L’oxymétrie du nerf optique, un biomarqueur potentiel pour le glaucome
Glaucoma is a progressive optic neuropathy characterized by loss of the retinal nerve fibers layer. This disease causes a decrease in the visual field that can lead to blindness. The main risk factor for glaucoma is the increase of intraocular pressure. However, not all glaucoma patients have an elevated intraocular pressure and many patients continue to progress despite good intraocular pressure control with current therapies. Several authors have focused on the hemodynamic components of the eye. They obtained significant differences in these factors between normal and glaucoma patients. Ocular oximetry is technology that can non-invasively measure oxygen saturation of eye tissues. Several studies have verified the association between ocular oximetry and glaucoma. The Zilia device uses diffuse spectroscopic reflectance to measure oxygen saturation at a specific point. The objective of this study was to verify the repeatability of the oximetry measurements on the head of the optic nerve obtained with the Zilia device and to study the acquisition in order to determine the characteristics necessary to obtain it optimally. Also, we measured the oxygen saturation (SaO2) on the optic nerve of normal subjects and compared it with patients with glaucoma. Additionally, the SaO2 was correlated with different variables affected by glaucoma. This is a prospective repeated-measures and case-cohort study. Participants were recruited at the Laurentian Eye Institute (IOL). They completed a complete eye exam under pupil dilation including a blood pressure measurement with an automated device and the pulse oximetry was obtained by a pulse oximeter (SpO2). The ocular oximetry measures was acquired by the Zilia imaging system on the temporal side of the optic nerve. No statistically significant differences were observed between the average of three SaO2 measurements at the optic nerve. For the duration of the acquisition, the data analysis showed a statistically significant difference between the 5 seconds acquisition compared to the other acquisition duration. There was no statistically significant difference between the average of the first measurement obtained before and after the use of the data optimization technique. The result showed a significant difference in the SaO2 values between glaucomatous participants and normal. We also see a correlation statistically significantly between the SaO2 values and the global RNFL. This study is one of the first one done with the Zilia device. The average value of SaO2 obtained at a specific point of the optic nerve acquired by the Zilia device are repeatable and a 10-second acquisition could provide a precise value. Also, the SaO2 measured with the Zilia imaging system on the optic nerve is significantly lower in glaucoma patients compared to normal patients. More studies are needed to really establish the role of that device in the diagnostic and fully up of patients with glaucoma.
Ocular oximetry Glaucoma Oxygen saturation Oxyhemoglobin