Oxygen Distribution in the Human Eye: Relevance to the Etiology of Open-Angle Glaucoma after Vitrectomy

Abstract

Oxygen metabolism by the lens and cornea establishes oxygen gradients in the anterior segment. Vitrectomy and cataract surgery increase pO(2) in the anterior chamber angle, potentially damaging trabecular meshwork cells. We propose that oxygen levels in the anterior chamber angle are strongly influenced by oxygen derived from the ciliary body circulation.

Vitreoretinal influences on lens function and cataract

“…In any case, oxidative metabolism by superficial lens cells should assure that oxygen levels in the deeper fibre cells are much lower than near the lens surface. This prediction is supported by measurements of oxygen gradients across the lens in rabbits [27] and in the human lens nucleus [24], as well as by much higher pO 2 anterior to the lens after cataract surgery and intraocular lens implantation, when the superficial tissues at the anterior of the lens have been removed [22].…”

“…3% O 2 ) [19,20], a value that is close to the normal level of oxygen in most tissues. In the vitreous near the posterior of the human lens, the pO 2 drops to approximately 7 mmHg (approx.1% O 2 ) [21] and our recent measurements in human patients revealed that the pO 2 near the anterior and lateral surfaces of the lens is typically about 3 mmHg (less than 0.4%) [22]. The low oxygen near the surfaces of the lens and the consumption of oxygen by lens cells results in even lower pO 2 in the lens nucleus [23,24].…”

“…(a) Oxygen distribution around the lens A thin, fibreoptic oxygen sensor (optode) was used to map pO 2 in several regions of the anterior chamber and in the posterior and vitreous chambers of patients undergoing vitrectomy, cataract or glaucoma surgery [21,22]. Oxygen diffused from the superficial retinal vessels into the gel vitreous, reaching a partial pressure there of approximately 20 mmHg [20,31].…”

“…A steep oxygen gradient is also present across the fluid-filled anterior chamber, from %24 mmHg at the inner surface of the cornea to %3 mmHg near the anterior lens capsule [22]. As the cornea is avascular, the pO 2 at its inner surface is set by oxygen diffusion from the air at the outer surface of the cornea and oxygen consumption by corneal cells [33].…”

The occurrence of delayed ocular hypertension and glaucoma after pars plana vitrectomy for rhegmatogenous retinal detachment

“…The asterisk indicates thickening of the retinal nerve fibre layer in the temporal position of the right eye due to macular pucker formation (bottom). (Chang 2006;Siegfried et al 2010). Post-PPV glaucoma was shown to occur in up to 20% (Chang 2006).…”