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

Corneal Epithelial Cell Density Is Reduced in Young Adults With Conjunctival Ultraviolet Autofluorescence

PURPOSE

The aim of this study was to investigate the effects of chronic ultraviolet (UV) radiation exposure on the corneal microstructure using conjunctival UV autofluorescence (CUVAF) as a marker of exposure.

METHODS

Young healthy adults aged 18 to 35 years were recruited. Participant's demographics and sun exposure behavior were recorded using questionnaires. Images of the bulbar conjunctiva from the right eye were captured and analyzed for the CUVAF area. Corneal microstructure was assessed by in vivo confocal microscopy and anterior segment optical coherence tomography. The presence of palisades of Vogt in all 4 limbal quadrants was recorded.

RESULTS

CUVAF was observed in 31 of 52 eyes (60%), with a mean (±SD) nasal, temporal, and total CUVAF area of 5.39 ± 4.16 mm 2 , 4.29 ± 4.27 mm 2 , and 9.67 ± 7.01 mm 2 , respectively. Individuals with CUVAF were significantly more likely to report undertaking moderate-intensity to high-intensity outdoor exercise ( P = 0.021). Individuals with CUVAF were less likely to have visible nasal and temporal palisades of Vogt ( P = 0.011). Corneal basal cell densities anterior to the nerve whorl ( P < 0.001) and nasally ( P = 0.005) were lower in individuals with CUVAF. Wing cell density anterior to the nerve whorl was lower in individuals with CUVAF ( P = 0.011). No significant changes in the central and limbal corneal epithelial thickness were observed.

CONCLUSIONS

Significant reductions in corneal epithelial cell density were observed in individuals with CUVAF, a biomarker of chronic UV exposure. This observation suggests that chronic UV exposure is damaging to the corneal microstructure.

Could Children's Myopization Have Been Avoided during the Pandemic Confinement? The Conjunctival Ultraviolet Autofluorescence (CUVAF) Biomarker as an Answer

BACKGROUND

The objective of this study was to evaluate the association of the presence of conjunctival ultraviolet autofluorescence (CUVAF) with the level and progression of myopia and the impact of reduced sunlight exposure during the COVID-19 pandemic confinement (PC).

METHODS

A retrospective observational study was carried out using three cohorts, children (9-17 years old), young adults (18-25 years old), and adults (>40 years old) with myopia (≤0.75D) and at least three annual eye examinations (before and after PC). All participants underwent an automatic objective refraction and CUVAF area analysis. All the participants filled out a questionnaire regarding lifestyle and myopia history.

RESULTS

The 298 recruited participants showed that during the PC, children's and young adults' myopia progression rate increased on average by -0.50 and -0.30 D/year, respectively, compared with the pre-pandemic level (p < 0.0001 and p < 0.01). A significantly greater progression was observed in those with low baseline myopia compared to those with moderate or high myopia (p < 0.01). CUVAF shows its protective effect associated with outdoor activity (OA) with regard to the age of onset of myopia and mean diopters (p < 0.01). In fact, although there were no differences in the increase in diopters between children with and without CUVAF during the PC, those who had CUVAF started with lower gains (-0.3 D/year) compared to those who did not (-0.5 D/year; p < 0.05). The myopia treatments (atropine drops, Ortho-K, and MiSight® contact lenses) showed a reduction effect in myopic progression rate post-PC in comparison with non-treated children (p < 0.0001, p < 0.0001 and p < 0.01, respectively).

CONCLUSIONS

The strict restriction of OA during PC led to the rate of myopia progression doubling among children and young adults. This progression occurred mainly in children with previously low myopia, and CUVAF, as a biomarker of OA, reflects its potential to provide benefits in the form of recommended behavioral changes to protect against the development of myopia.

Conjunctival ultraviolet autofluorescence as a biomarker of outdoor exposure in myopia: a systematic review and meta-analysis

Outdoor exposure is considered the primary modifiable risk factor in preventing the development of myopia. This effect is thought to be attributed to the light-induced synthesis and release of dopamine in the retina. However, until recent years, there was no objective quantifiable method available to measure the association between time spent outdoors and myopia. It is only recently that the conjunctival ultraviolet autofluorescence (CUVAF) area, serving as a biomarker for sun exposure, has begun to be utilized in numerous studies. To provide a comprehensive summary of the relevant evidence pertaining to the association between the CUVAF area and myopia across different geographic regions and age groups, a systematic review and meta-analysis were conducted. The search encompassed multiple databases, including MEDLINE, SCIENCE DIRECT, GOOGLE SCHOLAR, WEB OF SCIENCE, and SCOPUS, and utilized specific search terms such as "conjunctival ultraviolet autofluorescence", "CUVAF", "UVAF", "objective marker of ocular sun exposure", "myopia", "degenerative myopia", and "high myopia". The bibliographic research included papers published between the years 2006 and 2022. A total of 4051 records were initially identified, and after duplicates were removed, 49 articles underwent full-text review. Nine articles were included in the systematic review. These studies covered myopia and outdoor exposure across different regions (Australia, Europe and India) with a total population of 3615 individuals. They found that myopes generally had smaller CUVAF areas compared to non-myopes. The meta-analysis confirmed this, revealing statistically smaller CUVAF areas in myopic patients, with a mean difference of - 3.30 mm2 (95% CI - 5.53; - 1.06). Additionally, some studies showed a positive correlation between more outdoor exposure and larger CUVAF areas. In terms of outdoor exposure time, myopic patients reported less time outdoors than non-myopic individuals, with a mean difference of - 3.38 h/week (95% CI - 4.66; - 2.09). Overall, these findings highlight the connection between outdoor exposure, CUVAF area and myopia, with regional variations playing a significant role. The results of this meta-analysis validate CUVAF as a quantitative method to objectively measure outdoor exposure in relation with myopia development.

The association between conjunctival and scleral thickness and ocular surface ultraviolet autofluorescence

Ultraviolet autofluorescence (UVAF) imaging is used to visualise ocular surface changes due to sunlight exposure and so is considered to be a biomarker for UV damage. The conjunctival and scleral thicknesses of participants with and without ocular surface UVAF were measured to examine the UVAF associated tissue thicknesses. The presence of UVAF on the ocular surface was associated with significant differences in tissue thickness including thinner conjunctival epitheliums and thicker scleras but predominantly thickening of the conjunctival stroma. Participants were also classified into four groups according to the presence and absence of UVAF on both the temporal and nasal conjunctivas. It was noted that for those that had only nasal UVAF, the temporal conjunctival stroma was significantly thicker even without the presence of UVAF. Some participants with temporal UVAF had signs of pinguecula observed with slit lamp examination and some had OCT SLO enface imaging darkening. These findings highlight the potential of techniques other than slit lamp examination, including tissue thickness measurement and UVAF photography, in the detection of early UV-related changes to the ocular surface.

A Cross-Sectional Observational Study of the Relationship between Outdoor Exposure and Myopia in University Students, Measured by Conjunctival Ultraviolet Autofluorescence (CUVAF)

Myopia is the most common refractive error worldwide. This cannot be explained by genetic factors alone, therefore, environmental factors may play an important role. Hence, the main objective of this study was to analyse whether outdoor exposure could exert a protective effect against the development of myopia in a cohort of young adults and to investigate ultraviolet autofluorescence (CUVAF), as a biomarker of time spent outdoors. A cross-sectional observational study was carried out using two cohorts. A total of 208 participants were recruited, 156 medical students and 52 environmental science students. The data showed that 66.66% of the medical students were myopic, while 50% of the environmental science students were myopic (p = 0.021). Environmental science students spent significantly more hours per week doing outdoor activities than medical students (p < 0.0001), but there was no significant difference with respect to near work activities between them. In both cohorts, the degree of myopia was inversely associated with CUVAF, and a statistically significant positive correlation was observed between spherical equivalent and CUVAF (Pearson’s r = 0.248). In conclusion, outdoor activities could reduce the onset and progression of myopia not only in children, but also in young adults. In addition, CUVAF represents an objective, non-invasive biomarker of outdoor exposure that is inversely associated with myopia.

Prevalence and Risk Factors of Myopia in Young Adults: Review of Findings From the Raine Study

Myopia tends to develop and progress fastest during childhood, and the age of stabilization has been reported to be 15-16 years old. Thus, most studies on myopia have centered on children. Data on the refractive error profile in young adulthood - a time in life when myopia is thought to have stabilized and refractive error is unaffected by age-related pathology such as cataract - are limited. The Raine Study has been following a community-based cohort of young adults representative of the general Western Australia population since their prenatal periods in 1989-1991, with eye examinations performed when participants were 20 and 28 years old. At 20 years old, prevalence of myopia in the cohort was 25.8%. Using long-term trajectory of serum vitamin D levels and conjunctival ultraviolet autofluorescence (CUVAF) area to objectively quantify sun exposure, the Raine Study confirmed a negative relationship between time spent outdoors and myopia prevalence. However, prospective studies are required to determine the amount of CUVAF area or serum vitamin D levels associated with time duration. Combining data from the Raine Study and several other cohorts, Mendelian randomization studies have confirmed a link between myopia and a genetic predisposition toward higher education. Several novel potential associations of myopia or ocular biometry were investigated, including fetal growth trajectory, which was found to be significantly associated with corneal curvature at 20 years. By age 28, myopia prevalence had increased to 33.2%. Between 20 and 28 years old, myopia progressed and axial length elongated, on average, by -0.041D/year and 0.02 mm/year, respectively. Smaller CUVAF area at follow-up, female sex, and parental myopia were significant risk factors for myopia incidence and progression between 20 and 28 years. Given the limited research in young adults, further investigations are warranted to confirm the Raine Study findings, as well as identify novel genetic or environmental factors of myopia incidence and progression in this age group.

Conjunctival ultraviolet autofluorescence area decreases with age and sunglasses use

BACKGROUND

Conjunctival ultraviolet autofluorescence (CUVAF) is a method of detecting conjunctival damage related to ultraviolet radiation exposure. In cross-sectional studies, CUVAF area is positively associated with self-reported time spent outdoors and pterygium and negatively associated with myopia; however, longitudinal studies are scarce.

AIMS

To use a novel deep learning-based tool to assess 8-year change in CUVAF area in young adults, investigate factors associated with this change and identify the number of new onset pterygia.

METHODS

A deep learning-based CUVAF tool was developed to measure CUVAF area. CUVAF area and pterygium status were assessed at three study visits: baseline (participants were approximately 20 years old) and at 7-year and 8-year follow-ups. Participants self-reported sun protection behaviours and ocular history.

RESULTS

CUVAF data were available for 1497 participants from at least one study visit; 633 (43%) participants had complete CUVAF data. Mean CUVAF areas at baseline and the 7-year and 8-year follow-ups were 48.4, 39.3 and 37.7 mm², respectively. There was a decrease in mean CUVAF area over time (change in total CUVAF area=-0.96 mm² per year (95% CI: -1.07 to -0.86)). For participants who wore sunglasses ≥1/2 of the time, CUVAF area decreased by an additional -0.42 mm² per year (95% CI: -0.72 to -0.12) on average. Fourteen (1.5%) participants developed a pterygium.

CONCLUSIONS

In this young adult cohort, CUVAF area declined over an 8-year period. Wearing sunglasses was associated with a faster reduction in CUVAF area. Deep learning-based models can assist in accurate and efficient measurement of CUVAF area.

Challenges in Eye Care in the Asia-Pacific Region

The Asia-Pacific region is home to a 4.3-billion population and one of the most rapidly aging regions. Addressing the eye care needs in the region would greatly boost the progress toward achieving universal eye health. Over 20 countries/regions have actively engaged in the "VISION 2020" initiative launched since 1999, and remarkable achievements have been witnessed as demonstrated by an increase in both the number and density of ophthalmologists in almost all countries. Nevertheless, formidable and emerging challenges are to be overcome in the coming century. From 1990 to 2015, the absolute number of blind people increased by 17.9%, largely due to population growth and aging. The Asia-Pacific region, the most populous continent with a rapidly aging population, would inevitably be left to tackle this challenge. Furthermore, a high prevalence of blinding eye diseases imposes great pressure on current eye care services, with South Asia having the highest age-standardized prevalence of moderate to severe visual impairment (17.5%) and mild vision impairment (12.2%) globally, and high-income countries having the highest overall prevalence of myopia, reaching 53.4% with East Asia having the second-highest overall prevalence (51.6%). Moreover, the availability of ophthalmic resources varies greatly in the region, with the density of ophthalmologists ranging from over 114 ophthalmologists per million population in Japan to 0 in Micronesia, and a highly disproportionate urban-rural distribution. This article aims to shed light on challenges faced by the Asia-Pacific ophthalmic community and propose corresponding strategies to tackle those challenges.

Has the Sun Protection Campaign in Australia Reduced the Need for Pterygium Surgery Nationally?

BACKGROUND

The Slip! Slop! Slap! Sunsmart safety campaign was an Australian initiative implemented in the 1980s. To assess this campaign's effect on pterygium, we examined the rate of pterygium surgery across Australia and described the prevalence and associations of pterygium in Perth, Australia's sunniest capital city.

METHODS

The rate of pterygium surgery was examined using Australian Medicare data. A cross-sectional analysis of the Generation 1 (Gen1) cohort of the Raine Study was performed to investigate the prevalence of pterygium in Perth. We investigated the association between pterygium and conjunctival ultraviolet autofluorescence (CUVAF) area, an objective biomarker of sun exposure, and demographics and health variables derived from a detailed questionnaire.

RESULTS

Between 1994 and 2017, the rate of Medicare funded pterygium surgery in Western Australia fell 11%, well below the national average decline of 47%. Of the 1049 Gen1 Raine Study participants, 994 (571 females; mean age 56.7 years, range = 40.9-81.7) were included in the analysis. The lifetime prevalence of pterygium was 8.4% (n = 83). A higher prevalence of pterygium was associated with outdoor occupation (p-trend = 0.007), male sex (p-trend 0.01) and increasing CUVAF area (p-value <0.001).

CONCLUSIONS

The effect of Australia's Slip! Slop! Slap! Sunsmart safety campaign on pterygium been mixed. Since 1994, the rate of private pterygium surgery has declined significantly in all Australian states except Western Australia. Perth, Western Australia, has the highest pterygium prevalence of any mainland-Australian cohort. Higher CUVAF area, male sex, and outdoor occupation were associated with an increased risk of pterygium.

Effect of UV-absorbing Contact Lenses on Conjunctival Ultraviolet Autofluorescence

PURPOSE

The intended purpose of UV-absorbing contact lenses is to protect the cornea and posterior ocular structures from UV-induced damage. Few studies report conjunctival effects of UV-absorbing contact lens materials. The purpose of this study was to evaluate conjunctival ultraviolet autofluorescence (UVAF) for contact lens wearers of UV-absorbing and minimally UV-absorbing materials.

METHODS

Forty-four volunteers enrolled in the cross-sectional study. Three groups were recruited; non-contact lens wearers (n = 15), minimally UV-absorbing contact lens wearers (n = 15), and UV-absorbing contact lens wearers (n = 14). Ocular sun exposure was calculated using self-reported measures. Conjunctival UVAF images of temporal and nasal conjunctiva, acquired using a Nikon D7000 camera system adapted with appropriate flash and filter system, were analyzed using ImageJ. A sub-group of participants including only subjects with measurable UVAF was analyzed.

RESULTS

No significant differences were present between groups found similar for age, gender, and ocular sun exposure. The area of UVAF significantly increased following lens removal for UV-absorbing contact lens wearers compared with non-contact lens wearers. Furthermore, for contact lens wearers compared with non-lens wearers, area of UVAF was significantly greater between right and left eyes (p = .04 minimally UV-absorbing, p = .01 UV-absorbing), and between nasal (p = .046 minimally UV-absorbing, p = .01 UV-absorbing), and temporal (p = .01 UV-absorbing) areas. However, no significant difference was found between contact lens wearers of the two groups. No difference was found between nasal and temporal UVAF regions during contact lens wear (p = .28) or after lens removal (p = .16) (Mann-Whitney U).

CONCLUSIONS

Contact lens materials have conjunctival effects, with increased UVAF in both UV-absorbing and minimally UV-absorbing contact lens wearers compared with non-lens wearers. UV-absorbing and minimally UV-absorbing contact lens materials appear to influence nasal and temporal areas of the ocular surface equally.

Conjunctival ultraviolet autofluorescence area, but not intensity, is associated with myopia

BACKGROUND

Conjunctival ultraviolet autofluorescence (CUVAF) has been used as a biomarker of time spent outdoors. Smaller CUVAF area is associated with myopia in southern hemisphere cohorts. Further research is required to determine if this association is replicated in northern latitudes and whether average CUVAF intensity is a valuable metric. This prospective study explored the association between myopia, CUVAF (area and intensity) and additional indicators of sun exposure (vitamin D₃ and self-reported sun exposure preferences) across seasons at a location of 55° north.

METHODS

Young adults (age 18-20) provided blood samples biannually (March/April and September/October) over an 18-month period (four phases) for the assessment of 25-hydroxyvitamin D (25(OH)D₃ ) concentrations (liquid chromatography-tandem mass spectrometry). CUVAF (total area, average intensity) and self-reported sun exposure preferences were recorded at each phase. Axial length and corneal radius were measured. Refractive error was measured by autorefractor and spherical equivalent refraction used to classify participants into refractive groups: myopic (spherical equivalent refraction ≤ -0.50 DS) or non-myopic.

RESULTS

Fifty-four participants (24 myopes, 30 non-myopes) participated. CUVAF area was negatively associated with the presence of myopia (odds ratio = 0.94, 95 per cent confidence interval = 0.90-0.98, p = 0.002). Myopes = 4.5 mm² (interquartile range [IQR] 0.95-6.4 mm² ), non-myopes = 7.0 mm² (IQR = 2.0-10.7 mm² ). No significant association was found between CUVAF intensity and refractive group (p = 0.17). There was no significant association between sun exposure preferences or serum concentration of 25(OH)D₃ and refractive status (all p ≥ 0.21). CUVAF measures were not associated with ocular biometry measures (all p ≥ 0.084). CUVAF area was unaffected by season (all p ≥ 0.45) and variations in CUVAF area over the study period did not exceed the repeatability of the measurement technique.

CONCLUSION

Myopia was associated with smaller areas of CUVAF indicative of less cumulative ultraviolet-B exposure. These findings suggest that CUVAF measures are a useful, non-invasive biomarker of the time spent outdoors in adults in northern hemisphere populations.

Dry eye disease and oxidative stress

Dry eye, an age-related condition, is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance and tear film instability. Environmental factors are also often implicated in dry eye including exposure to pollutants, ultraviolet (UV) radiation and ozone as well as the chronic use of preserved eyedrops such as in the treatment of glaucoma. These factors increase oxidative stress and ocular surface inflammation. Here, we reviewed the cellular, animal and clinical studies that point to the role of oxidative stress in dry eye disease. The biomarkers used to indicate oxidative damage in ocular surface tissues include 8-hydroxy-2 deoxyguanosine (8-OHdG), 4-hydroxynonenal (HNE) and malondialdehyde (MDD). Antioxidative defences in the ocular surface occur in the form of tear proteins such as lactoferrin and S100A proteins, and enzymes such as superoxide dismutase (SOD), peroxidase, catalase and mitochondrial oxidative enzymes. An imbalance between the level of reactive oxygen species (ROS) and the action of protective enzymes will lead to oxidative damage, and possibly inflammation. A small number of interventional studies suggest that oxidative stress may be directly targeted in topical therapy of dry eye treatment. For example, in vitro studies suggest that L-carnitine and pterostilbene, a blueberry component may reduce oxidative stress, and in animal studies, alpha-lipoic acid (ALP) and selenoprotein P may be helpful. Examples of treatments used in clinical trials include vitamin B12 eyedrops and iodide iontophoresis. With recent emphasis on ageing medicine and preventive holistic health, as well as the role of environmental science, research on oxidative stress in the ocular surface is likely to have increasing impact in the coming years.

Seasonal Effect on Ocular Sun Exposure and Conjunctival UV Autofluorescence

PURPOSE

To evaluate feasibility and repeatability of measures for ocular sun exposure and conjunctival ultraviolet autofluorescence (UVAF), and to test for relationships between the outcomes.

METHODS

Fifty volunteers were seen for two visits 14 ± 2 days apart. Ocular sun exposure was estimated over a 2-week time period using questionnaires that quantified time outdoors and ocular protection habits. Conjunctival UVAF was imaged using a Nikon D7000 camera system equipped with appropriate flash and filter system; image analysis was done using ImageJ software. Repeatability estimates were made using Bland-Altman plots with mean differences and 95% limits of agreement calculated. Non-normally distributed data was transformed by either log10 or square root methods. Linear regression was conducted to evaluate relationships between measures.

RESULTS

Mean (±SD) values for ocular sun exposure and conjunctival UVAF were 8.86 (±11.97) hours and 9.15 (±9.47) mm, respectively. Repeatability was found to be acceptable for both ocular sun exposure and conjunctival UVAF. Univariate linear regression showed outdoor occupation to be a predictor of higher ocular sun exposure; outdoor occupation and winter season of collection both predicted higher total UVAF. Furthermore, increased portion of day spent outdoors while working was associated with increased total conjunctival UVAF.

CONCLUSIONS

We demonstrate feasibility and repeatability of estimating ocular sun exposure using a previously unreported method and for conjunctival UVAF in a group of subjects residing in Ohio. Seasonal temperature variation may have influenced time outdoors and ultimately calculation of ocular sun exposure. As winter season of collection and outdoor occupation both predicted higher total UVAF, our data suggests that ocular sun exposure is associated with conjunctival UVAF and, possibly, that UVAF remains for at least several months after sun exposure.

The use of conjunctival ultraviolet autofluorescence (CUVAF) as a biomarker of time spent outdoors

PURPOSE

Conjunctival ultraviolet autofluorescence (CUVAF) has been used in previous Southern Hemisphere myopia research as a marker for time spent outdoors. The validity of CUVAF as an indicator of time spent outdoors is yet to be explored in the Northern Hemisphere. It is unclear if CUVAF represents damage attributed to UV exposure or dry eye. This cross-sectional study investigated the association between CUVAF measures, self-reported time spent outdoors and measures of dry eye.

METHODS

Participants were recruited from University staff and students (n = 50, 19-64 years; mean 41). None were using topical ocular medications (with the exception of dry eye treatments). Sun exposure and dry eye questionnaires (Ocular Surface Disease Index and McMonnies) were completed by the participant. Dryness was also assessed using slit lamp biomicroscopy and invasive tear break up time. Images of the temporal and nasal conjunctiva from the right and left eye were captured using a bespoke photography system. The total CUVAF area, average CUVAF pixel intensity per mm(2) and total CUVAF pixel intensity were analysed using MATLAB R2013a (The MathWorks Inc).

RESULTS

Of the 50 participants, 42% were classified as having dry eye. Self-reported sunglasses use was negatively associated with all CUVAF measures (Kruskal Wallis total CUVAF area, p = 0.04, ptrend  = 0.03, average CUVAF pixel intensity p = 0.02, ptrend  = 0.02, total CUVAF pixel intensity: p = 0.04, ptrend  = 0.02). Time spent outdoors was positively associated with all CUVAF measures (Spearman's correlation coefficients, total CUVAF area: r = 0.37, p = 0.01, average CUVAF pixel intensity: r = 0.36, p = 0.01, total CUVAF pixel intensity: r = 0.37, p = 0.01) and remained significant when sunglasses use was controlled for (partial correlation, total CUVAF area: r = 0.32, p = 0.03, average CUVAF pixel intensity: r = 0.39, p = 0.01, total CUVAF pixel intensity: r = 0.39, p = 0.03). Neither CUVAF area nor intensity measures were associated with any dry eye measure (Ocular Surface Disease Index: all p ≥ 0.41, corneal staining: all p ≥ 0.38, McMonnies: all r ≤ 0.09 all p ≥ 0.52, slit lamp biomicroscopy: all r ≤ 0.20 all p ≥ 0.17, invasive tear break up time: all r ≤ -0.07 all p ≥ 0.31).

CONCLUSIONS

CUVAF area and intensity were not associated with clinical measures of dry eye. Greater CUVAF area and intensity were associated with wearing sunglasses less frequently and spending more time outdoors. If sunglass wear is accounted for, CUVAF may be a useful biomarker of time spent outdoors in future myopia studies.

Conjunctival Ultraviolet Autofluorescence as a Measure of Past Sun Exposure in Children

Background: Conjunctival ultraviolet autofluorescence (CUVAF) area detected from UVAF photographs is a recently developed potential marker for past sun exposure, but its relationship with sun-related factors has not been fully investigated.Methods: The study included 339 healthy children ages 5 to 15 years in Melbourne, Australia. Data were collected by questionnaire and examination at school. CUVAF area was measured using a computer program and analyzed as a continuous and dichotomous outcome (any/none).Results: Fifty-three children (15.6%) had detectable CUVAF, and the youngest age at which a child showed sun damage was 8 years. Compared with silicone skin cast score, there was good inter-grader agreement on CUVAF grading, with Cohen kappa 0.85 [95% confidence interval (CI), 0.65-1.00] for total CUVAF area using both eye photographs. Perfect intra-grader agreement was achieved. Fairer pigmentation, including medium/fair skin color [adjusted odds ratio (AOR), 3.42; 95% CI, 1.02-11.48 vs. dark/olive] and blue/gray eye color (AOR, 4.07; 95% CI, 1.73-9.55 vs. brown) was associated with increased odds of CUVAF. Increasing lifetime sunburn number (e.g., AOR, 2.89; 95% CI, 1.14-7.35 and 4.29; 1.04-17.76 for sunburns 2 to 4 and ≥ 5 times, respectively, vs. no sunburns, trend P = 0.004) and freckling by the end of last summer were associated with increased odds of CUVAF.Conclusions: CUVAF area can be an a priori objective measure of past sun exposure in pediatric populations for future research.Impact: To our knowledge, this is the first pediatric study that evaluated associations of sun-related risk factors with CUVAF. Cancer Epidemiol Biomarkers Prev; 26(7); 1146-53. ©2017 AACR.

Quantification of sun-related changes in the eye in conjunctival ultraviolet autofluorescence images

Quantification of sun-related changes in conjunctival ultraviolet autofluorescence (CUVAF) images is a subjective and tedious task, in which reproducibility of results is difficult. Thus, we have developed a semiautomatic method in MATLAB(®) to analyze CUVAF images retrospectively. The algorithm was validated on 200 images from 50 randomly selected participants from the Western Australian Pregnancy Cohort (Raine) study 20-year follow-up assessment, in which CUVAF area measurements were available from previous manual analysis. Algorithm performance was compared to manual measurements and yielded better than 95% correspondence in both intra- and interobserver agreement. Furthermore, the semiautomatic method significantly reduced analysis time by 50%.

Measuring sun exposure in epidemiological studies: Matching the method to the research question

Sun exposure has risks and benefits for health. Testing these associations requires tools for measuring sun exposure that are feasible and relevant to the time-course of the health outcome. Recent sun exposure, e.g. the last week, is best captured by dosimeters and sun diaries. These can also be used for medium-term sun exposure e.g. over several weeks, but incur a high participant burden. Self-reported data on "typical time outdoors" for working and non-working days, is less detailed and not influenced by day-to-day variation. Over a longer period, e.g. the lifetime, or for particular life stages, proxies of sun exposure, such as latitude of residence or ambient ultraviolet (UV) radiation levels (from satellites or ground-level monitoring) can be used, with additional detail provided by lifetime sun exposure calendars that include locations of residence, usual time outdoors, and detail of sunburn episodes. Objective measures of lifetime sun exposure include microtopography of sun-exposed skin (e.g. using silicone casts) or conjunctival UV autofluorescence. Potential modifiers of the association between sun exposure and the health outcome, such as clothing coverage and skin colour, may also need to be measured. We provide a systematic approach to selecting sun exposure measures for use in epidemiological health research.

Pterygium and conjunctival ultraviolet autofluorescence in young Australian adults: the Raine study

BACKGROUND

Sun exposure is associated with several ophthalmic diseases, including pterygium which may develop in adolescence. This study reports the prevalence of pterygium and its associations in a large cohort of young Australian adults. Conjunctival ultraviolet autofluorescence, a biomarker of ocular sun exposure, has recently been characterized in some Australian populations.

DESIGN

Cross-sectional population-based study.

PARTICIPANTS

One thousand three hundred forty-four subjects aged 18-22 years in the Western Australian Pregnancy Cohort (Raine) Study.

METHODS

Standardized colour and ultraviolet autofluorescence photographs of the nasal and temporal conjunctiva were taken, and assessed for presence of pterygium and area of autofluorescence. Sun exposure and protective factors were assessed by structured questionnaire.

MAIN OUTCOME MEASURES

Area of conjunctival ultraviolet autofluorescence in square millimetre (mm(2)) and presence of pterygium.

RESULTS

Median total conjunctival autofluorescence was 44.2 mm(2) (interquartile range 20.2-69.8 mm(2)). Median conjunctival autofluorescence was higher in nasal than in temporal quadrants (23.8 mm(2) vs. 18.9 mm(2), P < 0.001), but did not differ according to age or gender. Higher body mass index was associated with lower levels of autofluorescence. Total autofluorescence increased with increasing time spent outdoors. Prevalence of pterygium was 1.2% (95% confidence interval 0.6-1.8%), and was associated with male gender (odds ratio 6.71, P = 0.012). Participants with pterygium had significantly more conjunctival autofluorescence than those without (median 73.4 mm(2) vs. 44.0 mm(2), P = 0.001).

CONCLUSIONS

Conjunctival ultraviolet autofluorescence is associated with increased time spent outdoors, and increased prevalence of pterygium. The association of this biomarker with other ophthalmohelioses, including cataract, ocular surface squamous neoplasia and eyelid malignancy, has yet to be determined.

Myopia in young adults is inversely related to an objective marker of ocular sun exposure: the Western Australian Raine cohort study

PURPOSE

To determine the association between ocular sun exposure measured by conjunctival ultraviolet (UV) autofluorescence and myopic refractive error in young adults.

DESIGN

Cross-sectional study.

METHODS

setting: Population-based cohort in Western Australia. study population: Total of 1344 mostly white subjects aged 19-22 years in the Western Australian Pregnancy Cohort (Raine) Eye Health Study. observation procedures: Cycloplegic autorefraction, conjunctival ultraviolet autofluorescence photography, participant questionnaire. main outcome measures: Prevalence of myopic refractive error (spherical equivalent less than -0.50 diopters) and area of conjunctival ultraviolet autofluorescence in mm(2).

RESULTS

There was an inverse relationship between myopic refractive error and ocular sun exposure, with more than double the prevalence of myopia in the lowest quartile of conjunctival autofluorescence than the highest quartile (33.0% vs 15.6%). Median area of autofluorescence was significantly lower in myopic than in nonmyopic subjects (31.9 mm(2) vs 47.9 mm(2), P < .001). These differences remained significant after adjustment for age, sex, parental history of myopia, and subject level of education. The use of corrective lenses did not explain the lower conjunctival autofluorescence observed in myopic subjects.

CONCLUSIONS

In this young adult population, myopic refractive error was inversely associated with objectively measured ocular sun exposure, even after adjustment for potential confounders. This further supports the inverse association between outdoor activity and myopia.

Conjunctival UV autofluorescence--prevalence and risk factors

PURPOSE

Autofluorescence of ultraviolet (UV) light has been shown to occur in localised areas of the bulbar conjunctiva, which map to active cellular changes due to UV and environmental exposure. This study examined the presence of conjunctival UV autofluorescence in eye care practitioners (ECPs) across Europe and the Middle East and its associated risk factors.

METHOD

Images were captured of 307 ECPs right eyes in the Czech Republic, Germany, Greece, Kuwait, Netherlands, Sweden, Switzerland, United Arab Emirates and the United Kingdom using a Nikon D100 camera and dual flash units through UV filters. UV autofluorescence was outlined using ImageJ software and the nasal and temporal area quantified. Subjects were required to complete a questionnaire on their demographics and lifestyle including general exposure to UV and refractive correction.

RESULTS

Average age of the subjects was 38.5±12.2 years (range 19-68) and 39.7% were male. Sixty-two percent of eyes had some conjunctival damage as indicated by UV autofluorescence. The average area of damage was higher (p=0.005) nasally (2.95±4.52mm(2)) than temporally (2.19±4.17mm(2)). The area of UV damage was not related to age (r=0.03, p=0.674), gender (p=0.194), self-reported sun exposure lifestyle (p>0.05), geographical location (p=0174), sunglasses use (p>0.05) or UV-blocking contact lens use (p>0.05), although it was higher in those wearing contact lenses with minimal UV-blocking and no spectacles (p=0.015). The area of UV damage was also less nasally in those who wore contact lenses and spectacles compared to those with no refractive correction use (p=0.011 nasal; p=0.958 temporal).

CONCLUSION

UV conjunctival damage is common even in Europe, Kuwait and UAE, and among ECPs. The area of damage appears to be linked with the use of refractive correction, with greater damage nasally than temporally which may be explained by the peripheral light focusing effect.

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 mm(2)) [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 mm(2)) 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.