Comparison of Anterior Segment Measurements with Scheimpflug/Placido Photography-Based Topography System and IOLMaster Partial Coherence Interferometry in Patients with Cataracts

Comparison of keratometric values and anterior segment parameters measured using Scheimpflug Sirius topography and Lenstar biometry

PURPOSE

This study aimed to evaluate the consistency of preoperative keratometric values, anterior segment, and intraocular lens (IOL) power measurements in patients with cataract and no comorbidities using the Sirius topography device (CSO, Italy) and Lenstar LS 900 (Haag-Streit AG, Köeniz, Switzerland).

METHODS

Patients with grade 2 and 3 cataracts who applied to Ophthalmology Clinic of Dışkapı Yıldırım Beyazıt Education and Research Hospital, University of Health Sciences and planned for cataract surgery were included the study. Forty eyes with cataract from 40 patients were taken in the study. All patients underwent preoperative assessment using a combined Scheimpflug-Placido disc-based tomography device (Sirius) and Lenstar before cataract surgery. Keratometric measurements, such as flat keratometry (K1), steep keratometry (K2), and maximum keratometry (Kmax), and anterior segment parameters, white-to-white (WTW) distance, IOL power, astigmatism (AST), anterior chamber depth (ACD), aqueous depth (AD), and central cornea thickness (CCT), were recorded.

RESULTS

There were significant differences between K1Lenstar and K1Sirius, K2Lenstar and K2Sirius, KmaxLenstar and KmaxSirius, WTWLenstar and WTWSirius, and IOL powerLenstar versus IOL powerSirius. However, there were insignificant differences between ASTLenstar and ASTSirius, ACDLenstar versus ACDSirius, ADLenstar and ADSirius, and CCTLenstar and CCTSirius variables. Furthermore, it was found that Sirius measured significantly higher than Lenstar, especially in terms of IOL power.

CONCLUSION

Significant differences were observed between Lenstar and Sirius in terms of keratometric values, WTW distance, and IOL power. The IOL power value measured with Sirius was found to be higher than the IOL power value measured with Lenstar.

Comparison of Anterior Segment Measurements between Scheimpflug-Placido Camera and New Swept-source Optical Coherence Tomography

Purpose: We compared anterior segment measurements obtained using a Scheimpflug-Placido topographer (SIRIUS®, Costruzione Strumenti Oftalmici, Florence, Italy) and a new anterior module for a swept-source optical coherence tomography system (ANTERION®, Heidelberg Engineering Inc., Heidelberg, Germany).Methods: Anterior segment measurements were evaluated in 74 eyes of 101 patients with the two devices. Central corneal thickness (CCT), anterior chamber depth (ACD), corneal refractive power (K), J0 (Jackson cross-cylinder with axes at 180° and 90°), J45 vector (Jackson cross-cylinder with axes at 45° and 135°), and white-to-white corneal diameter (WTW) measurements obtained using the SIRIUS® system and the new anterior segment module of ANTERION® were compared.Results: The mean CCTs measured by SIRIUS® and ANTERION® were 558.69 ± 44.65 and 540.26 ± 36.57 μm, respectively. The difference was statistically significant (p < 0.005), and there were high correlations between the two methods (r = 0.915, p < 0.001). The mean ACD measurements were 3.34 ± 0.53 and 3.34 ± 0.51 mm (p = 0.856), respectively, for SIRIUS® and ANTERION®. The measurements were strongly correlated (r = 0.966, p < 0.001). The measurements of WTW, total mean K, and J0 obtained with the two systems differed significantly (p < 0.005, p = 0.017, and p < 0.005, respectively), with high correlations between the two systems (r = 0.875, r = 0.967, and r = 0.933, respectively; all p < 0.001).Conclusions: There were significant differences in measurements of K, CCT, WTW, and J0 between the two devices. Agreement analysis suggests that SIRIUS® and ANTERION® should not be used interchangeably.

Astigmatic Outcomes of Single, Non-Paired Intrastromal Limbal Relaxing Incisions During Femtosecond Laser-Assisted Cataract Surgery Based on a Custom Nomogram

Purpose

To determine astigmatic changes of intrastromal limbal-relaxing incisions (LRIs) performed during femtosecond laser-assisted cataract surgery (FLACS).

Design

Retrospective case series.

Patients and Methods

Patients undergoing FLACS with adjunctive astigmatism management with intrastromal LRIs were included. All eyes had preoperative corneal cylinder (Kcyl) ≥0.20 D on ocular biometry. An intrastromal LRI nomogram of single, non-paired LRIs placed at the 9 mm optical zone was used. Keratometry was measured preoperatively, and postoperatively at 1 week, 1 month, and 3 months (POM3). Alpins astigmatism analysis was used to calculate target-induced astigmatism (TIA, equivalent to preoperative Kcyl), surgically induced astigmatism (SIA), difference vectors (DV), and correction indices (CI). Secondary analysis included multivariable binary logistic regression to determine clinical factors associated with corrections >125% (CI > 1.25).

Results

A total of 154 eyes (125 patients) were studied. Mean preoperative Kcyl was 0.87±0.42 D (SD), which did not significantly differ from POM3 Kcyl (0.87±0.51 D, p=0.470). Only the against-the-rule (ATR) subgroup demonstrated a small but significant reduction in Kcyl from preoperative (0.96±0.51D) to POM3 (0.89±0.55D, p=0.032). Sixteen eyes (10.4%) had Kcyl ≤0.5 D preoperatively, compared to 46 eyes (29.9%) at POM3 (p<0.0001). Mean SIA was 0.80±0.52 D. Mean DV was 0.85±0.47. Mean CI was 0.79. Fifty-one eyes (33%) had astigmatism correction >125%. On multivariable regression analysis, ATR astigmatism class (p=0.026) and lower arc lengths (30º) (p=0.005) were associated with correction >125%. Lower preoperative corneal astigmatism was inversely correlated with CI (p<0.001).

Conclusion

Although intrastromal LRIs can be conveniently performed during FLACS and appear safe, only patients with ATR astigmatism demonstrated a significant reduction in corneal astigmatism 3-months postoperatively under the current nomogram. Areas for future refinements to the nomogram were identified.

Comparison of anterior segment measurements using Sirius Topographer® and Nidek Axial Length-Scan® with assessing repeatability in patients with cataracts

Purpose:

The purpose of this study is to evaluate anterior segment measurements obtained using CSO Sirius Topographer^® (CSO, Firenze, Italy) and Nidek Axial Length (AL)-Scan^® (Nidek CO., Gamagori, Japan).

Methods:

A total of 43 eyes of 43 patients were included in this prospective study. The central corneal thickness (CCT), anterior chamber depth (ACD), white-to-white distance (WTW), flat keratometry (K1), steep keratometry (K2), and mean keratometry (K) values were randomly measured three times with each device by the same examiner. The intraclass correlation coefficient of repeatability was analyzed. The compatibility of both devices was evaluated using the 95% limits of the agreement proposed by Bland and Altman.

Results:

Examiner achieved high repeatability for all parameters on each device except the WTW measured by Sirius. All measurements except WTW and K1 taken with the Sirius were higher than that taken with the Nidek AL-Scan^®. The difference in CCT, ACD, and WTW values was statistically significant.

Conclusion:

High repeatability of the measurements was achieved on both devices. Although Km, K1, and K2 measurements of the Sirius and the AL-Scan^® showed good agreement, WTW, CCT, and ACD measurements significantly differed between two devices. Thus, anterior segment measurements except for Km, K1, and K2 cannot be used interchangeably between Sirius and Nidek AL-Scan^® devices.

Comparison of anterior segment parameters and axial length measurements performed on a Scheimpflug device with biometry function and a reference optical biometer

PURPOSE

To compare measurements of axial length (AL), corneal curvature (K), anterior chamber depth (ACD) and white-to-white (WTW) distance on a new device combining Scheimpflug camera and partial coherence interferometry (Pentacam AXL) with a reference optical biometer (IOL Master 500). To evaluate differences between IOL power calculations based on the two biometers.

METHODS

Ninety-seven eyes of 97 consecutive cataract or refractive lens exchange patients were examined preoperatively on IOL Master 500 and Pentacam AXL units. Comparisons between two devices were performed for AL, K, ACD and WTW. Intraocular lens (IOL) power targeting emmetropia was calculated with SRK/T and Haigis formulas on both devices and compared.

RESULTS

There were statistically significant differences between two devices for all measured parameters (P < 0.05), except ACD (P = 0.36). Corneal curvature measured with Pentacam AXL was significantly flatter then with IOL Master. The mean difference in AL was clinically insignificant (0.01 mm; 95% LoA 0.16 mm). Pentacam AXL yielded higher IOL power in 75% of eyes for Haigis formula and in 62% of eyes for SRK/T formula, with a mean difference within ± 0.5 D for 72 and 86% of eyes, respectively.

CONCLUSIONS

There were statistically significant differences between AL, K and WTW measurements obtained with the compared biometers. Flatter corneal curvature measurements on Pentacam AXL necessitate formulas optimisation for Pentacam AXL.

Multivariate Analysis to Predict the Horizontal Anterior Chamber Diameter from Other Anterior Chamber Parameters Using Scheimpflug Imaging: Is There a Better Method Than Adding a Fixed Constant?

PURPOSE

To evaluate the predictive association between the horizontal anterior chamber diameter (HACD) and other measurements using Scheimpflug imaging, and to assess whether a method superior to using fixed constants can be proposed.

METHODS

This hospital-based study was performed in the Cornea and Refractive Surgery Services, New Medical Center (NMC) specialty hospital, Abu Dhabi. Initially, 100 candidates were included serially in the model building group (group1). All candidates underwent detailed evaluation and Scheimpflug imaging (CSO, Sirus, Italy). Subsequently, another 100 candidates were included serially in the validation group (group 2). Candidates in both groups underwent the same tests.

RESULTS

In group 1, the mean HACD was 12.25 ± 0.48 mm. This measurement correlated significantly with the horizontal visible iris diameter (HVID), anterior chamber depth, angle (ACA), and volume (ACV) (r = 0.2-0.7). The overall regression equation was HACD = 5.62 + 0.01 × ACV + 0.45 × HVID - 0.013 × ACA (adjusted R² = 0.66, p < 0.001). Situation-based equations derived from the outcomes of group 1 were tested in group 2. Equation A included all factors found significant during model-building, Equation B included only non-volumetric significant factors, and situation C only included the HVID. Equations D through F used direct substitution by HVID plus a constant to predict HACD (the constant was 0.0, 0.5, and 1.0 for Equations D, E, and F, respectively). The predicted HACD (pHACD) was within ±0.5 mm of the actual HACD (aHACD) in 93%, 88%, 87%, 83%, 69%, and 16% case for Equations A, B, C, D, E, and F, respectively. The mean prediction error was -0.14 ± 0.27 mm (p = 0.08), -0.15 ± 0.28 mm (p = 0.03), -0.18 ± 0.30 mm (p = 0.001), -0.18 ± 0.32 mm (p < 0.001), 0.33 ± 0.35 mm (p < 0.001), and 0.83 ± 0.35 mm (p < 0.001) for Equations A, B, C, D, E, and F, respectively.

CONCLUSION

Regression equations using Scheimpflug-derived anterior chamber parameters may predict HACD to varying degrees, depending on the input parameters. Adding 0.5 or 1.0 mm to the corneal diameter (CD) to estimate the HACD is not recommended.

Comparison of keratometric measurements obtained by the Verion Image Guided System with optical biometry and auto-keratorefractometer

The aim of this study was to compare the keratometric measurements of Verion Image Guided System with an optical biometer (Zeiss IOLMaster 500, Carl Zeiss Meditec, Jena, Germany) and an automated keratorefractometer (AKR) (Topcon KR-8900, Topcon, Japan). In this prospective clinical trial, the right eyes of 52 patients with cataract were examined (mean age 62.25 ± 12.16 years). The measurements were taken by the three systems in a random order. Keratometric data, magnitude of astigmatism, and astigmatic axis measurements from all three instruments were compared. The results were evaluated using, intraclass correlation coefficients (ICC), Bland-Altman plots, and paired samples t tests. The mean flat/steep K of Verion, IOLMaster, and AKR were 43.22 ± 1.38D/44.23 ± 1.46D, 43.07 ± 1.26D/44.05 ± 1.34D, and 43.07 ± 1.31D/43.89 ± 1.42D, respectively. Flat K readings of Verion were higher than IOLMaster and AKR (p < 0.05 for both). Steep K readings were different for all three (p < 0.05). The magnitude of astigmatism by Verion and IOLMaster were 0.98 ± 0.65D and 0.98 ± 0.59D (p = 0.88). The mean astigmatism measured by the AKR was 0.82 ± 0.62D, less than the other two instruments (p < 0.001). Astigmatic axis measurements of Verion and AKR differed <10° in 38, between 10° and 20° in 5, and >20° in 9 eyes; the same difference was 30, 11, and 11 eyes, respectively, between Verion and IOLMaster. Although, keratometric and astigmatic results obtained from Verion were not completely interchangeable with IOLMaster and AKR, especially the agreement between Verion and IOLMaster was excellent with ICCs close to one. However, there were pronounced astigmatic axis measurement differences between three instruments.

Anterior segment parameters and eyelids in systemic sclerosis

To evaluate main numerical parameters of anterior segment and the effects of eyelid skin changes on these parameters in patients with systemic sclerosis (SSc). Thirty-four patients with SSc and 34 healthy individuals were enrolled. Besides full eye examination, anterior segment measurements including anterior chamber depth (ACD), anterior chamber volume, anterior chamber angle width, central corneal thickness, pupil size, corneal volume and keratometry were obtained using a Sirius Scheimpflug/Placido photography-based topography system. Eyelid thickness was evaluated using the scala of the modified Rodnan skin score and the patients were subgrouped with respect to these scores to evaluate the effect of eyelid thickening on the anterior segment parameters. Age and sex distributions of the groups were similar (p > 0.05). SSc patients had steeper and thinner corneas, smaller corneal volumes, narrower, shallower and smaller anterior segments but only the mean ACD value of right eyes was found significantly less than those of the controls (p = 0.047). The mean ACD values of SSc subgroup patients with moderate to severe eyelid thickening (50 %) had lower ACD measurements compared to those of control group. (p = 0.043 for the right eyes, p = 0.070 for the left eyes). However, SSc subgroup patients with none to mild eyelid thickening (50 %) had similar anterior segment parameters with control subjects (p > 0.05). Anterior chamber parameters of the SSc patients could show significant differences. These differences occur parallel to the eyelid changes but not secondary to it.

Evaluation and comparison of the new swept source OCT-based IOLMaster 700 with the IOLMaster 500

Purpose

To compare the measurements and failure rates obtained with a new swept source optical coherence tomography (OCT)-based biometry to IOLMaster 500.

Setting

Eye Clinic, Baskent University Faculty of Medicine, Ankara, Turkey.

Design

Observational cross-sectional study and evaluation of a new diagnostic technology.

Methods

188 eyes of 101 subjects were included in the study. Measurements of axial length (AL), anterior chamber depth (ACD), corneal power (K1 and K2) and the measurement failure rate with the new Zeiss IOLMaster 700 were compared with those obtained with the IOLMaster 500. The results were evaluated using Bland–Altman analyses. The differences between both methods were assessed using the paired samples t test, and their correlation was evaluated by intraclass correlation coefficient (ICC).

Results

The mean age was 68.32±12.71 years and the male/female ratio was 29/72. The agreements between two devices were outstanding regarding AL (ICC=1.0), ACD (ICC=0.920), K1 (ICC=0.992) and K2 (ICC=0.989) values. IOLMaster 700 was able to measure ACD AL, K1 and K2 in all eyes within high-quality SD limits of the manufacturer. IOLMaster 500 was able to measure ACD in 175 eyes, whereas measurements were not possible in the remaining 13 eyes. AL measurements were not possible for 17 eyes with IOLMaster 500. Nine of these eyes had posterior subcapsular cataracts and eight had dense nuclear cataracts.

Conclusions

Although the agreement between the two devices was excellent, the IOLMaster 700 was more effective in obtaining biometric measurements in eyes with posterior subcapsular and dense nuclear cataracts.

Posterior Corneal Surface Stability after Femtosecond Laser-Assisted Keratomileusis

The purpose of this study was to evaluate posterior corneal surface variation after femtosecond laser-assisted keratomileusis in patients with myopia and myopic astigmatism. Patients were evaluated by corneal tomography preoperatively and at 1, 6, and 12 months. We analyzed changes in the posterior corneal curvature, posterior corneal elevation, and anterior chamber depth. Moreover, we explored correlation between corneal ablation depth, residual corneal thickness, percentage of ablated corneal tissue, and preoperative corneal thickness. During follow-up, the posterior corneal surface did not have a significant forward corneal shift: no significant linear relationships emerged between the anterior displacement of the posterior corneal surface and corneal ablation depth, residual corneal thickness, or percentage of ablated corneal tissue.