Evaluation of the preferred sleeping position as a risk factor for keratoconus asymmetry

Identifying potential modifiable risk factors for keratoconus progression is crucial for better outcomes. This study suggests that sleeping position may contribute to interocular asymmetry in keratoconus, providing an actionable target for patient education and clinical management and underscoring the importance of sleep posture in slowing disease progression.

This study aimed to investigate whether the preferred sleeping position can contribute to interocular asymmetry of keratoconus.

A clinical cross-sectional study was conducted on 50 patients (100 eyes) with grade I and II keratoconus (Amsler-Krumeich) and 40 individuals (80 eyes) without keratoconus. Corneal tomographic parameters from the Galilei G6 (keratometry plus curve [Steep K], mean keratometry [Sim K], thinner corneal thickness, central corneal thickness, Cone Location and Magnitude Index, dioptric asymmetry between the inferior and superior corneal hemispheres, and vertical coma) were obtained to assess interocular asymmetry. All participants answered a questionnaire about their preferred sleeping position. The eye positioned lower during sleep has been referred to as the dependent eye, and the eye positioned higher was classified as the nondependent eye, regardless of the sleeping position (lateral or ventral).

There were no significant differences between dependent and nondependent eyes regarding the evaluated tomographic variables among individuals without keratoconus. However, in individuals with keratoconus, statistically significant differences were observed between dependent and nondependent eyes for the following parameters: Steep K (47.89 vs. 45.78 D, p=0.0047), Sim K (46.54 vs. 44.42 D, p=0.0016); thinnest corneal thickness (445.84 vs. 460.34 μm, p=0.0057), central corneal thickness (463.03 vs. 477.6 μm, p=0.0125), vertical coma (-1.98 vs. -1.41 μm, p=0.0448), and total coma (1.60 vs. 1.22 μm, p=0.0495).

This study suggests that in individuals with keratoconus, the preferred sleeping position may contribute to keratoconus asymmetry in the dependent eye, regardless of whether the sleeping position is lateral or ventral.