Mitigation of the IOP elevation associated with non‐supine sleep positions

Abstract

AbstractPurpose When a person sleeps in a non‐supine position, the load path through which the weight of the head is transferred to a supporting surface (a pillow, the mattress, an arm, etc.) generally includes one eye. This research quantifies the forces that act on the eye and the potential for extended periods of intraocular pressure (IOP) elevation when the eye is a load bearing element in the "head‐to‐bed" load path.Methods An engineering model of the load path is used to quantify nominal loads on the eye when in side‐ and face‐down sleep positions. The eye is modeled as a fluid filled, thin walled pressure vessel and is included as a load‐bearing structural element in the head‐to‐bed load path. The model is used to simulate a device that provides as alternative load path to mitigate sleep position related elevation of IOP.Results Predictions from a lumped parameter model indicate that individuals who sleep in non‐supine positions will experience elevation of IOP of 3‐5 mmHg. A more sophisticated eye model is used to incorporate deformation of the eye and to show the lumped parameter model estimates of IOP elevation are conservative. This result is supported by a recently published experimental study of measured IOP elevation in dogs during eye manipulation [Keing et al., 2011] which suggests that relatively modest deformations of the eye can nearly double measured IOP levels. A non‐invasive method for alleviation of the external forces that act on the eye during non‐supine sleep is described as a means for altering this load path.Conclusion These results suggest that patients with normal IOP levels during the day may experience significant elevation of IOP levels due to sleeping in non‐supine positions. An approach to mitigate this mechanism of IOP elevation is presented.