A recent study published in the British Journal of Ophthalmology evaluated the association between high-pillow sleeping posture with changes in intraocular pressure (IOP) in glaucoma patients.
Give me some background.
IOP typically follows a distinct circadian rhythm, with peak values occurring during nocturnal periods—highlighting the importance of nocturnal IOP management.
Moreover: IOP exhibits significant fluctuations in response to changes in body posture, with the transition from an upright to a supine position during sleep representing the primary contributor to nocturnal IOP elevation.
- For example: Relative to the supine position, the lateral decubitus position elevates IOP by 1.5-3.2mmHg in the inferior eye and the prone position induces an even more pronounced IOP elevation of ~5mmHg.
As such: Postural modification during sleep may serve as a potential adjunctive strategy for IOP management in glaucoma patients.
Now talk about the study.
Between October 2023 and April 2024, investigators analyzed the right eye of 144 glaucoma patients who underwent comprehensive ophthalmologic exams and IOP measurements taken every 2 hours for a 24-hour period when sitting and lying down.
- When supine, participants’ heads were raised with two normal-sized pillows (head elevated by 20-35°) and their IOP was measured 10 minutes later.
Then: Patients reverted to sleeping on their backs until the next measurement.
- In total, four sets of complete measurements were obtained for each participant with and without pillows.
In addition: Changes in jugular venous lumen in response to postural variation were evaluated via ultrasonography in 20 healthy volunteers.
Anything else?
More information on the cohort:
- Ages:
- >44 years: 84 participants
- 45 to 59 years old: 41 participants
- 60+ years old: 19 participants
- Glaucoma subtypes:
- Normal-tension glaucoma (NTG): 70 patients
- Ocular hypertension (OHT): 9 patients
- Primary open-angle glaucoma (POAG): 65 patients
Findings?
In the cohort, 96 (67%) of participants had a demonstrable increase in IOP when transitioning from supine to an elevated position, with an average increase of ~1.61 mmHg.
Compared with the supine position, the high-pillow position was associated with (all p<0.001):
- Significantly elevated IOP (17.42 mmHg vs. 16.62 mmHg)
- Increased 24-hour IOP fluctuation
- Reduced ocular perfusion pressure (OPP; 54.57 mmHg vs. 58.71 mmHg)
Greater postural IOP fluctuation (ΔIOP) was observed in younger individuals (p=0.027) and patients with primary open-angle glaucoma (POAG, p<0.001).
Multiple regression analysis identified thicker central corneal thickness and the presence of POAG (vs. normal-tension glaucoma) as positive predictors of larger ΔIOP changes (both p<0.05).
And how did postural variation affect the jugular venous lumen?
Ultrasonography in healthy volunteers revealed significant constriction of both internal and external jugular venous lumen in the high-pillow position (all p<0.001), accompanied by an increase in maximum blood flow velocity of the internal jugular vein (p=0.013).
Expert opinion?
Based on the findings, the study authors concluded that positional adjustments of the head during sleep may inadvertently lead to neck flexion—which could potentially mechanically constrict the jugular veins, thereby impeding aqueous humor outflow and subsequently elevating IOP.
And while previous studies have shown that semi-reclining positions (achieved via wedge pillows or elevated bedheads) resulted in significant IOP reduction compared with the supine position, this discrepancy may be caused by distinct effects on cervical biomechanics.
- How: The use of a wedge pillow to elevate the upper body promotes cervical extension, whereas adopting a high-pillow position primarily alters head posture, resulting in neck flexion.
Any limitations?
A few to note, including:
- As this study aimed to observe postural IOP changes during sleep under real-life physiological conditions, the investigators did not restrict the high-pillow position to a specific angle
- Ultrasonography was conducted as an independent supplementary assessment following IOP measurement, with distinct study populations for the two procedures
- Given the limited sample size within each glaucoma subtype and the wide dispersion of ΔIOP values, the confidence interval for the beta coefficient in the POAG group was broad
Take home.
These findings demonstrated that compared to the supine position, the high-pillow position was associated with elevated IOP, increased 24-hour IOP fluctuation, and decreased OPP in glaucoma patients.
Plus: This association may be linked to jugular venous compression induced by neck flexion, which could potentially compromise venous return and aqueous humor outflow.
Consequently: Patients with glaucoma may benefit from avoiding sleeping postures that induce jugular venous compression to mitigate postural IOP elevation.
- However: Further studies are required to validate these preliminary associations.