Ultraviolet protection in spectacle and sunglass lenses: claims vs performance

The need for ultraviolet protection in the natural environment has become a popular topic in the media, particularly when considered in conjunction with the depleting ozone layer and ozone hole(s). Public apprehension has been fuelled by sunglass manufacturers, distributors and importers in their attempts to sell more of their product. This has led, among other things, to the marking of sunglasses with claims of 95 per cent or 100 per cent UV protection. It has also led to a proposal for marking sunglasses with a code of Environmental Protection Factor (EPF) akin to the Sun Protection Factors of sunscreens. In this method the equivalent of a sun protection factor of 400+ is given the maximum rating of 10. In a previous report from this study, we surveyed available sunglass data to assess the level of UVR protection afforded and compliance with the sunglass standards in 253 sunglasses. We men surveyed the additional ultraviolet claims on 81 pairs of commercially available sunglasses sampled by the Federal Bureau of Consumer Affairs. We found that the great majority of sunglasses passed the various standards and the majority would have rated 10 on the EPF scale. However, a number of sunglasses did not meet the claims of UV protection placed on them by the suppliers. The suppliers are, therefore, tending to fall short in their self-applied claims rather than the requirements of sunglass standards. We also dyed a set of piano untinted lenses using commercially available dyes and purchased lenses claimed to be treated to include 100 per cent protection to 400 nm. Judging by the performance of the lenses, there was some considerable variation in the interpretation placed on the term ‘UV 400’. The dyes fell well short, although extending the dyeing time can produce lenses with low transmittance at 400 nm. Some of the variation in claims may well arise from variations between national standards and the definition of ultraviolet wavelength limits. We hope that work can recommence on the ISO standard to enable the rationalisation of the standards and claims. (Clin Exp Optom 1993; 76.4: 136–140)     

Children's sunglasses: caveat emptor

Spectrophotometric measurements were obtained on 40 pairs of children's sunglasses. Some of these sunglasses provide excellent protection from the potentially damaging effects of ultraviolet radiation (UVR), whereas others fail to provide adequate protection for the crystalline lens and retina. Some labels were ambiguous and misleading with respect to whether the sunglass provided adequate absorption of UVR.     

Sunglasses and sunglass standards

Sunglasses and sunglass standards are reviewed from the point of view of the history of sunglasses and the development of sunglass standards. The need for eye protection from solar radiation is discussed and the provisions of the various national sunglass standards are discussed in relation to that need.     

Sunglasses,the European directive and the European standard

Purpose: The Optics and Radiometry Laboratory (ORLAB) provides a testing service for the Australian sunglass industry to assist its compliance with the mandatory Consumer Product Safety Standard. In doing so, a number of sunglasses carrying the CE mark (in effect a claim of compliance with the European Union Personal Protective Equipment Directive) have been tested. Since there is no mandatory testing in Europe (the sunglass industry is deemed self regulating), evaluating their performance will give an insight into compliance with the Directive. Methods: Consecutive submissions to ORLAB over a period of 18 months were examined for CE marked sunglasses. The results for 646 CE marked pairs of sunglasses tested during 2003 and first half 2004 were examined and evaluated for compliance with EN 1836 (the European sunglass standard) on the basis of refractive power, prismatic power, transmittance (visible, UV and coloration) and polarization. Results: A total of 17.3% failed EN 1836 and 3.3% were borderline (i.e. within our uncertainties of measurement of the requirement). The failures comprised: 0.9% lens defect; 12.5% polarization alignment error; 2.7% excessive vertical prism; 22.3% excessive horizontal prism; 27.7% excessive spherical power; 14.3% excessive cylindrical power; 1.8% excessive UV transmittance; and 23.2% transmittance difference between lenses (always gradient tints). Conclusion: With up to 20% non‐compliance, self regulation is not working particularly well in providing the public with complying sunglasses.     

UV-A absorbing characteristics of commercial sunglasses intended for recreational and general use.

Ultraviolet radiation (UVR) is known to cause photokeratitis with acute symptoms. It also has been demonstrated that UVR has the potential to accelerate human cataractogenesis. For certain recreational pursuits, protection from specific UVR wavebands is important to the prescriber, the dispenser, and the patient or consumer of sunglasses. By knowing the ultraviolet absorbance characteristics of lens materials, practitioners would be able to advise their patients. In this study, the UV-A spectra of pairs of sunglasses purchased anonymously were measured. The results indicate that manufacturers' claims of UVR protection, or absorbance, are valid with respect to the UV-A waveband. No association between UV-A absorbance and lens material or cost was established.     

Prevention of the adverse photic effects of peripheral light-focusing using UV-blocking contact lenses

PURPOSE: Peripheral light-focusing (PLF) is an occult form of ultraviolet radiation (UVR) hazardous to the human eye. In PLF, obliquely incident light is refracted from the peripheral cornea to concentrated sites inside the anterior segment. In the current study, the directionality of this phenomenon for UVR and whether PLF is established in outdoor settings exposed to sunlight were investigated. The protection provided by a UV-blocking contact lens was also evaluated. METHODS: UVA and UVB sensors were placed on the nasal limbus of an anatomically based model eye. The temporal limbus was exposed to a UV light source placed at various angles behind the frontal plane. PLF was quantified with the sensor output. The ensemble was mounted in the orbit of a mannequin head and exposed to sunlight in three insolation environments within the region of Sydney, Australia. PLF for UVA and UVB was determined with no eyewear or with sunglasses and commercially available soft contact lenses, with and without UV-blocking capability. RESULTS: The intensity of UVA peaked at approximately 120 degrees incidence, the level at which the UVB response was also at its maximum. The intensification of UVA was up to x18.3. The intensity of PLF for UVA and UVB was reduced by an order of magnitude by a UV-blocking contact lens, whereas a clear contact lenses had a much lesser effect. Only the UV-blocking contact lens achieved a significant effect on UVA and UVB irradiance in the urban, beach, and mountain locales (P < 0.056). CONCLUSIONS: The results identify another type of sunlight hazard: the peripheral focusing of obliquely incident light. UVR from albedo (reflected ambient light) is capable of establishing PLF in the anterior segment, but this can be shielded by UV-blocking soft contact lenses. Sunglasses may be unable to shield oblique rays, unless side protection is incorporated. Contact lenses can offer UVR protection against all angles of incidence, including the peak-response angle. They can also protect the eye in settings in which the wearing of sunglasses is not feasible or convenient.     

The Sunglass Standard and its rationale

This paper reports on the 17-year development of the current Z80.3 Sunglass Standard. The dioptric tolerances of +0.125 to -0.25 D power, 0.125 D astigmatism, 0.25 delta prism, and 0.18 D power imbalance are based on research by optometry's leaders. The traffic signal and luminous transmittance requirements are the result of study of the literature and original research. There has been much misunderstanding regarding the UV transmittance specifications. They too were exhaustively researched and discussed. That work is reviewed in detail. New equations for calculating exposures are presented with sample spectra. Graphic evaluations of severe risk exposures are presented. They show that based on the accepted criteria, for reasonable assumptions the Standard offers a 10x margin of safety. Studies of retinal risk indicate the Standard provides ample protection. Some criteria need further study. Potential problems are based on the fact that some sunglasses are too dark for driving and that use of ordinary sunglasses for sports provides inadequate protection from injuries.     

Ultraviolet radiation transmittance of the mouse eye and its individual media components

Recently, the mouse has become the preferred animal model in ophthalmic research. Therefore, there is a need for enhanced understanding of the mouse eye to validate its use in different experimental setting. The purpose of this study was to determine the ocular transmittance of the whole mouse eye, the cornea and the crystalline lens, particularly in the ultraviolet radiation (UVR) wavebands. This was carried out using a non-cuvette based fiber optic spectrometer system and the resulting transmittance curves were compared with published cone spectral response curves and mouse ocular transmittance data. First, transmittance curves of the whole mouse eye were measured by removing a small disc of sclera from the posterior pole to provide an anterior to posterior optical path. No statistical difference was found between left and right eye in each of the four mice sampled, therefore, all eight eyes were included in the final statistical analysis. The average of five test measurements from each left and right eye for the four test mice showed a transmittance cut off at approximately 310 nm. Secondly, the cornea with a scleral rim was excised and transmittance curves obtained for all eight eyes. This data showed an average transmittance cut off at 280 nm for the cornea. Similarly measured data for the excised crystalline lens showed UVR transmittance down to 310 nm. The good correlation between total ocular UVR transmittance and the sum of the individually measured components (i.e. the cornea and the crystalline lens) supported the validity of our method and its findings. This experiment demonstrated that the mouse cornea transmits more UV-B (280-315 nm) than the rabbit and the human corneal transmittance. The mouse crystalline lens on the other hand showed a cut off in the UV-B at 310 nm, which is at a much lower UV-B wavelength than the approximate UV-A (315-400 nm) cut off for the human crystalline lens at around 390 nm. The increased transmittance of UVR in the mouse eye serves its vision, since the mouse has a cone photopigment peaking at approximately 350 nm. Due to the above stated differences between the mouse and the human it is concluded that the mouse is not an ideal model for the human eye in experiments involving UVR.     

A SURVEY OF OPTICAL PROPERTIES OF SUNGLASSES

The results of a survey of optical properties and dimensions of a sample of 135 different sunglass lenses commercially available in Australia are compared with the limits for optical properties and dimensions of sunglasses given by an existing specification for general purpose sunglasses.     

Evaluation of the spectral transmittance of UV-absorbing disposable contact lenses.

PURPOSE: Increasing evidence suggesting deleterious effects of ultraviolet radiation (UVR) on the eye has prompted manufacturers to develop UV-absorbing disposable contact lenses. The spectral transmittances of a sample of these lenses were measured in order to determine if they provide adequate protection from UVR. METHODS: Four types of UV-absorbing disposable lenses were studied (Acuvue [Vistakon, Jacksonville, FL], Precision UV [Wesley-Jessen, Des Plaines, IL], Specialty Sport [Specialty UltraVision, Sunnyvale, CA], and Surevue [Vistakon]). For comparison, a lens without UV-absorbing properties (Acuvue), a conventional soft lens (Permaflex UV [Cooper Vision, San Jose, CA]) and an RGP lens (Boston ES [Polymer Technology, Rochester, NY]) were also evaluated. The tested lens was placed in a silica wet cell filled with saline. Spectral transmittance was measured over the 200-800 nm waveband. RESULTS: Each disposable lens exhibited a transmittance window in the 240-320 nm waveband. Computing indices of protection factor and safe exposure duration allowed for the assessment of the level of protection afforded by each lens. Among disposable lenses studied, the Surevue performed best with a transmittance of less than 1% in the waveband 280-348 nm and the longest safe exposure duration, while the Specialty Sport had the highesttransmittance of UVB (290-315 nm). CONCLUSION: All UV-absorbing lenses studied provided a better level of protection from UVR exposure than lenses without UV absorber. These results will help the eyecare practitioner in prescribing the most appropriate UV-blocking lens for each patient.     

Short wavelengths filtering properties of sunglasses on the Canadian market: are we protected?

Background

Exposure to solar radiation is a risk factor for multiple ocular pathologies. Ultraviolet (UV) radiation is involved in ocular diseases, including pterygium, ocular surface squamous neoplasia, and cataracts. High-energy visible light (HEV) is associated with age-related macular degeneration. Ocular protection against solar radiation seems essential to protect our eyes against the adverse effects of those harmful rays. Australia, New Zealand, Europe, and the United States are the only regions with mandatory standards for UV transmission for sunglasses. Adherence to Canadian standards by sunglasses manufacturers is not mandatory. In this study, we evaluated the UV and visible transmission of sunglasses in the Canadian market to test their compliance with Canadian standards.

窄谱滤光片屏蔽460～480nm蓝光后正常成人视功能的变化

目的 观察屏蔽460～480 nm蓝光后正常成年人视功能的变化.方法 自身对照研究.选取24例正常成年人,分别比较其在正常未干预情况下、配戴屏蔽460～480 nm蓝光滤光片(窄谱滤光片)后和配戴普通市售黄色镜片(屏蔽部分380～550 nm可见光)后,在2种照度环境中(1 000 lx、40 lx)色觉的错误总分值(TES)和10个分色区错误分值(PES),并比较明环境、暗环境、暗眩光环境中5个空间频率(1.5、3.0、6.0、12.0、18.0 c/d)对比敏感度的变化,采用配对秩和检验对各组数值进行统计学分析.结果 2种照度环境下,配戴窄谱滤光片或黄色镜片后FM100-Hue色棋检查的TES和多个分区PES均高于未干预状态(P＜0.017).配戴窄谱滤光片状态和配戴黄色镜片状态相比,在2种照度环境下,黄色镜片状态TES和多个分区PES均高于窄谱滤光片状态(P＜0.017).明环境和暗环境中,3种状态下在5个空间频率对比敏感度的差异无统计学意义,暗眩光环境中,配戴窄谱滤光片状态在6.0 c/d空间频率对比敏感度值高于未干预状态(P＜0.017).结论 通过光学薄膜技术将460～.480 nm波长光特异性屏蔽后,正常成年人的色觉辨别力有一定程度的下降,但和普通黄色镜片相比影响程度较轻.特异性屏蔽460～480 nm蓝光后,成年人在中频的对比敏感度显著提高,这种改善作用优于普通黄色镜片.     

Sunglasses: are they necessary in Christchurch?

Concern over potential eye injury from sunlight prompted this study to see if the levels of sunlight in Christchurch posed a particular risk to our population's eyes, whether the populace was aware of any risk and whether effective sunglasses were freely available to the public. While there has been a 4% to 9% increase in UV radiation since 1969 due to global ozone depletion, no firm evidence was found that focal ozone depletion was a particular problem in New Zealand. Christchurch residents were poorly informed about the ocular hazards of sunlight. A questionnaire completed by 200 adults disclosed 32% were unaware of the particular danger of UV light and only 3% knew that snow blindness, eclipse burns and cataracts could all be caused by sunlight. Fifty-four sunglasses were analysed for labelling and for transmission characteristics of their lenses. The standard of labelling of the sunglasses was poor with only 53% making reference to UV transmission characteristics and only three pairs stating that they adhered to the New Zealand Sunglass Standard. Attention is drawn to the need to improve public awareness of the potential for eye injury from sunlight and to improve the standard of labelling of sunglasses.     

Ultraviolet-absorbing spectacle lenses, contact lenses, and intraocular lenses

Optical materials that are available to the practitioner for protection of the eye against hazardous exposure to ultraviolet radiation (UVR) are discussed. Principles of protection, procedures for calculating safe ocular exposure duration, and transmittance curves of commonly prescribed spectacle lenses, contact lenses, and intraocular lenses are discussed. Suggestions are made to assist the practitioner in providing adequate protection for the patient.     

Sunglasses: are they necessary in Christchurch?

Concern over potential eye injury from sunlight prompted this study to see if the levels of sunlight in Christchurch posed a particular risk to our population's eyes, whether the populace was aware of any risk and whether effective sunglasses were freely available to the public. While there has been a 4% to 9% increase in UV radiation since 1969 due to global ozone depletion, no firm evidence was found that focal ozone depletion was a particular problem in New Zealand. Christchurch residents were poorly informed about the ocular hazards of sunlight. A questionnaire completed by 200 adults disclosed 32% were unaware of the particular danger of UV light and only 3% knew that snow blindness, eclipse burns and cataracts could all be caused by sunlight. Fifty-four sunglasses were analysed for labelling and for transmission characteristics of their lenses. The standard of labelling of the sunglasses was poor with only 53% making reference to UV transmission characteristics and only three pairs stating that they adhered to the New Zealand Sunglass Standard. Attention is drawn to the need to improve public awareness of the potential for eye injury from sunlight and to improve the standard of labelling of sunglasses.     

Effectiveness of eyeglasses for protection against ultraviolet rays]

PURPOSE: The relationship between eyeglass size and protection of the eye surface from the effects of solar ultraviolet (UV) rays was investigated. METHODS: Solar UV rays irradiating the eye surface were measured on a mannequin which modeled the standard facial bone structure of a Japanese female. UV sensor chips (photo-sensitivity: 260-400 nm) were attached to the ocular surface of the lid fissure. UV measurement was done from 12:00 to 15:00 on a sunny day in March. UV intensity was measured under the following conditions: 1) with or without eyeglasses, 2) wearing sunglasses with side protectors, and 3) wearing a cap with a 7 cm brim. Eyeglasses of four frame sizes (width: 48-57 mm) were put on the mannequin. All lenses were made of plastic and coated so as to be impervious to rays shorter than 400 nm. The refractive power was 0 diopters. At the same time, UV irradiation intensity from all directions (excluding from the earth direction) was measured using a polyhedron type UV sensor with 25 sensor chips. RESULTS: Except for eyeglasses with the smallest frame size, eyeglasses effectively reduced UV exposure to sunlight from the upper front direction. However, protection against rays from the upper temporal direction was extremely poor. Sunlight from the upper back was reflected by the posterior surface of the eyeglasses and reached the eye surface. CONCLUSION: The efficacy of eyeglasses against UV depends on their size. The shape of the eyeglasses and reflection from the posterior lens surface are also of great importance. Small eyeglasses do not offer ideal UV protection for the Japanese face shape.     

Quantification of the ultraviolet radiation (UVR) field in the human eye in vivo using novel instrumentation and the potential benefits of UVR blocking hydrogel contact lens

BACKGROUND/AIMS: Certain degenerative eye conditions occur predominantly nasally, at the limbal region, and are associated with solar ultraviolet radiation (UVR) induced damage. The relative contribution to the in vivo ocular flux of (a) the reflection of UVR incident on the skin of the nose onto the nasal limbus, and (b) the focusing of UVR incident on the temporal side of the cornea onto the nasal limbus were examined. METHODS: A novel photodiode sensor array was used to measure the UVR field across the eye. In addition, a novel spectrometer set-up was used to measure the spectrum of radiation refracted across the cornea. The efficacy of UVR blocking hydrogel contact lenses in filtering incident UVR was assessed in vivo. RESULTS: Qualitative and quantitative data indicated an increase nasally of UVR. Photodiode readings showed a net UVR increase from the temporal to the nasal side. Transmission curves showed that most UVR incident on the limbal region is either absorbed by, or transmitted through, the ocular tissues. This radiation is filtered by UVR blocking soft contact lens. CONCLUSIONS: An increased UVR flux on the nasal side of the eye, due to reflection off the nasal skin, was identified in vivo. Any UVR passing through the cornea is either absorbed by the conjunctiva and/or transmitted through it onto the sclera where it is absorbed. UVR blocking hydrogel contact lenses can eliminate these sources of UVR.     

Ultraviolet radiation as a risk factor for cataract and macular degeneration

The human eye is constantly exposed to sunlight and artificial lighting. Light transmission through the eye is fundamental to its unique biological functions of directing vision and circadian rhythm, and therefore, light absorbed by the eye must be benign. However, exposure to the intense ambient radiation can pose a hazard particularly if the recipient is over 40 years of age. This radiation exposure can lead to impaired vision and transient or permanent blindness.Both ultraviolet-A (UV-A) and UV-B induce cataract formation and are not necessary for sight. Ultraviolet radiation is also a risk factor for damage to the retinas of children. The removal of these wavelengths from ocular exposure will greatly reduce the risk of early cataract and retinal damage. One way this may be easily done is by wearing sunglasses that block wavelengths below 400 nm (marked 400 on the glasses). However, because of the geometry of the eye, these glasses must be wraparound sunglasses to prevent reflective UV radiation from reaching the eye. Additional protection may be offered by contact lenses that absorb significant amounts of UV radiation.In addition to UV radiation, short blue visible light (400-440 nm) is a risk factor for the adult human retina. This wavelength of light is not essential for sight and not necessary for a circadian rhythm response. For those over 50 years old, it would be of value to remove these wavelengths of light with specially designed sunglasses or contact lenses to reduce the risk of age-related macular degeneration.