Retinal Vascular Oxygen Saturation and Its Variation With Refractive Error and Axial Length

Abstract

Purpose: To evaluate the relationships between refractive error, axial length (AL), and retinal vascular oxygen saturation in an adult population. Methods: This was a hospital-based, prospective observational study. The left eyes of phakic adult subjects without media opacity were analyzed. Subjective undilated manifest refraction was performed, and refractive errors were defined as myopia (spherical equivalent [SE], ,À1 D), emmetropia (SE between À1 D and þ1 D) and hyperopia (SE .þ1 D). Retinal oximetry was performed using the Oxymap system (Oxymap Inc., Reykjavik, Iceland). Multivariate linear regression models were constructed to assess the relationship between retinal vascular oxygen saturation, SE, and AL obtained with optical biometry, with adjustments for age, sex, race, blood pressure, hyperlipidemia, and diabetes mellitus. Results: There were 85 subjects, with mean age of 66.1 6 11.3 years. The majority were female (60%) and Chinese (84%). A total of 60% were myopic, 28% emmetropic, and 12% hyperopic. Mean SE was À5.29 6 6.51 D and mean AL was 25.30 6 2.99 mm. In multivariate analyses, more myopic SE and longer AL were associated with lower retinal arteriolar oxygen saturation (regression coefficient B ¼ 0.61 [95% confidence interval, 0.28, 0.95], P ¼ 0.001; and B ¼ À1.13 [95% confidence interval, À1.71, À0.56], P , 0.001, respectively). Subjects with myopic SE and AL also had lower retinal arteriolar oxygen saturation than emmetropes and hyperopes (P ¼ 0.03 and P ¼ 0.02, respectively). Conclusions: Eyes with more myopic SE and longer AL have lower retinal arteriolar oxygen saturation. Translational Relevance: This study provides direct evidence of a link between retinal oxygenation and hypoxia and myopia by using a novel device that quantifies retinal vascular oxygenation in vivo.

Retinal glial cells under hypoxia possibly function in mammalian myopia by responding to mechanical stimuli, affecting hormone metabolism and peptide secretion

“…They function mainly in the cytoplasm where they bind to protein and have roles in the regulation of localisation, cellular response to stimuli, and regulation of multicellular organismal processes. saturation, can be examined [5,6,21,22] . Studies have reported that choroid thickness tends to decrease in myopic patients [7] and in experimentally induced myopia [23] .…”

“…With the development of optical coherence tomography technology, ophthalmologists and scientists can examine a larger area of ocular vessels, especially retinal and choroid vessels. The horizontal and vertical axes, as well as morphology and vascular oxygen saturation, can be examined [5, 6, 21, 22] . Studies have reported that choroid thickness tends to decrease in myopic patients [7] and in experimentally induced myopia [23] .…”

“…Scleral expansion whereby the ocular axis becomes longer is commonly considered a consequence of myopia [4] . During the process, retinal and choroid vessel changes have been observed where not only the density is altered, but also the blood flow and oxygen content [5][6][7] .…”

Retinal Vessel Oxygen Saturation Measurement Protocols and Their Agreement

“…Requiring only a dilated pupil to obtain a measurement, this technology has been implemented into clinical research examining patients with diabetes mellitus, cardiovascular disease, glaucoma, and high myopia. [6][7][8] The findings of these studies have provided a valuable insight into the retinal oxygen metabolism showing how oxygen consumption is reduced in patients suffering from glaucoma 9 and with increasing stages of DR. 10 Other studies have shown a change in oxygen parameters depending on visual field loss in glaucoma 4 and in hereditary conditions, including retinitis pigmentosa with characteristic loss of photoreceptors. 11,12 As with any novel technique, which is aimed at clinical testing, it is paramount to have a robust protocol that has a low test-retest variability and high specificity and sensitivity.…”

Retinal oxygen delivery and extraction in ophthalmologically healthy subjects with different blood pressure status

“…6. 31,33,41 For each vessel segment, we implemented linear compensations by means of a backward regression model, with ODR serving as the dependent variable and the independent variables being potential confounders, i.e., laterality, optic disc area, spherical error, cylinder, vessel diameter, and quadrant pigmentation index (PI). Only the significant variables of the reduced (final) model were subsequently used to construct the following correction formula:…”