Depending on the precise time of day of light exposure, the internal clock will shift either earlier or later. For example, inadvertent evening light exposure can delay the clock and suppress pineal melatonin when the therapeutic goal is to advance the clock. This can confound efforts to achieve normal sleep onset. The most active delaying agent falls in the short-wavelength visible range of light. Using appropriately filtered wraparound lenses at the end of the day these disruptive effects can be minimized in coordination with afternoon or evening melatonin treatment, morning light therapy, or both.