Feasibility of Magnetic Levator Prosthesis Frame Customization Using Craniofacial Scans and 3-D Printing

Abstract

Purpose To determine the feasibility of a custom frame generation approach for nonsurgical management of severe blepharoptosis with the magnetic levator prosthesis (MLP). Methods Participants (n = 8) with severe blepharoptosis (obscuring the visual axis) in one or both eyes who had previously been using a non-custom MLP had a craniofacial scan with a smartphone app to generate a custom MLP frame. A magnetic adhesive was attached to the affected eyelid. The custom MLP frame held a cylindrical magnet near the eyebrow above the affected eyelid, suspending it in the magnetic field while still allowing blinking. The spectacle magnet could be rotated manually, providing adjustable force via angular translation of the magnetic field. Fitting success and comfort were recorded, and interpalpebral fissure (IPF) was measured from video frames after 20 minutes in-office and one-week at-home use. Preference was documented, custom versus non-custom. Results Overall, 88% of patients (7/8) were successfully fitted with a median 9/10 comfort (interquartile 7–10) and median ptosis improvement of 2.3 mm (1.3–5.0); P = 0.01). Exact binomial testing suggested, with 80% power, that the true population success rate was significantly greater than 45% ( P = 0.05). Five participants took the custom MLP home for one week, with only one case of mild conjunctival redness which resolved without treatment. Highest to lowest force modulation resulted in a marginally significant median IPF adjustment of 1.5 mm (0.8 to 2.7; P = 0.06). All preferred the custom frame. Conclusions The three-dimensional custom MLP frame generation approach using a smartphone app–based craniofacial scan is a feasible approach for clinical deployment of the MLP. Translational Relevance First demonstration of customized frame generation for the MLP.

A Magnetic Actuator Device for Fully Automated Blinking in Total Bidirectional Eyelid Paralysis: First Proof of Concept in a Human Participant

“…One possible measure to enhance stability involves the utilization of patient-specific custom three-dimensional printed frames, a strategy previously employed for standard MLP designs with success. 20 Considering the patient's anatomy, support points can be preferentially placed near the frame magnet, increasing stability. Additional support structures can be incorporated while ensuring comfort.…”

An adjustable magnetic levator prosthesis for customizable eyelid reanimation in severe blepharoptosis: Design and proof-of-concept

“…Substantial force changes occur with frame movements as small as 1mm, therefore a more stable frame is paramount. This can be accomplished using custom designed 3D printed spectacle frames, specifically designed for the individual user, as reported previously in a recent phase I study (Houston and Paschalis 2022).…”

Clinical Report: Clinician Feedback on the Magnetic Levator Prosthesis

“…In our experience, surgical treatment is frequently denied to these orphan disease patient groups because of the characteristic daily or even hourly variability of blepharoptosis severity and needs for repeated surgery over a lifetime. Safety and efficacy data for these populations exist from our ongoing 4 and prior clinical trials, 5,6 although these represent subpopulations of our clinical trial study sample, which is already small. This is a well-known problem for rare disease studies and may be addressed by n-of-1 trial analysis methods of repeated measures over time and blinded crossovers 17 .…”

“…With force properly titrated, the facial muscles of eye closure (orbicularis oculi) can easily overcome the attractive force to allow comfortable blinking without any power supply, making a relatively lightweight and inexpensive device. In two prior open-label studies (combined n = 20), there was an 80% in-office fitting success with median comfort rating of 8.5 of 10 and no serious adverse events during 1 week or more of use 5,6 …”

“…In two prior open-label studies (combined n = 20), there was an 80% in-office fitting success with median comfort rating of 8.5 of 10 and no serious adverse events during 1 week or more of use. 5,6 Although there are other nonsurgical approaches for severe ptosis including oxymetazoline eye drops, scleral contact lenses, skin tape, and ptosis crutch, they all carry substantial limitations that might be overcome by the MLP. Oxymetazoline drops, which activate Muller's muscle to provide approximately 1 mm of improvement in lid position 7 and oversized scleral contact lenses, which may mechanically elevate the lid, [8][9][10] do not likely provide enough opening to address severe cases of ptosis such as the case in Fig.…”