De praecipius visus symptomatis eorumque causis Physica & Medica contemplatio

LIIII.
Yet the reason brought forward by Galen does not seem sufficient for the matter when scrutinized more carefully according to an exact norm. Plato asserted that to phos diakritikon light is distinguishing, and it is certain that a lesser light is obscured by a greater, and that the eyes are offended in that way, but that affection will result in katachesin a pouring down/covering, not in kath' hexin a fixed condition, the author of absolute blindness.

LV.
For if anyone is blinded from a more attentive staring at the sun, because the internal spirit has been dissipated by the gleaming ray, this would be a light loss to be repaired by nature in a short time; for with the eye closed, it will return, or it will be gathered again in a shady and opaque place.

LVI.
And if a hectic and stable blindness follows from that, it is necessary that either the substance of the brain be deeply vitiated, or the optic nerve obstructed. But the substance of the brain is not injured without the weakening of the temperament, which happens successively and in the progress of time, not in a moment. Light does not change the temperament by itself, as it has no commerce with the hot, cold, dry, and moist, which are subjected to touch; furthermore, it moves in an instant and suddenly affects the objects.

LVII.
But also, a corrupted brain is accompanied by the destruction of many faculties, and thus to blindness would be added paralysis, akinesia lack of movement, and anaisthēsia insensibility of the eyes, since the offshoots of these nerves spring from a nearby origin, which, however, experience denies.

LVIII.
Much less does intense light [cause] the obstruction of the optic nerves