The elastic properties of the lens capsule in capsulorhexis

A study for lens capsule tearing during capsulotomy by finite element simulation

BACKGROUND AND OBJECTIVE

During capsulotomy, the force applied to the anterior capsule is a crucial parameter controlling capsule tears, that affects the clinical performance. This study aims to investigate the tear force in capsulotomy and analyze the effects of different tearing conditions on the tear force.

METHODS

A three-dimensional model of the human lens was constructed based on published clinical data using the finite element (FE) method. The lens model consisted of four layers: the anterior and posterior lens capsule, the cortex, and the nucleus. Distortion energy failure criterion combined with the bilinear interface law was used to express the crack propagation process at the edge of the anterior lens capsule. At the clamping position, a local coordinate system was established to parameterize the capsule tearing. The simulation results were then validated by conducting a capsulorhexis experiment using isolated porcine eyes with force-sensing forceps.

RESULTS

The simulation results showed a good agreement with the experimental data of two porcine specimens (No. 6 and 9) during a stable tearing process (p-values = 0.76 and 0.10). The mean force differences between the experimental data and the simulation were 3.10 ± 2.24 mN and 2.14 ± 1.73 mN, respectively. The tear direction with a minimum mean tear force was at θ₁ = 0° and θ₂ = 30°. The tear velocity was not significantly different to the variation in the tear force. However, an appropriate capsulorhexis diameter was found to contribute to the reduction of tear force.

CONCLUSIONS

The outcome of this paper demonstrates that our FE model could be used in modeling lens capsule tearing and the theoretical study of tear mechanism.

Flap motility as a sign of posterior capsule rupture in peripherally extended anterior capsular tears

Purpose

To describe various types of anterior capsular tears and an early diagnostic, flap motility, as a sign of posterior capsular rupture following posterior extension of radial tears.

Design

This was a prospective study carried out in 4,331 eyes that underwent phacoemulsification in a private practice setting from April 2015 to February 2016. Twenty six consecutive cases of anterior capsular tears were included. Morphological features of anterior capsular tears and resultant complications were evaluated. Parameters studied were surgical step during which the tear occurred, shape of tear, its extension in relation to the equator, and flap nature and motility in tear extending up to equator.

Main outcome measures

The main outcome measures were motility and nature of flaps in anterior capsular radial tears and the relation to posterior capsule rupture.

Results

Based on shape, extent, and angulation, anterior capsular tears were categorized into 5 types: Type I, pre-equatorial radial tear (26.92%); Type II, post-equatorial radial tear (3.85%); Type III, Argentinean flag sign pre-equatorial tear (57.69%); Type IV, Argentinean flag sign post-equatorial tear (7.69%), and Type V, mini punch (3.85%). Flaps were either seen to be everted and fluttering or inverted and non-fluttering. In all cases with everted fluttering flaps no posterior capsular rupture (PCR) was observed, while in cases with inverted non-fluttering flaps a PCR was observed (p<0.05).

Conclusion

Everted and fluttering flaps of the anterior capsular tears indicate pre-equatorial tear, while inverted and non-fluttering flaps indicate posterior capsule rupture following tear extension beyond the equator.

Precision Pulse Capsulotomy: Preclinical Safety and Performance of a New Capsulotomy Technology

PURPOSE

To assess the preclinical safety and performance of a new precision pulse capsulotomy (PPC) method.

DESIGN

Human cadaver eye studies and surgical, slit-lamp, and histopathologic evaluation in a consecutive series of 20 live rabbits.

PARTICIPANTS

Human cadaver eyes and New Zealand white rabbits.

METHODS

Precision pulse capsulotomy uses a highly focused, fast, multipulse, low-energy discharge to produce a perfectly round anterior capsulotomy instantaneously and simultaneously along all 360°. Capsulotomies are performed using a disposable handpiece with a soft collapsible tip and circular nitinol cutting element. Miyake-Apple imaging and scanning electron microscopy (SEM) of PPC were conducted in human cadaver eyes. Surgical, postoperative slit-lamp, and histopathologic assessments of PPC were performed in 20 live rabbits and were compared with manual continuous curvilinear capsulorrhexis (CCC) in the fellow eye. Anterior chamber (AC) thermocouple temperature measurements were evaluated in a subset of rabbit eyes.

MAIN OUTCOME MEASURES

Capsulotomy edge circularity, SEM morphologic features and zonular movement with PPC in human cadaver eyes. Anterior chamber temperature during PPC and grading of ocular inflammation, corneal endothelial damage, anterior capsular opacification (ACO), and posterior capsular opacification (PCO).

RESULTS

Miyake-Apple imaging showed minimal zonular stress, and thermocouple measurements demonstrated negligible AC temperature changes during PPC. Precision pulse capsulotomy produced round, complete capsulotomies in all 20 rabbit eyes, leading to successful in-the-bag intraocular lens (IOL) implantation. Slit-lamp examinations at 3 days and 1, 2, and 4 weeks after surgery showed no significant differences between PPC and CCC in corneal edema, AC inflammatory reaction, capsular fibrosis, ACO, and PCO. Postmortem studies showed no difference in the corneal endothelium between PPC and CCC eyes. All IOLs were well centered in PPC eyes, and histopathologic analysis showed no greater inflammatory infiltrates.

CONCLUSIONS

Precision pulse capsulotomy is a new method to automate consistent creation of a perfectly circular anterior capsulotomy with a disposable handheld instrument that can be used in the normal phacoemulsification surgical sequence. Compared with CCC in fellow rabbit eyes, PPC was equally safe and showed no greater zonular stress compared with CCC in human cadaver eyes. Human cadaver eye SEM showed a much smoother capsulotomy edge compared to those produced by femtosecond laser.

New device for creating a continuous curvilinear capsulorhexis

PURPOSE

To describe the evolution of a new device to facilitate continuous curvilinear capsulorhexis (CCC) creation.

SETTING

Department of Ophthalmology, University of Colorado School of Medicine, Aurora, Colorado, USA.

DESIGN

Experimental study.

METHODS

Bench-side ex vivo testing of unique prototypes for guidance and assistance of CCC in bovine and human eyes was performed. Five designs were sequentially tested as follows: a flexible circular blade of nickel-titanium alloy (nitinol), a flexible nitinol guide wire, a flexible elastomeric suction device, a combination approach of a nitinol guide wire and flexible silicone ring, and a freestanding micropatterned silicone ring.

RESULTS

The first 3 designs were not amenable to insertion through a sub-2.4 mm corneal incision and failed to maintain adequate downward force to cut the capsule and/or prevent radial tears. The fourth design was successfully inserted through a 2.4 mm incision and maintained adequate downward pressure and contact to guide a manual CCC without radial tears. The final design was insertable through a 2.4 mm incision and exhibited self-adhesive characteristics after placement on the anterior capsule of an ophthalmic viscosurgical device-filled anterior chamber.

CONCLUSIONS

Given the steep learning curve of manual capsulorhexis and the high cost of capsulotomy-assistive devices, such as the femtosecond laser, an alternative approach for creating a CCC is desirable. Performance of a highly precise manual CCC through a small incision using a medical-grade silicone device with an adhesive micropatterned design is a viable and cost-effective option for use in cataract surgery across a wide range of user experience.

FINANCIAL DISCLOSURE

All authors are named as the inventors in a patent filed by the University of Colorado covering the details in this report.

Symmetric bimanual phacofragmentation: a new approach for nucleus disassembly

PURPOSE

To describe a new technique to split the lens nucleus inside the capsular bag, using a novel pair of instruments.

METHODS

Two identical instruments are employed on the horizontal axis to promote nuclear splitting into 2 or more fragments. Each instrument has a portion that functions as a hook (H); an anterior edge, opposite to the hook, which acts as a knife (K); and a surface area located between the hook and knife, which functions as a cracker (C).

RESULTS

Nuclei up to grade 4 nuclear sclerosis were successfully fractured employing this technique.

CONCLUSIONS

Symmetric bimanual phacofragmentation with HKC instruments provides effective bimanual splitting of nuclei for phacoemulsification, also allowing depth adjustment of cleavage plane, and can be applied for a wide range of nuclear densities.

Analysis of femtosecond laser assisted capsulotomy cutting edges and manual capsulorhexis using environmental scanning electron microscopy

Purpose. To investigate the structure and irregularity of the capsulotomy cutting edges created by two femtosecond (FS) laser platforms in comparison with manual continuous circular capsulorhexis (CCC) using environmental scanning electron microscopy (eSEM). Methods. Ten anterior capsulotomies were obtained using two different FS laser cataract platforms (LenSx, n = 5, and Victus, n = 5). In addition, five manual CCC (n = 5) were obtained using a rhexis forceps. The specimens were imaged by eSEM (FEI Quanta 400, OR, USA). Objective metrics, which included the arithmetic mean deviation of the surface (Sa) and the root-mean-square deviation of the surface (Sq), were used to evaluate the irregularity of both the FS laser capsulotomies and the manual CCC cutting edges. Results. Several microirregularities were shown across the FS laser capsulotomy cutting edges. The edges of manually torn capsules were shown, by comparison of Sa and Sq values, to be smoother (P < 0.05) than the FS laser capsulotomy edges. Conclusions. Work is needed to understand whether the FS laser capsulotomy edge microirregularities, not seen in manual CCC, may act as focal points for the concentration of stress that would increase the risk of capsular tear during phacoemulsification as recently reported in the literature.

Effects of trypan blue on corneal endothelium and anterior lens capsule in albino wistar rats: An investigator-masked, controlled, two-period, experimental study

BACKGROUND

The development of continuous curvilinear capsulorrhexis (CCC) has contributed significantly to the tolerability and effectiveness of cataract extraction and intraocular lens implantation. Staining of the anterior capsule has become a popular method of increasing visibility when performing CCC.

OBJECTIVE

The aim of this study was to determine, using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the highest concentrations of trypan blue dye that would not cause long-term toxicity after injection into the anterior chamber of rat eyes.

METHODS

The eyes of healthy female albino Wistar rats were used in this investigator-masked, controlled, 2-period, experimental study conducted over 12 weeks at the Dicle University Experimental Animal Laboratory, Diyarbakir, Turkey. The rats were randomly divided into 5 groups of 4 using a random-number table. Each rat was administered a 0.05-mL injection of trypan blue into the right eye in 1 of the following concentrations: 0.4%, 0.2%, 0.1%, 0.05%, or 0.025%. A 0.05-mL pH-balanced saline solution was injected into the left eye of each rat to act as a control. At 1 day after injection and 4 weeks after injection (early period), 1 rat from each concentration group was euthanized and their eyes were enucleated. At 12 weeks after injection (late period) the remaining 2 rats from each group were euthanized and their eyes were enucleated. Corneal endothelial cells and the anterior lens capsule of the enucleated eyes were analyzed using SEM and TEM, and the results were compared with those of the control group. In the TEM analysis, the primary end point was the histopathologic changes in the cellular organelles when compared with those in the control group. In the SEM analysis, the primary end point was changes in cell shape, intracellular junctions, and density of the microvilli when compared with those in the control group.

RESULTS

Forty eyes from 20 albino Wistar rats (mean [SD] age, 8.2 [1.6] weeks; mean [SD] weight, 175.6 [16.5] g) were used in the study. Each group of rats received a different concentration of trypan blue in the right eye. In the early period, both the 0.4% and 0.2% concentrations were associated with the impairment of the hexagonal structure of corneal endothelial cells and intercellular junctions. Those concentrations were also associated with an increased occurrence of cellular vacuolation, cytoplasmic edema, extensive granulation of the endoplasmic reticulum, pyknotic nuclei, and mitochondrial degeneration. In the late period, these changes were observed as persisting in a decreasing manner. With the 0.1% and 0.05% concentrations, the density of microvilli decreased, nuclei appeared normal, granulation of the endoplasmic reticulum and Golgi apparatus was active, and minimal levels of mitochondrial degeneration were observed.

CONCLUSIONS

In this small experimental study in rat eyes, trypan blue at concentrations >0.025% was associated with impaired morphology and structure of corneal endothelial cells after short-term exposure. This effect continued in a decreasing fashion after long-term exposure. No significant changes were noted in the control group or the group administered the 0.025% concentration.

Capsulorhexis: Pearls and pitfalls

A critical step in phacoemulsification (as well as extracapsular cataract extraction) is making a window in anterior capsule wall (i.e. anterior capsulotomy). Continuous Curvilinear Capsulorhexis (CCC) has become recognized as the standard method of anterior capsulectomy. Techniques employed for CCC have undergone sustained evolution. The present review evaluates elementary principles of CCC. Management of CCC in the presence of small pupil and pseudoexfoliation syndrome is discussed. Main differences of pediatric CCC from its adult-style counterpart and finally several techniques of rescue of an extending capsulorhexis are also reviewed.

Comparison of capsulorhexis resistance to tearing with and without trypan blue dye using a mechanized tensile strength model

PURPOSE

To evaluate the influence of trypan blue staining on capsulorhexis tear resistance using a model for mechanical measurement of the entire capsular bag of fresh human cadaver eyes.

SETTING

John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Experimental study.

METHODS

After the cornea and iris were removed, a 5.0 to 5.5 mm anterior continuous curvilinear capsulorhexis (CCC) was created; the capsule in study eyes was stained with trypan blue. The nucleus was hydroexpressed and the capsular bag was evacuated by irrigation/aspiration. Two metal shoetree-shaped fixtures were implanted separately in the capsular bag and assembled using a screw nut. After zonulectomy, the fixture-capsular bag assembly was removed from the eye and loaded onto a mechanized tester. The fixtures were separated at a velocity of 7.0 mm/min in 0.15 μm intervals to stretch the capsulorhexis to its rupture point. A graph was generated for each eye.

RESULTS

Ten study eyes were compared with 23 control eyes. The groups were comparable in donor age, time from death, and CCC diameter. The mean rupture load was 0.40 Newton (N) ± 0.13 (SD) in the trypan blue group and 0.39 ± 0.16 N in the control group (P=.94). The mean extension was 5.70 ± 0.99 mm and 5.85 ± 1.17 mm, respectively (P=.74).

CONCLUSIONS

There was no difference in CCC strength between trypan blue-stained capsules and control capsules. Staining with trypan blue did not reduce CCC tear resistance.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Femtosecond laser-assisted cataract surgery with integrated optical coherence tomography

About one-third of people in the developed world will undergo cataract surgery in their lifetime. Although marked improvements in surgical technique have occurred since the development of the current approach to lens replacement in the late 1960s and early 1970s, some critical steps of the procedure can still only be executed with limited precision. Current practice requires manual formation of an opening in the anterior lens capsule, fragmentation and evacuation of the lens tissue with an ultrasound probe, and implantation of a plastic intraocular lens into the remaining capsular bag. The size, shape, and position of the anterior capsular opening (one of the most critical steps in the procedure) are controlled by freehand pulling and tearing of the capsular tissue. Here, we report a technique that improves the precision and reproducibility of cataract surgery by performing anterior capsulotomy, lens segmentation, and corneal incisions with a femtosecond laser. The placement of the cuts was determined by imaging the anterior segment of the eye with integrated optical coherence tomography. Femtosecond laser produced continuous anterior capsular incisions, which were twice as strong and more than five times as precise in size and shape than manual capsulorhexis. Lens segmentation and softening simplified its emulsification and removal, decreasing the perceived cataract hardness by two grades. Three-dimensional cutting of the cornea guided by diagnostic imaging creates multiplanar self-sealing incisions and allows exact placement of the limbal relaxing incisions, potentially increasing the safety and performance of cataract surgery.

Rescue of an extending capsulorrhexis by creating a midway tangential anterior capsular flap: a novel technique in 22 eyes

OBJECTIVE

To show how an extending capsulorrhexis can be rescued by a midway tangential capsular flap in order to achieve an uneventful phacoemulsification.

DESIGN

Consecutive case series.

PARTICIPANTS

Twenty-two eyes of 22 patients with extending capsulorrhexis treated at the Farabi Eye Hospital, Tehran.

METHODS

First, a tangential capsular opening was created on the border of the presumed continuous curvilinear capsulorrhexis just midway between the beginning of the capsulorrhexis and the edge of the extending capsulorrhexis, to make a tangential flap of the anterior capsule. Second, the centre of this new flap was grasped and pulled centripetally until the edges of the new flap joined the edges of the extending flap to complete the capsulorrhexis.

RESULTS

The technique was successfully performed in all cases, leading to an uneventful phacoemulsification.

CONCLUSIONS

Midway tangential capsular flap is a safe and effective technique to rescue an extending capsulorrhexis and leads to an uneventful phacoemulsification.

Anterior capsulotomy with a pulsed-electron avalanche knife

PURPOSE

To evaluate a new pulsed-electron avalanche knife design for creating a continuous curvilinear capsulotomy (CCC) and compare the CCC with a mechanical capsulorhexis.

SETTING

Department of Ophthalmology, Stanford University, Stanford, California, USA.

METHODS

In this study, CCCs were created in freshly enucleated bovine eyes and in rabbit eyes in vivo. The cutting velocity was adjusted by controlling the burst repetition rate, voltage amplitude, and burst duration. Tissue samples were fixed and processed for histology and scanning electron microscopy (SEM) immediately after surgery.

RESULTS

The study included 50 bovine eyes and 10 rabbit eyes. By adjusting the electrosurgical waveforms, gas-bubble formation was minimized to permit good surgical visualization. The optimum voltage level was determined to be +/-410 V with a burst duration of 20 mus. Burst repetition rate, continuously adjustable from 20 to 200 Hz with footpedal control, allowed the surgeon to vary linear cutting velocity up to 2.0 mm/s. Histology and SEM showed that the pulsed-electron avalanche knife produced sharp-edged capsule cutting without radial nicks or tears.

CONCLUSIONS

The probe of the pulsed-electron avalanche knife duplicated the surgical feel of a 25-gauge cystotome and created a histologically smooth capsule cut. It may improve precision and reproducibility of creating a CCC, as well as improve its proper sizing and centration, especially in the face of surgical risk factors, such as weak zonules or poor visibility.

FINANCIAL DISCLOSURES

Drs. Palanker and Vankov hold patents to the pulsed electron avalanche knife technology, which are licensed to PEAK Surgical by Stanford University. Drs. Palanker and Chang are consultants to PEAK Surgical. Dr. Vankov is an employee of PEAK Surgical. Neither of the other authors has a financial or proprietary interest in any material or method mentioned.

The lens capsule and zonulae

The embryology and natural history of the lens capsule and the zonular apparatus have been described according to the present knowledge of the subject. Clinical evidence pointing towards an active turnover of lens capsule material is presented.

Capsulotomy and hydroprocedures for nucleus prolapse in manual small incision cataract surgery

Manual small incision cataract surgery (MSICS) involves the manual removal of nucleus through a scleral tunnel. To achieve 100% success every time, one has to do a good capsulotomy and should master the technique to prolapse the nucleus into anterior chamber. During conversion from extracapsular cataract surgery to MSICS, one can perform a can-opener capsulotomy and prolapse the nucleus. However, it is safer and better to perform a capsulorrhexis and hydroprolapse the nucleus, as it makes the rest of the steps of MSICS comfortable. Use of trypan blue in white and brown cataracts makes the capsulorrhexis and prolapse simple and safe. Extra caution should be taken in cases with hypermature cataracts with weak zonules and subluxated cataracts.

Assessment of the strength of minicapsulorhexes

PURPOSE

To evaluate the effect of age, size, position, and species on the strength of minicapsulorhexes.

SETTING

Surgical Suite and Laser Laboratory, Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA.

METHODS

Capsulorhexes 0.7 to 2.3 mm in diameter were made centrally or peripherally in 35 eye-bank eyes and 32 rabbit eyes. A custom-made instrument stretched the capsulorhexes until rupture. Load and stretch at rupture were recorded.

RESULTS

Maximum load and stretch were 26.3 mN +/- 20.3 (SD) and 50% +/- 18% for central and 50.8 +/- 20.5 mN and 69% +/- 17% for peripheral capsulorhexes in eye-bank eyes and 19.8 +/- 15.2 mN and 38% +/- 13% for central and 13.5 +/- 9.5 mN and 30% +/- 7% for peripheral capsulorhexes in rabbit eyes. Peripheral capsulorhexes were stronger and more elastic than central capsulorhexes in eye-bank eyes, and maximum load and stretch increased statistically with the capsulorhexis diameter.

CONCLUSIONS

Peripheral minicapsulorhexes were more resistant to rupture than central capsulorhexes in eye-bank eyes, probably because of increased lens capsule thickness at the periphery. An increase in capsulorhexis diameter increased the resistance to rupture.

Five-year experience of the 2-incision push-pull technique for anterior and posterior capsulorrhexis in pediatric cataract surgery

PURPOSE

To describe the authors' 5-year experience of the 2-incision push-pull (TIPP) technique for pediatric anterior and posterior capsulorrhexis formation.

DESIGN

Retrospective descriptive study over a 5-year period.

PARTICIPANTS

A total of 84 eyes of 63 patients who had undergone cataract surgery in 1 center.

METHODS

Retrospective review of all consecutive patients who underwent pediatric cataract extraction with planned intraocular lens implantation and TIPP rhexis between January, 1999, and August, 2004. Any lost capsulorrhexis, or capsular tears at any stage of the operation, and the relation of optic size to anterior capsulorrhexis size were noted.

MAIN OUTCOME MEASURES

Complications during TIPP rhexis formation and any late complications at last visit.

RESULTS

The mean age at operation was 70.21 months (range, 4 weeks-18 years). All eyes had anterior TIPP rhexis; 41 eyes also had posterior TIPP rhexis, and there were no anterior or posterior capsulorrhexis loss or tears while performing the technique. In no patient in whom TIPP rhexis was performed for the posterior capsule was there an inadvertent vitreous loss during rhexis formation. All eyes had anterior rhexis diameters that were smaller than the optic diameter (5.5-6.0 mm), approximately 4 to 4.5 mm in diameter. Four capsular tears were reported; 1 tear occurred during irrigation and aspiration and the others during rigid lens insertion. No late complications were noted.

CONCLUSIONS

Our 5-year experience with the TIPP rhexis in pediatric cataract surgery has shown this to be a reliable method for producing a consistent-size capsulorrhexis opening in both anterior and posterior capsulorrhexis.

Extensibility and scanning electron microscopy evaluation of 5 pediatric anterior capsulotomy techniques in a porcine model

PURPOSE

To compare the extensibility and scanning electron microscopy (SEM) of 5 currently used pediatric anterior capsulotomy techniques: vitrectorhexis, manual continuous curvilinear capsulorhexis (CCC), can-opener, radio frequency diathermy, and plasma blade in a porcine model.

SETTING

Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

Extensibility was determined by stretching each capsulotomy until it ruptured and measuring it by calculating the mean stretch-to-rupture circumference of each capsulotomy (20 eyes per technique) as a percentage of its baseline circumference. Edge characteristics were evaluated using SEM.

RESULTS

The mean extensibility of each technique tested (vitrectorhexis 161%, CCC 185%, can opener 149%, radio frequency 145%, plasma blade 170%) was significantly different (P<.001, 1-way analysis of variance). The SEM examination found that the vitrectorhexis had a scalloped edge with the whole edge rolled over, presenting a smooth surface toward the inside of the capsulotomy; the manual CCC produced the smoothest edge, with no irregularities noted; the can-opener edge was irregular, showing each puncture of the needle had created a small arc, with occasional regions of the edge rolled over in a "hit-and-miss" fashion; the radio-frequency diathermy capsulotomy edge was ragged, rough, and irregular; and the plasma blade capsulotomy edge was rougher than the manual CCC, but there were fewer irregularities than the radio-frequency diathermy edge had.

CONCLUSIONS

The manual CCC technique produced the most extensible porcine capsulotomy, followed by the plasma blade, vitrectorhexis, can-opener, and radio-frequency techniques, in a porcine model. The manual CCC technique also produced the smoothest anterior capsulotomy edge according SEM evaluation.

Analysis of the capsule edge after Fugo plasma blade capsulotomy, continuous curvilinear capsulorhexis, and can-opener capsulotomy

PURPOSE

To compare the quality of the edges of anterior capsulotomies performed in porcine eyes using 3 different techniques.

SETTING

David J. Apple, MD Laboratories for Ophthalmic Devices Research, John A. Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, USA.

METHODS

Four porcine eyes were submitted to the center in 10% neutral buffered formalin. The cornea of the eyes had been removed, and a continuous capsulotomy had been performed in each eye using the Fugo plasma blade. To provide morphologic correlation, 4 additional porcine eyes were used in the study. In 2, a manual continuous curvilinear capsulorhexis (CCC) was performed after the cornea or cornea/iris was removed and in the other 2, a can-opener capsulotomy (COC) was performed. The eyes were then placed in 10% neutral buffered formalin. Gross (macroscopic) and microscopic analysis of each eye was performed, and photographs were taken. One eye in each group was also prepared and analyzed under scanning electron microscopy (SEM).

RESULTS

The capsulotomy margin in the Fugo blade group presented some regularly spaced tags directed centrally with smooth edges at the base. Such a configuration would not interfere with the dynamics of the capsulorhexis sphincter and would generally not lead to radial tears. The smooth and regular nature of the capsulotomy margin in the CCC group was confirmed by gross and microscopic examinations of the eyes. The capsulotomy margin in the COC group presented some sharp notches directed outward, irregularly spaced, and irregular in shape. These are known to have a tendency to extend and form radial tears.

CONCLUSION

Although performance of an anterior capsulotomy with the Fugo blade was associated with some margin irregularities, the geometry of the centrally directed tags prevented them from becoming the site of radial tear formation. The base of the capsulotomy performed with the Fugo blade appeared to be almost as smooth and regular as in the CCC under SEM evaluation.

Management of the anterior and posterior lens capsules and vitreous in pediatric cataract surgery

PURPOSE

To review and discuss the advantages and disadvantages of various methods of managing anterior and posterior lens capsules and anterior vitreous in pediatric cataract surgery.

METHODS

We reviewed the literature related to pediatric cataract surgery on PubMed and subclassified the subject into subtopics for managing the anterior lens capsule, posterior lens capsule, and anterior vitreous.

RESULTS

After a review of the literature, we summarized the advantages and disadvantages of various approaches related to surgical managements of the anterior lens capsule, posterior lens capsule, and anterior vitreous in pediatric cataract surgery. We discussed recommendations from the literature and commented on our experiences related to the above subtopics.

CONCLUSION

In the surgical management of pediatric cataract, anterior continuous curvilinear capsulorhexis provides the most reliable and tear-resistant capsular opening. Vitrectorhexis and radiofrequency diathermy, on the other hand, are alternative approaches (depending on the surgeon's personal preference). Primary posterior continuous curvilinear capsulorhexis may delay the onset of posterior capsule opacification. Anterior vitrectomy may be necessary to prevent or eliminate the onset of posterior capsule opacification in young children.

Mechanical properties of the human lens capsule

The human lens capsule has recently been the subject of much attention in an attempt to understand its physiological function in relation to the accommodative function, its functional reserve in the elderly population, and its potential in relation to cataract surgery. This overview presents our current knowledge of the mechanical properties of the human lens capsule, discussed on basis of its structure and its role in accommodation and cataract surgery.

[History of the development of intraocular lenses]

Even though cataract surgery has been practiced for over 2000 years, modern cataract surgery started just some 50 years ago. with the first IOL implantation by Sir Harold Ridley. The development of intraocular lenses was accompanied by great successes and disasters. With the fast development of cataract surgical techniques over the past 15 years (ECCE, Phacoemulsification, Capsulorhexis) a successful marriage between IOL-developments and surgery was established. Indication profiles for cataract surgery and IOL implantation extended to more and more patient groups. At this time classical cataract surgery is further developing into refractive intraocular lens surgery to correct higher ametropia in clear lens or phakic eyes. This development was only possible because of the improvements of surgical techniques and implants in classical cataract surgery.

Gentian violet solution for staining the anterior capsule

PURPOSE

To evaluate the histopathological changes after injecting gentian violet solution into the anterior chamber of rats and to describe a technique that uses gentian violet to allow a clear view of the anterior capsule during continuous curvilinear capsulorhexis (CCC) in human eyes with white mature cataract.

SETTING

Department of Ophthalmology, University of Dicle, Diyarbakir, Turkey.

METHODS

In this masked, experimental study (first stage), 0.05 mL of gentian violet 0.01% or 0.001% solution or balanced salt solution (BSS) (control group) was injected into the anterior chamber of 30 eyes of 30 Wistar albino rats. One, 24, and 48 hours after injection, 4 eyes in each group and 2 eyes in the control group were enucleated, and histopathological examination was performed. In the second stage, these solutions were used for staining the anterior capsule in the 18 human eyes with white mature cataract. The success rate of CCC and intraoperative and postoperative complications were evaluated.

RESULTS

Histopathological examination revealed no pathology in any group. A CCC was completed in all cases. No intraoperative or postoperative complications were observed in human eyes except mild corneal edema and mild inflammatory reaction in the anterior chamber that improved within 1 week. Mean follow-up was 3.4 months. Visualization of the anterior capsule was better with gentian violet 0.01% solution.

CONCLUSIONS

Gentian violet solutions at 0.01% and 0.001% concentrations had no evident toxic effect that caused significant histopathological changes. The staining technique was practical and helped the surgeon visualize the anterior capsule. However, gentian violet may have adverse effects that lead to corneal edema.

Capsule contraction after continuous curvilinear capsulorhexis: poly(methyl methacrylate) versus silicone intraocular lenses

PURPOSE

To evaluate the progressive contraction of the anterior capsule opening after in-the-bag implantation of 2 types of intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, University of Brest, Brest, France.

METHODS

In this prospective study, 32 single-piece poly(methyl methacrylate) (PMMA) (Pharmacia 812 C) and 30 3-piece silicone IOLs with PMMA haptics (Allergan SI-40NB) were implanted in the bag after standardized phacoemulsification performed by the same surgeon. All patients were older than 70 years, and none had zonular weakness. The surface of continuous curvilinear capsulorhexis (CCC) was measured 1, 30, and 150 days postoperatively using a 3 charge-coupled device camera and a digitized computer analysis system.

RESULTS

A significant progressive constriction was observed at 150 days in 70% in the silicone group and 32% in the PMMA group. In addition, CCC contraction was greater in silicone group (P < .05). The mean surface decrease was 4.20 mm2 in the silicone group and 1.53 mm2 in the PMMA group. There was no correlation between sex, age, initial capsulorhexis area, final capsule shrinkage. In some eyes, especially in those with a single-piece PMMA IOL (41%), there was no constriction, but fine changes in the capsule opening were seen.

CONCLUSION

Evolutive anterior capsulorhexis modifications were observed in all patients; however, the contraction rate was statistically higher in the silicone group. These results suggest that silicone IOL implantation should be avoided in eyes at risk for CCC constriction.

Prediction of pseudophakic capsular bag diameter based on biometric variables

PURPOSE

To measure the capsular bag diameter (CBDm) in vivo and calculate a regression formula for future preoperative prediction of capsular bag diameter (CBDp).

SETTING

Department of Ophthalmology, University of Vienna, Austria.

METHODS

This prospective study comprised 70 eyes having cataract surgery with implantation of an open capsular tension ring (CTR) (Morcher Type 14). Within the first postoperative days, the distance between the ends of the CTR were measured through a gonioscopy lens by adjusting the slit height. This distance was added to the known length of the CTR to calculate the capsular bag circumference and from this, the CBDm. The CBDm was correlated with axial eye length (AL), corneal power (P), preoperative anterior chamber depth and lens thickness, corneal diameter, and age. A stepwise multiple regression analysis was computed with CBDm as the dependent variable.

RESULTS

The mean CBDm was 10.37 mm +/- 0.25 (SD). A statistically significant negative correlation was found between CBDm and P (P < .0004; r2 = 0.16) and a positive correlation between CBDm and AL (P < .0226, r2 = 0.07). Stepwise multiple regression resulted in the following regression formula: CBDp = 3.44 to 0.056 x P + 0.713 x AL - 0.0135 x AL2 (P < .0001; r2 = 0.3145). Using this formula with the individual Ps and ALs, all 6 eyes with a large capsular bag diameter (CBDm > 10.7 mm) and 10 of 13 eyes with a small one (CBDm < 10.1 mm) were correctly classified.

CONCLUSION

The capsular bag diameter in vivo correlated negatively with corneal power (P) and positively with AL. The regression formula used may serve as a tool for preoperative identification of eyes with a very large or very small CBDm.

Experimental staining of the anterior lens capsule in albino rabbits

PURPOSE

To study the value and safety of staining the anterior lens capsule in albino rabbits.

SETTING

Ophthalmology Department, Cairo University, and Ophthalmic Pathology Department, Research Institute of Ophthalmology, Cairo, Egypt.

METHODS

The experiment was divided into 3 stages. First, the capacity of different concentrations of crystal violet solution to stain the anterior lens capsule of postmortem albino rabbit eyes was tested. The toxicity of different concentrations of the dye (2% to 0.25%) was then tested to determine the highest concentration that was nontoxic to the cornea and trabecular meshwork. The third step was to detect possible toxicity of lower concentrations (0.1% to 0.05%). Different dye concentrations were injected into the anterior chamber of the rabbit eyes. The eyes were examined after 1 and 3 days, 1 week, and 1 month using light microscopy and scanning and transmission electron microscopy.

RESULTS

Different concentrations of crystal violet stained the anterior lens capsule, allowing for easy capsulorhexis. The use of the 2% and 1% concentrations was accompanied with irreversible damage to all corneal layers. The use of the 0.5% concentration caused damage to stromal keratocytes and endothelium. The use of the 0.25% concentration did not damage any corneal layer or the trabecular meshwork. Lower concentrations of 0.1% and 0.05% also stained the capsule, providing good visibility for successful capsulorhexis, and were less toxic to the corneal endothelium.

CONCLUSION

Staining the anterior lens capsule with 0.25% to 0.05% concentrations of crystal violet solution caused no injury to the cornea or trabecular meshwork in albino rabbit eyes.

Relationship between lens and capsular bag size

PURPOSE

To measure the size of the lens and the empty capsular bag and evaluate the relationship between them.

SETTING

Iladevi Cataract & IOL Research Centre, Ahmedabad, India.

METHODS

In 46 eye-bank eyes, the equatorial diameter of the lens was measured after a corneoscleral button and the iris were removed. Empty capsular bag diameter was measured after extracapsular cataract extraction through an intact capsulorhexis.

RESULTS

Mean lens size was 10.20 mm +/- 0.38 (SD) and mean capsular bag size, 10.38 +/- 0.35 mm. The difference between the size of the lens and that of the empty capsular bag varied from 0 to 0.50 mm (mean 0.20 +/- 0.17 mm). Lenses measuring less than 10.25 mm in diameter showed an increase of 0.25 mm while lenses larger than 10.25 mm showed an increase of 0.09 mm.

CONCLUSION

Lens size was larger in our population than in previous studies. The increase in the empty capsular bag size was related to initial lens size.

Compression forces of haptics of selected posterior chamber lenses

PURPOSE

To compare the compressive forces of the haptics of different intraocular lens (IOL) models and analyze the observed differences.

SETTING

Central Hospital of Central Finland and University of Jyväskylä, Jyväskylä, Finland.

METHODS

The haptics of 28 IOL models were compressed to a diameter of 9.0 mm. The compression forces were measured at 0.5 mm intervals. The conclusions were verified by numerical simulations of mechanical models of the lenses.

RESULTS

The measured forces varied between 100 and 601 mg at a diameter of 11.0 mm, 206 and 1057 mg at a diameter of 10.0 mm, and 315 and 2094 mg at a diameter of 9.0 mm. The slopes of the force curves of the three-piece lenses were fairly linear. In general, the three-piece models were less rigid than one-piece models and underwent plastic deformations after repeated compressions. For most one-piece models, compression force increased progressively with increasing compression. The overall IOL diameter and differences in haptic thickness and length and the angle between optic at the point of haptic insertion were the main causes of the observed differences in the compression forces. The variation in forces between individual specimens of the same model, which occurred with almost all models, were mainly the result of variations in haptic thickness.

CONCLUSION

Great variations in the compression forces of the IOL haptics were found. Compression behaviors should be taken into account when selecting a lens to implant.

Clinicopathological findings in human autopsy eyes with an Anis circular lens

PURPOSE

To evaluate the long-term performance of the Anis circular intraocular lens (IOL).

SETTING

Center for IOL Research, Storm Eye Institute, Charleston, South Carolina.

MATERIALS

Fifteen human autopsy eyes with an Anis circular IOL submitted between 1985 and 1993 were evaluated. The eyes were sectioned at the equatorial plane, and the anterior segment containing the capsular bag and the IOL was photographed from the posterior perspective. Fixation, centration, capsular bag shape, zonular damage, central posterior capsule opacification (PCO), and Soemmering's ring formation were analyzed. The results were compared with those of a control group comprising human autopsy eyes with a one-piece (n = 15) or three-piece (n = 15) poly(methyl methacrylate) IOL with a C-loop design.

RESULTS

All 15 Anis IOLs showed symmetrical in-the-bag fixation. Mean decentration in the Anis IOL eyes was significantly lower than in the control eyes (P = .02). Eyes with the Anis IOL had fewer zonular defects (P = .0005) and a better circular extension of the capsular bag (P = .003). There were no statistically significant differences in PCO (P = .29) or Soemmering's ring formation (P = .67).

CONCLUSION

The Anis IOL with a circular haptic design had better centration and capsular bag morphology than the control eyes, although a difference in PCO and Soemmering's ring formation could not be shown.

Experimental study of different intraocular lens designs implanted in the bag after capsulorhexis

OBJECTIVE

To analyze experimentally in cadaver eyes several models of commercially available posterior chamber intraocular lenses (IOLs) to determine their stability, fixation, and behavior in the capsular bag in relation to their overall size, optic diameter, shape, material, and haptic configuration.

SETTING

Eye Bank and Department of Ophthalmology, University General Hospital of Alicante, Spain.

METHODS

Thirty-three IOLs of different sizes, shapes, and designs, divided in two series and five groups, were implanted successively in 31 cadaver eyes. All the proceedings were videotaped, and measurements were made on the television screen with the picture static. Main outcome measures were the diameters of the lens, the empty capsular bag, and the capsulorhexis; capsular distension by the IOL haptics; extent of haptic arc of contact with the capsular equator; and IOL mobility in the bag.

RESULTS

The stability of and stretching caused by the IOLs varied greatly depending on their overall size, haptic flexibility, and the extent of the arc of haptic contact with the capsular equator. Lenses between 13.5 and 14.0 mm had good stability but stretched the capsule excessively. The J-loop haptic configuration produced a spindle-shaped bag deformity that might come in contact with the ciliary processes in the physiologic eye. Among IOLs designed for in-the-bag implantation after capsulorhexis, the two smaller than 12.0 mm were unstable, permitting excessive mobility in the capsular bag. Except for IOLs with a 5.0 mm optic, all 12.0 mm IOLs had reasonable stability, little or no mobility within the capsular bag, and good short-term centering. Lenses with a broad angulation at the haptic-optic junction, to about 90 degrees, achieved the largest arc of contact with the equator and behaved as lenses with larger optics. The Pharmacia 808 performed best.

CONCLUSION

After capsulorhexis and extracapsular cataract extraction, 12.0 mm, poly(methyl methacrylate), one-piece IOLs with modified C-shaped loops, 90 degree angulation at the haptic-optic junction, and an optic diameter between 6.0 and 6.5 mm performed best in the capsular bag.

Posterior capsulorhexis with optic capture in pediatric cataract and intraocular lens surgery

BACKGROUND

A major concern in pediatric intraocular lens implantation surgery is the high incidence of posterior capsule opacification. The purpose of this article is to investigate a surgical technique for maintaining a clear visual axis after pediatric cataract and intraocular lens surgery.

METHODS

In a prospective evaluation, posterior capsulorhexis with optic capture as a surgical technique for preventing secondary membrane formation after pediatric cataract extraction is investigated. This technique involves capture of an intraocular lens optic through a posterior curvilinear capsulorhexis opening. Perioperative complications and incidence of secondary cataract are presented. Results will be compared to an historic cohort of patients with pediatric cataract-intraocular lens who did not have posterior continuous curvilinear capsulorhexis with optic capture.

RESULTS

In 13 consecutive eyes operated on in children aged 2 to 12 years (mean, 5.8 years), there was no opacification of the visual axis at a mean follow-up of 19 months after surgery (range, 8-30 years).

CONCLUSION

Posterior capsulorhexis with optic capture holds promise as a technique for preventing secondary membrane formation. This maneuver ensures centration of the posterior chamber intraocular lens while eliminating the need for an anterior vitrectomy. Apposition of the anterior and posterior capsule leaflets anterior to the optic may limit the migration of Elschnig pearls, reducing the incidence of secondary membranes and the need for additional procedures.

Centration and fixation of posterior chamber intraocular lenses in eyes with pseudoexfoliation syndrome. An analysis of explanted autopsy eyes

Pseudoexfoliation syndrome is an important risk factor in cataract surgery. We examined decentration of posterior chamber intraocular lenses in a series of 24 autopsy eyes with pseudoexfoliation syndrome that had undergone cataract surgery and intraocular lens implantation. The results were compared to a control group of 25 normal autopsy eyes that matched the pseudoexfoliation collection for age distribution, implant duration and further anatomical parameters. The mean lens decentration in all pseudoexfoliation eyes (0.75 +/- 0.38 mm) was significantly higher than in the control group (0.40 +/- 0.29 mm) (p = 0.0008). Analysis of subgroups with symmetrical bag/bag fixated intraocular lenses showed a significantly higher decentration in the pseudoexfoliation group (p = 0.04). The main reason for decentration was a decentration of the entire capsular bag in pseudoexfoliative eyes (p = 0.001), which was related to zonular weakness and damage. The results indicate that in patients with pseudoexfoliation syndrome alternative fixation sites, like sulcus or transscleral fixation, should also be considered.

Mechanized anterior capsulectomy as an alternative to manual capsulorhexis in children undergoing intraocular lens implantation

BACKGROUND

Although manual capsulorhexis is an ideal anterior capsulectomy technique for adults, it is more difficult to perform in very young eyes because the capsular bag is more elastic. Our mechanized anterior capsulectomy technique has compared favorably with manual capsulorhexis in the laboratory using autopsy eyes. We now report the results of circular mechanized anterior capsulectomy in consecutive pediatric patients receiving a posterior chamber intraocular lens (IOL) after cataract extraction.

METHODS

Twenty eyes of 17 consecutive patients between 6 months and 13 years of age underwent a mechanized anterior capsulectomy followed by IOL implantation into the capsular bag. The integrity of the anterior capsular edge was evaluated at the completion of capsulectomy, prior to IOL insertion, and at the end of surgery.

RESULTS

A single radial tear developed in three eyes (15%) of two patients (12%). In the remaining 17 eyes (85%), an intact circular capsulectomy edge was verified at the completion of the mechanized capsulectomy, at the end of IOL insertion, and at the completion of surgery. Complete in-the-bag capsular fixation of the IOL was accomplished in all 20 eyes. Both patients who sustained radial tears were older children (age 11 years). All IOLs remain well centered behind a smooth circular anterior capsular edge after a minimum follow up of 6 months.

CONCLUSION

A mechanized anterior capsulectomy technique can produce a circular capsular opening that resists tearing during lens aspiration and IOL insertion. The vitrector-cut capsulectomy performed well even in the youngest patients in whom manual capsulorhexis would have been difficult to control.

A modified preparation technique for closed-system ocular surgery of human eyes obtained postmortem: an improved research and teaching tool

PURPOSE

In addition to use for corneal transplantation, human autopsy eyes also are used for teaching and vision research. The valuable posterior video technique of Miyake usually is done with an "open-sky" preparation. Closed-system surgery in postmortem eyes is difficult because of postmortem decrease of corneal clarity and myosis. The authors have developed an improved preparation technique that allows closed-system ocular surgery in human postmortem eyes.

METHOD

The cornea is dehydrated using a hyper osmolar (15 percent) dextran solution (Swinger-Kornmehl solution), which clarifies the cornea for several hours. The pupil is dilated mechanically by injecting dextran solution into the anterior chamber, and the iris is fixated using formaldehyde (10 percent) and Karnovsky solution.

RESULTS AND CONCLUSIONS

This technique can be used in autopsy eyes up to 4 days postmortem without other fixation. Incision techniques, capsulorhexis, phacoemulsification, and intraocular lens implantation, as well as other surgical procedures such as glaucoma surgery, transcleral fixation of posterior chamber lenses and vitrectomies, can be performed. Neodymium:YAG laser capsulectomies or other laser surgical procedures are also possible. This technique is not only excellent for residency training and postgraduate wet laboratories, but is also a viable tool for research purposes.

The capsular bag after short- and long-term fixation of intraocular lenses

PURPOSE

To investigate the effect of posterior chamber intraocular lens (PC IOL) size and construction on the capsular bag in human cadaver eyes.

METHODS

Studies were done at two timeframes: (1) short term (prospective)--the effect of 12 different IOLs on the capsular bag configuration after experimental implantation; and (2) long term--(retrospective) analysis of eyes with PC IOLs obtained post-morterm.

RESULTS

The short-term study showed the maximal diameter of the capsular bag to be 11.0 mm for IOLs with total diameter of 12.0 mm and 11.5 mm for 13.5- to 14.0-mm IOLs. Longer IOLs caused more ovaling of the bag with stress lines (striae) on the posterior capsule. Secondary processes such as proliferation of epithelial cells (Soemmering ring) and capsular fibrosis caused the capsular bag to resume a more circular shape with irregular contour. The area of contact between the IOL loops and the capsular equator was significantly lower in eyes with radial tears and IOLs with the J-loop design compared with the C-loop design. In both the short- and long-term groups, maximal capsular diameter did not exceed 12.0 mm.

CONCLUSIONS

The results of this study suggest that using the capsulorrhexis technique, a 12.0-mm total diameter IOL is sufficient to provide stable capsular fixation.

Posterior capsulorhexis with optic capture: maintaining a clear visual axis after pediatric cataract surgery

We describe a technique for preventing secondary membrane formation after pediatric cataract extraction. This technique involves capture of an intraocular lens (IOL) optic through a posterior curvilinear capsulorhexis opening in an attempt to maintain a clear visual axis in children after cataract surgery. This maneuver ensures centration of the posterior chamber IOL because the haptics remain in the capsular bag and the optic is captured in the posterior capsular opening. Also, the need for an anterior vitrectomy may be eliminated. Apposition of the anterior and posterior capsule leaflets anterior to the optic may limit the migration of Elschnig pearls, reducing the incidence of secondary membranes and the need for additional procedures.

Comparison of mechanized anterior capsulectomy and manual continuous capsulorhexis in pediatric eyes

Performing a continuous curvilinear capsulorhexis (CCC) can be more difficult in children than in adults because the capsular bag is more elastic. In this study we compared two capsulectomy techniques in pediatric eyes: creating a mechanized circular anterior capsulectomy using a vitrector and creating a conventional smooth-edged curvilinear tear or CCC using a forceps or needle. We used 18 pairs of eyes (36 eyes) obtained postmortem from children ranging in age from four days to 16 years. The mechanized vitrector-cut capsulectomy was unsuccessful in only one eye (from a 16-year-old child) in which a radial tear developed. Manual CCC was unsuccessful in six eyes, all from children less than five years of age. We conclude that mechanized circular capsulectomy is not only easier to perform in very young eyes than manual CCC, but it is also safe and creates a capsular opening that resists radial tearing. This mechanized technique gives the surgeon an alternative to use in pediatric eyes in which standard manual CCC may be difficult to perform and control.

Intraocular lenses for pediatric implantation: biomaterials, designs, and sizing

Posterior chamber intraocular lenses (IOLs) are being implanted in children with increasing frequency. However, with rare exceptions, only IOLs designed for adults are currently available. These lenses may be difficult to insert into small eyes. Since the pediatric crystalline lens is smaller than that of adults and because the capsular bag does not continue to grow after lensectomy, it is worthwhile to determine the biomaterials, designs, and sizes that may be appropriate for pediatric implantation. In a study of 50 pediatric eyes obtained postmortem, we have documented an estimated growth curve for the developing crystalline lens between birth and 16 years of age. Ninety percent of crystalline lens growth occurs during the first two years of life. Based on these data and this study using the Miyake posterior view analysis of implanted standard and prototype IOLs, we recommend the following: Clinical trials of capsular IOLs, downsized to approximately 10.0 mm diameter, are appropriate for children under two years of age. Capsular IOLs are defined as flexible open-loop, one-piece, all poly(methyl methacrylate), modified C-loop designs made specifically for in-the-bag placement. Because the rapid growth phase of the lens is complete by the age of two, we believe that downsizing the IOL is not necessary after this age unless axial length measurements indicate an unusually small eye. Standard flexible 12.0 mm to 12.5 mm diameter capsular IOLs can be safely implanted. Such lenses could be tolerated throughout life, obviating the need for later IOL exchange.

A comparative study of the elastic properties of continuous tear curvilinear capsulorhexis versus capsulorhexis produced by radiofrequency endodiathermy

Capsulorhexis using radio-frequency endodiathermy may confer some advantages over continuous tear curvilinear capsulorhexis (CTCC) in certain clinical situations. It is unclear whether a capsulorhexis produced in this fashion has the clinically advantageous elasticity and resistance to tearing that a CTCC has been demonstrated to have. To investigate this, a test of capsular elasticity was carried out on pairs of eyes obtained from an eye bank, 42 eyes of 21 patients in total, using modified digital vernier calipers. One eye of each pair had a CTCC, the other a diathermy capsulorhexis (DC). The elasticity of the capsule in both groups was expressed by comparing the circumference of the capsulotomy at rest with its circumference at rupture. The mean capsular elasticity of the CTCC group was significantly greater than that of the DC group (p << 0.001). The capsular edge in both groups was examined using scanning electron microscopy, and the difference in morphology appears to be the source of the difference in elasticity.