Purpose: To evaluate quantitative topographic parameters of the cornea and to define topographic cone patterns and pachymetry in a series of keratoconus patients.Methods: We prospectively evaluated topographic findings of 130 eyes of 73 patients using ORBSCAN corneal TOPOGRAPHY system. The location, anterior and posterior surface elevation, curvature, amount of astigmatism and pachymetry were analyzed with special reference to the central point of corneal, the apex and the thinnest point.Results: The mean age of patients was 27/31 years ± 9.30 (SD). Fifty seven patients (67.6%) had bilaterial and sixteen (12.3%) had unilateral keratoconus.Most cones (64.6%) were located in the inferior temporal quadrant. 32.3% of cones were restricted to the central cornea and 4 were above horizontal meridian. Maximum apex elevation was 68.9D. The mean elevation of the apex was (0.195±0.055) mm. The mean distance between the apex and central point was (0.697±327) mm.The mean thickest of thinnest point of cornea was 398pm (range 143-551pm).Conclusion: ORBSCAN can provide accurate and subtle information about the shape and thickness of keratoconus which can help for early diagnosis of this disease.ORBSCAN TOPOGRAPHY system may be helpful in identifying patients who are potentially at risk for developing ectasia after lasik.

Purpose: To evaluate agreement between Galilei, ORBSCAN II, and placido disk-based TOPOGRAPHY in terms of keratometry readings, and anterior and posterior elevation.Methods: In this prospective comparative study, 184 eyes of 92 keratorefractive surgery candidates were evaluated with Galilei, ORBSCAN II, and placido disk-based TOPOGRAPHY. Keratometry readings and anterior and posterior elevation maps were compared using ANOVA and paired t-test.Results: Mean keratometry reading by Galilei, ORBSCAN II and corneal TOPOGRAPHY was 44.30±1.49 D, 44.11±1.47 D, and 44.60±1.56 D, respectively. The maximum difference in SimK and astigmatism obtained three devices was less than 0.5 D with respect to the anterior and posterior best fitted sphere, the agreement between the Galilei and ORBSCAN II was 0.96 and 0.95, respectively. Maximum elevation of the anterior central cornea was 9.17±5.1 m by ORBSCAN II and 3.2±1.78 m by Galilei. Maximum depression of the posterior central cornea was 33.84±9.33 mm and 6.81±3.78m, respectively.Conclusion: Despite a significant difference in mean keratometry readings, the three devices can be used as the difference in measurements was not clinically significant. However a large amount difference was found between Galilei and ORBSCAN II interms of anterior and posterior maximum elevation values.

Background and Aim: The aim of this study was to determine the validity in central corneal thickness (CCT) and peripheral corneal thickness (PCT) measured by Scheimpflug imaging (Pentacam, Oculus) and scanning-slit TOPOGRAPHY (ORBSCAN II, Bausch & Lomb) using gold standard method of ultrasound (US) in Hyperopic eyes after LASEK surgery.Materials and Methods: This descriptive-analytic study carried out on hyperopic patients who underwent LASEK eye surgery in Farabi eye hospital in 2012 and collection of samples lasted 9 months.28 Hyperopic eyes who underwent LASEK eye surgery were inspected by ultrasound (US), Scheimpflug imaging (Pentacam, Oculus) and scanning-slit TOPOGRAPHY (ORBSCAN II, Bausch & Lomb). Statistical analysis of collected data was performed using SPSS software version 18 and paired t-test method.Results: CT and PCT were evaluated in 28 eyes. CCT measured by ORBSCAN II had good correlation with those measured by ultrasound pachymetry (r=0.083 and p<0.05). ORBSCAN II had good correlation in CCT measurement with those measured by Pentacam HR (p<0.05 and r=0.072). PCT measured by Pentacam HR had good correlation with those ultrasound pachymetry readings and there is no considerable discrepancy between two methods. ORBSCAN II had good correlation in superior, inferior and temporal corneal thickness but there was considerable discrepancy in nasal corneal thickness measured by ORBSCAN II with those of ultrasound pachymetry (sig=0.01, t=-2.74, p<0.05).Conclusion: Pentacam HR and ORBSCAN II showed good correlation with US in CCT measurement; however, in PCT measurement Pentacam HR had better correlation compared to ORBSCAN II in hyperopic patients after LASEK refractive surgery.

Purpose: To compare ORBSCAN II and ultrasonic pachymetry for measurement of central corneal thickness (CCT) in eyes scheduled for keratorefractive surgery.Methods: CCT was measured using ORBSCAN II (Bausch & Lomb, USA) and then by ultrasonic pachymetry (Tomey SP-3000, Tomey Ltd, Japan) in 100 eyes of 100 patients with no history of ocular surgery scheduled for excimer laser refractive surgery.Results: Mean CCT was 544.7±35.5 (range 453-637) mm by ultrasonic pachymetry versus 546.9±41.6 (range 435-648) mm measured by ORBSCAN II applying an acoustic factor of 0.92 (P=0.14). The standard deviation of measurements was greater with ORBSCAN pachymetry but the difference was not statistically significant.Conclusion: CCT measurements by ORBSCAN II (applying an acoustic factor) and by ultrasonic pachymetry are not significantly different; however, when CCT readings by ORBSCAN II are in the lower range, it is advisable to recheck the measurements using ultrasonic pachymetry.

Purpose: To compare central corneal thickness (GGT) readings measured by ORBSCAN II and Nidek Ultrasound Pachymeter (UP-1000) in healthy eyes and to evaluate the reliability coefficient of ORBSCAN II pachymetry.Methods: In 88 eyes of 44 subjects GGT was measured twice by ORBSCAN II and then by ultrasound. Sample rings of different diameters in the range of 0 mm to 3 mm were assigned to ORBSCAN II and measurements were recorded. before and after applying the manufacturer's suggested acoustic factor. A correction equation was calculated through regression analysis with which data were reanalyzed. To evaluate the relationship between the two devices, corneal thickness was compared using the 95% limits of agreement (LoA), The reliability coefficient of ORBSCAN II was assessed to determine the reproducibility of GGT measurements.Results: Mean CCT measured by ORBSCAN II and ultrasound was 578 (range, 527-656) and 560 (range, 507-630) microns (m m) with standard deviations of 29 and 31, respectively. Mean difference between the two series of measurements was 18.7±15.5 mm and the 95% LoA was -11.7 to 49.2 mm. After applying the calculated correction equation, the mean difference changed to 0.38±15.4 mm (95% LoA: -29.9 to +30.7 mm).The reliability coefficients of ORBSCAN II in different diameters assigned were consistently high and was 0.978 (P<0.001) for the 2-mm-diameter ring.Conclusion: The two devices should not be used interchangeably before a precise correction equation is achieved through studies with samples of greater numbers and ranges of GGT. ORBSCAN II can be the single non-contact device used in follow-up of patients with intact corneas regarding its reliability.

We express our sincere thanks to Dr. Bernardo and Dr. Rosa for their interest in our study and their letter on our work. [1] Bernardo and Rosa noted the significance of central corneal thickness (CCT) in virgin eyes and after photorefractive keratectomy (PRK), as evaluated by Pentacam HR (Scheimpflug imaging) and ORBSCAN II (scanning slit TOPOGRAPHY). They concluded that the difference between Pentacam and ORBSCAN in measuring corneal thickness is related to differences in the devices, rather than corneal changes induced by hyperopic PRK...

Background and Objective: Evaluating the agreement among various corneal imaging devices is crucial due to their varying technologies in diagnosing corneal parameters. This study aimed to assess the agreement of Advanced Corneal Explorer (ACE) with Pentacam and ORBSCAN in myopic individuals with healthy corneas. Methods: This descriptive-analytical study was conducted on 45 myopic individuals (25 women and 20 men; mean age=30.37±6.13 years) referring to Al-Zahra Ophthalmology Hospital in Zahedan, Iran, during 2023. Anterior segment imaging was performed using three devices: ACE, Pentacam, and ORBSCAN. Corneal parameters, including TOPOGRAPHY, tomography, and corneal aberrations, were examined. The intraclass correlation coefficient (ICC) and 95% limits of agreement (LoA) were used to evaluate the agreement of ACE data with the data obtained from the other two devices. Results: ACE exhibited good agreement with Pentacam for the mean power (ICC=0.97), maximum power (ICC=0.98), and minimum power of the anterior corneal surface (ICC=0.97) (P<0.05). Additionally, ACE exhibited good statistical agreement with ORBSCAN for the mean power of the anterior corneal surface due to an ICC of 0.98 (P<0.05). The ICC values for central corneal thickness and thinnest corneal thickness with the ACE and Pentacam devices were 0.99 and 0.95, respectively, indicating significant statistical agreement (P<0.05). White-to-white distance, pupil size, and corneal aberrations did not show good agreement among the three devices (ICC<0.75). Conclusion: TOPOGRAPHY values and corneal thickness measured with ACE showed good agreement with Pentacam; therefore, they can be used interchangeably. Other measured variables from ACE did not show good agreement with Pentacam and ORBSCAN and are not interchangeable.