Expert Review of Medical Devices
ISSN: 1743-4440 (Print) 1745-2422 (Online) Journal homepage: http://www.tandfonline.com/loi/ierd20
Open source modular ptosis crutch for the
treatment of myasthenia gravis
Trust Saidi, Sudesh Sivarasu & Tania S. Douglas
To cite this article: Trust Saidi, Sudesh Sivarasu & Tania S. Douglas (2017): Open source
modular ptosis crutch for the treatment of myasthenia gravis, Expert Review of Medical Devices,
DOI: 10.1080/17434440.2018.1421455
To link to this article: https://doi.org/10.1080/17434440.2018.1421455
Accepted author version posted online: 22
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Download by: [University of New England]
Date: 23 December 2017, At: 10:53
Publisher: Taylor & Francis
Journal: Expert Review of Medical Devices
DOI: 10.1080/17434440.2018.1421455
Open source modular ptosis crutch for the treatment of myasthenia gravis
Trust Saidi1*, Sudesh Sivarasu2 and Tania S. Douglas3
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1*
University of Cape Town
Department of Human Biology
Division of Biomedical Engineering
P. Bag X3
Observatory, 7935
Cape Town, South Africa
trust.saidi@uct.ac.za
2
University of Cape Town
Department of Human Biology
Division of Biomedical Engineering
P. Bag X3
Observatory, 7935
Cape Town, South Africa
sudesh.sivarasu@uct.ac.za
3
University of Cape Town
Department of Human Biology
Division of Biomedical Engineering
P. Bag X3
Observatory, 7935
Cape Town, South Africa
tania.douglas@uct.ac.za
*corresponding author
Abstract
Introduction: Pharmacologic treatment of Myasthenia Gravis presents challenges due to poor
tolerability in some patients. Conventional ptosis crutches have limitations such as interference
with blinking which causes ocular surface drying, and frequent irritation of the eyes. To address
this problem, a modular and adjustable ptosis crutch for elevating the upper eyelid in Myasthenia
Gravis patients has been proposed as a non-surgical and low-cost solution.
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Areas covered: This paper reviews the literature on the challenges in the treatment of
Myasthenia Gravis globally and focuses on a modular and adjustable ptosis crutch that has been
developed by the Medical Device Laboratory at the University of Cape Town.
Expert commentary: The new medical device has potential as a simple, effective and
unobtrusive solution to elevate the drooping upper eyelid(s) above the visual axis without the
need for medication and surgery. Access to the technology is provided through an open source
platform which makes it available globally. Open access provides opportunities for further open
innovation to address the current limitations of the device, ultimately for the benefit not only of
people suffering from Myasthenia Gravis but also of those with ptosis from other aetiologies.
Key words: myasthenia gravis, ptosis crutch, adjustable ptosis, developing countries; open
innovation
1. Introduction
Myasthenia Gravis (MG) is an antibody-mediated autoimmune disease attributed to abnormalities
of the thymus gland and genetic predisposition [1, 2]. The autoimmune reaction is directed
against the nicotinic acetylcholine receptors of the neuromuscular junction [3], obstructing
normal function and disrupting neuromuscular transmission [4, 5]. The disease causes fatigable
weakness of skeletal muscles, commonly affecting the eye and facial muscles and leading to
blurred vision or drooping eyelids [6, 7]. Usually, the weakness of the susceptible muscle
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fluctuates, and tends to worsen with activity and to improve with rest [8].
Patients with
significant MG may need to tilt their head back into a chin-up position, lift their eyelid with a
finger, or raise their eyebrows [9, 10]. The continuous activation of the forehead and scalp
muscles may additionally cause tension headache and eyestrain [11, 12].
Globally, MG is a relatively rare disease as it affects about 3-30 per 100 000 persons depending
on geographic location [13, 14]. The incidence of the disease is increasing and has more than
doubled in the last 20 years in Western countries as well as in Japan and Taiwan [1, 15, 16]. This
is most likely to be a result of improved diagnosis [16] and greater ability of neurologists to
differentiate MG symptoms from classical fatigue due to aging [1]. Diagnosis of the disease can
be done by the ice or ice pack test, a clinically simple, safe, and affordable procedure for the
diagnosis of ocular MG [17, 18]. Myasthenic ptosis is known to improve with cold and therefore
the ice pack test is used as a tool for differential diagnosis [19]. The test is conducted by placing a
surgical glove filled with crushed ice on the more ptotic eyelid for about 2 minutes and
evaluating the effect of ice application on the ptosis [20, 21]. If the disease is present, the ptosis
is substantially diminished (>5 mm) and this is used to distinguish MG from other causes of
ptosis or ophthalmoparesis [22]. Repetitive nerve stimulation is another method used to diagnose
neuromuscular junction disorders associated with myasthenia gravis [23, 24, 25]. It involves
electrical stimulation to a motor nerve several times per second followed by assessment for a
neuromuscular junction disorder [26, 27, 28]. A decremental response of ≥ 10% between the
first and fifth compound muscle action potential is suggestive of the presence of MG [29].
Edrophonium chloride (tensilon) assists in diagnosing a muscle disorder in myasthenia gravis as
patients who are positive for the disease show an improvement in muscular strength following
administration of the drug [30, 31]. Oral pyridostigmine bromide (mestinon) is undergoing
clinical trials as an alternative approach for the diagnosis of MG [32, 33] due to its ability to
produce rapid results [34]. It blocks an enzyme that breaks down acetylcholine, the chemical
that transmits signals from nerve endings to muscles, resulting in temporary improvement in
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weakness of the eye muscles, an indication of the presence of MG [35].
The occurrence of MG varies by sex and age with women being affected nearly three times more
often than men during early adulthood [8, 36]. In Europe and North America, MG is not common
in children, who comprise only 10–15% of cases [8, 37]. In Asian countries such as China up to
50% of patients have disease onset under the age of 15 years [38]. While MG affects individuals
of all racial groups across the world, previous studies have revealed that patients of African
genetic ancestry, particularly juveniles, are more likely to develop an ocular muscle complication
of MG compared to their European counterparts [39]. Studies by Andrews et al. [22] and Philips
[23] revealed that the onset of MG before puberty may be more frequent in American children
with African genetic ancestry compared to those with European genetic ancestry [40, 41].
Another study by Mombaur suggested that there may be a higher incidence of MG among
children with African genetic ancestry in South Africa [42]. Thus, MG appears to
disproportionately affect children of African genetic ancestry.
Although MG can be treated [43, 44], results from a study on the phenotypic variation of subjects
from a multi-racial South African cohort revealed that Black subjects were more likely than
Whites to develop treatment-resistant complete ophthalmoplegia and ptosis, which are paralysis
or weakness of the eye muscles and drooping of the upper eyelid respectively [45]. In Africa, no
epidemiological studies had been done on MG until 2007 [44]. It is likely that people in Africa
who are affected at young age may grow up without receiving treatment due to a lack of health
facilities as well as the high costs of surgical correction of ptosis.
This paper reviews on a modular and adjustable ptosis crutch which has been developed by the
Medical Devices Laboratory at the University of Cape Town (UCT) in South Africa as a nonsurgical and low-cost solution for elevating the upper eyelid in MG. The ptosis crutch is designed
to meet the specific needs of the MG patient population, particularly those in low income
settings. The application of the solution is not limited to Africa as there appears to be an unmet
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need for a non-surgical solution to elevating the ptotic eyelid in developing as well as developed
countries.
2. Challenges in the treatment of Myasthenia Gravis
Advances during the last century have resulted in various treatments for MG. Cholinesterase
inhibitors are used to retard the degradation of acetylcholine at the neuromuscular junction [46].
There are challenges in the use of cholinesterase inhibitors such as pyridostigmine bromide and
neostigmine [7, 47]. Although pyridostigmine bromide is the most common first treatment and is
considered effective particularly during the early phases of the disease, most patients experience
muscarinic side effects of nausea, abdominal cramping and diarrhoea [7, 34]. Neostigmine is
rarely used because of its poor tolerability and pharmacodynamic profile [7]. Consequently,
cholinesterase inhibitor treatment is inadequate for the vast majority of MG patients, and as a
result, immunosuppressive corticosteroids, particularly prednisone, is prescribed [48]. Although
corticosteroids are inexpensive and rapid-acting drugs for immunomodulation in MG [49], their
use is limited by multiple side effects such as osteoporosis, diabetes mellitus, infection, gastric
ulcer and glaucoma [50].
Thymectomy has been a treatment option for decades to improve MG in younger adults who fail
to respond adequately to immunosuppressive therapy or to minimise adverse effects [51, 52]. It
is a surgical procedure that removes all the thymic tissue to produce lasting remission as the
thymus has been demonstrated to play a role in the development of MG [51, 53]. Thymectomy is
recommended for patients suffering from generalised, early-onset MG and who are positive for
anti-acetylcholine receptor antibodies [49]. There are uncertainties related to thymectomy as the
age of patients who should undergo thymectomy and the timing of the procedure have not been
settled, although most experts restrict the procedure to patients under the age of 65 years [7]. A
number of studies indicate that the sooner after diagnosis the procedure of thymectomy is done,
the greater the benefit [7, 54]..Although various studies have shown that adverse effects are not
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common with thymectomy [3, 55, 56, 57], the procedure is expensive as it can cost up to $80,000
[58] and may have operative complications that need to be weighed against benefits [59].
Another surgical method for the treatment of myasthenia blepharoptosis, is the frontalis sling or
suspension procedure which is done by creating a drape from the frontalis muscle to the eyelid
with the aim of transferring the elevating function of the muscle to the ptotic eyelid [60]. It is
recommended for severe cases, particularly for patients who fail to respond to medical treatment
such as acetylcholine esterase inhibitors [61, 62]. However, these surgical options are often out of
reach for patients in developing countries due to costs and lack of facilities.
Patients with contraindications to the use of steroids, immunosuppressive agents or thymectomy
can opt for assistive devices aimed at correcting double vision and ptosis. These include eyelid
supports, occlusive devices, eyeglass prisms, and contact lenses [63, 64, 65]. Eyelid crutches can
be fitted into glasses and tape can be used to elevate the drooping eyelids, while eye patching,
clip-on occluders or frosted lenses can eliminate double vision [66]. Mechanical lid elevation for
eyelid drooping that obscures vision with ptosis crutches or tape is effective and well tolerated
[7]. Although the use of assistive devices is relatively cheap [63, 67], the solutions may be
impractical for some patients. For example, taping the eyelid using dermatologic tape provides a
simple solution for ptosis, but the major drawback is corneal exposure and the need for topical
lubrication [68]. In addition, eyeglass prisms which are used for double vision, positional
correction, or convergence correction are usually not effective because of fluctuation in eye
muscle weakness [66].
3. Ptosis crutches as nonsurgical intervention for Myasthenia Gravis.
A ptosis crutch is a plastic-coated stainless steel wire mounted or soldered onto a spectacle frame
to elevate the eyelids of the patient [69, 70]. It is used as an external device attached to the
patient’s eyeglass frame to mechanically hold the eyelid open [71]. The device is meant to
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overcome the adverse visual effects of ptosis, usually in cases deemed unsuitable for medical or
surgical treatment [72]. Fitting the ptosis crutch is a simple procedure as it is the same as for
regular spectacles in that a frame appropriate for the patient’s facial features or structure is
selected [71]. It is possible to make a custom fit ptosis crutch for each patient with the goal of
creating a gentle mechanical lift of the eyelid(s) without downward or posterior pressure on the
globe [73]. Ptosis crutches have the advantages of being effective, cost-efficient and non-invasive
[8]. Despite the seemingly straight-forward application, the use of ptosis crutches by MG patients
presents challenges. For example, the crutch can prevent the eye from fully closing, causing
ocular surface drying and frequent irritation of the eyes due to decreased normal blinking [68,
71]. In addition, patients using crutch glasses often experience discomfort with the forced
opening of the eye and watering owing to the pressure of the wire loop on the upper lid [74].
Various mechanisms have been developed to overcome the limitations of ptosis crutches.
Magnetic force has been used, by insertion of a magnet into, or its attachment to, the upper
eyelid, and elevation of the eyelid by the action of a small magnet placed behind the upper rim of
a spectacle frame [71, 74]. The attracting force from the magnets pulls the eyelid upwards and
forwards. The use of a magnetic ptosis crutch is a possible solution towards the maintenance of
eye closure as either a volitional or reflexive blink [71, 75]. However, there are problems relating
to the strength of the magnetic field, attachment and adhesion of the lid magnet, as well as the
effects of static magnetic fields [71].
Against this background, researchers from Medical Devices Laboratory at UCT developed a low
cost, modular and adjustable ptosis crutch for use in low resource settings. Although the ptosis
crutch itself is not novel, no evidence could be found of a modular or adjustable ptosis crutch in
the global market [6]. The global trend is for ptosis crutches to be manufactured and fitted on a
case-by-case basis [69, 76, 77]. While this brings the advantage of customised crutches to meet
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the needs of the users, it requires the patient to have access to the appropriate facilities.
4. Modular and Adjustable Ptosis Crutch developed by Medical Devices Laboratory at
UCT
The ptosis crutch that has been developed by Medical Devices Laboratory at UCT provides a
simple and unobtrusive solution to elevating the ptotic eyelid(s) above the visual axis of MG
patients. The design was aided by input from the clinician and the users (MG patients) as shown
in Table 1.
Patient requirements




Elevates the eyelid above the visual axis.
Easily attached to glasses.
Comfortable.
Aesthetically acceptable.
Clinician requirements



No irritation to the skin at the point
of contact.
No drying of the cornea.
Suitable for children, adolescents and
adults.
Table 1: Design requirements for the ptosis crutch [78].
The crutch accommodates unilateral and bilateral ptosis as a crutch can be fitted to either of the
spectacle temples [79]. The crutch is adjustable along the axial, transverse and frontal planes,
thus allowing the patient to fit it to the specific size and position of their eye [6]. This allows the
ptosis crutch to cater for the inter-individual variability of horizontal eye position, globe
projection and eyelid elevation [6, 79]. The crutch is 3D printed using acrylonitrile butadiene
styrene (ABS) with stainless steel wire coated in polyvinyl chloride as tubing material [6]. The
materials do not cause irritation to the eyelid skin and the crutch does not have any known
adverse effects such as drying of the cornea and obstruction to the visual field of the patient [79].
This is the result of the eyelid not being elevated to its original position, but rather only
sufficiently to clear the visual axis. However, no corneal examination was conducted to quantify
dryness.
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The crutch comprises three modular components shown in Figure 1.
Figure 1: An adjustable ptosis crutch comprising three modular components; [A] the crutch bar,
[B] the crutch housing, and [C] the attachment component to the frame of the glasses.
The crutch housing fits a metal arm and is secured to the spectacle temple using a press fit
mechanism [78]. The curved crutch bar makes full contact with the skin at the position of the
eyelid crease and holds the eyelid above the visual axis [6]. The ptosis crutch is customised to fit
spectacle arms with different dimensions [78]. For example, the adjustable components allow the
crutch to fit a globe protrusion from 12 to 21mm and adjust for the upper eyelid position by 5–
10mm measured from the lateral canthus to the border of the arm of the spectacles. The crutch
bar is adjusted to elevate the eyelid 2–5 mm and the crutch is fastened when in the correct
position [6, 78, 79]. Figure 2 displays the ptosis crutch prototype attached to the border of the
spectacle frame.
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Figure 2: The ptosis crutch attached to the spectacle border; [A] front view and [B] top view
The crutch design is modifiable to fit a range of user eye shapes, in that the curvature of the eye
ball is accommodated in standard categories namely small, medium and large, to cater for the
different requirements of the patients.
5. Clinical testing
Functional assessment of the ptosis crutch involved analysing digital photographs of twenty-one
participants’ ptotic eyes under two conditions, that is with and without the ptosis crutch fitted [6,
79]. The ptosis crutch was fitted to a standard spectacle frame for testing to reduce any
confounding influence of the spectacle frame on measurements. The use of the ptosis crutch to
elevate the upper eyelid and improve vision is shown in Figure 3:
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Figure 3: Use of ptosis crutches to elevate drooping eyelids in patients A, B, C and D
A one-way analysis of variance (ANOVA) (p<0.05) revealed significant differences in the
marginal reflex distance (MRD) of the participant’s eyes when unassisted and when wearing the
ptosis crutch. The MRD when wearing the ptosis crutch was 0.86mm (±1.33mm) (above the
pupil centre) compared to -0.83mm (±1.38mm) (below the pupil centre) without, with the pupil
centre located at 0mm. This is a difference in the MRD of 1.69mm (±1.15mm) [ 79].
Initially, patients were given the ptosis crutch for overnight use which was later extended to a
week and three months. The majority of the patients came from remote locations. To reduce the
frequency of travelling to the hospital while ensuring access to the ptosis crutches, each patient
was given 10 sets of crutches to last for 3 months. The patients were provided with basic training
and manuals on how to fit the crutches to the glasses. To keep track of their experiences, the
patients were given assessment sheets to record their experiences.
The functional effectiveness, cost effectiveness and user satisfaction were explored to determine
whether the ptosis crutch could be considered as successful in meeting the needs of the user.
5.1 Functional effectiveness
The effectiveness of the ptosis crutch was measured as the ability of the device to successfully
elevate the upper eyelid to clear the visual axis. The ptosis crutch was effective in elevating the
eyelid to clear the visual axis as indicated in the measurements of the MRD which was 0.86mm
(±1.33mm) when wearing the ptosis crutch and -0.83mm (±1.38mm) without [79]. Different
eyeball radii were accommodated by a set of pre-defined crutch sizes.
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5.2 Cost effectiveness
The cost effectiveness of the ptosis crutch was measured in terms of the use of resources with
reference to the materials and manufacturing methods. The ptosis crutch cost 0.9 USD to
manufacture, which is remarkably lower than the cost of the existing devices on the market,
which range from 30-100 USD [6, 79]. However, some of the crutches were fragile and broke
after a few days. The crutches were made of acrylonitrile butadiene styrene plastic which is not
strong under tensile stress but was chosen due to its low cost and local availability [78]. Moulded
plastic could be used to make the crutches durable, but at high cost. The producers of the
technology took a deliberate decision in favour of 3D printing of the device for ease of access.
5.3 User satisfaction
The user satisfaction focused on the user’s subjective experience of the ptosis crutch in terms of
comfort and ease of use. A total 14 participants were assessed after spending between a day and
week using the crutches and they indicated that they experienced improved vision and felt
comfortable. They expressed interest in using the device on a long-term basis. After using the
device for a period of between a month and three months, user satisfaction was mixed as shown
in Table 2 [unpublished data].
Number of participants
Participant experience
8
Comfortable using the crutch when reading.
2
Not comfortable wearing the ptosis crutch regularly.
4
Found the crutches useful, but did not continue using them due to
breakage.
Table 2: Assessment of user satisfaction with the ptosis crutch [unpublished data].
6. Advantages and disadvantages of the modular ptosis crutch
The ptosis crutch which has been developed by the Medical Devices Laboratory at UCT is
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advantageous in a number of ways.
1. It is relatively cheap as it costs about 0.9 USD or 90 USD cents to produce [79]. This is
considerably lower than the cost of existing devices, which ranges between 30 and 100
USD [67, 80].
2. Although the ptosis crutch does not restore the functionality of the muscles involved in
eyelid elevation, it acts as an aid to manually elevate the eyelid in order to improve vision
[6]. The crutch does not elevate the upper eyelid to a normal anatomic position, but is able
to lift to a position that is just enough to clear the visual axis
3. The ptosis crutch, by virtue of being made of a combination of ABS and galvanized wire
covered in PVC tubing, allows for good skin-crutch coupling and does not cause skin
irritation [6, 79]. Conventional ptosis crutches, which are manufactured using metal wire
[81] (stainless steel, bronze, gold or copper-aluminium) or nylon, tend to exert pressure
on the globe, resulting in double vision as well as skin irritation at the site of crutch-eyelid
contact.
4. The housing of the crutch is flexible in that it can be customised to fit the frames of
glasses with different dimensions [78]. The crutches that have been developed thus far are
manufactured for patients on a case-by-case basis [79]. Finding an optician who can
dependably craft spectacle frames with crutches and then adjust them correctly for the
individual patient can be difficult [81]. Providing the patient with the ability to fit and
adjust the crutch to their spectacles themselves has the advantage of the patient not
needing to visit facilities that specialise in making and fitting ptosis crutches.
5. The ptosis crutch is being released as an open source innovation. This is meant to ensure
that it is easily accessible, thus allowing ptosis patients or interested institutions to
download the ptosis crutch stereolithography file free of charge [79]. This means that
anyone with access to a 3D printer would be able to print a crutch after downloading the
design files. Furthermore, design improvements may be made by anyone who has an
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interest in the crutch.
The ptosis crutch has limitations:
1. The ptosis crutch is dependent on a facility that has 3D printing. In developing countries,
such facilities are lacking, hence access to the device may be limited.
2. The ptosis crutch does not open the eyelid fully but elevates it in such a way that that the
visual axis is cleared. Aesthetically, the patient will continue to have drooping eyes but
technically the vision is improved.
3. The current design results in some breakage, but the open sharing of the design enables
improvements.
7. Expert commentary
The modular and adjustable ptosis crutch developed by the Medical Device Laboratory at UCT is
a non-surgical and low-cost solution for elevating the upper eyelid in MG patients. It could
change the landscape in the treatment of not only MG, but also other clinical conditions that
require elevation of the eyelid if the problems of usability are addressed. The crutch shows
potential to provide a simple, effective and unobtrusive solution to elevate the drooping upper
eyelid(s) above the visual axis of ocular MG patients without the need for surgery and
medication. The inventors provide information on the procedures and downloadable files for the
3D printing so that a medical practitioner can facilitate the printing of the devices for patients as
required. This is a novel technology transfer model in South Africa for a 3D printed medical
device. The open source innovation platform makes the ptosis crutch easily accessible globally
and this is a crucial step in providing opportunities for further open innovation to address the
limitations of the device. Through the release of the device into the public domain, researchers
interested in the technology can contribute towards improving the device to provide access to an
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affordable alternative to surgery for patients in low-resource settings.
8. Five-year review
The modular and adjustable ptosis crutch has the potential to become the first line treatment for
myasthenia gravis and other similar clinical cases in the near future, particularly in settings such
as Africa where the disease has been neglected and surgical correction of ptosis is beyond the
reach of many patients due to the costs and unavailability of facilities. The low cost of the device
is likely to improve the treatment of myasthenia gravis in developing countries, which will have
the impact of raising public awareness and making the disease socially acceptable.
Free availability of the ptosis crutch as an open source innovation provides opportunities for
further research, development, and improvement, and the ptosis crutch is likely to evolve with the
evolution of 3D printing technology.
9. Key issues

Medicines for treating MG such as cholinesterase inhibitors and corticosteroids are
available but their use is limited due to side effects, while thymectomy, a surgical
solution, is beyond the reach of many patients in developing countries.

The ptosis crutches that are available on the market present challenges such as interfering
with the closure of the eye, which causes ocular surface drying and frequent irritation of
the eyes.

The open-access, modular and adjustable ptosis crutch developed in the Medical Device
Laboratory at UCT provides opportunities for further open innovation to address the
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limitations of the device.

The facility for adjustment along axial, transverse and frontal planes caters for interindividual variability in horizontal eye position, globe projection and eyelid elevation
without causing irritation to the eyelid skin, drying of the cornea, and obstruction to the
visual field.
Legends of figures and tables
Figure 1: An adjustable ptosis crutch comprising three modular components; [A] the crutch
bar, [B] the crutch housing, and [C] the attachment component to the frame of the glasses.
Figure 2: The ptosis crutch attached to the spectacle border; [A] front view and [B] top view
Figure 3: Use of ptosis crutches to elevate drooping eyelids in patients A, B, C and D
Table 1: Design requirements for the ptosis crutch [78].
Table 2: Assessment of user satisfaction with the ptosis crutch [unpublished data].
Funding
This paper was based on research supported by the South African Research Chairs Initiative of the
Department of Science and Technology and the National Research Foundation of South Africa (Grant
no. 98788).
Declaration of interest
The authors have no other relevant affiliations or financial involvement with any organization or
entity with a financial interest in or financial conflict with the subject matter or materials discussed in
the manuscript apart from those disclosed. Peer reviewers on this manuscript have no relevant
financial or other relationships to disclose.
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*The article gives a good background of Myasthenia Gravis and explains the use of ptosis
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Ptosis crutch open source instructions
The ptosis crutch device has been made available as an open source file for your (the users)
convenience. The ptosis crutch can be downloaded and easily assembled using the step-bystep instructions outlined below.
Instructions
1. Download the STL and SLDWRKS files within this folder.
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2. Locate your closest 3-D printing facility (it is often easiest to find the closest 3D
printing institution using a Google search).
3. Measure the height and width of the superior border of your spectacle frame
[Figure 1].
A
B
Figure 1: Illustration of the height [A] and the width [B] measurements.
4. If you have got access to the SolidWorks software, alter the dimensions of the
attachment component to 0.1mm larger than the dimensions of your spectacle frame,
that were measured in step 3.
5. If you do not have access to the SolidWorks software, ask an assistant at the 3D
printing institution to alter the dimensions of the attachment component to 0.1mm larger
than the dimensions of your spectacle frame, that were measured in step 3.
6. Determine whether the aperture of the eye is upward or downward sloping
[Figure 2].
A
B
7. Select the crutch bar for the ptotic eye with the suitable slant for the user’s
aperture [Figure 3].
A
B
C
B
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Figure 3: Models of the crutch bar for the left and the right eyes. A] Left eye upward sloping aperture, B] Left
eye downward sloping aperture, C] Right eye upward sloping aperture, D] Right eye downward sloping
aperture.
8. You are now ready to 3D print the three components of the ptosis crutch. Print the
components using ABS as the chosen material.
9. Sand down the 3D printed component to remove the roughly printed edges
10. Place the 3D printed components in an acetone chamber with 45 ml of acetone
[Figure 4]. The control and the crutch bar should be placed in the chamber for 20
minutes while the attachment component should only be inserted for 10 minutes.
The acetone vapour based smoothing provides the ABS with a smooth and glossy
finish.
11. Mould a piece of 1.5mm galvanized wire to a curved shape [Figure 4] with the
dimensions given below:
RoC: 12.7mm
Height of curve: 4.87mm Width:
24mm
h
Figure 4: Curved shape of the galvanized wire.
12. Cut a 5cm length of PVC tubing with a bore of 2mm.
13. Thread the curved wire through the PVC tubing [Figure 5].
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Figure 5: Curved galvanized wire being threaded through the PVC tubing.
14. Thread the PVC tubing, containing the wire bar, through the cylindrical
openings in the crutch bar housing unit [Figure 6].
Figure 6: PVC tubing inserted into the ABS crutch bar.
15. Snip the PVC tubing at the edge of the crutch bar housing unit [Figure 7].
Figure 7: PVC tubing being cut to size, when threaded through the cylindrical openings n the ABS crutch bar.
16. Remove the 2mm tip of a stainless steel nail (2mm diameter), using wire cutters
[Figure 8].
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Review
Figure 8: Tip of a 2mm nail being removed, using a clamp to secure the nail and plyers to remove the tip of nail.
17. Insert the nail tips into the PVC tube opening and push them into the bore of
the tube [Figure 9]. The purpose of the nail tips is to secure the PVC tubing
within the housing unit.
Figure 9: Nail tips inserted into the PVC tubing to secure the tubing in place.
18. Clip the attachment component onto the superior border of the spectacle frame.
The component should fit securely on the spectacle frame.
19. Insert the control component into the slot on the attachment.
20. Insert the crutch bar into the slot on the control
21. Fit the spectacles to the nasal bridge.
28
Review
22. Adjust the crutch bar along the y axis to comfortably fit on the upper eyelid.
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23. Elevate the eyelid to clear the visual axis using the vertical lever.
29