Comparison of radius of anterior lens surface curvature measurements in vivo using the anterior segment optical coherence tomography and Scheimpflug imaging

Measurement of in vivo lens shapes using IOLMaster 700 B-scan images: Comparison with phakometry

PURPOSE

This study compared in vivo crystalline lens shape measurements using B-scan images from the IOLMaster 700 with phakometry.

METHODS

Twenty-four young adult participants underwent IOLMaster 700 and phakometry measurements under cycloplegia (1% cyclopentolate). The IOLMaster 700 generated B-scan images along six meridians in 30° increments, which were analysed using custom MATLAB software to determine lens surface radii of curvature. Phakometry measurements were obtained using Purkinje images reflected from the lens surfaces.

RESULTS

The IOLMaster 700 image analysis method yielded a lower mean anterior lens surface spherical equivalent power (+6.20 D) than phakometry (+7.55 D); however, the two measurements were strongly correlated (R(21) = 0.97, p < 0.0001). The astigmatic power vectors (J0 and J45) for the anterior lens surface were significantly higher for the IOLMaster 700 measurements, with only J0 showing a significant moderate positive correlation (R(21) = 0.57, p = 0.005). For the posterior lens surface, the IOLMaster 700 measurements had a higher mean spherical power (+14.28 D) compared to phakometry (+13.70 D); however, a strong positive correlation (R(21) = 0.90, p < 0.0001) was observed. No significant correlations were noted for posterior lens surface astigmatic vectors (J0 and J45). The IOLMaster 700 estimates for the equivalent lens mean spherical power were slightly lower than those for phakometry, with a mean difference of -0.72 D, and both methods were positively correlated (R(21) = 0.94, p < 0.0001).

CONCLUSIONS

The findings demonstrate that IOLMaster 700 B-scan image analysis technique provides similar estimates of lens surface powers to phakometry. These results highlight the potential of the IOLMaster 700 to provide measurements of lens shape, informing future research and clinical use.

Role of swept-source anterior segment optical coherence tomography in imaging pediatric cataract

Purpose

To determine the morphology of pediatric cataracts and assess the status of the anterior and posterior capsules preoperatively on swept-source anterior segment optical coherence tomography (ASOCT) and compare the findings to those of intraoperative examination. Secondly, we aimed to obtain biometric measurements on ASOCT and compare them to those obtained on A-scan/optical methods.

Methods

This was a prospective and observational study carried out at a tertiary care referral institute. ASOCT scans for anterior segment were obtained preoperatively for all patients, aged <8 years, scheduled for paediatric cataract surgery. The morphology of the lens and capsule and biometry were performed on ASOCT and the same were assessed intraoperatively. The main outcome measures were comparison of ASOCT findings to intraoperative findings.

Results

The study included 33 eyes of 29 patients (range 3 months-8 years). The morphological characterization of cataract on ASOCT was accurate in 31/33 (94%) cases. ASOCT accurately identified fibrosis and rupture of the anterior and posterior capsules in 32/33 (97%) cases each. In 30% of eyes, ASOCT gave additional information preoperatively compared to the slit lamp. Intraclass correlation coefficient (ICC) calculation revealed a good agreement between the keratometry values obtained on ASOCT and those obtained preoperatively with a handheld/optical keratometer (ICC = 0.86, P = 0.001).

Conclusion

ASOCT is a valuable tool that could provide complete preoperative information of the lens and capsule in pediatric cataract cases. In children as young as 3 months of age, intraoperative risks and surprises could be diminished. The keratometric readings are highly dependent on patient cooperation but show good agreement with the handheld/optical keratometer readings.

In-vivo Lens Biometry Using the Novel Ultrasound Biomicroscopy

Background and Aim

To assess the reproducibility of the novel ultrasound biomicroscopy, Insight 100 and its agreement with a swept-source optical coherence tomography, CASIA2.

Methods

A total of 96 volunteers (96 eyes) were enrolled. The radius of anterior lens curvature (RAL), the radius of posterior lens curvature (RPL), lens thickness (LT), and lens diameter (LD) were measured with Insight 100 and CASIA2. A semiautomated software was used to adjust the measurement of LT (LT_S) and LD (LD_S) by Insight 100. Intraobserver and interobserver reproducibility of Insight 100 measurements, and the agreement of results from Insight 100 and CASIA2 were assessed with 95% limit of agreement (LoA), intraclass correlation coefficient (ICC), Pearson correlation, and linear regression.

Results

For Insight 100 measurements, the intraobserver ICCs of RAL, RPL, LT_S, and LD_S measurement were 0.996, 0.973, 0.936, and 0.889, and the interobserver ICCs were 0.987, 0.890, 0.974, and 0.816, respectively. There was an excellent correlation in LT measurements (R = 0.961, P < 0.001) but poor agreements in other parameters between the two devices. The LD measurements tended to be larger (95% CI: 0.768–0.928) in CASIA2 when compared with Insight 100.

Conclusion

Insight 100 could obtain highly repeatable lens biometry in vivo. With better signal penetration, it shows promising potential in future clinical applications.

Agreement of Anterior Segment Parameter Measurements With CASIA 2 and IOLMaster 700

Purpose

To compare the difference and agreement in central corneal thickness (CCT), keratometry (K), anterior chamber depth (ACD), aqueous depth (AQD), and lens thickness (LT) measured with CASIA 2 and IOLMaster 700 in patients with cataract.

Methods

A total of 81 patients with cataract (81 eyes) scheduled for phacoemulsification were prospectively collected from March to May, 2020 in the cataract department of Zhongshan Ophthalmic Center, Sun Yat-sen University, including 43 males and 38 females with age of 61.5 ± 10.6 years. CCT, anterior Kf, anterior Ks, real Kf, real Ks, ACD, AQD, and LT were measured with CASIA 2 and IOLMaster 700. Paired t-test, intraclass correlation coefficients (ICCs), 95% limit of agreement (95% LoA), and Bland-Altman plots were performed and used to analyze the difference and agreement between the two devices.

Results

There was no statistically significant difference in anterior K measurement with the CASIA 2 (44.3 ± 1.66 mm) and IOLMaster 700 (44.31 ± 1.67 mm, P = 0.483). Differences among the CCT, anterior Kf, real Kf, real Ks, ACD, AQD, and LT measured by the two instruments were statistically significant (P &lt; 0.001). The ICCs of CCT, anterior Kf, anterior Ks, real Kf, real Ks, ACD, AQD, and LT measurements between the two devices were 0.892, 0.991, 0.991, 0.827, 0.817, 0.937, 0.926, and 0.997, respectively. The 95% LoA between CASIA 2 and IOLMaster 700 was −30.06 to 0.43 μm for CCT, −0.3 to 0.48 D for anterior Kf, −0.46 to −0.43 D for anterior Ks, −1.49 to −0.49 D for real Kf, −1.62 to −0.49 D for Real Ks, −0.03 to 0.24 mm for ACD, 0.04 to 0.25 mm for AQD, and −0.06 to 0.09 mm for LT.

Conclusion

Anterior Kf, anterior Ks, ACD, AQD, and LT have excellent agreement between the two devices. CCT, real Kf, and real Ks have moderate agreement between the two devices. It is recommended to use anterior Kf, anterior Ks, ACD, AQD, and LT interchangeably between CASIA 2 and IOLMaster 700.

The Heritability of Primary Angle Closure Anatomic Traits and Predictors of Angle Closure in South Indian Siblings

PURPOSE

To estimate the heritability of ocular biometric and anterior chamber morphologic parameters and to determine predictors of angle closure concordance in South Indian probands with angle closure and their siblings DESIGN: Prospective observational cohort study METHODS: Subjects received a standardized ophthalmic examination, A-scan ultrasonography, pachymetry, and anterior segment optical coherence tomography (ASOCT) imaging. Heritability was calculated using residual correlation coefficients adjusted for age, sex, and home setting. Concordant sibling pairs were defined as both proband and sibling with angle closure. Predictors of angle closure concordance among siblings were calculated using multivariable logistic regression models.

RESULTS

A total of 345 sibling pairs participated. All anterior chamber parameters were highly heritable (P < .001 for all). Similarly, all iris parameters, axial length, lens thickness (LT), central corneal thickness, anterior lens curvature, lens vault (LV), spherical equivalent, and intraocular pressure were moderately to highly heritable (P < .004 for all). LV and LT were more heritable among concordant siblings (P < .05 for both). In contrast, ASOCT angle parameters had statistically insignificant heritability estimates. In multivariable analyses, siblings older than their probands were more likely to be concordant for angle closure (OR 1.05, 95% CI 1.01, 1.09; P = .02) and siblings with deeper anterior chamber depths (ACDs) compared to their proband were less likely to be concordant for angle closure (OR 0.74, 95% CI 0.64, 0.86; P < .001).

CONCLUSIONS

Iris, anterior chamber, and lens parameters may be heritable whereas angle parameters were not. LT and LV may play important roles in the pathogenesis of angle closure. Siblings who are older or have a shallower ACD may need more careful disease monitoring.

Calculation of ocular magnification in phakic and pseudophakic eyes based on anterior segment OCT data

PURPOSE

The purpose of this study is to develop a straightforward mathematical concept for determination of object to image magnification in both phakic and pseudophakic eyes, based on biometric measures, refractometry and data from an anterior segment optical coherence tomography (OCT).

METHODS

We have developed a strategy for calculating ocular magnification based on axial length measurement, phakic anterior chamber and lens thickness, keratometry and crystalline lens front and back surface curvatures for the phakic eye, and axial length measurement, anterior chamber and lens thickness, keratometry and intraocular lens power, refractive index and shape factor for the pseudophakic eye. Comparing the magnification of both eyes of one individual yields aniseikonia, while comparing the preoperative and postoperative situation of one eye provides the gain or loss in ocular magnification. The applicability of this strategy is shown using a clinical example and a small case series in 78 eyes of 39 patients before and after cataract surgery.

RESULTS

For the phakic eye, the refractive index of the crystalline lens was adjusted to balance the optical system. The pseudophakic eye is fully determined and we proposed three strategies for considering a potential mismatch of the data: (A) with spherical equivalent refraction, (B) with intraocular lens power and (C) with the shape factor of the lens. Magnification in the phakic eye was -0.00319 ± 0.00014 and with (A) was -0.00327 ± 0.00013, with (B) was -0.00323 ± 0.00014 and with (C) was -0.00326 ± 0.00013. With A/B/C, the magnification of the pseudophakic eye was on average 2.52 ± 2.83%/1.31 ± 2.84%/2.14 ± 2.80% larger compared with the phakic eye. Magnification changes were within a range of ±10%.

CONCLUSIONS

On average, ocular magnification does not change greatly after cataract surgery with implantation of an artificial lens, but in some cases, the change could be up to ±10%. If the changes are not consistent between the left and right eyes, then this could lead to post-cataract aniseikonia.

Evaluation of phacoemulsification (ultrasound) cataract surgery on the dynamics of the anterior segment of primary angle closure by AS-OCT

OBJECTIVE

To explore the changes of anatomical biological parameters and dynamic parameters of the anterior segment (AS) before and after primary angle closure glaucoma (PACG) surgery.

METHODS

The clinical data of 82 patients (82 eyes) who underwent phacoemulsification in our hospital were retrospectively analyzed and divided into group A (angle closure, n = 38) and group B (normal open angle, n = 44). The anatomical biological parameters and dynamic parameters were compared between the two groups before and after surgery.

RESULTS

Compared with group B, group A had smaller anterior chamber depth, higher vaulting, greater iris curvature, and smaller TISA500. Compared with group B, group A had smaller ΔTISA500 and ΔI-area. Compared with group B, the TISA500 was smaller in group A preoperatively, at 1 week, and 1 month after surgery (P < 0.05). The iris curvature was larger in group A (P < 0.05). The ΔI-area was significantly reduced in group B at 1 week and 1 month after surgery. Group B exhibited smaller ΔI-curv than group A at 1 week and 1 month after surgery (P < 0.05).

CONCLUSION

Anterior segment optical coherence tomography (AS-OCT) can effectively monitor the dynamic changes (DC) of the AS caused by phacoemulsification in patients with primary angle closure (PAC). Phacoemulsification can open the primary of PAC patients. However, their iris area does not change significantly. The biological characteristics of the iris itself may be a risk factor leading to PAC.

The Structure of the Lens and Its Associations with the Visual Quality

In humans, the lens is the organ with the ability to change morphology and refractive power, designated as accommodation, to focus light from various distances and obtain clear retinal image. The accommodative ability of the lens depends on its structure and biological parameters. The lens grows throughout the life, forming specific lens sutures and a unique gradient refractive index, and possesses regenerative ability under certain circumstances. Minimally invasive lens surgery that preserves endogenous lens epithelial stem/progenitor cells (LECs) can achieve functional lens regeneration in humans. The lens is the main source of intraocular aberration, especially intraocular higher-order aberrations (IHOAs) which is found to be binocularly symmetrical in phakic eyes. There is a compensation mechanism between corneal aberrations and lens aberrations. Therefore, the structure and the biological parameters of the lens, the binocular relationship of the lens and the correlation between the lens and cornea affect visual quality. This paper summarises the above findings and their current and potential applications in refractive surgeries, providing a comprehensive understanding of the lens as a strong determinant of visual quality in the optical system.