Strength of the lens capsule during hydroexpression of the nucleus

Adjusted femtosecond laser capsulotomy distance in white cataracts to decrease incomplete capsulotomy: a randomized comparative cohort study

BACKGROUND

To compare safety and effectiveness between standard position and adjusted distance pre- and post-anterior capsule of femtosecond laser capsulotomy in white cataracts surgery.

METHODS

Selected white cataracts that underwent LenSx femtosecond laser capsulotomy were randomized into groups A (standard position, with 300 µm symmetrically pre- and post-anterior capsule), B (increased distance with 400 µm symmetrically pre- and post-anterior capsule), and C (unsymmetrical distances of 200 µm pre- and 400 µm post-anterior capsule, respectively). All these surgeries were performed by the same experienced surgeon. Complications, including incomplete capsulotomy and capsule tears, were recorded. In addition, femtosecond capsulotomy and phacoemulsification parameters, IOLs centrality and corrected distance visual acuity were assessed.

RESULTS

A total of 113 eyes were included in this study. There were 8 (21.6%) incomplete capsulotomy and 1 anterior capsule tear in group A. Meanwhile, only 2 eyes (5.1%) had incomplete capsulotomy with none showing capsule tear in group B. In group C, only 1 eye (2.7%) had incomplete capsulotomy and no capsule tear occurred. Mean femtosecond laser capsulotomy time was longer in group B compared with groups A and C. Average cumulative dispersed energy, IOL centrality and corrected distance visual acuity were similar in all groups.

CONCLUSIONS

Appropriate adjustment on femtosecond laser capsulotomy distance by reducing pre-anterior capsule and increasing post-anterior distance, may decrease incomplete capsulotomy and be more effective in white cataracts surgery.

TRIAL REGISTRATION

Clinical trial registration number: ChiCTR2100043863.

Thermal capsulotomy: Initial clinical experience, intraoperative performance, safety, and early postoperative outcomes of precision pulse capsulotomy technology

PURPOSE

To assess the clinical safety and performance of a new thermal capsulotomy device in patients having cataract surgery.

SETTING

Launceston Eye Institute, Launceston, Tasmania, Australia.

DESIGN

Prospective case series.

METHODS

This single-surgeon consecutive series comprised eyes having capsulotomy with a precision pulse capsulotomy (PPC) device (Zepto). Baseline demographic information and preoperative, intraoperative, and early postoperative outcomes, including complications, intraocular pressure (IOP), flare photometry, corneal and retinal thickness, and specular microscopy were collected and analyzed. Outcomes included PPC performance, intraoperative complications, effective phacoemulsification time, IOP, postoperative inflammation, corneal edema, endothelial cell density, functional evaluation of the corneal endothelium, retinal thickness, cost-effectiveness, and early postoperative visual acuity.

RESULTS

The study evaluated 100 eyes. Complete free-floating capsulotomy was achieved in 70 eyes (72%). Focal attachments were identified in 17 eyes (18%) and broad attachments in 10 eyes (10%). Intended PPC capsulotomy failed in 3 eyes due to operator or device error. Anterior capsule tears occurred in 4 eyes (4%); otherwise, there were no significant safety signals in the early postoperative period. There was no evidence of a learning curve effect; however, use of a dispersive ophthalmic viscosurgical device (OVD) is postulated as influencing capsulotomy completeness.

CONCLUSIONS

The PPC device created round, reproducible, appropriately sized capsulotomies in 72% of eyes. The incidence of incomplete capsulotomy and radial tear rate was high and was possibly associated with the use of a dispersive OVD.

Prevention and Management of Posterior Capsule Rupture

PURPOSE

To present the means and technique used in our Department for prevention and management of posterior capsule rupture during planned extracapsular cataract extraction.

METHODS

Prospective analysis of 550 extracapsular cataract operations from October 1993 to March 1994. Our technique (a slight modification of Blumenthal's technique) included a triplanar watertight small scleral incision, a relatively large continuous curvilinear capsulorhexis, or can-opener capsulotomy, nucleus hydrodissection and hydroexpression, use of an anterior chamber maintainer and residual cortex removal through a 10 o'clock side-port corneal incision.

RESULTS

Best corrected postoperative visual acuity ranged from 7-10/10 in 93.45% of our cases. Posterior capsule rupture with or without vitreous loss occurred in 1.63% and 2.72% of the cases, respectively. These rates are much lower than those, observed, when we used the sclerocorneal incision and nucleus extraction with external pressure.

CONCLUSIONS

The combination of a triplanar watertight small scleral incision. A relatively large continuous curvilinear capsulorhexis, an anterior chamber maintainer and residual cortex aspiration through the 10 o'clock side-port corneal incision greatly reduced the posterior capsule rupture rate.

Ultrastructural Integrity of Human Capsulotomies Created by a Thermal Device

PURPOSE

To investigate the ultrastructural features of anterior capsulotomy performed with a thermal device, the precision pulse capsulotomy (PPC).

DESIGN

Prospective, multicenter case series.

PARTICIPANTS

Consecutive patients undergoing capsulotomy with the PPC device.

METHODS

Prospective study of patients undergoing capsulotomy with the PPC by 2 surgeons, followed up by routine phacoemulsification cataract surgery, was undertaken. All capsulotomy specimens were collected for scanning electron microscopy (SEM). Observations were made regarding uniformity of the capsular edge and the presence of irregularities that may compromise integrity. Comparisons were made with manual continuous curvilinear capsulorrhexis.

MAIN OUTCOME MEASURES

Ultrastructural features of PPC and presence of irregularities.

RESULTS

Frayed appearance of the anterior capsule edge was noted in postoperative visits under slit-lamp examination. Scanning electron microscopy sampling showed a generally uniform rolled capsular edge, but interspersed with areas of irregularity with frayed appearance at the capsule margin.

CONCLUSIONS

The PPC device is capable of creating reproducible, central, and precise circular capsulotomy. The ultrastructural features in ex vivo human capsulotomy specimens generally show eversion of the capsulotomy edge, but in some cases, this was accompanied by areas of irregular capsule margin with frayed edges, likely caused by dissipated thermal energy. The postoperative appearance and SEM features warrant further assessment of the PPC integrity and clinical correlation.

AN ADVANCED CATARACT SURGERY BY PHACOEMULSIFICATION: AN INITIAL EXPERIENCE

Phacoemulsification surgery is rapidly emerging as accepted latest surgical technique for the management of cataract. Retrospective analysis of first fifty cases of phacoemulsification surgery performed in our setup were critically evaluated to assess efficacy and adaptability of this procedure in Armed Forces setup. Results of initial twenty five cases were compared qualitatively with subsequent cases. Equipment settings, operative constraints, post-operative complications, effects on induced astigmatism, visual outcome and patient's rehabilitation were critically evaluated. Corneal striate, iris chaffing, posterior capsular rent were noted initial problems. Induced astigmatism was ranging between 0.5 to 1.0 Dioptre with early decay and complete stabilisation within four weeks. Inspite of excellent visual outcome, complex technique, steep and long learning curve restricts its application to institutional setup.

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.

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.

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.

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.

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.

The lens capsule

The lens capsule is a modified basement membrane that completely surrounds the ocular lens. It is known that this extracellular matrix is important for both the structure and biomechanics of the lens in addition to providing informational cues to maintain lens cell phenotype. This review covers the development and structure of the lens capsule, lens diseases associated with mutations in extracellular matrix genes and the role of the capsule in lens function including those proposed for visual accommodation, selective permeability to infectious agents, and cell signaling.

Multiaxial mechanical behavior of the porcine anterior lens capsule

The biomechanics of the lens capsule of the eye is important both in physiologic processes such as accommodation and clinical treatments such as cataract surgery. Although the lens capsule experiences multiaxial stresses in vivo, there have been no measurements of its multiaxial properties or possible regional heterogeneities. Rather all prior mechanical data have come from 1-D pressure-volume or uniaxial force-length tests. Here, we report a new experimental approach to study in situ the regional, multiaxial mechanical behavior of the lens capsule. Moreover, we report multiaxial data suggesting that the porcine anterior lens capsule exhibits a typical nonlinear pseudo-elastic behavior over finite strains, that the in situ state is pre-stressed multi-axially, and that the meridional and circumferential directions are principal directions of strain, which is nearly equi-biaxial at the pole but less so towards the equator. Such data are fundamental to much needed constitutive formulations.

Resistance of the human posterior lens capsule and zonules to disruption

PURPOSE

To determine the resistance of the human posterior lens capsule and zonules to disruption during cataract surgery.

SETTING

Wet lab at Walkergate Hospital, Newcastle upon Tyne, England.

METHOD

Human donor eyes were obtained after removal of a corneoscleral disc. Lens extraction was performed by an extracapsular technique leaving an intact capsular bag. The resistance of the zonules and posterior capsule to disruption by aspiration was measured in each eye, and the resistance of the zonules to damage from direct mechanical stretch was determined.

RESULTS

Posterior capsules tolerated a median suction pressure of 200 mm Hg (range 150 to 300 mm Hg) before disruption. Values for female eyes were slightly greater than for male; no significant correlation with age was shown. The zonular fibers tolerated a median suction pressure of 200 mm Hg (range 150 to 300 mm Hg). The median mechanical zonular stretch tolerance was 3.00 mm (range 2.75 to 4.00 mm). No significant correlation was found between zonular suction tolerance or stretch tolerance and sex or between suction tolerance and age, but a negative relationship was noted between maximum tolerated stretch and age.

CONCLUSION

Setting the maximum aspiration pressure during irrigation/aspiration to 150 mm Hg should help prevent capsular or zonular rupture. If more powerful aspiration is required, it should be used with great care so as not to engage the capsule.

Tensile strength of lens capsules in eye-bank eyes

PURPOSE

To measure the tensile strength of the anterior and posterior lens capsules in eye-bank eyes and study the tensile strength of capsules dehydrated with hypertonic glucose solution.

SETTING

Tongren Hospital, Beijing, China.

METHODS

The in situ anterior and posterior capsules of 35 eye-bank eyes (Group 1) donated by healthy men aged 20 to 40 years (mean 27.1 years) were measured with a biomembrane strength device. Sixteen eyes (Group 2), from donors aged 20 to 37 years (mean 27.0 years) and similar to those in Group 1, were measured in the same way after the anterior and posterior capsules were exposed to glucose 50% solution for 15 minutes.

RESULTS

In Group 1, anterior and posterior capsule strength was 6.269 +/- 1.118 and 3.755 +/- 0.835 g, respectively (P < .01), and the correlation between the tensile strength of the anterior and posterior capsules was statistically significant (r = .94; P < .001). In Group 2, the strength of the capsules increased to 9.024 +/- 0.586 and 4.424 +/- 0.761 g, respectively, a finding that was statistically significantly different from that in Group 1 (P < .01 and .05, respectively.

CONCLUSION

The tensile strength of the anterior capsule was stronger than that of the posterior capsule under the experimental conditions. Glucose 50% solution has the potential to increase the tensile strength of anterior and posterior capsules.

Extracapsular cataract surgery using capsulorhexis with viscoexpression via a limbal section

Two hundred consecutive patients had extracapsular cataract surgery by capsulorhexis and viscoexpression. Capsulorhexis, attempted in 195 eyes, was successful in 87.7%. Viscoexpression was attempted in 162 cases and successfully delivered the nucleus in 87.7%. There were five cases of zonule rupture, one of posterior capsule rupture, and two of vitreous loss. If the capsulorhexis is larger than 5 mm, viscoexpression can be safely used on all cataracts, regardless of nuclear density, and is the ideal transition to phacoemulsification.

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.

Hydroexpression and viscoexpression of the nucleus through a continuous circular capsulorhexis

When a continuous circular capsulorhexis (CCC) is performed, conventional nucleus expression may be impossible because of the strong capsular rim. Hydroexpression of the nucleus seems to overcome the problem if the capsulorhexis opening is large enough. Because a viscoelastic material may be an even more gentle tool than balanced salt solution (BSS), hydroexpression and viscoexpression were evaluated in 16 pairs of human cadaver eyes. The diameter of the capsulorhexis opening ranged from 4 mm to 6 mm; it was the same in each pair of eyes. Hydroexpression was performed in one eye using BSS and viscoexpression was performed in the fellow eye using sodium hyaluronate (Healon Yellow). The fluid pressure in the capsular bag was measured during both procedures. The pressure was higher during hydroexpression than during viscoexpression. The pressure difference between fellow eyes ranged from 0 to 32 mm Hg and was most marked when the CCC opening was small. This correlation was significant (P < .05). Viscoexpression may enhance the safety in cases with a small CCC opening or in those that are otherwise difficult.