[Bruch's Membrane Opening in OCT in Correlation with Corneal Correction - a Pilot Study]

Background: The measurement by optical coherence tomography (OCT) of the Bruch membrane opening (BMO) and the thinnest retinal fiber nerve layer in relation to it (BMO-MRW) has been performed in clinical routine since 2014. To compensate for astigmatism, or increased or decreased corneal power, a correction is performed through the mean K-value of the measured eye. The aim of this study was to measure the value of this correction and its influence on the measurement results. Methods: The sectors of BMO-MRW and BMO values of the five right eyes of five healthy patients were measured five times each with Heidelberg Spectralis OCT. Corneal compensation was systematically raised with each single measurement (7.1, 7.4, 7.7, 8.0, 8.3 mm).

The data showed almost linear dependence on the given corneal compensation values, with intraindividual variability. For the BMO-MRW, only small effects of compensation were found (0.85 up to 1.97 % per K-value difference of 0.3 mm). For BMO, the effect was greater, with a mean change of 7.71 % for every 0.3 mm change in compensation. Conclusion: For BMO-MRW, corneal compensation is of low clinical relevance. BMO is more dependent on this correction. In follow-up measurements, the compensation might not account for significant changes, although we recommend using correct corneal compensation values when obtaining single or first-time measurements.