An abbreviated assessment of ocular exposure to ultraviolet radiation.

Individual behaviour has a very large effect on determining the exposure of the eye to solar radiation. To be able to examine the relationship between ocular exposure to ambient ultraviolet radiation and ocular disease, a model was developed previously that assessed cumulative ocular exposure from individual information on work and leisure activities. In this paper, we present a simplified version of the model that uses data on exposure during the middle of the day (9 a.m. to 3 p.m. solar time) during the northern 'summer' months (April to September). The ocular exposure determined by the simplified model is highly correlated with the full model (r = 0.98) and the simplified model predicts 62% of the total ocular exposure. This model should be useful for future epidemiologic studies of sun exposure and eye disease.     

Basal cell carcinoma of the eyelids and solar ultraviolet radiation exposure

AIMS—To compare the distribution of eyelid basal cell carcinoma (BCC) with the relative ultraviolet radiation (UVR) exposure to different sites on the eyelids.
METHODS—The location of BCC on the eyelids was allocated to one of seven regions. The UVR exposure was recorded with a polymer film attached to the eyelids at seven sites in a manikin and in human subjects.
RESULTS—Localisation of the 329 tumours was mainly on the lower eyelids (225 tumours), and the medial canthal regions (87 tumours). There was no association between UVR doses at the seven sites of the eyelids and the location of BCCs. The UVR exposure was similar on the upper and lower eyelids, while the number of tumours on the lower eyelids outnumbered the upper lids by a factor of 13 (17 upper, 225 lower)
CONCLUSION—UVR exposure only partially explains the aetiology of periorbital BCC.

Keywords: polysulphone film; basal cell carcinoma; ultraviolet radiation; eyelid     

Methodological considerations for future epidemiological studies of solar ultraviolet radiation and eye disease

This paper reviews current methodological and epidemiological issues that face researchers interested in examining the relationship between exposure to solar ultraviolet radiation and cataract and other eye diseases. Key areas addressed include study design, measurement of ocular exposure, potential confounding and modifying factors, and evaluation of the impact of ozone depletion on eye diseases.     

紫外线误照致群体性眼外伤的调查

目的 总结紫外线致群体性眼外伤的卫生学调查的方法和结果，探讨治疗及预防方法。方法 首先排查出致伤现场，进行卫生学调查，模拟检测眼部接受紫外线的强度并与国家标准对比。对患者进行镇痛、促使角膜上皮修复及预防感染的治疗。结果 测出了患者在1小时内接受紫外线的强度为：中波3．8～11．2μW／cm^2，短波3．9～11μW／cm^2，为国家标准全天接触最高限值的3～10倍。25位患者在治疗后1～2天内均痊愈。结论 加强职业卫生健康教育及培训，完备预防措施是预防紫外线性眼外伤的重点。发病后及时正确的治疗极为重要。     

The association between pterygium and conjunctival ultraviolet autofluorescence: The Norfolk Island Eye Study

Purpose: To investigate the association between conjunctival ultraviolet autofluorescence (UVAF), a biomarker of ocular ultraviolet radiation (UVR) exposure, and prevalent pterygium. Methods: We conducted a cross‐sectional study on Norfolk Island, South Pacific. All permanent residents aged ≥15 were invited to participate. Participants completed a sun exposure questionnaire and underwent autorefraction and slit lamp biomicroscope examination. Area of conjunctival UVAF (sum of temporal/nasal area in right and left eyes) was determined using computerized methods. Multivariate logistic and linear regression models were used to estimate the associations with pterygia and UVAF, respectively. Results: Of 641 participants, 70 people (10.9%) had pterygium in one or both eyes, and prevalence was higher in males (15.0% versus 7.7%, p = 0.003). Significant independent associations with pterygium in any eye were UVAF (per 10 mm²) [odds ratio (OR) 1.16, 95% confidence interval (CI) 1.16–1.28, p = 0.002], tanning skin phenotype (OR 2.17, 1.20–3.92, p = 0.010) and spending more than three‐quarters of the day outside (OR 2.22, 1.20–4.09, p = 0.011). Increasing quartile of UVAF was associated with increased risk of pterygium following adjustment of age, sex and time outdoors (p_Trend = 0.002). Independent associations with increasing UVAF (per 10 mm²) were decreasing age, time outdoors, skin type and male gender (all p < 0.001). UVAF area correlated well with the duration of outdoor activity (p_Trend < 0.001). Conclusion: Pterygium occurs in approximately one‐tenth of Norfolk Islanders. Increasing conjunctival UVAF is associated with prevalent pterygia, confirming earlier epidemiological, laboratory and ray‐tracing studies that pterygia are associated with UVR. Protection from the sun should be encouraged to reduce the prevalence of pterygium in the community.     

Contact lens dosimetry of solar ultraviolet radiation

Background : Ultraviolet radiation from the sun has been implicated in the pathogenesis of many ocular conditions. However, the amount of UV reaching the eye is not well defined. Methods : A contact lens made from the UV-sensitive plastic polysulphone was used to measure the dose of UV radiation at the surface of the eye for two subjects over six wearing trials. Results : The average ratio of UV radiation exposure at the surface of the eye to that of the UV radiation in the surrounding environment (ambient dose) was found to be 28 ± 9 per cent. The temporal UV dose appeared lower than both the central and nasal UV doses in five of the six wearing trials but these differences did not reach statistical significance. Conclusions : Contact lenses made from polysulphone can be used to estimate the regional dose of solar ultraviolet radiation. (Clin Exp Optom 1997; 80: 6: 204–210)     

Maximum tolerable dose for avoidance of cataract after repeated exposure to ultraviolet radiation in rats

The purpose of the present study was to determine the impact of inter-exposure interval between repeated equivalent exposures of ultraviolet radiation (UVR) on threshold accumulated dose for cataract development. Female Sprague-Dawley rats were randomly divided into 5 inter-exposure interval groups with 20 rats in each group. The inter-exposure intervals were 6 h, 1, 3, 9 and 30 days respectively. Each inter-exposure interval group was divided into 5 dose-subgroups. Only one eye of each rat was exposed to ultraviolet radiation (lambdamax=300 nm). The total dose incident on the cornea, in each subgroup varied between 0 approximately 10 kJ/m2. One week after the second exposure, the rats were sacrificed and both lenses were extracted. The intensity of forward light scattering was measured and macroscopic morphology was documented. Maximum tolerable dose (MTD) for each inter-exposure interval was estimated based on the experimentally determined dose-response function. The difference of intensity of light scattering between exposed and contralateral non-exposed lens decreased as a function of inter-exposure interval between the two equivalent exposures. The accumulated MTD2.3:16 was 5.3, 5.1, 5.4, 5.8, and 6.0 kJ/m2 UVR-B for the 6 h, 1, 3, 9 and 30 day inter-exposure interval between the two exposures, respectively. The shorter the inter-exposure interval between two subsequent exposures, the more damage. The time constant for repair of lens damage after in vivo exposure to close to threshold dose was estimated to be eight days and the fraction of repairable damage to be 20%. The accumulated threshold dose for damage after two repeated equivalent exposures to UVR-B increases as a function of inter-exposure interval up to at least 30 days inter-exposure interval.     

Distribution of conjunctival ultraviolet autofluorescence in a population-based study: the Norfolk Island Eye Study

Objective

The objective of this study was to describe the distribution of conjunctival ultraviolet autofluorescence (UVAF) in an adult population.

Methods

We conducted a cross-sectional, population-based study in the genetic isolate of Norfolk Island, South Pacific Ocean. In all, 641 people, aged 15 to 89 years, were recruited. UVAF and standard (control) photographs were taken of the nasal and temporal interpalpebral regions bilaterally. Differences between the groups for non-normally distributed continuous variables were assessed using the Wilcoxon–Mann–Whitney ranksum test. Trends across categories were assessed using Cuzick''s non-parametric test for trend or Kendall''s rank correlation τ.

Results

Conjunctival UVAF is a non-parametric trait with a positively skewed distribution. Median amount of conjunctival UVAF per person (sum of four measurements; right nasal/temporal and left nasal/temporal) was 28.2 mm² (interquartile range 14.5–48.2). There was an inverse, linear relationship between UVAF and advancing age (P<0.001). Males had a higher sum of UVAF compared with females (34.4 mm² vs23.2 mm², P<0.0001). There were no statistically significant differences in area of UVAF between right and left eyes or between nasal and temporal regions.

Conclusion

We have provided the first quantifiable estimates of conjunctival UVAF in an adult population. Further data are required to provide information about the natural history of UVAF and to characterise other potential disease associations with UVAF. UVR protective strategies should be emphasised at an early age to prevent the long-term adverse effects on health associated with excess UVR.     

Assessment of the epidemiological evidence that exposure to solar ultraviolet radiation causes cataract

In this paper an assessment is made of the evidence that exposure to solar ultraviolet radiation is causally associated with cataract. The evidence is reviewed separately for cortical, nuclear and posterior subcapsular cataract. The assessment examines the consistency and magnitude of an association, the dose-response relationship, supporting ecological data, and data from animal studies. Based on the assessment, it is concluded that there is sufficient experimental evidence that exposure to artificial sources of UV-B can cause cortical opacities in laboratory animals. However, there is only limited evidence that exposure to solar UV-B causes cortical opacities in humans. Similarly, there is only limited evidence that exposure to solar UV-B causes posterior subcapsular cataract in humans. The epidemiological evidence is consistent in suggesting tha nuclear cataracts are not causally associated with exposure to solar UV-B.     

Evolution of light scattering and redox balance in the rat lens after in vivo exposure to close‐to‐threshold dose ultraviolet radiation

Acta Ophthalmol. 2010: 88: 779–785

Abstract.

Purpose: To investigate the evolution of cataract development and glutathione redox balance in the rat lens after in vivo close‐to‐threshold dose exposure to ultraviolet radiation (UVR) around 300 nm. Methods: Three groups of 10 Sprague–Dawley rats were unilaterally exposed to 8 kJ/m² UVR‐300 nm for 15 min, and a fourth group of 10 rats was kept without UVR exposure as nonexposed control animals. The exposed animals were killed at 1, 3 and 7 days after exposure. Both lenses from all animals were extracted and photographed and the intensity of forward light scattering was measured quantitatively. Thereafter, the lenses were homogenized. The concentration of reduced glutathione (GSH) and oxidized glutathione (GSSG), and the activity of glutathione reductase (GR) and glutathione peroxidase (GPx), respectively, were determined spectrophotometrically. The mean paired differences between exposed and nonexposed lenses were used as primary data in the statistical analyses. Results: All exposed lenses developed cataract. Lens light scattering increased throughout the 7 days after UVR exposure. GSH concentration and GPx rate transiently increased at 1 day after exposure and then decreased throughout follow‐up, with GSH concentration having a negative balance at the end. GSSG concentration and GR activity did not change after UVR exposure. Conclusion: In vivo close‐to‐threshold UVR exposure induces a gradual increase in rat lens opacification/cataract development and time dependently alters the redox balance in the lens.     

高原紫外线致晶状体损伤的防护效果评估

目的:检验评估高原紫外线致晶状体损伤的防护效果。方法:对象采取尽量减少户外活动,戴有缘帽、防护镜及摄取新鲜蔬菜等措施。结果:通过本防护措施的实施,晶状体混浊的发生率由10a前的39.6%下降为16.5%,且晶状体混浊程度也有明显降低(P<0.01)。结论:在紫外线较强的高原地区,采取必要的防护措施,可有效地降低紫外线对晶状体的损伤,减少晶状体混浊的发生率、减少白内障的发病率,可有效地延缓人群中的白内障发病年龄。     

眼内醛脱氢酶在防止紫外线辐射损伤中的作用

人眼持续暴露于来自阳光紫外线辐射（ultraviolet radiation,UVR）中会产生大量的活性氧族（reactive oxygen species,ROS）,诱导氧化应激反应,产生毒性醛损伤眼组织.醛脱氢酶（aldehydedehydrogenase,ALDH）超家族是一类多功能蛋白,在内、外源性醛的代谢及抗氧化应激等过程中起着重要作用.ALDH在眼部防止UVR损伤的机制尚不明确.ALDH在眼部主要分布于角膜和晶状体中,其中ALDH1A1和ALDH3A1表达丰富,可能与抗UVR损伤有关.新近的研究提示,针对ALDH的药物可能对某些眼病有益.     

Impact of iris pigment and pupil size in ultraviolet radiation cataract in rat

Purpose: To investigate the effect of iris pigment and pupil size in ultraviolet radiation (UVR)‐induced cataract. Methods: Brown‐Norway rats (pigmented) and Fischer‐344 rats (non‐pigmented) were unilaterally exposed in vivo to 5 kJ/m² UVR. Each strain was split into two groups, each receiving either mydriatic (tropicamide) or miotic (pilocarpine) eye‐drops. One week after exposure, the degree of ocular inflammation and damage in the anterior segment was determined. The lenses were extracted, photographed and the degree of forward light scattering (cataract) was quantified. Results: The cataract types differed between the two strains. All Fischer rats developed macroscopically identifiable UVR cataract while only 41% of Brown‐Norway rats did so. All groups except the miotic Brown‐Norway developed significant light scattering. The Fischer rats developed 3–4‐fold more lens light scattering than the Brown‐Norway rats. The miotic Fischer group exhibited significantly more light scattering than the mydriatic Fischer group. There was no significant difference in light scattering between the two Brown‐Norway groups. There was a correlation between ocular inflammation and degree of light scattering, with Brown‐Norway rats exhibiting less inflammation and lens light scattering. Conclusions: Pigmented rats develop less UVR cataract and less ocular inflammation than non‐pigmented rats. Pupil size plays a smaller role in UVR cataract development in pigmented rats than in non‐pigmented. The role of UVR‐induced ocular inflammation in cataract development is still ambiguous.     

Anterior eye focusing of peripheral ultraviolet and visible radiation albedo

Concern about short- and long-term ultraviolet radiation (particularly UVB) damage to the eye has led to increased research in this area. Numerous studies have confirmed the pathogenic enhancing roles of reflected ultraviolet (UV) and visible radiation in our environment. There is concern that conventional sunglasses do not protect the eye adequately from reflected rays (albedo), especially on the lateral aspect, from behind and from below. Using eye models and computer ray tracing methods, the pathways of oblique rays incident at the temporal peripheral cornea have been plotted by Maloof, Ho and Coroneo.¹ These rays are refracted and focused and theoretically can result in up to 20 times the concentration of incident irradiance at the nasal anterior chamber angle and nasal equatorial cortex of the crystalline lens. The purpose of this study was to determine the limits of angular subtense of the incident peripheral light which is refracted in this manner in human subjects and to investigate the relation between corneal shape and certain ocular parameters to the limits. A statistically significant positive correlation was found between temporal entrance angle and anterior chamber depth (r = 0.70, P< 0.0006). The entrance angle ranged from 15 degrees to 30 degrees and was located 10 degrees to 45 degrees posterior to the coronal plane. Our results support Maloof and colleagues' predictions for the implication of focused peripheral UV and high intensity visible radiation in the pathogenesis of pterygium and cortical cataract and emphasise the need for lateral eye protection in conditions of high ultraviolet albedo.     

The ocular dose of ultraviolet radiation to outdoor workers

Ocular ultraviolet radiation (UVR) exposure was assessed in three occupational groups: fisherman, landscape workers and construction workers. The ratio of ocular exposure to ambient exposure was determined by placing UV-sensitive film (295-320 nm) between the eyes of the subjects and in a nearby open field. The mean ocular exposures varied between 2 and 17% of the ambient exposure on a horizontal surface, depending on whether subjects wore hats, the job performed and the time of year. Wearing a brimmed hat significantly reduced ocular exposure in all groups of subjects. Subjects working over more reflective surfaces had significantly higher ocular exposure. A seasonal effect on the ocular ambient exposure ratio (OAER) was also observed. These results are consistent with measurements of OAER in mannikin and measurements of surface reflectivity in this and previous studies. The results provide parameters which can be used in modeling ocular UVR exposure in epidemiological and clinical studies.     

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.