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Reproducibility of Central Corneal Thickness Measurements in Normal Eyes Using the Zeiss Cirrus 5000 HD-OCT and Pentacam HR
摘要： Objectives: To determine the repeatability and reproducibility of Central Corneal Thickness (CCT) measurements using two different anterior segment imaging modalities, including those obtained with the new anterior segment lens attachments for the Cirrus 5000 HD-OCT. Methods: A total of 32 eyes from 16 normal volunteers (8 male, 8 female) were enrolled in this prospective study. CCT was measured by the same examiner using the Cirrus 5000 HD-OCT and Pentacam HR. The results of CCT obtained by each method were averaged and compared using t-test analysis. The agreement between the measurement methods was evaluated. Coefficient of Repeatability (CoR) and Intra-Class Correlation Coefficient (ICC) were computed. Results: The mean measurements taken with the Cirrus OCT anterior chamber lens (CCTAC), HD cornea lens (CCTHDC) and pachymetry scans (CCTPach) were 545.35 ± 31.02, 537.87 ± 26.82, and 532.04 ± 29.82 μm, respectively. The mean CCT obtained with the Pentacam (CCTPent) was 545.51 ± 30.71 μm. CCTPent were significantly higher than CCTHDC and CCTPach (p< 0.0001). In contrast, the CCTPent and CCTAC were similar (p=0.87). CCT, as evaluated by the two different instruments, showed excellent correlation (r > 0.98, p< 0.0001) with an ICC > 0.99 (95% CI, 0.97 – 0.99). CoR was the highest for CCTPach (3.7 ± 1.4, 95% CI (3.0- 4.6)). Conclusion: CCT measurements from the Cirrus OCT using the new anterior segment lens attachments and the Pentacam HR are highly correlated. This should allow the use of a standardized correction factor if necessary to inter-relate the measurements between the two devices.
关键词： Imaging,Central corneal thickness,Cornea,Optical coherency tomography,Scheimpflug technology,Pachymetry
更新于2025-09-23 15:21:01
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Diurnal variation of anterior segment parameters handled with Scheimpflug imaging in keratoconus patients
摘要： Purpose To define diurnal changes in anterior segment parameters of keratoconus patients by using Scheimpflug imaging. Methods All keratoconus patients had corneal topography measurements 3 times a day (around 09:00 AM, 13:00 PM and 17:00 PM) by the same experienced operator. Three consecutive scans in each measurement session were obtained. The average of three measurements was used for analysis. A repeated measures analysis of variance with one within-subject factor (time of day) was carried out to assess diurnal variation. Results This study included 26 eyes of 26 patients with keratoconus. Significant diurnal variation was found in CCT and TCT measurements (P < 0.01, and P < 0.01, respectively). The mean amplitudes of change in CCT and TCT were 4.2 ± 1 μm (95% CI: 1.7–6.8 μm) and 4.1 ± 1.1 μm (95% CI: 1.2–8.0 μm), while the mean of CCT and TCT were 462.4 ± 34.5 μm (95% CI: 448.4–476.6 μm) and 452.9 ± 6.6 μm (95% CI: 439.3–466.5 μm), respectively. The maximum value and the lowest value were observed at 09:00 AM and at 17:00 PM, respectively. Other parameters except CCT and TCT did not show diurnal variation. Conclusion Statistically significant but clinically insignificant diurnal variation in CCT and TCT measurements of the keratoconus patients were detected over an 8-hour period (09:00 AM–17:00 PM).
关键词： Diurnal variation,Keratoconus,Anterior segment,Scheimpflug imaging
更新于2025-09-23 15:19:57
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Accuracy of Scheimpflug-derived corneal biomechanical and tomographic indices for detecting subclinical and mild keratectasia in a South Asian population
摘要： To test the predictive accuracy of the Belin-Ambrósio deviation index (BAD-D), the stiffness parameter A1 (SPA1), the Corvis biomechanical index (CBI), and the tomographic and biomechanical index (TBI) assessments for distinguishing subclinical and mild keratoconic eyes from normal eyes.
关键词： Scheimpflug-derived corneal biomechanical and tomographic indices,subclinical keratectasia,South Asian population,mild keratectasia
更新于2025-09-23 15:19:57
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Scanning laser triangulation sensor geometry maintaining imaging condition
摘要： This work deals with the system design, control and the experimental results of a scanning laser sensor in which the optical path is scanned by a novel high performance compact fast steering mirror (FSM). The system design satisfies the Scheimpflug condition even though only the illumination path is scanned, such that an FSM with a small aperture size and high bandwidth can be used. To scan the area of interest with the FSM, raster trajectories are employed, which provide an uniform spatial resolution over the scan area. To track the trajectory a feedback controller is designed using the H-approach, such that a closed loop bandwidth of 1.4 kHz is achieved. The FSM can follow triangular signals up to 200 Hz with the maximum actuation range of ±3?. This enables a framerate of up to two frames per second for an image with 100x100 pixels. With the scanning system a maximum spatial resolution of 60 μm and a scan range of 25 mm can be achieved.
关键词： Optical Sensing and Sensors,Precision measurements,Laser Sensor,Fast Steering Mirror,Scheimpflug Condition,3D Sensor,Absolute measurement,System Design
更新于2025-09-16 10:30:52
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Comparison of Laser Platform Estimation and Objective Measurement of Maximum Ablation Depth Using Scheimpflug Pachymetry in Myopic Femtosecond Laser In Situ Keratomileusis
摘要： To compare the preoperative estimation of maximum ablation depth provided by the laser platform with objective measurement using Scheimpflug pachymetry in myopic femtosecond laser-assisted in situ keratomileusis (FS-LASIK). This is a prospective study carried out at the Rothschild Foundation, Paris, France. In 89 consecutive myopic eyes (45 patients) treated with FS-LASIK, the maximum ablation depth was calculated by measuring the difference between preoperative and 3-month postoperative measurements in central corneal thickness using Scheimpflug pachymetry (Pentacam HR; Oculus Optikger?te, Wetzlar, Germany). These values were compared with the preoperative estimation of the maximum ablation depth provided by the laser platform, without nomogram adjustment. We found a strong linear correlation between laser platform estimation of maximum ablation depth and Scheimpflug pachymetry (P , 0.00001). The mean ablation depth measured using Scheimpflug pachymetry was greater than that predicted by the laser platform, with a mean overall difference of 2.15 mm (P , 0.05). Subgroup analysis revealed a difference in ablation depth measurements of 7.1 mm in the high myopia subgroup, which was the only subgroup where the difference remained statistically significant. In myopic FS-LASIK, laser platform estimation of maximum ablation depth correlates well with measurement of maximum ablation depth using Scheimpflug pachymetry and therefore can be used safely.
关键词： LASIK,ablation depth,Pentacam,Scheimpflug pachymetry
更新于2025-09-12 10:27:22
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Direct and Indirect Flap Measurements in Femtosecond Laser–Assisted In Situ Keratomileusis
摘要： To compare direct and indirect LASIK flap thickness measurements using ultrasound and Scheimpflug technology. Eighty-two eyes treated with laser-assisted in situ keratomileusis refractive surgery using a femtosecond laser (IntraLase FS150) were prospectively included in the study. Flap thickness was set to 115 mm. Corneal flap thickness was measured using the direct method—ie, ultrasound pachymetry immediately after flap construction in the presence of cavitation bubbles—and indirect methods, with subtraction of intraoperative post-lift corneal thickness measured using ultrasound pachymetry (intrastroma) from preoperative central corneal thickness using ultrasound (Indirect-US) or Scheimpflug thinnest pachymetry (Indirect-Scheimpflug). Mean flap thickness was overestimated using the indirect methods, Indirect-US and Indirect-Scheimpflug (122.6 6 24.5 mm and 128.1 6 26.1 mm, respectively; P , 0.0060 and P , 0.0001, respectively). There were no significant correlations between the direct and indirect methods. Indirect-Scheimpflug was significantly higher (P = 0.0122) than Indirect-US. The closest average flap thickness compared with the set parameter of 115 mm was that of the direct method (115.6 6 8.6 mm; 95% confidence interval: 21.3 to 2.5; P = 0.5163). The direct method provided the lowest SD of all groups (SD: 8.64). The direct method of flap thickness measurement was the most comparable to the set parameter compared with the indirect subtraction methods. Additional studies are needed to determine which method allows for the most accurate measurement of flap thickness.
关键词： flap thickness,femtosecond laser,laser in situ keratomileusis,Scheimpflug,ultrasound
更新于2025-09-12 10:27:22
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Comparison of anterior segment changes after femtosecond laser LASIK and SMILE using a dual rotating Scheimpflug analyzer
摘要： Background: To compare the changes in the anterior segment after femtosecond laser in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE) using a dual rotating Scheimpflug (DRS) analyzer (Galilei?; Ziemer Ophthalmology, Port, Switzerland). Methods: A total of 218 eyes of 109 patients who underwent FS-LASIK or SMILE for myopic correction were retrospectively studied. Ninety-eight eyes of 49 patients who underwent FS-LASIK were compared to 120 eyes of 60 patients treated with SMILE. A DRS analyzer was used for preoperative and 6-month postoperative anterior segment analyses. Measured variables included the central corneal thickness (CCT), anterior chamber depth (ACD), anterior and posterior keratometry (K), anterior and posterior best-fit sphere radius, and maximum posterior elevation (MPE). Results: After the procedure, the amount of CCT decrease was higher in the SMILE group than in the FS-LASIK group, but it was not statistically significant. The MPE was significantly increased after both procedures (p < 0.001 and p = 0.001 in the FS-LASIK and SMILE groups, respectively), with the amount of elevation being higher after FS-LASIK than after SMILE even though it was not statistically significant. And there was a significant change in the steep and average posterior K in the FS-LASIK group (p = 0.006 and 0.001, respectively), but not in the SMILE group. Conclusions: Regarding changes in the MPE and posterior K, changes in the posterior corneal surface were greater after FS-LASIK than after SMILE.
关键词： Dual rotating Scheimpflug analyzer,LASIK,Galilei,Small incision lenticule extraction,FS-LASIK,SMILE
更新于2025-09-12 10:27:22
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Validation of the SToP formula for calculating intraocular lens power in eyes with previous myopic excimer laser surgery
摘要： To validate the accuracy of the SToP formula for calculating the intraocular lens (IOL) power from measurements obtained with a rotating Scheimpflug camera (Pentacam) in eyes with previous myopic excimer laser surgery.
关键词： myopic excimer laser surgery,Scheimpflug camera,Pentacam,intraocular lens power,SToP formula
更新于2025-09-12 10:27:22
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Tomographic analysis of anterior and posterior surgically induced astigmatism after 2.2?mm temporal clear corneal incisions in femtosecond laser–assisted cataract surgery
摘要： To evaluate surgically induced astigmatism (SIA) of temporal clear corneal incisions (CCIs) on anterior and posterior corneal curvature after femtosecond laser–assisted cataract surgery (FLACS) using Scheimpflug tomographic measurements.
关键词： clear corneal incisions,Scheimpflug tomography,femtosecond laser–assisted cataract surgery,surgically induced astigmatism
更新于2025-09-12 10:27:22
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Corneal topography and angle parameters after laser iridotomy combined with iridoplasty assessed by dual Scheimpflug analyzer
摘要： Purpose To investigate the changes in corneal topography including parameters such as corneal curvature and corneal aberrations, along with anterior chamber angle (ACA) after laser iridotomy (LI) combined with peripheral iridoplasty (PI) using dual Scheimpflug analyzer. Methods In this prospective observational study, dual Scheimpflug analyzer images were acquired before and 1 week after LI plus PI. Corneal curvature of both axial and instantaneous maps from anterior and posterior surface, respectively, and total corneal power (TCP) were acquired. These corneal parameters from three zones (central, middle, and peripheral) and total corneal wavefront aberration, trefoil, and coma were obtained. The ACA from four quadrants, anterior chamber depth (ACD), anterior chamber volume (ACV), and intraocular pressure (IOP) were also inspected. Results ACD increased from 2.15 ± 0.25 to 2.18 ± 0.24 mm (P = 0.002). ACV and ACA from all four quadrants increased significantly after the laser treatment (all P < 0.05). IOP decreased from 16.9 ± 3.1 to 14.7 ± 2.9 mmHg following LI plus PI (P = 0.000). No significant changes were detected in corneal axial and instantaneous curvature from three zones on the anterior and posterior corneal surface after LI plus PI (all P > 0.05). The TCP, total corneal wavefront aberration, trefoil, and coma also revealed no significant changes after the laser procedure (all P > 0.05). Conclusions Treatment with LI combined with PI did not affect the corneal topographic parameters from both anterior and posterior surfaces. However, LI plus PI significantly and effectively improved ACA parameters.
关键词： Anterior chamber angle,Laser iridoplasty,Dual Scheimpflug analyzer,Laser iridotomy,Primary angle closure
更新于2025-09-12 10:27:22