critical oxygen requirement

oxygen requirement, critical (COR) 

The minimum oxygen pressure at the epithelial surface required to prevent corneal swelling during the day. This value was initially assumed to be between 11 and 19 mmHg but it is nowadays considered to be at least 74 mmHg near the centre of the cornea (or 10% EOP or a Dk/L of about 25 ✕ 10−9 (cm2 ml O2)/(s ml mmHg) at 25ºC for daily wear. This figure increases to at least 90 ✕ 10−9 for overnight wear. Syn. critical oxygen tension. See hypoxia.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
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