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Question
By closing the eyes and gently pressing them by your palms, you may see some specks of brilliant light. How do you get this sensation while there is no light entering your eyes?
Solution 1
If we look at a bright object and then close our eyes, the sensation of light persists for a short period of time. This is known as the persistence image or the after image. It lasts for one-tenth of a second. Therefore, by closing your eyes and gently pressing them with your palms, you see some specks of brilliant light.
Solution 2
Phosphenes are the sense of seeing dazzling light after gently touching the eyes with your palms. Mechanical activation of retinal cells causes this behaviour, even when no external light is present. This is how it happens:
- Mechanical Stimulation: Closing your eyes and lightly pressing them with your palms applies pressure to the eyeballs.
- Stimulation of Retinal Cells: Pressure on the eyeballs stimulates retinal cells, including photoreceptors (rods and cones).
- Activation of the Optic Nerve: Stimulated retinal cells transmit messages to the brain via the optic nerve.
- Perception of Light: The brain interprets these signals as light, resulting in the impression of phosphenes, or dazzling light.
Mechanical stimulation mimics the impact of light on the retina, creating a sense of light even when no external light enters the eyes. Other ways to create phosphenes include rubbing your eyes or being exposed to strong magnetic fields.
Notes
Students can refer to the provided solutions based on their preferred marks.
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