[Precision of a new device for biometric measurements in pseudophakic eyes]

Association of refractive outcome with postoperative anterior chamber depth measured with 3 optical biometers

PURPOSE

This study evaluated the relationship between refractive outcomes and postoperative anterior chamber depth (ACD, measured from corneal epithelium to lens) measured by swept-source optical coherence tomography (SS-OCT), optical low-coherence reflectometry (OLCR), and Scheimpflug devices under the undilated pupil.

METHODS

Patients undergoing cataract phacoemulsification with intraocular lens (IOL) implantation in a hospital setting were enrolled. Postoperative ACD (postACD) was performed with an SS-OCT device, an OLCR device, and a Scheimpflug device at least 1 month after cataract surgery. After adjusting the mean predicted error to 0, differences in refractive outcomes were calculated with the Olsen formula using actual postACD measured from 3 devices and predicted value.

RESULTS

Overall, this comparative case study included 69 eyes of 69 patients, and postACD measurements were successfully taken using all 3 devices. The postACD measured with the SS-OCT, OLCR, and Scheimpflug devices was 4.59 ± 0.30, 4.50 ± 0.30, and 4.54 ± 0.32 mm, respectively. Statistically significant differences in postACD were found among 3 devices (P < 0.001), with intraclass correlation coefficients (ICCs) and Bland-Altman showing good agreement. No significant difference in median absolute error was found with the Olsen formula using actual postACD obtained with 3 devices. Percentage prediction errors were within ± 0.50 D in 65% (OLCR), 70% (Scheimpflug), and 67% (SS-OCT) calculated by actual postACD versus 64% by predicted value.

CONCLUSION

Substantial agreement was found in postACD measurements obtained from the SS-OCT, OLCR, and Scheimpflug devices, with a trend toward comparable refractive outcomes in the Olsen formula. Meanwhile, postACD measurements may be potentially superior for the additional enhancement of refractive outcomes.

Effect of Cycloplegia on Optical Biometry in Pediatric Eyes

PURPOSE

To study the effect of cycloplegia on optical biometry parameters in pediatric eyes using the Lenstar LS 900 (Haag-Streit, Koeniz, Switzerland).

METHODS

In this observational and comparative study, 56 normal eyes and 20 cataractous eyes in children between 5 and 15 years of age were included. Measurements were taken before and after cycloplegia using 2% homatropine drops. Parameters studied were axial length, central corneal thickness, keratometry, anterior chamber depth, and lens thickness. The Wilcoxon test was used to compare the effects of cycloplegia on all parameters.

RESULTS

Cycloplegia resulted in a statistically significant decrease in axial length (P < .05), central corneal thickness (P < .05), and lens thickness (P < .001) and an increase in the anterior chamber depth (P < .001) in normal eyes. In the cataract group, cycloplegia resulted in an increase in anterior chamber depth (P < .001) and decrease in lens thickness (P < .001).

CONCLUSIONS

Biometry measurements have to be carefully interpreted in pediatric eyes where cycloplegia is an important part of the examination. [J Pediatr Ophthalmol Strabismus. 2018;55(4):260-265.].

Comparison of preoperative and postoperative measurements of optical low-coherence reflectometry biometry and assessment of its refractive predictability

PURPOSE

To compare the preoperative and postoperative measurements of optical low-coherence reflectometry (OLCR) biometry and assessment of its refractive predictability.

METHODS

A total of 114 eyes of 102 patients who underwent cataract treatment were prospectively examined. The axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), K (keratometry) 1, K2, K average (KAVE) and K astigmatic (KAST) values were recorded using Lenstar LS 900 (Haag-Streit, Koeniz, Switzerland) OLCR device. The IOL (intraocular lens) power was measured based on the SRK/T formula. The cases were divided into three subgroups according to AL (Group 1: AL < 22 mm, Group 2: 22 mm ≤ AL < 24 mm, Group 3: 24 mm ≤ AL). The mean absolute error (MAE) calculated for each eye.

RESULTS

The right eyes of 45 patients (44.1%), left eyes of 45 patients (44.1%), and both eyes of 12 patients (11.7%) were examined. The average AL in the preoperative period was 23.19 ± 1.01; it was 23.20 ± 0.99 in the postoperative period (p > 0.05). A significant deepening was detected in the postoperative ACD (preop 2.76 ± 0.38 mm, postop 3.81 ± 0.46 mm, p < 0.001). CCT was measured as 521.4 ± 36.3 µm in the preoperative period and as 530.8 ± 42.8 (p > 0.05) µm in the postoperative period. The average mean absolute error (MAE) was measured as 0.48 ± 0.41 D, whereas refractive error was - 0.081 ± 0.67 D. The MAE distribution of cases was found to be ≤ 1.5 D 109 (95.6%) eyes, and ≤ 2.0 D in 114 (100%) eyes. MAE values according to AL of the cases were calculated as 0.71 ± 0.83 D in group 1, 0.49 ± 0.43 D in group 2 and 0.41 ± 0.36 D in group 3 (p > 0.05).

CONCLUSION

When the measurement and refractive results of the OLCR biometry were evaluated, it was observed that there was a very satisfactory result and a predictable device compatible with the current literature. The SRK/T formula, one of the new generation formulas, has shown high MAE and RE results in eyes with AL ≤ 22 mm, although not statistically significant. Other new generation formulas should be tried in these eyes.

Meta-analysis of optical low-coherence reflectometry versus partial coherence interferometry biometry

A meta-analysis to compare ocular biometry measured by optical low-coherence reflectometry (Lenstar LS900; Haag Streit) and partial coherence interferometry (the IOLMaster optical biometer; Carl Zeiss Meditec). A systematic literature search was conducted for articles published up to August 6th 2015 in the Cochrane Library, PubMed, Medline, Embase, China Knowledge Resource Integrated Database and Wanfang Data. A total of 18 studies involving 1921 eyes were included. There were no statistically significant differences in axial length (mean difference [MD] 0 mm; 95% confidence interval (CI) −0.08 to 0.08 mm; p = 0.92), anterior chamber depth (MD 0.02 mm; 95% CI −0.07 to 0.10 mm; p = 0.67), flat keratometry (MD −0.05 D; 95% CI −0.16 to 0.06 D; p = 0.39), steep keratometry (MD −0.09 D; 95% CI −0.20 to 0.03 D; p = 0.13), and mean keratometry (MD −0.15 D; 95% CI −0.30 to 0.00 D; p = 0.05). The white to white distance showed a statistically significant difference (MD −0.14 mm; 95% CI −0.25 to −0.02 mm; p = 0.02). In conclusion, there was no difference in the comparison of AL, ACD and keratometry readings between the Lenstar and IOLMaster. However the WTW distance indicated a statistically significant difference between the two devices. Apart from the WTW distance, measurements for AL, ACD and keratometry readings may be used interchangeability with both devices.

Comparison of corneal astigmatism measurements of 2 optical biometer models for toric intraocular lens selection

PURPOSE

To compare corneal astigmatism measurements obtained using a new optical biometer (AL-Scan) and a standard biometer based on partial coherence interferometry (IOLMaster 500) for toric intraocular lens (IOL) selection.

SETTING

Siriraj Hospital, Mahidol University, Bangkok, Thailand.

DESIGN

Prospective comparative study.

METHODS

Keratometry (K) readings were taken with the 2 biometers in eyes of cataract patients. The corneal astigmatism readings from the 2 devices were compared. The cylinder measurements were transformed into J0 and J45 vector components for analysis, and the devices' values were compared using the paired t test. Correlation coefficients were calculated. The Bland-Altman method was used to evaluate the agreement between the sets of measurements.

RESULTS

One hundred thirty-seven eyes (81 patients) were enrolled. The magnitude of astigmatism between the new biometer 2.4 mm zone and the standard biometer was similar (P = .19). There was a statistically significant difference between values from the new biometer 3.3 mm zone and the standard biometer (P < .05). There was good correlation in the overall magnitude of astigmatism between devices. There was a trend of low correlation toward the flat cornea (K <43.0 diopters [D]), low corneal cylinder (<1.0 D), and with-the-rule astigmatism. The IOL toricity calculated from both devices was similar.

CONCLUSIONS

Corneal astigmatism measurements with the 2 biometers were similar in magnitude, especially in 2.4 mm zone of the new biometer. There was no difference in the toric IOL selections between the devices.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Reproducibility of the optical Biometer OA-1000 (Tomey)

Aim. The OA-1000 (Tomey, Japan) is a new optical biometer, which measures axial length (AL), anterior chamber depth (ACD), and central corneal thickness (CT) utilizing optical interference technology. The aim of this study was to prove the reproducibility which is considered fundamental for other clinical investigations. Methods. 55 healthy volunteers were enrolled in this study. For each measurement of AL, ACD, and CT the biometer is grabbing a sequence of 10 shots and mean value (mean) and standard deviation (SD) are displayed. Five consecutive measurements were performed and average and standard deviation were assessed. Cronbach's α was derived as a quality measure for reproducibility. Results. For AL measurement Cronbach's α was 1.000, for CT 0.999, and for ACD 0.979, respectively. Mean value for AL was 23.36 ± 1.03 mm, for ACD it was 3.60 ± 0.687 mm, and for CT it was 552.08 ± 29.70 μm, respectively. Standard deviation for AL was 0.013 ± 0.022 mm, for ACD 0.09 ± 0.11 mm, and for CT 2.18 ± 1.75 μm. One correlation was found between mean values for AL and ACD (R = 0.388, P = 0.005); no other correlations were found between mean values or values of standard deviation of AL, ACD, or CT. Conclusion. The OA-1000 shows an excellent reproducibility for measurement of AL, ACD, and CT and can be used in clinical practice.