The relationship between outdoor exposure and myopia on university students, measured by conjunctival ultraviolet autofluorescence ( CUVAF)

Abstract Purpose: The purpose of this study was to analyse whether outdoor (OD) exposure could exert a protective effect against the development of myopia and HM, in two different cohorts of university students that differ in the time of OD activities in their study programs. Moreover, CUVAF, as an objective measure of time spent outdoors, was also investigated in this cohort. Methods: A cross‐sectional observational study was carried out using two different cohorts of students, one of medical students (MS) and the other of environmental science students (ESS). All participants underwent an automatic objective refraction, axial length measurement, colour fundus photographs, and CUVAF area (BAF module on the Heidelberg Spectralis HRA + OCT). All the participants filled out a questionnaire of life style and myopia history. For all statistical analyses, corrected p values < 0.05 (two‐tailed) were considered statistically significant using SPSS 20.1 Software. Results: A total of 208 participants were recruited, 156 were MS and 52 were ESS. The data showed that 66.66% of the MS were myopic versus only 50% of the ESS ( p = 0.021; OR 95 = 2.03 (95% CI 1.1–3.6). With regards to OD activities, ESS spent significantly more hours per week doing OD activities than MS ( p < 0.0001), but with respect to near work activities, there was no significant difference between both cohorts. In this sense, it was found that high myopia MS spent significantly fewer hours outdoors than their controls ( p < 0.05). The degree of myopia was inversely associated with CUVAF in all university students, and a statistically significant positive correlation was observed between spherical equivalent and CUVAF ( r = 0.248 [95% CI 0.094–0.390]; p = 0.001). Conclusions: The results showed that OD 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 OD exposure that is inversely associated with myopia, and can be useful to follow‐up myopic patients.