Optical Low Coherence Reflectometry (OLCR) versus Ultrasound Pachymetry (US): Comparison of Precision in 120 human Eyes
Lackerbauer C.-A., Kojetinsky C., Grueterich M., Kampik A., Ludwig K.
Department of Ophthalmolgy, Ludwig-Maximilians-University, Munich
Purpose: To investigate the precision of corneal pachymetry, an important focus in Excimerlaser refractive surgery. A new "non-contact" method based on OLCR could have beneficial effects compared to standard US-pachymetry.
Method: Corneal thickness was measured in 120 eyes (60 volunteers) with an OLCR prototype, integrated in the Allegretto-Excimerlaser system, Wavelight Laser Technologies AG, Erlangen, Germany, and with an US-pachymetry system SP 2000, Tomey, Erlangen, Germany. Measurements were performed by one investigator, each consisting of 10 consecutive scans. Results were considered statistically (paired t-test, p<0.05). In addition, corneal thickness measurements of both methods were proven by two independent investigators in further 20 cases. Results were correlated (spearman rank correlation; rho).
Results: Corneal thickness could be measured with OLCR in 115 cases., while US-pachymetry could be performed in all human eyes without problems. Mean corneal thickness was 541.3 µm±31.7 µm (range 414.6 µm-608.5 µm) with OLCR, respective standard error of the single scans 1.5 µm. With US-pachymetry mean corneal thickness was 533.1µm±31.8 µm (range 410.2 µm-599.1 µm), respective standard error of the single scans 3.3 µm (p<0.0001). Interreader-correlation was high for both methods (OLCRrho:0.962; USrho:
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