Microcurrent stimulation in the treatment of dry and wet macular degeneration
Laurie Chaikin1
Kellen Kashiwa2
Michael Bennet2
George Papastergiou3
Walter Gregory4
1
Private practice, Alameda, CA,
USA; 2
Retina Institute of Hawaii,
Honolulu, HI, USA; 3
California Retinal
Associates, San Diego, CA, USA; 4
Clinical Trials Research Unit, Faculty
of Medicine and Health, University of
Leeds, Leeds, UK
Purpose: To determine the safety and efficacy of the application of transcutaneous
(transpalpebral) microcurrent stimulation to slow progression of dry and wet macular degeneration or improve vision in dry and wet macular degeneration.
Methods: Seventeen patients aged between 67 and 95 years with an average age of 83 years
were selected to participate in the study over a period of 3 months in two eye care centers.
There were 25 eyes with dry age-related macular degeneration (DAMD) and six eyes with wet
age-related macular degeneration (WAMD). Frequency-specific microcurrent stimulation was
applied in a transpalpebral manner, using two programmable dual channel microcurrent units
delivering pulsed microcurrent at 150 MA for 35 minutes once a week. The frequency pairs
selected were based on targeting tissues, which are typically affected by the disease combined
with frequencies that target disease processes. Early Treatment Diabetic Retinopathy Study or
Snellen visual acuity (VA) was measured before and after each treatment session. All treatment
was administered in a clinical setting.
Results: Significant increases were seen in VA in DAMD (P 0.012, Wilcoxon one-sample
test), but in WAMD, improvements did not reach statistical significance (P 0.059). In DAMD
eyes, twice as many patients showed increase in VA (52%) compared to those showing deterioration (26%), with improvements being often sizeable, whereas deteriorations were usually
very slight. In WAMD eyes, five of six (83%) patients showed an increase and none showed
deterioration.
Conclusion: The substantial changes observed over this period, combined with continued
improvement for patients who continued treatment once a month, are encouraging for future
studies. The changes observed indicate the potential efficacy of microcurrent to delay degeneration and possibly improve age-related macular degeneration, both wet and dry. However, this
study has no control arm, so results should be treated with caution. Randomized double-blind
controlled studies are needed to determine long-term effects.
Keywords: microcurrent, macular degeneration, transpalpebral, transcutaneous, retinal
disease
Introduction
Low-intensity micro-amperage current has been applied to retinal conditions for several
decades under various circumstances. Henry Dor, MD, an ophthalmologist in Germany,
used electrical currents to help individuals with amblyopia, retinochoroiditis, glaucoma, and optic atrophy in 1873.1
In a summary paper by Gekeler and Bartz-Schmidt,
subthreshold visual stimulation in inactive retinal implants leading to improvements in
residual areas of vision was stated to be the result of a release of neurotrophic factors.2
Twenty peer-reviewed publications in PubMed over the last 5 years reflect renewed
interest in microcurrent therapy.3
Since then, transcorneal electrical stimulation (TES)
and transpalpebral electrical stimulation (TPES) placement of the electrodes over the
Correspondence: Laurie Chaikin
Private practice, 420 F Cola Ballena
Alameda, CA 94501, USA
Tel 1 510 693 8053
Fax 1 510 995 8376
Email [email protected]
Journal name: Clinical Ophthalmology
Article Designation: Original Research
Year: 2015
Volume: 9
Running head verso: Chaikin et al
Running head recto: Microcurrent stimulation for macular degeneration treatment
DOI: http://dx.doi.org/10.2147/OPTH.S92296
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Chaikin et al
closed lid has been used. A study by Shinoda et al in 2008
applied this approach to 16 patients with wet age-related
macular degeneration (WAMD) and to five with dry agerelated macular degeneration (DAMD). They used four
frequencies of 290 Hz, 31 Hz, 8.9 Hz, and 28 Hz delivered
via a monophasic pulse at 800 MA. Subjects with both
WAMD and DAMD showed statistically significant log of
the minimum angle of resolution (logMAR) improvements,
from 29.5 logMAR units to 31.8 logMAR units (WAMD,
P 0.04) and from 39.8 logMAR units to 42.9 logMAR
units (DAMD, P 0.04), comparing pre- and 4-week posttreatment results.3
In 2013, Anastassiou published results
from a randomized placebo-controlled exploratory trial
with 22 patients using a TPES approach with variable frequencies of 5–80 Hz at 150–220 MA twice a day treatment
to eight spots around the eyes for 40 seconds per spot for
1 week. At the end of the week, they found that seven out
of 12 patients had an improvement in visual acuity (VA)
of more than five letters (P 0.001). Similarly contrast
sensitivity improved with an increase of 4.4 optotypes
(P 0.006). Placebo controls had no statistically significant
change in VA.4
Basic research both in vitro and in vivo demonstrating the safety and neuroprotective effects of electrical
current stimulation has been done in a number of areas.
Motor axonal regeneration, sensory nerve regeneration,
and growth-associated gene expression were found to be
significantly enhanced by brief periods of micro-amperage
stimulation.5
Increased survival of retinal ganglion cells in
rats following crushed optic nerve as well as significant delay
of posttraumatic cell death was described.6,7 Increased visual
evoked potential amplitude following optic nerve crush
(early stage).5
Electroretinogram measurements showed
amelioration of progressive photoreceptor degeneration
following light-induced retinal damage,8
as well as neuroprotection through proinflammatory effects.9
Alteration
in gene expression was demonstrated, where close to 500
transcriptome changes were measured and included potentially neuroprotective genes as well as genes that moderate
the expression of tumor necrosis factor (TNF).10 Retinal
photoreceptor protective effects were demonstrated in rhodopsin P347L-deficient rabbits via electroretinogram,11 as
well as neuroprotection from ischemic damage.12 Increase
in cerebral blood flow in rats following TES of trigeminal
afferents even after being subjected to subarachnoid hemorrhage induced vasospasm.13 In all human studies, there were
no adverse effects aside from short-term corneal irritation
from the contact electrode and, in most cases, there were
notable and sometimes significant improvements in vision.
All studies were small; some had sham controls. Effective
use of TES for eye conditions included nonarteritic ischemic
neuropathy,14 branch retinal vein occlusion,15 Stargardt’s
disease,16 retinitis pigmentosa,17 and Best vitelliform retinopathy.18 Frequency-specific microcurrent (FSM) has been
used extensively in the field of physical medicine and rehabilitation for pain relief and accelerating tissue recovery.19
This approach proposes that it is not only the microcurrents
that have a positive effect on biological tissue but also the
frequencies themselves. Frequencies are delivered via a
square-wave pulse train. Square-wave pulse trains contain
a wide range of harmonics, which can stimulate a resonance
effect in target tissues. One well-known resonance effect is
in sound acoustics breaking down the binding of lead atoms
in crystal glass enabling it to shatter. In tissue pathology,
the resonance could potentially break molecular bonds
responsible for inflammation. For example, an animal model
was used to test the anti-inflammatory effect in the immune
system.20 Arachidonic acid was painted on mouse ears to
create inflammation. The frequency combination of 40 Hz
and 116 Hz for inflammation in the immune system was
run through the ears immediately afterward, and ear thickness measurements were made after treatment. In the sham
treatment, a different frequency combination of 40 Hz/0 Hz
was run, and the results were measured. The treatment group
showed a 62% reduction of lipoxygenase-mediated inflammation and 30% reduction of cyclooxygenase-mediated
inflammation at 4 minutes, while the sham group showed
no change. Treated ear thickness reduc
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Microcurrent stimulation for macular degeneration treatment
Methods
Seventeen patients aged between 67 and 95 years with an average age of 82.9 years were tested and treated in two eye care
centers located at the Retina Institute of Hawaii in Honolulu
and a private practice in Castro Valley, CA, USA. There were
25 eyes with DAMD and six eyes with WAMD. All patients
were screened for inclusion after providing written informed
consent. The research followed the tenants of the Declaration
of Helsinki, and an independent review board application was
completed and approved by Sterling Independent Review
Board (Atlanta, GA, USA) prior to subject selection. The trial
was registered with number NCT01790958.
Inclusion criterion were 50 years of age or older,
male and female, history of retinal disease involvement, no
antivascular endothelial growth factor treatments for at least
3 months prior to the study, and no new antioxidant/vitamin
supplementation for at least 6 months prior to the study.
Subjects with WAMD were placed in the study only after
they were medically cleared as having no active bleeding.
Exclusion criteria included a history of noncompliance with
regular medical visits, significant media opacities that might
interfere with assessing VA, presence of pigment epithelial
tears or rips, diabetic retinopathy, any known serious allergies
to fluorescein dye, presence of retinal neovascularization, or
any treatment with investigation agents in the past 30 days.
Screening procedures included best-corrected VA (VA
determined by staff low vision optometrist), ophthalmic
examination, intraocular pressure measurement, fluorescein
angiography, fundus photography, and OCT per standard of
care; these tests were performed no earlier than 14 days prior
to initiation of the treatment and were performed by qualified
personnel. Qualified personnel consisted of licensed low vision
optometrists, ophthalmic technicians, and ophthalmologists.
After initial screening, patients returned for regular clinic
examinations and diagnostic testing per standard of care.
These visits were conducted depending on the type and
severity of the retinal disease condition per standard of care.
Vitals (blood pressure, weight, and pulse), VA, intraocular
pressure measurements, OCT, and dilated eye examinations
were performed per standard of care. Fundus photos, fluorescein angiograms, and microperimetry were obtained based
on standard of care and severity of disease.
In some cases, VA was measured using Snellen acuity,
which then was converted to the logMAR scores. In the cases
of count fingers, hand motion, light perception, or no light perception, the following convention was used: count fingers 1.6,
hand motion 2.0, light perception 2.5, and no light perception 3.0 logMAR units, as described by Cohen et al.23 Because
treatment intervals varied slightly from patient to patient, and
patients were followed-up for varying lengths of time, in order
to calculate mean logMAR changes over time it was necessary
both to interpolate logMAR values between one time point and
the next, and to make assumptions about the pattern of logMAR
results beyond the longest follow-up time for each patient. It
was therefore assumed that changes from one time point to the
next followed a linear pattern. In this way, it was possible to
derive an imputed logMAR score for every day from the start
of treatment for each patient. The so-called linear increment
method was then used to extrapolate beyond the follow-up of an
individual patient.24 This method involves projecting the pattern
of change for the individual patient beyond their own follow-up
by allowing each individual’s values to follow the overall pattern
of the whole cohort from day-to-day.24 Thus, the mean values
are not compromised by dropouts. The standard error (SE) of the
mean and, therefore, the confidence interval (CI) on the mean
are based on the number of actual values at that time point; the
values carried forward are used in calculating the mean, but not
the SE. This method is used in Figures 3 and 4.
To evaluate the significance of overall changes in VA
over time, the overall difference in the letter count was
calculated for each patient and the significance of these differences was evaluated using the Wilcoxon one-sample test
(Wilcoxon signed-rank sum test); if differences were random,
the median of these values was expected to be 0.
FSM stimulation was applied in a transpalpebral manner, with flat carbon electrodes placed into chamois-type
fabric, which was moistened with water and placed over
the closed eyes; another electrode was placed at the base of
the skull (Figure 1). Two small dual channel programmable
Figure 1 Patient receiving microcurrent treatment.
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Chaikin et al
is significant change in VA scores in DAMD (P 0.012,
Wilcoxon one-sample test). In WAMD, changes did not
reach statistical significance (P 0.059). With only six values,
all six WAMD eyes would have had to show improvements
for this result to be significant, whereas, in fact, five eyes
showed improvement and one showed no change. In DAMD
eyes, twice as many patients showed a positive trend (52%)
compared to those showing deterioration (26%), and the
changes were often sizeable, whereas deteriorations were
usually very slight (Figures 1 and 5). In WAMD eyes, five
of six (83%) patients again showed a positive trend, while
none showed deterioration.
Table 1 VA results for dry AMD
Eye no Pretreatment VA Posttreatment VA
1 20/40 20/20
2 20/50 20/25 2
3 20/200 20/200
4 HM 1` HM 1`
5 20/800 20/640
6 20/320 20/160
7 20/125 20/63
8 20/25 20/30
9 20/80 20/80
10 20/200 20/80
11 20/20 20/20
12 20/40 20/32
13 20/100 20/70
14 CF at 4` CF at 4`
15 20/50 20/50
16 20/200 20/200
17 20/60 20/50
18 20/100 20/30
19 20/250 20/50
20 20/80 20/60
21 20/125 20/125–
22 20/60 20/50
23 20/400 20/160
24 20/800 20/800
25 20/1,000 20/1,000
Abbreviations: AMD, age-related macular degeneration; CF, count fngers;
HM, hand motion; VA, visual acuity.
microcurrent units utilizing a direct current source (Custom
Care Manufacturing Microcurrent Technologies, Seattle,
WA, USA, and Precision Distributing, Vancouver, WA,
USA) were programmed with the FSM protocol. The treatment time was 35 minutes, and all treatments were administered in a clinical setting. The frequency pairs selected
were based on targeting tissues, which are typically affected
by the disease and combining with frequencies that target
disease processes. For example frequencies pairs included
40 Hz with 95 Hz for inflammation in the retina and macula
(137 Hz), scarring and inflammation in the arteries, veins,
capillaries, and retina (3 Hz and 13 Hz with 62 Hz, 79 Hz,
162 Hz, and 95 Hz) among others. Current was delivered at
150 MA, and frequency was delivered via a ramped squarewave pulse train. Early Treatment Diabetic Retinopathy
Study or Snellen VA was measured before and after each
treatment session, and subjective responses were recorded.
Number of treatments was determined by condition severity
and patient response. The number of treatments ranged from
2 to 10, with an average of 4.8 sessions.
Results
Tables 1 and 2 show the VA scores before and after treatment.
Absolute logMAR changes from the baseline values over
the first 3 months are shown for DAMD and WAMD eyes
in Figures 2 and 3, respectively. The no-change line is added
for reference. Many eyes show an initial sharp logMAR
drop, with a few patients showing no improvement or a very
slight deterioration. Overall mean changes over time with
95% CI on these means are shown for dry and wet eyes in
Figures 4 and 5, respectively, using the approach described
in the “Methods” section. For these mean changes, similar
patterns are observed in both eyes, with a sharp fall, indicating improvement in VA, seen over approximately the first
week or so, and continuing improvement throughout the first
month. Subsequently, the logMAR scores appear to level off.
There may be some slight deterioration in the next 2 months;
though numbers become small, the CIs are wide. The upper
95% CIs on these means are consistently well below 0, indicating a highly statistically significant effect, which begins
almost immediately. Choosing to compare logMAR values
at 21 days, since only two WAMD eyes have follow-up
at 30 days, whereas all six have follow-up at 21 days, the
21-day logMAR mean was 3.8 SEs below 0 in DAMD eyes
(P 0.0001) and 3.9 SEs below 0 in WAMD eyes (P 0.0001),
a very similar order of magnitude of effect.
The histograms in Figures 6 and 7 show the mean
letter changes from baseline to final visit by eye. There
Table 2 VA results for wet AMD
Eye no Pretreatment VA Posttreatment VA
1 20/160 1 20/100 1
2 20/200 20/80
3 20/60 20/60
4 20/70 20/50
5 20/1,000 20/800
6 20/100 20/80
Abbreviations: AMD, age-related macular degeneration; VA, visual acuity.
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Microcurrent stimulation for macular degeneration treatment
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Figure 2 Dry AMD eyes: absolute logMAR differences from starting values for each
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Notes: Each color represents a different eye. There is an additional dotted axis
line drawn at 0.
Abbreviations: AMD, age-related macular degeneration; logMAR, log of the
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Figure 3 Wet AMD eyes: absolute logMAR differences from starting values for each
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Abbreviations: AMD, age-related macular degeneration; logMAR, log of the
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Figure 4 Dry AMD eyes: mean absolute logMAR differences from starting values
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Abbreviations: AMD, age-related macular degeneration; logMAR, log of the
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Figure 5 Wet AMD eyes: mean absolute logMAR differences from starting values
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Abbreviations: AMD, age-related macular degeneration; logMAR, log of the
minimum angle of resolution.
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Figure 7 Wet AMD eyes: total letter change.
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Abbreviation: AMD, age-related macular degeneration.
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Chaikin et al
Of the patients who had microperimetry testing done, there
was an overall increased retinal sensitivity across the board
following microcurrent stimulation (Figures 8 and 9). Some
patients, however, with large areas of geographic atrophy
tended to increase their sensitivity in areas of their preferred
retinal locus, where others with smaller to no areas of geographic atrophy increased their sensitivity in their fovea. There
were no changes in retinal thickness measured by OCT.
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Figure 8 Pre- and post-microperimetry felds on three patients.
Notes: MP-1 felds of patient 16: (A) pretreatment, (B) following two treatments, and (C) after fve treatments at 6 months.
Abbreviation: MP-1, microperimeter-1.
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Microcurrent stimulation for macular degeneration treatment
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Figure 9 Pre- and post-microperimtery felds on two patients.
Notes: MP-1 felds of patient 17: (A) pretreatment and (B) posttreatment after three treatments.
Abbreviation: MP-1, microperimeter-1.
Discussion
In this study, dual channel FSM therapy was used in a noninvasive procedure, involving transcutaneous electrical current
with very low intensity. Clinically, if further studies support
positive trends over time, this would be a relatively easy treatment modality for physicians to offer their patients, either
as a weekly in-office treatment or a home-based therapy.
Interested clinicians would benefit from a course, such as
the one available at www.frequencyspecific.com.
Mechanisms of possible tissue effects that may explain
some of the changes in visual function by FSM are theoretical. No direct measures of tissue changes were taken. Many
of the following hypotheses are derived from animal models
using TES:
u Effects on the mitochondrial Krebs cycle increase production of intracellular adenosine triphosphate. Transmembrane transport through voltage-gated ion channels is
dependent on adenosine triphosphate. Voltage-gated ion
channels may be positively influenced by the presence of
external current flow, enabling the configuration change
that precedes ion flow.19
u Influence of extremely low-frequency electromagnetic
fields has been demonstrated to have beneficial and
therapeutic effects on voltage-gated calcium channel
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Chaikin et al
via influence on the G-protein channel through the nitric
oxide-cyclic GMP–protein kinase pathway.25
u Alteration in gene expression, such as upregulation of Bcl-2,
ciliary neurotrophic factor, and brain-derived neurotrophic
factor; downregulation of Bax; suppression or inhibition
of inflammatory factors, such as IL-1B and TNF-A; and
transcriptome changes in 490 genes have been identified,
including neuroprotective genes, such as Bax or those that
are part of the TNF family. Additionally, upregulation of
intrinsic insulin-like growth factor-1 (Mueller cell activation and diffusion into the inner retina) was found.9,10
u Increase in choroidal vessel blood flow in normal human
subjects, measured in ten healthy subjects following
TES using a laser speckle flowgraphy, showed that there
was statistically significant increase in blood flow in the
macular zone, which may account for the improvements
in patients with ischemia.26
Although, the majority of the patients demonstrated both
subjective and objective improvements, follow-up is still
relatively short and determination of long-term efficacy is
as yet unproven. Further, the training effects of repeated VA
measures are unknown and the VA testers were not blinded,
adding the possibility of examiner bias. The magnitude of
changes in VA in this patient population was similar to that
seen by Shinoda et al3
and perhaps less than that reported by
Anastassiou, although follow-up was extremely short in the
latter study. It is unclear whether and to what degree early
improvements were subsequently abrogated in this group of
patients, since follow-up varied considerably from patient to
patient. However, those patients who continued treatment
once a month, for at least 6 months, maintained their VA
gains. There was sufficient follow-up to enable mean changes
over time to be determined, as in Figures 3 and 4, for at least
the first 30 days. The substantial changes observed over this
period, combined with continued improvement for patients
who continued treatment once a month, are encouraging for
future studies, which could be made double-blind by including a control arm with sham treatment.
It is likely that patients would need to continue treatment
for the duration of their lives, since the natural course of
disease progression for age-related macular degeneration is
a steady loss of vision. In the case of DAMD, there is a slow
steady decline over what could be a long period (10 years or
more), with the possibility of geographic atrophy occurring
in a steady but more rapid decline with complete loss of
central vision. In the case of WAMD, there is rapid precipitous loss of vision over a very short (days to months) time
if left untreated. This efficacy and safety study suggests that
microcurrent stimulation can be safely administered to this
population.
Disclosure
None of the authors have any financial interest in the equipment used, and report no conflicts of interest in this work.
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