A Protective Eye Shield Reduces Limbal Strain and Its Variability During Simulated Sleep in Adults With Glaucoma

Effect of Sleeping Position on the Retinal Nerve Fiber Layer in Individuals with Glaucoma

Aims and background

To evaluate the effect of sleeping in the lateral decubitus position on the average thickness of the retinal nerve fiber layer (RNFL) in the peripapillary region of the optic nerve since the effect of posture on intraocular pressure (IOP) and glaucoma progression is not yet sufficiently understood.

Materials and methods

A cross-sectional observational study was carried out with 40 volunteers who preferably slept in a right lateral decubitus (RLD) (RLD group N = 20) and left lateral decubitus (LLD) (LLD group N = 20) position. IOP was measured in both eyes, first in the sitting position and again after 10 minutes in a supine position, right lateral, and LLD, respectively. The mean thickness of the RNFL and the vertical papillary cup were measured by optical coherence tomography.

Results

The average age of the volunteers was 60.53 ± 7.26 years. There were 32 female and eight male. There was an increase in IOP with the change from the sitting position to the lateral decubitus of 2.7 and 3.6 mm Hg in the RLD group (p < 0.001) and an increase of 3.0 and 3.15 mm Hg in the LLD group (p < 0.001), right eye (RE) vs left eye (LE), respectively. However, there was no difference in IOP values between the groups. The average thickness of the RNFL was in the RLD group-75.10 vs 78.05 μm (p = 0.325) and in the LLD group-81.55 vs 79.95 μm (p = 0.580). Vertical papillary excavation was in the RLD group-0.70 vs 0.65 (p = 0.175) and in the LLD group-0.65 vs 0.65 (p = 1.000), RE vs LE, respectively.

Conclusion

We found no relationship between the lateral decubitus position when adopted preferentially for sleeping and the reduction of the RNFL.

Clinical significance

Search for risk factors for the asymmetrical development of glaucoma, especially in well-controlled IOP in daytime measurements.

How to cite this article

Vaz RT, Montenegro AAL, Quintas Segundo ADS, et al. Effect of Sleeping Position on the Retinal Nerve Fiber Layer in Individuals with Glaucoma. J Curr Glaucoma Pract 2024;18(2):57-62.

IOP and glaucoma damage: The essential role of optic nerve head and retinal mechanosensors

There are many unanswered questions on the relation of intraocular pressure to glaucoma development and progression. IOP itself cannot be distilled to a single, unifying value, because IOP level varies over time, differs depending on ocular location, and can be affected by method of measurement. Ultimately, IOP level creates mechanical strain that affects axonal function at the optic nerve head which causes local extracellular matrix remodeling and retinal ganglion cell death - hallmarks of glaucoma and the cause of glaucomatous vision loss. Extracellular tissue strain at the ONH and lamina cribrosa is regionally variable and differs in magnitude and location between healthy and glaucomatous eyes. The ultimate targets of IOP-induced tissue strain in glaucoma are retinal ganglion cell axons at the optic nerve head and the cells that support axonal function (astrocytes, the neurovascular unit, microglia, and fibroblasts). These cells sense tissue strain through a series of signals that originate at the cell membrane and alter cytoskeletal organization, migration, differentiation, gene transcription, and proliferation. The proteins that translate mechanical stimuli into molecular signals act as band-pass filters - sensing some stimuli while ignoring others - and cellular responses to stimuli can differ based on cell type and differentiation state. Therefore, to fully understand the IOP signals that are relevant to glaucoma, it is necessary to understand the ultimate cellular targets of IOP-induced mechanical stimuli and their ability to sense, ignore, and translate these signals into cellular actions.

Relationship between sleep position and glaucoma progression

PURPOSE OF REVIEW

As humans spend a considerable portion of life in the horizontal position, it is vital to better understand the effect of sleep position on glaucoma.

RECENT FINDINGS

The mean positional increase from the supine position to the lateral decubitus position (LDP) in recent literature is less than 2 mmHg for each eye in its dependent position and less than 1 mmHg in the nondependent position. The right LDP is most commonly favored sleeping position. Some evidence suggests that the positional increases persist and so could lead to worse glaucomatous progression in the dependent eye. However, multiple studies failed to find a strong association. Ideally future research will identify risk factors for higher positional increases to identify patients who may benefit from a change in sleep position. To date, medications and argon laser trabeculoplasty have been ineffective in blunting the positional increase, although glaucoma surgery does reduce it. Raising the head of the bed has been linked with blunting the increase as well.

SUMMARY

Certain sleeping positions appear to be associated with higher intraocular pressure, although the association between sleep position and glaucoma progression is not as clear.

Is a pillow a risk factor for glaucoma?

Purpose

To study whether a clinically significant increase in intraocular pressure (IOP) occurs during simulated sleep conditions with the subject's head turned comfortably into a pillow (the simulated sleep position) and the effect of protective glasses on any such IOP rise.

Methods

A specially developed electronic epipalpebral pressure (EPP) sensor was attached to an eyelid of the right eye of all participants: 11 patients with primary open‐angle glaucoma and 11 healthy volunteers. During calibration, mechanical pressure was applied to the EPP sensor taped to the lower eyelid and the IOP was measured simultaneously at the slit lamp by Goldmann applanation tonometry. The EPP was increased in a stepwise fashion to assess the relationship between EPP and IOP for each individual eye. Thereafter, EPP (with the sensor now taped to the upper eyelid) measurements were performed in the simulated sleep position, both with and without protective glasses. The EPP was determined in each individual eye, and the estimated IOP was then inferred from the established EPP/IOP relationship.

Results

In the simulated sleep position, the mean IOP increased by an estimated 19.6 mmHg (SD: 7.5; range 11.6–32.8; p < 0.0001) in the patient group and 28.0 mmHg (SD: 9.6; range 12.3–41.1); p < 0.0001) in the control group. When the subjects wore protective glasses, the mean estimated IOP decreased again by 16.3 mmHg (SD: 5.6; range 9.8–28.1; p < 0.0001) in the patient group and 25.1 mmHg (SD: 8.2; range 11.7–38.3; p = <0.0001) in the control group.

Conclusion

Turning the head into a pillow gave a large and clinically significant increase in the estimated IOP in the simulated sleep position. With protective glasses, however, the increase in estimated IOP was almost absent. Therefore, protective shielding of the eyes during sleep may be a treatment option in glaucoma.