comparable to a study done by Deb et al. in South India, where the prevalence was noted to be 20.4% in hypertensives.¹³

The prevalence of glaucoma in India has been reported to range from 0.4% to 3.75% in various surveys done across the country.^14-19

 

Our study, being a hospital based study, showed much higher value of prevalence of glaucoma compared with the population based surveys. These differences may be related to the study population and design.

In our study, the percentage of males and females was equal. There was no significant difference between the prevalence of POAG between men and women. This is similar to the Baltimore Eye Survey²⁰, Beaver Dam Study⁴ and the Blue Mountains eye study.⁵

In our study, the mean ocular perfusion pressure in the hypertensive group was 47.54mm of Hg and in the normotensive group was 42.55mm of Hg. We found a 3.61% reduction in risk of having POAG (95% CI=0.9338 to 0.9949, P=0.0226) with increase in MOPP by 1 unit. In other words, the lower the MOPP the greater the risk of developing glaucoma. In a case control study by Gherghelet al²¹, lower ocular perfusion pressure was associated with haemodynamic alterations in progressive glaucoma patients. Deb et al, found a 31% and 12% reduction in the risk of having POAG and suspicious glaucoma respectively with every 1mm Hg increase of MOPP.¹³

Low diastolic PP has been consistently associated with increased glaucoma prevalence in population-based studies. In the Baltimore Eye Survey ²², the Barbados Eye Study²³and the Rotterdam Study²⁴ low diastolic PP was a risk factor for glaucoma prevalence. Showing similar results, the Egna-Neumarkt Study ¹¹ and the Proyecto VER²⁵ reported that glaucoma prevalence decreases progressively with increased diastolic PP.

In the present study, we found that the mean ocular perfusion pressure in glaucoma patients classified as severe was lower compared to the mean ocular perfusion pressure in non-glaucoma patients, in both the groups.

In our study, the mean IOP in the hypertensive group was significantly higher than those without hypertension. The mean IOP of patients with glaucoma was noted to be 19.55±5.12 as compared to 17.38±4.29 in the normal patients.

The mean arterial pressure in the study group was 99.74mm of Hg and in the control group was 89.78mm of Hg. A positive correlation was observed between the mean arterial pressure and IOP in the normotensive group, i.e with increase in mean arterial pressure there was an increase in IOP. Similar conclusions were drawn by Deb and colleagues.¹³ This result could not be reproduced in the hypertensive group.

In conclusion, the prevalence of POAG in patients with systemic hypertension is higher than in normal population. MOPP in hypertension patients was found to be higher than normal individuals. More severe glaucoma was associated with a lower mean ocular perfusion pressure in both the groups and was also associated with lower mean arterial pressure. Patients on antihypertensive medication were at a higher risk of developing glaucoma. Therefore it is important to screen systemic hypertension patients for glaucoma.

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