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 (birth control) White. Reflexions also manufactured a flat-spring diaphragm up until 2014. There are a number of variations. The SILCS diaphragm is made of silicone, has an arcing spring, and a finger cup is molded on one end for easy removal. The Duet disposable diaphragm is made of dipped polyurethane, pre-filled with BufferGel (BufferGel is currently in clinical trials as a spermicide and microbicide). Both the SILCS and Duet diaphragms are one-size-fits-all. Diaphragms usually come in different sizes and require a fitting appointment with a health care professional to determine which size a woman should wear. Single size diaphragms that do not