Comparison and evaluation of ocular biometry using a new noncontact optical low-coherence reflectometer.

PURPOSE: To evaluate a new high-resolution noncontact biometer (Lenstar; Haag-Streit AG, Koeniz, Switzerland) using optical low-coherence reflectometry and to compare the clinical measurements with those obtained from the IOLMaster (Carl Zeiss, Jena, Germany) and the Pachmumeter (Haag-Streit AG). DESIGN: Exploratory evaluation of diagnostic technology and nonrandomized, prospective clinical trial. PARTICIPANTS: Eighty subjects (144 eyes) aged 20 to 90 years with cataractous, pseudophakic, aphakic, silicon oil-filled, or normal eyes. METHODS: Measurements of axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT), corneal radius (R1 [flattest radius of corneal curvature] and R2 [steep radius, 90 degrees apart from R1]), and axis of the flattest radius (Ax1) obtained with the Lenstar were compared with those obtained with the IOLMaster or Pachmumeter. The results were evaluated using Bland-Altman analyses. The differences between both methods were assessed using the paired t test, and its correlation was evaluated by Pearson coefficient. MAIN OUTCOME MEASURES: Axial length, CCT, ACD, R1, R2, and Ax1. RESULTS: The overall mean AL measured with the Lenstar and the IOLMaster was 24.1 mm (r = 0.999). Anterior chamber depth was 3.19 mm (Lenstar) and 3.17 mm (IOLMaster; r = 0.875). Excellent correlations also were found for the corneal radius and the axis of flattest radius (R1, r = 0.927; R2, r = 0.929; and Ax1, r = 0.938). Mean CCT was 0.557 mm (r = 0.978) for both Lenstar and Pachmumeter. CONCLUSIONS: Measurements with the new Lenstar correlated well with those with the IOLMaster and Pachmumeter in cataractous, pseudophakic, aphakic, silicon oil-filled, and normal eyes. It is an accurate, fast instrument that provides additional information of interest to any cataract or refractive surgeon.

Optical low coherence reflectometry for noncontact measurements of flap thickness during laser in situ keratomileusis.

OBJECTIVE: There is growing evidence that iatrogenic keratectasia after laser in situ keratomileusis (LASIK) for high corrections occurs more frequently than initially assumed, and that it may result from larger variation in flap thickness. DESIGN: Consecutive noncomparative case series PARTICIPANTS: Thirty-four patients who underwent LASIK for myopia and astigmatism (first treatment group) and 10 patients who received re-LASIK (retreatment group). METHODS: Central corneal thickness and thickness of the lamella during LASIK were determined by optical low coherence reflectometry (OLCR) and contact ultrasound pachymetry. MAIN OUTCOME MEASURES: Thickness of the flap and its standard deviation, as well as its correlation with age, sphere, cylinder, corneal thickness, intraocular pressure, and corneal refractive power (K-readings). RESULTS: The mean flap thickness of the first treatment group determined by OLCR was 130 +/- 29 microm; the 95 percentile was 169 microm and the 5 percentile was 86 microm. The flap thickness was not correlated with any of the investigated demographic or refractive parameters. The mean flap thickness of the retreatment group was 152 +/- 14 microm; the 95 percentile was 175 microm and the 5 percentile was 137 microm. Thus, the flap thickness of the retreatment group was significantly thicker compared with the first treatment group (P < 0.001). CONCLUSIONS: Optical low coherence reflectometry (OLCR) was shown to be an appropriate alternative to ultrasonic preoperative and intraoperative corneal pachymetry in laser assisted in situ keratomileusis. The lack of correlation between achieved flap thickness and preoperative clinical data, such as corneal thickness, corneal curvature, intraocular pressure, and refraction, emphasizes the importance of measuring flap thickness and corneal bed thickness during surgery.