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Patient characteristics, diagnosis, and treatment of
non-contact lens related Acanthamoeba keratitis
Savitri Sharma, Prashant Garg, Gullapalli N Rao
Abstract
Aim—To review the clinical characteris-
tics, diagnosis, and visual outcome in
patients with non-contact lens related
Acanthamoeba keratitis and compare the
findings with reported series of contact
lens associated Acanthamoeba keratitis.
Methods—Medical and microbiology
records of 39 consecutive patients with a
diagnosis of Acanthamoeba keratitis, at a
tertiary eyecare centre in India between
January 1996 and June 1998, were analysed
retrospectively.
Results—A majority of the patients pre-
sented with poor visual acuity and large
corneal stromal infiltrates (mean size 38.20
(SD 26.18) mm). A predisposing factor
was elicited in 19/39 (48.7%) patients
(trauma 15, dirty water splash three, leaf
juice one). None of the patients had worn
contact lenses. Most patients (26/39
(66.6%)) came from a low socioeconomic
background. Complaint of severe pain was
not a significant feature and radial kera-
toneuritis was seen in 1/39 (2.5%) patients.
A ring infiltrate was present in 41.1% of
cases. A clinical diagnosis of fungal kerati-
tis was made in 45% of the patients before
they were seen by us. However, all patients
were diagnosed microbiologically at our
institute based on demonstration of Acan-
thamoeba cysts in corneal scrapings (34/
39) and/or culture of Acanthamoeba (34/
39). Treatment with biguanides (PHMB,
15/38 (39.4%), PHMB with CHx, 23/38
(60.5%), one patient did not return for
treatment) resulted in healing with scar
formation in 27 out of 31(87.0%) followed
up patients (mean time to healing 106.9
days). Overall visual outcome was poor
with no statistical diVerence between cases
diagnosed within 30 days (early) or 30 days
after (late) start of symptoms. The visual
outcome in cases requiring tissue adhesive
(five) and keratoplasty (three) was also
poor.
Conclusions—This is thought to be the
largest series of cases of Acanthamoeba
keratitis in non-contact lens wearers. In
such cases, the disease is advanced at
presentation in most patients, pathogno-
monic clinical features are often not seen,
disease progression is rapid, and visual
outcome is usually poor. Possible exist-
ence of Acanthamoeba pathotypes specifi-
cally associated with non-contact lens
keratitis and unique to certain geographi-
cal areas is suggested.
(Br J Ophthalmol 2000;84:1103–1108)
From a historical perspective Acanthamoeba
keratitis has been described as a recent
epidemic.1It has been recognised in almost all
parts of the world.2–6 Evidence from several
studies has suggested soft contact lens wear as
the greatest risk factor78although some studies
have reported the development of Acan-
thamoeba keratitis in patients with no apparent
predisposing factor.49With most of the litera-
ture focusing on contact lens related Acan-
thamoeba keratitis, ophthalmologists may hesi-
tate to diagnose this entity in patients without
lenses. Chynn et al10 reported some of the
diVerences between contact lens and non-
contact lens related Acanthamoeba keratitis in a
small number of patients. Mean time to
diagnosis was significantly longer and visual
outcome was significantly lower in non-contact
lens users compared with those who wore con-
tact lenses. The study recommended the need
for increased suspicion of Acanthamoeba kerati-
tis in patients who did not present with the
obvious risk factor of contact lenses. On the
basis of our experience, on a much larger scale,
with Acanthamoeba keratitis unrelated to con-
tact lens wear, we support the above conten-
tion and report in this study 39 cases of Acan-
thamoeba keratitis in non-contact lens users.
We present the clinical characteristics, diagnos-
tic methods, treatment schedules, and out-
come in these cases and discuss our findings in
the context of reported series of Acanthamoeba
keratitis in patients using contact lenses.
Patients and methods
All patients treated for Acanthamoeba keratitis
between January 1996 and June 1998 were
included in the study. The clinical and
microbiology records were reviewed retrospec-
tively. Information obtained from the clinical
records included age, sex, socioeconomic
status, medical history including predisposing
risk factors, duration and type of symptoms,
prior diagnosis and treatment, presenting ocu-
lar findings, ocular treatment, and final visual
outcome.
Laboratory data of all patients were sought
from microbiology records. Results of smear
examinations of corneal scrapings which in-
cluded Gram stain, Giemsa stain, and potas-
sium hydroxide with calcofluor white
(KOH+CFW) stain were noted. Culture re-
sults indicating any significant growth of bacte-
ria, fungus, or Acanthamoeba were recorded
along with the in vitro sensitivity test results.
Cultures in all cases had included a variety of
media, such as sheep blood agar (aerobic,
anaerobic), chocolate agar, brain-heart infu-
sion broth, thioglycollate broth, Sabouraud’s
Br J Ophthalmol 2000;84:1103–1108 1103
Jhaveri Microbiology
Centre, LV Prasad Eye
Institute, LV Prasad
Marg, Banjara Hills,
Hyderabad-500 034,
India
S Sharma
Cornea Service
P Garg
G N Rao
Correspondence to:
Dr Sharma
savitri@lvpeye.stph.net
Accepted for publication
26 April 2000
www.bjophthalmol.com
dextrose agar, and non-nutrient agar with
Escherichia coli overlay, allowing for the growth
of bacteria, fungus, or Acanthamoeba. Signifi-
cance was assigned to the bacterial or fungal
growth if the same organism had grown in
more than one medium or a similar organism
was seen in the smears of corneal scrapings. All
organisms including Acanthamoeba were iden-
tified using standard procedures.11
Once the diagnosis was established by
microbiological investigation the treatment was
started with polyhexamethylene biguanide
0.02% (PHMB, Baquasil, ICI, USA) and/or
chlorhexidine digluconate 0.02% (CHx,
Sigma, C-9394) instilled half hourly to the
aVected eye day and night for 2–3 days (usually
as an inpatient) and then 1 hourly for a week.
The frequency of instillation of the biguanides
was reduced to 3 or 4 hourly per day according
to clinical response over subsequent weeks and
continued after resolution of inflammatory
signs for 2–3 weeks. In 18 (46.1%) cases
Neosporin ointment (neomycin, Dominion)
was added at night. Concomitant bacterial
infection was treated with ciprofloxacin 0.3%
eye drops and modified if required according
to the sensitivity results from the laboratory.
Topical cycloplegics and oral analgesics were
used in most cases. Steroids were not used in
any case.
For analysis, the patients were divided into
two groups according to the time between the
onset of symptoms and diagnosis of Acan-
thamoeba keratitis (initiation of antiamoebic
treatment). The “early” category consisted of
patients who were diagnosed within 1 month of
onset of symptoms and the remaining were
labelled as “late”.
Results
Over a span of 2
1
⁄
2
years, we treated 39 eyes of
39 patients with Acanthamoeba keratitis. Table
1 shows the demographic data of these
patients. The laboratory data are listed in
Table 2.
More males than females (23:16) were
aVected, though the diVerence was not signifi-
cant (p = 0.2945). Mean age of patients was
36.8 years with a range of 18–70 years.
All except six patients had received ophthal-
mic attention before reporting to our cornea
service and were being treated for presumed
bacterial, fungal, or viral keratitis based on
clinical features. None had been investigated
microbiologically. The most common clinical
suspicion was of fungal keratitis (15/33,
45.4%). Viral keratitis was suspected in only
four cases. One patient was clinically suspected
to have Acanthamoeba keratitis and was receiv-
ing PHMB.
None of the patients in our series wore con-
tact lenses. While 15 patients gave a history of
definite trauma with either vegetative matter,
stone, or dust, three patients reported splash-
ing unclean water into the eyes along with
trauma. In one patient, a suspected foreign
body on the cornea was removed with the
tongue. The same patient used extract of some
herbs in the eye before seeing a doctor who
treated her for bacterial keratitis. In 20
(51.2%) patients no definite risk factor could
be elicited from the history.
SIGNS AND SYMPTOMS
All patients presented to us with redness,
watering, and decrease in vision. Ocular pain
disproportionate to the degree of keratitis was
not noted for any of the patients. Various clini-
cal signs noted in our patients are shown in
Table 3. Radial keratoneuritis, which has been
described as specific for the diagnosis of Acan-
thamoeba keratitis, was seen in only one
patient. Anterior stromal infiltrates were
present in all patients except one in the late
group who had a corneal scar with oedema. A
ring infiltrate was present in 41.1% of the
patients and was the presenting feature more
often (45.8%) in the early than the late group
(33.3%). The diVerence was not statistically
significant (p = 0.6617). Less specific signs
Table 1 Age and sex distribution of patients with
laboratory confirmed Acanthamoeba keratitis
Patients
Category
TotalEarly Late
Sex
Male 15 8 23
Female 9 7 16
Age (years)
0–20 1 0 1
21–40 14 11 25
41–60 8 4 12
>61 101
Mean age (years) 36.75 37.00 36.8
No of patients 24 15 39
Early = cases diagnosed within 30 days of start of symptoms.
Late = cases diagnosed 30 days after start of symptoms.
Table 2 Laboratory data of early and late cases of
Acanthamoeba keratitis
Tests
Category
Total (39)
Early cases
(n=24)
Late cases
(n=15)
Acanthamoeba
Cysts in smears
Gram 15 (62.5%) 11 (73.3%) 26 (66.6%)
Giemsa 14 (58.3%) 9 (60.0%) 23 (58.9%)
KOH+CFW 21 (87.5%) 13 (86.6%) 34 (87.1%)*
Culture
Acanthamoeba 21 (87.5%) 13 (86.6%) 34 (87.1%)†
Gram +ve
bacteria
5 (20.8%) 4 (26.6%) 9 (23.0%)
*Smear −ve culture +ve - (5).
†Smear +ve culture −ve - (5).
Early = cases diagnosed within 30 days of start of symptoms.
Late = cases diagnosed 30 days after start of symptoms.
Table 3 Clinical signs in early and late cases of
Acanthamoeba keratitis at presentation
Clinical signs
Category
Total
(n=39)
Early cases
(n=24)
Late cases
(n=15)
Ring infiltrate 11 (45.8%)* 5 (33.3%) 16 (41.0%)
Satellite infiltrate 9 (37.5%) 2 (13.3%) 11 (28.2%)
DiVuse infiltrate 11 (45.8%) 10 (66.6%) 21 (53.8%)
Endothelial plaque 4 (16.6%) 1 (6.6%) 5 (12.8%)
Hypopyon 14 (58.3%) 7 (46.6%) 21 (53.8%)
Dendritic lesion 1 (4.1%) 0 1 (2.5%)
Radial
keratoneuritis
0 1 (6.6%) 1 (2.5%)
*In two cases the ring infiltrate was partial.
Early = cases diagnosed within 30 days of start of symptoms.
Late = cases diagnosed 30 days after start of symptoms.
1104 Sharma, Garg, Rao
www.bjophthalmol.com
such as satellite stromal infiltrates, diVuse
stromal infiltrates, and endothelial plaques
were seen in many of the patients with no sig-
nificant diVerence between the early and late
groups. One patient in the early group
presented with dendritiform epithelial lesion
mimicking viral keratitis. More than half of the
patients (53.8%) had anterior chamber reac-
tion with hypopyon ranging from trace to 3.5
mm.
DIAGNOSIS
Diagnosis in all cases was based on the demon-
stration of Acanthamoeba cysts or trophozoites
in corneal scrapings by smear examination
and/or culture. Twenty four of 39 (61.5%)
patients were diagnosed within a month (early)
and 15 (38.5%) cases were diagnosed 1 month
(late) after start of symptoms. Twenty nine
(74.3%) cases were positive for Acanthamoeba
both on smear examination and culture where
as five each were detected either by culture or
smear (Table 2). Among 34 smear positive
cases, KOH+CFW stain detected cysts in all
cases. Fewer cases showed cysts in corneal
scrapings by Gram and Giemsa stain (26/34
(76.4%) and 23/34 (67.6%) respectively). Bac-
terial growth along with Acanthamoeba was
seen in five cases in the early group and four
cases in late group. The bacterial co-isolates
were mainly low virulence organisms such as
Staphylococcus epidermidis (6/9) and Corynebac-
terium species (2/9). Staphylococcus aureus was
isolated in one case.
TREATMENT OUTCOME
Anti-Acanthamoeba treatment with cationic
antiseptics (PHMB and/or CHx) was initiated
in all cases as soon as the microbiological
diagnosis was made. The therapeutic strategy
and outcome in all patients is shown in Figure
1. In 27 out of 31 patients followed up
(87.0%) the corneal infiltrate resolved follow-
ing medical treatment in a mean time of 106.9
(9–281) days. Seven patients were lost to
follow up, four of whom were refused
admission for financial reasons, and three
patients left against medical advice after being
treated for 5–7 days. Post-treatment visual
acuity was recorded in 14 early and 13 late
cases. Visual acuity before and after treatment
in early and late cases is shown in Figure 2.
Improvement in visual acuity following treat-
ment was seen in 35.7% (5/14) of early and
30.7% (4/13) of late cases (p=0.891). Applica-
tion of tissue adhesive (n-butyl cynoacrylate
tissue adhesive) with bandage contact lens was
performed in five cases (four in late, one in
early) for extreme thinning or perforation less
than 2 mm in size. After prolonged medical
therapy with PHMB and CHx (mean 88 days)
the infiltrates resolved with scarring and
Figure 1 Therapeutic strategy and treatment outcome in 39 patients with non-contact lens related Acanthamoeba
keratitis.
Total no of patients 39
Early 24 Late 15
Medical Mx
19
Non-specific Mx
(LTFU)
1
Surgical Mx
4
• PK 3
• Evisceration 1
• PHMB and/or CHx
• PHMB and CHx
+
+
• PHMB and CHx
tissue adhesive
tarsorrhaphy
• PHMB and/or CHx
• PHMB and CHx
+
tissue adhesive
12
1
1
9
4
Medical Mx
15
Surgical Mx
0
Healed scar
14
LTFU
5
Healed scar
13
LTFU
2
Figure 2 Pretreatment and post-treatment visual acuity in
non-contact lens related Acanthamoeba keratitis patients
diagnosed within 30 days (early, 14 cases) and 30 days
after (late, 13 cases) start of symptoms.
PLPR
Early
Late
CF
CF
HM
HM
6/60
6/60
6/36
6/36
6/30
6/30
6/18
6/18
6/12
PLPR
Post-treatment visual acuity
Pretreatment visual acuity
6/12
Patient characteristics, diagnosis, and treatment of non-contact lens related Acanthamoeba keratitis 1105
www.bjophthalmol.com
vascularisation in all. However, the final visual
acuity remained poor (PL/PR three, HM one,
and 6/36 one). Paramedian tarsorrhaphy was
performed for associated lagophthalmos in
one patient. Therapeutic penetrating kerato-
plasty (PK) was performed in three cases in
the early group owing to large infiltrate at the
time of presentation which failed to respond
even on intensive medical therapy. The
outcome of surgical excision however, was not
encouraging. One patient required limbus to
limbus graft 7 days after presentation. The
graft developed an infiltrate in the immediate
postoperative period followed by corneal
perforation and pseudocornea formation. The
graft failed in the second patient, and in the
third patient there was choroidal detachment
with vitreous opacities resulting ultimately in
phthisis. Development of vitreous opacities
and scleral involvement was noted in one
patient who ultimately required evisceration.
Discussion
Corneal ulceration is a major cause of mo-
nocular blindness in developing countries. A
recent report from this centre, in a well
conducted survey of an urban population in
south India, listed corneal blindness as the
third major cause of visual disability and
blindness.12 Incidence of corneal ulcers in
south India has been estimated to be 11.3 per
10 000 population and has been referred to as
a blinding disease of epidemic proportions.13
Epidemiology and aetiology of corneal ulcera-
tion in south India has already been
published14 wherein 1% of culture positive
cases were caused by Acanthamoeba. The
reported incidence of Acanthamoeba keratitis in
India varies from 1–3% in various
published14 15 and unpublished series. Of note,
barring single case reports in contact lens
wearers,16 17 all reported cases are predomi-
nantly seen in non-contact lens wearers.41415
While Sharma et al4reported complete healing
in four out of five adequately followed up
cases (treated with neosporin/miconazole/
ketoconazole) they did not comment on visual
outcome. Likewise, none of the other
studies14 15 has dwelt on clinical features, treat-
ment schedule, or visual outcome. Conse-
quently, such data are severely lacking from
this part of the world.
On the other hand, some reports from the
USA10 and the UK18 have described the disease
in non-contact lens wearers. While contribut-
ing significantly to the understanding of Acan-
thamoeba keratitis in non-contact lens wearers,
both these studies were encumbered by rela-
tively small sample size. To the best of our
knowledge, the present study is the largest
series of patients with non-contact lens related
Acanthamoeba keratitis.
Diagnosis of Acanthamoeba keratitis, based
on clinical features, was made only in one out
of 33 patients by physicians who had treated
these patients before they were seen by us. The
majority of these patients (15/33(45.4%)) were
treated as fungal keratitis which is diVerent
from what has been reported for patients with
contact lens related Acanthamoeba keratitis
who generally undergo treatment for herpes
simplex keratitis before the microbiological
diagnosis is made.19 The presence of satellite
stromal infiltrates and endothelial exudates in
some of our patients points more towards fun-
gal aetiology. Additional reason for underdiag-
nosis of Acanthamoeba keratitis could have
been the relatively high incidence of fungal
keratitis in India (50%),14 and lack of enough
reports of Acanthamoeba keratitis in non-
contact lens wearers. Radial keratoneuritis,
described as typical for Acanthamoeba keratitis,
was also uncommon in our patients. Visual loss
in contrast with severe pain was the predomi-
nant symptom in our series. Absence of
complaints of pain disproportionate to clinical
features in our patients is probably related to
absence of keratoneuritis. Although predilec-
tion of Acanthamoeba to neural tissue has been
demonstrated,20 it is possible that the same is
not seen with all species and pathotypes of
Acanthamoeba.
Contact lens wear does not emerge as an
important risk factor for Acanthamoeba kerati-
tis in our population. This can probably be
attributed to the relatively few people who are
exposed to contact lens wear in this country.
In 20/39 (51.2%) of the patients in this series
a definite risk factor that led to Acanthamoeba
keratitis could not be elicited. In previously
published reports of this entity in non-contact
lens wearers from India4and elsewhere,10 18
trauma and exposure to contaminated water
have been identified as major risk factors. Use
of traditional eye medicine may be added as
another risk factor though this was reported in
just one patient in this series. A recent study
from south India reported use of traditional
eye medicine by 47.7% of patients with kerati-
tis in a rural setting.21 However, the lone
patient with Acanthamoeba keratitis in their
series had not used any traditional medicine. It
is possible that some of our patients experi-
enced events that were too trivial to remem-
ber. The low socioeconomic background of
our patients (26/39(66.6%)) may be a con-
tributory factor. The innocuous habit of
splashing water into the eye following dust fall
may not be remembered by the patients and
cannot be ruled out in our patients. On the
other hand, it is also possible that particularly
virulent strains of Acanthamoeba adhere to and
invade normal corneal epithelium, a possi-
bility suggested by the electron microscopy
study of Neiderkorn et al22 which showed rigid
host specificity of A castellanii to intact chinese
hamster, pig, and human corneas in vitro.
In this series the diagnosis and initiation of
treatment was delayed in 38.5% of patients by
more than 30 days. This is in contrast with
contact lens related Acanthamoeba keratitis.
Radford et al18 reported that diagnosis was
established within 1 month in 89% of contact
lens related cases. This delayed diagnosis
could have been because of lack of severe pain
and low socioeconomic status of most of our
patients. Compared with Acanthamoeba kerati-
tis in contact lens wearers, severe corneal fea-
tures were noted in our patients at presenta-
tion. The stromal infiltrates, even in early
1106 Sharma, Garg, Rao
www.bjophthalmol.com
cases, varied in size from 11.9–88 mm (mean
38.3 (SD 20.6) mm ). Large ulcer size and
central location in 22/24 (91.6%) patients in
the early group and 13/15 (86.6%) in late
group account for the overall poor visual out-
come in our patients. Though we found the
final visual outcome better in cases diagnosed
early than late, the diVerence was not
signifcant (p=0.891), which is in contrast to
other studies which have shown a significant
diVerence.10 18 23 While Radford et al18 related
the less assured visual outcome in patients
with no contact lens history to delayed
diagnosis we believe that this is also related to
the presence of more severe disease in these
patients. Wide variability in virulence among
the strains of Acanthamoeba in diVerent
geographical areas, as well as diVerences in
host immune responses, may contribute to the
variability in clinical presentation. In the
patients in this series, a rapid progression of
the corneal pathology leading to early and
severe damage to corneal tissues is seen. This
is in contrast with slow progress of the disease
in contact lens related keratitis where a
marked stromal involvement may not be obvi-
ous until 6 weeks or more.24 Though the host
factors may have an important part to play,
variability among diVerent strains can not be
ruled out. Co-infection with bacteria may be
another explanation in this setting; however, in
this series there were only nine (23%) cases
with mixed infection with bacteria.
Microbiological diagnosis in this series was
satisfactory in majority of the patients with the
organisms being demonstrated in smears and
cultures. In 32/34 cases the first scraping
yielded a positive result leaving only two
requiring rescrapes. As reported earlier,25
KOH+CFW staining of corneal scrapings
proved to be the most rewarding of all methods
for the diagnosis of Acanthamoeba keratitis.
With increased awareness and better diagnos-
tic facilities in this part of the world, the
incidence of Acanthamoeba keratitis is likely to
be reported more often in non-contact lens
wearers which may contrast with the decrease
in the number of cases reported from devel-
oped countries.18
The final visual outcome, as measured by
resolution of the infiltrate and healing of the
ulcer, was achieved in 27/31 (87.0%) patients
with no significant diVerence between early
and late cases. Use of cationic antiseptics
(PHMB and CHx) has resulted in a dramatic
improvement in the clinical management of
Acanthamoeba keratitis. We used PHMB in
15/38 (39.4%) and CHx with PHMB in 23/38
(60.5%) patients. Neosporin was used only
during sleeping hours in a limited number of
patients which may not have played a signifi-
cant part in control of infection. Although
combination therapy with PHMB and propa-
midine has been reported earlier23 the choice
of combination therapy with PHMB and CHx
was based on in vitro observation of low MCC
(minimum cysticidal concentration) of
PHMB and CHx and the reported synergistic
activity of both.26 The mean duration of treat-
ment in our patients was 106.9 days which is
comparable with the duration reported (135
days) for contact lens wearers,18 23 thereby sug-
gesting that though the clinical features were
severe time taken to respond to medical
therapy was not unduly long. This also
suggests that the susceptibility of Acan-
thamoeba to biguanides in our series is similar
to what has been reported from contact lens
wearers.
Studies are taking place at our centre to
determine susceptibility of Acanthamoeba iso-
lates from non-contact lens wearers to various
antimicrobials and the results (unpublished)
support this hypothesis.
Although the visual outcome was poor, a
clinical resolution of infiltrate was obtained in
majority of the patients with a promise of good
vision following optical corneal graft at a later
stage. Increased awareness may enable early
and frequent recognition and proper manage-
ment of this devastating corneal disease in
patients other than contact lens wearers.
Financial support: Hyderabad Eye Research Foundation,
Hyderabad, India.
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