Purchase this article with an account.
Pang-yu Teng, Justin Wanek, Norman P Blair, Mahnaz Shahidi; A Method for Three-dimensional Mapping of Retinal Tissue Oxygen Tension in Rat. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2100.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The amount of oxygen available for energy production by the retina is determined by retinal tissue oxygen tension (tPO2). Retinal ischemia is often multifocal and may lead to localized regions of tissue hypoxia in diseases such as diabetic retinopathy and retinopathy of prematurity. Therefore, methods for mapping retinal tPO2 are needed for advancing knowledge of tissue oxygenation under these conditions. The purpose of the study was to demonstrate three-dimensional mapping of retinal tPO2 in rats under systemic normoxia and hypoxia.
Using our established optical section phosphorescence lifetime imaging system, depth-resolved retinal tPO2 images were acquired from closely spaced locations on the retina. These retinal tPO2 images were combined to reconstruct a three-dimensional retinal tPO2 volume, consisting of 40 enface retinal tPO2 maps, separated in depth and spanning from the vitreous to the choroid. Imaging was performed in 1 rat under normoxia and 1 rat under systemic hypoxia, respectively. The severity of hypoxia was evaluated with the use of z-score maps, generated for each retinal tPO2 map based on the mean and standard deviation (SD) obtained from the normoxic enface retinal tPO2 maps at corresponding retinal depths. Inner (tPO2_IR) and outer (tPO2_OR) retinal tPO2 volumes were compiled, consisting of enface maps from 1 to 20 and from 21 to 40, respectively.
Mean retinal tPO2 calculated from enface maps progressively increased with retinal depth, with the maximum value obtained near the choroid. Mean, SD, distribution peak, and 10th and 90th percentiles of both tPO2_IR and tPO2_OR volumes were lower under hypoxia as compared to normoxia (Table 1). Anoxic regions (PO2 ≤ 1 mmHg) were present in the retina under hypoxia, encompassing 7% and 1% of tPO2_IR and tPO2_OR volumes, respectively. Under systemic normoxia, z-scores < - 2 were present in 1% of tPO2_IR and tPO2_OR volumes. In contrast, under systemic hypoxia, z-scores < - 2 were observed in 40% and 25% of tPO2_IR and tPO2_OR volumes, respectively.
Three-dimensional mapping of retinal tPO2 was reported for the first time to our knowledge, demonstrating reduced tPO2 under systemic hypoxia. The presence of anoxia under hypoxic condition indicates regions of the retina had a severe loss of energy production. Retinal tPO2 mapping holds promise for investigating multifocal ischemia and tissue hypoxia due to retinal diseases.
This PDF is available to Subscribers Only