Improvement in retinal vessel oxygen saturation after vitrectomy

Purpose

To evaluate the effects of vitrectomy on retinal vascular oxygen saturation.

Methods

This was a prospective observational study. 27 eyes of 27 patients who underwent vitrectomy for macular conditions were included. Retinal oximetry was performed using the Oxymap (Oxymap Inc., Reykjavik, Iceland) prior to vitrectomy and 3 months after surgery. The mean retinal arterial and venous oxygen saturation were measured and the arterial-venous difference (AVD) was calculated as the difference between the arterial and venous saturations.

Multivariate linear regression models were constructed to compare oxygen saturation before and after surgery, with adjustments for age, sex, hypertension, hyperlipidemia, diabetes mellitus and indication for surgery.

Results

The mean age of the subjects was 68.4 ± 8.9 years, 15 (55%) were male and the majority were of Chinese ethnicity (93%). The mean arterial saturation increased significantly after vitrectomy (101.93 ± 8.36% vs 96.16 ± 14.14%, p = 0.01). The mean venous saturation also increased significantly after surgery. (59.76 ± 8.52% vs 50.40 ± 11.72%, p = 0.02). The mean AVD significantly decreased from 45.76 ± 12.18% before surgery to 42.17 ± 10.94% after surgery (p = 0.02).

Conclusions

Retinal arterial and venous oxygen saturation are significantly increased after vitrectomy, while the AVD is decreased after vitrectomy. Our results suggest that vitrectomy enhances retinal oxygenation. This may account for the apparent benefit of vitrectomy on conditions with retinal hypoxia such as diabetic retinopathy.