Researchers recently used an online survey to track women’s daily ocular symptoms for 40 days. In doing so, they hoped to better understand how their menstrual cycle—and any oral contraceptive use—impacts daily changes in symptoms.

Previous research suggests women are more likely to experience ocular surface symptoms, possibly due to variable estrogen levels, the researchers said in the study. Thus, changing hormone levels likely influence fluctuating ocular symptoms, although little data exists to corroborate such hypotheses, they wrote in the study.

To gather more information and help make the connection, they asked 36 normally menstruating women and another 36 using an oral contraceptive to complete a daily online survey, consisting to two questions, to track their ocular symptoms. They found the survey tool effectively measured instantaneous symptoms with good diagnostic ability and repeatability. Most notably, they confirmed a cyclic fluctuation across the women’s menstrual cycles, with the most symptoms appearing on the second day when estrogen levels are at the lowest. In addition, those on oral contraceptives reported significantly higher symptom scores.

Clinicians should take a woman’s menstrual phase and oral contraceptive use into consideration when interpreting ocular symptoms, the researchers conclude. “These findings enhance the current understandings of ocular surface and systemic pain during menstrual cycle.”