Human eye The upper end of the range is given in terms of normal visual performance as 10 cd/m (100,000,000 or one hundred million candelas per square meter). The eye includes a lens similar to lenses found in optical instruments such as cameras and the same physics principles can be applied. The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop. Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it
The Eye in the Door The Eye in the Door The Eye in the Door is a novel by Pat Barker, first published in 1993, and forming the second part of the "Regeneration" trilogy. "The Eye in the Door" is set in London, beginning in mid-April, 1918, and continues the interwoven stories of Dr William Rivers, Billy Prior, and Siegfried Sassoon begun in "Regeneration". It ends some time before the conclusion of the First World War later the same year. The third part of the trilogy, "The Ghost Road", continues the story. Whereas "Regeneration" is an anomalous, but not unique, mixture of fact and fiction,