Change in optical axial length after cataract surgery: segmental method vs composite method

Comparison of the accuracy of axial length measurement by different imaging methods in Sprague Dawley rats

Background

Obtaining accurate axial length (AL) is very important for the establishment of animal models of myopia. The purpose of this study is to compare the accuracy of Quantel A-B scan, OD-1 A scan, and vernier caliper in measuring AL in Sprague Dawley (SD) rats.

Methods

In total, 60 5-week-old SD rats were divided into female rat group (n = 30) and male rat group (n = 30). Quantel A-B scan and OD-1 A scan were, respectively, used to measure the AL of both eyes of each living rat, and vernier caliper was used to measure the anterior-posterior diameter of each rat's eyeball. Besides, the correlation between refractive error (RE) and AL measured by different instruments was evaluated, and the accuracy of the three measurement methods was compared according to gender and left/right eyes.

Results

There were significant differences in AL and diopter of SD rats at the same age (p < 0.05). the AL of male rats was greater than that of female rats, while diopter (D) was the opposite; There was no significant difference in AL and D between left and right eyes in the same SD rats (p > 0.05); There were statistical differences among the three measurement methods (p < 0.05), AL measured by vernier caliper was the largest, followed by Quantel A-B scan, OD-1 A scan; Difference in AL between male and female was not statistically significant between the results obtained by Quantel A-B scan and vernier caliper (p > 0.05), but there were statistically significant differences between the other two measurement methods (p < 0.05).

Conclusion

Sex is the influencing factor of AL and RE. Imaging measurement can accurately measure the AL in living small rodents. Compared with OD-1 A scan, Quantel A-B scan may be more accurate.

Dual study on the sum-of-segments method for axial length measurement: is it better?

PURPOSE

To evaluate the sum-of-segments (SOS) method for optical axial length (AL) measurements.

SETTING

Department of Ophthalmology, University of Aarhus, Denmark, and Private practice, Copenhagen, Denmark.

DESIGN

Retrospective observational study.

METHODS

2 retrospective datasets were included. The first dataset comprised 1491 university cataract cases measured with the LENSTAR LS900 preoperatively and 1 to 4 months postoperatively. The second dataset comprised 904 lens surgery cases with refractive follow-up to study the accuracy of intraocular lens power calculation. The prediction accuracy was evaluated as the difference between the observed and the expected refraction.

RESULTS

The mean difference between the preoperative and the postoperative AL readings was -0.06 mm and -0.020 mm for the standard and the SOS AL method, respectively, however with a larger variation for the SOS AL method ( P < .01). For the second dataset, the SOS method was found to increase the accuracy of the SRK/T and the Holladay formulas. With the Olsen formula, the SOS method was found to be worse ( P < .01). The highest accuracy was found using standard AL with the Olsen formula, with a mean absolute error of 0.24 diopter (D) and 89.8% of the cases within ±0.5 D.

CONCLUSIONS

The SOS method improved the accuracy of the classical formulas probably because the optical path is a better representative of the true AL. The Olsen formula already incorporates an optical path correction, and this may be the reason for the lack of improvement with the SOS method.

Comparison of two one-piece acrylic foldable intraocular lenses: Short-term change in axial movement after cataract surgery and its effect on refraction

Purpose

To compare the change in intraocular lens (IOL) axial movement, corneal power, and postoperative refraction of eyes implanted with two different single-piece, open loop, acrylic foldable IOLs with planar-haptic design: one IOL with hinges vs. one IOL without hinges. The role of IOL axial movement on short-term refractive shift after cataract surgery was also evaluated.

Methods

This retrospective comparative study enrolled consecutive patients who had phacoemulsification with aspheric IOL implantation. The IOL depth (the distance from corneal endothelium to IOL surface) and corneal power were measured via anterior-segment optical coherence tomography at 4 days and 1 month postoperatively. The changes in axial movement of the IOL, corneal power, and manifest refractive spherical equivalent (MRSE) were compared among groups, and the correlations between each lens were evaluated.

Results

IOL with hinges was implanted in 42 eyes of 42 patients and IOL without hinges was implanted in 42 eyes of 42 patients. The change in axial movement between 4 days and 1 month was significantly smaller in the IOL with hinges group than in the IOL without hinges group (p < 0.001). The axial movement of IOL with hinges did not correlate with the MRSE change; however, the forward shift of IOL without hinges correlated with the myopic refractive change (Pearson r = 0.62, p < 0.001).

Conclusion

The postoperative axial movement of IOL was more stable in the IOL with hinges group than the IOL without hinges group between 4 days and 1 month after cataract surgery. Even though the two study IOLs with planar-haptic design are made of similar acrylic materials, other characteristics such as hinge structure may affect IOL stability in the bag.

Ocular biometry with swept-source optical coherence tomography

This study aimed to summarize the outcomes reported when swept-source optical coherence tomography (SS-OCT) is used for ocular biometry. A literature search was performed to identify publications reporting clinical outcomes of patients measured with commercial SS-OCT. Twenty-nine studies were included in this review. A comprehensive analysis of the available data was performed, focusing on parameters used for intraocular lens (IOL) power calculation in cataract surgery, including keratometry, central corneal thickness, white-to-white distance, anterior chamber depth, lens thickness, axial length, IOL power, and pupil diameter. Different metrics for repeatability, reproducibility, and agreement between devices were analyzed. In general, SS-OCT biometers provide excellent repeatability and reproducibility outcomes; however, the differences obtained for some parameters measured in agreement studies should be carefully analyzed to validate the interchangeability between devices. The good outcomes reported lead us to conclude that optical biometers based on SS-OCT technology are likely to become the gold standard for ocular biometry.

Refractive change and optical biometry dynamics after 25-gauge vitrectomy in pseudophakic eyes

OBJECTIVE

To investigate the refractive change and optical biometry dynamics after 25-gauge vitrectomy without gas tamponade for macular pathology in pseudophakic eyes.

DESIGN

A prospective observational case series.

PARTICIPANTS

Patients with pseudophakic eyes who were scheduled for vitrectomy owing to macular pathology by an experienced surgeon (T.S.) at the Hayashi Eye Hospital between March 2019 and February 2020.

METHODS

The primary endpoint was the change in manifest refraction spherical equivalent (MRSE) between baseline (preoperatively) and 3 months postoperatively. The secondary endpoint was the change in optical biometry parameters obtained by swept-source optical coherence tomography-based biometers between baseline and 3 months postoperatively. Optical biometry parameters included corneal curvature and axial length, evaluated by the IOLMaster 700, and intraocular lens position-that is, lens decentration, lens tilt, and aqueous depth (AQD)-evaluated by the CASIA2.

RESULTS

Thirty-four eyes of 34 patients were enrolled. The mean MRSE values at baseline and 3 months postoperatively were -0.70 ± 1.21 diopter (D) and -0.82 ± 1.27 D, respectively, showing a significant myopic shift of -0.12 ± 0.41 D postoperatively (p = 0.043). There was no significant difference between the pre- and postoperative values of the optical biometry parameters, except for the AQD (4.28 ± 0.34 mm vs 4.27 ± 0.34 mm; p = 0.019).

CONCLUSIONS

The results suggest that replacing the vitreous by the aqueous during vitrectomy induces an average myopic shift of -0.12 D.