Interim Mixed Model Analysis of an Adjustable Magnetic Levator Prosthesis for Severe Ptosis

Abstract

Purpose : The Magnetic Levator Prosthesis (MLP) is a promising non-surgical intervention for severe ptosis that employs magnets placed on the spectacles and on the upper lid. We hypothesized that magnet orientation (Figure 1) would affect Interpalpebral Fissure (IPF) between and within blinks and subject-reported comfort.

Methods : IPF was measured manually using ImageJ from 15s video recording for 5 polarity angles: 0° (poles aligned), 30°, 60°, 90°, and 180° (reverse polarity). Participants reported comfort on a 10-point scale at each rotation position while wearing the MLP. Linear mixed models included rotation position as a fixed effect and also rotation position within subject-eye as random effects (allows subjects to differ from one another).

Results : Eye opening improved for 4 of 5 rotations by 0.9 to 2.5mm (p<0.001). Considerable unexplained variance suggested the presence of other factors not included in the model. Comfort rating varied between some rotation positions (p<0.001), and higher comfort was strongly associated with more eye opening between blinks (p<0.001), but only weakly with closure on the blink (p=0.05). Comfort with impeded blink would be expected to worsen with longer wear times.

Conclusions : Our primary hypothesis was confirmed, however, there are remaining factors that affect IPF pattern across rotation angles between subjects that need to be determined. Potential factors for future study include age, physiological differences (brow height and eyelid shape), and the baseline ptosis severity. The MLP’s ability to adjust the force on the eyelids is promising for severe ptosis and potentially opens the possibility for complete blink re-animation in total paralysis.

This is a 2021 ARVO Annual Meeting abstract.

 

Figure 1. Schematic of the MLP with rotation adjustment mechanism.