Abstract
Background: Females suffer from a cluster of symptoms during premenstrual phase. Those subside on the onset of menstruation. Varied symptoms are confusion, headache, decrease in alertness, forgetfulness, and mood fluctuations. Cyclical variation in ovarian hormones is responsible for these symptoms. These hormones affect reaction time (RT) of an individual to a particular stimulus. RT gives us information about sensorimotor association and processing capability of central nervous system.

Aims and Objectives: To study the influence of phases of menstrual cycle on visual RT (VRT).

Materials and Methods: Seventy females in the age group of 18–21 years were selected for the study. VRT was assessed in pre- and post-menstrual phase with portable instrument. Results were analyzed using Student’s paired t test.

Results: The study shows highly statistically significant prolongation of VRT in premenstrual phase as compared to postmenstrual phase.

Conclusion: Prolongation of VRT in premenstrual phase is predominantly due to high levels of progesterone. It exerts its action centrally through inhibitory neurotransmitter gamma-aminobutyric acid. It delays neuronal conduction time. Effects of progesterone locally acting on the ocular tissue and the intraocular fluid also contribute to prolonging VRT in premenstrual phase.