Introduction  

In this pilot study the effects of vitrectomy on PO₂ in the vitreous cavity in CRVO were investigated.

Study design  

Prospective, controlled, interventional study.

Method  

Six patients with ischaemic CRVO in one eye (undergoing vitrectomy for radial optic neurotomy, RON) and six with either macula hole or membrane were included. An oxygen probe was inserted before removal of the vitreous (pre-vitrectomy) and after removal of the vitreous (post-vitrectomy). In the patients with CRVO, measurements were taken before RON was performed. Oxygenation recordings (PO₂) were taken in the mid-vitreous cavity and the preretinal vitreous.

Results  

Mean age was 65 years. In controls, pre-vitrectomy, the mean PO₂ adjacent to the retina (15.0 mmHg S.D.5.7) was significantly less than mid-cavity (33.7 mmHg S.D.12.8). Similarly in CRVO, the pre-vitrectomy pre-retinal PO₂ (8.1 mmHg S.D. 3.5), was significantly less than mid-cavity (19.8 mmHg S.D.7.3). The mean PO₂ was significantly less in the eyes with CRVO than in control eyes. Post-vitrectomy, the PO₂ was significantly greater than pre-vitrectomy at both recording sites in the controls mid-cavity (61.5 mmHg S.D.13.9) and pre-retinal (75.8 mmHg S.D. 9.1), and CRVO eyes mid-cavity (53.7 mmHg S.D. 17.9) and pre-retinal (59.8 mmHg S.D. 15.8).

Conclusion  

PO₂ is reduced in the vitreous cavity in CRVO. Vitrectomy may be a method of increasing oxygen availability to the retina.