Does a flash of light during meditation mean anything?

A flash by itself cannot confirm that communication is happening or that the pineal gland is involved. Visual flashes can have ordinary causes, including eye strain or changes in how the visual system is responding. Try easing off the intense focus and keeping your eyes relaxed rather than pressing your attention hard into one spot.

If the flashes are new or keep happening, especially with new floaters, a shadow or curtain in your vision, reduced vision, or significant pain, get prompt advice from an eye-care professional. Sudden vision changes are worth checking rather than interpreting through meditation.

I’d treat the experience as something you noticed, not as proof of a particular source. For a while, you could use a softer meditation focus, stop if pressure builds, and jot down when the flashes happen, how long they last, and whether they occur outside practice too. That gives you a clearer picture without assuming what they mean.