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Kevin Houston, Nish Mohith Kurukuti, James Chodosh, Eleftherios I Paschalis, Michael Yoon; Can simple angular translation of static magnetic fields provide adjustable force in magnetic correction of blepharoptosis?. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2224.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if angular rotation of the magnetic levator prosthesis (MLP) magnetic field (Houston et al., 2014) results in a clinically significant change in lid position and therefore may be a useful innovation to allow adjustable force in the magnetic correction of ptosis.
An adjustable force MLP prototype was produced consisting of 3 small N52 magnets embedded in silicone (lid array) attached to the lid with medical adhesive and a larger cylindrical N52 magnet in a 3-D printed rotatable casing on a spectacle frame. The magnet casing sits above the affected eye, resulting in upward force on the lid array to lift the lid. The intent is to allow titration of the force such that the lid is open but can still overcome the force to blink naturally. To test this concept, subjects with severe ptosis having negative MRD (without frontalis recruitment) were fitted with the prototype and the interpalpebral fissure was measured at 0° (poles aligned), 30°, 60°, 90° (counterbalanced) while comfort was monitored with a Likert-type scale (best comfort = 10). ImageJ was used to measure interpalpebral fissure (IPF) over 15s of 30Hz recording at each force setting. A 20-minute followed by a home trial were offered if acceptable fitting was obtained (clinician judgment). Reasons for fitting failure were documented.
Ten eyes of 8 subjects have completed the initial fitting thus far (n=30 planned). Ptotic IPF was 4.6mm ±2.8 improving on the lowest force setting to 6.7mm ±1.9 (p=0.001) and significantly more on the highest setting (poles aligned) to 8.9 ±1.6 (p<0.001). The mean change from lowest to highest was 2.2mm ±1.3, with 70% of eyes meeting a predefined ≥1mm clinical significance criterion. The force setting providing the best-fit varied substantially between subjects. Median comfort at the best setting was 8/10 (IQR 6 to 9). Only 4/10 subjects progressed to the 20min trial and 3/10 to the home trial. The main reason cited for failure to move on to extended trials was poorly fitting frame – there was only 1 frame option at the time.
The adjustable force feature shows promising preliminary results for use in the MLP, and continued study is warranted. Additional frame designs including custom 3-D printed frames based on craniofacial scans are being tested to address failures due to poorly fitting frames.
This is a 2020 ARVO Annual Meeting abstract.
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