Intraocular pressure (IOP) is the hydrostatic pressure maintained within the eye by the dynamic equilibrium between the continuous secretion and drainage of the aqueous humor. Normal range of IOP is between 10-21 mm Hg.¹The increased IOP is associated with glaucomatous optic nerve head damage.² Glaucoma is one of the leading causes of irreversible blindness in the world.³In  India about 11.9 million are diagnosed with glaucoma.⁴Intraocular pressure is the only modifiable risk factor which can halt progression of glaucoma. Consequently, the prompt identification of elevated intraocular pressure is necessary.⁵ Various etiological factors directly influence the fluctuation of intraocular pressure (IOP). Non modifiable risk factors include age,sex,race,refraction⁶ and modifiable risk factors include blood pressure and physical activity.^7,8Hypertension functions as a principal independent risk factor in the etiology and pathogenesis of both systemic cardiovascular diseases and cerebrovascular incidents, thereby significantly increasing morbidity and all-cause mortality.⁹Hypertension affects one billion people globally.¹⁰As age increases , blood pressure also increases in most populations, and medical treatment achieves good control of blood pressure.¹¹ IOP increases proportionately with increase in blood pressure.¹² The increased blood pressure increases the episcleral venous pressure and decreases the aqueous drainage, thus leading to raised IOP. Increased BP also contributes to increased ciliary blood flow and more aqueous humor secretion.¹³

Aim / Objectives / Hypothesis :

To investigate the correlation between Intraocular Pressure and Blood Pressure in patients attending  Ophthalmology OPD at GVPIHC & MT.

A Hospital based, prospective, cross sectional study was done in the Department of Ophthalmology, GVPIHC & MT, Visakhapatnam for a period of 3 months.

The Institutional Ethics Committee approval was taken. Informed and written consent was obtained from all patients after duly explaining the purpose of the study and procedure to be followed. 300 patients were included in the study after applying appropriate inclusion and exclusion criteria.

Inclusion criteria :

Patients above the age of 18 years including those with newly diagnosed hypertension not using any antihypertensive medication.

Exclusion criteria :

Patients with any systemic co morbidity. Patients using any systemic or ocular medication. Patients with history of ocular trauma.

Patients with history of glaucoma. Patients with prior ocular surgery.

Patients with any corneal degenerations, dystrophies, opacities which may alter intraocular pressure measurement.

Patients not willing to take part in the study.

The patient’s demographic data was noted.

Uncorrected visual acuity and best corrected visual acuity was assessed in all patients with autorefractometer (Potec PRK 5000 ) and subjective verification .

Anterior Segment examination was done under slit lamp biomicroscopy.

An automatic digital blood pressure monitor was used to measure systolic and diastolic blood pressures. After  5 minutes of rest, BP was recorded in the right arm with the patient comfortably seated and arm supported, the BP cuff at the level of the heart. The values were measured thrice 2 min apart and the mean of them was considered.

Depending upon the values, the patients were classified into the following groups based on the Indian Guidelines on Hypertension IV(2019)

Normal: <130 & <85

High normal: 130–139 or 85–89

HTN ≥140 or ≥90

HTN Grade 1: 140–159 or 90–99

HTN Grade 2: 160–179 or 100–109

HTN Grade 3: ≥180 or ≥110

The intraocular pressure was measured with the patient seated using slit lamp mounted Goldmann Applanation tonometer. The patients eyes were anesthetized topically with 0.5% proparacaine hydrochloride drops. The tip of a moistened fluorescein strip was touched to the lower fornix of the eye. Prism of the applanation tonometer was set into position. The adjusting knob was set at 1g.The illumination system makes an angle of 60 degrees with the viewing microscope and was positioned temporal to the eye to be measured. The slit beam width is maximum. Cobalt blue filter was used. The magnification was set at 10x.The patient was advised to fixate at a distance and the biprism was advanced until it touches the apex of the cornea. Green mires were observed against a blue background. The tension knob was adjusted until the ocular pulsations were noted and the inner edges of the two semicircles just touch. The IOP was determined by multiplying the dial reading with 10.The procedure was then repeated in the other eye. All the readings were done between 9-11 am to avoid any diurnal variation.

Fundus examination was done by indirect ophthalmoscopy.

The results were statistically analyzed using SPSS software . Descriptive statistics were used to analyse variables. Tests of significance were used with p value <0.05 being considered significant.

300 subjects were included in the study. 162 were males and 138 were females. The age of the subjects ranged from 21 to 80.

Table 1. Age and gender distribution

Table 2. Variation of intraocular pressure with age

The mean IOP in males was 14.772 +/- 3.032 . The mean IOP in females was 15.246 +/- 2.558. The highest intraocular pressure (IOP) was observed in the 41 to 60 age group for males and in the 61 to 80 age group for females. However, the analysis using the ANOVA test revealed no statistically significant difference in the mean IOP across the three age groups for both males and females.

Table 3. Correlation between age and systolic blood pressure in males.

Table 4. Correlation between age and systolic blood pressure in females.

The mean SBP increased with increasing age  in both males and females. The difference  in SBP between the age groups was found to be statistically significant in both genders by ANOVA test.

Table 5. Correlation between age and diastolic blood pressure in males.

Table 6. Correlation between age and diastolic blood pressure in females.

The diastolic blood pressure was found to be highest in the 41 to 60 age group in both males and females. A significant statistical variation in diastolic blood pressure (DBP) across different age groups was noted in both genders.

Table 7. Classification of blood pressure among the subjects

Table 8 . Mean IOP across different ranges of blood pressure

A correlation analysis was done between systolic blood pressure and IOP in different age groups, and also between  diastolic blood pressure and IOP in different age groups. Pearson correlation coefficient was calculated. A positive correlation was found across all age groups between SBP,DBP and IOP.

Table 9. Correlation between Systolic Blood pressure and Intraocular Pressure

Table 10. Correlation between Diastolic Blood Pressure and Intraocular Pressure

Glaucoma, also known as glaucomatous optic neuropathy, is marked by a slow, ongoing loss of retinal ganglion cells and their nerve fibers. Elevated intraocular pressure (IOP) is a primary risk factor for this condition¹⁴ and it's widely considered the most significant modifiable factor associated with the development of glaucomatous optic neuropathy.¹⁵

The factors influencing intraocular pressure and its measurement are critically important for understanding the pathogenesis of the disease and for reducing the burden of blindness. Given that IOP correlates with various physiological parameters, these factors must be considered when investigating its determinants. This study briefly investigated the relationships among age, blood pressure, gender, and intraocular pressure (IOP).

In our study, there are 138 females and 162 males. The mean IOP increased with increasing age in both the genders but was not statistically significant. Elderly age is an important risk factor for the incidence of glaucoma, especially open angle glaucoma. It is also found to be contributing to progression of ocular hypertension and glaucoma.^16,17Sclerotic Changes in the trabecular meshwork with age lead to reduction of trabecular outflow, subsequently raising the IOP.¹⁸ Progressive decrease in cerebral and ocular perfusion is associated with ageing.¹⁹

Mean IOP increased with increasing grade of hypertension. IOP increased with increasing systolic blood pressure. IOP also increased with increasing diastolic blood pressure. Both SBP and DBP were positively correlated with IOP. Several studies showed a change in IOP corresponded to a change in BP.^20,21,22

The Beaver Dam Eye Study concluded that systemic BP is positively correlated with IOP, and changes in BP over time are associated with corresponding changes in IOP. Both SBP and DBP were significantly correlated with IOP at both baseline and follow-up. ⁸

Nangia V et al found a positive correlation between systemic blood pressure and intraocular pressure (IOP). ²³

Foster PJ et al.  reported a direct correlation between intraocular pressure (IOP) and systolic

 blood pressure.²⁴

In patients with high blood pressure, intraocular pressure (IOP) may rise due to an increase in retinal blood volume, which occurs when elevated pressure in the central retinal artery raises the pressure in the nearby central retinal vein. Increased resistance in episcleral and ciliary veins can reduce aqueous outflow and raise blood volume in the ciliary body. Higher ciliary artery pressure may increase aqueous production, while elevated episcleral venous pressure can block drainage at the chamber angle.²⁵

This study found that intraocular pressure (IOP) increases with age in both men and women.

This study also revealed that IOP is directly linked to both systolic and diastolic blood pressure.

Elevated intraocular pressure is one of the most important risk factors for development and progression of glaucoma. It is currently the only modifiable risk factor which can halt disease progression and prevent irreversible blindness due to glaucoma. Increase in systolic blood pressure and diastolic blood pressure independently is associated with rise in intraocular pressure.

Based on our observations and supporting literature, hypertension is found to be a significant risk factor for elevated IOP. Regular monitoring of IOP in hypertensive and patients with advancing age can help in early detection of glaucoma. Periodic screening will help reduce the burden of glaucoma in the population.

Conflict of interest: None

Funding: Nil.

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