Vitrectomy surgery increases oxygen exposure to the lens: A possible mechanism for nuclear cataract formation

Measurement of PO2 during vitrectomy for central retinal vein occlusion, a pilot study

“…With this study in human eyes a PO 2 gradient was observed in control and CRVO eyes, but decreasing towards the retina. A similar, small gradient, has also been measured between anterior and mid-vitreal spaces in human eyes 19 . Therefore, we hypothesise that in human eyes other fractions of ocular blood flow do indeed contribute significantly to vitreal O 2 content, and furthermore that the vitreous may actually be an O 2 source to the retina, especially during ischaemia.…”

“…We do not know how long these higher PO 2 levels persisted postoperatively, however in animal studies raised PO 2 levels persisted for up to eight weeks 18 and in a human study PO 2 levels were higher in patients reinvestigated after previous vitrectomy 19 . Vitrectomy may therefore be useful as a therapy for ischaemic eye conditions, particularly in the retina, e.g.…”

Raman spectroscopic evidence for nuclear disulfide in isolated lenses of hyperbaric oxygen-treated guinea pigs

“…Treatment of guinea pigs with HBO has been shown to produce a two-fold increase in lens focal length viability, compared to age-matched controls (Bantseev et al, 2004). The results help to explain the observed induction of nuclear cataracts in human patients treated with HBO (Palmquist et al, 1984), and may also be relevant to the development of maturity-onset and vitrectomy-induced human nuclear cataracts since these types of cataracts are also thought to be caused by O 2 (Dische and Zil, 1951;Holekamp et al, 2005;Ogura et al, 1991). The level of increase of -SS-in the lens nucleus of O 2 -treated guinea pigs, compared to age-matched controls, was found to be more than two-fold (Fig.…”

“…Recent studies have linked molecular oxygen (O 2 ) with lens nuclear opacity (Holekamp et al, 2005;Simpanya et al, 2005), and it is possible that O 2 is a precursor to a more active, harmful species within the lens that can generate disulfide (-SS-). We treat guinea pigs with hyperbaric oxygen (HBO) in order to investigate events leading to nuclear cataract, and have used this technique to demonstrate an association between O 2 -induced lens nuclear light scattering and an increase in the level of PSSP (Giblin et al, 1995;Simpanya et al, 2005).…”

Nitric oxide levels in the anterior chamber of vitrectomized eyes with silicon oil

“…Posterior vitrectomy can modify the gradient of oxygen concentration in the vitreous cavity (26,27) . When the vitreous gel is present and intact there is a diffusion of oxygen from the retinal arterioles into the vitreous and then, an uptake of this oxygen by the retinal tissue (27) .…”