The critical flicker fusion frequency (CFF) is the frequency at which a flickering stimulus is perceived to be constant; the quick recognition of variation in stimuli indicates the active coordination between eyes and brain. When human eyes get exposed to the light radiating from Smartphone screen for longer period that driven us into recognizable mental and visual fatigue results in sleep disturbances, mood fluctuations, insomnia, dry eyes, computer vision syndrome, misconceptions and tactile hallucinations. In the present study the CFF frequency test has been used to evaluate the mental and visual fatigue due to continuous Smartphone overuse.