Original Article

Levodopa Plus Occlusion Therapy versus Occlusion
Therapy Alone for Children with Anisometropic

Amblyopia

Majid Farvardin1, MD; Mohammad Reza Khalili1, MD; Mehdi Behnia2, MD

1Poostchi Ophthalmology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
2Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran

ORCID:
Majid Farvardin: https://orcid.org/0000-0001-9047-0329

Abstract

Purpose: This study aimed to compare the effects of short-term administration of levodopa plus occlusion
therapy versus occlusion therapy alone in preschool children with hyperopic anisometropic amblyopia.
Methods: This comparative interventional study included 40 eligible preschool children aged 6 to 7 years
with hyperopic anisometropic amblyopia. The primary outcome measure was the logarithm of the minimum
angle of resolution (logMAR) best-corrected visual acuity recorded at baseline, 3 weeks after the treatment
initiation and 12 weeks after the treatment termination. The results were compared between the two groups.
Results: No statistically significant intergroup difference was observed in baseline logMAR visual acuities
(P = 0.92). The mean logMAR visual acuities of the amblyopic eyes were significantly better in both groups
three weeks after the treatment initiation than the baseline (P < 0.01 in both groups). At 12 weeks after
treatment termination, the logMAR visual acuities of the amblyopic eyes were significantly better than the
baseline values (P < 0.001 in the placebo group and P = 0.09 in the levodopa group). Intergroup comparisons
revealed no statistically significant difference in visual acuities 3 weeks after the treatment initiation (P = 0.11)
and 12 weeks after the treatment termination (P=0.10). Twelve weeks after the treatment termination, visual
acuities regressed 0.037 logMAR in the placebo group and 0.042 logMAR in the levodopa group. These
regression rates were not significantly different (P = 0.89).
Conclusion: The results of this study provide evidence that adding short-term administration of levodopa
to occlusion therapy in hyperopic anisometropic amblyopia offers no additional benefit in visual outcomes
and provides no advantage in terms of the regression rate.

Keywords: Amblyopia; Anisometropic; Levodopa; Occlusion Therapy

J Ophthalmic Vis Res 2019; 14 (4): 457–464

Correspondence to:

Majid Farvardin, MD. Poostchi Ophthalmology Research
Center, Shiraz University of Medical Sciences, Shiraz
71349, Iran.
E-mail: majidfarvardinjahromi@gmail.com

Received: 17-10-2018 Accepted: 09-04-2019

Access this article online

Website:
https://knepublishing.com/index.php/JOVR

DOI:
10.18502/jovr.v14i4.5451

INTRODUCTION

For more than 200 years, the standard treatment
for amblyopia has been occlusion of the domi-
nant eye.[1] However, noncompliance is common

This is an open access journal, and articles are distributed under the terms of
the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which
allows others to remix, tweak, and build upon the work non-commercially, as
long as appropriate credit is given and the new creations are licensed under the
identical terms.

How to cite this article: Farvardin M, Khalili MR, Behnia M. Levodopa for
Children with Anisometropic Amblyopia. J Ophthalmic Vis Res 2019;14:457–
464.

© 2019 J  O  V R | PUBLISHED BY KNOWLEDGE E 457

http://crossmark.crossref.org/dialog/?doi=10.18502/jovr.v14i4.5451&domain=pdf&date_stamp=2019-07-17
https://knepublishing.com/index.php/JOVR


Levodopa for Anisometropic Amblyopia; Farvardin et al

because of cosmetic dissatisfaction and interfer-
ence of occlusion with daily activities.[2, 3] There-
fore, developing a treatment modality for ambly-
opia with improved efficacy, shorter duration, and
better compliance has been a research goal. In
the past years, several studies have evaluated the
effects of levodopa on visual function in children
with amblyopia.[4–12] Levodopa is a precursor of
dopamine, a neurotransmitter in the brain and
retina. The effects of dopamine in the management
of amblyopia are explained by its neuromodulator
and neurotransmitter roles in the retina and cen-
tral visual pathway. Studies have suggested that
increased dopamine levels lead to a reduction in
the size of the receptive field in the retina, thereby
improving visual function.[8, 9, 13] In addition, studies
have hypothesized that increased dopamine lev-
els reduce the size of the suppression scotoma.
Measurement via functional magnetic resonance
imaging has shown that dopamine changes the
volume of cortical activation even after a single-
dose administration.[14, 15]

Peripheral decarboxylase inhibitors, such as car-
bidopa or benserazide, prevent the breakdown
of levodopa at peripheral sites and allow more
levodopa to cross the blood–brain barrier, where
it can have central effects.[16, 17] Several studies on
the influence of levodopa on visual function in
amblyopia have used levodopa without occlusion
of the dominant eye,[4, 7, 8] whereas some stud-
ies have combined levodopa with occlusion of
the dominant eye.[5, 6, 10–12] The results of studies
comparing the effects of levodopa plus occlusion
therapy and occlusion therapy alone in amblyopia
are controversial, and a debate persists whether
augmenting occlusion therapy with a pharmaco-
logic agent such as levodopa could affect the man-
agement of patients with amblyopia. In a single-
dose study, and in another three-week longitudinal
study, Leguire et al demonstrated that levodopa
combined with occlusion improved the visual acuity
in children with amblyopia to a greater extent than
did placebo combined with occlusion.[5, 6] How-
ever, in children with anisometropic and strabismic
amblyopia, Bhartiya et al showed that levodopa
supplementation has no additional benefit over
occlusion therapy alone.[12]

Therefore, the present study aimed to assess
the effectiveness of short-term administration of
levodopa combined with standard occlusion treat-
ment on the visual acuities of preschool children

with hyperopic anisometropic amblyopia, and to
compare it to that of occlusion therapy alone.

METHODS

Study Design and Participants

In this comparative interventional study, we
included 40 eligible patients with hyperopic
anisometropic amblyopia. The patients were
preschool children aged 6 to 7 years with
amblyopia caused by hyperopic anisometropia
[Table 1 and Figure 1]. All patients were selected
among the preschool children referred from the
national amblyopia screening program to our
strabismus and pediatric ophthalmology clinic
affiliated to the Shiraz University of Medical
Sciences because of decreased visual acuity.
The inclusion criteria were as follows: patients
with hyperopic anisometropia (with more than 1.5
diopters of difference between the two eyes) and
the logarithm of the minimum angle of resolution
(logMAR) best-corrected visual acuity (BCVA)
worse than 0.2 log-unit in the amblyopic eye or
at least a 2-line difference in BCVA between the
two eyes. The eye with worse BCVA was included
in the study. At an alpha level of 0.05, 18 patients
were required in each group to find a difference
of 0.1 logMAR visual acuity between the treatment
and placebo groups. Considering a 10% possibility
of non-adherence, 40 patients were included.

Patients with strabismic amblyopia, other types
of anisometropic amblyopia and deprivation ambly-
opia, and patients with a history of previous ambly-
opia therapy were excluded from the study. We
also excluded patients with neurologic and cog-
nitive disorders, including cerebral palsy, autism
spectrum disorders, and attention deficit hyper-
active disorder, as well as those with any sys-
temic disorders such as diabetes, thyroid disease,
and rheumatologic disease. Eyes with a history
or objective sign of trauma, previous intraocular
surgery, uveitis, corneal opacity, or any ocular
disorder other than amblyopia and hyperopic ani-
sometropia were also excluded.

All eligible patients underwent a complete ocular
examination, including visual acuity measurement,
slit-lamp examination, dilated fundus examination,
ocular motility test, and appropriate strabismus
tests (including prism-cover test and modified Krim-
sky test). We used the Snellen E-chart, and Snellen

458 J  O  V R Volume 14, Issue 4, October-December 2019



Levodopa for Anisometropic Amblyopia; Farvardin et al

Table 1. Absolute refractive errors of both groups and differences in refractive errors (mean and standard deviation of the
spherical equivalent of anisometropia in both groups)

Placebo Levodopa P-value

Normal eye 1.99 ± 0.69 1.69 ± 0.77 0.28
Amblyopic eye 4.49 ± 0.59 4.29 ± 0.58 0.94
Difference 2.49 ± 0.82 2.61 ± 0.96 0.49

Figure 1. Flow diagram outlining the enrollment of the amblyopic children into the study.

visual acuity was measured under standardized
lighting conditions in the same room with the same
projector unit and at a viewing distance of 6 m.
Refraction was measured under cycloplegia with
1% cyclopentolate eye drops (cycloplegic refrac-
tion). We assessed the best subjective refraction,
measured visual acuity by using optical correction,
and registered the BCVA.

All interventions were conducted according to
the tenets of the Declaration of Helsinki, and the
study was approved by the Ethics Committee of our
institution. Signed informed consent was obtained

from at least one parent, and assent was obtained
from each child at the beginning of the study.

Eligible preschool children were divided into
two groups of 20 patients each. In the first
group, part-time occlusion therapy was adminis-
tered 3 h/day combined with an oral placebo,
and in the second group, part-time occlusion
therapy was administered 3 h/day with levodopa.
The dosage of levodopa was based on each
patient’s body weight; each patient received 6
mg/kg as a loading dose. Thereafter, each patient
received 2 mg/kg/day levodopa in three divided

J  O  V R Volume 14, Issue 4, October-December 2019 459



Levodopa for Anisometropic Amblyopia; Farvardin et al

doses administered for three weeks. The Pharmacy
Department of the Shiraz University of Medical
Sciences prepared the levodopa-benserazide and
placebo capsules. The placebo was made using
the same capsules used for levodopa, but they
were filled with lactose instead of the active
drug. Patients were instructed to take one cap-
sule three times/day at approximately 8-h inter-
vals after a meal. Visual acuities were measured
and recorded by an expert optometrist. Neither
patients nor examiners were aware of the differ-
ence.

The patients were followed up and examined
at weeks 1 and 3 during the treatment regi-
men and 12 weeks after the termination of all
treatments. All patients were informed about the
potential side effects of the drug such as nau-
sea, vomiting, headache, dizziness, dry mouth,
fatigue, nightmares, and mood changes. Parents
were instructed to record the date(s) of any side
effects. At each follow-up, the patients were asked
whether they experienced any subjective changes
or side effects. Systolic and diastolic blood pres-
sure and pulse rate were also measured at each
examination session. Laboratory tests, including
complete blood count and differential, liver func-
tion tests, blood urea nitrogen (BUN), and plasma
creatinine level measurements were performed at
baseline, one week and three weeks after the
initiation of treatment, and at three months (12
weeks) after the termination of all treatments. If a
patient’s laboratory test results were not within the
normal limits, the patient was excluded from the
study.

Study Outcome Measures

A change in Snellen BCVA was regarded as the
primary outcome measure. The amblyopic eye
was always tested first, and one varying line
was presented each time to prevent memorization
within a test session. The line in which the patient
could read more than half of the letters was
considered as the line of visual acuity. If the new
glasses resulted in better BCVA, the glasses were
changed, and the patient was given time to adapt to
the new prescription before starting the assigned
treatment. The BCVA values were converted to
logMAR visual acuities for statistical purposes. The
regression rate and side effects were secondary
outcome measures.

Statistical Analysis

All statistical analyses were performed using SPSS
Statistics for Windows/Macintosh, Version 17.0
(SPSS Inc., Chicago, IL). A paired two-tailed t-test
was used to compare the logMAR visual acuities
in consecutive test sessions in each group. The
independent samples t-test was used to com-
pare the logMAR visual acuities between the two
groups. A P < 0.05 was considered statistically
significant.

RESULTS

The mean (±standard deviation) age of the patients
was 6.4 years (±0.416) in the levodopa group
and 6.4 years (±0.447) in the placebo group.
Both groups included 10 male and 10 female
patients. The absolute refractive errors of both
groups and the difference in refractive errors
(mean and standard deviation of the spherical
equivalent of anisometropia in both groups) are
shown in Table 1. No statistically significant dif-
ference was observed between the groups in
the spherical equivalent of anisometropia (P =
0.49).

The mean and standard deviation of logMAR
visual acuities of the patients in both groups at
each examination are represented in Table 2.
No statistically significant difference was observed
between the groups in the baseline visual acuities
of the amblyopic eyes (P = 0.92). Visual acuities
were significantly better at three weeks after the
initiation of treatment than at the baseline in
both groups (P = 0.002 in the placebo group
and P = 0.007 in the levodopa group). The
improvement in visual acuities in the amblyopic
eyes was not significantly different between the
levodopa and placebo treatment groups (P =
0.11). To assess the stability of the treatment
effects, we repeated the examinations 12 weeks
after the termination of all treatments. Visual
acuities at this examination were still signifi-
cantly better than the baseline visual acuities (P
< 0.001 in the placebo group and P = 0.09
in the levodopa group). No statistically signifi-
cant difference was observed between the visual
acuities of the levodopa and placebo treatment
groups (P = 0.10). Visual acuities regressed 0.037
logMAR in the placebo group and 0.042 log-
MAR in the levodopa group 12 weeks after

460 J  O  V R Volume 14, Issue 4, October-December 2019



Levodopa for Anisometropic Amblyopia; Farvardin et al

the termination of all treatments. A compari-
son of the regression rates between the groups
showed no statistically significant difference (P =
0.89).

Compliance

All patients completed all test sessions. According
to previous reports, capsule consumption compli-
ance was determined using the number of remain-
ing capsules at the end of the treatment period.[10]
Regimen capsule compliance in both groups was
good, and no capsule remained at the end of the
treatment.

Tolerance

Patients were asked, during each follow-up,
whether they experienced any side effects. In the
first week, four patients in the placebo group (20%)
had an episode of mild nausea lasting for few
hours, but it did not continue during the course of
the study and did not necessitate discontinuation
of the treatment. No patient reported headache,
dizziness, fatigue, nightmares, and dry mouth.
No patients reported side effects in the levodopa
group. No significant changes were observed
in systolic or diastolic blood pressures or pulse
rate over the 15-week study period. Moreover, no
occlusion amblyopia occurred in the fellow eyes in
the control and treatment groups.

Laboratory Tests

A comparison of the baseline and 15-week study
results revealed no changes in various laboratory
tests. The complete blood count and differential
results remained unchanged. No specific changes
were observed in the serum BUN and creatinine
levels. Moreover, no change was noted in the liver
function test results.

DISCUSSION

The results of this placebo-controlled interven-
tional study suggest that adding short-term admin-
istration of levodopa to the standard part-time
occlusion therapy in preschool children with hyper-
opic anisometropic amblyopia does not yield better
visual outcomes.

For this study, we selected patients with hyper-
opic anisometropic amblyopia, which is the most
common type of anisometropic amblyopia. Other
types of amblyopia, such as strabismic amblyopia
and stimulus deprivation amblyopia are usually
diagnosed by parents at an earlier age and,
hence, treatment begins earlier. However, patients
with anisometropia have normal general appear-
ance and usually present at a later age; they
are frequently diagnosed during preschool ambly-
opia screening programs. Thus, the problem of
neglected amblyopia is of major importance in
anisometropic amblyopia, and anisometropia is the
most common cause of amblyopia in adults.[3]

Several studies on the treatment of amblyopia
have shown the beneficial effects of levodopa.[4–11]
The beneficial effects of levodopa and benserazide
in decreasing the fixation scotoma size and improv-
ing contrast sensitivity in amblyopia have already
been demonstrated.[7] Like carbidopa, benserazide
is a peripheral decarboxylase inhibitor. Levodopa
is a precursor to the neurotransmitter dopamine
and is administered to increase the dopamine
level in the central nervous system. However, most
levodopa is decarboxylated to dopamine before it
reaches the brain, and since dopamine is unable
to cross the blood–brain barrier, this leads to
little therapeutic effect in the brain with strong
peripheral side effects. By inhibiting the afore-
mentioned decarboxylation, benserazide allows
dopamine access to the brain. In addition, the
adverse effects caused by peripheral dopamine,
such as vasoconstriction, nausea, and arrhythmia
are minimized.

In a study on adults with amblyopia, Gottlob et
al showed an improvement in visual acuity after
one-week levodopa therapy.[8] In a single pilot
study, Leguire et al demonstrated the effects of
levodopa/carbidopa on visual function.[4] Based on
these initial findings, other studies were designed
to evaluate the effects of levodopa in human
amblyopia.[5, 6, 9–12] Some studies compared the
effects of levodopa therapy alone and levodopa
plus occlusion therapy on the visual function of
amblyopic eyes.[9, 10] Other studies compared the
effects of levodopa plus occlusion therapy and
occlusion therapy alone in amblyopia. The results
of these studies appeared to be contradictory;
some studies suggested beneficial effects,[5, 6, 18]
whereas others demonstrated that this treatment
was ineffective.[12, 19] Leguire et al, in a placebo-
controlled, single-dose study and in another

J  O  V R Volume 14, Issue 4, October-December 2019 461



Levodopa for Anisometropic Amblyopia; Farvardin et al

Table 2. Visual acuities of patients in the placebo and levodopa groups at each examination

Group Baseline mean ± SD
logMAR VA

Three-week mean ± SD
logMAR VA

Fifteen-week mean ± SD
logMAR VA

Placebo group 0.425 ± 0.231 0.234 ± 0.096 0.271 ± 0.087
Levodopa group 0.432 ± 0.242 0.187 ± 0.085 0.229 ± 0.071
P-value 0.92 0.11 0.10

logMAR, logarithm of the minimum angle of resolution; SD, standard deviation; VA, visual acuity

three-week longitudinal study on children with
amblyopia, showed that levodopa combined with
occlusion resulted in more improved visual acuity
than did placebo combined with occlusion.[5, 6]
Dadeya et al also compared the effects of com-
bined levodopa and occlusion therapy to those
of occlusion therapy alone in the management of
patients with strabismic amblyopia; more patients
in the levodopa group gained more than two
lines of visual acuity.[18] Contrary to these stud-
ies, in a randomized, placebo-controlled study on
children with amblyopia, Bhartiya et al reported
that levodopa supplementation did not have any
advantage over occlusion therapy alone.[12] Rashad
et al also observed that in children and adults
with different types of amblyopia, the mean log-
MAR was similar in the occlusion and levodopa
enhancement groups.[19] In their study, a higher
percentage of strabismic amblyopia was observed
in the levodopa group and a higher percentage
of mixed-etiology amblyopia was noticed in the
occlusion group.

Unlike the abovementioned studies, we
exclusively included patients with hyperopic
anisometropic amblyopia in both groups and,
therefore, compared similar groups. The similar
age (preschool children) in both groups in the
present study also allowed for a more reliable
comparison. Despite several differences among
the studies, the present study findings are in
agreement with the studies of Bhartiya et al and
Rashad et al who showed that supplementation
of occlusion therapy with levodopa offers no
additional benefits in patients with amblyopia
compared with occlusion therapy alone. Moreover,
a randomized trial of levodopa as a treatment for
residual amblyopia in older children demonstrated
that oral levodopa administration while continuing
patch therapy 2 h/day does not produce a
clinically or statistically significant improvement

in comparison with placebo administration or
patching alone.[20]

The aim of amblyopia therapy is to improve the
visual acuity of the amblyopic eye and to prevent
the regression of visual acuity. Many patients
with successfully treated amblyopia are known to
exhibit a regression of visual acuity once stan-
dard occlusion therapy is terminated.[2] Long-term
follow-up of levodopa treatment in children with
amblyopia has shown that the regression of visual
acuity in patients receiving levodopa therapy alone
was more (2.1 lines) than that in those receiving
levodopa plus occlusion (1.4 lines).[11] Pandey et
al also showed that visual acuity regressed sig-
nificantly when levodopa was not combined with
occlusion therapy.[21] Mohan et al demonstrated
that the addition of full-time occlusion to levodopa
helped maintain improved visual acuity for a longer
duration than did levodopa alone.[22] According to
our results, visual acuities regressed 0.037 logMAR
in the placebo plus occlusion treatment group and
0.042 logMAR in the levodopa plus occlusion treat-
ment group 12 weeks after the termination of all
treatments. Although the mean value of regression
was less in the placebo group, a comparison of
the regression rates between the groups showed
no statistically significant difference. Following the
termination of treatments in both groups, and
when the regression of visual acuity occurred, the
patients still had better visual acuities than their
baseline visual acuities.

Both groups completed all test sessions and
tolerated treatment well without significant side
effects. Before enrollment, the parents or other
caregivers were informed about the possible
adverse effects of medications, such as hypoten-
sion, arrhythmias, disorientation, confusion, and
extreme emotional states, particularly anxiety,
insomnia, visual hallucinations, somnolence, nar-
colepsy, depression, and psychosis. However,

462 J  O  V R Volume 14, Issue 4, October-December 2019



Levodopa for Anisometropic Amblyopia; Farvardin et al

these side effects are very uncommon given
the short duration of study. Moreover, no signif-
icant side effect was reported by the patients
in the present study. Abnormalities in labo-
ratory tests may occur in patients receiving
levodopa.[23–25] These include elevations in liver
and kidney function test parameters, such as
alkaline phosphatase, serum glutamic-oxaloacetic
transaminase/aspartate aminotransferase, serum
glutamic-pyruvic transaminase/alanine aminotrans-
ferase, and bilirubin levels, and abnormalities in
BUN and creatinine levels.[23] Thrombocytopenia
has also been reported. Nevertheless, in our
study, no abnormality in laboratory data was
detected.[24, 25]

One limitation of our study was the small sam-
ple size. However, according to calculations, 18
patients were required in each group to find a
difference of 0.1 logMAR visual acuity between the
treatment and placebo groups, and considering a
10% possibility of non-adherence, we included 40
patients. In addition, the present study was per-
formed on children with hyperopic anisometropia
aged 6 to 7 years old; hence, the results cannot
be generalized to other amblyopia types and to
patients in other age groups.

In conclusion, the results of the present study
indicated that in preschool children with hyper-
opic anisometropic amblyopia, short-term admin-
istration of levodopa combined with conventional
occlusion therapy offered no additional benefits
in visual outcomes than did occlusion therapy
alone. Moreover, the combined treatment offered
no advantage over the placebo treatment in terms
of the regression rate. This clearly indicates the
need for more studies to clarify the role of levodopa
in the management of amblyopia.

Financial Support and Sponsorship

Nil.

Conflicts of Interest

There are no conflicts of interest.

REFERENCES

1. von Noorden GK. Binocular vision and ocular motility:
theory and practice of management of strabismus. 5th ed.

Lous Mosby-Year Book: USA, St. Louis, Missouri 63146;
1996:216–254,512–520.

2. Keech RV. Practical management of amblyopia. In: Focal
points: clinical modules for ophthalmologist. San Fran-
cisco, CA: American Academy of Ophthalmology; 2000:18.

3. Arruga A. Effect of occlusion of amblyopic eye on
amblyopia and eccentric fixation. Trans Oph Soc UK
1962;82:45–49.

4. Leguire LE, Rogers GL, Bremer DL, Walson P,
Hadjieonstantinou-Neff M. Levodopa and childhood
amblyopia. J Pediatr Ophthalmol Strabismus
1992;29:290–298.

5. Leguire LE, Roger GL, Bremer DL, Walson PD, McGregor
ML. Levodopa/carbidopa for childhood amblyopia. Invest
Ophthalmol Vis Sci 1993;34:3090–3095.

6. Leguire LE, Walson PD, Rogers GL, Bremer DL, McGre-
gor ML. Longitudinal study of levodopa/carbidopa for
childhood amblyopia. J Pediatr Ophthalmol Strabismus
1993;30:354–360.

7. Gottlob I, Stangler-Zuschrott E. Effect of levodopa on
contrast sensitivity and scotomas in human amblyopia.
Invest Ophthalmol Vis Sci 1990;31:776–780.

8. Gottlob I, Charlier J, Reincoke RD. Visual acuities and sco-
tomas after one week levodopa administration in human
amblyopia. Invest Ophthalmol Vis Sci 1992;33:2722–
2728.

9. Leguire LE, Walson PD, Rogers GL, Bremer DL, McGregor
ML. Levodopa/carbidopa treatment for amblyopia in older
children. J Pediatr Ophthalmol Strabismus 1995;32:143–
151.

10. Leguire LE, Rogers GL, Walson PD, Bremer DL, McGre-
gor ML. Occlusion and levodopa-carbidopa treatment for
childhood amblyopia. J AAPOS 1998;2:257–264.

11. Leguire LE, Komaromy KL, Nairus TM, Rogers GL. Long-
term follow-up of L-dopa treatment in children with ambly-
opia. J Pediatr Ophthalmol Strabismus 2002;39:326–
330;quiz 345–346.

12. Bhartiya P, Sharma P, Biswas NR, Tandon R, Khokhar SK.
Levodopa-carbidopa with occlusion in older children with
amblyopia. J AAPOS 2002;6:368–372.

13. Nguyen-Lergos J, Durand J, Simon A. Catecholamine
cell types in the human retina. Clin Vis Sci 1992;7:435–
447.

14. Algaze A, Leguire LE, Roberts C, Ibinson JW, Lewis JR,
Rogers G. The effects of Ldopa on the functional magnetic
resonance imaging response of patients with amblyopia: a
pilot study. J AAPOS 2005;9:216–223.

15. Yang CI, Yang ML, Huang JC, Wan YL, Jui-Fang Tsai R,
Wai YY, et al. Functional MRI of amblyopia before and after
levodopa. Neurosci Lett 2003;339:49–52.

16. Yeh KC, August TF, Bush DF, Lasseter KC, Musson DG,
Schwartz S, et al. Pharmacokinetics and bioavailability
of Sinemet CR: a summary of human studies. Neurology
1989;39:25–38.

17. Bartholine G, Pletscher A. Cerebral accumulation and
metabolism of 14C-dopa after selective inhibition of periph-
eral decarboxylase. J Pharmacol Exp Ther 1968;161:14–20.

18. Dadeya S, Vats P, Malik KP. Levodopa/carbidopa in the
treatment of amblyopia. J Pediatr Ophthalmol Strabismus
2009;46:87–90;quiz 91–92.

J  O  V R Volume 14, Issue 4, October-December 2019 463



Levodopa for Anisometropic Amblyopia; Farvardin et al

19. Rashad MA. Pharmacological enhancement of treatment
for amblyopia. Clin Ophthalmol 2012;6:409–416.

20. Repka MX, Kraker RT, Dean TW, Beck RW, Siatkowski
RM, Holmes JM, et al. A randomized trial of levodopa
as treatment for residual amblyopia in older children.
Ophthalmology 2015;122:874–881.

21. Pandey PK, Chaudhuri Z, Kumar M, Satyabala K, Sharma
P. Effect of levodopa and carbidopa in human amblyopia.
J Pediatr Ophthalmol Strabismus 2002;39:81–89.

22. Mohan K, Dhankar V, Sharma A. Visual acuities after lev-
odopa administration in amblyopia. J Pediatr Ophthalmol

Strabismus 2001;38:62–67;quiz 96–97.
23. Dhall R, Kreitzman DL. Advances in levodopa therapy

for Parkinson disease: review of RYTARY (carbidopa
and levodopa) clinical efficacy and safety. Neurology
2016;86:S13–S24.

24. Lee KE, Kang HS, Yu HJ, Roh SY. Thrombocytopenia asso-
ciated with levodopa treatment. J Mov Disord 2013;6:21–
22.

25. Giner V, Rueda D, Salvador A, Hernández JC, Esteban
MJ, Redón J. Thrombocytopenia associated with levodopa
treatment. Arch Intern Med 2003;163:735–736.

464 J  O  V R Volume 14, Issue 4, October-December 2019