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An optical low-coherence reflectometer is used for rapid noncontact measurements of the human corneal thickness in vivo. Thickness measurements on ten volunteers show a standard deviation of 3.4 μm. The experiments reveal that the optical reflectometer benefits from a 2.5 fold enhancement of the measurement precision and a 2.8 fold reduction in measurement time compared to a standard clinical ultrasonic pachometer. © 1998 Society of Photo-Optical Instrumentation Engineers.

This study investigates the precision and intraindividual variability of a clinical optical pachometer based on low-coherence reflectometry, which was used to measure the central thickness of a human cornea in vivo. The instrument, attached to a slit lamp, is a single mode fiber optic based Michelson interferometer with a high repetition rate as previously described. The same operator performed ten sets of measurements on the same subject, each consisting of 20 consecutive scans, on each day for three consecutive days. By computing the means from every scan series, the thickness of the central cornea with optical pachometry was found to be 519.6±1.2 (range 518-521) μm on day 1, 519.9±0.9 (range 519-521) μm on day 2, and 523.8±0.6 (range 523-525) μm on day 3. The thickness values on day 3, where the subject suffered from a cold without clinical ocular involvement, were different from the two previous days (p<0.001, one way analysis of variance). Optical low-coherence reflectometry measurements of corneal thickness can be performed with high precision of about 1 μm and a high intra- and intersession reproducibility. © 1999 Society of Photo-Optical Instrumentation Engineers.

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Purpose To evaluate and compare axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and central corneal thickness (CCT) measurements assessed by optical biometry (OB), ultrasound biometry (UB), optical low coherence reflectometry pachymetry (OLCR‐P), and by a new prototype applying optical low coherence reflectometry biometry (OLCR‐B). Methods OLCR‐B (Haag‐Streit), OLCR‐P (optical low coherence reflectometry pachymetry; Haag‐Streit), OB (IOLMaster, Zeiss), and UB (Tomey AL‐3000) were performed in 35 eyes of 20 patients with incipient cataract. Among the patients were 13 women (age 60‐88) and 7 men (age 53‐90). There were no exclusion criteria. Bland‐Altman analysis was performed to investigate agreement of AL, ACD, LT and CCT measurements between the devices. Correlation between the techniques was also determined using linear regression. All measurements were performed according to the manufacturers recommendations. Results The mean AL was for OLCR‐B 24.35 mm ± 2.32 (SD), OB 24.33 mm ± 2.41, and UB 24.03 mm ± 2.27; the mean ACD for OLCR‐B 3.10 mm ± 0.51, OB 3.15 mm ± 0.52, and UB 3.09 mm ± 0.47; the mean LT for OLCR‐B 4.71 mm ± 0.42, and UB 4.73 mm ± 0.49; the mean CCT for OLCR‐B 543 mm ± 44, OLCR‐P 536 mm ± 32, and UB 541 mm ± 41. Bland‐Altman analysis and linear regression showed high correlation between the devices. Conclusion OLCR‐B, OLCR‐P, OB and UB give comparable results in patients with incipient cataract. The advantages of the OLCR‐B prototype are the non contact method, the exact measurement of AL, ACD, LT and CCT on the same interferometry method and hence the short duration of the measurements. Commercial interest