Utility of the Swept Source Optical Coherence Tomography for Measurements of Central Corneal Thickness

PURPOSE: To evaluate the efficacy of swept source optical coherence tomography (SS-OCT) by comparing the measurement of central corneal thickness (CCT) to the measurement obtained using Orbscan II, anterior segment optical coherence tomography (AS-OCT) and ultrasound pachymetry. METHODS: One examiner measured the CCT in 65 eyes of 65 healthy subjects using Orbscan II, AS-OCT, SS-OCT and ultrasound pachymetry. The mean values and correlations were analyzed. RESULTS: The average CCT measurements obtained using Orbscan II, AS-OCT, SS-OCT and ultrasound pachymetry were 534.83 ± 38.46, 517.80 ± 32.48, 528.22 ± 33.71 and 528.02 ± 34.90 µm, respectively. A significant linear correlation was observed among Orbscan II, AS-OCT, SS-OCT and ultrasound pachymetry (r > 0.894, p < 0.001). There was no significant difference between the SS-OCT and ultrasound pachymetry (p = 0.782). CONCLUSIONS: The results of the 4 methods were significantly correlated and the SS-OCT reached a high level of agreement when CCT was determined using ultrasound pachymetry. The CCT measurements using SS-OCT is a better alternative for ultrasound pachymetry than Orbscan II and AS-OCT.

Comparison of Colvardpupillometer, ORBScan II and Sirius in Determining Pupil Size for Refractive Surgery

PURPOSE: To compare pupil size measured by Colvard(R)pupillometer, ORBScan II(R), Sirius(R) and analyze correlation between pupil size and night vision disturbance after refractive surgery according to measuring methods. METHODS: Two hundred eyes of one hundred patients who underwent refractive surgery were retrospectively evaluated. Pupil size was measured with Colvard(R)pupillometer, Sirius(R) in the scotopic light condition and with ORBScan II(R), Sirius(R) in the photopic light condition. Patients filled out questionnaire about night vision disturbance at postoperative three months. Correlation between pupil size according to measuring methods and night vision disturbance was evaluated. RESULTS: The mean age of patient was 26 years and number of male patients was 36. In scotopic light condition, pupil size measured with Colvard(R)pupillometer (6.76 mm) was significantly larger than that of Sirius(R) (6.53 mm) (p < 0.001). In photopic light condition, pupil size measured with ORBScan II(R) (3.98 mm) was significantly smaller than that of Sirius(R) (4.41 mm) (p < 0.001). Night vision disturbance were correlated with pupil size and Sirius(R) in the scotopic light condition had strongest correlation among three measuring method (r = 0.44). CONCLUSIONS: Sirius(R) tends to measure pupil size smaller than Colvard(R)pupillometer in the scotopic light condition. The correlation between night vision disturbance and pupil size was highest in Sirius(R).

Comparison of Anterior Chamber Depth Obtained from Applanation and Optical Principle Devices

PURPOSE: To assess the reproducibility and reliability of applanation A-scan ultrasonography (Pacscan 300A, Sonomed Inc., Chicago, IL, USA) and optical measurements with IOL Master(R) (Carl Zeiss Meditec, Germany), Pentacam(R) (Oculus, Wetzlar, Germany), and Orbscan II(R) (Orbtek Inc., Laredo, TX, USA) when measuring anterior chamber depth (ACD). METHODS: In this study of 188 eyes of 94 patients, ACD estimation prior to cataract surgery was preformed by the applanation A-scan method and IOL Master(R), Pentacam(R), and Orbscan II(R) optical methods. Repeatability from each device was evaluated by coefficient of variation, standard deviation, and intraclass correlation coefficient. RM-ANOVA on Ranks was used to compare the differences in ACD among the devices. The Bland-Altman plot was performed to assess agreement in measurements between the devices. RESULTS: The mean ACD according to the applanation A-scan method and IOL Master(R), Pentacam(R), and Orbscan II(R) optical methods were 2.89 +/- 0.49 mm, 3.25 +/- 0.45 mm, 3.21 +/- 0.46 mm, and 3.19 +/- 0.47 mm, respectively, and the differences were statistically significant (p < 0.01). The coefficient of variation for the 4 methods was 2.50% in the A-scan, 0.87% in the IOL Master(R), 1.25% in the Pentacam(R), and 1.04% with Orbscan II(R), and reproducibility was higher with the optical principle devices. The correlation coefficient between A-scan and IOL Master(R) was 0.65, between IOL Master(R) and Pentacam(R) 0.91, between IOL Master(R) and Orbscan II(R) 0.90, between A-scan and Pentacam(R) 0.69, between A-scan and Orbscan II(R) 0.71, and between Pentacam(R) and Orbscan II(R) 0.93. CONCLUSIONS: Applanation A-scan provided lower measurements for ACD compared with IOL Master(R), Pentacam(R) and Orbscan II(R). There was good agreement between results obtained with the latter 3 methods, and reproducibility was high with optical measurements. The coefficient of variation was low for IOL Master(R).

Posterior Corneal Curvature Assessment after Epi-LASIK for Myopia: Comparison of Orbscan II and Pentacam Imaging

PURPOSE: To compare the changes in posterior corneal curvature using scanning slit topography (Orbscan II) and Scheimpflug imaging (Pentacam) before and after Epi-laser in situ keratomileusis (LASIK) for myopia. METHODS: In a prospective observational case-series study, 20 myopic patients having undergone Epi-LASIK were examined serially with two different devices, Orbscan II and Pentacam, preoperatively and one month postoperatively. Posterior central elevation (PCE) and posterior maximal elevation (PME) were compared between the two devices, and the changes in parameters after Epi-LASIK were analyzed using a difference map. RESULTS: All parameters (preoperative and postoperative PCE and preoperative and postoperative PME) that were measured using the Orbscan II were significantly greater compared to those of the Pentacam (for all p < 0.001). PCE and PME were significantly increased one month postoperatively in the Orbscan II measurements (p < 0.05) but were not significantly increased in the Pentacam measurements. Also, DeltaPCE and DeltaPME, in the difference map obtained by each serial scanning, were significantly greater in the Orbscan II measurements than with the Pentacam (p = 0.012, p = 0.016). CONCLUSIONS: The Pentacam measurements displayed significantly reduced values in all parameters related to posterior corneal elevation compared to those of the Orbscan II. The Pentacam showed no significant change in posterior corneal curvature after Epi-LASIK, based on the difference map.

Corneal topography and hyperopia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To evaluate Orbscan II corneal topography in hyperopic cases.METHODS: A retrospective, observational, consecutive, clinical case series in two hundred and ninety five eyes of hyperopic patients who undergo a LASIK evaluation. The information that was reviewed included age and sex of the patients and the Orbscan II corneal topographic maps. Refractive powers and the following test indices produced by Orbscan II were analyzed: keratometry, corneal diameter, pupil diameter and anterior chamber depth. RESULTS: The total mean corneal thickness was 546.3±35.5μm.It was found ; 547.3±38.4μm in 17-29 years old, 553.4±38.3μm in 30-44 years old and 546.2±29.3μm in older than 45 years old .The mean corneal thickness was found 551.5±35.9μm in female, and 542.6±34.7μm in male. The total mean depth of anterior chamber was 2.57±0.40mm and in 17-29 years old patients was 2.82±0.39mm. In 30-44 years old patients was 2.49±0.39mm and in patients older than 45 years old was 2.37±0.40mm. The mean depth of anterior chamber was 2.53±0.40mm in female and 2.60±0.40mm in male. A reverse significant relation between corneal thickness and keratometry were found. Refractive error severity had a reverse correlation with depth of anterior chamber and a correlation with keratometry (P=0.061,r=0.108).Corneal thickness had a reverse correlation with keratometry (P=0.005,r=0.160), and correlation with pupil diameter (P=0.013, r=0.144).CONCLUSION: This study provides a description and analysis of Orbscan II findings in hyperopic patients. These show mean corneal thickness 546.3±35.5μm and anterior chamber depth 2.57±0.40mm in hyperopic patients.

Agreement of Actual Corneal Power and Corneal Power Using Topography in Cataract Patients Undergone Refractive Surgery

PURPOSE: To evaluate the agreement between actual corneal power and corneal power using Orbscan II of cataract patients who have undergone refractive surgery. METHODS: We retrospectively evaluated 18 eyes of 14 patients who underwent cataract surgery after refractive surgery. IOL power was targeted for emmetropia retrospectively using the manifest refraction two months after cataract surgery with SRK ll or SRK-T. We evaluated the agreement between actual corneal power and corneal power using 1 mm, 2 mm, 3 mm and 4 mm zone of Orbscan II TOP maps. RESULTS: The actual corneal power of cataract patients who underwent refractive surgery and 1 mm, 2 mm, 3 mm and 4 mm zone of Orbscan II TOP maps shows high agreement. When using a corneal power of 1 mm, 2 mm, 3 mm and 4 mm zone of Orbscan II TOP map, the following estimated refractive powers were observed at a 1 mm zone 0.21+/-0.69D, 2 mm zone 0.14+/-0.70D, 3 mm zone 0.25+/-0.95D and 4 mm zone 0.65+/-0.92D. CONCLUSIONS: The actual corneal power of cataract patients who have undergone refractive surgery and 1 mm, 2 mm, 3 mm and 4 mm zone of Orbscan II TOP maps show high agreement. We recommend selecting a corneal power corresponding to 1 mm or 2 mm zone of Orbscan II TOP maps to avoid hyperopia after cataract surgery.

Agreement of Actual Corneal Power and Corneal Power Using Topography in Cataract Patients Undergone Refractive Surgery

PURPOSE: To evaluate the agreement between actual corneal power and corneal power using Orbscan II of cataract patients who have undergone refractive surgery. METHODS: We retrospectively evaluated 18 eyes of 14 patients who underwent cataract surgery after refractive surgery. IOL power was targeted for emmetropia retrospectively using the manifest refraction two months after cataract surgery with SRK ll or SRK-T. We evaluated the agreement between actual corneal power and corneal power using 1 mm, 2 mm, 3 mm and 4 mm zone of Orbscan II TOP maps. RESULTS: The actual corneal power of cataract patients who underwent refractive surgery and 1 mm, 2 mm, 3 mm and 4 mm zone of Orbscan II TOP maps shows high agreement. When using a corneal power of 1 mm, 2 mm, 3 mm and 4 mm zone of Orbscan II TOP map, the following estimated refractive powers were observed at a 1 mm zone 0.21+/-0.69D, 2 mm zone 0.14+/-0.70D, 3 mm zone 0.25+/-0.95D and 4 mm zone 0.65+/-0.92D. CONCLUSIONS: The actual corneal power of cataract patients who have undergone refractive surgery and 1 mm, 2 mm, 3 mm and 4 mm zone of Orbscan II TOP maps show high agreement. We recommend selecting a corneal power corresponding to 1 mm or 2 mm zone of Orbscan II TOP maps to avoid hyperopia after cataract surgery.

Corneal Topographic Study Using Orbscan II between Keratoconus and Keratoconus Suspect

PURPOSE: To compare corneal topographic changes using Orbscn II between keratoconus and keratoconus- suspected eyes. METHODS: Thirty-seven keratoconus eyes, 17 keratoconus-suspected eyes and 37 normal eyes were evaluated by using Orbscan II corneal topography. We compared central phachymetry, anterior elevation from best-fit sphere (BFS), posterior elevation from BFS, most protruded corneal thickness, central corneal thickness, anterior chamber depth, corneal diameter, and pupil size. RESULTS: Central pachymetry, anterior and posterior elevation from BFS, central corneal thickness, and anterior chamber depth were statistically significantly different between keratoconus and control eyes. Anterior elevation from BFS showed a significant difference between keratoconus-suspected and control eyes. There were statistically significant differences in central pachymetry, posterior elevation from BFS, central corneal thickness and most protruded corneal thickness between keratoconus and keratoconus-suspected eyes. Corneal diameter and pupil size showed no differences among the 3 groups. CONCLUSIONS: Suspected keratoconus eyes have a higher value of anterior elevation from BFS on Orbscan II topography as compared with control eyes. Central pachymetry, posterior elevation from BFS, central corneal thickness and most protruded corneal thickness may be helpful in distinguishing between keratoconus and keratoconus-suspected eyes.

Intraocular Lens Power Calculation in High Myopic Eyes with Previous Radial Keratotomy

PURPOSE: To elucidate a proper method of intraocular lens (IOL) power calculation in highly myopic eyes with previous radial keratotomy (RK). METHODS: Five post-RK-surgery eyes with pre-RK-surgery myopia over -10.0 diopters (D) were studied retrospectively. The keratometric values obtained via the clinical history method, the contact lens over-refraction method, conventional keratometry, and Orbscan II were compared to the true keratometric value calculated retrospectively using the SRK/T formula. RESULTS: The mean pre-RK-surgery refractive power was -19.35+/-5.86D (-14.50 ~ -29.50D) and cataract surgery was performed on average 16.6 years after RK. The true keratometric value was closest to that estimated by the contact lens over-refraction method in 1 eye and to the flatter keratometric value between Sim K and the 3mm zone mean Pwr obtained with axial keratometric power map of Orbscan II in 4. CONCLUSIONS: The flatter keratometric value between Sim K and the 3mm zone mean Pwr from Orbscan II was closest to the true post-RK-surgery keratometric value of the central cornea.

Relationship between Clinical History Method and Orbscan II for Measuring Corneal Power after LASIK

PURPOSE: To evaluate the relation between clinical history method and Orbscan II for corneal power measurement after laser in situ keratomileusis (LASIK). METHODS: A total of 77 consecutive eyes of 43 patients who were treated with LASIK for myopia were followed up for at least 6 months. Corneal power by clinical history methods (CK) was compared with 3.0 mm zones of simulated keratometry (Sim-K), with 0.5, 1.0, 1.5, 2.0 and 3.0 mm zones of axial power maps (AP) and with 2.0, 3.0, 3.5, 4.0 and 5.0 mm zones of total optical power maps (TOP). RESULTS: Sim-K and all AP-map zones using Orbscan II were significantly higher (P<.001) than the CK value, while all TOP-map zones were significantly lower (P<.001) than the CK value. Among them, 3.0 and 4.0 mm TOP-map zones showed the highest correlation with the corneal power by CK (r2=0.889, P<.001; r2=0.889, P<.001). The correlation was higher with 3.0 mm TOP-map zone (r2=0.800, P<.001) than with 4.0 mm TOP-map zone (r2=0.793, P<.001) in high myopia patients. CONCLUSIONS: Although 3.0 and 4.0 mm TOP-map zones of Orbscan II were correlated highly with the CK value, these correlations were relatively low in high myopia patients and 3.0 mm TOP-map zone was better correlated than 4.0 mm TOP-map zone in these patients.

The Reproducibility and Accuracy of Biometry Parameter Measurement from IOL Master(R)

PURPOSE: To evaluate the reproducibility and accuracy of axial length and anterior chamber depth measurements from IOL Master(R). METHODS: The axial length and anterior chamber depth measurements in 30 eyes with normal crystalline lens, 30 eyes with cataract and 30 pseudophakic eyes were measured by two practitioners using IOL Master(R) followed by A-scan and Orbscan II. The reproducibility of IOL Master(R) was analyzed by comparing the results from the first and second practitioners. To evaluate the accuracy of IOL Master(R), the axial length was compared to A-scan and the anterior chamber depth was compared to A-scan and Orbscan II. RESULTS: The difference between the axial length and anterior chamber depth measurements from the two practitioners using IOL Master(R) were not statistically significant (p>0.05). The axial length of measurement from IOL Master(R) was 0.16 mm, 0.18 mm, and 0.96 mm longer than that from A-scan, in the normal, cataract and pseudophakic groups, respectively. In addition, the anterior chamber depth measurement from IOL Master(R) was significantly deeper than that from A-scan and Orbscan II (p<0.05). CONCLUSIONS: There was good reproducibility and accuracy of axial length and anterior chamber depth measurements from IOL Master(R). However, some patients who had media opacity were not measured using IOL Master(R). It is a noncontact method, which provides an alternative to A-scan.

Diagnostic Criteria for Keratoconus Using Orbscan II Slit Scanning Topography/Pachymetry System

PURPOSE: To investigate new diagnostic criteria of keratoconus using Orbscan II Slit Scanning Corneal Topography/Pachymetry System. METHODS: Eighty eyes of 45 patients with keratoconus and 100 randomly selected eyes of 50 patients without any ophthalmologic problem were enrolled in this study. Anterior elevation from BFS, posterior elevation from BFS, Sim K (maximum), and thinnest pachymetric value were evaluated using Orbscan II. Values outside 2 standard deviations from the mean value of each parameter were estimated to the upper or lower limits in diagnosing keratoconus. RESULTS: There were significant differences of all parameters of Orbscan II between the keratoconic eyes and the control (p 23.3 micro meter, posterior elevation from BFS > 49.8 micro meter, Sim K (maximum) > 47.0 D, thinnest pachymetric value < 455.0 micro meter. CONCLUSIONS: Orbscan II can provide useful information in the diagnosis of keratoconus with high sensitivity and specificity.

Measurement of Central Keratometric Value with Orbscan II(R) Topography after LASIK

PURPOSE: To compare central keratometric values (K-values) measured at the pupillary center by Orbscan II (R) topography (Orbtek, Bausch & Lomb, USA) with preexisting methods for K-values in patients who have been treated with laser in situ keratomileusis (LASIK). METHODS: A total of 36 consecutive eyes of 25 patients who were treated with LASIK for myopia have been followed up for more than 1 year. Central K-values measured by Orbscan II(R) topography, K-values measured with autorefractokeratometer, and refraction-derived K-values were compared . RESULTS: The mean central keratometric K-value measured by Orbscan II (R) topography was 39.65+/-1.94 (35.82 to 43.45) diopter (D), and was not statistically significantly different from the mean refraction derived K-value which was 39.63+/-1.95 D (35.95 to 43.41) (p>0.05), but was statistically lower than the mean K-value measured with autorefractokeratometer which was 40.23+/-1.76 D (36.56 to 43.69) (P<0.05). CONCLUSIONS: In patients who have been treated with LASIK for myopia, central keratometric K-value measured with Orbscan II R topography is not statistically significantly different from refraction derived K-value, but is lower than K-value measured with autorefractokeratometer.