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Essential Contact Lens Practice
Medical Ltd
Overnight
Wear
key points
Key Points
The risks and benefits of
overnight wear should be
discussed between the
patient and practitioner
to help enable an informed
choice to be made
Although the absolute risk of
developing a serious adverse
reaction to overnight wear
is small, the relative risk in
comparison to daily wear is
significant with all lens types
including silicone hydrogel
lenses
Patient selection and
lens trial is more critical.
Overnight wear lenses should
only be considered for ideal
contact lens patients
It is critical that extended
and continuous wear patients
are carefully and frequently
monitored throughout their
contact lens wearing life,
with regular aftercare checks
All overnight wear patients
should be instructed to
self-monitor their eyes
daily, and to understand the
procedures to follow should
any variations from the norm
be observed
Ever since contact lenses were first fitted, some
patients have either chosen to, or been advised
by their practitioner to sleep in them.
Many of the first glass haptic lenses fitted by,
for example, the Mullers in the 1880s, were worn
for up to two years at a time, and the literature contains many reports of patients wearing
both haptic and hard corneal lenses on an extended wear basis prior to 1974.1 It was John de
Carle, working in London, who first popularised
hydrogel overnight wear with the Permalens. In
1981 hydrogel extended wear was approved by
the Food and Drug Administration (FDA) in the
US for cosmetic correction and the aggressive
advertising and popularity of this modality led
to its widespread acceptance in the US. For the
purpose of this article, extended wear (EW) refers to six nights of continuous wear followed
by a night of no lens wear, and continuous wear
(CW) as up to 30 nights followed by a night of
no lens wear.
Overnight Wear
Essential Contact Lens Practice
It is now well established that lack of oxygen to the eye leads
to corneal swelling (oedema). During normal closed eye sleep
the cornea swells by an average of up to 4 percent. It is capable,
however, of recovering 8 percent of swelling during the day
and this became the target for hydrogel lenses.
The landmark study by Holden and Mertz in 1984 defined the
2
levels of oxygen needed to avoid corneal oedema (Table 1).
Further studies have shown the inability of the EW hydrogel
lenses fitted at that time to meet these needs. While hydrogel
materials are unable to achieve the criteria of zero additional
swelling with overnight wear, some come close to the 8 percent
level (zero residual swell) and gained regulatory approval for
overnight wear. More recent research by Harvitt and Bonanno
define the Dk/t levels as 35 and 125 for daily and overnight wear
3
respectively.
Modern rigid gas-permeable lenses (RGPs) and silicone
hydrogels (Si-Hy) allow sufficient oxygen to the eye to meet
the zero additional swelling criteria (Table 2). Nevertheless, it
is important to remember the closed eye environment differs
from the normal open eye in several key factors (Table 3).
As well as the issue of corneal hypoxia, early non-disposable
hydrogel CW was also associated with more inflammatory
reactions due to long-term deposit build up, and toxic
reactions due to the intensive cleaning procedures required
after 30 nights of wear. The introduction of weekly replaced
disposable lenses in 1987 resolved these two issues. These
lenses were worn for six continuous nights of overnight wear
and referred to as ‘extended wear’.
0 % D W ≤ 4 % o v e r n i g h t 0 % o v e r n i g h t
oedem a
o e d e m a w e a r r e s i d u a l oedema
Critical Dk/t (avg)
(x10 -9) @20 0C
Critical EOP
(% atmospheric O2)
2
24.1
87.0
34.3
9.9
17.9
12.1
TablE 1
Critical corneal oxygen requirements
N o l e n s E ta f i l c o n AB a l a f i l c o n AS e n o f i l c o n AL o t r a f i l c o n A
Dk/t = 3 1
Dk/t = 1 10
Dk/t = 1 47
Dk/t = 175
% Mean corneal swelling (± SD))
0.77
(± 3.40)
5.83*
(± 3.83)
1.35
(± 2.95)
1.40
(± 3.64)
1.22
(± 3.83)
TablE 2
Average corneal swelling after removal after eight hours of overnight wear
* p < 0.001
Closed-eye environment
Available oxygen drops from 155mmHg (atmospheric)
to 55mmHg (palpebral conjunctival capillaries)
Corneal demand for oxygen increases
Lens temperature increases about 2˚C
pH drops from 7.45 to 7.25
Tear osmolarity decreases from 310-318 mOsm/Kg
to 285 mOsm/Kg
TablE 3
H
ydrogel overnight wear lenses were typically worn for
up to 30 nights then removed, cleaned and reinserted.
By 1985 an estimated 4 million US patients were
wearing lenses in this way. Early overnight wear research was
conducted in an intuitive clinical manner with patient success
being judged by the ability to continue to wear the lenses. As
the 1980s progressed, the scientific interest in the mechanics
and physiology of overnight wear grew. In particular, there
was an increased understanding of the oxygen needs of the
cornea and the effect of oxygen depletion to its structure.
Further increases in the size of the EW market followed,
particularly in the US. Dis­posable EW shows fewer overall
complications, fewer unscheduled appointments and fewer
4
patient symptoms than conventional hydrogel CW lenses.
This was primar­ily due to the increased replace­ment frequency,
resulting in few allergy-based reactions. The incidence of
corneal infection with disposable EW remained the same,
although reports suggested the severity of the infection may
4
be less than that with non-disposable EW.
The growth of the EW market in the US was curtailed in 1989
with the publication and popularisation of a landmark study by
5
Poggio and Schien. This was sponsored by the Contact Lens
Institution (CLI), an industry trade association. The study
showed EW patients to have an incidence of keratitis of 20.9
per 10,000 patient years, compared to 4.1 per 10,000 for soft
daily wear patients. The relative risk of developing microbial
keratitis (MK) was shown to be increased by factors such as
smoking and wearing lenses for more than six consecutive
nights. The relative risks of hydrogel EW versus daily wear
have been verified in several studies since the original CLI
study (Table 4).
Despite the low incidence rates (about 0.2 percent), the Poggio
and Schien study gained significant media coverage and
reduced overall confidence in the modality. The study also
led the FDA to recommend in 1989 that EW be limited to no
more than seven days and six nights of continuous overnight
wear without removal of lenses for cleaning and disinfection
or lens disposal.
3
TablE 4
Overnight Wear
Essential Contact Lens Practice
A range of Si-Hy lenses are now available, some with regulatory
approval for up to 30 nights of continuous wear and others for
six nights of extended wear.
Incidence and relative risk of microbial keratitis:
Extended wear hydrogel to daily wear hydrogel
Annualised incidence per 10,000
R
e l at i v e r i s k
A u t h o rY e a r
D W RGP
D W E W RGPE W o f E W h y d ro g e l
h y d r o g e l
h y drogel
t o D W h y d ro g e l
Poggio et al
MacRae et al
Benjamin
Dart
Nilsson
Cheng et al
1989
4.0
4.1
—
20.9
x5.09
1991
1991
1991
1994
6.8
1.1
—
1.21
5.2
2.1
—
0.51
18.2
4.2
—
—
23.9
8.8
—
3.12
x4.59
x4.2
x5.78
x6.12
1999
1.1
3.5
—
20
x5.72
Current status
Disposable hydrogel EW has been shown to be beneficial
over conventional non-disposable CW, with careful patient
selection and close follow-up.4,6 However, they still result in
significant hypoxia-related adverse events for many wearers
and do not significantly reduce the incidence of MK compared
to conventional non-disposable overnight wear.
Figure 1 Lens binding following
overnight wear with an RGP lens
(Courtesy of Judith Morris and
Andrew Gasson)
High Dk RGP extended wear has several advantages over
the use of soft hydrogel lenses. Notably, enhanced oxygen
transmissibility and an active tear pump mechanism. These
properties allow the issue of hypoxia to be addressed,
with a resultant reduction in the risk of hypoxia-related
complications. Several disadvantages, however, have limited
the more widespread usage of this modality, with the main
issue being comfort, lens binding resulting from changes
in the tear film during sleep (Figure 1) and 3 and 9 o’clock
staining.
Si-Hy lenses were initially developed to address the limitations
of oxygen transmission of hydrogel lenses, and to make
EW a safer and more successful wearing modality. Their
introduction in 1999 resulted in a slow but steady increase
in EW fitting, however new fits in the UK remain less than
7
10 percent.
Their development combines the oxygen benefits of silicone
elastomers with the preferred hydrophilic aspects of hydrogel
lenses. Increasing the silicone content may bring the benefit
of increased oxygen permeability but will also decrease
wettability and increase lipid interaction. Consequently Si-Hy
lenses must be either surface treated or contain components to
achieve a wettable and compatible lens following manufacture.
In general, Si-Hy materials deposit minimal protein although
there is a tendency for greater lipid deposition when compared
to hydrogel materials especially high water content, ionic
hydrogel materials (FDA Group IV).
4
First-generation materials tend to have a higher modulus
than more recently available materials and this can have an
impact on lens fit, initial comfort and mechanically-related
adverse events.
Oxygen supply to the cornea is such that incremental
overnight corneal swelling with lens wear should be eliminated
or significantly reduced. This was the primary design goal of
Si-Hy lenses and studies confirm that overnight swelling is
typically no greater than that measured with no lens wear,
regardless of the different oxygen transmissibilities of the
Si-Hy materials tested8 (Table 2).
Figure 2 Emptying of vessels
following refitting with Si-Hy lenses
(Courtesy of Neil Chatterjee)
This may be explained by the minimal differences in
equivalent oxygen percentage (EOP) or oxygen flux during
closed eye between the Si-Hy materials tested.
These materials represent a significant breakthrough in
design, with the direct result that complications associated
with lens-induced hypoxia — such as epithelial and stromal
oedema, limbal hyperaemia, corneal vascularisation,
endothelial polymegathism and myopic shifts — are now
rarely observed.
Figure 3 Early SEAL lesion resulting
from Si-Hy extended wear (Courtesy
of David Ruston)
Indeed, blood vessels that have extended into the clear
cornea as a result of chronic hypoxia are often seen to empty
following refitting with these lenses (Figure 2). Si-Hy lens
overnight wear is not, however, complication free.
Adverse events
First generation Si-Hy materials are approximately two to
three times stiffer than hydrogel materials and can result in
more negative pressure under the lens during blinks than more
flexible materials such as HEMA or etafilcon A. This may
increase the incidence of mechanical arcuate lesions (Figure
3) with these materials, as well as a more mechanically-related
local papillary conjunctivitis (CLPC) typically observed in
zones two and three (Figure 4). ‘Mucin balls’ (Figure 5) are
more frequently observed with Si-Hy lenses. Frequency of
mucin balls increases the longer the period of overnight wear
and these are more likely to present in eyes with steeper corneal
curvature.9 They are not detrimental to contact lens wear,
with no intervention required if vision is not compromised.
More recent lens and edge designs, as well as materials with
lower modulus (less stiff), have resulted in less mechanicallyrelated adverse events during overnight and daily wear.
Figure 4 Five zones of the upper
palpebral conjunctiva (Courtesy
of CCLRU)
Figure 5 ‘Mucin balls’ between lens
and cornea in Si-Hy extended wear
(Courtesy of Brian Tompkins)
5
Overnight Wear
Essential Contact Lens Practice
Inflammatory responses can manifest as different adverse
events. Contact lens acute red eye (CLARE), contact lens
peripheral ulcer (CLPU) (Figure 6) and other infiltrative
events can occur. Literature reviews have shown that there
are twice as many corneal infiltrative events with Si-Hy lenses
worn overnight up to 30 days when compared with disposable
hydrogel six nights’ extended wear.10 Increased risk cannot
be definitively linked to Si-Hy lenses alone since the effect of
material on outcome is confounded by the differences in length
of wear (30 nights versus six nights). It will be interesting
to observe from future studies whether the availability of
newer Si-Hy materials approved and used for for six nights
of EW followed by disposal will result in a lower incidence of
inflammatory events. Regardless, inflammatory events will
occur more frequently during overnight wear and practitioners
must be confident in their detection and diagnosis. Helpful
grading scales have been designed to support the management
of the full range of infiltrative events (Figure 7).
routine follow-up
Morgan et al
Schien et al
Stapleton et al
SERIOUS
Infiltrative Keratitis (IK)
Infection of the cornea by microbes, characterised by excavation of the corneal
epithelium, Bowman's layer and stroma with infiltration and necrosis of the tissue.1
00 Eyes)
96.4
19.8
—
—
18.2
2008
1.2
1.9
19.5
25.4
2.5, 2.8, 3.0, 3.2, 2.5 (n=5)
Spectacle
Inflammatory reaction of the cornea, characterised in its active stage by focal
excavation of the epithelium, infiltration and necrosis of the anterior stroma.
Bowman’s layer, however, is intact.2
2.3 ± 0.5 (n=43)
Daily Wear
0
Extended Wear
0
0
Spectacle
1
2
Inflammatory reaction of the cornea and the conjunctiva subsequent to a period of
eye closure with soft contact lens wear, characterised by small, focal and diffuse
peripheral corneal infiltration with minimal or no epithelial involvement.
2.1 ± 0.7 (n=67)
Daily Wear
Extended Wear
0
25
6
87
0
Spectacle
Daily Wear
Extended Wear
0
0
14
69
0
Male
Younger age group (12-19 years)
Infrequent lens disinfection
Longer duration
of extended wear
Chlorine disinfection
Lower socio-economic class
Heat disinfection
Inflammatory reaction of the cornea, characterised by anterior stromal infiltration
with or without epithelial involvement.
Immune response of the cornea, characterised by multiple focal corneal infiltrates.
1.2 ± 0.7 (n=67)
2.4 ± 0.9 (n=9)
Spectacle
Daily Wear
Extended Wear
13
15
17
52
0
54
0.4, 1.7, 1.2 (n=3)
Daily Wear
Extended Wear
0
102
16
22
Spectacle
-
Overnight use
of daily wear lenses
Daily Wear
5
0
Extended Wear
0
7
• Mainly central or paracentral, sometimes peripheral
• Peripheral or mid-peripheral
• Peripheral to mid-peripheral
• Peripheral to mid-peripheral
• Scattered across entire cornea
• Peripheral
• Usually large, irregular, focal infiltrate (>1mm) with small satellite lesions
• Significant diffuse infiltration
• Usually small, single, circular, focal infiltrate (up to 2mm)
• Slight diffuse infiltration surrounding focal infiltrate
• Diffuse infiltration (either sectorial or circumferential)
• Focal infiltrates (low to moderate in number)
• Mild to moderate diffuse infiltration and/or
• Small, focal infiltrate, possibly multiple
• Multiple, focal infiltrates of varying size
• Arc-like, greyish-white epithelial lesion with heaped edges, possibly
• Anterior to mid-stroma, may involve entire depth
• Anterior stroma (sub-epithelial)
• Anterior stroma (sub-epithelial)
• Anterior stroma (sub-epithelial)
• Anterior to mid-stroma
• Epithelium and anterior stroma
• Yes
• Only if very severe, rarely clinically observed
• Only if very severe, rarely clinically observed
• Rarely clinically observed
• None
• None
• Full thickness loss (when active), raised edges
• Full thickness loss (when active)
• No significant staining
• Slight to moderate staining
• Staining
• Common, ranging from flare to hypopyon
• Only if severe
• None
• None
• None
• Usual
• None
• Uncommon
• None
• None
• Severe
• Moderate, localised
• Moderate to severe, circumferential
• Moderate
• Unilateral
• Unilateral
• Rarely bilateral
Microbial invasion and infection (bacteria, fungus, parasites)4
the contact lens surface5, bacteria
Toxins released by S.aureus colonising
6
9,10
, overnight contact lens wear10,11,
Trauma8,9, poor contact lens hygiene
12
Overnight contact lens wear, lens material interaction with corneal surface
Progressively worsens without treatment
Immediately discontinue lens wear
Corneal scrapings and antimicrobial therapy
immuno-compromised states
(e.g. fluoroquinolones) mandatory
Monitor daily
Resolves with scar, usually vascularisation
not found on scraping or biopsy
Normally heals rapidly without treatment
Discontinue lens wear until resolution
Close monitoring required
Prophylaxis (antibiotics) if monitoring not possible
Resolves with scar (‘bullseye’ appearance)
NON-SIGNIFICANT
Inflammatory event, characterised by infiltration of the cornea without patient
symptoms.
Infiltrates in the cornea without patient signs or symp
0.7 ± 0.4 (n=40)
0.3 ± 0.2 (n=153)
Spectacle
Daily Wear
Extended Wear
13
25
15
39
0
8
Spectacle
Daily Wear
67
68
85
• No symptoms
• Peripheral
• Commonly peripheral; may be present anywher
• Small, focal infiltrates (up to 0.4mm) and/or
• Mild to moderate diffuse infiltration
• Very small, focal infiltrate, usually only 1 (norm
• Anterior stroma (sub-epithelial)
• Anterior stroma (sub-epithelial)
• None
• None
• Significant staining, immediate diffusion into surrounding tissues
• Often punctate staining
• No staining
• None
• None
• None
• None
• None
• None
• Moderate to severe
• None
• Mild to moderate
• None
• Can be bilateral
• Commonly bilateral
• Can be bilateral
• Can be bilateral
Endotoxins released by Gram-negative bacteria colonising the contact lens
Multifactorial (e.g. foreign body trapped beneath contact lens, mechanical
Smoking
• Unilateral
Viral infection (Adenovirus)
Unknown: Possibly a combination of mechanical properties of the lens
Unknown
Observed at similar rates in contact and non-co
Overnight contact lens wear
Contact lens wear
Exposure to virus (usually Adenovirus), highly contagious
13
From Stapleton et al
Contact lens wear
Contact lens wear (can also be seen in non-contact lens wearers)
Normal occurence
Discontinuing lens wear during active stage leads to
Discontinue lens wear until resolution
Progress to be monitored
No medication required
Scars rarely (depends on etiology)
Discontinue lens wear (slow resolution of weeks or months)
Medication may be required
Discontinue lens wear until resolution (rapid resolution)
Progress to be monitored
No medication required
May require discontinuation if severe, e.g. diffuse infiltrates with redness
No medication required
Lens wear is not disrupted (rapid resolution)
No medication required
surface7
rapid resolution (depending on severity)
Progress should be monitored
Prophylaxis not usually required
trauma, bacterial toxins)
Diabetes
No surfactant or rub and rinse step
Case cleaning (reduction)
Compliance with
hygiene regimen
• Ranges from edge awareness, foreign body sensation to asymptomatic
Asymptomatic Infiltra
• No symptoms
waking
• Irritation
• Redness
• Tearing
• Photophobia
No or infrequent disinfection
• Ranges from severe to moderate pain, foreign body sensation, irritation to
• Irritation to moderate pain
• Redness, tearing and photophobia
• Mild to moderate irritation
• Redness
• Occasional discharge
Spectacle
Smoking
Mechanical injury to the corneal epithelium. Characterised by an arc-like lesion in
the periphery of the superior cornea.
• Moderate to severe pain of rapid onset
• Severe redness (‘meaty’ appearance)
• Decreased visual acuity if the lesion is on the visual axis
• Discharge (mucopurulent or purulent), tearing
• Photophobia
• Puffiness of lids
asymptomatic
• Redness
• Tearing
• No symptoms prior to eye closure
• Patient woken from sleep by symptoms, or symptoms noticed soon after
x3.00
Asymptomatic Infiltrative Keratitis (AIK)
D a i ly w e a r E x t e n d e d w e a r
Serious
Significant
Non-Significant
2=slight, 3=moderate & 4=severe)
6.4
—
Risk factors for microbial keratitis
in
soft
contact lens wearersSuperior Epithelial Arcuate Lesion
Viral
Keratoconjunctivitis
SIGNIFICANT
Contact Lens Induced Acute Red Eye (CLARE)
FIGURE 7
signs:
2.9
2005
Other factors such as tear film stagnation, entrapment of
pathogens and debris underneath the lens, compromised
corneal epithelial integrity and reduced epithelial cell turnover
may play a more significant role in the development of corneal
infection than corneal hypoxia. Risk factors for microbial
keratitis in soft contact lens wearers are shown in Table 6.13
Studies have shown that Pseudomonas aeruginosa, a microorganism often associated with MK, showed a significant
reduction in binding to the epithelium of corneas wearing
lenses with higher oxygen transmissibility and it was hypo­
thesised that Si-Hy lenses would result in a lower incidence
Contact Lens Induced Peripheral Ulcer (CLPU)
2005
of MK. However, recent prospective epidemiological studies
published11,12 and presented at scientific congresses suggest
that Si-Hy when used as CW have a similar incidence of MK
compared to six nights of hydrogel EW. Both have a higher
incidence compared to daily wear re-usable hydrogel lenses
(Table 5). Si-Hy CW can, however, result in less severe infection,
with faster recovery rates.
Infection risk
Microbial Keratitis (MK)
TablE 5
Annualised incidence per 10,000
R
e l at i v e r i s k
A u t h o r Y e a r D W RGP
D W E W E W of CW Si-Hy
h y d r o g e l h y d r o g e l S i - H y t o D W h y d ro g e l
TablE 6
Figure 6 CLPU observed during
Incidence and relative risk of microbial keratitis:
Continuous wear silicone hydrogels to daily wear hydrogels
Topical steroid therapy
Warm climate
diffuse infiltration underlying lesion
Gender
material, ocular topography and lid tonus.
diffuse infiltration
possible evidence of normal corneal cellular act
Figure 7 IER/LVPEI Guide to Corneal Infiltrative Conditions
6
www.siliconehydrogels.com/resources/Guide_to_Corneal_Infiltrative_Conditions.pdf
7
Overnight Wear
Essential Contact Lens Practice
Overnight wear contact lenses are beneficial for many patients
and there is no doubt that patients are interested in the
convenience of this option, especially if endorsed by their eye
care professional. The benefits are particularly evident, with
many occupations such as doctors and nurses on night duty
and those in the armed forces, in addition to certain hobbies,
which make the management of daily wear lenses impractical.
Infant or elderly aphakes are further examples of those who
may also benefit from overnight wear lenses, by overcoming
handling and vision limitations.
However, this lens modality needs to be treated with respect
in view of the greater incidence of overall complications
compared to when contact lenses are worn as daily wear, as
well as the increased risk of MK resulting from overnight use.
It is important, therefore, that a full explanation of the risks and
benefits of overnight wear are provided objectively, allowing
the patient to make an informed choice. This discussion should
include risk comparison with other lens types and wearing
modalities, as well as a comparison to refractive surgery — a
procedure that results in a significantly greater risk of loss of
best corrected vision compared to EW or CW contact lenses.
If the patient accepts this increased risk then the practitioner
has to decide on the best course of action. There are three
possibilities:
•Refuse to fit any overnight wear regardless of physiological suitability. In this case the patient might go to
another practitioner and who might not take the care
required to manage the modality
•Refer the patient to a colleague who is more experienced
in fitting and managing this modality or fit under
supervision until more confidant
•Proceed with the evaluation of suitability and, if the
patient is suitable, fit. This course of action maintains the
relationship between practitioner and patient and allows
the practitioner to offer a total contact lens service.
Instrumentation
The instrumentation required for fitting contact lenses for
overnight wear is essentially the same as for all basic contact
lens fitting. It is vital that the slit-lamp biomicroscope has
good optics and high magnification for viewing subtle corneal
changes, in particular, corneal infiltrative events, which can be
subtle in appearance. As with any form of contact lens practice,
grading scales will allow more objective observation and
recording of baseline tissue appearance prior to lens fitting. It is
important to monitor corneal distortion secondary to hypoxia
in both RGP and soft contact lens wearers. The keratometer
8
provides some, but rather limited, information in this regard.
Keratoscopy can also play a useful role in monitoring corneal
distortion. As for any contact lens, the presence of a normal,
stable, tear film is important. The practitioner must, therefore,
have access to instrumentation that permits tear assessment for
both initial assessment and monitoring.
Since the overnight wear of a contact lens can result in greater
significant adverse events, it is incumbent upon the practitioner
to carefully select candidates for overnight wear. This involves
thorough pre-assessment, but ultimately a lens trial, which
allows optimal fit and frequent monitoring to establish
physiological response.
History and symptoms
The first stage in overnight wear fitting, as in any contact lens
fitting, is to elicit a full history and symptoms from the patient.
In overnight wear fitting it is important to fully understand and
explore the reasons the patient wants overnight lens wear. Is it
because the patient truly needs to sleep in lenses (for example,
occupational need)? Or has interest been generated by consumer
advertising? Has the patient failed in other lens modalities and
thinks this may be a more appropriate modality? Is there a
history of inflammatory events? General laziness or failure to
return for aftercare would be considered as contraindications
to overnight wear. High standards of patient hygiene are
required, and consideration must also be given to the home or
work environment.
Ocular and general health must be questioned; for example
diabetes would be considered by many as a contraindication for
EW but acceptable for daily wear.
Open questioning techniques should be used to identify the
patient needs. It is the obligation of the practitioner to ensure
that the patient fully understands the risks and benefits of
their chosen modality. The patient must also understand the
Reasons for considering and avoiding
overnight wear lens fitting
I n d i c at i o n C o n t r a i n d i c at i o n
Poor handling ability
Non-compliant/Poor hygiene
Lifestyle
Smokers
Occupation
Poor general health
New parents
Blepharitis/MGD
Therapeutic lens fitting
Signs of dryness
History of inflammatory
response
table 7
Patient selection
Adapted from Woods 14
9
Overnight Wear
Essential Contact Lens Practice
importance of self-monitoring and of calling their practitioner
if there are any unusual findings or changes.
cases in terms of suitability, could be successful in daily wear
lenses, but these patients should not be fitted with EW.
Although the absolute risk of developing a serious adverse
reaction to overnight wear is small, the relative risk in
comparison to daily wear is significant with all lens types
including Si-Hy lenses. The patient must understand this,
and the use of a written and signed acknowledgement form is
recommended. As in all contact lens practice, the practitioner
should fully record the outcome of the discussion. Reasons
for considering and avoiding overnight wear modality are
summarised in Table 7.14
Particular aspects to be considered are: a stable tear film,
no corneal staining, full blinking, minimal conjunctival
hyperaemia, and minimal follicles or papillae on the tarsal plate.
A recommended ‘pre-health’ checklist is shown in Table 8.15
table 8
Initial examination
Once the history and symptoms have been completed, the next
stage is to conduct a detailed examination of the anterior segment
to assess the suitability of the patient for contact lens wear.
The practitioner’s next responsibility is then to ensure that
the patient is physiologically suitable for EW, which can be
achieved from lens trial.
Overnight wear of contact lenses puts the cornea in a more
stressful environment when compared to daily wear. It is,
therefore, important to assess all potential contraindications
to the wearer. It is possible that patients who may be borderline
Lens fitting
Pre-fit checklist on ocular health as recommended
by Brennan and Coles15
c h a r a c t e r i s t i c
requirement
Comfor t
Grade 3 (comfor table)
or better
Subjective vision rating
Grade 3 (good) or better
Visual acuity
Within 1 line of best
spectacle acuity
Hypoxic effects
No microcysts or vacuoles*
No striae or signs of visible
oedema
Limbal vascularisation
<0.5mm vessel penetration
Corneal staining
None**
Endothelial polymegethism
≤Grade 1
Changes in corneal cur vature
No irregular corneal
distor tion or warpage**
Infiltrates
None**
Bulbar and palpebral
conjunctiva redness
≤Grade 1
Palpebral conjunctival papillae
≤Grade 1
Conjunctival staining
≤Grade 1
*Existing wearers may show some degree of microcysts, vacuoles or corneal distortion or
warpage and clinical judgement should be used to assess suitability for fitting.
**Overnight wear lenses should not be fitted until staining or infiltrates are resolved
10
Keratometric assessment, should be taken to provide baseline
data in the cornea of the soft EW patient, and fitting
information for the RGP EW patient. The keratometer reflex
should be regular and if keratoscopy is to be carried out, the
cornea should show a regular contour with no distortion or
warpage.
The basic principles of EW lens fitting are the same as for
daily wear. Maximising oxygen supply to the eye in ­addition to
adequate tear exchange to remove post-lens debris should be
prime considerations.
Si-Hy fitting is more critical due to the relative stiffness of
some materials compared to hydrogels. Primary gaze postblink movement should be 0.2–0.3mm and is required for
flushing toxins and debris from underneath lenses. However,
excessive movement can result in discomfort and tarsal plate
changes. Careful observation of edge alignment of the lens to
the bulbar conjunctiva should be made during biomicroscopic
examination, as ‘edge-fluting’ can be a significant reason for
poor comfort and an unsuccessful fit. A lens which is centrally
steep may lead to fluctuating vision, which can be solved with
a flatter base curve. High molecular weight sodium fluorescein
can be useful when assessing the fit of stiffer materials.
More recent lower modulus Si-Hy materials exhibit fitting
characteristics more similar to hydrogel materials.
RGP lenses should be fitted to achieve an optimum fit to avoid 3
and 9 o’clock staining and lens binding. Fitting as close as possible
to alignment to achieve equal lens bearing across the cornea reduces
the risk of lens binding. In particular, if the lens is too tight in
the mid periphery this will increase the risk of lens binding. Lack
of tear exchange will cause an increase in tear viscosity. Other
design considerations differentiating RGP EW from daily wear
include increasing lens diameter to help stabilise the fit and
increasing peripheral clearance to help avoid lens binding.
It is critical with overnight wear fitting that lenses be thoroughly
cleaned and disinfected on removal, if they are to be reinserted.
11
Overnight Wear
Essential Contact Lens Practice
With disposable systems, whether weekly or monthly, this need
can be overcome. However, the latter necessitates the need for
a longer period of continuous wear (up to one month) if lens
care solutions are to be avoided.
Lens adaptation
In the authors’ opinion, it is important that neophyte patients
adapt fully to their lenses on a daily wear basis before starting
to sleep in them.
Typically, at least one week of daily wear should be completed
for soft lenses with the wearing time being gradually increased
each day in the normal manner. Of course, the build-up will be
more gradual for the novice RGP wearer. This period of daily
wear use also helps in practicing lens handling technique.
It is particularly important the patient understands the need to
clean and disinfect the lenses during this adaptation period and
that they are given full instruction in lens maintenance, even
though they will not require to do this once they are wearing
the lenses on single-use EW or CW basis (namely, disposal on
removal).
Once the patient has built up to all-day wear they should,
ideally, attend an aftercare appointment before commencing
overnight wear. At this appointment, the practitioner should
evaluate the extent to which the patient has adapted to lens
wear and assess their end of day comfort.
Practitioners should be cautious about overnight wear if there
are any visible signs of lack of adaptation during daily wear.
In particular, signs of oedema, conjunctival hyperaemia,
palpebral changes, corneal infiltrates or corneal staining,
whether resulting from desiccation or mechanical insult as well
as lens binding.
If the eye is clear and the patient appears to have fully adapted
to daily lens wear then they may proceed with the first night of
overnight wear. The practitioner should instruct their patient
to remove the lens if there is any pain or significant redness
of the eye, either during the night or upon waking. They
should be told to check for lens movement on eye opening
and ocular lubricants can be recommended for morning use
to encourage movement and debris flushing from beneath the
lens. It is also important to schedule a follow-up appointment
for the morning after the first overnight wear. ‘Stress’ testing
to determine what level of corneal oedema is acceptable is now
less critical with the introduction of Si-Hy lenses.
When refitting hydrogel lens wearers, they may initially find
silicone hydrogel lenses less comfortable due to the different
surface properties of silicone hydrogel lenses as well as the
12
higher lens modulus of some products. This adaptation period
can take three to four weeks.
It must be stressed that the ability of any patient to wear lenses
overnight, whether for one week to one month, does not assure
continued success indefinitely. Regular and ongoing aftercare
visits are essential for patients wearing overnight wear lenses.
First aftercare appointment
The appointment after the first overnight wear should be
made as early as possible in the morning. This is more critical
with hydrogel lens fitting to ensure that signs of corneal
oedema are not missed. More importantly, this is when the
cornea will have its most stressed appearance and is therefore
the optimal time for slit-lamp examination. The examination
routine should follow the normal aftercare pattern. Particular
attention should be paid in the history and symptoms section
to the comfort and vision of the lens upon eye opening and
then the speed of resolution of any symptoms, which ought to
be quite rapid.
The assessment of lens fit should show free-moving lenses with
no sign of lens binding. Visual acuity in the lenses should not
show any difference from that obtained before the first night
of overnight wear. When refitting hydrogel EW lens wearers
with Si-Hy lenses, greater lipid deposition may be observed
in some patients. This may necessitate advice on the need to
remove and clean the lens with a surfactant cleaner followed
by disinfection before insertion again or increase frequency of
lens replacement (namely, from monthly replacement to weekly
replacement). A whiter eye is likely to be observed due to the
significantly improved oxygen supply to the cornea resulting
in less limbal redness. Over-refraction may also show a small
refractive shift (less minus) due to the re-oxygenation of the
cornea and more microcysts may be observed initially before
reducing in number and eventual elimination.
All overnight wear patients should be instructed to respond
to any signs or symptoms quickly and appropriately. Patients
should be advised to remove the lenses immediately if they
experience any pain, red eye or blurred vision, and call their
practitioner for advice. This availability of immediate advice
should be supported further by supplying patients with an
after-hours emergency contact. Remember, early symptoms
of potentially serious problems can be subtle; foreign body
sensation is frequently the earliest symptom of MK.
Educating the patient as to appropriate self-management can
enhance the success and safety of contact lens wear.
It is important that all practice staff who may receive calls
from contact lens patients understand the appropriate action.
13
Overnight Wear
Essential Contact Lens Practice
TablE 9
Management guidelines of overnight wear complications
O b s e r vat i o n
Possible cause
Ac t i o n r e q u i r e d
1-3 striae
• within four hours of awakening
•present >4 hours after
awakening
Mild stromal oedema
due to closed eye
Excessive oedema
Monitor for persistence later in day
Increase oxygen supply
Change to daily wear
≥4 striae and/or folds
Excessive oedema
Increase oxygen supply
Change to daily wear
10-30 microcysts
Mild corneal hypoxia and/or
hypercapnia
Increase oxygen supply*
Monitor more frequently
>30 microcysts
Excessive corneal hypoxia and/or
hypercapnia
Increase oxygen supply*
Change to daily wear
Vascularisation (note: most
commonly seen in superior
cornea initially)
Long-term hypoxia with hydrogel
contact lens wear
Increase oxygen supply
Change to daily wear
Refit with RGP or silicone hydrogel
General CLPC
Local CLPC
Denatured protein build-up
Replace lenses and consider frequent
replacement thereafter
on lenses
Lens stiffness, lens or edge design Fit lower modulus Si-Hy lens
Change lens designy
Corneal staining
• Desiccation
• 3 and 9 o’clock
• arcuate lesions (eg SEAL)
CLARE
(contact lens acute red eye)
Pervaporisation of tears
Compromised RGP fit
Incomplete blinking
Poor surface wetting
Hypoxia under upper lid
Mechanical
Poor lens fit
Increase replacement frequency
Try alternative material
Use ocular lubricants
Modify fit
Blinking exercises
New RGP lenses
Increase oxygen supply
Use material with lower modulus
Improve fit
Change lens design
Poor tear exchange
Tight lens fit
Bound lens
Exotoxins from bacteria
Loosen fit. Try alternative lens design
Loosen fit
Improve fit, try ocular lubricants,
change lens design
Improve lens hygiene, increase lens
replacement frequency
Hypoxia
Poor tear exchange
Tight lens fit
Solution reaction
Remove lens and allow to resolve
Increase oxygen supply
Loosen fit. Try alternative lens design
Loosen fit
Change solution regimen
CLPU
(contact lens peripheral ulcer)
Exotoxins from bacteria
Remove lens and monitor over 24hrs
If symptoms and signs increase:
immediate referral
Infectious ulcer
Microbial invasion of cornea
Remove lens and immediate referral
Corneal infiltrate (non-staining)
On lens removal, if the patient’s signs or symptoms persist,
an urgent appointment with the practitioner should be made.
It has to be remembered that serious adverse responses can
develop within 24 hours.
Patients should be instructed to bring their lenses, their case
and any solutions used to the appointment. As with daily
wear contact lens users, all overnight lens wearers should be
advised to have an up-to-date pair of spectacles for use as
necessary.
On awakening each morning the lens wearer should carry out
a self-assessment:
• Do my eyes look good?
• Do my eyes feel good?
• Do my eyes see good?
If any of these questions are answered in the negative, then
lenses should immediately be removed and the decision tree
followed as outlined in the Aftercare article of this series.
Ongoing aftercare
Following a successful fitting and first overnight wear the
patient should be monitored after one week, and thereafter every
three months or more frequently as required. All appointments
should be made as early as possible in the morning.
As with all contact lens wearers, a full eye examination
including ophthalmoscopy should be undertaken at least
every two years or sooner if symptoms suggest a non-contact
lens-related problem.
Interpretation of findings
Results from patient discussion, measurement and observation
all need to be taken into account in deciding the course of
action to be taken.
Table 9 summarises the complications seen in overnight wear
patients and recommends management options.
Many conditions are rarely observed during daily wear followup and all forms of continuing education on overnight wear
are to be encouraged to ensure appropriate recognition and
management when prescribing this modality.
* Note: when refitting with higher Dk/t lens, the number of microcysts may initially increase prior to being reduced or eliminated
14
15
Overnight Wear
Essential Contact Lens Practice
references
O v e r n i g h t w e a r V s d a i ly w e a r
Ad va n ta g e s D i s a d va n ta g e s
Convenience
Increased risk of corneal
infection
Continuous vision correction
Potentially for mechanical
induced adverse events
Less maintenance
Increased risk of inflammatory
events
Reduced or no care products
Increased chair-time costs
Less handling
Adapted from Woods 14
Summary
It is important to view the issues of overnight wear in
perspective. Although there may be an increased risk of MK
compared to daily wear, there is significantly less risk of loss
of best corrected visual acuity when compared to Lasik.16
Extended or continuous wear is not a suitable modality for
everybody, but recent material developments have increased
success rates as well as improved wearing comfort. It can
be the best choice for some patients – especially those with
specific vocational or recreational demands and medical
indications. If the need for overnight wear is established, it
is better for the practitioner to manage responsibly rather
than merely to say ‘no’. Informed choice and continuous
careful monitoring are of the utmost importance. Table 10
summarises the advantages and disadvantages of overnight
wear,14 which should be included in patient discussion.
New lens materials, in the form of Si-Hy, have resulted in
significant improvements in satisfying the physiological
requirements of the cornea during eye closure in that
hypoxic-related complications should no longer be a feature
of overnight wear for the majority of patients.
Many patients also report improved comfort and less dryness
after a period of adaptation. They should therefore be the
lens of choice when offering this modality to new wearers.
However, these lenses are not without complications which
require appropriate recognition and management. This may
involve the use of RGP lenses, moving to daily wear silicone
hydrogel or hydrogel lenses or, in the future, the use of
therapeutic agents by contact lens practitioners.
Regardless of lens type prescribed, the importance of
patient selection and education, optimal lens fitting and
comprehensive/regular follow-up remains the same.
16
TablE 10
Advantages and disadvantages of overnight wear
References
1. Young G. Overview on rigid lens
extended wear before 1984. J Brit
Contact Lens Assoc, 1985; 8:2 71-77.
2. Holden BA, Mertz GW. Critical
oxygen levels to avoid corneal oedema
for daily and extended wear. Invest
Ophthal Vis Sci, 1984; 25 1161-1167.
3. Harvitt DM, Bonanno JA. Reevaluation of the oxygen diffusion
model for predicting minimum contact
lens Dk/t values needed to avoid
corneal anoxia. Optom Vis Sci, 1999;
76 712-9.
4. Poggio EG, Abelson M. Complications
and symptoms in disposable
extended wear lenses compared with
conventional soft daily wear and soft
extended wear lenses. The CLAO
Journal, 1993; 10: 31-39.
5. Poggio EG and Schien OD et al. The
incidence of ulcerative keratitis among
wearers of daily wear and extended
wear soft contact lenses. N Eng J Med,
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6. Hamano H et al. A study of the
complications induced by conventional
and disposable contact lenses. The
CLAO Journal, 1994; 20:2 103-7.
7. Morgan PB. Trends in UK contact lens
prescribing. Optician, 2007; 233:6104.
8. Steffen R and Schnider C. The
impact of silicone hydrogel materials
on overnight corneal swelling Eye &
Contact Lens, 2007; 33:3: 115-120.
authors
12. Schein OD et al. The incidence of
microbial keratitis among wearers of a
30-day silicone hydrogel extended wear
contact lens. Ophthalmology, 2005; 112
2172-2179.
13. Stapleton F et al. The Incidence
of Contact Lens-Related Microbial
Keratitis in Australia. Ophthalmology,
2008; 115”10 1655-1662.
14. Woods J. Overnight wear with
silicone hydrogel contact lenses.
Optician, 2007; 233 6100.
15. Brennan N and Coles C. Where do
silicone hydrogels fit into everyday
practice? (chapter 8) Silicone
Hydrogels, the rebirth of continuous
wear contact lenses. ButterworthHeinemann, Oxford 2000.
16. Watson SL et al. Improved safety in
contemporary Lasik. Ophthalmology,
2005; 112 1375-1380.
Jane Veys MSc MCOptom
FBCLA FAAO, Education Director,
The Vision Care Institute™
Johnson & Johnson Vision Care,
Europe, Middle East & Africa.
Formerly in contact lens research,
optometric education and
independent practice.
John Meyler BSc FCOptom
DipCLP Senior Director
Professional Affairs, Johnson
& Johnson Vision Care, Europe,
Middle East & Africa. Formerly in
independent optometric practice.
Ian Davies BSc MCOptom DipCLP
FAAO, Vice President, The
Vision Care Institute™ Johnson
& Johnson Vision Care, Europe,
Middle East & Africa. Formerly
in contact lens research and
independent optometric practice.
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3. Sweeney DF. Silicone Hydrogels,
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9. Dumbleton K et al. Clinical
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The Vision Care Institute™ is a trademark of Johnson & Johnson Medical Ltd. © Johnson & Johnson Medical Ltd. 2008
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