Reproducibility of retinal oxygen saturation in normal and treated glaucomatous eyes

Aim: To measure the reproducibility of retinal oxygen saturation (SaO₂) levels among treated glaucomatous eyes and normal controls in a prospective nonrandomised study. Methods: Patients with perimetric glaucoma (PG) and normal controls were included. Exclusion criteria for both groups included visual acuity <20/30, unreliable visual fields, thyroidopathies, hemoglobinopathies, cardiovascular and pulmonary diseases. Retinal oximetry was performed twice consecutively on one randomly selected eye of PG and normal controls using spectrophotometric retinal oximeter (SRO; Oxymap ehf., Iceland). Four main retinal vessel pairs were analysed separately. Coefficients of variability (CoV), coefficients of repeatability (CoR) and intraclass correlation coefficients (ICCs) in arteries (a.SaO₂) and veins (v.SaO₂) were calculated. Results: 23 PG (mean age 68.3±10.8 years) and 22 normal subjects (mean age 61.5±18.2 years; p=0.14) were included. The intraocular pressure and mean ocular perfusion pressure in glaucoma (14.4±4.2 mm Hg; 45.8 ±5.8 mm Hg) and controls (14.3±3.3 mm Hg; 45.8 ±6.1 mm Hg) were similar (p >0.05). In the PG group, the a.SaO₂ had a CoV of 1.6%, a CoR of 4.7 and an ICC of 0.97; the v.SaO₂ had a CoV of 5.9%, a CoR of 8.7 and an ICC of 0.96. In normals, the a.SaO₂ had a CoV of 0.98%, a CoR of 3.3 and an ICC of 0.97; the v.SaO₂ had a CoV of 4.8%, a CoR of 7.7 and an ICC of 0.93. Conclusions: Retinal oximetry measurements using SRO are highly reproducible in both treated glaucomatous and normal eyes.