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Laurence Shen Lim, Xian Hui Lim, Licia Tan; Influence of refractive error and axial length on retinal vessel oxygen saturation. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2157.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the relationships between refractive error, axial length, and retinal vascular oxygen saturation in an adult population.
This was a prospective observational study. Phakic adult subjects without media opacity were recruited from a general ophthalmology clinic. Subjective refraction was used to determine the spherical equivalent refraction (SE) and ocular biometry (IOLMaster V3.01, Carl Zeiss; Meditec AG Jena, Germany) was performed. Refractive errors were defined as myopia (SE < -1D), emmetropia (SE between -1D and +1D) and hyperopia (SE > +1D). Retinal oximetry was performed using the Oxymap system (Oxymap Inc., Reykjavik, Iceland) to measure mean retinal arteriolar and venular oxygen saturation. The mean arterial-venous difference (AVD) was calculated as the difference between the mean arteriolar and venular saturations. Multivariate analyses were performed to assess the relationships between retinal arteriolar and venular oxygen saturation and the AVD, and SE, axial length (AL) and refractive error, with adjustments for age, sex, race, blood pressure, hyperlipidemia, and diabetes mellitus. The left eye was used for all analyses.
There were 85 subjects in total, with a mean age of 66.1±11.3 years. The majority were female (60%) and Chinese (84%). The mean SE was -5.29±6.51D (range -25.0D to +2.5D) and the mean AL was 25.30±2.99mm (range 21.14 - 34.45mm). SE and AL were strongly correlated (Pearson correlation coefficient r = -0.88, p<0.001). The majority were myopic (60%), followed by emmetropic (28%) and hyperopic (12%). In multivariate analyses, more myopic SE and longer AL were associated with lower mean retinal arteriolar oxygen saturation [regression coefficient B = 0.61 (95% confidence interval (CI) 0.28, 0.95), p= 0.001; and B = -1.13 (95%CI -1.71, -0.56), p<0.001, respectively). Subjects with myopia had lower mean retinal arteriolar oxygen saturation, compared to emmetropic and hyperopic subjects (p = 0.03). There were no associations between SE, AL or refractive error, and venular oxygen saturation or AVD.
Eyes with more myopic refractive errors and longer AL have lower retinal arteriolar oxygen saturation. Reduced retinal oxygenation may contribute to the development of the pathological changes seen in high myopia.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Figure. Scatterplot of retinal arteriolar oxygen saturation versus axial length showing lower saturation with increasing axial length
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