Characterization of the Effects of Hyperbaric Oxygen on the Biochemical and Optical Properties of the Bovine Lens.
OBJECTIVE
To assess the morphologic, biochemical, and optical properties of bovine lenses treated with hyperbaric oxygen.


METHODS
Lenses were exposed to hyperbaric nitrogen (HBN) or hyperbaric oxygen (HBO) for 5 or 15 hours, lens transparency was assessed using bright field microscopy and lens morphology was visualized using confocal microscopy. Lenses were dissected into the outer cortex, inner cortex, and core, and glutathione (GSH) and malondialdehyde (MDA) measured. Gel electrophoresis and Western blotting were used to detect high molecular weight aggregates (HMW) and glutathione mixed protein disulfides (PSSG). T2-weighted MRI was used to measure lens geometry and map the water/protein ratio to allow gradient refractive index (GRIN) profiles to be calculated. Optical modeling software calculated the change in lens optical power, and an anatomically correct model of the light pathway of the bovine eye was used to determine the effects of HBN and HBO on focal length and overall image quality.


RESULTS
Lenses were transparent and lens morphology similar between HBN- and HBO-treated lenses. At 5- and 15-hour HBO exposure, GSH and GSSG were depleted and MDA increased in the core. Glutathione mixed protein disulfides were detected in the outer and inner cortex only with no appearance of HMW. Optical changes were detectable only with 15-hour HBO treatment with a decrease in the refractive index of the core, slightly reduced lens thickness, and an increase in optimal focal length, consistent with a hyperopic shift.


CONCLUSIONS
This system may serve as a model to study changes that occur with advanced aging rather than nuclear cataract formation per se.
Department of Physiology, School of Medical Sciences, NZ National Eye Centre, University of Auckland, New Zealand 2School of Optometry and Vison Science, NZ National Eye Centre, University of Auckland, New Zealand.
Julie C
JC
Lim
School of Optometry and Vison Science, NZ National Eye Centre, University of Auckland, New Zealand.
Ehsan
E
Vaghefi
Department of Physiology, School of Medical Sciences, NZ National Eye Centre, University of Auckland, New Zealand.
Bo
B
Li
Department of Physiology, School of Medical Sciences, NZ National Eye Centre, University of Auckland, New Zealand 2School of Optometry and Vison Science, NZ National Eye Centre, University of Auckland, New Zealand.
Mitchell G
MG
Nye-Wood
Department of Physiology, School of Medical Sciences, NZ National Eye Centre, University of Auckland, New Zealand 2School of Optometry and Vison Science, NZ National Eye Centre, University of Auckland, New Zealand.
Paul J
PJ
Donaldson
D000818:Animals; D015153:Blotting, Western; D002386:Cataract / Q000209:etiology; D002417:Cattle; D004195:Disease Models, Animal; D004591:Electrophoresis, Polyacrylamide Gel; D005978:Glutathione / Q000032:analysis; D006931:Hyperbaric Oxygenation; D007908:Lens, Crystalline / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008315:Malondialdehyde / Q000032:analysis
D008315:Malondialdehyde; D005978:Glutathione