This isn't the ancient points of light in the desert night sky. It isn't even light - it's just neurons misfiring and his brain interpreting danger as beauty.
Instead of the stars in the night sky, Snow's overshadowed by a woman resembling a black hole; a woman who's not reflecting any light and who's absorbing everything around her. Regina's body is merged into this woman's; a woman who is now effectively deciding whether Snow will breathe or not, in a much more literal sense than Snow would have ever imagined.
Her visual system is creating light where there's no actual light. If she could open her eyes she'd be surrounded by the darkness of her lover's room, curtains drawn to shield them from the light pollution of the London skyline. Regina has surrounded them with darkness, making sure that the only light Snow is able to see is the light that originates from own her touch; a direct result of the hand that suppresses Snow's trachea and deprives her of air.
It isn't the Afghan skies Snow sees. Even if every coherent thought is evacuated in this moment, sense memory isn't. The lights Snow experiences now might look like the night sky in the sharp, clear desert air where she once thought her blood would spill into the sand until there was no more. The pain had been peripheral - it was the vast emptiness and the sensation of life running out of her body that had persisted into his memories of that night.
This is another form of dissolution under a different night sky. This is a brilliant supernova that gives her false sensations of light as she drives into Snow's body with forceful, slow movements. And Snow shouldn't allow this, it's too close to dying for someone who has almost died too many times, but then again; that might just be the purpose of it all. For Regina to override all of her previous sensations and fears.
The breathy sounds of her lover above her, the flashes of lights on her retina and then the obscene sounds that echoes around them as Regina finally surges into her, leaving her cells there to diffuse and invade Snow's. Then the alleviation of pressure on her trachea as Regina's mouth hovers above her own, letting her own air merge with Snow's lack of breath. She fills Snow's mouth with her breath before she finally allows Snow to take her own breaths again.
Blinking her eyes open,Snow's vision is blurry from the prolonged asphyxiation and the saline rapidly filling her eyes. The first thing that emerges from the haze is the face of her lover, and the light sensations are replaced with a reflection of darkness and light merged into one; into the eyes of the woman who still holds her hard enough to bruise.
This isn't the clouded lights of the London night. It isn't even light - it's just neurons misfiring and her brain interpreting Regina as a conductor of light sensations.