• PURPOSE: To compare biometry performed by an enhanced version of dual beam partial coherence interferometry and applanation ultrasound in a prospective study of 85 cataract eyes to improve refractive outcome of cataract surgery due to a more accurate calculation of intraocular lens power. • METHODS: The SRK II formula using ultrasound biometry data was employed. Three months after surgery, partial coherence interferometry biometry was repeated and refractive outcome was determined. Preoperative partial coherence interferometry biometry data were used to determine the refractive power of the intraocular lenses retrospectively and to calculate the possible refractive outcome. • RESULT: Precision of partial coherence interferometry biometry was more than 10 times better than that of ultrasound. Therefore, the possible mean absolute error for postoperative refraction achieved with partial coherence interferometry biometry was 0.49 diopters (compared with 0.67 diopters with ultrasound biometry), resulting in an improvement of 27%. Axial eye length measured with the two techniques differed by a mean of 460 μm. The difference in lens thickness measured with partial coherence interferometry and ultra-sound significantly correlated with cataract grade. A mean shortening of 120 μm of axial eye length following cataract surgery was also detected by partial coherence interferometry. • CONCLUSIONS: The enhanced version of partial coherence interferometry offers biometry with un, precedented precision (<10 μm) and resolution (~12 μm), therefore improving the refractive outcome in cataract surgery. This noninvasive technique provides a high degree of comfort for the patient, with no need for local anesthesia or pupil dilation and minimized risk of corneal infection.

Partial Coherence Interferometry: A Novel Approach to Biometry in Cataract Surgery

A post-operative manifest refractive error as close as possible to target is key when performing cataract surgery with intraocular lens (IOL) implantation, given that residual astigmatism and refractive errors negatively impact patients’ vision and satisfaction. This review explores refractive outcomes prior to modern biometry; advances in biometry and its impact on patients’ vision and refractive outcomes after cataract surgery; key factors that affect prediction accuracy; and residual refractive errors and the impact on visual outcomes. There are numerous pre-, intra-, and post-operative factors that can influence refractive outcomes after cataract surgery, leaving surgeons with a small “error budget” (i.e., the source and sum of all influencing factors). To mitigate these factors, precise measurement and correct application of ocular biometric data are required. With advances in optical biometry, prediction of patient post-operative refractory status has become more accurate, leading to an increased proportion of patients achieving their target refraction. Alongside improvements in biometry, advancements in microsurgical techniques, new IOL technologies, and enhancements to IOL power calculations have also positively impacted patients’ refractory status after cataract surgery.

/pdf/refractive-outcomes-after-cataract-surgery-qbumh3zo.pdf

Refractive Outcomes after Cataract Surgery

Purpose This study compared the extended depth of focus (EDOF) intraocular lens (IOL) (ZXR00; Tecnis® Symfony®, Johnson & Johnson Vision, Santa Ana, CA, USA) and a new presbyopia-correcting IOL that combines EDOF and multifocal profiles (ZFR00; Tecnis® Synergy®, Johnson & Johnson Vision, Santa Ana, CA, USA) with the same material. Methods The medical records of patients undergoing cataract surgery with ZXR00 or ZFR00 implantation between March 2021 and July 2021 and with the data available for the 3-month visit were reviewed. The uncorrected near, intermediate, and distance visual acuity (VA), corrected distance VA, defocus curves, refractive errors (RE), optical quality parameters, and patient-reported visual performance parameters were the main outcome measures. Results Among the twenty-three enrolled patients, twelve patients (21 eyes) received ZXR00 and nine patients (17 eyes) received ZFR00. The mean age of the patients was 59.6 ± 10.6 (range: 49 to 70) and 65.2 ± 8.2 (range: 45 to 82) years in ZXR00 and ZFR00 groups, respectively, without significant difference. There was not a significant difference between the two groups in terms of baseline parameters and postoperative RE. The ZFR00 group showed markedly superior intermediate and near VA (p < 0.001 for all) at 3 months postoperatively. In terms of optical quality, ZXR00 was significantly better than ZFR00 (p < 0.001). Conclusions Both IOLs had comparable distance VA. ZFR00 IOL was superior for intermediate and near visual acuity, but ZXR00 IOL was better for optical quality. Research with more participants is needed to support this finding.

Comparison of visual results and optical quality of two presbyopia-correcting intraocular lenses: TECNIS symfony versus TECNIS synergy

Purpose To evaluate the agreement between a new optical biometer (AL-Scan) and an anterior-segment Scheimpflug tomographer (Pentacam HR). Setting Eye Hospital of Wenzhou Medical University, Zhejiang, China. Design Prospective randomized comparative case series. Methods Three consecutive scans of the right eye of each subject were obtained using each device in a random order. The following common parameters were recorded: central corneal thickness (CCT), anterior chamber depth (ACD), aqueous depth, and keratometry (K) readings (steep, flat, and mean). Bland-Altman limits of agreement (LoA) were calculated for the common device parameters. Results The study comprised 121 healthy subjects (57 men, 64 women) with a mean age of 25.41 years ± 6.86 (SD) (range 18 to 54 years). The mean difference in CCT was 1.61 μm with LoA of −6.29 to 9.52 μm. The mean difference in the aqueous depth and ACD was 0.02 mm with LoA of −0.10 to 0.14 mm and −0.09 to 0.14 mm, respectively. For the 2.4 mm K readings from the new biometer versus the standard K readings from the Scheimpflug tomographer, the mean difference for flat K, steep K, and mean K was 0.10 diopter (D), 0.05 D, and 0.08 D, respectively. The LoA were −0.17 to 0.38 D, −0.29 to 0.39 D, and −0.19 to 0.34 D, respectively. The CCT, ACD, and all K readings were assessed to be clinically interchangeable. Conclusion There was good agreement between the 2 devices for CCT, ACD, aqueous depth, and K readings. Financial Disclosure None of the authors has a financial or proprietary interest in any material or method mentioned.

Agreement of anterior ocular biometric measurements with a new optical biometer and a Scheimpflug tomographer

To assess and compare the visual performance of two extended depth-of-focus intraocular lenses (IOLs), Tecnis Symfony (Symfony; Johnson & Johnson Vision, Santa Ana, CA) and Acrysof IQ Vivity (Vivity; Alcon Inc, Fort Worth, TX).The medical records of patients undergoing cataract surgery with Symfony or Vivity implantation from May 2021 to September 2021 and the data available for the 3-month follow-up were reviewed. The main measures of the findings were uncorrected and corrected distance (4 m) visual acuity (VA), uncorrected intermediate (66 cm) VA (UIVA) and uncorrected near (40 and 33 cm) VA (UNVA), refractive error (RE), defocus profiles analysis, optical quality parameters, and patient-reported quality of vision questionnaire results.Of the 40 patients, 19 patients (31 eyes) were treated with the Symfony IOL and 21 (32 eyes) with the Vivity IOL. The mean age of the patients was 63.4±7.8 (range, 40-76) years in the Symfony group and 61.8±9.7 (range, 40-77) years in the Vivity group. There was no meaningful difference between the two groups in the preoperative parameters, except that the Vivity group had a better CDVA. Among the main measures of results, there was no statistically significant difference, except for the UNVA (33 cm). The Symfony group also showed a smoother defocus curve at 3 months postoperatively.There was no significant difference between the two groups regarding uncorrected/corrected distance VA, UIVA, UNVA (40 cm), RE, optical quality parameters, and patient-reported quality of vision questionnaire results. The Symfony group demonstrated a significantly superior UNVA (33 cm) and a smoother defocus curve with a broad landing zone. 

A Comparative Study of Two Extended Depth of Focus Intraocular Lenses

Satisfaction of patients undergoing cataract surgery is dependent on precise predictions of refractory outcomes. Over the years, development of biometry, phacoemulsification, and intraocular lens (IOL) calculation enabled precise prediction of postoperative refractory status.

To obtain accurate IOL power, a number of factors are needed. These biometries include axial length, corneal refractive power, and anterior chamber depth. Among these factors, Olsen [1] reported that axial length plays a main role in determining postoperative refraction and is responsible for 54% of the actual refractive error. Axial length error of 100 µm translates to a postoperative refraction error of 0.28 diopters (D).

Until recently, axial length was measured by using applanation ultrasound technique, which involves contact with the cornea and can result in corneal epithelial injury, infection, and patient discomfort. Error due to corneal indentation, which can lead to axial lengths 0.1 to 0.3 mm shorter than those measured by the immersion technique, is also a major disadvantage of the applanation ultrasound method [2].

To overcome this limitation, a partial coherence interferometer (PCI), which is based on the principle similar to that of optical coherence tomography, was introduced. Axial length measured by this method was comparable to that of other methods in precision and repeatability. Especially considering that the method is of the non-applanation type, it has the advantage of giving the patient less discomfort and has a low interobserver error [3,4,5,6].

Commonly used PCIs in the clinical setting include the IOL Master (Carl Zeiss Meditiec, Jena, Germany) and Lenstar (Haag Steit AG, Koeniz, Switzerland). Recently, the new PCI AL-scan (Nidek, Gamagori, Japan) has been introduced and increases precision by using a 3-dimentional ocular tracking technique. By using PCI and scheimpflug imaging techniques, AL-scan made it possible to measure axial length, corneal refractive power, anterior chamber depth, central corneal thickness, white-to-white distance, and pupil size in a single sitting based on those values and automatically calculates the appropriate IOL power to be used in cataract surgery by onboard software.

According to previous studies, it is known that the IOL Master and Lenstar show greater or similar accuracy compared to the conventional ultrasound techniques [3,7,8]. However, studies on the newly launched PCI, AL-scan, are lacking. Therefore, in this study we used AL-scan to measure axial length and refraction. With the obtained values, IOL power is calculated to look for the degree of error compared with the predicted value preoperatively and analyze the accuracy compared to values obtained from ultrasound.

/pdf/accuracy-of-biometry-for-intraocular-lens-implantation-using-59dyrcj1yf.pdf

Accuracy of Biometry for Intraocular Lens Implantation Using the New Partial Coherence Interferometer, AL-scan

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Accuracy of Biometry for Intraocular Lens Implantation Using the New Partial Coherence Interferometer, AL-scan