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Effects of Pigment Location in Tinted Contact Lenses on the Ocular Surface

Jung, Ji Won; Han, Sun Hyup; Park, Si Yoon; Kim, Eung Kweon; Seo, Kyoung Yul; Kim, Tae-im

doi: 10.1097/OPX.0000000000000880
Original Articles

Purpose To evaluate the effects of the location of pigments in decorative tinted soft contact lenses on the ocular surface.

Methods Thirty test subjects were enrolled in this study. All subjects wore the following types of contact lenses, classified according to the location of the pigment layer, in one eye in three different testing sessions: conventional clear lenses, tinted lenses with a pigment layer embedded in the lens matrix, and tinted lenses with an exposed pigment layer on the surface. Tear samples were collected, the ocular surface status was evaluated, and subjective symptoms were surveyed after lens wear for 8 hours.

Results The tinted lenses with surface pigments resulted in a greater increase in epidermal growth factor and interleukin-8 levels compared with the clear lenses and tinted lenses with embedded pigments (p < 0.050). Ocular surface parameters and subjective symptom scores were significantly different among three lens types (p < 0.050), with the clear lenses showing superior results compared with the two tinted lenses (p < 0.050). The tinted lenses with exposed pigments resulted in a greater degree of conjunctival redness and ocular surface staining and poorer symptom scores compared with the tinted lens with embedded pigments (p < 0.050).

Conclusions Our results suggest that the presence of surface pigments in tinted contact lenses increases ocular inflammation and results in a poorer ocular surface status and greater discomfort compared with clear lenses and tinted lenses with an embedded pigment layer.

*MD

MD, PhD

The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of South Korea (JWJ, SHH, SYP, EKK, KYS, T-iK); Department of Ophthalmology and Inha Vision Science Laboratory, Inha University School of Medicine, Incheon, Republic of South Korea (JWJ); and Corneal Dystrophy Research Institute, Severance Biomedical Science Institute, and Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of South Korea (EKK).

Tae-im Kim Department of Ophthalmology Yonsei University College of Medicine 50 Yonsei-ro, Seodaemun-gu Seoul 120–752 Republic of South Korea e-mail: tikim@yuhs.ac

Of late, the use of decorative tinted soft contact lenses has been increasing, particularly in Asian countries.1 Tinted contact lenses comprise a central pigment-free optical zone and a peripheral pigmented area. Such lenses make the corneal diameter appear larger and impart different colors and patterns to the iris. Users primarily include adolescents, who purchase these cosmetic lenses without appropriate ophthalmological testing or prescriptions from ophthalmologists.2 Several countries have raised concerns regarding the improper use of tinted lenses, which expose their wearers to serious complications such as infectious keratitis.1–3

Because of the increasing popularity, the safety of tinted contact lenses has become an increasingly debated issue in the industry. Color printing and processing vary among manufacturers, and there has been growing interest in the location of the pigment layer in tinted lenses.4,5 Decorative tinted soft contact lenses can be divided into two types on the basis of the pigment location. The first type comprises a pigment layer embedded within the matrix, with no pigment particles exposed on the surface. The second type comprises a pigment layer on the front (convex) or back (concave) surface, which results in direct contact between the pigment particles and the palpebral conjunctiva or cornea.5 However, no conclusive research has been conducted to completely elucidate the effects of different color printing and processing methods on the safety of artificial material coming in direct contact with human tissue.

In our previous study,6 we suggested efficient methods for evaluating the location of pigments and showed that the roughness of the lens surface can be affected by the location of the pigment layer within the lens. Steffen and Barr have also suggested that tinted lenses with pigment particles exposed on the surface increase ocular discomfort compared with conventional clear lenses.7

From the above perspectives, we conducted this study to evaluate the effects of the location of pigments in tinted lenses on the ocular surface by comparing the two types of tinted lenses with clear lenses.

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METHODS

This prospective study was conducted with 30 healthy subjects with no history of ocular disease, previous ocular surgery, or systemic disorders that may affect the ocular surface status. Prescreening slit-lamp examinations were performed for all eyes to confirm the absence of ocular pathologies. Informed consent for participation in the study was obtained after the study protocol was fully explained. The study adheres to the tenets of the Declaration of Helsinki and has been approved by the Severance Hospital Institutional Review Board, Seoul, South Korea.

Three types of soft contact lenses with similar oxygen permeability were tested according to the location of the pigment layer: conventional clear lenses, tinted lenses with a pigment layer embedded in the matrix, and tinted lenses with an exposed pigment layer on the surface. Each test subject attended three testing sessions conducted at a minimum interval of 1 week. In every session, the participants wore one of the lenses in one eye for 8 hours. The order of lens wear was randomly chosen. To ensure masking, two investigators were involved in each testing session. One was assigned to randomize the order of lens wear and to apply and remove the lenses, whereas the other performed the tests and collected data without knowing the type of lens worn.

Fig. 1 shows the pigment locations in the tinted lenses on anterior segment Fourier-domain optical coherence tomography (FD-OCT) images. The same contact lenses were used in our previous study (unpublished data), and data obtained regarding the location of the pigment layer and the surface roughness are shown in Table 1. The roughness of the front surface near the pigment layer was significantly higher for the tinted lenses with surface pigments than for the tinted lenses with embedded pigments. However, there was no difference in roughness between the lenses with embedded pigments and the clear lenses.

TABLE 1

TABLE 1

FIGURE 1

FIGURE 1

Each subject wore the designated lenses for 8 hours, following which they were carefully removed to avoid any irritation to the ocular surface before testing. Tear samples were collected for tear cytokine analysis, four ocular surface parameters were evaluated using the Efron grading scale, and subjective symptom scores were obtained from the participants for each session.

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Tear Collection and Multiplex Bead Analysis

Tear samples were collected by injecting 30 μL of phosphate-buffered saline into the inferior fornix.8 A micropipette was used to collect 20 μL of tear fluid and buffer from the medial and lateral canthi. Ocular surface irritation was minimized by collection from the marginal tear strip of the lower lid near the lateral canthus without the use of anesthetic eye drops. The samples were transferred into 0.5-mL Eppendorf tubes (Eppendorf, Fremont, CA) and stored at −70°C until further analysis by immunoassay.

Tear cytokines were analyzed using immunoassay kits and panels [Millipore MILLIPLEX MAP Human Cytokine/Chemokine Magnetic Bead Panel I-6 Plex (HCYTOMAG-60K-06)] with a magnetic bead-based immunoassay kit (Luminex 200; Luminex Corp., Austin, TX). The analyzed cytokines included epidermal growth factor (EGF), interleukin (IL)-17α, IL-6, IL-8, tumor necrosis factor (TNF)-α, and vascular endothelial growth factor (VEGF). Tear samples were incubated with antibody-coated capture beads overnight at 4°C. After washing, the beads were further incubated with biotin-labeled anti-human cytokine antibodies, followed by streptavidin–phycoerythrin incubation. For the conversion of fluorescence units to concentrations (pg/mL), the standard curve of known concentrations of recombinant human cytokines/chemokines was used. Molecular concentrations in tear samples were calculated by analyzing the median fluorescent intensity data using a five-parameter logistic or spline curve-fitting method.

The minimum concentrations of tear cytokines for detection were as follows: EGF, 2.8 pg/mL; IL-17α, 0.7 pg/mL; IL-6, 0.9 pg/mL; IL-8, 0.4 pg/mL; TNF-α, 0.7 pg/mL; and VEGF, 26.3 pg/mL. The minimum detectable concentration was used for statistical comparisons among tear samples with concentrations below the detection limit in the linear portion of the standard curve.

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Evaluation of Ocular Surface Parameters

Under slit-lamp examinations, four ocular surface parameters, including conjunctival redness, limbal redness, corneal staining, and conjunctival staining, were evaluated using the Efron grading scale.9

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Subjective Symptom Scores after Lens Wear

Subjective scores for ocular comfort, dryness, lens awareness, and vision after lens wear were collected from the participants for each session. The participants rated several predetermined questions using a scale from 1 to 10, where 1 represented poor and 10 represented excellent.10

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Statistical Analysis

The results for the three lens types worn in the same eye were compared using repeated-measures analysis of variance (ANOVA) incorporating, where necessary, a Greenhouse–Geisser correction for nonsphericity. If significant differences were observed with the ANOVA test, paired t-tests were performed to determine significant differences among the three lenses. Because of multiple comparisons, an adjusted p-value was used after Bonferroni correction. A p-value of <0.050 was considered statistically significant.

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RESULTS

One eye of each test subject (11 men and 19 women) was randomly selected for this study. The average age and spherical equivalent were 30.2 ± 4.19 years and −1.87 ± 1.96 diopters.

The inflammatory cytokine levels in the tear samples are shown in Table 2. There were significant differences in cytokine levels, particularly EGF and IL-8 levels, among the three lenses. The mean concentrations of EGF were 206.52 ± 47.63, 268.71 ± 38.77, and 458.68 ± 66.87 pg/mL for the clear lenses, tinted lenses with embedded pigments, and lenses with surface pigments, respectively (p = 0.019), whereas those of IL-8 were 34.54 ± 10.64, 33.21 ± 7.94, and 150.09 ± 77.42 pg/mL, respectively (p = 0.043). Post hoc analyses using paired t-tests showed significantly higher EGF and IL-8 levels after wear of the tinted lens with surface pigments than after wear of the tinted lenses with embedded pigments and the clear lenses (p < 0.050).

TABLE 2

TABLE 2

Figs. 2A and 3 show the ocular surface status after wear of the three lens types for 8 hours. The ocular surface status was significantly different among the three lens types (all p < 0.050). Post hoc analyses using paired t-tests showed a superior ocular surface status for the clear lenses than for the two tinted lenses (all p < 0.050), with significantly increased conjunctival redness, corneal staining, and conjunctival staining with the tinted lenses with surface pigments than with the tinted lenses with embedded pigments (p < 0.050).

FIGURE 2

FIGURE 2

FIGURE 3

FIGURE 3

The subjective symptom scores for the three lens types are shown in Fig. 2B. Significant differences in all scores except those for overall vision were observed among the three lens types (p < 0.050). Post hoc analysis revealed that the scores for most symptoms were lower for the tinted lenses than for the clear lenses (p < 0.050). Scores for comfort at the end of the day and burning and stinging sensations were significantly lower for the tinted lens with surface pigments than for the tinted lenses with embedded pigments (p = 0.021 and 0.036, respectively).

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DISCUSSION

In the present study, we evaluated the effects of the location of pigments in tinted lenses on the ocular surface by comparing tinted lenses with surface pigments, tinted lenses with embedded pigments, and clear lenses with regard to the ocular surface status, inflammatory cytokine levels in tear samples, and subjective symptom scores. Our results suggest that tinted soft contact lenses, particularly those with surface pigments, result in more adverse effects on the ocular surface.

Tinted soft contact lenses differ from conventional clear lenses in that they have an added pigment layer in the peripheral region. Infective keratitis associated with the use of cosmetic tinted contact lenses can be primarily attributed to the improper use of tinted lenses without professional consultation, primarily by adolescents, who are identified as the characteristic consumer population.2,3 Previous case reports have documented corneal pigmentation secondary to tinted lens wear and pigment deposition from tinted lenses after intense pulsed light treatment.11,12 Although the pigment location in tinted lenses has recently been suggested as another potential cause for complications associated with the use of tinted contact lenses,13,14 the correlation between the presence of surface pigments and adverse events associated with tinted lens wear is not fully investigated.

Lorenz et al.5 recently demonstrated that the surface roughness of the pigmented area was significantly greater than that of the non-pigmented area in tinted lenses. In addition, the surface roughness of lenses with surface pigments was greater than that of lenses with embedded pigments. Several studies have reported that a rough lens surface increases microbial adherence.13,14 One report also suggested that pigment particles expose on the surface of tinted lenses alter the surface roughness and lens wettability and cause increased ocular discomfort.7

A report has stressed on the importance of the pre-lens tear film, which affects ocular comfort,15 and how it is affected by the pigment location in tinted lenses through alteration of the surface roughness and lens wettability. Therefore, we evaluated the effect of the location of pigment layers in tinted soft contact lenses on the human ocular surface through comparisons with clear lenses.

Several studies related to the ocular inflammatory response after contact lens wear have been published.16–19 González-Pérez et al.17 compared tear film inflammatory mediator levels between silicone–hydrogel and rigid contact lenses. Efron also used confocal microscopy to examine the density of Langerhans cells after contact lens wear and confirmed a subclinical inflammatory response.20 Our study showed that eyes wearing tinted lenses with surface pigments were more prone to inflammation of the ocular surface compared with those wearing clear lenses or tinted lens with embedded pigments. A previous study showed an increase in the levels of EGF and IL-8, among several cytokines, after contact lens wear.19 EGF presents in human tears and is induced in response to stimulation of the corneal epithelium, whereas IL-8 serves as a potent neutrophil chemotactic agent and an activating factor that increases in response to ocular surface inflammation. The authors of a previous study19 suggested mechanical stimulation of the corneal surface by the physical presence of contact lenses as the cause of inflammatory mediator release. Therefore, exposed pigment particles on lens surfaces can increase the surface roughness and induce mechanical irritation of the ocular surface, resulting in a greater inflammatory response. In turn, ocular surface inflammation may worsen the ocular surface status and subjective symptoms.

Steffen and Barr7 demonstrated that tinted soft contact lenses resulted in increased ocular discomfort during wear compared with clear lenses. They found pigment particles exposed on the surface of the tinted lenses using a microscope and suggested that the consequent rugged surface altered the surface roughness and lens wettability, eventually decreasing the comfort of wear. Our study showed that pigment location and surface roughness significantly affected ocular comfort, thus supporting the hypothesis proposed by Steffen and Barr. Recently, the possible mechanism underlying lens discomfort was studied with regard to the lens surface lubricity, which mechanically affects the conjunctival palpebral surface.21 The coefficient of friction for the lens surface demonstrated a significant correlation with comfort at the end of the day. In the present study, tinted lenses with embedded pigments worsened the ocular surface status and subjective symptom scores compared with clear lenses, even though there were no significant differences in the surface roughness and degree of ocular surface inflammation between the two types. Several factors are associated with contact lens comfort, including the lens modulus, interaction of the lens edge with the upper lid, and chemical characteristics of the lens surface. These factors were previously reported to be associated with tear film disruption or ocular surface drying and tear evaporation from the lens surface.22,23 Our study design makes it difficult to elucidate the precise mechanism underlying this discrepancy. Further studies on other possible factors that influence contact lens comfort should be conducted using tinted lenses with embedded pigments and clear lenses.

In conclusion, our results suggest that tinted soft contact lenses with an exposed pigment layer on the surface and increased surface roughness result in more adverse effects on the ocular surface compared with conventional clear lenses and tinted lenses with an embedded pigment layer, with more severe ocular surface inflammation and mechanical stimulation worsening the ocular surface status and subjective symptoms.

Tae-im Kim

Department of Ophthalmology

Yonsei University College of Medicine

50 Yonsei-ro, Seodaemun-gu

Seoul 120–752

Republic of South Korea

e-mail: tikim@yuhs.ac

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ACKNOWLEDGMENTS

This study was partially supported by a grant (14172MFDS379) from the Ministry of Food and Drug Safety (Seoul, Republic of South Korea) in 2014 and by a faculty research grant of Yonsei University College of Medicine for 2008 (6-2008-0133).

None of the authors have any conflicts of interest to declare.

Received August 31, 2015; accepted February 2, 2016.

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REFERENCES

1. Rah MJ, Schafer J, Zhang L, Chan O, Roy L, Barr JT. A meta-analysis of studies on cosmetically tinted soft contact lenses. Clin Ophthalmol 2013;7:2037–42.
2. Singh S, Satani D, Patel A, Vhankade R. Colored cosmetic contact lenses: an unsafe trend in the younger generation. Cornea 2012;31:777–9.
3. Steinemann TL, Fletcher M, Bonny AE, Harvey RA, Hamlin D, Zloty P, Besson M, Walter K, Gagnon M. Over-the-counter decorative contact lenses: cosmetic or medical devices? A case series. Eye Contact Lens 2005;31:194–200.
4. Lazarus M. Cosmetic and prosthetic contact lenses. In: Phillips AJ, Speedwell L. Contact Lenses, 5th ed. Oxford: Elsevier Butterworth-Heinemann; 2007;519–30.
5. Lorenz KO, Kakkassery J, Boree D, Pinto D. Atomic force microscopy and scanning electron microscopy analysis of daily disposable limbal ring contact lenses. Clin Exp Optom 2014;97:411–7.
6. Jung JW, Han SH, Kim SA, Kim EK, Seo KY, Kim TI. Evaluation of pigment location in tinted soft contact lenses. Cont Lens Anterior Eye 2016;42 (Feb. 2):epub ahead of print:doi 10.1016/j.clae.2016.01.008.
7. Steffen RB, Barr J. Clear versus opaque soft contact lenses: initial comfort comparison. Int Contact Lens Clin 1993;20:184–6.
8. Lee H, Min K, Kim EK, Kim TI. Minocycline controls clinical outcomes and inflammatory cytokines in moderate and severe meibomian gland dysfunction. Am J Ophthalmol 2012;154:949–57.
9. Efron N. Contact Lens Complications. Oxford: Butterworth-Heinemann; 1999.
10. Diec J, Evans VE, Tilia D, Naduvilath T, Holden BA, Lazon de la Jara P. Comparison of ocular comfort, vision, and SICS during silicone hydrogel contact lens daily wear. Eye Contact Lens 2012;38:2–6.
11. Spiteri N, Choudhary A, Kaye S. Pigmentation of the cornea secondary to tinted soft contact lens wear. Case Rep Ophthalmol Med 2012;2012:852304.
12. Hong S, Lee JR, Lim T. Pigment deposition of cosmetic contact lenses on the cornea after intense pulsed-light treatment. Korean J Ophthalmol 2010;24:367–70.
13. Ji YW, Cho YJ, Lee CH, Hong SH, Chung DY, Kim EK, Lee HK. Comparison of surface roughness and bacterial adhesion between cosmetic contact lenses and conventional contact lenses. Eye Contact Lens 2015;41:25–33.
14. Chan KY, Cho P, Boost M. Microbial adherence to cosmetic contact lenses. Cont Lens Anterior Eye 2014;37:267–72.
15. Young G, Efron N. Characteristics of the pre-lens tear film during hydrogel contact lens wear. Ophthalmic Physiol Opt 1991;11:53–8.
16. Efron N. Is contact lens wear inflammatory? Br J Ophthalmol 2012;96:1447–8.
17. González-Pérez J, Villa-Collar C, Sobrino Moreiras T, Lema Gesto I, González-Méijome JM, Rodríguez-Ares MT, Parafita M. Tear film inflammatory mediators during continuous wear of contact lenses and corneal refractive therapy. Br J Ophthalmol 2012;96:1092–8.
18. Thakur A, Willcox MD. Cytokine and lipid inflammatory mediator profile of human tears during contact lens associated inflammatory diseases. Exp Eye Res 1998;67:9–19.
19. Kallinikos P, Morgan PB, Efron N. Assessment of stromal keratocytes and tear film inflammatory mediators during extended wear of contact lenses. Cornea 2006;25:1–10.
20. Efron N. Contact lens-induced changes in the anterior eye as observed in vivo with the confocal microscope. Prog Retin Eye Res 2007;26:398–436.
21. Jones L, Brennan NA, González-Méijome J, Lally J, Maldonado-Codina C, Schmidt TA, Subbaraman L, Young G, Nichols JJ. The TFOS International Workshop on Contact Lens Discomfort: report of the contact lens materials, design, and care subcommittee. Invest Ophthalmol Vis Sci 2013;54:TFOS37–70.
22. Grobe GL 3rd, Valint PL Jr, Ammon DM Jr. Surface chemical structure for soft contact lenses as a function of polymer processing. J Biomed Mater Res 1996;32:45–54.
23. Craig JP, Willcox MD, Argüeso P, Maissa C, Stahl U, Tomlinson A, Wang J, Yokoi N, Stapleton F. The TFOS International Workshop on Contact Lens Discomfort: report of the contact lens interactions with the tear film subcommittee. Invest Ophthalmol Vis Sci 2013;54:TFOS123–56.
Keywords:

decorative tinted soft contact lens; tear cytokines; pigment location; surface roughness; contact lens comfort

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