It's an unsettling experience, projecting an image of someone's inner eye so neatly into your own, retina examining retina through the intermediary of a lens. It can be disorientating too: gazing down the axis of the beam is like looking up into the night sky with an eyeglass. If the central retinal vein is blocked, the resultant scarlet haemorrhages are described in the textbooks as 'stormy sunset appearance.' I sometimes see pale retinal spots caused by diabetes, and they're reminiscent of cumulus clouds. In patients with high blood pressure the branching, silvered shine on the retinal arteries resembles jagged forks of lightning. The first time I looked into the curved vault of a patient's eyeball I was reminded of those medieval diagrams that showed the heavens as an upturned bowl.from Adventures in Human Being by Gavin Francis (2015)
Image from Utriusque Cosmi by Robert Fludd (1617)
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