Complications and fitting challenges associated with scleral contact lenses: A review

Abstract

The modern scleral contact lens (ScCL) has evolved from the very first contact lens fitted 128 years ago. Originally manufactured in glass and oxygen impermeable plastics, these lenses are available today in high Dk gas permeable materials that allow permeation of oxygen, reducing many of the complications that were seen with older generation ScCL. However, as with any new contact lens modality, the modern ScCL brings with it a new set of complications and fitting limitations.
Pubmed searches under different keywords were conducted.
Existing literature provides some reports of infection with the scleral devices, although these are often seen in severely compromised corneas, while hypoxic and inflammatory complications are rarely reported in the literature. Furthermore, the somewhat complex relationship of a scleral lens on the eye can create fitting and removal challenges. Anomalies such as conjunctival prolapse, epithelial bogging, midday fogging, and limbal bearing have been reported, and appear to be unique sequelae to scleral lens wear.
Although this revolutionary technology broadens the scope in which practitioners can treat patients with irregular ocular surfaces, reports of these complications indicate that there is still a need for continued research to further enhance the clinical outcomes of this promising contact lens modality.
Published by Elsevier Ltd.

Full text

Review
article
Complications
and
fitting
challenges
associated
with
scleral
contact
lenses:
A
review
Maria
K.
Walker*,
Jan
P.
Bergmanson,
William
L.
Miller,
Jason
D.
Marsack,
Leah
A.
Johnson
University
of
Houston
College
of
Optometry,
4901
Calhoun
Road,
Houston,
TX
77004,
USA
A
R
T
I
C
L
E
I
N
F
O
Article
history:
Received
18
May
2015
Received
in
revised
form
13
July
2015
Accepted
19
August
2015
Keywords:
Scleral
contact
lens
Complication
Hypoxia
Midday
fogging
Conjunctival
prolapse
A
B
S
T
R
A
C
T
Introduction:
The
modern
scleral
contact
lens
(ScCL)
has
evolved
from
the
very
first
contact
lens
fitted
128
years
ago.
Originally
manufactured
in
glass
and
oxygen
impermeable
plastics,
these
lenses
are
available
today
in
high
Dk
gas
permeable
materials
that
allow
permeation
of
oxygen,
reducing
many
of
the
complications
that
were
seen
with
older
generation
ScCL.
However,
as
with
any
new
contact
lens
modality,
the
modern
ScCL
brings
with
it
a
new
set
of
complications
and
fitting
limitations.
Methods:
Pubmed
searches
under
different
keywords
were
conducted.
Results:
Existing
literature
provides
some
reports
of
infection
with
the
scleral
devices,
although
these
are
often
seen
in
severely
compromised
corneas,
while
hypoxic
and
inflammatory
complications
are
rarely
reported
in
the
literature.
Furthermore,
the
somewhat
complex
relationship
of
a
scleral
lens
on
the
eye
can
create
fitting
and
removal
challenges.
Anomalies
such
as
conjunctival
prolapse,
epithelial
bogging,
midday
fogging,
and
limbal
bearing
have
been
reported,
and
appear
to
be
unique
sequelae
to
scleral
lens
wear.
Conclusion:
Although
this
revolutionary
technology
broadens
the
scope
in
which
practitioners
can
treat
patients
with
irregular
ocular
surfaces,
reports
of
these
complications
indicate
that
there
is
still
a
need
for
continued
research
to
further
enhance
the
clinical
outcomes
of
this
promising
contact
lens
modality.
Published
by
Elsevier
Ltd
on
behalf
of
British
Contact
Lens
Association.
Contents
1.
Introduction
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89
1.1.
Resurgence
of
Scleral
Contact
Lenses
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89
1.2.
Literature
search
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89
1.3.
History
of
scleral
contact
lens
complications
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90
2.
Complications
of
scleral
contact
lens
wear
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90
2.1.
Infection-related
complications
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90
2.2.
Inflammation-related
complications
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90
2.3.
Hypoxia-related
complications
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90
3.
Fitting
challenges
associated
with
scleral
contact
lenses
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91
3.1.
The
asymmetric
sclera
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91
3.2.
Lens
seal-off
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92
3.3.
Conjunctival
prolapse
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92
3.4.
Limbal
bearing
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93
3.5.
Mid-day
fogging
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93
3.6.
Epithelial
bogging
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4.
Conclusion
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94
Acknowledgements
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References
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*
Corresponding
author
at:
University
of
Houston
College
of
Optometry,
4901
Calhoun
Road,
David
J.
Armistead
Bldg.,
Houston,
TX
77004,
USA.
E-mail
addresses:
mkwalker@central.uh.edu
(M.K.
Walker),
jbergmanson@central.uh.edu
(J.P.
Bergmanson),
wlmiller@uiwtx.edu
(W.L.
Miller),
jmarsack@central.uh.edu
(J.D.
Marsack),
leahannjohnson@gmail.com
(L.A.
Johnson).
http://dx.doi.org/10.1016/j.clae.2015.08.003
1367-0484/Published
by
Elsevier
Ltd
on
behalf
of
British
Contact
Lens
Association.
Contact
Lens
and
Anterior
Eye
39
(2016)
88–96
Contents
lists
available
at
ScienceDirect
Contact
Lens
and
Anterior
Eye
journal
homepage:
www.elsevier.com/locate/clae

1.
Introduction
1.1.
Resurgence
of
Scleral
Contact
Lenses
The
first
device
resembling
a
scleral
contact
lens
(ScCL)
was
fitted
in
1887
by
the
firm
of
F.
Ad.
Müller
&
Söhne
of
Wiesbaden,
Germany
for
a
patient
with
lagophthalmic
keratitis
in
the
right
eye
due
to
cancerous
destruction
of
the
lower
eyelid
[1].
This
therapeutic,
blown
glass
shell
was
worn
on
an
extended
wear
basis
and
probably
had
a
total
diameter
of
about
25.00

30.00
mm
[2].
In
1888,
Adolf
Fick
designed
a
ground
shell
with
a
total
diameter
of
20.00
mm
in
a
series
of
five
patients
with
corneal
scarring
and
one
with
keratoconus,
only
one
of
them
achieving
visual
improvement
[3].
In
the
same
year,
Photinos
Panas
reported
that
his
junior
colleague,
Eugène
Kalt,
had
obtained
a
significant
increase
in
visual
acuity
with
a
shell
in
a
case
of
keratoconus
[4].
Examination
of
Kalt's
shells
revealed
that
they
had
a
mono-curve
back
surface
construction
with
a
total
diameter
of
16.00–22.00
mm
[5].
In
1889,
August
Müller
was
the
first
clinician
to
correct
refractive
error
with
a
contact
lens,
when
he
neutralized
his
own
high
myopia
using
a
ground
scleral
lens
having
a
total
diameter
of
20.00
mm
[6].
The
practice
of
fitting
lenses
using
a
trial
set
was
originated
by
the
German
firm
of
Carl
Zeiss,
which
in
the
1920s
offered
a
choice
of
four
alternative
specifications
of
ground
lenses
to
correct
keratoconus
[7].
Within
a
decade
the
fitting
set
expanded
to
39
lenses
to
allow
correction
of
refractive
errors
[8].
While
there
was
a
range
of
base
curve
radii
and
back
surface
scleral
radii,
each
lens
had
the
same
primary
optic
diameter
of
12.00
mm
and
the
same
overall
diameter
of
20.00
mm.
Successful
eye
impressions
were
first
made
by
István
Csapody
in
1929
[9]
and
the
manufacture
and
fitting
of
molded
scleral
lenses
using
this
approach
was
developed
by
József
Dallos
[10].
The
earliest
report
of
the
successful
clinical
use
of
poly(methyl
methacrylate)
(PMMA)
ScCL
was
made
by
Petrus
Thier
in
1939
[11].
The
major
limitation
of
both
glass
and
PMMA
contact
lenses
is
their
negligible
gas
transmissibility,
which
has
been
associated
with
hypoxic
complications
for
patients
wearing
them
from
the
late
19th
until
the
latter
part
of
the
20th
century.
The
first
rigid
gas
permeable
(GP)
contact
lens
material
was
cellulose
acetate
butyrate
which
came
into
use
in
the
mid-1970s
[12].
Subsequently,
siloxymethacrylate
and
fluoromethacrylate
materials
were
developed
with
greatly
increased
oxygen
perme-
ability,
which
reduced
hypoxic
complications
with
corneal
lenses.
Even
with
the
development
of
newer
GP
materials,
the
re-
emergence
of
scleral
contact
lenses
did
not
gain
momentum
until
the
late
1990's
and
early
2000's.
Modern
day
ScCL
pioneers
include
Donald
Ezekiel
of
Perth,
Australia,
who
was
the
first
to
describe
fitting
gas
permeable
scleral
contact
lenses
–
on
43
patients
–
in
1983
[13],
Perry
Rosenthal
of
the
United
States,
Ken
Pullum
of
the
United
Kingdom,
and
Rients
Visser
of
The
Netherlands,
who
have
all
led
the
advancement
of
ScCL
for
refractive
correction
in
post-
surgical
and
keratoconic
eyes
[14–16].
These
innovative
practi-
tioners
realized
the
potential
of
the
scleral
lens
modality,
and
have
led
practitioners
to
embrace
this
new
application
of
a
historical
concept.
1.2.
Literature
search
The
goal
of
this
review
article
was
to
examine
the
literature
and
compile
a
list
of
documented
complications
and
fitting
challenges
associated
with
ScCL
use.
The
literature
reviewed
in
this
article
was
Table
1
Case
reports
of
infectious
events
amongst
scleral
contact
lens
wearers.
Author
(year)
ScCL
Indication(s)
a
Infectious
Organism(s)
Outcome
Taking
steroids
(y/n)
Taking
prophylactic
antibiotics
(y/n)
Comments
Study
Design
b
Rosenthal
et.al.
[16]
(2000)
PED
post-PK
Mycobacterium
abcessus
Failed
graft
Y
Y
Known
epi
defect
at
time
of
infection
CS/R
Rosenthal
et.al.
[16]
(2000)
PED
post-PK
Streptococcus
pneumonia
Failed
graft
Y
Y
CS/R
Rosenthal
et.al.
[16]
(2000)
PED
post-PK
Alpha-hamolytic
streptococcus,
Staphlococcus
epidermidis
(x2)
Failed
graft
x3
Y
Y
Known
epi
defect
at
time
of
infection
CS/R
Rosenthal
et.al.
[16]
(2000)
PED
post-PK
Staphylococcus
epidermidis
Failed
graft
Y
Y
Known
epi
defect
at
time
of
infection
CS/R
Kalwerisky
et.al.
[17]
(2012)
Exposure
keratopathy
related
to
acute
thermal
keratitis
MRSA
Resolved
with
fortified
antibiotics
N
Y
CS/R
Kalwerisky
et.al.
[17]
(2012)
Exposure
keratopathy
related
to
acute
thermal
keratitis
Pseudomonas
aeruginosa
Resolved
with
fortified
antibiotics
N
Y
CS/R
Severinsky
et.al.
[18]
(2014)
Irregular
astigmatism
post-
PK
Not
cultured
Unknown
Unknown
Unknown
Authors
report
poor
lens
compliance
CS/R
Severinsky
et.al.
[18]
(2014)
Irregular
astigmatism
post-
PK
Not
cultured
Unknown
Unknown
Unknown
Authors
report
poor
lens
compliance
CS/R
Fernandes
et.al.
[19]
(2013)
OCP
&
SS
Staph.
epidermidis,
Corynebacterium
accolens,
&
Microsporidia
Failed
graft
Y
N
Known
epi
defect
at
time
of
infection
CR/R
Farhat
&
Sutphin
[20]
(2014)
GVHD
Acanthamoeba
DALK
performed
Y
Y
CR/R
Zimmerman
&
Marks
[21](2014)
Neurotrophic
keratitis
2^
HSK
Unable
to
determine
on
culture
Resolved
with
antibiotic
treatment
N
Y
Authors
report
poor
compliance
CR/R
a
PED:
persistent
epithelial
defect;
PK:
penetrating
keratoplasty;
OCP:
ocular
cicatricial
pemphigoid;
SS:
sjogren’s
synrome;
HSK:
herpes
simplex
keratitis
GVHD:
graft
vs.
host
disease;
DALK:
Decemet’s
anterior
lamellar
keratoplasty.
b
CR:
single
case
report;
CS:
case
series;
R:
retropective.
M.K.
Walker
et
al.
/
Contact
Lens
&
Anterior
Eye
39
(2016)
88–96
89

searched
on
PubMed
between
November
2014
and
April
2015.
Keywords
included
“scleral
contact
lens;
complications;
hypoxia;
infection;
inflammation.”
Ultimately;
the
search
revealed
a
total
of
33
articles
that
address
complications
and
limitations
of
the
use
of
ScCL.
1.3.
History
of
scleral
contact
lens
complications
As
mentioned
earlier,
hypoxia
was
the
primary
cause
of
complications
associated
with
the
wearing
of
glass
and
PMMA
ScCL.
In
1995,
Tan
et
al.
reported
on
a
total
of
517
eyes
wearing
low
Dk
ScCL
(primarily
PMMA)
between
1988
and
1993;
they
found
the
most
common
complications
to
be
neovascularization
(13.3%)
and
corneal
edema
(7.4%)
secondary
to
corneal
hypoxia.
Additionally,
less
common
complications
included
corneal
abrasion
(3.1%)
and
giant
papillary
conjunctivitis
(1.7%)
[15].
One-hundred
eighteen
of
the
eyes
from
the
original
cohort
were
re-fitted
into
GP
ScCL
to
allow
oxygen
diffusion
through
the
lens,
and
the
improved
outcomes
were
described
in
a
second
paper
[17].
The
complica-
tions
related
to
corneal
hypoxia
were
significantly
reduced;
however,
these
lenses
brought
with
them
a
new
set
of
problems
such
as
susceptibility
to
lens
deposits,
breakage,
and
poor
surface
wetting
characteristics
[17].
The
development
of
more
advanced
GP
materials
and
manufacturing
techniques
continues
to
evolve,
steadily
improving
the
clinical
performance
of
ScCLs.
Therefore,
this
review
will
focus
on
complications
reported
in
wearers
of
modern
high
Dk
ScCL
designs.
2.
Complications
of
scleral
contact
lens
wear
2.1.
Infection-related
complications
As
the
prevalence
of
ScCL
use
increases,
we
are
beginning
to
observe
an
increase
in
the
reported
infectious
complications
associated
with
their
use.
Many
of
these
infections
are
seen
in
the
presence
of
a
compromised
corneal
surface,
as
well
as
with
the
use
of
immunosuppressive
therapy
[16,18–22].
Table
1
summarizes
the
published
reports
of
serious
infectious
complications
seen
with
modern
ScCL
in
the
past
15
years.
There
are
common
risk
factors
for
developing
an
infection
while
wearing
a
ScCL.
In
all
except
for
one
of
the
cases
reviewed,
the
patients
had
ocular
surface
disease,
which
in
itself
carries
an
increased
risk
for
microbial
keratitis
[23].
It
is
possible
that
all
of
the
documented
cases
of
infection
occurred
in
the
presence
of
epithelial
compromise
that
acted
as
an
entry
site
for
invading
microorganisms,
although
it
is
not
specified
in
all
of
the
publications.
Further,
almost
all
of
the
reports
were
of
individuals
taking
oral
and/or
topical
corticosteroids
to
manage
their
underlying
condition
(reducing
the
immune
protection
from
invading
organisms).
This
risk
is
further
elevated
when
the
lenses
are
not
being
stored
and
cleaned
properly
[19,22].
There
is
an
overall
low
incidence
of
infectious
events
in
ScCL
wearers,
which
is
likely
due
to
multiple
factors.
First,
it
is
estimated
that
approximately
70,000
individuals
in
the
US
are
wearing
a
ScCL
device
[24];
this
is
a
small
population,
compared
to
the
nearly
30
million
people
wearing
commercially
available
contact
lenses.
Given
the
relatively
small
number
of
ScCL
wearers,
incidence
rates
will
be
low
even
if
infectious
incidents
are
occurring
at
an
equal
or
increased
rate
than
with
other
contact
lens
devices.
Further,
these
lenses
are
prescribed
to
be
worn
during
the
day
only,
with
rare
occurrences
of
overnight
wear
–
a
strong
risk
factor
for
contact
lens
related
infections
[25,26].
Finally,
we
expect
that
the
compliance
rate
in
terms
of
lens
hygiene
is
greater
in
patients
wearing
ScCL
than
with
other
lens
modalities,
as
ScCL
patients
often
rely
on
careful
ocular
hygiene
due
to
their
underlying
ocular
disease
state,
thus
are
perhaps
more
diligent
than
the
general
population
in
regards
to
lens
care
compliance.
As
ScCLs
continue
to
gain
popularity
amongst
practitioners,
the
incidence
of
infections
is
likely
to
increase.
Practitioners
should
take
specific
caution
when
fitting
patients
with
ScCL
who
are
known
to
have
epithelial
compromise
and/or
taking
immunosup-
pressive
therapy.
Prophylactic
antibiotics
should
be
considered
in
these
individuals
[27],
and/or
an
alternative
to
corticosteroid
treatment
if
available.
2.2.
Inflammation-related
complications
There
are
few
publications
that
specifically
cite
inflammatory
responses
in
ScCL
wearers.
One
case
report
describes
non-
infectious
infiltrative
keratitis
in
a
keratoconus
patient
wearing
a
ScCL,
and
another
reports
conjunctival
hyperemia
post-lens
removal,
which
may
have
an
inflammatory
etiology
[28,29].
Beyond
these
two
case
reports
there
have
been
no
publications,
to
our
knowledge,
that
specifically
cite
inflammation
as
a
cause
of
ScCL
complications,
or
systematically
assesses
this
potential
response
in
ScCL
wear.
However,
studies
have
reported
a
number
of
subjects
who
discontinue
lens
wear
due
to
discomfort—about
ten
percent
of
patients
according
to
two
separate
studies
[19,30].
We
suspect
that
inflammation
may
be
under-reported
in
the
literature.
Our
clinical
experience
has
shown
us
that
there
are
individuals
who
experience
discomfort,
redness,
or
other
inflam-
matory-related
responses
to
ScCLs.
To
mitigate
these
responses,
the
lens
parameters
can
be
adjusted
(i.e.,
adjusting
the
peripheral
curves
to
minimize
lens
bearing,
increasing
lens
diameter).
However,
it
is
not
always
successful—in
a
report
of
a
patient
who
developed
infiltrative
keratitis
during
ScCL
wear,
the
authors
increased
vault
in
an
attempt
to
dilute
endotoxin
buildup,
which
was
unsuccessful
at
decreasing
the
inflammatory
response
[28].
Situations
of
inflammation
can
result
in
the
discontinuation
of
ScCL
wear,
although
often
times
mild
inflammatory
responses
are
overshadowed
by
the
positive
effects
of
the
lenses
on
a
patient's
quality
of
life.
Due
to
the
increasing
application
of
the
ScCL
modality,
as
well
as
the
gradual
expansion
into
the
mainstream
contact
lens
market,
we
expect
to
see
an
increase
in
reports
of
inflammatory-based
complications
in
the
future.
2.3.
Hypoxia-related
complications
The
basic
design
philosophy
when
fitting
a
ScCL
is
to
vault
over
the
cornea,
creating
a
post-lens
tear
reservoir
between
the
lens
and
the
cornea
that
is
relatively
thick
compared
to
other
lens
modalities
(100–300
um
thick
in
ScCL
compared
to
approximately
30
um
thick
beneath
traditional
GP
lenses)
[31].
It
then
follows
that
it
is
important
to
consider
the
oxygen
transmissibility
of
this
lens
system
–
the
lens
and
the
tear
reservoir
–
when
assessing
the
effective
hypoxia
induced
by
a
ScCL.
The
corneal
response
to
hypoxia
is
a
complex
cascade
of
events
resulting
from
the
lack
of
oxygen
availability
at
the
anterior
surface
of
the
eye.
The
cascade
begins
with
epithelial
release
of
lactic
acid,
a
byproduct
of
the
anaerobic
cellular
metabolic
process
that
cells
are
forced
into
during
a
period
of
reduced
oxygen
availability.
The
release
of
lactic
acid
into
the
corneal
stroma
affects
the
osmotic
balance,
and
leads
to
a
greater
than
normal
amount
of
fluid
in
the
stroma
[32–34].
This
process
occurs
in
the
normal
non-contact
lens-wearing
eye
overnight
due
to
the
closed
eyelids—the
average
overnight
corneal
swelling
is
about
4.5%
with
most
recovering
within
an
hour
of
awakening
[35].
Graham
et
al.
recorded
a
corneal
swelling
response
of
5.09%
in
subjects
wearing
92
Dk
gas
permeable
corneal
contact
lenses
overnight
[36].
The
presence
of
vertical
striae,
an
early
clinical
indication
of
corneal
swelling
in
soft
lens
wearers,
was
found
to
occur
when
the
mean
corneal
90
M.K.
Walker
et
al.
/
Contact
Lens
&
Anterior
Eye
39
(2016)
88–96

edema
was
6.89%
[37].
When
the
stroma
swells
approximately
10%
or
greater
than
normal,
the
cornea
may
begin
to
become
hazy,
and
may
result
in
structural
changes
to
the
endothelium,
if
present
chronically.
Modern
ScCL,
manufactured
in
high
Dk
materials,
rarely
provoke
frank
corneal
edema;
however,
recent
studies
suggest
that
there
may
be
edema
occurring
at
a
subclinical
level
[38–40].
The
long-term
effect
of
low-grade
physiological
edema
on
a
daily
basis
has
yet
to
be
documented,
but
we
predict
it
to
be
benign.
This
level
of
edema
may
cause
changes
to
the
endothelial
mosaic,
if
present
chronically,
although
the
clinical
implications
of
endothelial
polymegethism
has
yet
to
be
determined
[41].
Investigators
have
begun
to
address
the
effects
of
a
ScCL
system
on
corneal
oxygen
availability.
Smith
et
al.
described
the
earliest
report
of
corneal
swelling
with
contemporary
ScCL
materials
in
2004,
however
the
study
addressed
this
response
in
the
overnight
wear
of
theses
lenses
[42].
Based
on
a
theoretical
model
developed
by
Michaud
et
al.
in
2012,
the
post-lens
tear
layer
should
be
no
greater
than
200um
in
order
to
avoid
corneal
edema
using
a
high
Dk
(>150)
lens
with
a
maximum
central
thickness
of
250
um
[39].
Jaynes
et
al.,
using
a
different
theoretical
model,
also
arrived
at
similar
conclusions,
reporting
that
ScCLs
should
be
manufactured
in
the
highest
available
Dk
material
and
fitted
with
minimal
tear
reservoir
depth
in
order
to
avoid
hypoxia
[43].
In
a
separate
study,
Compañ
et
al.
calculated
that
in
order
to
avoid
corneal
edema,
a
200
um
thick
scleral
contact
lens
must
be
manufactured
with
a
Dk
of
at
least
125
Dk,
and
fitted
with
a
corneal
vault
of
no
greater
than
150
um
[38].
This
study
also
had
a
clinical
component;
subjects
were
fitted
with
15.5
mm,
100
Dk
material
ScCL,
with
a
central
post-lens
tear
film
thickness
of
150
um
or
350
um.
The
study
showed
1.6%
corneal
swelling
in
the
shallow
tear
reservoir
group,
and
3.9%
swelling
in
the
subjects
that
were
fitted
with
a
deeper
reservoir,
after
3
h
of
lens
wear.
This
magnitude
of
swelling
is
within
the
range
of
physiological
corneal
swelling
that
occurs
during
closed
eye
conditions,
such
as
sleep
[35,44].
Similar
findings
were
reported
in
another
clinical
study,
in
which
the
subjects
were
fitted
with
ScCL
that
were
manufactured
from
3
different
materials
with
Dk
values
of
32,
59,
and
115 ,
in
thicknesses
of
0.15,
0.30,
0.60,
and
1.20
mm
[45].
It
was
found
that
a
0.6
mm
thick
lens
with
a
Dk
of
115
induced
central
corneal
swelling
of
less
than
3%.
There
is
little
evidence
that
a
clinically
significant
corneal
edematous
response
is
provoked
when
wearing
modern
high
Dk
material
ScCLs.
In
the
Michaud
et
al.
theoretical
study,
the
authors
acknowledged
that
there
are
no
reports
to
provide
clinical
evidence
in
support
of
their
theoretical
calculations,
although
this
may
be
because
the
ScCL
wearing
population
is
relatively
small
compared
to
other
contact
lens
modalities.
To
our
knowledge,
there
is
only
one
case
report
that
specifically
describes
a
situation
in
which
a
ScCL
patient
experienced
corneal
edema
during
daily
wear.
The
authors
describe
a
keratoglobus
patient
with
less
than
100um
of
tear
film
thickness
(Dk
of
lens
unknown)
that
experienced
significant
corneal
edema
(6.8%)
over
a
6
hour
wear
period
[29].
It
is
unknown
if
there
were
confounding
factors
in
this
case
which
led
to
the
induction
of
edema
during
ScCL
wear.
It
has
been
reported
that
keratoglobus
can
be
associated
with
endothe-
lial
disease,
which
may
provoke
corneal
swelling
[46].
Studying
the
edematous
corneal
response
in
ScCL
wear
is
difficult
to
control
because
of
two
major
variables.
First,
the
availability
of
oxygen
to
the
cornea
is
dependent
on
the
amount
of
tear
exchange
occurring
beneath
a
ScCL.
While
most
ScCL
experts
suggest
that
there
is
minimal
tear
exchange
occurring
beneath
a
ScCL,
the
exchange
that
occurs
has
yet
to
be
quantified,
and
may
be
variable
due
to
asymmetric
scleral
anatomy
that
is
unique
to
each
eye
and
sometimes
variable
within
each
quadrant
of
an
eye
[31,47–49].
Secondly,
oxygen
availability
also
depends
on
the
level
of
tear
mixing
that
occurs
beneath
the
lens,
which
to
our
knowledge
has
also
not
been
documented
in
ScCL
wearers.
The
eminent
late
corneal
and
contact
lens
physiologist,
Iving
Fatt,
believed
the
sub-lens
tear
mixing
to
be
an
important
and
helpful
factor
in
the
success
of
ScCL
wear
[50].
Perhaps
the
greatest
challenge
in
studying
these
two
oxygen
availability
predictors
is
that
the
inter-subject
variability
in
lens
ScCL
fitting
characteristics
is
broad,
making
it
difficult
to
determine
a
universally
applicable
tear
exchange
model.
An
additional
variable
that
complicates
the
oxygen
availability
measurements
is
the
depth
of
the
postlens
tear
film,
which
show
a
large
amount
of
inter
and
intra-subject
variability.
Not
only
can
apical
tear
film
reservoir
depths
range
between
50
and
500um
in
the
ScCL
wearing
population,
but
also
beneath
a
single
lens
there
are
wide
variations
in
tear
reservoir
depth
across
the
corneal
surface
(especially
in
highly
irregular
corneas
with
large
corneal
elevation
variability).
The
understanding
of
hypoxia
associated
with
a
ScCL
is
incomplete,
and
although
there
does
not
appear
to
be
clinically
significant
edema
occurring
amongst
ScCL
wearers,
there
may
be
low
grade
hypoxic
effects
that
have
yet
to
manifest.
Investigations
exploring
the
effects
of
long-term
ScCL
wear
on
the
endothelium
are
indicated,
specifically
in
those
patients
with
decreased
endothelial
functionality
by
virtue
of
the
underlying
conditions
and/or
as
a
consequence
of
surgery.
Furthermore,
it
is
not
unreasonable
to
suspect
that
a
chronic
low-grade
hypoxic
state
may
induce
factors
that
promote
corneal
neovascularization
[51].
Despite
the
uncertainties
in
regard
to
the
effects
of
reduced
oxygen
to
the
cornea
during
ScCL
wear,
medical
management
with
ScCLs
involves
a
balance
of
risk
versus
benefit.
There
may
be
chronic
damage
to
the
cornea
occurring
during
lens
wear,
but
most
of
these
individuals
rely
on
the
lenses
for
usable
vision
and
functionality
in
their
daily
lives.
Further,
the
relatively
hypoxic
effects
may
be
slow
in
progression
and
insignificant
in
consider-
ation
of
the
lifespan
of
the
corneal
tissue.
Further
studies
are
suggested
to
more
completely
explore
this
issue.
3.
Fitting
challenges
associated
with
scleral
contact
lenses
3.1.
The
asymmetric
sclera
The
scleral
surface
is
highly
asymmetric.
Several
groups
have
measured
this
asphericity
in
order
to
improve
landing
zone
design,
and
practitioners
are
more
frequently
designing
toric
haptic
zones
in
an
effort
to
reduce
meridional
lens
impingement
due
to
scleral
toricity
[52,53].
In
a
retrospective
analysis
of
43
subjects,
Visser
et
al.
found
an
increase
in
wearing
time
and
comfort
in
subjects
wearing
ScCLs
with
a
toric
haptic,
due
to
the
more
balanced
distribution
of
lens
bearing
on
the
sclera
[54].
Unfortunately,
the
shape
of
the
sclera
typically
does
not
exhibit
regular
astigmatism,
but
instead
is
considerably
more
complex.
Hall
et
al.
looked
at
the
corneoscleral
topography
of
408
eyes
using
OCT,
and
found
that
the
corneoscleral
junction
(the
angle
at
the
transition
of
the
cornea
and
the
sclera)
was
significantly
different
in
the
four
major
quadrants.
They
found
that
the
“sharpest”
corneoscleral
angle
was
nasal,
followed
by
temporal,
inferior,
and
superior,
respectively
[47].
Tan
et
al.
arrived
at
similar
conclusions,
finding
a
“more
pronounced”
corneoscleral
junction
in
the
nasal
quadrant,
followed
by
the
inferior,
superior,
then
temporal
quadrants
[48].
A
sharp
corneoscleral
junction
angle
indicates
a
relatively
flat
radius
of
curvature
of
the
sclera
as
it
approaches
the
cornea
in
the
nasal
quadrant,
when
compared
to
the
other
three
quadrants.
This
is
exactly
what
was
found
in
studies
that
looked
at
the
radius
of
curvature
of
the
sclera.
Choi
et
al.
found
that
the
average
curvature
of
the
nasal
sclera
(13.33
mm)
was
flatter
than
the
temporal
sclera
(12.32
mm)
[49].
Similarly,
Tan
et
al.
determined
that
the
temporal
sclera
had
the
steepest
radius
of
curvature
[48].
As
such,
one
might
M.K.
Walker
et
al.
/
Contact
Lens
&
Anterior
Eye
39
(2016)
88–96
91

expect
an
elevation
map
to
show
the
nasal
sclera
as
“higher”
than
the
other
quadrants,
and
the
temporal
scleral
“lower”,
at
an
equivalent
chord.
This
height
difference
may
explain
the
frequent
temporal
lens
decentration
that
is
often
observed
by
practitioners
(Fig.
1),
as
the
lens
will
land
first
nasally,
and
be
pushed
toward
the
less
resistant
(steeper
curvature)
temporal
ocular
surface.
ScCLs
also
have
a
natural
tendency
to
displace
inferiorly
due
to
gravity
and
the
blinking
force
exerted
by
the
upper
eyelid.
When
the
sclera
is
highly
asymmetric,
unequal
weight
bearing
of
the
lens
can
occur
and
induce
sectorial
impingement
and
compression
of
the
conjunctiva.
Impingement
Compression
of
the
conjunctiva
to
the
point
where
the
blood
vessels
are
closed
off
impinged
is
an
undesirable
outcome,
and
will
have
an
effect
on
wearing
time
and
comfort
[54,55].
Distribution
of
the
weight
of
the
lens
around
the
entire
circumference
of
the
eye
should
be
the
goal
in
ScCL
fitting.
However,
the
perfect
fit
may
create
a
peripheral
seal
that
will
not
permit
adequate
exchange
of
tears
in
some
individuals,
so
a
practitioner
must
determine
the
appropriate
fitting
approach
for
each
patient.
3.2.
Lens
seal-off
Lens
seal-off
can
become
a
serious
problem
for
many
individuals
wearing
ScCL.
We
refer
to
“seal-off”
as
strong
suction
of
the
lens
to
the
eye,
creating
difficulty
with
lens
removal
and
restricting
tear
exchange
beneath
the
lens.
Even
with
ScCL
fit
to
clinical
standards,
tear
exchange
appears
to
be
quite
reduced
when
compared
to
traditional
rigid
contact
lenses.
Therefore,
a
complete
or
nearly
complete
adherence
of
a
ScCL
would
create
a
substantial
reduction
in
tear
exchange
that
would
produce
a
stagnation
of
the
post
lens
tear
reservoir,
exposing
the
cornea
to
toxic
metabolic
waste
[19].
It
is
our
opinion
that
certain
eyes
appear
more
prone
to
lens
adhesion,
which
can
induce
complications
during
lens
removal.
Eyes
which
may
be
at
particular
risk
include
post-RK,
LASIK,
and
PKP/LKP,
where
the
oblate
corneal
shape
exacerbates
the
suction
force
of
the
lens
on
eye
from
blinking
or
by
forces
exerted
by
the
plunger
during
lens
removal;
in
these
individuals,
there
is
an
increased
risk
for
trauma
or
rupture
of
the
globe
at
the
corneal
incision
or
the
host/donor
interface
sites
during
removal
due
to
biomechanical
weakening
of
the
stroma
after
surgery.
For
instance,
several
years
after
radial
keratectomy
surgery,
the
lamellae
at
incision
sites
remain
severed,
with
only
a
disorganized
collagen
matrix
and
epithelial
cells
closing
the
wound
[56].
Further,
it
is
known
that
donor
buttons
in
PKP
can
suffer
wound
dehiscence
many
years
after
keratoplasty
[57].
Beyond
the
hindrance
of
difficulty
with
lens
removal,
the
effect
that
seal-off
has
on
susceptibility
to
infection,
inflammation
and
oxygen
availability
are
potentially
significant.
Some
practitioners
acknowledge
the
potential
dangers
of
seal-off,
and
advocate
mid-
day
removal
of
ScCLs
in
order
to
avoid
ocular
surface
compromise
[19,58].
3.3.
Conjunctival
prolapse
Conjunctival
prolapse,
also
known
as
hooding
or
chalasis,
occurs
when
the
perilimbal
conjunctival
tissue
migrates
beneath
the
peripheral
confines
of
a
ScCL,
sometimes
adhering
to
the
peripheral
cornea
[59,60].
This
occurs
due
to
the
negative
pressure
forces
beneath
a
lens,
which
pull
the
malleable
perilimbal
conjunctival
tissue
onto
the
peripheral
cornea,
particularly
in
areas
of
relative
corneal
depression
[59].
This
complication
of
ScCL
wear
is
rarely
mentioned
in
the
published
literature.
One
study
does
acknowledge
its
presence
in
their
patient
population,
Fig.
1.
An
image
of
a
scleral
lens
on
a
right
eye.
Areas
of
bright
fluorescence
designate
areas
of
relatively
deep
tear
film
reservoir,
and
the
dark
band
(arrow)
in
the
superior
nasal
quadrant
shows
close
apposition
or
‘touch’
of
the
scleral
lens.
Fig.
2.
(A)
Peripheral
conjunctival
prolapse
(white
arrows)
in
the
inferior
temporal
quadrant
of
a
right
eye,
seen
after
removal
of
the
scleral
lens.
(B)
The
same
area
of
the
cornea
after
recession
of
the
prolapse.
A
yellow
arrow
designates
the
border
of
the
previously
adhered
conjunctival
tissue,
which
appears
opaque.
Neovascularization
of
the
area
beneath
the
previously
adhered
conjunctival
tissue
is
apparent
(black
arrows).
“
(For
interpretation
of
the
references
to
color
in
this
figure
legend,
the
reader
is
referred
to
the
web
version
of
this
article.)
92
M.K.
Walker
et
al.
/
Contact
Lens
&
Anterior
Eye
39
(2016)
88–96

reporting
such
folds
in
the
conjunctiva
in
1
out
of
a
sample
of
33
eyes
[19].
Other
than
cosmetics,
potential
consequences
of
this
occur-
rence
are
not
well
understood.
It
should
be
noted,
however,
that
when
the
conjunctival
tissue
adheres
to
the
cornea
for
extended
periods
of
time,
vascularization
and
scarring
of
the
underlying
limbus
and
peripheral
cornea
have
been
observed
(Fig.
2).
It
is
perhaps
prudent
to
avoid
a
fitting
relationship
in
which
a
prolapse
occurs,
by
decreasing
clearance,
specifically
in
the
limbal
zone,
to
create
a
more
uniform
shaped
tear
film
reservoir.
3.4.
Limbal
bearing
The
limbal
stem
cells
have
a
well-established
role
in
the
renewal
and
proliferation
of
the
corneal
epithelium
[61].
Avoiding
disturbance
of
the
important
limbal
epithelium
is
prudent,
and
also
heavy
bearing
in
this
region
with
a
high
density
of
sensory
nerve
endings
is
likely
to
generate
discomfort.
Subepithelial
fribrosis
has
been
documented
in
an
area
of
lens
bearing
at
the
graft/host
interface
in
a
PKP
patient
[19].
Our
clinical
observations
have
shown
the
breakdown
of
epithelium
in
the
presence
of
harsh
limbal
touch
(Fig.
3),
although
it
should
be
noted
that
tissue
breakdown
does
not
occur
in
all
cases
of
peripheral
lens
bearing.
It
is
important
to
monitor
areas
of
limbal
bearing,
especially
if
they
cannot
be
reduced
or
avoided
with
lens
parameter
changes.
Damage
to
the
peripheral
corneal
tissue
has
the
potential
to
lead
to
limbal
stem
cell
deficiency
and
re-epithelialization
of
the
cornea
by
conjunctival
cells
[62].
As
mentioned
previously,
ScCLs
frequently
decenter
inferior-
temporally,
and
this
often
times
results
in
superior-nasal
limbal
lens
bearing
(Fig.
1).
It
is
important
to
monitor
for
epithelial
and
anterior
stromal
changes
in
areas
of
limbal
lens
bearing.
However,
in
some
corneas
a
small
area
of
touch
can
be
very
difficult
to
avoid
without
worsening
the
lens
fit
elsewhere.
For
this
reason,
in
our
clinic
we
often
tolerate
lens
touch
when
it
is
20%
or
less
of
the
limbal
circumference.
3.5.
Mid-day
fogging
One
of
the
most
common
ScCL
complications
is
“mid-day
fogging”
(MDF),
when
particulate
matter
accumulates
in
the
tear
reservoir
between
the
contact
lens
and
cornea,
creating
a
fog-like
blur
in
20-33%
of
individuals
[63–67]
(Fig.
4).
MDF
can
occur
promptly
following
the
application
of
lenses,
or
progress
gradually
over
the
course
of
the
wear
cycle.
The
debris
accumulation
can
cause
a
significant
visual
blur
effect,
necessitating
lens
removal
to
refill
the
shell
with
fresh
solution.
For
some
patients,
this
becomes
a
daily
routine
that
is
repeated
multiple
times.
The
origin
of
this
particular
complication
is
unknown,
as
is
whether
its
presence
poses
a
risk
to
already
compromised
corneas.
However,
it
does
Fig.
3.
(A)
A
ScCL
exhibiting
circumlimbal
lens
bearing.
Fluorescein
was
instilled
into
the
lens
chamber
prior
to
application
to
highlight
the
areas
of
lens
bearing
(dark
banding).
(B)
After
lens
removal,
positive
staining
is
observed,
signifying
epithelial
breakdown
in
the
location
of
lens
bearing.
Images
courtesy
of
Patrick
Caroline
at
Pacific
University.
Fig.
4.
(A)
An
optic
section
shows
the
scleral
lens
on
eye
with
a
post
lens
tear
film
(yellow
arrow)
filled
with
particulate
matter.
Images
B,
C,
&
D
are
optical
coherence
tomography
(OCT)
cross-sectional
images
that
show
the
scleral
lens
on
eye,
with
progressive
opacification
of
the
tear
film
reservoir
(white
arrows)
over
an
eight
hour
period.
Images
courtesy
of
Patrick
Caroline
at
Pacific
University.
“
(For
interpretation
of
the
references
to
color
in
this
figure
legend,
the
reader
is
referred
to
the
web
version
of
this
article.)
M.K.
Walker
et
al.
/
Contact
Lens
&
Anterior
Eye
39
(2016)
88–96
93

appear
that
the
debris
responsible
for
turbidity
has
a
lipid
component,
originating
through
or
directly
from
the
perilimbal
conjunctival
environment
[67],
and
is
more
common
in
patients
with
dry
eye
and
inflammatory
conditions
[66,68].
It
is
important
to
make
a
differential
diagnosis
between
MDF
and
frank
stromal
or
epithelial
edema,
since
patients
complaining
of
foggy
vision
may
be
experiencing
edema
rather
than
debris
accumulation,
and
this
should
be
ruled
out
by
the
practitioner.
The
MDF
phenomenon
has
been
discussed
at
various
confer-
ences,
but
unfortunately
peer-reviewed
literature
is
lacking
information
on
its
etiology
and
prevalence.
However,
there
have
been
retrospective
case
analyses
that
have
described
events
similar
to
MDF.
A
study
of
pediatric
patients
wearing
ScCLs
found
that
debris
accumulation
beneath
the
ScCL
occurred
in
up
to
70%
of
patients,
with
almost
half
of
those
experiencing
greater
than
2
lines
decreased
visual
acuity
[63].
Another
study,
at
UC
Davis,
reports
only
5%
of
patients
complaining
of
excessive
debris,
although
they
also
report
a
25%
drop
out
rate
due
to
visual
dissatisfaction,
which
may
have
been
related
to
MDF
[30].
In
our
clinical
experience,
MDF
may
be
managed
by
using
high
viscosity,
ion
containing,
preservative
free
artificial
tears
to
fill
the
ScCL,
rather
than
plain
preservative
free
saline
solution.
The
mechanism
by
which
this
reduces
fogging
in
some
individuals
is
unknown
–
it
is
possible
that
it
is
related
to
the
nutritious
ion
presence,
physiological
osmolality,
or
the
high
viscosity
of
the
artificial
tears.
In
addition,
we
have
found
that
adjusting
the
lens
design
to
create
a
thinner,
uniform
(plano
lens
shape)
post-lens
tear
reservoir
is
also
helpful
in
decreasing
the
occurrence
of
MDF.
However,
creating
uniformity
of
the
tear
reservoir
can
be
difficult
to
achieve,
particularly
in
highly
irregular
corneas.
The
presence
of
MDF
appears
to
be
multi-factorial,
with
a
number
of
variables
affecting
the
clinical
outcome.
For
instance,
anterior
ocular
surface
shape,
natural
tear
film
composition,
and
contact
lens
design
all
seem
to
play
a
role
in
the
occurrence.
There
is
a
need
for
further
research
into
this
unique
ScCL
complication,
to
explore
the
etiology
and
develop
an
effective
solution
to
the
problem.
We
regard
this
complication
as
a
limitation
and
not
a
contraindication
to
continued
ScCL
wear.
3.6.
Epithelial
bogging
After
removal
of
a
ScCL,
there
are
often
irregularities
noted
in
the
epithelial
surface
of
the
cornea,
those
which
were
not
present
prior
to
ScCL
wear
(Fig.
5).
To
our
knowledge
this
has
not
been
documented
in
the
peer-reviewed
literature,
although
clinical
observation
has
led
us
to
address
its
occurrence.
We
refer
to
it
as
‘epithelial
bogging’
due
to
the
waterlogged
appearance
of
the
cornea
during
biomicroscopic
evaluation
with
fluorescein,
and
we
often
observe
it
in
patients
after
a
few
days
of
ScCL
wear.
We
hypothesize
that
there
is
a
compromise
to
the
epithelium
due
to
the
prolonged
submersion
of
the
cornea
in
non-nutritious
saline
solution
during
lens
wear.
It
may
represent
epithelial
edema,
loss
of
the
glycocalyx
layer
leading
to
incomplete
ocular
surface
wetting,
or
an
osmotic
imbalance
of
the
tears.
Additionally,
the
lack
of
lid
shearing
forces
that
normally
compress
the
epithelium
with
each
blink
may
allow
for
a
buildup
of
non-vital
epithelial
cells
that
would
otherwise
slough
off
throughout
the
day.
Current
evidence
suggests
that
epithelial
bogging
does
not
have
long-term
effects
on
corneal
health,
although
further
exploration
of
the
phenomenon
is
indicated.
4.
Conclusion
Like
other
advancements
in
contact
lens
modalities,
the
ScCL
has
brought
with
it
the
potential
for
complications
and
a
new
set
of
fitting
limitations.
However,
there
is
no
doubt
that
the
re-
emergence
of
these
lenses
has
revolutionized
the
specialty
contact
lens
options
available
to
treat
corneal
and
ocular
surface
diseases.
Interestingly,
the
increasing
application
of
ScCL
therapy
has
seen
a
broadening
of
its
utilization
to
include
those
with
high
refractive
error
and
astigmatism,
in
other
words
patients
with
otherwise
healthy
ocular
surfaces
are
benefitting
from
ScCL
use
[69,70].
This
review
attempted
to
summarize
the
complications
and
challenges
of
which
we
are
aware
within
the
ScCL
field
today.
Midday
fogging,
epithelial
bogging,
and
associated
inflammatory
responses,
all
potentially
related
to
tear
exchange
beneath
the
lens,
seem
to
be
the
most
challenging
complications
and
are
likely
to
be
multifactorial
in
nature.
Fortunately,
infection
rates
do
not
appear
to
be
greater
in
ScCL
wearers
than
in
other
contact
lens
modalities,
and
we
have
yet
to
observe
acute,
vision
interfering
complications
related
to
oxygen
deprivation.
There
is
a
great
need
for
clinical
and
basic
research
in
the
field
of
ScCL,
to
resolve
the
complications
that
our
patients
wearing
these
devices
currently
experience.
With
increased
understanding
of
the
causes
and
consequences
of
the
complications
associated
with
ScCL
wear
will
come
new
lens
technologies
and
fitting
strategies.
The
improved
devices
will
in
turn
enhance
clinical
outcomes
and
expand
the
clinical
population
of
patients
that
will
benefit
from
their
use.
Acknowledgements
The
authors
would
like
to
acknowledge
Dr.
Richard
Pearson
for
his
guidance
and
assistance
in
the
contact
lens
history
section.
Additionally,
we
would
like
to
thank
Professor
Patrick
Caroline
for
the
use
of
select
images.
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