Seasonal Effect on Ocular Sun Exposure and Conjunctival UV Autofluorescence

Abstract

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 2 visits 14±2 days apart. Ocular sun exposure was estimated over a two-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) mm2, 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 following sun exposure.

Repurposing blue laser autofluorescence to measure ocular sun exposure

“…First, the area of CUVAF is typically largest next to the limbus, in accordance with the peripheral light focussing effect in which light striking the cornea near the limbus temporally or nasally is focussed much more intensely at the opposite limbus . Second, those who spend more time outdoors or in the sun are more likely to have a larger CUVAF area . Third, higher median CUVAF area is associated with an increased risk of pterygium, a condition associated with ocular UV light exposure .…”

“…The fluorophore responsible for CUVAF is unknown. Lipofuscin, collagen cross‐links, tryptophan, nicotinamide adenine dinucleotide (NADH), or more generally, the presence of altered cellular or mitochondrial activity, have all been suggested as potential sources . Pingueculae autofluoresce strongly on CUVAF imaging and contain elastotic material and advanced glycation end‐products (AGEs), both of which autofluoresce in the cornea and skin .…”

“…Additionally, CUVAF images serve as an excellent patient education tool as areas of “sun damage” can be easily appreciated. Currently, CUVAF images are captured using a specialized custom‐built camera apparatus that is not readily available and thus only utilized in research settings . An alternative, accessible method of capturing CUVAF images could present greater opportunities for identifying and monitoring patients at risk of sun‐related eye disease, and for further research into the harms of ocular sun exposure.…”

“…2,7 Second, those who spend more time outdoors or in the sun are more likely to have a larger CUVAF area. [8][9][10][11][12] Third, higher median CUVAF area is associated with an increased risk of pterygium, a condition associated with ocular UV light exposure. 8 Last, CUVAF area in young adults is inversely associated with odds of myopia, a condition that is associated with less time spent outdoors during childhood and adolescence.…”

“…Lipofuscin, collagen cross-links, tryptophan, nicotinamide adenine dinucleotide (NADH), or more generally, the presence of altered cellular or mitochondrial activity, have all been suggested as potential sources. 11,18,19 Pingueculae autofluoresce strongly on CUVAF imaging and contain elastotic material and advanced glycation end-products (AGEs), both of which autofluoresce in the cornea and skin. 6,18,[20][21][22][23] Some AGEs form by cross-linking with proteins such as collagen or elastin and UV exposure can speed up this process.…”