This is the author s version of a work that was submitted/accepted for publication in the following source:

Size: px

Start display at page:

Download "This is the author s version of a work that was submitted/accepted for publication in the following source:"

Phyllis Hudson
5 years ago
Views:

1 This is the author s version of a work that was submitted/accepted for publication in the following source: Osuagwu, Uchechukwu L. & Ogbuehi, Kelechi (2016) In response: UV vis light transmittance through tinted contact lenses and the effect of color on values. Contact Lens and Anterior Eye, 39(3), pp This file was downloaded from: c Copyright 2016 Elsevier Licensed under the Creative Commons Attribution; Non-Commercial; No- Derivatives 4.0 International. DOI: /j.clae Notice: Changes introduced as a result of publishing processes such as copy-editing and formatting may not be reflected in this document. For a definitive version of this work, please refer to the published source:

2 1 1 2 In Response: UV-vis light transmittance through tinted contact lenses and the effect of color on values. 3 Authors: Osuagwu Uchechukwu L (OD,MSc) 1 ; Ogbuehi Kelechi C (PhD,FAAO) Institute of Health and Biomedical Innovation, Department of Optometry & Vision Sciences, Faculty of Health, Q Block, Room 5WS36 60 Musk Avenue Kelvin Grove, Brisbane Queensland Australia. Phone: E mail: uchechukwulevi.osuagwu@hdr.qut.edu.au Department of Medicine, Dunedin School of Medicine, University of Otago, PO Box 913, Dunedin 9054, New Zealand

3 2 12 Dear Editor, Thank you for the opportunity to comment on the result of our study published in In the study, we used the Agilent 8453 spectrophotometer (which is equipped with a limiting aperture that restricts the light beam to the central 5 mm of the contact lens), to measure the transmittance of various coloured contact lenses including the one Day Acuvue define manufactured by Johnson and Johnson which the authors represent. We measured the instrument baseline before the transmittance spectra of lenses were tested. The values of lens transmittances were thus the difference between baseline and lens measurement at each time. The transmittance measurements were obtained at 0.5 nm intervals, from 200 to 700 nm after a soak in saline to remove the influence of any surface active agents within the packaging products. The technique used in our study was not very different from how other research studies 2-6 have measured the spectra transmittances of contact lenses For each contact lens brand, five new samples extracted from their blister packs were tested each time. The results in our study represent the average value of the 5 lenses for each brand and/or colour. The study was aimed at providing the transmittance behaviours of these lenses within the optical zone. We think that spectra transmittance, assessed across the optical zone of a contact lens, is the ideal manner to assess its transmission or absorption characteristics, as the variation of these characteristics should be negligible in this region As mentioned by the authors, accurate measurement of light transmission is subject to controlling many variables in the methodology particularly the centration and the ability to centre properly can be highly variable. For the purposes of verifying the standards of contact lens transmittances, and seeking registration of any brand, determining the transmittance behaviour of contact lenses through the exact centre of the lens is of great importance. Unfortunately, for this study, this level of accuracy was deemed completely unnecessary as it

4 is almost impossible to expect that the light entering a contact lens-wearing eye is only that which passes precisely through the optical centre of the contact lens The authors demonstrated that the one-day Acuvue Define transmitted more than 95% of visible light when the lens was properly centred. However, our results on the transmittance of the one day Acuvue define contact lens (figure 1, reproduced from Fig.1 of Osuagwu and Ogbuehi ) in the ultraviolet (UV) spectrum is comparable with that reported by the authors. They also confirm the difficulty associated with proper centration of the one day Acuvue lens due to its spoke pattern design. We did not try to determine the exact centre of lenses in this study prior to measurement. We recommend that future studies should consider doing so. However, we took a number of precautionary measures, which were consistent throughout the study, to ensure that the results were truly representative of the actual values. First, the instrument has a limiting aperture which restricts the light beam to the central 5mm of the contact lenses. Second, measurements were repeated twice (i.e. made in triplicate) with each lens, and the measurements demonstrated excellent repeatability (except for measurements of total UV transmittance, all other measurements showed excellent repeatabilities as is evidenced by the very small standard deviations in Table 1 (which was Table 2 of Osuagwu and Ogbuehi ). Third, five different lenses of same brand and/or colour (and of zero power) were measured to ensure the results were consistent. Fourth, the lenses were sourced from stores, randomly, to eliminate any selection bias. As just one example, the average of three measurements on each of five different one day Acuvue Define contact lenses in the visible spectrum were, 35.7, 35.0, 34.7, 34.7 and 34.8% (so for example, 35.7 is the average of 3 measurements) The instrumentation used by the authors differed from that used in our study (theirs appeared to have greater precision) and the power of the contact lenses they used for their measurements was -3.00D versus plano in our study. Although the effects of these

5 differences in methodology should be small, they would be expected to affect the comparability of both sets of results. It is also known that when the same sample is measured with two different spectrophotometers, the results often disagree by a large amount 7-9 which sometimes is greater than the precision of either instrument In conclusion, it should be noted that our result and those of previous studies are limited by the difficulty to accurately centre the contact lenses, even though, as we mentioned earlier, what really should matter is that all measurements are carried out within the optic zone of the contact lenses. This difficulty increases in cosmetic lenses where differentiation of the clear zone from the tinted zone is often difficult. Additionally, the presence of pigments along the optical path of the instrument as shown by the authors might significantly affect the results of the transmittances. 72

6 5 73 References Osuagwu UL, Ogbuehi KC. UV-vis light transmittance through tinted contact lenses and the effect of color on values. Cont Lens Anterior Eye. 2014;37: DeLoss KS, Walsh JE, Bergmanson JP. Current silicone hydrogel UVR blocking lenses and their associated protection factors. Cont Lens Anterior Eye Jun;33(3): Lira M, Dos Santos Castanheira EM, Santos L, Azeredo J, Yebra-Pimentel E, Real Oliveira ME. Changes in UV-visible transmittance of silicone-hydrogel contact lenses induced by wear. Optom Vis Sci Apr;86(4): Moore L, Ferreira JT. Ultraviolet (UV) transmittance characteristics of daily disposable and silicone hydrogel contact lenses. Cont Lens Anterior Eye Jul;29(3): Quesnel NM, Fares F, Verret E, Giasson C. Evaluation of the spectral transmittance of UV-absorbing disposable contact lenses. CLAO J Jan;27(1): Osuagwu UL, Ogbuehi KC, Almubrad TM. Changes in ultraviolet transmittance of hydrogel and silicone-hydrogel contact lenses induced by wear. Eye Contact Lens Jan;40(1): Mielenz KD. Physical parameters in high accuracy spectrophotometry In Radu Mavrodineanu, J. I. Schultz, Oscar Menis. Accuracy in Spectrophotometry and Luminescence measurements. Proceedings of a conference held NBS Goithersburg md, March Available at 8. Khashayar G, Dozic A, Kleverlaan CJ, Feilzer AJ. Data comparison between two dental spectrophotometers. Oper Dent. 2012;37:12-20.

7 Sarafianou A, Kamposiora P, Papavasiliou G, Goula H. Matching repeatability and interdevice agreement of 2 intraoral spectrophotometers. J Prosthet Dent. 2012;107: Table legend 1. Mean ± Standard deviation (SD) transmittance of total ultraviolet (UV), UVC, UVB, UVA and visible light for all tested colored contact lenses (reproduced from Osuagwu and Ogbuehi 2014) 105 Figure legend Transmittance spectra (ultraviolet (UV) vis range) for the one day Acuvue define contact lens (reproduced from Osuagwu and Ogbuehi 2014). 108

8 7 Table 1 Lens Brands Visible % UV-Visible light transmittance (mean ± Standard deviation) UV UVC UVB UVA Durasoft Green 49.9 ± ± ± ± ± 0.5 Tutti Blue 61.9 ± ± ± ± ± 2.4 Neo Cosmo Brown 64.1 ± ± ± ± ± 1.0 Acuvue Define Brown 6.7 ± ± ± ± ± 0.4 Freshlook Blue 5.1 ± ± ± ± ± 0.2 Freshlook Green 5.6 ± ± ± ± ± 0.7 ± ± 1.0 ± 6.7 ± 0.6 ± 0.6 Brown 5.9 ± ± ± ± Turquoise 6.1 ± ± ± ± ± Sapphire 5.7 ± ± ± ± ± Sterling Gray 6.1 ± ± ± ± Honey 5.2 ± ± ± ± Gemstone Green 4.2 ± ± ± ± Brilliant Blue 5.3 ± ± ± ±

This is the author s version of a work that was submitted/accepted for publication in the following source:

This is the author s version of a work that was submitted/accepted for publication in the following source: Osuagwu, Uchechukwu L., Ogbuehi, Kelechi C., & Almubrad, Turki M. (2015) In response: Changes