Comparison of the ultrasonographic method with 2 partial coherence interferometry methods for intraocular lens power calculation.

BACKGROUND: The accuracy of biometric measurements, particularly axial length, is critical for precise intraocular lens (IOL) power calculation and predictable refractive outcomes after cataract surgery. Partial coherence interferometry-based systems represent progress toward measurements that are more precise and reliable. The purpose of this study was to evaluate a new noncontact optical biometer (Lenstar; Haag-Streit AG, Koeniz, Switzerland) using optical low-coherence reflectometry and to compare the biometric measurements (including axial length, keratometry, anterior chamber depth, and IOL power) with those obtained from current clinical instrumentation. METHODS: Biometric measurements were obtained with Lenstar, IOL Master V.5 (Carl Zeiss Meditec AG, Jena, Germany), and A-scan applanation ultrasound scan combined with a Javal-type keratometer in 234 eyes of 234 subjects scheduled for cataract surgery. IOL power was calculated using Sanders, Retzlaff, Kraff II, Hoffer Q, and Holladay 1 formulas. RESULTS: The axial length readings were similar (P = 0.997). The anterior chamber depth measurements obtained by IOL Master were slightly smaller than those obtained with other devices (P = 0.092). The means of the average keratometry readings were 0.65 and 0.61 diopters lower when measured with Lenstar as compared with IOL Master and the Javal-type keratometer, respectively (P = 0.002). All of the measurements were tightly correlated (P < 0.001). For anterior chamber depth measurements, however, the correlation was slightly weaker. Using the above-mentioned formulas, the mean IOL power measurements were similar. These measurements were tightly correlated (P < 0.001). The level of agreement was acceptable and comparable between devices. CONCLUSIONS: The findings from this study show the validity and clinical utility of Lenstar compared with instrumentation currently used in clinical practice for assessing ocular biometry and IOL power calculation in cataractous eyes.

Comparison of anterior chamber depth measurements using Galilei, HR Pentacam, and Orbscan II.

BACKGROUND: Anterior chamber depth measurement is used frequently in cataract and refractive surgery for advanced intraocular lens (IOL) power calculation formulas and implantation of phakic IOLs. In this article, we show agreement in anterior chamber depth measurements in normal eyes among 3 noncontact systems, namely Galilei, HR Pentacam, and Orbscan II. METHODS: The anterior chamber depth measurements were obtained with Galilei, HR Pentacam, and the Orbscan II in both eyes of 37 healthy subjects. Pearson's correlations were calculated, and mean anterior chamber depth measurements were compared. Bland-Altman plots were used to assess the difference between individual measurements for each patient. RESULTS: The mean anterior chamber depth readings (+/- standard error of means) with Galilei, Pentacam, and Orbscan were 3.22 +/- 0.05, 3.25 +/- 0.05, and 3.54 +/- 0.07, respectively. The difference between Galilei and Pentacam was not statistically significant (P = 0.013). However, Orbscan measurements were larger than those of either Galilei or Pentacam (P < 0.001). The differences between Orbscan and either Galilei or Pentacam were increased with greater anterior chamber depths. The 95% limits of agreement between Orbscan and Galilei, Orbscan and Pentacam, and Pentacam and Galilei in different ranges of chamber depth were ([ < 3 mm, -0.43 to +0.71 mm]; [3 to 3.5 mm, -0.23 to +0.83]; [ > 3.5 mm, +0.41 to +0.53]), ([ < 3 mm, -0.43 to +0.71 mm]; [3 to 3.5 mm, -0.26 to +0.80]; [ > 3.5 mm, +0.38 to +0.54]), and ([ < 3 mm, -0.05 to +0.06 mm]; [3 to 3.5 mm, -0.06 to +0.10]; [ > 3.5 mm, -0.11 to +0.12]), respectively. CONCLUSIONS: These data indicate that in the assessment of normal eyes, Orbscan gives consistently higher measurements for anterior chamber depth compared with Galilei and Pentacam. Because the differences between Orbscan and either Galilei or Pentacam were not within clinically acceptable levels, they are not interchangeable in every clinical situation. However, the differences among anterior chamber depth values measured with Galilei and Pentacam were within clinically acceptable levels. Thus, these 2 systems can be regarded as interchangeable.

Comparison of horizontal corneal diameter measurements using Galilei, EyeSys and Orbscan II systems.

BACKGROUND: White-to-white corneal measurement is used frequently in cataract and refractive surgery as well as in diagnosing various corneal diseases and monitoring congenital glaucoma. In this article, we determine agreement in horizontal corneal diameter measurements in normal eyes among the Galilei V4.01, the EyeSys and the Orbscan IIz. METHODS: In this prospective study, 37 consecutive volunteers were enrolled. All 74 eyes were measured with all three devices. Galilei, EyeSys and Orbscan II measurements were compared with one another. In addition, the data from the right and left eyes were compared for each device. RESULTS: The mean horizontal corneal diameter measurements with the Galilei, the EyeSys and the Orbscan II were 12.01 +/- 0.61 mm, 12.09 +/- 0.87 mm and 11.67 +/- 0.29 mm, respectively. The difference between the Galilei and EyeSys systems was not statistically significant (p = 0.76), however, the Orbscan II showed smaller measurements (p < 0.001). The best 95% limits of agreement between devices were for the Galilei and the Orbscan II (-0.72, 1.48; r = 0.4, p < 0.01). The best 95% limits of agreement between two eyes for each device were found with the Orbscan II (-0.15, 0.17; r = 0.996, p < 0.01). There was no correlation between measurements of right and left eyes for the Galilei or the EyeSys (r = 0.274, p = 0.176 and r = 0.31, p = 0.065, respectively). CONCLUSIONS: These results suggest that measurements made with the Orbscan II are smaller than those obtained with the EyeSys Corneal Analysis system and the Galilei. Among the three devices, the Galilei and the Orbscan II showed the best agreement, however, it is inadvisable to use the three devices interchangeably in every clinical situation.