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

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.

Vitamin D and myopia: a review

Myopia is a worldwide public health problem of vision disorder caused by multiple factors, which has posed a huge socioeconomic burden, raising concerns about sight-threatening ocular complications. Vitamin D, as a kind of fat-soluble vitamin, related to time-spent-outdoors, has been considered by extensive studies to have potential relationship with myopia. We reviewed studies published in a decade which estimated the association of blood vitamin D status with myopia and summarized the universality and individuality of all research articles. Several research articles suggested the known environmental risk factors of myopia, including age, gender, ethnicity, education level, parental and school conditions, time-spent-outdoors, and sunlight exposure, and recent epidemiological studies demonstrate that increased vitamin D levels, by virtue of the extended outdoor time, may be an important modifiable factor and a protective effect that delay the progression of myopia in children and adolescents rather than in adults. The genetic studies have been conducted to get access to the evidence of gene polymorphism for explaining the association of serum vitamin D status and myopia, but the precise genetic interpretation of vitamin D and myopia remains unclear so far; on the other hand, the possible mechanisms are various like copolymerization mechanism, calcium homeostasis and imbalance of ciliary muscle function regulation, but nearly all of the investigators are inclined to remain skeptical. This article reviews the age-related epidemiological proofs, existent genetics correlations, possible underlying biological mechanisms and further values for the protective association between vitamin D and myopia, providing the possibility of prevention or postponement for myopia.

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.

Environmental influences on ophthalmic conditions: A scoping review

BACKGROUND

Environmental factors have been implicated in various eye pathologies. The purpose of this review is to synthesise the published research on environmental effects on eye disease.

METHODS

Four databases were searched for terms relating to environmental exposures and ophthalmic disease. Titles and abstracts were screened followed by full-text review. Data was extracted from 118 included studies. Quality assessment was conducted for each study.

RESULTS

Air pollutants, including nitrogen dioxide, nitrites, sulphur dioxide, particulate matter, carbon monoxide, ozone and hydrocarbons are associated with ocular conditions ranging from corneal damage to various retinopathies, including central retinal artery occlusion. Certain chemicals and metals, such as cadmium, are associated with increased risk of age-related macular degeneration. Climate factors, such as sun exposure, have been associated with the development of cataracts. Living in rural areas was associated with various age-related eye diseases whereas people living in urban settings had higher risk for dry eye disease and uveitis.

CONCLUSION

Environmental exposures in every domain are associated with various ophthalmic conditions. These findings underscore the importance of continued research on the interplay between the environment and eye health.

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.

Effects of air pollution on myopia: an update on clinical evidence and biological mechanisms

Myopia is one of the most common forms of refractive eye disease and considered as a worldwide pandemic experienced by half of the global population by 2050. During the past several decades, myopia has become a leading cause of visual impairment, whereas several factors are believed to be associated with its occurrence and development. In terms of environmental factors, air pollution has gained more attention in recent years, as exposure to ambient air pollution seems to increase peripheral hyperopia defocus, affect the dopamine pathways, and cause retinal ischemia. In this review, we highlight epidemiological evidence and potential biological mechanisms that may link exposure to air pollutants to myopia. A thorough understanding of these mechanisms is a key for establishing and implementing targeting strategies. Regulatory efforts to control air pollution through effective policies and limit individual exposure to preventable risks are required in reducing this global public health burden.

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.

Low Serum Vitamin D Is Not Correlated With Myopia in Chinese Children and Adolescents

Purpose

This cross-sectional study investigated the association between serum 25-hydroxyvitamin D [25(OH)D] concentration and myopia in two groups of Chinese children aged 6–14 years from different geographic and economic locations.

Methods

A total of 294 children from a lowland area and 89 from a highland area were enrolled as two groups of study subjects. The visual acuity, ocular biometry, and automated refraction were measured. The serum level of 25(OH)D was determined by chemiluminescence immunoassay. Near vision and outdoor exposure durations were assessed with a questionnaire interview. Data were analyzed for differences using Chi-square and Wilcoxon rank sum tests. The risk factors were evaluated using logistic regression analysis.

Results

We found that the serum level of 25(OH)D of the subjects from lowland area was 20.9 ng/mL which was higher than that of subjects from highland area (16.9 ng/mL). The median spherical equivalent refraction (SER) was −0.25 diopters(D) in lowland subjects and −0.63D in highland subjects. The prevalence of myopia was 45.2% in lowland subjects and 55.1% in highland subjects. The average axial length was similar, 23.6 mm and 23.1 mm in lowland and highland subjects, respectively. We found no statistical difference between the average SER and serum 25(OH)D concentration in subjects of either lowland or highland area. The ratio of myopia to non-myopia was also similar in subjects with three levels (sufficient, deficient, and insufficient) of serum 25(OH)D in these two areas.

Conclusions

There is no association between serum 25(OH)D concentration and myopia in the 6–14 years old Chinese children.

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.

Effect of Sunshine Duration on Myopia in Primary School Students from Northern and Southern China

Background

To assess the current myopia prevalence rate and evaluate the effect of sunshine duration on myopia among primary school students in the north and south of China.

Methods

This prospective cross-sectional study pooled data from 9171 primary school students (grades from 1 to 6) from four cities in the north and south of China. National Geomatics Center of China (NGCC) and China Meteorological Administration provided data about altitude, latitude, longitude, average annual temperature, and average annual sunshine duration. Non-cycloplegic refraction was recorded, and prevalence rates in primary school students and factors associated with myopia were analyzed. Univariate and multivariate logistic regression models were used to determine the independent association of risk factors of myopia.

Results

The overall myopia prevalence was 28.0%, from 7.5% to 50.6% for first and sixth grades, respectively. Low, moderate and high myopia significantly increased with school grades from 7.30% to 35.0%, 0.3% to 13.60% and 0.00% to 1.9%, respectively. Multiple regression analysis revealed that longer average cumulative daylight hours were connected to lower myopia prevalence in primary school students (OR, 0.721; 95% CI, [0.593–0.877]; P=0.001), whereas girls and higher grade was independently associated with higher myopia prevalence (girls: β=0.189; OR, 1.208; 95% CI, [1.052–1.387]; P=0.007; higher grade: β=0.502; OR, 1.652; 95% CI, [1.580–1.726]; P<0.001).

Conclusion

This study demonstrated that myopia was highly prevalent in southern Chinese cities over northern ones, linked to shorter light exposure, higher education level, and female gender. Such findings reinforced the beneficial impact of daylight exposure with a protective role against myopia development.

Damage of the ocular surface from indoor suntanning-Insights from in vivo confocal microscopy

PURPOSE

To evaluate the ocular surface at the microstructural level of adults who habitually undertake indoor-suntanning utilising in vivo confocal microscopy.

METHODS

Participants were prospectively recruited and enrolled into either а study group (n = 75) with a history UV indoor tanning, or a control group (n = 75) with no prior history of artificial tanning. The study group participated in voluntary tanning sessions performed with standard equipment and maintained their usual routine for eye protection. Slit lamp biomicroscopy and in vivo confocal microscopy were performed at baseline before undertaking a series of suntanning sessions (10 sessions of 10 min duration over a 15 day period), within three days after the last session, and four weeks after the last session. Control group participants were examined at baseline and 8 weeks later and did not participate in tanning sessions.

RESULTS

All participants were female with a mean age of 25 ± 4 years and 24 ± 4 years in the study and control groups, respectively. No clinically significant changes were observed in either group over time using slit lamp biomicroscopy (all p ≥ 0.05), however, statistically significant differences were observed between the study and the control group for all corneal layers imaged using confocal microscopy (all p ≤ 0.03). Characteristic cystic conjunctival lesions with dark centres and bright borders were observed in 95% of the study group before and in 100% after the suntanning sessions.

CONCLUSION

Indoor suntanning resulted in statistically significant microstructural changes in the cornea and the bulbar conjunctiva that are undetectable with slit lamp biomicroscopy.

Conjunctival Ultraviolet Autofluorescence as a Measure of Riboflavin and Ultraviolet and Accelerated Cross-Linking Exposure in Keratoconic Patients

Purpose: The study was performed to analyze the prevalence of the conjunctival ultraviolet autofluorescence (CUVAF) area in keratoconic eyes and changes caused by UVA-irradiation as a component of accelerated corneal cross-linking (aCXL). Methods: The study group involved 20 keratoconic patients subjected to aCXL surgery in one eye. The comparative group consisted of 111 age- and sex-matched patients with healthy corneas. The images of the anterior segment in both patient groups were taken using a Coroneo camera. In the study group the photos were taken before and immediately after the surgery, and 7 and 30 days following the procedure. Results: Nasal and temporal autofluorescence area (AN+T) were significantly smaller in a keratoconic patients group compared to control group (p = 0.0001). Patients with the third stage of keratoconus had significantly higher AN+T (p = 0.0277) compared with individuals with lower stage keratoconus. No statistically significant CUVAF changes were observed after the aCXL procedure. In keratoconic patients with primary CUVAF undergoing aCXL, a temporary fast enlargement of the autofluorescence area was observed. Conclusions: The eyes undergoing the aCXL procedure showed no difference in the size of the CUVAF area but such patients should be in strict follow-up in order to reveal UV-related ocular surface diseases.

Genetic and environmental factors related to the development of myopic maculopathy in Spanish patients

High myopia and the subsequent degenerative changes of the retina, choroid, and sclera, known as myopic maculopathy (MM), are a serious visual problem in many Asian countries, and are beginning to be so in the south of Europe, especially in the Mediterranean. It is therefore necessary to carry out genetic and environmental studies to determine the possible causes of this disease. This study aims to verify if the genetic factors that have been most related to Asian populations are also associated in two Spanish cohorts. Eight SNPs from six genes (PAX6, SCO2, CCDC102B, BLID, chromosome 15q14, and COL8A1) along with demographic, ophthalmic and environmental factors were analysed in two cohorts from a total of 365 highly myopic subjects and 177 control subjects. The genetic analysis showed that COL8A1 SNP rs13095226 was associated with the development of choroidal neovascularization (CNV) and also seems to play an important role in the increase of axial length. The SNP rs634990 of chromosome 15q14 also showed a significant association with MM, although this was lost after the Bonferroni correction. Additional demographic and environmental factors, namely age, sex, smoking status, and pregnancy history, were also found to be associated with MM and CNV in this population.

Low 25-Hydroxyvitamin D Concentration Is Not Associated With Refractive Error in Middle-Aged and Older Western Australian Adults

Purpose

To investigate the association between serum 25-hydroxyvitamin D (25[OH]D) concentration and refractive error in a community-based cohort of adults aged 46 to 69 years.

Methods

Residents of the City of Busselton in Western Australia born between 1946 and 1964 were invited to participate. Participants underwent cycloplegic autorefraction and completed questionnaires on education, occupational sun exposure, and physical activity. Blood samples were collected and serum frozen at −80°C. Serum 25[OH]D concentration was measured by immunoassay. Data on 25[OH]D were deseasonalized and multivariate models built to analyze the association between 25[OH]D concentration and spherical equivalent and myopia, defined as spherical equivalent <−0.50 D.

Results

After exclusions, data were available for 4112 participants. Serum 25[OH]D concentration was not associated with spherical equivalent or myopia after adjustment for confounding factors (β = −0.01, 95% confidence interval [CI]: −0.03 to −0.008, P = 0.25, and odds ratio = 1.02, 95% CI: 0.99 to 1.05, P = 0.12, respectively). When participants were classified into 25[OH]D groups of lower (<50 nmol/L), medium (≥50 to <75 nmol/L), and upper (≥75 nmol/L), the upper group had slightly greater myopic refractive error than the medium group (P = 0.02) but not the lower group, after adjustment for confounders.

Conclusions

There was no substantial association between 25[OH]D levels and spherical equivalent or odds of myopia in this study. The association previously noted between low serum 25[OH]D level and myopia in younger Western Australians is not evident in later adulthood.

Translational Relevance

This study provides further evidence suggesting that vitamin D levels are unrelated to myopia risk in adults and thus not a suitable target for myopia intervention.

Repurposing blue laser autofluorescence to measure ocular sun exposure

IMPORTANCE

Excessive ocular sun exposure is linked to various eye pathologies. Conjunctival ultraviolet autofluorescence (CUVAF) is a method of detecting sun-related conjunctival damage; however, the custom-built camera system required is not readily available.

BACKGROUND

We investigated whether blue laser autofluorescence (BAF) on a commonly used confocal scanning laser ophthalmoscope (cSLO) can be utilized to measure CUVAF area.

DESIGN

Cross-sectional evaluation of a diagnostic technology at a medical research institute.

PARTICIPANTS

Sixty-four participants recruited from three on-going observational eye studies in Western Australia.

METHODS

All participants had four images, two of each eye, captured using the CUVAF camera and BAF on the same day. Participants with pterygium or poor quality images were excluded from the analysis. Two graders measured CUVAF area in each image twice. CUVAF area measured by BAF was then compared to measurements determined with the conventional camera system.

MAIN OUTCOME MEASURES

CUVAF area.

RESULTS

After exclusions, 50 participants' images were analysed. Intra- and inter-observer repeatability were similar between the two systems. When comparing CUVAF area measured by BAF to the camera measurement, grader 1 had a mean difference of +1.00 mm² , with 95% limits of agreement -5.75 to 7.77 mm² . Grader 2 had a mean difference of +0.21mm² , with 95% limits of agreement -7.22 to 7.64 mm² .

CONCLUSIONS AND RELEVANCE

BAF on a commercially available cSLO is a valid method for measuring CUVAF area. This finding provides broader opportunity for identifying, monitoring and educating patients with sun-exposure-related ocular conditions and for researching the ocular impacts of sun exposure.