Comparison of anterior ocular biometry between optical low-coherence reflectometry and anterior segment optical coherence tomography in an adult Chinese population

Biometry-Based Technique for Determining the Anterior Scleral Thickness: Validation Using Optical Coherence Tomography Landmarks

Purpose

Considering the potential role of anterior scleral thickness (AST) in myopia and the ubiquitous use of optical biometers, we applied and validated a biometry-based technique for estimating AST using optical coherence tomography (OCT) landmarks.

Methods

The AST was determined across four meridians in 62 participants (aged 20-37 years) with a swept-source OCT and a noncontact optical biometer at a mean ± SD distance of 3.13 ± 0.88 mm from the limbus. The biometer's graticule was focused and aligned with the anterior scleral reflex, which led to the generation of four prominent A-scan peaks: P1 (anterior bulbar conjunctiva), P2 (anterior episclera), P3 (anterior margin of anterior sclera), and P4 (posterior margin of anterior sclera), which were analyzed and compared with the corresponding OCT landmarks to determine tissue thickness.

Results

The AST measurements between biometer and OCT correlated for all meridians (r ≥ 0.70, overall r = 0.82; coefficient of variation [CV], 9%-12%; P < 0.01). The mean difference ± SD between two instruments for overall AST measures was 3 ± 2.8 µm (range, -18 to +16 µm; lower limits of agreement, -89 to +83 µm; P = 0.23) across all meridians. The mean ± SE AST with both instruments was found to be thickest at the inferior (562 ± 7 µm and 578 ± 7 µm) and thinnest at the superior (451 ± 7 µm and 433 ± 6 µm) meridian. The biometer demonstrated good intrasession (CV, 8.4%-9.6%) and intersession (CV, 7.9%-13.3%) repeatability for AST measurements across all meridians.

Conclusions

The noncontact optical biometer, which is typically used to determine axial length, is capable of accurately estimating AST based on OCT landmarks.

Translational Relevance

The high-resolution optical biometers can demonstrate wider application in the field of myopia research and practice to determine AST.

Anterior segment measurements and determinants of angle width with short, medium, and long axial lengths in a rural Chinese population

Purpose

To report the anterior segment measurements and investigate the determinants of angle width with short, medium, and long axial length (AL) in a rural Chinese population.

Design

Observational, population-based, cross-sectional study.

Methods

Subjects aged ≥35 years who underwent complete ocular examinations during the follow-up of the Handan Eye Study were included. Ocular data of the right eye were analyzed. Anterior segment parameters were obtained and stratified by age and sex. AL was categorized into short (<22.0 mm), medium (22.0-23.5 mm), and long (>23.5 mm) subgroups. Linear regression analyses were performed to identify the parameters associated with angle width (angle opening distance at 500 μm from the scleral spur (SS) [AOD500]).

Results

The final analysis included 4435 subjects (58.0 [49.0, 64.0] years old, 44.1% males). Smaller AOD500 was significantly associated with female sex (P = 0.032), larger iris thickness at 750 μm from the SS (IT750) (P < 0.001), larger lens vault (LV) (P < 0.001), and smaller anterior chamber volume (ACV) (P < 0.001) in the short AL subgroup; larger sphere equivalent (SE), IT750, iris curvature (IC), and LV and smaller ACV (all P < 0.001) in the medium AL subgroup; and larger SE, IT750, IA, IC, and LV and smaller ACV (all P < 0.001) in the long AL subgroup.

Conclusions

Our study provides the anterior segment parameters of a large rural Chinese population. IT750, ACV, and LV were found to be the most important factors associated with angle width.

Diagnostic imaging versus surgical procedure: intra- and postoperative OCT evaluation of sutureless scleral-fixated intraocular lens implantation and possible related complications

Because the popularity of corneal refractive surgery has been increasing throughout the last 25 years, many authors have thought to apply optical coherence tomography (OCT) to the anterior segment (AS-OCT); by revising the instrumentation needed and slightly improve the technique, it has become an element of vital importance in order to ensure a complete and exhaustive pre- and postsurgical evaluation. Many applications of OCT have been recently developed—mostly in cataract surgery due to the increasing numbers—such as chamber biometry, which is used in a preoperative stage to determine the details of IOL implantation, and lens evaluation. The aim of this review is to assess the applications of anterior segment OCT in dislocated IOL and/or capsular bag exchange surgery with scleral sutureless fixated intraocular lens and monitoring of possible postoperative complications.

New IOL formula using anterior segment three-dimensional optical coherence tomography

This retrospective study was aimed to compare prediction errors from various combinations of biometric data generated using optical coherence tomography (OCT) and develop a new intraocular lens (IOL) formula using biometric data. 145 eyes from 145 patients who underwent femtosecond laser-assisted cataract surgery (FLACS) were enrolled to the present study and they were divided into a training set (n = 92) and a test set (n = 53). Preoperative axial length (AL) and corneal radius were measured using partial coherence interferometry. The anterior chamber depth (ACD), lens meridian parameter (LMP), lens thickness (LT), thickness of anterior and posterior parts of the crystalline lens (aLT and pLT), and anterior segment length were measured by OCT. From a training set, we developed eight regression equations and analyzed the predictive accuracy. The regression equation using AL, LMP, and pLT (-1.143 + 0.148*AL + 0.428*LMP + 0.254*pLT) showed the strongest correlation with effective lens position (ELP) and smallest standard deviation of ELP prediction error. IOL formula generated using AL, LMP, and pLT yielded the highest predictive accuracy. In a test set, the new IOL formula also produced narrowest range of prediction error, smallest median absolute error, and highest percentages within ±0.25, ±0.50 than existing IOL formulas. The IOL formula considering AL, LMP and pLT will help to improve predictive accuracy in FLACS.

Preoperative biometric measurements with anterior segment optical coherence tomography and prediction of postoperative intraocular lens position

The purpose of this study is to evaluate the biometric parameters of crystalline lens components and to find effective factors for predicting postoperative intraocular lens (IOL) position. This retrospective study included 97 eyes from 97 patients with a mean age of 63.00 ± 12.38 (SD) years. The biometric measurements were performed by means of a 3-dimensional optical coherence tomography (3D-OCT) device. Specifically, anterior chamber depth (ACD), aqueous depth (AD), lens thickness (LT), lens meridian parameter (LMP), white-to-white diameters (WTW), anterior segment length (ASL), the anterior part of lens (aLT), and the posterior part of lens (pLT) were measured. Additionally, axial length (AL) and corneal radius (CR) were measured by the partial coherence interferometry. Ninety-seven eyes were divided into thin lens group (LT < 4.5 mm) and thick lens group (LT ≥ 4.5 mm). The differences between the above two groups were also analyzed. Postoperative IOL position was measured by 3D-OCT at 3 months postoperatively and regression formulas for predicting postoperative IOL position were developed by various combinations of preoperative factors. As lens thickened, ACD and AD became shallow (all P < .001). AD, ACD, ASL, aLT, and pLT showed statistically significant differences between two subgroups classified on the basis of LT (all P < .001). Meanwhile, the value obtained by subtracting aLT from pLT did not show any association with the other biometric measurements. The combination of ACD, aLT, pLT, AL, CR, and WTW showed the highest correlation with postoperative IOL position (R = 0.536, P < .001). In conclusion, pLT-aLT was an independent factor not affected by any other variables and did not show significant difference between thin lens group and thick lens group. The subdivision of the lens structure using 3D-OCT helps to predict postoperative IOL position.

Comparison of Anterior Segment Measurements with Optical Low-coherence Reflectometry and Partial-coherence Interferometry Optical Biometers

AIMS

To evaluate a new noncontact optical biometer using partial-coherence interferometry and to compare the clinical measurements with those obtained from the device using optical low-coherence reflectometry (OLCR).

SETTING AND DESIGN

Ondokuz Mayis University, Samsun, Turkey. Nonrandomized, prospective clinical trial.

SUBJECTS AND METHODS

The study was performed on the healthy phakic eyes of volunteers in the year 2014. Measurements of axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT), mean keratometry (K), and white-to-white (WTW) measurements obtained with the low-time coherence interferometry (LTCI) were compared with those obtained with the OLCR.

STATISTICAL ANALYSIS USED

The results were evaluated using Bland-Altman analyses. The differences between both methods were assessed using the paired t-test, and its correlation was evaluated by Pearson's coefficient.

RESULTS

We examined seventy participants with a mean age of 33.06 (±9.7) (range: 19-53) years. AL measurements with LTCI and OLCR were 23.7 (±1.08) mm and 23.7 (±1.1) mm, respectively. ACD was 3.6 (±0.4) mm and 3.5 (±0.4) mm for LTCI and OLCR, respectively. The mean CCT measurements for both devices were 533 (±28) mm and 522 (±28) mm, respectively. The mean K readings measurements for LTCI and OLCR were 43.3 (±1.5) D and 43.3 (±1.5) D, respectively. The mean WTW distance measurements for both devices were 12.0 (±0.5) mm and 12.1 (±0.5) mm, respectively.

CONCLUSIONS

Measurements with LTCI correlated well with those with the OLCR. These two devices showed good agreement for the measurement of all parameters.

Early Postoperative Effects of Cataract Surgery on Anterior Segment Parameters in Primary Open-Angle Glaucoma and Pseudoexfoliation Glaucoma

Objectives:

To compare the effect of cataract surgery on anterior segment parameters measured by optical biometry in primary open-angle glaucoma (POAG) and pseudoexfoliation glaucoma (PXG).

Materials and Methods:

Twenty-five eyes of 25 patients with POAG and 29 eyes of 29 patients with PXG who had uncomplicated phacoemulsification and posterior chamber intraocular lens implantation surgery were included to our prospective study. Central corneal thickness (CCT), anterior chamber depth (ACD) and axial length (AL) were measured with an optical biometer preoperatively and at 1 month postoperatively. The pre- and postoperative values of intraocular pressure (IOP) and the anterior segment parameters and the differences between POAG and PXG were compared statistically by paired t, independent t and chi-square tests.

Results:

The mean values of preoperative CCT (p=0.042) and ACD (p=0.012) were significantly lower in the PXG than in the POAG group. In the PXG group, IOP decreased (p=0.001) but CCT (p=0.03) and ACD (p=0.001) increased significantly postoperatively; AL did not change significantly. In the POAG group, IOP decreased (p=0.01) and ACD (p=0.004) increased significantly postoperatively, while AL and CCT did not change significantly. There were no significant differences in the pre- to postoperative changes in IOP (p=0.76), AL (p=0.44) and CCT (p=0.52) values between the two groups. However, the postoperative increase in ACD was larger in the PXG group (p=0.03).

Conclusion:

Cataract surgery may cause some changes in IOP and anterior segment parameters like ACD and CCT postoperatively in eyes with POAG and PXG, and these changes may differ between eyes with PXG and POAG.

Comparison of keratometry and white-to-white measurements obtained by Lenstar with those obtained by autokeratometry and corneal topography

PURPOSE

To compare anterior eye segment measurements obtained using low optical coherence reflectometry (LENSTAR LS900, Haag-Streit), autokeratometry (RC-5000, Tomey) and corneal topography (Topolyzer, Wavelight).

METHODS

In 46 healthy subjects, flat keratometry (Kf), steep keratometry (Ks), mean keratometry (Km) and white-to-white (WTW) distance were measured by Lenstar, Tomey RC-5000 and Topolyzer.

RESULTS

Kf and Km measurements of Lenstar were significantly steeper than Tomey RC-5000 (both p<0.001), but the 95% LoA of them were narrow (-0.22 to 0.46D, -0.16 to 0.36D, respectively). There were no significant differences between the Kf and Km measurements of Lenstar and Topolyzer, with a narrow 95% LoA. There were no significant differences between the Ks measurements of Lenstar and Tomey RC-5000, and Lenstar and Topolyzer. A good agreement was found between them with 95% LoA of -0.40 to 0.56D, and -0.56 to 0.64D, respectively. WTW measurements with Lenstar were greater than those with Tomey RC-5000 and Topolyzer (p=0.042, p<0.01, respectively). A good agreement existed between the WTW obtained by Lenstar and Topolyzer, Tomey RC-5000, with 95% LoA ranging from -0.13 to 0.74mm and -0.33 to 0.51mm.

CONCLUSIONS

Generally good agreement was found between the Lenstar and Tomey RC-5000, Topolyzer for K and WTW measurements. In clinical practice, K and WTW measurements obtained by Lenstar and Tomey RC-5000, Topolyzer can be used interchangeably.

Interchangeability among five devices that measure anterior eye distances

PURPOSE

The aim was to study the interchangeability of various devices that measure anterior chamber depth (ACD) and white-to-white (WTW) distance.

METHODS

Eighty right eyes of eighty patients aged 20 to 40 years were included. Their spherical equivalent ranged from -4.25 to +1.00 dioptres. Each eye's ACD and the WTW distance were measured using the following devices: a Castroviejo surgical calliper, CA-200F Corneal Analyser, Orbscan II, Pentacam HR and IOLMaster 500.

RESULTS

The Pentacam HR measured significantly greater ACD (p < 0.01) than the other two devices, whereas IOLMaster 500 and Orbscan II yielded comparable (p > 0.01) distances. Nonetheless, in every device comparison, the mean difference was within clinically acceptable limits. The device comparison showed that for WTW distance measurements IOLMaster 500 yields the greatest value (p < 0.01), whereas CA-200F Corneal Analyser yields the smallest one (p < 0.01).

CONCLUSION

Pentacam HR, Orbscan II and IOLMaster 500 can be used interchangeably to measure ACD, whereas Orbscan II, IOLMaster 500, Castroviejo surgical calliper and CA-200F Corneal Analyser cannot be considered interchangeable, when it comes to measuring WTW distance.