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Samia Fatum, Magdalena Sinczak, Amun Sachdev, Victor Chong; Comparing Optos OTI and Heidelberg Spectralis SD-OCT in Patients with Diabetic Macular Edema. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5870. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Heidelberg Spectralis Spectral Domain Optical Coherent Topography (SD-OCT) is often considered the current gold standard of SD-OCT. However, it does not have the ability to measure retinal function. In a previous study, microperimetry points from another machine were overlaid onto to the SD-OCT scan. As the optics of the machines is different, it was not clear whether the point to point correlation was correct. The Optos OTI has the microperimetry in the same machine, allowing point to point co-localisation. In this study we compared the measurements of these two machines in patients with diabetic macular edema (DME).
Patients with early DME were recruited in this study. Best corrected visual acuity (BCVA) was measured by letter counting with ETDRS chart. SD-OCT was measured by Spectralis and OTI in the same setting, one after the other. The central subfield and the parafoveal subfield (3mm) were analysed and compared between the two machines. The statistical analysis was calculated with SPSS.
There were 62 eyes included in the study. The mean age was 58.1 years, the mean BCVA was 77.2 letters, and the mean retinal thicknesses as measured by Spectralis were 310, 343, 344, 332, and 340 microns in the central, superior, temporal, inferior and nasal sub-field respectively, while the mean retinal thicknesses as measured by OTI were 237, 298, 297, 289, 290 microns in the central, superior, temporal, inferior and nasal sub-field respectively. The correlation of the two machines was highly significant in all five subfields (p<0.0001). The Pearson Correlations were 0.752, 0.85, 0.928, 0.839, and 0.823 in the central, superior, temporal, inferior and nasal sub-field respectively.
Although the absolute measurements of the two machines are significantly different, the correlation is over 75% in all sub-fields. This suggests that while it is not possible to transfer absolute measurements from one machine to the other, the OTI machine can be used for OCT measurements in patients with early DME requiring microperimetry assessment. Further studies are needed to identify the reason for these differences, which might allow us to have an even better correlation between the two machines.
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