Intraocular and crystalline lens protection from ultraviolet damage

Calculation of solar ultraviolet influx in the eye considering the field of view and pupillary dilation due to sunglasses

The media and even the specialized literature report that the ultraviolet (UV) protection for sunglasses is critical, on the grounds that sunglasses can have a counter effect if the lenses do not provide adequate UV protection. They reason that the primary and natural mechanism is that the pupil of the eye contracts to attenuate radiation and protect the inner eye under sun exposure. Therefore, if dark lenses do not provide appropriate UV protection, there is an increased UV incidence in the inner eye due to pupil dilation, which enhances the adverse effects and impacts the ocular tissues more severely than in situations without UV protection. However, no existing literature properly quantified or supported this argument. In this work, the influx of solar UV throughout the pupil of the eye was calculated in two situations: when a person wear sunglasses and when he/she does not. In both situations, the pupil dilation and the field of view (squint) were considered with their dependence on the brightness of the ambient, calculated by modeling the solar irradiation. Finally, it was assessed whether sunglasses with poor UV protection actually increase the UV influx throughout the dilated pupil compared to the non-dilated pupil. A set of 214 sunglasses lenses were tested and the results show that pupil dilation does not play an important role in the UV influx throughout the pupil. It was observed that the FOV is the main player, surpassing the pupil size contribution by up to 314.3%, disproving the common explanation. Because of the major role of the FOV, our results show that sunglasses with UV-A protection below 86% may have a slight potential to increase hazards to the eye compared to not wearing sunglasses at all. These results can have direct impact on sunglasses standards regarding the UV protection linked to the category of the lenses.

Ultraviolet and Visible Transmittance of Soft Contact Lenses with and without Ultraviolet Blockers

SIGNIFICANCE

Ultraviolet (UV) and visible light transmittance of soft contact lenses (SCLs) was measured. A significant difference in UV transmittance has been found between SCLs with a positive and negative back vertex power (BVP). It can be shown that thicker SCLs absorb more UV radiation.

PURPOSE

This study aimed to determine UV and visible light transmittance of different SCLs with and without UV protection filters.

METHODS

Twenty-one lens brands were investigated in the BVP range of -12.00 to +6.00 D. Three SCLs were measured per BVP 25 times. Three hundred thirty-nine SCLs with UV filter (stenfilcon A, somofilcon A, narafilcon A, senofilcon A, senofilcon C, etafilcon A, nesofilcon A) and 489 SCLs without UV filter (delefilcon A, lotrafilcon A, lotrafilcon B, comfilcon A, balafilcon A, samfilcon A, asmofilcon A, nelfilcon A, omafilcon A, hilafilcon B, ocufilcon D, hioxifilcon A, omafilcon B) have been examined. The measurement setup was created according to ISO 18369-3.

RESULTS

All UV-absorbing labeled test SCLs meet UV protection class 2. senofilcon A, senofilcon C, and narafilcon A meet the higher UV protection class 1 level. A statistically significant difference in UV transmittance (280 to 380 nm) has been found between SCLs with a positive BVP (+1.00 to +6.00 D) and SCLs with a negative BVP (-1.00 to -12.00 D), both without (P = .04) and with UV filters (P = .02).

CONCLUSIONS

With the ISO-conforming, diopter-independent measurement setup, the UV-absorbing test contact lenses that meet the current international standards, regardless of their BVP, were identified. Lenses with increased center thickness absorb more UV radiation. Further studies may use a modified measurement setup with a larger aperture than 10 mm. It would also be worthwhile to examine the UV absorption of the contact lens over the complete corneal area and limbal area because UV radiation may damage inner ocular tissues like the crystalline lens as well as limbal stem cells.

Relationship between practices of eye protection against solar ultraviolet radiation and cataract in a rural area

BACKGROUND

Cataract is a public health concern worldwide that differentially affects rural residents of outlying islands where ultraviolet radiation (UVR) may have greater penetration because of less shading.

OBJECTIVES

To assess the relationships between attitudes and practices of eye protection and eye diseases for residents of an offshore island of Taiwan.

METHODS

Questionnaire survey was administered to local residents (age > 50 years) regarding socio-demographic information, attitudes/practices of eye protection under sun exposure and eye diseases.

RESULTS

A total of 816 participants (response rate 90.7%, 816/900) completed the questionnaires. Mean age was 63.7 (+ 10.8) years. Among these participants, 44.4%, 15.1% and 8.3% had cataract, dry eye and glaucoma, respectively. Although 86.3% and 88.2% of participants agreed that they should avoid outdoor activities and wear glasses/broad-brimmed hats in harsh daylight, 69.4% and 48.3% of participants never/rarely used glasses or hats/umbrellas in harsh daylight, respectively. Predictors of less practices of eye protection against solar UVR included residents who were male, with lower education level, with longer residence and lack of commercial health insurance. Multivariate logistic regression revealed that practices of eye protection under sun exposure were significantly associated with less cataract, but not glaucoma or dry eye. Participants who did not wear glasses, broad-brimmed hats/use umbrellas or both in harsh sunlight (almost) every time were respectively associated with a 57% (P = 0.028), 45% (P = 0.027) or 70% (P = 0.026) increase of cataract than those who did in harsh sunlight (almost) every time.

CONCLUSIONS

Practices of eye protection under sun exposure is associated with lower risk of cataract.

A Need to Revise Human Exposure Limits for Ultraviolet UV-C Radiation†

The COVID‐19 pandemic has greatly heightened interest in ultraviolet germicidal irradiation (UVGI) as an important intervention strategy to disinfect air in medical treatment facilities and public indoor spaces. However, a major drawback of UVGI is the challenge posed by assuring safe installation of potentially hazardous short‐wavelength (UV‐C) ultraviolet lamps. Questions have arisen regarding what appear to be unusually conservative exposure limit values in the UV‐C spectral band between 180 and 280 nm. We review the bases for the current limits and proposes some adjustments that would provide separate limits for the eye and the skin at wavelengths less than 300 nm and to increase both skin and eye limits in the UV‐C below 250 nm.

Effects of an antioxidant protective topical formulation on retinal tissue of UV-exposed rabbits

PURPOSE

The aim of this study has been to evaluate the protective effect of a topical antioxidant formulation containing riboflavin, d-α-tocopheryl polyethylene glycol (TPGS vitamin E), proline, glycine, lysine, and leucine against UV-B-induced damage in in vivo rabbit retina.

METHODS

Twenty male albino rabbits were used. Animals were divided into four groups of five animals each. Control group did not receive any UV irradiation. The first group (IG) was irradiated with a UV-A lamp for 30 min; the second (IG30) and the third (IG60) groups received UV irradiation for 30 and 60 min, respectively, and were topically treated with 1 drop (approximately 50 µl) of the antioxidant formulation, every 15 min, starting 1 h before irradiation, until the end of the UC exposure.

RESULTS

The retina of IG group showed extensive destruction of the retinal pigment epithelium (RPE) and of the cones and rods layer. The retina of G30 group showed a lesser destruction of both RPE and cones and rods layer. In the G60 group, retina showed an irregular thickening of the RPE, with massive edema of the inner and outer layer immediately adjacent together with a significant reduction of the photoreceptor number.

CONCLUSION

Our results demonstrate that a topical application of eye drops containing riboflavin, d-α-tocopheryl polyethylene glycol (TPGS vitamin E), proline, glycine, lysine, and leucine counteracts UV retinal injury in exposed retina rabbits.

Cataract frequency and subtypes involved in workers assessed for their solar radiation exposure: a systematic review

Cataract is currently the primary cause of blindness worldwide, and one of its main risk factors is solar ultraviolet radiation exposure. According to the localization of lens opacities, three main subtypes of cataract are recognized: nuclear, cortical and posterior subcapsular cataract. One of the main determinants of individual long-term solar radiation exposure is outdoor work. We systematically reviewed scientific literature from the last 20 years to update the recent development of research on the risk of cataract in outdoor workers and on the specific subtypes involved, also investigating the methods applied to evaluate the occupational risk. A total of 15 studies were included in the review, of which 12 showed a positive association. The studies confirm the relationship of long-term occupational solar radiation exposure with cortical cataract and give new support for nuclear cataract, although no substantial new data were available to support a relation with the posterior subcapsular subtype. In most of the studies, the exposure assessment was not adequate to support a representative evaluation of the ocular risk; however, outdoor work is clearly a relevant risk factor for cataract. Further research providing a better evaluation of the relation between solar radiation exposure levels and lens damage in workers is needed and aimed to establish adequate occupational exposure limits and better preventive measures, studying also their effectiveness.

Ultraviolet Keratitis: From the Pathophysiological Basis to Prevention and Clinical Management

Ultraviolet keratitis is caused by the toxic effects of acute high-dose ultraviolet radiation (UVR) reflecting the sensitivity of the ocular surface to photochemical injury. The clinical syndrome presents with ocular pain, tearing, conjunctival chemosis, blepharospasm, and deterioration of vision typically several hours after exposure, lasting up to 3 days. Mountaineers, skiers, and beach recreationalists are particularly at risk to suffer from ultraviolet (UV) keratitis as the reflectivity of UVR in these environments is extremely high. The aim of this review is to raise awareness about the potential of UV damage on the eye with an emphasis on UV keratitis, to highlight the pathophysiological basis of corneal phototoxicity, and to provide practical guidance for the prevention and clinical management of UV keratitis commonly known as snow blindness.

Solar exposure and residential geographic history in relation to exfoliation syndrome in the United States and Israel

IMPORTANCE

Residential (geographic) history and extent of solar exposure may be important risk factors for exfoliation syndrome (XFS) but, to our knowledge, detailed lifetime solar exposure has not been previously evaluated in XFS.

OBJECTIVE

To assess the relation between residential history, solar exposure, and XFS.

DESIGN, SETTING, AND PARTICIPANTS

This clinic-based case-control study was conducted in the United States and Israel. It involved XFS cases and control individuals (all ≥ 60-year-old white individuals) enrolled from 2010 to 2012 (United States: 118 cases and 106 control participants; Israel: 67 cases and 72 control participants).

MAIN OUTCOMES AND MEASURES

Weighted lifetime average latitude of residence and average number of hours per week spent outdoors as determined by validated questionnaires.

RESULTS

In multivariable analyses, each degree of weighted lifetime average residential latitude away from the equator was associated with 11% increased odds of XFS (pooled odds ratio [OR], 1.11; 95% CI, 1.05-1.17; P < .001). Furthermore, every hour per week spent outdoors during the summer, averaged over a lifetime, was associated with 4% increased odds of XFS (pooled OR, 1.04; 95% CI, 1.00-1.07; P = .03). For every 1% of average lifetime summer time between 10 am and 4 pm that sunglasses were worn, the odds of XFS decreased by 2% (OR, 0.98; 95% CI, 0.97-0.99; P < .001) in the United States but not in Israel (OR, 1.00; 95% CI, 0.99-1.01; P = .92; P for heterogeneity = .005). In the United States, after controlling for important environmental covariates, history of work over water or snow was associated with increased odds of XFS (OR, 3.86; 95% CI, 1.36-10.9); in Israel, there were too few people with such history for analysis. We did not identify an association between brimmed hat wear and XFS (P > .57).

CONCLUSIONS AND RELEVANCE

Lifetime outdoor activities may contribute to XFS. The association with work over snow or water and the lack of association with brimmed hat wear suggests that ocular exposure to light from reflective surfaces may be an important type of exposure in XFS etiology.

The consequences for human health of stratospheric ozone depletion in association with other environmental factors

Ozone depletion, climate and human health.

The enhancement of biological ocular UV radiation on beaches compared to the radiation on grass

BACKGROUND

The influence of albedo on ocular UV exposure has seldom been reported. This paper aimed to explore the enhancement effect on measured ocular UV radiation due to a sand surface compared to measured ocular UV radiation due to a grass surface.

METHODS

We measured ambient and ocular UV radiation over the beach and grass surface in Sanya City of China (18.4°N, 109.7°E). The experimental apparatus was composed of a manikin and a dual-detector spectrometer. Integration of both UVA and UVB radiation was used to denote UV radiation. Then biologically effective ocular UVB radiation (UVBE) and the ratios of UVBE of two surfaces were calculated.

RESULT

Maximum of ocular UV radiation versus time over the two surfaces is bimodal. UVBE on the beach is significantly larger than UVBE on the sand, and UVBE peaked at different solar elevation angle (SEA) over the two surfaces (about 53° and 40° on the beach and grass, respectively, according to Bayesian regression). The maximum of ocular UVBE ratios is greater than two, which peaked SEA was about 50°. One hour's cumulative radiation under sunny weather exceeds thresholds for photokeratitis, conjunctivitis and lens damage.

CONCLUSIONS

Higher albedo significantly increased biological ocular UV radiation. Tourists on tropical beaches should take protective measures and avoid facing the sun directly, especially when SEA is around 50°.

Oxidative photodegradation of ocular tissues: beneficial effects of filtering and exogenous antioxidants

The fact that light is necessary for life is generally accepted as an axiom. The extent to which light interacts and influences human biology, however, is often not fully appreciated. Exposure to sunlight, for instance, can both promote and degrade human health. There is now general scientific consensus that, although the eye evolved to respond to light, it is also damaged by excessive exposure. Light-mediated ocular damage is involved in the pathophysiology of many common forms of blindness. The type of ocular tissue damage induced by light exposure depends on the extent of exposure and wavelength. The tissues of the lens, cornea, and retina contain specific chemical moieties that have been proven to exhibit light-mediated oxidative degradation. Proteins and lipids present in the cornea, lens, and retina, meet all of the physical requirements known to initiate the process of oxidative photodegradation upon exposure to solar radiation. As such, different mechanisms have evolved in the lens, cornea, and retina to ameliorate such light-mediated oxidative damage. It appears, however, that such mechanisms are ill-matched to handle modern conditions: namely, poor diet and longer life-spans (and the degenerative diseases that accompany them). Hence, steps must be taken to protect the eye from the damaging effects of light. Preventative measures include minimizing actinic light exposure, providing exogenous filtering (e.g., through the use of protective lenses), and enhancing antioxidant defenses (e.g., through increased dietary intake of antioxidants). These strategies may yield long-term benefits in terms of reducing oxidative photodegradation of the ocular tissues.

Self-service kiosk for testing sunglasses

BACKGROUND

Sunglasses users may only be assured on their ultraviolet protection by purchasing certified products, however they are not able to check if sunglasses are still ultraviolet (UV) protected as they age, unless they resort themselves to a professional who is qualified for using a spectrophotometer and is acknowledged on the standards for providing a report for the user. Current literature establishes safe limits on the exposure of the eyes relatively to the ultraviolet radiation exposure for the UVA and UVB ranges (280 nm - 400 nm). The UV protection is category dependent. Sunglasses are categorized from 0 to 4 and the categories are determined by the lenses transmission's percentage on the visible range (380 nm - 780 nm).

METHODS

In order to overcome inaccessibility of such measurements on sunglasses, a prototype for testing ultraviolet protection on sunglasses, according to Brazilian Standards, has been developed for amateur use. The system consists of assembling UVA and UVB light sources and two UV responsive photodiode sensors, with Erythema action response for measuring UV protection; for categories measurements, combination of white light and LEDs were used for the visible range, as well as a light sensor having spectral response similar to the human eye. Electronics has been developed for controlling the measurements and software has been implemented for providing the report as well as for the user's interface.

RESULTS

All the system was embedded as a self-service touch screen kiosk and provides transmittance measurements that are within the deviation limit required by NBR15111, i.e., 0.25%. Measurements were performed in over 45 sunglasses and compared to CARY 5000 - VARIAN spectrophotometer and present a good correlation for the measurements of transmittance in the visible spectral range (r2 = 0.9999) and in the ultraviolet range (r2 = 0.9997).

CONCLUSIONS

The prototype identifies the UV protection, for non-corrective sunglasses, according to category of the lens and is available for the public. In addition to educating the population about the importance of wearing protected sunglasses, the prototype has also allowed the public to have access to information about the quality of protection of their own sunglasses in an easy and free testing method.

UV-B-induced DNA damage and repair in the mouse lens

PURPOSE

Epidemiologic studies have linked UV-B exposure to development of cortical cataracts, but the underlying molecular mechanism(s) is unresolved. Here, we used a mouse model to examine the nature and distribution of DNA photolesions produced by ocular UV-B irradiation.

METHODS

Anesthetized mice, eye globes, or isolated lenses were exposed to UV-B. Antibodies specific for 6-4 photoproducts (6-4 PPs) or cyclobutane pyrimidine dimers (CPDs) were used to visualize DNA adducts.

RESULTS

Illumination of intact globes with UV-B-induced 6-4 PP and CPD formation in cells of the cornea, anterior iris, and central lens epithelium. Photolesions were not detected in retina or lens cells situated in the shadow of the iris. Photolesions in lens epithelial cells were produced with radiant exposures significantly below the minimal erythemal dose. Lens epithelial cells rapidly repaired 6-4 PPs, but CPD levels did not markedly diminish, even over extended postirradiation recovery periods in vitro or in vivo. The repair of 6-4 PPs did not depend on the proliferative activity of the epithelial cells, since the repair rate in the mitotically-active germinative zone (GZ) was indistinguishable from that of quiescent cells in the central epithelium.

CONCLUSIONS

Even relatively modest exposures to UV-B produced 6-4 PP and CPD photolesions in lens epithelial cells. Cyclobutane pyrimidine dimer lesions were particularly prevalent and were repaired slowly if at all. Studies on sun-exposed skin have established a causal connection between photolesions and so-called UV-signature mutations. If similar mechanisms apply in the lens, it suggests that somatic mutations in lens epithelial cells may contribute to the development of cortical cataracts.