Comparison of surface roughness and bacterial adhesion between cosmetic contact lenses and conventional contact lenses.

ARTICLE

Comparison of Surface Roughness and Bacterial Adhesion Between Cosmetic Contact Lenses and Conventional Contact Lenses Yong Woo Ji,

M.D.,

Young Joo Cho, M.D., Chul Hee Lee, M.D., Soon Ho Hong, Dong Yong Chung, Eung Kweon Kim, M.D., and Hyung Keun Lee, M.D.

Objective: To compare physical characteristics of cosmetic contact lenses (Cos-CLs) and conventional contact lenses (Con-CLs) that might affect susceptibility to bacterial adhesion on the contact lens (CL) surface. Methods: Surface characteristics of Cos-CLs and Con-CLs made from the same material by the same manufacturer were measured by atomic force microscopy (AFM) and scanning electron microscopy. To determine the extent and rate of bacterial adhesion, Cos-CL and Con-CL were immersed in serum-free Roswell Park Memorial Institute media containing Staphylococcus aureus or Pseudomonas aeruginosa. Additionally, the rate of removal of adherent bacteria was evaluated using hand rubbing or immersion in multipurpose disinfecting solutions (MPDS). Results: The mean surface roughness (root mean square and peak-to-valley value) measured by AFM was significantly higher for Cos-CL than for ConCL. At each time point, significantly more S. aureus and P. aeruginosa adhered to Cos-CL than to Con-CL, which correlated with the surface roughness of CL. In Cos-CL, bacteria were mainly found on the tinted surface rather than on the noncolored or convex areas. Pseudomonas aeruginosa attached earlier than S. aureus to all types of CL. However, P. aeruginosa was more easily removed from the surface of CL than S. aureus by hand rubbing or MPDS soaking. Conclusions: Increased surface roughness is an important physical factor for bacterial adhesion in Cos-CL, which may explain why rates of bacterial keratitis rates are higher in Cos-CL users in CL physical characteristics. Key Words: Cosmetic contact lens—Atomic force microscope—Surface roughness—Bacterial adhesion—Biofilm—Pseudomonas aeruginosa— Staphylococcus aureus—Microbial keratitis.

From the Institute of Vision Research, Department of Ophthalmology (Y.W.J., Y.J.C., C.H.L., E.K.K., H.K.L.), Yonsei University College of Medicine, Seoul, Korea; Division of Microbiology (S.H.H.), Department of Laboratory Medicine, Gangnam Severance Hospital, Yonsei University, Seoul, Korea; Morphology Laboratories (D.Y.C.), Yonsei Biomedical Research Institute, Seoul, Korea; and Institute of Corneal Dystrophy Research (E.K.K., H.K.L.), Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea. Supported by Advanced Science Research Program (Grant No. NRF2012R1A2A2A02009081) through the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science, and Technology and partially by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute, funded by the Ministry of Health and Welfare, Republic of Korea (HI13C0055). The authors have no conflicts of interest to disclose. Address correspondence and reprint requests to Hyung Keun Lee, M.D., Department of Ophthalmology, Gangnam Severance Hospital, 211 Eonju-ro, Gangnam-gu, Seoul 135-720, Korea; e-mail: [email protected] Accepted May 21, 2014. DOI: 10.1097/ICL.0000000000000054

Eye & Contact Lens Volume 41, Number 1, January 2015

(Eye & Contact Lens 2015;41: 25–33)

T

he use of cosmetic contact lenses (Cos-CLs) is becoming increasingly popular among patients because they not only improve visual acuity but also change or restore the appearance of the eye. Cosmetic contact lenses are especially common in East Asia (i.e., Japan, South Korea, and China), accounting for 13% of contact lens (CL) use in 2012, because they can be used to drastically alter the appearance of the eye. This is especially evident in the entertainment industry.1,2 Currently, many teenagers are exposed to Cos-CLs and start to use them without proper education. However, complications that can arise when wearing CL, such as microbial keratitis (MK), occur more frequently and are more serious in patients using Cos-CLs than in those using conventional contact lenses (Con-CLs).3 Contact lens–induced MK is a rare complication but represents the most significant health concern because it causes deterioration of vision or blindness.4–6 Microbial adhesion to CLs is an important first step in the initiation of many adverse events that occur during CL wear because CLs are a vector for microbial entry into the eye and biofilm formation.6–10 Although many studies have reported the importance of the hydrophobicity and surface roughness for microbial adhesion, these studies were mostly limited to analyses of noncolored Con-CLs.11–17 Although the materials and their hydrophobicity of Cos-CLs are almost identical to those of Con-CLs, a recent study has shown that the relative risk of developing CLrelated MK is 16.5 times higher in Cos-CL wearers compared with Con-CL wearers.3 Previous studies have suggested noncompliance as one of the most key factors in the cause of MK in Cos-CL.3,18 However, only few studies have analyzed the surface characteristics of Cos-CLs related to microbial adhesion. The purpose of this study was to determine physical properties and microbial susceptibility of Cos-CLs and Con-CLs and to correlate relationships between surface roughness and bacterial adhesions. In addition, biofilm formation on various CLs and removal of bacteria by different cleansing methods were investigated.

METHODS Contact Lenses Six types of commercially available sterile unworn hydrogel CLs were used in this study. Three were opaque cosmetic colored 25

Copyright @ Contact Lens Association of Opthalmologists, Inc. Unauthorized reproduction of this article is prohibited.


Y. W. Ji et al.

Park Memorial Institute 1640 medium using a homogenizer (Tissue-Teator 985370-395 homogenizer; BioSpec Products, Bartlesville, OK).

Quantification of Bacterial Adhesion to Contact Lenses

FIG. 1.

Configurations of the contact lenses used in the study.

lenses with the purpose of altering appearance (1-DAY ACUVUE DEFINE and ACUVUE 2 DEFINE; Johnson & Johnson Vision Care, Inc., Jacksonville, FL; and eyeLIKe Callamatch II; KORYO EyeTech Co., Ltd., Seoul, South Korea). The other three types were conventional clear lenses (1-DAY ACUVUE MOIST and ACUVUE 2; Johnson & Johnson Vision Care, Inc.; and eyeLIKe EYEPOP; KORYO EyeTech Co., Ltd.). These lenses were made of two types of material according to the manufacturer: Etafilcon A (Johnson & Johnson Vision Care, Inc.), which belongs to Food and Drug Administration group IV (high water, ionic), and 2-HEMA (KORYO EyeTech Co., Ltd.), which belongs to Food and Drug Administration group I (low water, nonionic). The lenses also had different applications (daily, extended, or continuous wear). The configurations and properties of these CLs are summarized in Figure 1 and Table 1.

For quantification of bacterial cells adhering to the surface of CLs, the number of CFUs was determined; 500 mL of each McFarland No. 1 bacterial suspension was collected, and 3 mL of 2.5 · 107 CFU/mL bacterial solution was placed in each well of a 12-well plate. The CLs were immersed in each bacterial solution for 1, 12, and 24 hr. For the 24-hr immersion, the bacterial solution was diluted to 1:4. The CLs were removed and washed gently three times for 5 min in 20 mL of 0.9% saline to remove nonadhered bacterial cells. After washing, CLs were aseptically transferred to individual sterile tubes containing 5 mL of RMPI and were vortexed for 3 min at 3,000 rpm to detach adhered bacterial cells from the surface of the CLs (Vortex-Genie 2; Scientific Industries, Inc., Bohemia, NY). Using a 1:1,000 calibrated platinum loop for clean-catch midstream specimens, accurate aliquots of each tube were inoculated onto a blood agar plate (BAP). To form a single isolated colony, we used the right angle streaking method that is normally used for urine sample culturing. A single streak was made quickly at the center of the BAP and additional streaks were made with a sweeping motion at right angles to the primary inoculum, without restreaking the same area. Finally, the bacterial cells were diluted and isolated by spreading the inoculum. The BAPs were inverted and incubated at 37°C in 5% CO2 for 18 hr. After incubation, the number of CFUs was calculated.

Bacterial Strains and Culture Preparation

Removal of Biofilm and Attached Bacteria From Contact Lenses

Staphylococcus aureus (strain ATCC No. 29213) and Pseudomonas aeruginosa (strain ATCC No. 29853) were used in this study. These were provided by the Division of Microbiology, Department of Laboratory Medicine, Gangnam Severance Hospital, Yonsei University, Seoul, Korea. Staphylococcus aureus and P. aeruginosa were obtained from stock cultures in SoybeanCasein Digest Medium that were stored at 280°C. Using a turbidity transmitter (DensiCHEK Plus; bioMérieux, Inc., Durham, NC), a McFarland No. 1 bacterial suspension, which is equivalent to 3.0 · 108 colony-forming unit (CFU)/mL, was prepared in Roswell

For removal of the biofilm and attached bacteria from the CLs, we compared the methods of hand rubbing and immersion in commercially available multipurpose disinfecting solutions (MPDS) (OPTIFREE EXPRESS; Alcon, Inc., Schaffhausen, Switzerland). Two sets of six types of CLs were immersed in solutions containing S. aureus or P. aeruginosa for 24 hr as described above. After washing the CL with saline, one set was soaked in MPDS for 1 or 6 hr without hand rubbing, whereas the other set was washed by hand rubbing for 3 min before soaking in MPDS for 1 or 6 hr. Bacterial culture and incubation were performed as above, and the number of CFUs was calculated.

TABLE 1. CL Type Conventional Daily wear Extended wear Continuous wear Cosmetic Daily wear Extended wear Continuous wear

Recommended Replacement 1d 2 wk 6 mo 1d 2 wk 6 mo

Material Etafilcon A Etafilcon A 2-HEMA Etafilcon A Etafilcon A 2-HEMA

Physical Properties of the Contact Lenses Used in This Study Water Content (%)

Dk/t Value (at3.00 D)

BC (mm)/Dia (mm)

Center Thickness (at-3.00 D) (mm)

Color-Tinting Method

58

25.5 · 1029

8.5/14.2

0.084

N/A

8.3/14.0

0.084

N/A

8.6/14.0

0.100

N/A

8.5/14.2

0.084

Sandwich

8.3/14.0

0.084

8.6/14.0

0.100

25.5 · 10

29

38

12.0 · 10

29

58

25.5 · 1029

58

58 38

25.5 · 10

29

12.0 · 10

29

CL, contact lens; DK/t, oxygen transmissibility; BC, base curve radius; Dia, diameter; N/A, not applicable.

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Eye & Contact Lens Volume 41, Number 1, January 2015 TABLE 2.

Surface Roughness of Cosmetic Lens on Bacterial Adhesion

Bacterial Colony Formation After Immersion of Contact Lenses in Bacterial Solution for 1, 12, and 24 hr Immersion Time: 1 hr

Immersion Time: 12 hr

Immersion Time: 24 hr

Conventional

Cosmetic

Conventional

Cosmetic

Conventional

Cosmetic

0 0.50 14.50

2.00 3.00 64.00

4.00 20.00 74.50

25.00 55.50 155.50

18.00 50.00 238.00

54.00 70.00 380.00

4.50 4.55 27.00

7.20 8.75 31.20

12.05 13.30 34.45

15.35 19.75 40.15

89.20 99.80 176.40

102.00 133.00 197.60

Staphylococcus aureusa Daily wear Extended wear Continuous wear Pseudomonas aeruginosab Daily wear Extended wear Continuous wear

All values are CFU/mL · 104.

a


b

CFU, colony-forming unit.

Measurement of Surface Roughness by Atomic Force Microscopy For atomic force microscopy (AFM), all types of CLs were hydrated with saline and cut into quarters. Each CL portion was attached to a microscope slide using double-sided sticky tape. The AFM equipment used in this study was a XE-Bio (Park Systems, Santa Clara, CA) equipped with a Super-Luminescent Diode and 2D

XY Flexure/High-Force Z scanners, operated in the noncontact mode with an aluminum coating on the detector side of the Si3N4 cantilever tip and a 42 N/m force constant. Height images were recorded in three dimensions on each CL quarter, and the average roughness (Ra), root-mean-square roughness (Rq), and ten-point mean height roughness (Rz) were obtained from these images. Atomic force microscopy analyses were conducted as quickly as possible

FIG. 2. Representative photographs of bacterial colonies on surface of each contact lens after immersion of contact lenses in bacterial solution for 1, 12, and 24 hr. (A) Staphylococcus aureus (B) Pseudomonas aeruginosa (for the 24-hr immersion condition, the bacterial solution was diluted to 1:4).

© 2014 Contact Lens Association of Ophthalmologists

27



Y. W. Ji et al.

Scanning Electron Microscopic Examination

FIG. 3. Comparison of Staphylococcus aureus (A) and Pseudomonas aeruginosa (B) adhesion onto Cos-CL and Con-CL, composed of same material, Etafilcon A, after immersion in bacterial solutions (*P,0.05 by independent t test). Cos-CL, cosmetic contact lens; Con-CL, conventional contact lens.

to minimize dehydration of the CLs, which was assumed to be minor because no significant differences were observed between the first and last measurements for each sample. The examinations were performed on both concave and convex sides of every CL. For the Cos-CLs, the surface of the color-tinted area was measured. The equations for measuring CL roughness are as follows: 1. Average roughness (Ra):

Arithmetic average height ðzÞ : zðN ; M Þ ¼ RaðN ; M Þ ¼

1 Xn zðx; yÞ; x¼1 N

1 Xn z x; y 2 z x; y : x¼1 N

After bacterial attachment of CLs immersed for 24 hr, each CL was fixed with 2% glutaraldehyde/paraformaldehyde in 0.1 M phosphate buffered saline (PBS), pH 7.4, for 2 hr and washed three times for 30 min in 0.1 M PBS. Contact lenses were postfixed for 2 hr with 1% OsO4 dissolved in 0.1 M PBS, dehydrated in a gradually ascending series of ethanol solutions (50%–100%), infiltrated with isoamyl acetate, and dried in a critical point dryer (HCP-2; Hitachi, Tokyo, Japan). Samples were coated with gold by using the ion sputter (IB-3; Eiko, Tokyo, Japan) at 6 mA for 6 min. The samples were then examined with a scanning electron microscope (FE-SEM S-800; Hitachi) at an acceleration voltage of 10 to 20 kV. Photographs were taken at different magnifications ranging from ·100 to ·10,000. Images were digitalized and stored as tagged image file format files in the microscope computer. Scanning electron microscopy examinations were performed for both concave and convex sides of the CLs.

Statistical Analyses To analyze differences in variables between Con-CLs and CosCLs, the independent t test was performed with Statistical Package for the Social Sciences software (SPSS 21.0; SPSS, Chicago, IL) assuming statistical significance at P,0.05. To analyze the correlation between surface roughness and bacterial adhesion of CLs, Pearson correlation analysis was performed with SPSS, assuming statistical significance at P,0.05 and Pearson correlation coefficient (r) of 21#r#1.

RESULTS 2. Root-mean-square roughness (Rq):

Comparison of Bacterial Adhesion Between Contact Lenses

rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 Xn ðzðx; yÞ 2 zðx; yÞÞ2 : RqðN ; M Þ ¼ x¼1 N

3. Ten-point mean height roughness (Rz):

Rz ðN ; M Þ ¼

1 X5 1 X5 Rpi þ Rvi: i¼1 i¼1 N N

TABLE 3.

Surface Roughness Measured by Atomic Force Microscopy

Average Roughness (Ra)

Concave surface roughness of CL Daily wear Extend wear Continuous wear Convex surface roughness of CLa Daily wear Extend wear Continuous wear

Based on bacterial colony formation, adherence of S. aureus to Cos-CL was much greater than adherence to Con-CL for each time of immersion in bacterial solution (1, 12, and 24 hr). After 1 hr of immersion, S. aureus colonies were not obtained for daily wear Con-CLs, whereas several colonies were cultured from the same type of Cos-CL. After 24 hr of immersion, daily wear ConCLs showed the lowest culture rate compared with the five other types of CLs. For extended wear CLs, Con-CLs also showed lower S. aureus culture rates than Cos-CLs at 1, 12, and 24 hr of immersion. For both Con-CL and Cos-CL, continuous wear

Root-Mean-Square Roughness (Rq)

Ten-Point Mean Height Roughness (Rz)

Conventional

Cosmetic

Conventional

Cosmetic

Conventional

Cosmetic

9.68 10.89 19.67

34.03 51.69 27.97

12.39 14.27 41.62

52.99 54.86 73.14

182.12 203.50 986.32

809.08 819.35 1765.85

9.98 19.88 21.90

32.71 44.92 54.95

12.82 25.97 26.44

56.52 70.18 78.60

188.42 274.36 463.17

411.93 484.57 886.70

a

All values are nanometer at 2500 mm2.

a

CL, contact lens.

28





FIG. 4. Representative photographs from atomic force microscope analysis of concave and convex surfaces of each contact lens.

CLs showed higher colony formation rates than daily or extended wear CLs (Table 2, Fig. 2A). Adhesion of P. aeruginosa on CLs was greater than adhesion of S. aureus for all types of CLs at all measured time points. Even after 1 hr of immersion, significant CFUs of P. aeruginosa were attached to CLs, and the CFU continuously increased until 24 hr. Similar to S. aureus, the number of P. aeruginosa colonies was higher for Cos-CLs than for Con-CLs at all time points and for all three wearing types (Table 2, Fig. 2B). When comparing bacterial adhesion between Con-CL and Cos-CL, composed of Etafilcon A, CFU of each bacteria adhering to Cos-CLs within 1 hr was significantly increased than those adhering to ConCLs (Fig. 3). © 2014 Contact Lens Association of Ophthalmologists

Determination of Surface Roughness of Cosmetic and Conventional Contact Lenses The surface roughness of CLs was measured with two different methods, AFM and SEM. As shown in the representative AFM images, the white spots representing a higher area of the surface were significantly greater in Cos-CLs, for daily, extended, and continuous wearing CLs (Table 3, Fig. 4). The Ra was approximately three times higher in Cos-CLs than Con-CLs but was not significant. When comparing roughness through Rq and Rz analyses, the surface roughness was significantly higher in Cos-CLs than Con-CLs (Fig. 5). Because color-tinting process may affect the surface roughness measurements, we measured convex and concave surface 29


Y. W. Ji et al.


FIG. 5. Comparison of surface roughness between Cos-CLs and Con-CLs, composed of same material, Etafilcon A (*P,0.05, †P,0.01 by independent t test). A, Concave surface roughness of CL; B, Convex surface roughness of CL; Cos-CL, cosmetic contact lens; Con-CL, conventional contact lens.

FIG. 6. Scanning electron microscopy of Cos-CL surface and bacterial adhesions. Different types of Cos-CLs were separately immersed in solutions containing Staphylococcus aureus or Pseudomonas aeruginosa for 24 hr. (A) Color-tinted area of Cos-CL, composed of Etafilcon A, was rougher than the nontinted area (·100). (B) Color-tinted area of Cos-CL, composed of 2-HEMA, was more irregular than the non-tinted area (·300). (C) Pseudomonas aeruginosa adhered to irregular surfaces of Etafilcon A Cos-CLs. In particular, more bacterial adhesions were found on the color-tinted area (·2,000). (D) Pseudomonas aeruginosa and (E) S. aureus adhesion to surfaces of Etafilcon A Cos-CLs at high magnification (·10,000). (F) Staphylococcus aureus appeared to be accumulating and mucoid material was present around the bacterial cells, forming a biofilm on the surface of 2HEMA Cos-CLs. N, non-tinted area; C, color-tinted area; white arrow head, P. aeruginosa adhesions; CosCL, cosmetic contact lens.

30





roughness of each CL. Neither Con-CLs nor Cos-CLs showed a significant difference in surface roughness between concave and convex surfaces. However, the Cos-CLs were significantly rougher than the Con-CLs on both surfaces. Among the Con-CLs, the Rz of continuous wear CLs was more than four times higher than that of the daily wear CLs (Table 3). Scanning electron microscopy examinations supported the AFM data. On Cos-CLs, the color-tinted areas showed more elevated reticular and scale-like surfaces than the noncolored areas. After immersion of Cos-CLs in bacterial solution and washing, higher numbers of P. aeruginosa or S. aureus were observed on the rough surfaces of the color-tinted areas than on the smooth surfaces. Additionally, for 2-HEMA Cos-CL, S. aureus seemed to accumulate with a mucus-like material around the aggregated bacterial cells, forming a biofilm on the surface (Fig. 6).

Correlation of Surface Roughness and Bacterial Adhesion As shown in Table 1, daily and extended wear CLs are composed of the same material, Etafilcon A. The correlation between CL surface roughness and bacterial adhesion was investigated among the four Etafilcon A CLs. Interestingly, the surface roughness was significantly positively correlated with CFUs of S. aureus and P. aeruginosa (Fig. 7).

Removal of Adherent Bacteria From Contact Lenses We compared hand rubbing for 3 min followed by immersion in MPDS with immersion in MPDS alone. After hand rubbing followed by 6 hr of immersion in MPDS, no colony formation of P. aeruginosa or S. aureus was observed. After hand rubbing with 1-hr immersion in MPDS, all types of CLs showed fewer than 10 CFUs. Interestingly, no P. aeruginosa remained after soaking in disinfectant for 6 hr, even without hand rubbing. However, under the same conditions, many S. aureus remained adhered to the surface of CLs and more than 100 CFUs were observed. Regardless of disinfection technique or CL type, more bacterial colonies were detected on the surface of Cos-CL than that of Con-CL (Table 4).

DISCUSSION This study demonstrates that Cos-CLs have more irregular and rougher surfaces than Con-CLs, which could facilitate bacterial attachment onto the surface. Interestingly, bacterial adhesion was highest in the tinted area of Cos-CLs. Compared with S. aureus, P. aeruginosa showed faster attachment onto all types of CL. However, P. aeruginosa was more easily removed from the surface of CLs than S. aureus by MPDS soaking alone or in combination with hand scrubbing.

Relationship Between Surface Roughness and Bacterial Adhesion Although there have been no comparative studies of the incidence of MK between Con-CLs and Cos-CLs, several cases of MK in individuals who used Cos-CLs have been reported by Singh et al.19 and Snyder et al.20 Previous studies have proposed factors that may be associated with MK in individuals who wear © 2014 Contact Lens Association of Ophthalmologists

FIG. 7. Correlation of surface roughness and initial (within 1 hr) bacterial adhesion to CL composed of same material, Etafilcon A. Bacterial adhesion by Staphylococcus aureus (A) or Pseudomonas aeruginosa (B) was analyzed with respect to measured CL roughness (r, Pearson correlation coefficient, 21#r#1). CL, contact lens.

Cos-CLs. These include influential commercials and easy availability of CLs and increased use in younger individuals of middle to lower socioeconomic classes who may be unaware and uninformed of the proper use and care of CLs.19,21 However, even though the manufacturing process is quite different from those of Con-CLs, no study has investigated the relationship between physical properties and bacterial adhesion to Cos-CLs. Our study shows that facilitated bacterial adhesion and proliferation may be related to the increased MK rate in Cos-CL wearers.

31



Y. W. Ji et al. TABLE 4.

Comparison of Bacterial Removal From Contact Lenses by Soaking in MPDS Soaking With and Without Hand Rubbing Non-Rubbing MPDS Soaking Time: 1 hr Conventional

Staphylococcus aureusa Daily wear Extended wear Continuous wear Pseudomonas aeruginosab Daily wear Extended wear Continuous wear

16 60 242 3 3.8 5.6

Cosmetic 64 90 318 3.4 4.8 6

Rubbing for 3 min With MPDS

MPDS Soaking Time: 6 hr



Conventional

Cosmetic

Conventional

Cosmetic

Conventional

Cosmetic

0 2 68

0 24 178

6 8 8

6 8 10

0 0 0

0 0 0

0 0 0

0 0 0

2 2 4

2 2 6

0 0 0

0 0 0


a


b

MPDS, multipurpose disinfecting solution; CFU, colony-forming unit.

We showed that Cos-CLs have a rougher surface than Con-CLs by AFM measurements. To prevent measurement error, we used three parameters (Ra, Rq, and Rz) to compare the surface roughness between the CLs. The Ra index is calculated by averaging the differences of each peak(+) and valley(2) with the average height of surface. But Ra is not effective in discrimination of different surface roughness because different roughness may present as equivalent Ra because of canceling out of peaks(+) and valleys(2). The Rq index squares the standard deviation of peaks and valleys from the average height of the surface and is profoundly affected by severely extruded or depressed surfaces. The Rq value can be affected by artifacts; thus, the Rz value, which is the sum of averages of peaks and valleys of 10 random points, may be helpful in indicating spaces in which foreign bodies may be captured. In this study, the Ra value did not show significant differences between the CLs. However, Rq and Rz values were significantly higher in Cos-CLs. Through manufacturing process as compression color-tint between two clear layers like sandwich, an inevitable irregular surface on Cos-CL is made. Although this nanoscopic changes on Cos-CL may not result in corneal damage or refractive errors, it is significant in bacterial settings. Because the size of a bacterial cell is approximately 1 to 3 mm, 100 to 1000 nm difference in surface roughness is significant enough to allow larger contact area for bacterial entrapment. We found a positive correlation between bacterial adhesion at 1 hr of CL immersion and surface roughness. However, at 12 and 24 hr of CL immersion, there were no significant differences between the CLs. This may indicate that roughness is important for only the initial bacterial adhesion. Therefore, a smooth CL surface will not prevent bacterial adhesion but merely delay bacterial attachment. The smoothness and electrical charge on the CL surface have previously been shown to be related to bacterial adhesion. In particular, an increased surface roughness caused more bacterial adhesion.16,22 Bruinsma et al.23 reported that the surface roughness was increased by CL wearing time, which was an important predictive factor for P. aeruginosa adhesion to Etafilcon A lenses. The surface roughness of CLs ranged from 4 nm for an unused lens to 10 nm after wearing, which caused a significant impact on P. aeruginosa adhesion. The present study showed greater than 100 nm roughness of Cos-CLs compared with less than 10 nm for Con-CLs. Therefore, surface roughness of Cos-CLs may be associated with risk for bacterial keratitis. 32

Differences in Bacterial Adhesion Between S. aureus and P. aeruginosa Pseudomonas aeruginosa showed greater adhesion to the CL surface than S. aureus, but the attached P. aeruginosa was easily removed from the CL by MPDS alone or hand rubbing with MPDS. In contrast, many CFUs of S. aureus remained on the lens surface after rubbing and MPDS soaking. It is well known that two important CL factors affecting bacterial adhesion are surface roughness and hydrophobicity.11,12 As we demonstrated, surface roughness showed good correlation with bacterial adhesion of S. aureus or P. aeruginosa. However, hydrophobicity of the CLs was not investigated in this study and it should be evaluated in the future. We also found that P. aeruginosa was attached more on Etafilcon A surface compared with S. aureus, which is consistent with previous study by Borazjani et al.24 Beside the above two factors, the cell surface hydrophobicity of P. aeruginosa also contributes to its adhesion to CLs.13,25 The prominent adhesive nature of P. aeruginosa is the result of its unique physiochemical characteristics. Organisms with greater surface hydrophobicity adhere in greater numbers than hydrophilic organisms. This phenomenon could explain the greater adhesive nature of P. aeruginosa than S. aureus. Cho et al.26 reported that rubbing was more effective for removing deposits than non-rubbing methods, irrespective of the solution used. The simple mechanical force applied by the fingers during the rubbing process provides more effective removal of debris and bacteria. Our results are in agreement with these findings. Another interesting finding from the present study is that rubbing was more effective for the removal of P. aeruginosa than S. aureus from CLs. We found that S. aureus was more tightly bound to Etafilcon A CLs than P. aeruginosa, which was easier to remove. However, different CL materials may show different binding affinities, and thus, future studies using CLs of other materials should be performed. Although we used six types of CLs and two types of bacteria to analyze surface roughness and bacterial adhesion, the relatively few materials and bacterial types (only one representative strain of each gram-positive and gram-negative bacteria) could be considered a limitation of our work. It is well known that many bacterial species and bacterial serostrains are involved in MK and many other CL materials are available. Therefore, our results may not apply to all bacteria and all cosmetic or conventional silicone hydrogel lenses. Eye & Contact Lens Volume 41, Number 1, January 2015


Eye & Contact Lens Volume 41, Number 1, January 2015 However, we used representative bacterial strains that are known to colonize.3,27 Etafilcon A is one of the most popular CL polymer, and thus, it can be considered a representative material for comparison between Con-CLs and Cos-CLs. In addition, we did not perform in vivo experiments or analyze clinical data. Future studies to determine the mechanism of MK could be performed using several types of Cos-CLs and various serotypes of bacteria. In conclusion, Cos-CLs are now frequently dispensed without a prescription in many countries. Compared with Con-CLs, CosCLs are rougher and more easily contaminated with bacteria. To avoid serious vision problems, such as MK, Cos-CL wearers should be educated on the risks, and manufacturing processes could be adapted to produce lenses with a smoother surface or surface treatment to inhibit bacterial adhesion. REFERENCES 1. Efron N, Morgan PB, Woods CA, et al. International survey of contact lens prescribing for extended wear. Optom Vis Sci 2012;89:122–129. 2. Efron N, Morgan PB, Woods CA, et al. An international survey of daily disposable contact lens prescribing. Clin Exp Optom 2013;96:58–64. 3. Sauer A, Bourcier T; French Study Group for Contact Lenses Related Microbial Keratitis. Microbial keratitis as a foreseeable complication of cosmetic contact lenses: A prospective study. Acta Ophthalmol 2011;89: e439–e442. 4. Stapleton F, Keay L, Edwards K, et al. The incidence of contact lens-related microbial keratitis in Australia. Ophthalmology 2008;115:1655–1662. 5. Schein OD, McNally JJ, Katz J, et al. The incidence of microbial keratitis among wearers of a 30-day silicone hydrogel extended-wear contact lens. Ophthalmology 2005;112:2172–2179. 6. Robertson DM, Parks QM, Young RL, et al. Disruption of contact lensassociated Pseudomonas aeruginosa biofilms formed in the presence of neutrophils. Invest Ophthalmol Vis Sci 2011;52:2844–2850. 7. Evans DJ, Fleiszig SM. Microbial keratitis: Could contact lens material affect disease pathogenesis? Eye Contact Lens 2013;39:73–78. 8. Babaei Omali N, Zhu H, Zhao Z, et al. Effect of cholesterol deposition on bacterial adhesion to contact lenses. Optom Vis Sci 2011;88:950–958. 9. Selan L, Palma S, Scoarughi GL, et al. Phosphorylcholine impairs susceptibility to biofilm formation of hydrogel contact lenses. Am J Ophthalmol 2009;147:134–139. 10. Willcox M, Sharma S, Naduvilath TJ, et al. External ocular surface and lens microbiota in contact lens wearers with corneal infiltrates during extended wear of hydrogel lenses. Eye Contact Lens 2011; 37:90–95.

© 2014 Contact Lens Association of Ophthalmologists

Surface Roughness of Cosmetic Lens on Bacterial Adhesion 11. Willcox MD. Microbial adhesion to silicone hydrogel lenses: A review. Eye Contact Lens 2013;39:61–66. 12. Shen EP, Tsay RY, Chia JS, et al. The role of type III secretion system and lens material on adhesion of Pseudomonas aeruginosa to contact lenses. Invest Ophthalmol Vis Sci 2012;53:6416–6426. 13. Dutta D, Cole N, Willcox M. Factors influencing bacterial adhesion to contact lenses. Mol Vis 2012;18:14–21. 14. Tang H, Cao T, Liang X, et al. Influence of silicone surface roughness and hydrophobicity on adhesion and colonization of Staphylococcus epidermidis. J Biomed Mater Res A 2009;88:454–463. 15. Giraldez MJ, Serra C, Lira M, et al. Soft contact lens surface profile by atomic force microscopy. Optom Vis Sci 2010;87:E475–E481. 16. Geoghegan M, Andrews JS, Biggs CA, et al. The polymer physics and chemistry of microbial cell attachment and adhesion. Faraday Discuss 2008;139:85–103, discussion 105–128, 419–120. 17. Desrousseaux C, Sautou V, Descamps S, et al. Modification of the surfaces of medical devices to prevent microbial adhesion and biofilm formation. J Hosp Infect 2013;85:87–93. 18. Kim JH, Song JS, Hyon JY, et al. A survey of contact lens-related complications in Korea: The Korean Contact Lens Study Society. J Korean Ophthalmol Soc 2014;55:20–31. 19. Singh S, Satani D, Patel A, et al. Colored cosmetic contact lenses: An unsafe trend in the younger generation. Cornea 2012;31:777–779. 20. Snyder RW, Brenner MB, Wiley L, et al. Microbial keratitis associated with plano tinted contact lenses. CLAO J 1991;17:252–255. 21. Gagnon MR, Walter KA. A case of acanthamoeba keratitis as a result of a cosmetic contact lens. Eye Contact Lens 2006;32:37–38. 22. Giraldez MJ, Resua CG, Lira M, et al. Contact lens hydrophobicity and roughness effects on bacterial adhesion. Optom Vis Sci 2010;87: E426–E431. 23. Bruinsma GM, Rustema-Abbing M, de Vries J, et al. Influence of wear and overwear on surface properties of etafilcon A contact lenses and adhesion of Pseudomonas aeruginosa. Invest Ophthalmol Vis Sci 2002; 43:3646–3653. 24. Borazjani RN, Levy B, Ahearn DG. Relative primary adhesion of Pseudomonas aeruginosa, Serratia marcescens and Staphylococcus aureus to HEMA-type contact lenses and an extended wear silicone hydrogel contact lens of high oxygen permeability. Cont Lens Anterior Eye 2004; 27:3–8. 25. Klotz SA, Butrus SI, Misra RP, et al. The contribution of bacterial surface hydrophobicity to the process of adherence of Pseudomonas aeruginosa to hydrophilic contact lenses. Curr Eye Res 1989;8:195–202. 26. Cho P, Cheng SY, Chan WY, et al. Soft contact lens cleaning: Rub or norub? Ophthalmic Physiol Opt 2009;29:49–57. 27. Vermeltfoort PB, Rustema-Abbing M, de Vries J, et al. Influence of day and night wear on surface properties of silicone hydrogel contact lenses and bacterial adhesion. Cornea 2006;25:516–523.

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Plasma surface modification of rigid contact lenses decreases bacterial adhesion.

Ocular prostheses and contact lenses. II--Contact lenses.

Ocular prostheses and contact lenses. I--Cosmetic devices.

Electric arcing and contact lenses.

Contact lenses in pregnancy.

Problems with contact lenses.

Bifocal contact lenses today.

Editorial: Soft contact lenses.

Soft contact lenses.

Therapeutic contact lenses.

Orange contact lenses from rifampin.

Fitting contact lenses after keratoplasty.

Extended-wear soft contact lenses.

[Contact lenses as therapeutic aid].

Warning about bacterial contamination of therapeutic contact lenses.

A laboratory assessment of factors that affect bacterial adhesion to contact lenses.

Contact lenses for infant aphakia.

Ocular surface displacement with and without contact lenses during non-contact tonometry.

Corneal endothelium damage with intraocular lenses: contact adhesion between surgical materials and tissue.

Prolonged wearing contact lenses and preliminary results.

Treatment of uniocular aphakia. A comparison of iris clip lenses with hard corneal contact lenses.

Therapeutic use of soft contact lenses.

Light transmission of hydrogel contact lenses.

Periocular migration of hard contact lenses.