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
Diaphragm pacing Diaphragm pacing Diaphragm pacing, (and even earlier as electrophrenic respiration), is the rhythmic application of electrical impulses to the diaphragm to provide ventilatory support for respiratory failure or sleep apnea. Historically, this has been accomplished through the electrical stimulation of a phrenic nerve by an implanted receiver/electrode, though today an alternative option of attaching percutaneous wires to the diaphragm exists. The idea of stimulating the diaphragm through the phrenic nerve was first firmly postulated by German physician Christoph Wilhelm Hufeland, who in 1783 proposed that such a technique could be applied as a treatment for asphyxia. French neurologist Duchenne de