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ORIGINAL ARTICLE
Year : 2022  |  Volume : 25  |  Issue : 4  |  Page : 395-400

Posture-induced intraocular pressure changes among patients with primary open angle glaucoma in a Nigerian Tertiary Hospital: Any implication for management


1 Department of Ophthalmology, Alex Ekwueme Federal University Teaching Hospital, Abakaliki, Ebonyi, Nigeria
2 Department of Ophthalmology, University of Nigeria Teaching Hospital, Ituku-Ozalla, Enugu, Nigeria

Date of Submission30-Oct-2020
Date of Decision25-Sep-2021
Date of Acceptance22-Feb-2022
Date of Web Publication19-Apr-2022

Correspondence Address:
Dr. O C Arinze
Department of Ophthalmology, Alex Ekwueme Federal University Teaching Hospital Abakaliki, Ebonyi
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_642_20

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   Abstract 


Background and Aim: To determine the effect of postural changes on intraocular pressure (IOP) among newly diagnosed patients with primary open-angle glaucoma (POAG). Patients and Methods: This was a cross-sectional observational study of 55 consecutive newly diagnosed patients with POAG attending Glaucoma clinics at a Federal Teaching Hospital in Abakaliki, Ebonyi state, from July to September 2017. Patients IOPs were measured in the sitting position, supine without a pillow, and supine with pillow positions using Perkin's handheld applanation tonometer. All data were analyzed with SPSS version 20.0 Results: A total of 55 subjects were recruited comprising 30 (54.5%) males and 25 (45.5%) females, with a mean age of 50.13 ± 9.97 years and an age range of 30–79 years. The mean intraocular pressure was 27.54 ± 3.98 mmHg in the sitting position, 30.15 ± 4.41 mmHg in the supine with pillow position, and 35.22 ± 4.61 mmHg in the supine without pillow position. The mean difference of mean IOP of sitting compared to supine without the pillow was 7.68 ± 2.08 mmHg (P-value < 0.001, 95% CI: 7.12–8.24); sitting compared to supine with the pillow was 2.61 ± 1.49 mmHg (P-value < 0.001, 95% CI: 3.01–2.21), whereas supine without the pillow compared to supine with the pillow was 5.07 ± 2.24 mmHg (P-value 0.001, 95% CI: 4.47–5.68) Conclusion: IOP was lowest in the sitting position and highest in the supine without pillow position. There was a statistically significant reduction in IOP on the assumption of supine with pillow position compared to supine without pillow position. The use of thick pillows in supine positions (such as during sleep or relaxations) rather than lying supine without pillows may reduce IOP spikes in POAG patients. This may have a positive effect as regards treatment and progression of glaucoma.

Keywords: Glaucoma, Intraocular pressure, posture, pressure, sitting, supine flat, supine with pillow


How to cite this article:
Ireka O J, Arinze O C, Ogbu N, Ogbonnaya C E, Nnadozie U U, Chuka-Okosa C M. Posture-induced intraocular pressure changes among patients with primary open angle glaucoma in a Nigerian Tertiary Hospital: Any implication for management. Niger J Clin Pract 2022;25:395-400

How to cite this URL:
Ireka O J, Arinze O C, Ogbu N, Ogbonnaya C E, Nnadozie U U, Chuka-Okosa C M. Posture-induced intraocular pressure changes among patients with primary open angle glaucoma in a Nigerian Tertiary Hospital: Any implication for management. Niger J Clin Pract [serial online] 2022 [cited 2022 May 23];25:395-400. Available from: https://www.njcponline.com/text.asp?2022/25/4/395/343470




   Background Top


Primary open-angle glaucoma (POAG) has been defined as a progressive, chronic optic neuropathy with a characteristic optic disc and visual field changes resulting from the death of retinal ganglion cells and their axons.[1],[2] Elevated intraocular pressure (IOP) has been shown to be the most common risk factor for glaucomatous damage and progression and is currently the only risk factor of glaucoma which is modifiable with effective treatment.[1],[2],[3],[4]

Intraocular pressure is the balance between the rate of aqueous formation by the ciliary body and the rate of fluid drainage from the eye through the trabecular meshwork and uveo-scleral outflow pathways, with the result that any abnormal decrease in the aqueous outflow facility usually leads to chronic elevation of intraocular pressure seen in POAG.[5] This chronic elevation in intraocular pressure causes deformation of the lamina cribosa with resultant compression of ganglion cell axons as well as their blood supply which culminates in impaired axoplasmic flow and poor perfusion of the optic nerve head resulting in the death of these axons and is seen as cupping of the optic nerve head during fundoscopy.[6],[7]

A number of factors have been shown to cause intraocular pressure fluctuations, one of which is a change in posture.[8] Studies have shown that intraocular pressure increases in both normal individuals and subjects with glaucoma when they change from sitting to lying positions.[9–11] This increase in intraocular pressure which occurs on assuming the supine position has been attributed to an increase in episcleral venous pressure which was noted to be constant throughout the day but increased on assuming the supine position.[12] The posture-induced intraocular pressure variation has been noted to be even higher in glaucomatous eyes.[11],[13]

Fluctuations of intraocular pressure with change in posture have been closely associated with the progression of glaucoma and have been correlated with the progression of glaucomatous visual field defects.[14],[15],[16] It has been shown that in most individuals, the peak intraocular pressure occurs during the night when patients assume a reclining/supine position.[17] The IOP in this position is usually not ascertained during routine clinical examination of glaucoma patients as most measurements of intraocular pressure are done in the sitting position. Thus, it is possible that the increased intraocular pressure that occurs on the assumption of supine position during sleep may contribute to the progression of glaucomatous optic neuropathy despite achieving a target pressure.

There is a paucity of data on intraocular pressure variations associated with changes in posture among sub-Saharan African patients with POAG whose disease onset and progression tend to occur earlier and be more aggressive.[18],[19]

The information obtained from this study may form the basis for advocacy for the measurement of IOP in various postures during routine clinical evaluation of POAG patients in the clinic. This will help optimize baseline IOP measurements as well as facilitate a more accurate determination of target IOP. Secondly, the findings from this study will also provide information on IOP measured in different postures. This will support the basis for counseling POAG patients on a possible need to modify postures adopted most of the time of the day (that is adopting the posture that gives the best IOP), with the aim of possibly slowing down the progression of the disease. In the same way that IOP reduction using medications and/or surgery slows the rate of progression of glaucomatous optic nerve damage, IOP reduction may also be achieved by adopting the best identified IOP lowering postures. The purpose of this study, therefore, is to determine the effect of posture on intraocular pressure among sub-Saharan Africans subjects with POAG.


   Materials and Methods Top


Study design

This was a cross-sectional study of newly diagnosed patients with POAGattending the Glaucoma and General Ophthalmology Clinics at Alex Ekwueme Federal University Teaching Hospital, Abakaliki, Ebonyi State from 1st July to 30th September 2017.

Ethical considerations

Ethical approval was obtained from the Research and Ethics Committee of Alex Ekwueme Federal University Teaching Hospital, Abakaliki, Ebonyi State in line with the World Medical Association Declaration of Helsinki. All recruited patients were fully informed of the procedures for the prestudy evaluation. Details concerning further assessment and measurements of intraocular pressure in different positions were further explained to those who met the inclusion criteria. A duly signed, written, or thumb-printed consent was also obtained before patients' participation.

Inclusion criteria

Patients aged 30 years or older who

  1. Gave voluntary consent.
  2. Were not hypertensive or diabetic.
  3. Were not on any medication known to influence intraocular pressure.
  4. Were diagnosed with POAG using the following diagnostic criteria:


  1. Open anterior chamber angle (Shaffer's grade 3 or 4 in all quadrants)
  2. Raised intraocular pressure ≥22 mm Hg, this is the true IOP after accounting for central corneal thickness (via pachymetry).
  3. A vertical cup-disc ratio of ≥0.6 or asymmetry of disc cupping equal to or greater than 0.2 with or without the following disc changes: a rim notching or thinning of the rim, disc hemorrhage, or violation of the inferior > superior > nasal > temporal (ISNT) rule seen on dilated fundoscopy using +78 D in one or both eyes.
  4. Characteristic glaucomatous visual field defects such as nasal step, paracentral scotoma, temporal wedge defect, seidel scotoma, arcuate scotoma, double arcuate scotoma, seen on automated perimetry using Optos Automated Perimeter Model AP 200 may or may not be present.


Exclusion criteria

  1. Patients with glaucoma aged less than 30 years.
  2. Patients with POAG aged 30 years and above who did not give consent to participate in the study.
  3. Patients who were diagnosed with POAG before this study.
  4. Patients aged 30 years and above with other types of glaucoma.
  5. Subjects with POAG aged 30 years and above with previous ocular surgeries.
  6. Subjects with POAG aged 30 years and above with anterior segment pathologies such as acute or chronic uveitis.
  7. Subjects with POAG aged 30 years and above with any corneal abnormality that would prevent reliable intraocular measurement such as corneal opacity.


Clinical evaluation

Consecutive new patients aged 30 years or older seen in the Glaucoma Subspecialty Clinic within the study period and who satisfied the inclusion criteria were selected. The patients' biodatas were collected. Each patient underwent a comprehensive ophthalmic evaluation which included a detailed history and systemic review. Assessment of visual acuity, pupillary reactions to light, and anterior segment was also done. IOP was measured using Perkin's handheld applanation tonometer. Pachymetry was also done to ascertain the central corneal thickness. Gonioscopy was performed using the Goldmann 2-mirror lens, and the angles were graded using Shaffer's grading system. Dilated fundoscopy using topical tropicamide was done, and the fundus was examined using the slit lamp and +78D lens. Automated perimetry using the Optos Automated Perimeter Model AP 200 was also performed on each of the patients.

Measurement of intraocular pressure in various postures

The enrolled subjects had their intraocular pressure measured with Perkin's handheld applanation tonometer. Measurements of intraocular pressure were taken in three positions namely sitting, supine without a pillow, and supine with a pillow. The subjects were instructed to sit quietly near one end of an examination couch. A topical anesthetic, 0.5% tetracaine hydrochloride, was instilled into the eyes. Then, a fluorescein sodium strip of 1 mg was inserted into the inferior conjunctiva sac for a few seconds and then removed.

The intraocular pressure of one eye, (right before left), was measured 15 min after the patient maintained a sitting position. The subject then assumed a supine without a pillow position. This body position was maintained for 15 min after which the intraocular pressure was measured. Then, a thick pillow was placed underneath the patient's head (achieving a head elevation of 30°), and intraocular pressure was recorded after 15 min of maintaining this posture. The same dimension (65 cm × 45 cm × 23 cm) and density of pillows were used for all patients. The dimensions and densities of the used pillows were periodically checked. There were multiple spare pillows of the same dimension and density which were used to replace any pillow that did not meet the requirements.

The same researcher measured the intraocular pressure of all the participants and measurements were taken between 10 am and 12 noon to minimize the effect of diurnal variations on intraocular pressure.[20],[21] Excessive pressures on the globe as well as corneal abrasion resulting from rough handling of instruments were avoided during intraocular pressure measurement.

Data entry and management

Using an anticipated mean change in the intraocular pressure of 4.1; the sample size was calculated to be 55 at a standard deviation of 2.6 and with a power of 90%. All statistical analyses were performed using SPSS version 20.0.

The IOP measurements for right and left eyes in each position were compared using paired t-tests. The IOP of both eyes was then averaged, and paired t-tests were used to compare the measurements in different positions. A P value of < 0.05 was considered statistically significant.


   Results Top


A total of 55 patients (110 eyes) participated in the study. There were 30 males (54.5%) and 25 females (45.5%) with a mean age of 50.13 ± 9.97 and an age range of 30–70 years. Their gender distribution and basic parameters are shown in [Figure 1] and [Table 1], respectively.
Figure 1: Gender distribution of subjects

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Table 1: Basic parameters of the patients

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[Table 2] shows the mean IOP variations with postural changes between the two eyes among the POAG patients. The mean IOP upon sitting was 27.54 ± 3.98, which was lower than that obtained in supine without a pillow (35.22 ± 5.4.61), and supine with a pillow (30.15 ± 4.41) positions. These differences in mean IOPs were all statistically significant, (P < 0.001).
Table 2: IOP differences between the various postures among patients

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   Discussion Top


This study has shown that posture-induced intraocular pressure variations occurred in sub-Saharan African subjects with POAG. Several studies[10],[11],[13] have previously established that IOP can be altered by changing body position in subjects with glaucoma. However, contrary to our study which was purely on newly diagnosed sub-Saharan African patients with POAGwho had not commenced any form of treatment, these studies were done on mainly Caucasian patients already diagnosed with glaucoma and who had commenced one form of treatment. The presumed advantage in our study population is that the alterations in IOP by changing body positions is purely a physiological response that was not affected by any IOP lowering drug or procedure.

It is believed that the increase in IOP in dependent posture is probably related to an increase in episcleral venous pressure and choroidal vascular volume that is associated with the cephaloid fluid shift occurring during head-down tilt due to gravity-induced orthostatic venous pressure gradient.[9] Orbital pressure probably increases quickly upon dependent posture because of numerous interconnections between the orbital drainage routes and the lack of venous valves in the orbit. Furthermore, congestion and expansion of the uveal tissue from increased venous and arterial pressures within the orbit probably also plays an important role. These congested orbital contents and the resultant increase in ocular blood volume produce mechanical compression of the globe against the orbit.[9]

The posture-induced IOP variations observed in our study corroborated with several previous studies[14],[16] although a greater increase in intraocular pressure was observed in our subjects when moving from sitting to the supine flat position. Kiuch[14] for instance reported a mean intraocular pressure difference of 4.5 mm Hg when moving from sitting to supine position, whereas our study reported 7.6 mmHg. The subjects in Kiuch's[14] study were, however, untreated normal-tension glaucoma patients, whereas the subjects in this study were untreated POAG patients. In the same vein, Hirooka et al.[16] reported an average intraocular pressure increase of 4.0 ± 0.2 mmHg in POAGsubjects and 3.1 ± 0.4 mmHg in normal subjects (without glaucoma or any other ocular pathology) as they moved from sitting to supine position. The lower mean intraocular pressure change recorded by Hirooka[16] when compared with the result of our study could be explained by the differences in sample size and study population. Their sample size was relatively smaller, and their subjects included patients with and without glaucoma. In addition, their glaucoma subjects were already on medications.

The above findings bring to light the need to measure IOP at various postural positions during routine examinations (and not just in the sitting position as is routinely done) in a glaucoma clinic. The consequence is that the mean IOP calculated from the different positions may now actually reflect the true nature of the IOP control in these patients as well as help in calculating each patient's target pressure. This can help in slowing down the disease progression as the true IOP, and a more accurate target pressure has been determined.

It is also important to note that although the mean posture induce IOP rise observed by Hiroka[16] in normal subjects was less than that observed in patients with glaucoma, the findings suggest that physiological posture-induced IOP rise in individuals tend to be more exaggerated if one develops glaucoma. This is supported by the findings in our study and that of Kiuch,[14] both of which reported a higher rise in posture-induced IOP-, 7.6 mm Hg and 4.0 mmHg, respectively when moving from the sitting to supine without pillow position. Thus, it may be necessary to research the various physiological mechanisms (ocular and nonocular) that contribute to posture-induced IOP changes in order to detect any abnormalities therein that may contribute to IOP rise in patients with glaucoma.

Upon elevation of the head with a pillow from a supine flat position, the mean intraocular pressure in our subjects reduced to 5.07 mmHg which was lower than that obtained in the supine flat position in the same subjects. This is in keeping with the report by Yvonne et al.[11] who reported that a mean IOP reduction occurred in glaucoma patients (on medication) on adoption of a 30° head elevation compared with supine the flat position. Their findings were similar to the results of our study even though the method of head elevation used in this study was achieved with the use of a thick pillow and subjects who participated in our study were not yet on antiglaucoma drugs.

A study by Yeon et al.[22] reported that intraocular pressure increased in some patients after changing from a supine without a pillow to supine with multiple pillows position. Our study, however, showed that intraocular pressure was significantly lower when changing from supine without a pillow to supine with pillow position. The contrast could be explained by the difference in study population and study design of the two studies. While subjects in Yeon's[23] study were healthy nonglaucoma patients younger than 40 years, subjects employed in the present study were glaucoma patients aged 30–70 years. In addition, the use of multiple pillows to achieve head elevation may produce a different effect compared to the use of a single pillow of appropriate density as was used in our study.

It is worthy to note that though subjects used in this study were POAGpatients who had not undergone any form of treatment, the findings from this study may not be directly extrapolated to glaucoma patients who are already on any form of treatment. Further comparative studies may be required. Additionally, the intraocular pressure for this study was measured at a specific period between 10 am and 12 noon, and this may not adequately factor in the effect of diurnal variation in intraocular pressure. Further studies on posture-induced IOP changes taking into account the IOP at other times of the day may be necessary.

In conclusion, this study confirmed that among patients with glaucoma, posture-induced intraocular pressure variations occur, and IOP was lower in sitting compared with supine positions. Intraocular pressure in the supine positions was observed to be lower when a thick pillow was used to elevate the head compared to supine without pillow position. These findings indicate that head elevation with the use of a thick pillow may reduce intraocular pressure rise which occurs upon adopting a supine position, especially during sleep and relaxation. Thus, encouraging patients with glaucoma to sleep with thick pillows as part of their treatment protocol can have positive and better treatment outcomes in the management of glaucoma patients.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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