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Contact Lens & Anterior Eye 37 (2014) 451–454

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Contact Lens & Anterior Eye journal homepage: www.elsevier.com/locate/clae

Spectral transmittance of UV-blocking soft contact lenses: A comparative study Saeed Rahmani a , Mohadeseh Mohammadi Nia a,∗ , Alireza Akbarzadeh Baghban b , Mohammad Reza Nazari a , Mohammad Ghassemi-Broumand a a b

Department of Optometry, Faculty of Rehabilitation Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Faculty of Rehabilitation Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

a r t i c l e

i n f o

Article history: Received 17 March 2014 Received in revised form 15 June 2014 Accepted 21 July 2014 Keywords: Contact lens UV-blocking Spectral transmittance Visible light

a b s t r a c t Background: Three major parts of sunlight consist of visible, ultraviolet and infrared radiation. Exposure to ultraviolet radiation (UVR) can result in a spectrum of skin and ocular diseases. UV-blocking contact lenses help provide protection against harmful UV radiation. We studied the ultraviolet and visible light rays transmission in some soft UV-blocking contact lenses. Material and methods: Four available tinted soft lenses (Acuvue Moist, Zeiss CONTACT Day 30 Air spheric, Pretty Eyes and Sauflon 56 UV) have been evaluated for UV and visible transmission. One-way ANOVA testing was performed to establish is there a statistically significant difference between the UV regions and visible spectra means for the contact lenses (˛ = 0.05). Results: Pretty Eyes, Zeiss CONTACT, Acuvue Moist and Sauflon 56 UV showed UV-B transmittance value of 0.65%, 10.69%, 1.22%, and 5.78%, respectively. Pretty Eyes and Acuvue Moist had UV-A transmittance values of 32% and 34%, Sauflon 56 UV and Zeiss CONTACT had transmittance values of 48% and 43%, respectively. All of the studied lenses transmitted at least 94.6% on the visible spectrum. The results of the one-way ANOVA statistical analysis show that a statistically significant difference exists within the group of contact lenses tested for the visible (p < 0.001), UV-B (p < 0.001) and UV-A (p < 0.001) portions of the spectrum (˛ = 0.05). Conclusion: Acuvue Moist has the best UV-blocking property and also visible transmission between other tested contact lenses in this study. © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

1. Introduction Previous studies indicated that exposure to ultraviolet radiation (UVR) has been linked to a spectrum of skin and eye diseases [1–3]. Clinical studies have demonstrated pathology to the eyelids, cornea, conjunctiva and iris after ultraviolet B exposure [4] and suggested a correlation with cataract and age-related macular degeneration [3,5–8]. In addition, World Health Organization (WHO) estimates worldwide some 12–15 million people become blind from cataracts annually, of which up to 20% may be caused or enhanced by sun exposure [9].

∗ Corresponding author at: Imam Hossien Square, Damavand Avenue, Faculty of Rehabilitation Sciences, Department of Optometry, Shahid Beheshti University of Medical Sciences, Tehran 16169-13111, Iran. Tel.: +98 21 77458865; fax: +98 21 77458865. E-mail addresses: [email protected] (S. Rahmani), [email protected] (M. Mohammadi Nia), [email protected] (M.R. Nazari), [email protected] (M. Ghassemi-Broumand).

The sun is the main UVR source on the earth. UVR covers a range of wavelengths from 100 to about 400 nm which is often broken down into three regions: UV-C (200–290 nm), UV-B (290–315 nm), and UV-A (315–400 nm). UV-C emitted by the sun is completely absorbed by ozone layer in the upper atmosphere and does not reach the surface of the earth [10]. However, recent environmental condition, such as ozone depletion can lead to increased UV radiation exposure. Both UV-A and UV-B are found in the sunlight and have been implicated as potential hazards to the eye [11]. The human eye has been shown to absorb afferent bands of UV radiation; for instance, the cornea absorbs all UV-C and some UV-B [12], whereas the crystalline lenses preferentially absorb some UV-B and some UV-A [13–15]. The retina absorbs small amount of UV-B and all of UV-A [13,15,16]. There are several protective ways to reduce the risk of UVR potential damage to the eyes, such as avoidance of direct sunlight exposure, use of UVR-blocking eyewear (sunglasses) and hats. Most styles of sunglasses do not prevent all UV rays from reaching the eyes because direct and reflected sunlight can shine through the sides, top and bottom of sunglasses. This is known as

http://dx.doi.org/10.1016/j.clae.2014.07.011 1367-0484/© 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

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S. Rahmani et al. / Contact Lens & Anterior Eye 37 (2014) 451–454

the peripheral light focusing effect (PLF) [17]. These peripheral rays or tangentially incident UVR may be more dangerous than those entering the eye along the visual axis. Tangentially incident UVR is believed to be important in the development of pterygium [18]. Studies have shown that UV-blocking contact lenses can also help block the peripheral light that sunglasses cannot block [17,18]. Contact lenses that offer protection against UV rays are labeled as Class 1 and Class 2. The different classes indicate the level of UV protection. The U.S. Food and Drug Administration (FDA) has criteria for UV-blocking contact lenses based on American National Standards Institute (ANSI) Z80.20 standards. There are two different classifications of UV-blocking lenses. FDA Class 1 lenses block 90% of UV-A rays and 99% of UV-B rays. FDA Class 2 lenses block 70% of UV-A and 95% of UV-B radiation. Class 2 blockers are better than not having any UV protection and are recommended for general environments. FDA Class 1 blockers are recommended for high exposure environments such as mountains or beaches [19]. With these facts in mind, this study was designed to evaluate and compare the UV-A, UV-B and visible transmittance characteristics of some currently available UV-blocking soft contact lenses that are manufactured by companies from different countries, and some of them have not been evaluated before.

transmittance of a soft contact lens has been used in previous studies [15,22–24]. Each contact lens was removed from the blister pack or vial using tweezers, after that, inserted into the measurement holder. This holder was then placed within the spectrophotometer. Before conducting each test, the baseline transmittance of the reference cell was measured and recorded. The scan was performed at 0.5 nm intervals at a scan speed of 10 nm/s for the waveband 290–760 nm and optical bandwidth of 4 nm. Spectral transmittance (UV-A, UV-B and visible) was measured three times for each of the three lenses measured within each brand. Using SPSS software, one-way analysis of variance (ANOVA) testing was performed to establish whether a statistically significant difference (p < 0.05) existed between the UV-B, UV-A and visible spectra means for the UV-blocking soft contact lenses. The p value for these analyses was served to establish whether a statistically significant difference exists between contact lenses. Further statistical analysis was performed a using multiple comparison (˛ = 0.05) to elicit the pairs of lenses where statistically significant differences existed for each of the wavebands tested.

2. Material and methods

Spectral transmittance of four soft contact lenses (Acuvue Moist, Pretty Eyes, Sauflon 56 UV and Zeiss CONTACT Day 30) was evaluated. All of them have UV-blocking mark on their packages. The results of ultraviolet and visible light rays transmission for each of the lenses are summarized in Table 2. Each entry on the table is the average of nine values (three lenses of each brand and three experiments with each lens). For better comparison we have provided a single transmission graph for all of the contact lenses evaluated in this study (Fig. 1). As shown in Fig. 2, Pretty Eyes shows the least transmittance of UV-B (0.65%) and Zeiss CONTACT had the highest transmittance (10.69%). Acuvue Moist and Sauflon 56 UV had UV-B transmittance of 1.22% and 5.78%, respectively. The mean UV-A transmittance data in Table 2 show that all of the examined contact lenses transmit over than 30% of UV-A, Pretty Eyes and Acuvue Moist had transmittance values of 32% and 34%, respectively. Sauflon 56 UV and Zeiss CONTACT had higher transmittance values of 48% and 43%, respectively. All of the studied contact lenses showed an overall reduction in transmittance of visible spectrum. Acuvue Moist and Zeiss CONTACT had similar visible transmittance value of 98%, while visible transmittance of Sauflon 56 UV and Pretty Eyes was 97% and 94%, respectively. The results of the one-way ANOVA statistical analysis show that a statistically significant difference exists between contact

2.1. Contact lenses The contact lenses evaluated in this study included four available soft lenses of the following types: Acuvue Moist (Johnson & Johnson, Ireland), Zeiss CONTACT Day 30 Air spheric (Zeiss, Germany), Pretty Eyes AC (Marshal Intergroup Srl, Italy) and Sauflon 56 UV (Sauflon, United Kingdom). All of the lenses were marked as UV-blocking and their optical power was −3.00 dpt. Table 1 shows the characteristics of the lenses. This study was conducted in a laboratory – Ophthalmic Lenses Verification Center (O.L.V.C.R) – of Shahid Baheshti University of Medical Sciences; that is a collaborating laboratory of National Standard Organization of Iran (ISIRI). 2.2. Instrumentation As previous studies that have measured UV absorption of spectacle and contact lenses using spectrophotometers [15,20,21], we used a special Cecil spectrophotometer (Cecil Instruments, United Kingdom) for the measurement of UV and visible transmittance spectra. A contact lens holder was designed to ensure that the soft contact lens remained saline in a stable and hydrated state throughout the measurement process. The wet-state measurement of UV

3. Results

Table 1 Contact lenses evaluated in this study. Brand

Manufacturer

UV marking

Material

Power (dpt)

BC (mm)

CT (mm)

WC (%)

Acuvue Moist Pretty Eyes AC Sauflon 56 UV Zeiss CONTACT Day 30 Air spheric

Johnson & Johnson, Ireland Marshal Intergroup Srl, Italy Sauflon, United Kingdom Zeiss, Germany

UV blocking UV blocking UV blocking UV blocking

Etafilcon A Metafilcon A Hema-copolymer Airpfilcon A

−3.00 −3.00 −3.00 −3.00

8.5 8.6 8.6 8.5

0.08 N/A 0.07 0.09

58 55 56 69

BC = base curve; WC = water content; CT = central thickness; N/A = not available.

Table 2 Ultraviolet and visible light transmission in the studied lenses. Brand

UV-B (%)

Acuvue Moist Pretty Eyes Sauflon 56 UV Zeiss CONTACT Day 30 Air Aspheric

1.22 0.65 5.78 10.69

± ± ± ±

UV-A (%) 0.24 0.20 1.87 1.08

32.88 34.47 48.18 43.09

± ± ± ±

Visible light (%) 37.73 34.88 34.76 35.10

98.77 94.64 97.72 98.04

± ± ± ±

1.25 1.68 0.79 1.27

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Fig. 1. Spectral transmittance curves of the tested contact lenses in this study.

Fig. 2. UV-B, UV-A and visible transmittances of UV-blocking tested soft contact lenses.

lenses tested for the visible (p < 0.001), UV-B (p < 0.001) and UV-A (p < 0.001) portions of the spectrum (˛ = 0.05). The results of the multiple comparisons with Tukey HSD testing for the contact lenses show that difference between the two sets of data is statistically significant at a 95% significance level (˛ = 0.05). The differences between the visible spectra are statistically significant for the Acuvue Moist contact lens compared with the Pretty Eyes and Sauflon 56 UV and Zeiss CONTACT Day 30 contact lenses (p < 0.001). The differences between the UV-B spectra are statistically significant for the Acuvue Moist contact lens compared with the Sauflon 56 UV and Zeiss CONTACT Day 30 contact lenses (p < 0.001). The differences between the UV-A spectra are statistically significant for the Acuvue Moist contact lens compared with the Sauflon 56 UV and Zeiss CONTACT Day 30 contact lenses (with p = 0.042 at most), this is true for the Pretty Eyes with Zeiss CONTACT Day 30 and Sauflon 56 UV contact lenses (with p = 0.117 at most). Other comparisons have no statistically significant differences. 4. Discussion In this study, we only evaluated UV-B, UV-A and visible spectra transmittance of some UV-blocking soft contact lenses; UV-C transmittance was ignored because the UV-C is not considered an ocular health concern [22,23]. Our results show that there are different amounts of UV and visible spectra transmitted by all tested contact lenses, although

some of them are very similar. It seems that the difference between the materials used for manufacturing the contact lenses (Table 1) is the main reason for different transmission of UV and visible spectra. In addition, other factors such as central thickness of the contact lenses (even with equal power) may have a role. The spectral transmittance curves obtained for Acuvue Moist lenses are similar to previously published studies [15,20–22,25]. Also good agreement was found with the spectral transmittance value for UV-B region published by the manufacturer too [26]. The differences in transmittance in the UV and visible spectra are probably caused by differences in the instrument used in this study. The UV-A and UV-B transmittance values found for the Acuvue Moist contact lens in our study correspond well with values found in a recent study on several branded contact lenses, before and after wearing them [27]. As they reported that the Acuvue Moist could meet the ANSI criteria, it seems the small difference between our results and their results is probably due to instrumentation and data analysis software used in the study (before wearing). Also formation of biofilms on the lens surface can be a main reason for difference after wearing the contact lenses. The spectra for the evaluated contact lenses show that Acuvue Moist and Zeiss CONTACT Day 30 have a window of transmittance in about the 313 nm and 312 nm wavelength region, respectively. While Pretty Eyes and Sauflon 56 UV contact lenses have a window of transmittance in about the 315 nm wavelength and 317 nm wavelength region, respectively (Fig. 1). All of the tested contact lenses reduced transmission of visible spectrum. The minimum visible transmission belonged to Pretty Eyes contact lenses (94.6%). About visible spectrum there is good agreement between previously published transmittance curves for soft contact lenses and results of this study [20,23]. Considering ANSI recommendation for UV-A and UV-B transmission, Acuvue Moist and Pretty Eyes contact lenses have good blocking property values for UV-B and UV-A spectra. Acuvue Moist, Sauflon 56 UV and Zeiss CONTACT Day 30 Air Aspheric have good transmission of visible spectrum. Finally, Acuvue Moist has the best UV-blocking property and visible transmission between other tested contact lenses in this study. We recommend further studies on other unexamined brands; it can be helpful for both contact lens wearers and contact lens practitioners to find which brand can provide better protection against UV harmful rays.

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