Preparing porcine lens to mimic human lens capsule

PURPOSE

To develop a chemical method that makes porcine lens anterior capsule resemble human lens anterior capsule in tear force and perforating force.

SETTING

Beijing Tongren Hospital, Beijing, China.

DESIGN

Experimental study.

METHODS

Porcine eyes were divided into groups, and reagents (0.9% physiological saline, 0.1% sodium hypochlorite, 0.3% sodium hypochlorite, and 0.5% sodium hypochlorite) were injected into the anterior chamber, respectively, recorded as Groups A, B, C, and D, respectively. A senior physician collected each group of anterior capsules after performing continuous circular capsulorhexis and assessing the anterior capsule's tearing and perforation forces. An additional group, which consisted of human lens anterior capsules taken in the operating room from patients with cataract, recorded as Group E. A tensile system was used to measure each sample's tensile force.

RESULTS

A significant difference was found between Group A and any other group in maximum tensile force and average tensile force in both transverse and longitudinal directions. No significant difference was found between any 2 groups from Group B to Group E. According to the surgeon's assessment, the tear force characteristic of the porcine lens anterior capsule treated with 0.1%, 0.3%, and 0.5% sodium hypochlorite solution was similar to that of the human lens anterior capsule.

CONCLUSIONS

Porcine lens capsule treated using this method can be used for training of new surgeons. The porcine lens anterior capsule treated with 0.5% sodium hypochlorite, which results showed most resembled human lens anterior capsule, can be used for robotic training.

Evaluation of continuous curvilinear capsulorhexis based on a neural-network

PURPOSE

Continuous curvilinear capsulorhexis (CCC), as a prerequisite for successful cataract surgery, is one of the most important and difficult steps in phacoemulsification. In clinical practice, the size and circularity of the capsular tear and eccentricity with the lens are often employed as indicators to evaluate the effect of CCC.

METHODS

We present a neural network-based model to improve the efficiency and accuracy of evaluation for capsulorhexis results. The capsulorhexis results evaluation model consists of the detection network based on U-Net and the nonlinear fitter built from fully connected layers. The detection network is responsible for detecting the positions of the round capsular tear and lens margin, and the nonlinear fitter is utilized to fit the outputs of the detection network and to compute the capsulorhexis results evaluation indicators. We evaluate the proposed model on an artificial eye phantom and compare its performance with the medical evaluation method.

RESULTS

The experimental results show that the average detection error of the proposed evaluation model is within 0.04 mm. Compared with the medical method (the average detection error is 0.28 mm), the detection accuracy of the proposed evaluation model is more accurate and stable.

CONCLUSION

We propose a neural network-based capsulorhexis results evaluation model to improve the accuracy of evaluation for capsulorhexis results. The results of the evaluation experiments show that the proposed results evaluation model evaluates of the effect of capsulorhexis better than the medical evaluation method.

Continuous Curvilinear Capsulorhexis - A Practical Review

BACKGROUND

Continuous curvilinear capsulorhexis (CCC) has become the gold standard technique for anterior capsulotomy, a cardinal development in modern cataract surgery. CCC enables safer and relatively convenient access to the crystalline lens, however it is more challenging to master than older methods. Understanding the physics underlying this procedure is key to achieving the desired results and avoiding complications.

PURPOSE

To review and present the established information about CCC, and to create a practical guide to this important step in cataract surgery.

METHODS

A literature review was conducted using PubMed, Embase, Cochrane and Scopus databases, with emphasis on up-to-date information. The first part of this review describes the evolution of CCC and discusses the different approaches, the various instruments available, tips and pearls and the general setup for best results. The second half covers more recent innovations and common complications, and strategies to prevent or manage them. This paper provides a practical review of all aspects of CCC.

Modified bandage-contact-lens used as a guide-marker for performing continuous-curvilinear-capsulorhexis by a first-year-post-graduate-ophthalmology-resident

Purpose

To define the use of modified bandage-contact-lens as a guide-marker for performing continuous-curvilinear-capsulorhexis by a first-year-post-graduate-ophthalmology-resident.

Observation

Phacoemulsification has now become the standard cataract surgery in which anterior capsulorhexis is the first and most crucial step. A perfect capsulorhexis is difficult to learn and even more difficult to master with a steep learning curve when performed free-hand especially by a first-year post-graduate ophthalmology-resident. There is paucity of simple, single-use, easily portable, cost-effective and affordable devices designed especially for performing CCCs in a safe and reproducible way.

In our technique, the bandage contact lens (BCL) is trephined using a 6mm corneal trephine. After topical or peribulbar block (as the case may be), the 6mm-guide-marker (trephined BCL) is placed on the cornea. The CCC is then completed using the edge of the contact-lens as a guide for CCC.

Conclusion

AND IMPORTANCE: CCC with contact-lens-guide-marker is expected to yield better results in carrying out the procedure more accurately being closer to the target in terms of size, circularity and centration as compared to contact-lens-unassisted conventional CCC. This would eventually facilitate better surgical outcomes and we recommend this to be applied as the standard protocol for first-year post-graduate ophthalmology-resident performing the surgery.

Techniques of anterior capsulotomy in cataract surgery

Optimal outcomes of a cataract surgery largely depend on the successful performance of an anterior capsulotomy. It is one of the most important steps of modern cataract surgery which reduces the risk of capsular tears and ensures postoperative stable intraocular lens (IOL). Anterior capsulotomy is considered ideal if it is round, continuous, well-centered, and overlaps the implanted IOL around its circumference. If any of these features is missing, it can be a cause of impedance for desired surgical and visual outcomes. Manual can opener and manual capsulorhexis are the routine standard techniques employed for manual extracapsular cataract extraction and phacoemulsification, respectively. Recent increasing use of femtosecond laser cataract surgery has allowed cataract surgeons to obviate inherent inaccuracies of manual anterior capsulotomy techniques. There is an ongoing quest to find an ideal, risk free, and surgeon-friendly technique of anterior capsulotomy that can be employed for surgery in all types of cataracts.

Advances in capsulorhexis

PURPOSE OF REVIEW

Continuous curvilinear manual capsulorhexis is currently the standard of cataract surgery. In the past several years, new technologies have been developed to improve the consistency and safety of capsulorhexis creation. This article reviews the most recent technologies in capsulotomy formation and their advantages and disadvantages.

RECENT FINDINGS

Guidance devices, femtosecond laser capsulotomy and precision pulse capsulotomy improve the centration, circularity and precision of anterior capsulorhexis and capsulotomy. These developments show particular promise for complex cataract surgeries, though clinical data on the refractive outcomes and complication rates of these technologies are currently limited and warrant additional investigation.

SUMMARY

New technological advances in capsulorhexis help surgeons achieve a more ideal capsulotomy geometry. Whether this translates into more predictable refractive outcomes and safer surgeries remains an area of future study.

Clinical results of the open ring PMMA guider assisted capsulorrhexis in cataract surgery

Background

To compare the results of continuous curvilinear capsulorrhexis(CCC) after application of an open ring-shaped guider compared with a free-hand procedure in eyes with cataracts.

Methods

This study comprised patients undergoing cataract surgery in Seoul St.Mary’s Hospital, The Catholic University of Korea. Eyes were grouped depending on the capsulotomy method; CCC was performed by free-hand procedure on 94 eyes (free-hand group), and it was performed under the guidance after introduction of an open ring-shaped guider on consecutive 89 eyes (guided group). Horizontal and vertical diameter, area and circularity of capsulotomy were measured postoperatively at one day, two months and six months. Differences in parameters and the percentage of ideal capsulorrhexis were analyzed between the two groups.

Results

On the first postoperative day, the vertical diameter in the guided group (5.24 ± 0.16 mm) was significantly longer than that of the free-hand group (5.01 ± 0.65 mm, P = 0.019). The area of capsulotomy was larger in the guided group (21.55 ± 0.87 mm²) than that of the free-hand group (20.34 ± 2.96 mm², P < 0.001). Circularity in the guided group (0.84 ± 0.03), was significantly greater than that of the free-hand group (0.69 ± 0.17, P = 0.036). Ideal capsulorrhexis was obtained in 60 eyes (67%) in the free-hand group and 81 eyes (86%) in the guided group.

Conclusions

After introduction of an open ring-shaped guider, CCC became larger and more circular with less anterior capsular contracture. The rate of acquiring ideal capsulorrhexis was higher in the guided group than it was in the free-hand group for six months after surgery.