Northwestern University, Department of Biomedical Engineering, Evanston, Illinois 60208, USA.
J Biomed Opt. 2013 Jun;18(6):066003. doi: 10.1117/1.JBO.18.6.066003.
Retinal hemoglobin oxygen saturation (sO2) level is believed to be associated with the pathophysiology of several leading blinding diseases. Methods to properly measure retinal sO2 have been investigated for decades; however, the accuracy of retinal oximetry is still considered to be limited. The Monte Carlo simulation of photon transport in retina to examine how the accuracy of retinal oximetry is affected by local parameters is discussed. Fundus photography was simulated in a multilayer retinal model, in which a single vessel segment with 0.7 sO2 was embedded, at six optical wavelengths. Then, 200 million photons were traced in each simulation to ensure statistically stable results. The optical reflectance and energy deposit were recorded to measure sO2 using both the reflection method (existing retinal oximetry) and a new absorption method, photoacoustic ophthalmoscopy (PAOM). By varying the vessel diameter and melanin concentration in the retinal pigment epithelium, the relative error of sO2 measurement in the reflection method increased with increasing vessel diameter and melanin concentration; in comparison, the sO2 measurement was insensitive to these two parameters in PAOM. The results suggest that PAOM potentially can be a more accurate tool in quantifying retinal sO2.
视网膜血红蛋白氧饱和度（sO2）水平被认为与几种主要致盲疾病的病理生理学有关。几十年来，人们一直在研究适当测量视网膜 sO2 的方法；然而，视网膜血氧计的准确性仍被认为是有限的。本文通过对视网膜中光子传输的蒙特卡罗模拟，探讨了视网膜血氧计的准确性如何受到局部参数的影响。在一个多层视网膜模型中模拟眼底摄影，其中嵌入了一个具有 0.7 sO2 的单个血管段，在六个光学波长下进行。然后，在每个模拟中追踪 2 亿个光子，以确保结果具有统计学稳定性。记录光的反射率和能量沉积，以使用反射法（现有的视网膜血氧计）和新的吸收法（光声眼内窥镜检查）测量 sO2。通过改变血管直径和视网膜色素上皮中的黑色素浓度，反射法中 sO2 测量的相对误差随着血管直径和黑色素浓度的增加而增加；相比之下，PAOM 对这两个参数的 sO2 测量不敏感。结果表明，PAOM 可能是一种更准确的定量视网膜 sO2 的工具。
