The effect of vitreomacular and cataract surgery on oxygen saturation in retinal vessels

Abstract

Purpose: To evaluate the effects of vitreomacular and cataract surgery on retinal oximetry in vitreomacular disease.

Patients and methods: Thirty-eight eyes with epiretinal membrane (ERM) and 15 with idiopathic macular hole (MH) underwent 25 gauge pars plana vitrectomy combined with cataract surgery and intraocular lens implantation. Retinal oximetry was performed using the Oxymap T1 before, 1 month, and 6 months after surgery. Oxymap T1 simultaneously captures monochrome images of the fundus at two different wavelengths of light. Built-in Oxymap Analyzer software measures the oxygen saturation and vessel diameter.

Results: Mean arterial oxygen saturation significantly increased from 96.8%±6.2% to 100.2%±5.8% at 1 month and to 99.6%±5.8% at 6 months after surgery (P<0.01). Mean venous oxygen saturation also significantly increased from 54.6%±7.5% to 61.2%±6.4% at 1 month and to 62.6%±5.9% at 6 months after surgery (P<0.01). Mean arteriovenous (A-V) difference decreased from 42.2%±6.6% to 39.0%±7.8% at 1 month and to 37.0%±6.9% at 6 months after surgery (P<0.01). The ERM and MH groups showed similar changes in retinal oxygen saturation. However, there were no significant changes in the caliber of major retinal vessels after surgery (from 125.2±15.2 μm to 124.0±15.4 μm in artery, from 168.7±14.6 μm to 169.8±14.6 μm in vein).

Conclusion: Oxymap T1 was able to measure the increase in oxygen saturation in retinal arteries and veins, which led to a decrease in the A-V difference in oxygen saturation after vitrectomy combined with cataract surgery.

Keywords: oxygen saturation; retinal vessels; vitrectomy; vitreomacular disease.

Figure 1

Fundus images at two different wavelengths of light obtained by Oxymap T1 and the oxygen saturation map analyzed by Oxymap Analyzer. Notes: Oxymap T1 simultaneously captures 50° monochrome images centered at the optic disk at two different wavelengths of light (570 nm and 600 nm): (A) 570 nm is the reference isosbestic wavelength that is insensitive to oxygen concentration and (B) 600 nm is the oxygen-sensitive wavelength. (C) Oxymap Analyzer automatically calculates the oxygen saturation in each selected vessel and produces a color oxygen saturation map. Retinal vessels with higher oxygen saturation are indicated with red to orange color. Green to purple color indicates the retinal vessels with lower oxygen saturation. (D) For the analysis, vessel selection was performed disk-centered, 1.5-disk to 3-disk diameter area, and 1 disk diameter away from the disk margin.

Figure 2

Oxygen saturation in major retinal vessels before the surgery and 1 month and 6 months after the surgery. Notes: Left graph: overall subjects; center graph: ERM subject; right graph: MH subject. Upper solid line: arterial saturation; middle solid line: venous saturation; lower broken line: A-V difference. *P<0.05, **P<0.01 compared before surgery. Abbreviations: ERM, epiretinal membrane; MH, macular hole; A-V, arteriovenous; m, months.

Figure 3

Vessel diameter before the surgery and 1 month and 6 months after the surgery. Notes: Left graph: overall subjects; center graph: ERM subject; right graph: MH subject. Upper broken line: vein; lower solid line: artery. *P<0.05 compared before surgery. Abbreviations: ERM, epiretinal membrane; MH, macular hole; m, months.