Short answers, pulled from the story.
Visual perception is the ability to detect light and use it to form an image of the surrounding environment. Light enters the eye through the cornea, is focused by the lens onto the retina, where photoreceptor cells convert it into neural impulses that travel via the optic nerve to the brain.
Ibn al-Haytham (Alhazen), a scholar born in 965 and working around 1040, provided the first correct explanation of vision through intromission. In his Book of Optics (Kitab al-Manazir, completed around 1021), he demonstrated through systematic experiment that light reflected from objects enters the eye and is focused by the lens onto the retina.
Unconscious inference is the term Hermann von Helmholtz coined in 1867 to describe how the brain fills in incomplete visual information using prior experience and assumptions. Helmholtz concluded that the human eye alone cannot produce a high-quality image, and that the brain must compensate by making hidden predictions about the world.
Leonardo da Vinci (1452-1519) is believed to be the first to recognize the special optical qualities of the eye. He found that distinct and clear vision exists only along a single optical line ending at the fovea, effectively establishing the modern distinction between foveal and peripheral vision without using those exact terms.
There are four main types: fixational eye movements (including microsaccades, ocular drift, and tremor), saccadic movements that jump rapidly from point to point, vergence movements that coordinate both eyes to produce a single fused image, and pursuit movements that smoothly track objects in motion.
Face and object recognition rely on distinct neural systems. Prosopagnosic patients show deficits in face recognition with intact object recognition, while patient C.K. showed the opposite pattern. Faces also show strong inversion effects that objects do not. Doris Tsao and colleagues used fMRI and electrophysiology to describe specific brain regions and a mechanism for face recognition in macaque monkeys.