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Matthias Bolz, Josef Pretzl, Nikolaus Luft, Michael Ring, SAVE study group; Diabetic macular edema type correlates with visual acuity and tissue integrity measured by transverse section OCT. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4696.
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© ARVO (1962-2015); The Authors (2016-present)
Tissues integrity measured by transverse section optical coherence tomography (OCT) in diabetic macular edema (DME) has been shown to correlate with retinal function. Aim of this study was to evaluate a new, standardized method to assess tissue integrity based on transverse section OCT analysis and correlate findings with retinal function based on a new grading protocol (SAVE) for clinically significant diabetic macular edema.
94 eyes of 67 patients with clinically significant DME were examined with 2 spectral domain OCT machines (Nidek RS-3000 Advance and Spectralis HRA and OCT by Heidelberg engineering) after assessing ETDRS visual acuity and performing fluorescence angiography. All cases were graded by a previously published grading protocol called SAVE whereas “S” stands for “subretinal fluid”, “A” for “area” (planimetric dimension), “V” for “vitreo-retinal abnormalities” and “E” for edema type (focal, non-focal, ischemic, degenerative). A standardized image post-processing method (MATLAB 2012a, The MathWorks) of the OCT transverse section images of both machines was used in order to measure the ratio between intra- and subretinal fluid and remaining tissue, referred to as tissue integrity (100 x remaining tissue/ total tissue).
There was a very good correlation between the SAVE edema subtypes (category E) and visual acuity (p values between 0.0004 and 0.006 for type 1 to 4). Accordingly mean tissue integrity in the central 2000µm was 90±3% in type 1, 81±20% in type 2, 67±16% in type 3 and 71±25% in type 4. There was a clear trend for a correlation between visual acuity and tissue integrity in edema types 1 to 3, only reaching statistical significance in SAVE edema type 2 (p=0.04). In edema type 4 (degenerative edema) there was even a negative correlation (Pearson=-0,55, p=0.26). There were no significant differences between the tissue integrity values assessed by the 2 OCT machines.<br />
Apart from describing the individual type and amount of alteration of DME, the SAVE grading protocol based on OCT and FA images reveals a correlation between retinal morphology and function. Tissue integrity based on OCT transverse section analysis seems to be a new clinically important parameter, above all in SAVE edema types 1, 2 and 3.
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