Investigating the Efficacy of Hydrogen Peroxide

Investigating the Efficacy of Hydrogen Peroxide Disinfection of Scleral Lens Cases of Different Sizes
Tammi Graham, OD; Judith Perrigin, OD, FAAO
University of Houston College of Optometry, Houston, TX
INTRODUCTION:
MATERIALS & METHODS:
RESULTS:
Advancements in scleral lens materials and designs in the last
decade have increased its use in the management of anterior
segment ocular disease.1 Similar to other types of contact lens use,
scleral lens wearers are also at risk for contact lens related
complications. Some experienced scleral lens fitters have
proposed the use of H2O2 systems for overnight disinfection of
scleral lenses.2,3 Their clinical recommendation of scleral lens
disinfection involves the use of proprietary H2O2 solution with a
non FDA approved large case for larger diameter scleral lenses
(16mm and larger).2,3 In order to neutralize the H2O2 solution
when using the larger case, patients are instructed to detach the
neutralizing disk from the smaller case and place it onto the large
non-approved case.2 This method of disinfection is considered
off-label and literature on the efficacy of disinfection with this
method is sparse.
Day 1: Reactivate Culture
 A total of twelve Case A, twelve Case B, and the corresponding twenty four

Activate freeze-dried MicroKwik culture of S. marcesens and S. epidermidis
according to manufacturer instructions.

Cap and incubate at 37°C for 24 hours.
baskets were inoculated with S. marcescens and S. epidermidis and allowed to
form a biofilm over a 16-hour period.
 One control case and basket of each type was not inoculated. No growth was
found on any of the plates from Case A. One of the plates from Case B grew 2
colonies; one colony of S. epidermidis and one of S. marcescens (Figure 4).
Day 2: Form Biofilm
 ANOVA unpaired t-test was performed comparing total colony growth

Create 0.1:1 mL dilution of each culture with fluid thioglycollate broth.

Inoculate 2 agar plates with undiluted culture (Figure 2a & b) and 2 plates of
diluted culture (Figures 3a, 3b, 3c).

Create inoculate by combining 1mL of each bacteria into a test tube.

Apply bacteria mix to calcium alginate swab.

Swab inside of cases up to fill line and outer baskets of 12 cases of each size.
Store contaminated cases upright and invert baskets to allow biofilm
formation for 16 hours.
between the two types of cases. With a total n value of 12, the two-tailed
P-value was 0.3282 (P≤ 0.05).
Figure 2a. One loop of undiluted S. epidermidis
Day 3: Disinfection and Bacteria Collection
PURPOSE:
 This pilot study aims to investigate the efficacy of a propriety
brand H2O2 solution (Clear Care®) to disinfect contact lens cases
of different size inoculated with Staphylococcus epidermidis (S.
epidermidis) and Serratia marcescens (S. marcescens).
 The cases differ in size and manufacturer, with the smaller size
(case A) marketed with Clear Care®, and the larger size (Case B)
sold by an independent company without a neutralizing disk
and H2O2 solution (figure 1).
 We hypothesize that the difference in efficacy of disinfection of
the contaminated cases and baskets, defined by total growth of
bacterial colonies, between the two sizes will be statistically
insignificant.

Follow manufacturer recommendations for disinfection and neutralization
by instilling H2O2 disinfection solution to the fill line and recapping.

Allow H2O2 solution to neutralize for 8 hours.

Inoculate 5% sheep blood agar plate with 1 loop of the neutralized H2O2
solution.

Empty neutralized solution into biohazard container.

Use a sterile calcium alginate swab to swab inside of case up to fill line and
outside of basket and inoculate 5% sheep blood agar plate.

Incubate plates at 37°C for 48 hours.
Figure 4. Growth of 2 colonies (one colony of S.
epidermidis and one of S. marcescens) from Case B.
Day 4: Data Collection

Observe plates for growth and count colony forming units.

Perform gram stain on any growth found.
DISCUSSION:
Figure 2b. One loop of undiluted S. marcescens
Figure 1. Cases of two different sizes (Case B on the left, Case A
on the right).
Figure 3a. Looping solution after 8-hour
neutralization of H2O2 solution
Figure 3b. One loop of diluted S. epidermidis
Figure 3c. One loop of undiluted S. marcescens

Some scleral lens fitters currently advise patients to use the large case (Case B) with the
neutralizing disk detached from the small case (Case A) and Clear Care® solution for
disinfection. This is an off label use of the Clear Care® system, and has not been studied
in depth in literature.

The present study did not demonstrate a statistically significant difference in H2O2
disinfection between the two case sizes.

This suggests that the current off label recommendation for disinfection with a large
contact lens case using the neutralizing disk removed from the small case with Clear
Care® is safe for scleral contact lens wearers regarding S. epidermidis and S. marcescens
contamination.

The decision to continue offering this off label recommendation should be guarded due
to the small sample size used in this study and due to lack of information regarding
other microorganisms.

Replication of this study using a much larger sample size may provide more concrete
evidence for the safety of scleral lens use through proper lens disinfection.

This study used S. epidermidis and S. marcescens, which were effectively eradicated using
the Clear Care® disinfection system with both the large and small cases. Future studies
can further establish clinical relevance by using other microorganisms known to cause
ocular infections with contact lens use, such as Pseudomonas and Acanthamoeba.

In summary, the present pilot study did not demonstrate a statistically significant
difference between the efficacy of disinfection of contaminated scleral contact lens
cases of differing sizes with a proprietary H2O2 contact len disinfection solution. Due to
the small sample size, the interpretation of the results is limited, and requires future
investigations.
References available upon request