Anterior segment variations after posterior chamber phakic intraocular lens implantation in myopic eyes

Effect of vault on predicting postoperative refractive error for posterior chamber phakic intraocular lens based on a machine learning model

PURPOSE

To investigate how vault and other biometric variations affect postoperative refractive error of implantable collamer lenses (ICLs) by integrating artificial intelligence and modified vergence formula.

SETTING

Eye and ENT Hospital of Fudan University, Shanghai, China.

DESIGN

Artificial intelligence and big data-based prediction model.

METHODS

2845 eyes that underwent uneventful spherical ICL or toric ICL implantation and with manifest refraction results 1 month postoperatively were included. 1 eye of each patient was randomly included. Random forest was used to calculate the postoperative sphere, cylinder, and spherical equivalent by inputting variable ocular parameters. The influence of predicted vault and modified Holladay formula on predicting postoperative refractive error was analyzed. Subgroup analysis of ideal vault (0.25 to 0.75 mm) and extreme vault (<0.25 mm or >0.75 mm) was performed.

RESULTS

In the test set of both ICLs, all the random forest-based models significantly improved the accuracy of predicting postoperative sphere compared with the Online Calculation & Ordering System calculator ( P < .001). For ideal vault, the combination of modified Holladay formula in spherical ICL exhibited highest accuracy ( R = 0.606). For extreme vault, the combination of predicted vault in spherical ICL enhanced R values ( R = 0.864). The combination of predicted vault and modified Holladay formula was most optimal for toric ICL in all ranges of vault (ideal vault: R = 0.516, extreme vault: R = 0.334).

CONCLUSIONS

The random forest-based calculator, considering vault and variable ocular parameters, illustrated superiority over the existing calculator on the study datasets. Choosing an appropriate lens size to control the vault within the ideal range was helpful to avoid refractive surprises.

Anterior Segment Biometry During Accommodation After Posterior Chamber Phakic Implantable Collamer Lens Implantation

PURPOSE

To evaluate the dynamic changes in anterior segment parameters during accommodation following Implantable Collamer Lens (ICL) implantation with swept-source optical coherence tomography (SS-OCT).

METHODS

Under the accommodation of 0.00 diopters (D), 3.00 D, and maximum amplitude, SS-OCT was used to examine the anterior segment parameters, including ICL vault, ICL depth (the distance between the corneal endothelium and the posterior surface of ICL), crystalline lens thickness, anterior chamber depth, and various parameters of the anterior chamber angle, comprising angle opening distance, angle recess area, trabecular iris space area, and trabecular iris angle.

RESULTS

During accommodation, the ICL vault showed a significant decrease from baseline (536 ± 278 μm) to 3.00 D (522 ± 281 μm), followed by an increase from 3.00 D to maximum amplitude (548 ± 306 μm) (analysis of variance [ANOVA], P < .001). Four eyes (2.61%) exhibited a decrease in ICL vault to less than 100 μm (47 ± 32 μm) at maximum accommodation. The ICL depth decreased significantly as accommodation increased (ANOVA, P < .001). Crystalline lens thickness increased, whereas anterior chamber depth decreased during accommodation (ANOVA, P < .001). The anterior chamber angle widened during 3.00 D of accommodation but narrowed at maximum accommodation, leading to significant changes in the angle opening distance, angle recess area, trabecular iris space area, and trabecular iris angle during accommodation (ANOVA, P < .001 for all).

CONCLUSIONS

The anterior segment, including ICL vault and anterior chamber angle, undergo significant dynamic changes during accommodation. These accommodative changes may require careful monitoring for the surgery design of ICL implantation. [J Refract Surg. 2024;40(3):e164-e172.].

Predicting post-operative vault and optimal implantable collamer lens size using machine learning based on various ophthalmic device combinations

BACKGROUND

Implantable Collamer Lens (ICL) surgery has been proven to be a safe, effective, and predictable method for correcting myopia and myopic astigmatism. However, predicting the vault and ideal ICL size remains technically challenging. Despite the growing use of artificial intelligence (AI) in ophthalmology, no AI studies have provided available choices of different instruments and combinations for further vault and size predictions. This study aimed to fill this gap and predict post-operative vault and appropriate ICL size utilizing the comparison of numerous AI algorithms, stacking ensemble learning, and data from various ophthalmic devices and combinations.

RESULTS

This retrospective and cross-sectional study included 1941 eyes of 1941 patients from Zhongshan Ophthalmic Center. For both vault prediction and ICL size selection, the combination containing Pentacam, Sirius, and UBM demonstrated the best results in test sets [R² = 0.499 (95% CI 0.470-0.528), mean absolute error = 130.655 (95% CI 128.949-132.111), accuracy = 0.895 (95% CI 0.883-0.907), AUC = 0.928 (95% CI 0.916-0.941)]. Sulcus-to-sulcus (STS), a parameter from UBM, ranked among the top five significant contributors to both post-operative vault and optimal ICL size prediction, consistently outperforming white-to-white (WTW). Moreover, dual-device combinations or single-device parameters could also effectively predict vault and ideal ICL size, and excellent ICL selection prediction was achievable using only UBM parameters.

CONCLUSIONS

Strategies based on multiple machine learning algorithms for different ophthalmic devices and combinations are applicable for vault predicting and ICL sizing, potentially improving the safety of the ICL implantation. Moreover, our findings emphasize the crucial role of UBM in the perioperative period of ICL surgery, as it provides key STS measurements that outperformed WTW measurements in predicting post-operative vault and optimal ICL size, highlighting its potential to enhance ICL implantation safety and accuracy.

Bilateral Toric Phakic Intraocular Lens Implantation for Correction of High Myopic Astigmatism in a Patient with Marfan Syndrome with Lens Coloboma: A Case Report

Marfan syndrome (MFS) is known to cause significant refractive error. Treatment options are limited in this condition for correcting refractive error. Clear lens exchange is done in these cases, but complication rates are high. Loss of accommodation is another concern in these young adults. We report toric phakic intraocular lens (pIOL) implantation in improving the uncorrected visual acuity (UCVA) in a known case of MFS with lens coloboma. A 22-year-old female patient with MFS with inferior lens coloboma underwent bilateral toric pIOL implantation in the same sitting. Pre- and post-operative UCVA and best-corrected visual acuity were assessed. Central and peripheral vaulting of the pIOL in relation to the natural lens was also assessed. UCVA improved from 20/500 to 20/20 in the right and 20/550–20/20 in the left eye. Marked central vaulting with partial peripheral vaulting was achieved. There were no post-operative complications. Phakic IOL implantation surgery could be an effective approach to achieve excellent uncorrected refractive outcome in patients with MFS to treat high myopia.

Vault changes after cyclopentolate instillation in eyes with posterior chamber phakic intraocular lens

Posterior chamber phakic intraocular lens (pIOL) implantation is a common option for correcting moderate-to-high ocular refractive defects. Because this pIOL is implanted on ciliary sulcus, the distance between the back surface of the pIOL and the anterior surface of the crystalline lens, that it is known as vault, should be measured in different conditions to ensure the technique's safety. Cyclopentolate is a drug that dilates the pupil and relaxes accommodation (cycloplegia). It is often used for different ocular examinations and for other medical purposes. However, there is no evidence of the effect of this drug on vault. This study quantified central vault changes associated with cyclopentolate instillation. We measured the vault under normal conditions (pre-cycloplegic instillation) and after instilling cyclopentolate on 39 eyes of 39 patients with implanted pIOL. Our results suggest that cyclopentolate instillation may induce changes to vault in eyes with implanted pIOL. These changes seem safe and are mainly associated with vault under normal conditions, but also with anterior chamber depth, pupillary diameter and pIOL size.

Off-Label Use of Phakic Intraocular Lens with a "Piggyback" Technique

Purpose

We report a case of a highly myopic pseudophakic patient who received off-label placement of a phakic intraocular lens (pIOL) via a “piggyback” technique, allowing the placement of an intraocular lens (IOL) in his fellow eye, resulting in improved visual acuity and emmetropia.

Case Report

A 66-year-old, highly myopic, pseudophakic male with an IOL implant in his left eye was referred for second opinion for surgical options for his phakic right eye. Given the severe myopic status of both eyes, he received off-label placement of a posterior chamber pIOL with a piggyback technique for the pseudophakic left eye followed by standard cataract surgery and intraocular lens implantation in the right eye. For the left eye, uncorrected best visual acuity improved from 20/70 to 20/25.

Conclusion

This case demonstrates the successful off-label use of a phakic IOL in a pseudophakic, highly myopic patient with a piggyback technique, resulting in improved visual acuity and ultimately allowing IOL placement in the fellow eye for emmetropia. This off-label use of pIOL can offer ophthalmologists an alternative option for pseudophakic patents with severe refractive error.

Dynamic Assessment of Light-Induced Vaulting Changes of Implantable Collamer Lens With Central Port by Swept-Source OCT: Pilot Study

Purpose

To assess dynamic variations in vault induced by changes in brightness in eyes implanted with phakic collamer intraocular lens (pIOL) with central port for correction of myopia, defining new parameters of vaulting measurement.

Methods

We used a noninvasive Fourier-domain swept-source anterior-segment optical coherence tomography (AS-OCT) system to dynamically evaluate the shifts between the pIOL and anterior chamber structures under changing light conditions. For each eye assessed, we measured vault interval (VI), which we define based on central vault values in maximum mydriasis and in maximum miosis after light-induced changes in pupil diameter, and vault range (VR), which we define as the absolute difference between the VI values.

Results

The pilot study sample comprised 39 eyes (23 patients) previously implanted (mean 107 ± 156 days) with a pIOL. A significant difference in vault value was found when maximum and minimum pupil size was assessed under changing external light conditions (P < 0.001). The mean VR from scotopic (0.5 lux) to photopic (18,500 lux) light conditions was 167 ± 70 μm.

Conclusions

Vault is continuously affected during movements of the pupil induced by external luminance.

Translational Relevance

Quantifiable dynamic parameters VR and VI obtained with this AS-OCT device describe the position of the pIOL in the posterior chamber of the eye in a more accurate and real way than static vault measurements, and may contribute to improved understanding of the behavior of the pIOL in terms of safety.

Buffering zone of implantable Collamer lens sizing in V4c

Background

The purpose of this study was to identify factors related to the unexpected vault in V4c implantable collamer lens (ICL; STAAR Surgical) implantation.

Methods

V4c ICLs were implanted in 43 eyes of 43 patients for the correction of myopia. The implanted V4c ICL sizes were determined individually with our previous V4 ICL sizing nomogram based on the sulcus-to-sulcus diameter (STS), and the V4 ICL sizes were then converted to V4c ICL sizes with a size-converting table. We defined the “normal-sizing group” as having a pre-converted ICL size larger than the STS, and the “under-sizing group” as having a pre-converted ICL size smaller than the STS. Refractive outcomes, safety and parameters related to postoperative vault were compared between the two groups.

Results

The value of “actual ICL size – STS” differed significantly between the normal-sizing and under-sizing groups (p < 0.001), but postoperative vault did not differ significantly (p = 0.442). The demographics, implanted ICL characteristics, effectiveness indexes, safety indexes, and parameters related to postoperative vault did not differ significantly between the two groups (p > 0.05). Two patients in the normal-sizing group exhibited over-vaulting; these patients had shallow anterior chambers and were implanted with high-dioptric-power ICLs.

Conclusions

The achievement of acceptable vault in both normal-sizing and under-sizing groups indicates the existence of a buffering zone in V4c ICL sizing. The smaller size of V4c ICLs should be considered in patients susceptible to over-vaulting, such as those with shallow anterior chambers and high-dioptric-power ICLs.

Comparison Over Time of Vault in Chinese Eyes Receiving Implantable Contact Lenses With or Without a Central Hole

PURPOSE

To compare the longitudinal vault changes after implantation of a posterior chamber phakic intraocular lens (pIOL) (Visian implantable contact lens) with (ICL V4c) and without (ICL V4) a central artificial hole for moderate to high myopia in Chinese eyes.

DESIGN

Retrospective case series.

METHODS

This study comprised 78 eyes implanted with the ICL V4c model and 82 eyes implanted with the ICL V4 model at our department by the same surgeon. The time course of the postoperative pIOL vault changes was quantitatively assessed using ultrasound biomicroscopy over 6 months.

RESULTS

There was a trend toward a decrease in all measures of central vault, peripheral vault, and the endothelium-anterior pIOL distance for both central hole pIOL and conventional pIOL over time, although the variance was not statistically significant (all P > .05). There were no significant between-group differences in the amount of the pIOL central vault, peripheral vault, or the endothelium-anterior pIOL distance at any time point after surgery (all P > .05).

CONCLUSIONS

The time course of the central hole pIOL vault changes is essentially equivalent to that of the conventional pIOL vault, suggesting that the presence of the central hole did not significantly affect the pIOL position.

Prevalence of Corneal Astigmatism and Anterior Segmental Biometry Characteristics Before Surgery in Chinese Congenital Cataract Patients

The prevalence and the distribution characteristics of corneal astigmatism (CA) and anterior segment biometry before surgery in Chinese congenital cataract (CC) patients are not completely understood. This study involved 400 CC patients from the Zhongshan Ophthalmic Center enrolled from February 2011 to August 2015. Data on CA, keratometry, central corneal thickness (CCT) and anterior chamber depth (ACD) were measured by the Pentacam Scheimpflug System. The mean age of patients was 54.27 months, and the ratio of boys to girls was 1.53:1. The mean CA was 2.03 diopters (D), and 39.25% of subjects had CA values ≥2 D. The most frequent (71.8%) diagnosis was with-the-rule astigmatism. Oblique astigmatism was present in 16.2% of cases, and 12% of cases had against-the-rule astigmatism. The mean keratometry measurement of cataractous eyes in bilateral patients was significantly larger than that in unilateral patients. Girls had a larger mean keratometry but a thinner CCT than did boys. The CA, CCT, and ACD of cataractous eyes were significantly larger than those of non-cataractous eyes in unilateral patients. The CA, mean keratometry, CCT, and ACD in CC patients varied with age, gender, and laterality. Fully understanding these characteristics may help inform guidelines and treatment decisions in CC patients.

Evaluation of the toric implantable collamer lens for simultaneous treatment of myopia and astigmatism

Myopic astigmatism is a prevalent condition that can be treated with spectacles, contact lenses, or laser refractive surgery. However, these treatment options have functional limitations at higher levels of refractive error. The toric implantable collamer lens is designed to treat a broad range of refractive error, generally up to -18 diopters with +1 to +6 diopters of astigmatism. Approval for a more limited treatment range of up to 15 diopters of myopia with +1 to +4 diopters of astigmatism is being sought in the US, where this device has not yet received marketing approval. Surgical correction of high-myopic astigmatism can be life-altering and allow people to participate in activities that were not previously feasible because of visual limitations. The toric implantable collamer lens is implanted behind the iris and in front of the natural crystalline lens. With earlier lens designs, it was necessary to create an iridectomy or iridotomy to prevent pupillary block. The newest toric implantable collamer lens model has a small central hole that is not visually noticeable. This eliminates the need to create a hole in the iris, thereby enhancing the safety of the procedure.