The eye is the lamp of the body. So if the eye is clear, the whole body will be full of light.’ - Jesus
I interpret the eye as meaning the third eye, the point between the eyebrows. This point is directly linked to the pineal gland in the centre of the brain. When you activate the pineal through various methods such as pranayama, meditations, you can have a dmt experience, which is a natural high and happiness. This is what i would say Jesus is telling us when he says the whole body will be full of light.
In the feel good state that the third eye creates, one forgets the woes of the external and is filled with joy in the present moment where life happens.
The Egyptians knew this as the eye of Horus.
Jesus would have learned this from his own experience and from his travels to India where he wen as a young man. The great sages would have been his teachers seeing that he already was a higher consciousness.