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G.L. Trick, P.A. Edwards, U. Desai, B.A. Berkowitz; Spatial and Temporal Properties of the Retinal Oxygenation Response in Healthy Subjects and Patients With Diabetes . Invest. Ophthalmol. Vis. Sci. 2006;47(13):990.
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© ARVO (1962-2015); The Authors (2016-present)
To analyze the evolution of local changes in the human retinal oxygenation response (ROR) during hyperoxia in healthy subjects and patients with diabetes mellitus.
MRI was used to measure the ROR during 40 minutes of hyperoxia in 7 healthy subjects (age = 41.5 ± 10.4 years) and 10 patients with Type 1 diabetes mellitus (age = 36.7 ± 11.5 years) who had either background or no retinopathy. Subjects fixated a point source and refrained from blinking during a 15–s fast low–angle shot image. This sequence was repeated 20–40 times (5–10 min acquisition) and high resolution (390 x 390 µm2 in–plane) images extending 19.5 mm nasal and temporal to the optic disc were collected sequentially during 0–10 (post1), 10–20 (post2), 20–30 (post3) and 30–40 (post4) min of hyperoxia. ROR changes were measured from these images. For local analysis, data were averaged in clusters representing 0.39 by 1.17 mm sectors. Because all post1 changes were significant relative to room air breathing, we examined changes during hyperoxia by statistically comparing ROR in clusters obtained at 0–10 minutes (post 1) of hyperoxia to ROR in corresponding clusters obtained at later points in hyperoxia. The resulting maps illustrate the distribution and evolution of significant changes.
At post1, both groups exhibited increases (p < 0.05) in panretinal ROR. For post2 there was essentially no significant changes in healthy subjects but patients with diabetes exhibited ROR increases (p < 0.05) from 7.5 –16.0 mm nasal and 14.5 – 19.5 mm temporal to the optic disc. By post3, both groups exhibited ROR increases (p < 0.05) from 5 – 19.5 mm nasal to the optic disc while changes temporal to the optic disc were spatially scattered. By post4, the patients with diabetes exhibited ROR increases (p < 0.05) that extended from 1.5 – 19.5 mm nasal and temporal to the optic disc, while the ROR increases (p < 0.05) in the healthy subjects extended from 5 – 14 mm nasal and 12 – 18 mm temporal.
The results demonstrate a new analytic measure of the difference in ROR dynamics between healthy subjects and patients with Type 1 diabetes mellitus. During the initial phase of hyperoxia both groups exhibited ROR increases that were spatially similar. However, as the hyperoxia duration was prolonged the patients with diabetes exhibited earlier and more spatially contiguous increases in ROR. These findings demonstrate MRI measurement of ROR during hyperoxia provides a non–invasive, real–time index of local oxygenation dynamics.
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