My experince occurred during the last of 6 ketamine infusions, for 30 years of diagnosed depression/bipolar 2/PTSD with highest ketamine dosage for my weight.
Partway through my infusion, I began to see a circle of light above, with rays of lower intensity extending downward. My sense of joy and excitement similar to sexual climax (not an actual physical sensation, though). Color was non-existent and insignificant, with no awareness of peripheral areas on left and right. A desirable sense of pulling toward the light, which I wanted to go to. Non-audible message of belief of greater being, release of worries of future, to forgive those who have caused me hurt and trauma.
He/they were unseeable, but with me. I felt a sense of joy, but also rapid mouth-breathing, tears flowing, very loud crying and begging, "Please, please help me!" I wanted to stay and shouted, "No, no," not to go back, but knew I needed to go back.
Time was non-existent throughout this experience.