Snape couldn't quite help the lopsided grin that stole across his face at Scorpius' comments. "Cruciatus," he assured the lad from a wealth of personal experience, "is invariably 'special'. That draught you just took should mitigate those symptoms. As for the bleeding," he added in grimmer tones, "we'll jump off that bridge when we come to it."
Because Scorpius was the only one of his patients who was at all tolerable, Snape actually troubled himself to explain, "Serpentine curses often make subtle changes to the structures of the eye, resulting in referred-pain migraines or vision-induced nausea."