title: Determination of oxygen tension on rabbit corneas under contact lenses.
abstract: OBJECTIVE
  To determine oxygen tension (PO2) on rabbit corneas beneath rigid gas permeable (RGP), hydrogel, and silicone elastomer lenses under open- and closed-eye conditions and to demonstrate the relationship between PO2 and overnight corneal swelling response in the rabbit model.
  
  
  METHODS
  An improved PO2 monitoring system (PO-2080) with a platinum-micro-wire-electrode was used to measure PO2. An ultrasonic pachymeter (DGH-2000) was used to measure corneal thickness after overnight wear.
  
  
  RESULTS
  The relationship between PO2 and oxygen transmissibility (Dk/ L) of the contact lens was linear for Dk/L between 0 and 70 x 10(-9) (cm/ sec)(mLO2/mL x mmHg). For Dk/L greater than 70 x 10(-9), PO2 gradually reached a plateau at 120 mmHg for open-eye conditions and 20 mmHg for closed-eye conditions. PO2 was inversely related to the overnight corneal swelling, ranging from 5.1% swelling at PO2 113.5/17.5 mmHg (open/closed-eye) for a hyper Dk/L lens (125 x 10(-9)) to 15.1% swelling at PO2 10.4/5.1 mmHg for a low Dk/L lens (11.5 x 10(-9)).
  
  
  CONCLUSIONS
  Polarographic determination of PO2 provides reliable information about the amount of oxygen available to the cornea under a lens for both open-eye and closed-eye conditions. The data demonstrate that it is not possible to achieve normal oxygen levels with contact lens wear, even when hyper Dk/L lenses are worn.
authors.affiliation: R&D Department, Menicon Co., Ltd., Nagoya, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Ichijima
authors.forename: T
authors.initials: T
authors.lastname: Hayashi
authors.forename: S
authors.initials: S
authors.lastname: Mitsunaga
authors.forename: H
authors.initials: H
authors.lastname: Hamano
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology; D003261:Contact Lenses / Q000009:adverse effects; D003315:Cornea / Q000378:metabolism*; D015715:Corneal Edema / Q000209:etiology / Q000378:metabolism; D005143:Eyelids / Q000502:physiology; D008839:Microelectrodes; D010100:Oxygen / Q000493:pharmacokinetics; D010313:Partial Pressure; D010539:Permeability; D011048:Polarography / Q000295:instrumentation; D011817:Rabbits; D012016:Reference Values
chemical_list: D010100:Oxygen