Effect of photorefractive keratectomy on agreement of anterior segment variables obtained by a swept-source biometer vs a Scheimpflug-based tomographer

A comparison of white-to-white measurements obtained by Anterion AS-OCT versus three optical devices in refractive surgery candidates

BACKGROUND AND OBJECTIVES

To assess the agreement between Anterion AS-OCT and three optical devices in measuring the white-to-white (WTW) diameter in candidates for refractive surgery.

METHODS

In this cross-sectional prospective study, 129 right eyes of 129 normal individuals underwent consecutive scans with the Anterion, the Pentacam AXL, the IOLMaster 700, and the Orbscan IIz. Mean difference (MD), 95% limits of agreement (LoA), and concordance correlation coefficient (CCC) were calculated to assess agreement and interchangeability.

RESULTS

The mean age of participants was 30.4 ± 5.9 (range: 21-47) years. The mean WTW distance measured by the different instruments was as follows: 12.00 ± 0.42 mm (range, 10.57 to 13.05) using the Anterion, 11.87 ± 0.34 (11.10 to 12.80) using the Pentacam, 12.12 ± 0.44 (11.00 to 13.30) using the IOLMaster, and 11.73 ± 0.37 (11.00 to 13.10) using the Orbscan. The MD and 95% LoA for Anterion vs. Pentacam, IOLMaster, or Orbscan were [0.11; -0.31 to 0.54 mm], [-0.13; -0.93 to 0.66], and [0.25; -0.28 to 0.78], respectively. The corresponding CCCs were 0.803, 0.514, and 0.631.

CONCLUSIONS

This study found weak agreement between Anterion and Pentacam AXL, IOLMaster 700, and Orbscan IIz devices regarding WTW distance measurements in refractive surgery candidates. Therefore, it is not recommended to use Anterion's WTW measurements interchangeably with the other three devices, particularly for phakic intraocular lens sizing.

Repeatability and agreement of total corneal astigmatism measured in keratoconic eyes using four current devices

BACKGROUND

To evaluate repeatability and agreement in measurements of total corneal astigmatism (TCA) in keratoconic eyes, using four optical coherence tomography (OCT)-based devices: Anterion, Casia SS-1000, IOLMaster 700, and MS-39.

METHODS

Three consecutive measurements were taken with each device in 136 eyes. TCA values were converted into components J0 and J45. The Anterion and the IOLMaster 700 also provided axial length (AL) measurements. The repeatability was calculated using pooled within-subject standard deviation (Sw). The agreement among the four devices was assessed by pairwise comparisons and Bland-Altman plots.

RESULTS

For all devices, the repeatability of TCA measurements showed Sw ≤0.23 D for TCA magnitude, ≤0.14 D for J0, and ≤0.12 D for J45. There were statistically significant differences in TCA magnitude for each pair, except for IOLMaster 700 with MS-39, and Anterion with MS-39. The repeatability (Sw) of axis measurements had a statistically significant negative correlation with the TCA magnitude (p < 0.001 for all devices). Both Anterion and IOLMaster 700 had high repeatability in AL measurements (Sw: 0.007 mm for Anterion and 0.009 mm for IOLMaster 700). The difference in AL between the two was 0.015 ± 0.033 mm (p < 0.001).

CONCLUSIONS

All four devices showed good repeatability in TCA measurements in keratoconic eyes, the agreement for TCA measurements between the tested devices was generally low. Anterion and IOLMaster 700 showed good repeatability and agreement in AL measurements.

Keratometry Agreement Between Two Swept-Source OCT Devices in Healthy and Post-refractive Surgery Eyes

PURPOSE

To evaluate the keratometry agreement between two swept-source devices for healthy and post-refractive surgery eyes and compare them.

METHODS

One hundred volunteers between 20 and 55 years of age were recruited for this study including both healthy and post-refractive surgery eyes. Three consecutive measurements of simulated keratometry (Sim K), posterior keratometry (PK), and total keratometry (TK) were obtained with the IOLMaster 700 and Anterion. The agreement was assessed through the Bland-Altman method. Limits of agreement (LoA) were calculated as mean difference ±1.96·SD and it represents the 95% of the differences between devices.

RESULTS

For both groups, Sim K measurements exhibited a mean difference close to 0 and within a range of ±0.30 and ±0.36 diopters (D) for the control and post-refractive surgery groups, respectively. Meanwhile, the IOLMaster 700 provided flatter PK values (0.30 D on average) for both groups. In general, the post-refractive surgery group exhibited slightly greater mean differences and wider 95% LoA than the control group for Sim K and PK. Steeper TK values were obtained by the IOLMaster in both groups (control = 0.50 D and post-refractive surgery = 0.75 D). TK differences between devices were significantly greater in the post-refractive surgery group (ranging from 0.38 to 1.14 D) compared to the control group (ranging from 0.15 to 0.85 D).

CONCLUSIONS

The IOLMaster 700 and Anterion are not interchangeable for TK measurements and eyes that had corneal refractive surgery even decreased the agreement between devices. Differences between devices for Sim K and PK measurements should be clinically judged, particularly in eyes with previous corneal surgery. [J Refract Surg. 2023;39(5):347-353.].

Clinical applications of anterior segment swept-source optical coherence tomography: A systematic review

Optical coherence tomography (OCT) is a non-invasive method that provides the opportunity to examine tissues by taking cross-sectional images. OCT is increasingly being used to evaluate anterior segment (AS) pathologies. Swept-source (SS) OCT allows greater penetration and achieves better visualization of the internal configuration of AS tissues due to the longer wavelength employed and high scan speeds. We reviewed the utilization of AS SS-OCT in various conditions including glaucoma, ocular surface pathologies, iris tumors, refractive surgery, cataract surgery, and scleral diseases. A systematic literature search was carried out on PubMed, Scopus, and Web of Science databases between January 1, 2008, and September 1, 2022 using the following keywords: AS SS-OCT; dry eye and SS-OCT; ocular surface and SS-OCT; cornea and SS-OCT; dystrophy and SS-OCT; glaucoma and SS-OCT; ocular surface tumors and SS-OCT; conjunctival tumors and SS-OCT; refractive surgery and SS-OCT; cataract and SS-OCT; biometry and SS-OCT; sclera and SS-OCT; iris and SS-OCT; ciliary body and SS-OCT; artificial intelligence and SS-OCT. A total of 221 studies were included in this review. Review of the existing literature shows that SS-OCT offers several advantages in the diagnosis of AS diseases. Exclusive features of SS-OCT including rapid scanning, deeper tissue penetration, and better image quality help improve our understanding of various AS pathologies.

The influence of corneal ablation patterns on prediction error after cataract surgery in post-myopic-LASIK eyes

Purpose

To evaluate the influence of corneal ablation patterns on the prediction error after cataract surgery in post-myopic-LASIK eyes.

Methods

Eighty-three post-myopic-LASIK eyes of 83 patients that underwent uneventful cataract surgery were retrospectively included. Predicted postoperative spherical equivalence (SE) was calculated for the implanted lens using the Haigis-L and Barrett True-K formula. Prediction error at one month postsurgery was calculated as actual SE minus predicted SE. For each eye, area and decentration of the ablation zone was measured using the tangential curvature map. The associations between prediction errors and corneal ablation patterns were investigated.

Results

The mean prediction error was − 0.83 ± 1.00 D with the Haigis-L formula and − 1.00 ± 0.99 D with the Barrett True-K formula. Prediction error was positively correlated with keratometry (K) value and negatively correlated with ablation zone area using either formula, and negatively correlated with decentration of the ablation zone using the Barrett True-K formula (all P < 0.05). In the K < 37.08 D group, prediction error was negatively correlated with decentration of the ablation zone with both formulas (all P < 0.05). Multivariate analysis showed that with the Haigis-L formula, prediction error was associated with axial length (AL), K value and decentration, and with the Barrett True-K formula, prediction error was associated with AL and decentration (all P < 0.05).

Conclusion

A flatter cornea, larger corneal ablation zone and greater decentration will lead to more myopic prediction error after cataract surgery in post-myopic-LASIK eyes.

Comparison of the IOLMaster 700 and the Pentacam in the Analysis of the Lens Nuclear Density Before the Cataract Surgery

Purpose: To evaluate the difference of the lens nuclear density measured before and after mydriasis by using the IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany) and the Pentacam Scheimpflug imaging (Pentacam HR, Oculus Incorporation, Wetzlar, Germany) and investigate the relationship between the measurement data and the phacoemulsification parameters.

Methods: Patients with age-related nuclear cataracts diagnosed on the slit-lamp examination were enrolled in the age range of 53–76 years. No patient had a history of ocular surgery, laser treatment, or general disorders affecting vision. The mean optical density (OD) was measured by the IOLMaster 700 by using the Image-Pro^® Plus software before and after mydriasis. The Pentacam nucleus densitometry (PND) was obtained automatically from the Pentacam Scheimpflug imaging and compared with OD. The correlation between OD and effective phacoemulsification time (EPT), PND, and EPT were analyzed, respectively.

Results: In this study, 53 eyes of 52 patients were evaluated. Before and after mydriasis, the mean OD values were 64.34 ± 23.31 and 63.81 ± 23.21 pixel units, respectively; the mean PND values were 28.51 ± 11.42 and 25.41 ± 11.31, respectively; and the mean EPT value was 6.24 ± 3.49. The Bland–Altman analysis showed that the lens nuclear densities of the two devices were highly consistent. There was no significant difference in the OD values (t = 0.455, p > 0.05) before and after mydriasis, but the difference has existed in the PND values (t = 2.509, p < 0.05). The OD and PND values were positively correlated with EPT before and after mydriasis (r_OD−Before = 0.604, r_OD−After = 0.593, r_PND−Before = 0.701, and r_PND−After = 0.891, p < 0.01).

Conclusion: The combination of the IOLMaster 700 and the Image-Pro^® Plus software can quantitatively evaluate the degree of the cataract lens opacification. It has good consistency with the Pentacam and is positively correlated with the phacoemulsification parameters. It is expected to become a new method to predict the phacoemulsification parameters before and during cataract surgery.