New method to measure the retention of viscoelastic agents on a rabbit corneal endothelial cell line after irrigation and aspiration

Thickness of the Protective Layers of Different Ophthalmic Viscosurgical Devices During Lens Surgery in a Porcine Model

Purpose

To evaluate the thickness of the intraoperative layers of 10 different ophthalmic viscosurgical devices (OVD) covering the corneal endothelium during simulated lens surgery in a porcine model.

Methods

This experimental study took place at the Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria. Ten OVDs with different viscoelastic properties (ProVisc, Z-Hyalin plus, Amvisc plus, DisCoVisc, Healon EndoCoat, Viscoat, Z-Hyalcoat, Combivisc, Duo-Visc, and Twinvisc) were assessed in 10 porcine eyes each, yielding a total of 100 eyes. Simulated cataract surgery was performed with volumetric intraoperative OCT imaging during phacoemulsification and during irrigation/aspiration to determine the remaining amount of OVD coating the endothelium over a scan field of 6 × 6 mm. Indirect visualization of the OVD was enabled by replacing the irrigating solution by a higher scattering diluted milk solution. A deep convolutional neural network (CNN) was used to evaluate OVD layer thickness based on the B-scans.

Results

Median thickness values after phacoemulsification were lowest for the cohesive OVDs Z-Hyalin plus (38 µm) and ProVisc (39 µm), followed by the combination systems Twinvisc (342 µm) and Duo-Visc (537 µm). Highest values were observed for the dispersive OVDs and the combination system Combivisc (Viscoat: 957 µm; Z-Hyalcoat: 988 µm, Combivisc: 1042 µm; Amvisc plus: 1259 µm; Healon EndoCoat: 1303 µm; DisCoVisc: 1356 µm). The difference between the OVDs was statistically significant (P < 0.01).

Conclusions

The results of this study confirm that at completion of phacoemulsification, thickest residual layers of OVD remain when using dispersive substances, followed by combination systems and lowest thickness values were observed with cohesive OVDs. The use of an intraoperative OCT and a deep convolutional neural network allowed measurements over a large scan field of 6 × 6 mm and a precise evaluation of the OVD layer coating the corneal endothelium. The OVD layer seemed to be more like a ragged terrain instead of a flat layer, indicating that the film-forming effect of dispersive OVDs is the result of their volume rheology rather than a surface interaction.

Translational Relevance

Evaluating the protective properties provides valuable insights into how different OVDs with different viscoelastic properties form layers beneath the corneal endothelium and helps to understand their persistence during the various steps of cataract surgeries.

New ophthalmic dual-viscoelastic device in cataract surgery: a comparative study

Objective

To compare the performance and safety in cataract surgery of two ophthalmic viscoelastic devices (OVDs), each having separate dispersive and cohesive characteristics and different concentrations.

Methods and analysis

In this prospective, randomised, controlled clinical study, one eye of each patient was injected with OVD1 (Viscopack14) or OVD2 (DuoVisc) during phacoemulsification and intraocular lens implantation. Endothelial cell count, intraocular pressure (IOP), central corneal thickness (CCT), intraocular inflammation and corrected distance visual acuity (CDVA) were compared 3 months postoperatively.

Results

The study enrolled 127 patients. Randomisation assigned 50 eyes of as many patients to each arm of the study. The postoperative mean endothelial cell loss was 14.4% and 7.1% from baseline in the OVD1 and OVD2 groups, respectively (p=0.08). The incidence of IOP spikes at 2 hours was 0% and 8%, respectively (p=0.02). There were intergroup differences in postoperative IOP values, the OVD2 group showed significantly higher values at all of the follow-up visits starting from the 24 hours examination (p<0.05). There was no statistically significant difference in the CCT, intraocular inflammation and CDVA at the end of follow-up.

Conclusion

Both OVDs showed similar clinical performances and were equally effective during cataract surgery. Viscopack14 showed more corneal endothelial cell reduction, while DuoVisc had more occurrences of IOP values and spikes. Future studies are mandatory to support these preliminary results.

Results of endocapsular phacofracture debulking of hard cataracts

Purpose/aim of the study

To present a phacoemulsification technique for hard cataracts and compare postoperative results using two different ultrasonic tip motions during quadrant removal.

Materials and methods

A phacoemulsification technique which employs in situ fracture and endocapsular debulking for hard cataracts is presented. The prospective study included 56 consecutive cases of hard cataract (LOCS III NC [Lens Opacification Classification System III, nuclear color], average 4.26), which were operated using the Infiniti machine and the Partial Kelman tip. Longitudinal tip movement was used for sculpting for all cases which were randomized to receive longitudinal or torsional/interjected longitudinal (Intelligent Phaco [IP]) strategies for quadrant removal. Measurements included cumulative dissipated energy (CDE), 3 months postoperative surgically induced astigmatism (SIA), and corneal endothelial cell density (ECD) losses.

Results

No complications were recorded in any of the cases. Respective overall and longitudinal vs IP means were as follows: CDE, 51.6±15.6 and 55.7±15.5 vs 48.6±15.1; SIA, 0.36±0.2 D and 0.4±0.2 D vs 0.3±0.2 D; and mean ECD loss, 4.1%±10.8% and 5.9%±13.4% vs 2.7%±7.8%. The differences between longitudinal and IP were not significant for any of the three categories.

Conclusion

The endocapsular phacofracture debulking technique is safe and effective for phacoemulsification of hard cataracts using longitudinal or torsional IP strategies for quadrant removal with the Infiniti machine and Partial Kelman tip.

Technology and Intraocular Lenses to Enhance Cataract Surgery Outcomes-Annual Review (January 2013 to January 2014)

PURPOSE

This article is aimed to provide a clinical update on recent developments in cataract surgical techniques, with specific focus on femtosecond laser technology. The article also focuses on recent improvements in the technology used in implanting intraocular lenses (IOLs).

DESIGN

Literature review.

METHODS

The authors conducted a review of literature available in the last 12 months in the English language using PubMed. The period used to conduct the literature search was from January 1, 2013, to December 31, 2013. The following search terms were used during the PubMed search: phacoemulsification, femtosecond laser, toric IOLs, multifocal IOLs, multifocal toric IOLs, manual small-incision cataract surgery, outcomes, surgically induced astigmatism, rotational stability, trifocal IOLs, laser cataract surgery, safety, and efficacy.

RESULTS

This review incorporates selected original articles that provide fresh insights and updates on the fields of toric and multifocal IOLs, femtosecond laser cataract surgery, and manual small-incision cataract surgery. Particular attention has been paid to observational, randomized controlled clinical trials, experimental trials, and analyses of larger cohorts with prospective and retrospective study designs. Letters to the editor, unpublished works, and abstracts do not fall under the purview of this review.

CONCLUSIONS

This review is not designed to be all-inclusive. It highlights and provides insights on literature that is most useful and applicable to practicing ophthalmologists.

Adhesive retention of sodium hyaluronate ophthalmic viscosurgical devices in an acrylic tube model and in porcine-eye corneal endothelium with different irrigation rates

PURPOSE

To evaluate the influence of irrigation rates on the adhesive retention of sodium hyaluronate ophthalmic viscosurgical devices (OVDs) by observation in an acrylic tube system designed to model the epithelial wall and in a porcine-eye experiment.

SETTING

Kohseichuo Hospital, Tokyo, Japan.

METHODS

Commercial sodium hyaluronate OVDs differing in molecular weight were visualized with fluorescein powder. Their adhesive and kinetic characteristics at 2 irrigation rates were visually observed in the acrylic tube model and in a porcine eye under phacoemulsification and aspiration.

RESULTS

In the acrylic tube model, the mean retention time of the low-molecular-weight sodium hyaluronate increased from 2.3 seconds under 78 mL/min irrigation to 27.9 seconds under 45 mL/min irrigation. In the porcine eye, phacoemulsification retention of the same OVD on the corneal endothelial cells was also longer under the low irrigation rate of a 2.2 mm incision than under the higher rate of a 3.5 mm incision.

CONCLUSION

The stable retention of low-molecular-weight sodium hyaluronate in the acrylic tube model at the low irrigation rate corresponded closely with that observed in the porcine eye. This indicates that low-molecular-weight sodium hyaluronate with the low irrigation rates used in procedures such as microincision cataract surgery may effectively protect corneal endothelial cells against surgical risks.

Hydroxyl Radical Scavenging Activity of a New Ophthalmic Viscosurgical Device

PURPOSE

To quantify the hydroxyl radical scavenging activity of a new ophthalmic viscosurgical device (OVD) based on sodium hyaluronate and hydroxypropylmethylcellulose (named VISC28) in comparison with Viscoat, Healon, and Amvisc Plus.

METHODS

The hydroxyl radicals that represent the principal free-radical species generated during phacoemulsification were produced by the Fenton reaction, and the scavenging activity of the tested viscoelastic substances was evaluated in vitro by the 2-deoxy-D-ribose (2-DR) oxidation method that produces the thiobarbituric acid-malondialdehyde (TBA-MDA), complex. An aliquot of viscosurgical formulation was added to phosphate buffer and mixed with 2-DR, Fe2 +/ethylenediaminetetraacetic acid (EDTA), and H2O2. The sample mix was incubated and thiobarbituric acid-trichloroacetic acid solution was added. The sample was then incubated for 30 min, and a chromatographic analysis was performed to quantify the TBA-MDA complex. The data were expressed as micromoles of MDA per milliliter of sample.

RESULTS

All tested OVDs showed a marked hydroxyl radical scavenging activity. The MDA level was significantly lower in VISC28 (0.045 +/- 0.007 micromol/ml) compared with Viscoat (0.070 +/- 0.012 micromol/ ml, p < 0.05), Amvisc Plus (0.111 +/- 0.008 micromol/ml, p < 0.001), and Healon (0.175 +/- 0.016 micromol/ml, p < 0.001). A reduced scavenging activity was shown by VISC28 phosphate-buffered solution (PBS) (no TRIS and no sorbitol) compared with VISC28 (p < 0.001).

CONCLUSIONS

The new OVD, VISC28, showed significantly higher hydroxyl radical inhibition compared with the other viscosurgical formulations. The following rank order for the scavenging activity was established: VISC28 > Viscoat > Amvisc Plus > Healon.

Comparison of the effect of Viscoat and DuoVisc on postoperative intraocular pressure after small-incision cataract surgery

PURPOSE

To evaluate the effect of Viscoat (sodium chondroitin sulfate 4%-sodium hyaluronate 3%) and DuoVisc (Viscoat and Provisc [sodium hyaluronate 1%]) on postoperative intraocular pressure (IOP) after bilateral small-incision cataract surgery.

SETTING

Department of Ophthalmology, University of Vienna, Vienna, Austria.

METHODS

This prospective randomized study comprised 60 eyes of 30 consecutive patients with age-related cataract in both eyes. Each patient's eyes were randomly assigned to receive Viscoat or DuoVisc during cataract surgery. DuoVisc is a packet containing 2 ophthalmic viscosurgical devices (OVDs): the dispersive Viscoat, which was used for intraocular lens (IOL) implantation. In the Viscoat group, the Viscoat was used during the entire surgery. The intraocular pressure (IOP) was measured preoperatively as well as 1, 6, and 20 to 24 hours postoperatively.

RESULTS

One and 6 hours postoperatively, the mean IOP was significantly higher in the Viscoat group than in the DuoVisc group (25.8 mm Hg and 20.5 mm Hg, respectively, at 1 hour and 24.7 mm Hg and 21.1 mm Hg, respectively, at 6 hours) (P<.05). At 20 to 24 hours, the mean IOP was not statistically significantly different between the 2 groups. Intraocular pressure spikes to 30 mm Hg or higher occurred in 4 eyes in the DuoVisc group and 11 eyes in the Viscoat group (P<.05).

CONCLUSIONS

Viscoat caused significantly higher IOP increases and significantly more IOP spikes than DuoVisc in the early postoperative period. Therefore, if Viscoat is used during cataract surgery, an additional cohesive OVD should be used for IOL implantation.

Soft-shell technique using Viscoat and Healon 5: a prospective, randomized comparison between a dispersive-viscoadaptive and a dispersive-cohesive soft-shell technique

PURPOSE

To compare the efficacy of the dispersive-viscoadaptive soft-shell technique using Viscoat and Healon 5 to the dispersive-cohesive soft-shell technique in reducing corneal endothelial cell damage during cataract surgery.

METHODS

In this prospective randomized study, 207 eyes of 171 cataract patients underwent phacoemulsification using the dispersive-viscoadaptive soft-shell technique (V-group, 102 eyes) with Viscoat and Healon5 or the dispersive-cohesive soft-shell technique (C-group, 105 eyes) with Viscoat and a cohesive agent (Opegan-Hi). Each group was divided into two subgroups depending on the amount of ultrasound (%Min) used during phacoemulsification. Corneal endothelial cell density was examined preoperatively and 3 months postoperatively. The endothelial cell loss was compared between the two groups, and also between the subgroups.

RESULTS

The mean endothelial cell loss 3 months after surgery was 8.4 +/- 5.6% standard deviation (SD) in the V-group and 8.2 +/- 6.2% in the C-group (P = 0.787). In the subgroups with ultrasound of 10 %Min or less, the mean endothelial cell loss 3 months after surgery was 6.6 +/- 4.6% in the V-group and 5.5 +/- 5.0% in the C-group (P = 0.104). In the subgroups with ultrasound of over 10 %Min, this value was 10.6 +/- 6.3% in the V-group and 11.9 +/- 5.7% in the C-group (P = 0.413). The correlation coefficient of the endothelial cell loss rate and %Min was 0.245 (P = 0.0129) in the V-group and 0.501 (P < 0.0001) in the C-group.

CONCLUSION

The dispersive-viscoadaptive soft-shell technique is as effective as the dispersive-cohesive soft-shell technique in protecting corneal endothelial cells during phacoemulsification regardless of the amount of ultrasound energy used.

Natural course of intraocular pressure after cataract surgery with sodium hyaluronate 1% versus hydroxypropylmethylcellulose 2%

PURPOSE

To investigate the natural course of intraocular pressure (IOP) after small-incision cataract surgery with sodium hyaluronate 1% versus hydroxypropylmethylcellulose 2%.

DESIGN

Randomized clinical trial.

PARTICIPANTS

Eighty eyes of 40 consecutive patients with bilateral age-related cataract.

METHODS

The patients were assigned randomly to receive sodium hyaluronate 1% or hydroxypropylmethylcellulose 2% during cataract surgery in the first eye. The second eye received the other ophthalmic viscosurgical device. The IOP was measured preoperatively and 30 minutes; 1, 2, 3, 4, 6, 8, and 20 to 24 hours; and 1 week postoperatively.

MAIN OUTCOME MEASURE

Postoperative IOP increase.

RESULTS

The highest mean IOP increase occurred at 8 hours postoperatively (5.3+/-6.4 mmHg) in the sodium hyaluronate 1% group and at 2 hours postoperatively (7.8+/-6.1 mmHg) in the hydroxypropylmethylcellulose 2% group. Overall, the IOP increase was higher with hydroxypropylmethylcellulose 2% (P = 0.005). Intraocular pressure spikes to > or =30 mmHg occurred in 5 eyes (13%) in the sodium hyaluronate 1% group and 13 eyes (33%) in the hydroxypropylmethylcellulose 2% group.

CONCLUSIONS

Sodium hyaluronate 1% and hydroxypropylmethylcellulose 2% caused significant IOP increases during the first 8 hours after cataract surgery. A single measurement at 6 hours postoperatively could detect all IOP spikes in the sodium hyaluronate 1% group. In the hydroxypropylmethylcellulose 2% group, a single measurement at 2 hours postoperatively could detect two thirds of IOP spikes.

The influence of viscoelastic substances on the corneal endothelial cell population during cataract surgery: a prospective study of cohesive and dispersive viscoelastics

PURPOSE

To compare the ability of cohesive and dispersive ophthalmic viscoelastic devices (OVDs) to protect the corneal endothelium following in-the-bag phacoemulsification with implantation of a foldable posterior chamber intraocular lens (IOL).

METHODS

In a prospective single-masked randomized study, 60 eyes of 60 cataract patients were assigned to three groups of 20 patients each, according to which OVD was used: Celoftal, Vitrax or Healon. The corneal response to surgery was evaluated by measuring the endothelial cell loss, the variation in mean cell area of the endothelial cells (CV), the frequency of hexagonal cells, and the central corneal thickness. Data were recorded preoperatively and 3 months postoperatively.

RESULTS

Preoperatively, no significant difference was observed in cell count, CV, hexagonal pattern or pachymetry among groups. Postoperatively, all three groups had a significant decrease in cell count, but the decrease was significantly less in the Vitrax group (6.97%) than in the Celoftal (18.03%) and Healon groups (18.46%). No changes in CV, hexagonality or corneal thickness were observed within any of the three groups or among the groups. There was an equal and significant increase in visual acuity.

CONCLUSIONS

Phacoemulsification with implantation of a posterior chamber lens is known to affect the density and morphology of corneal endothelial cells. Viscoelastics facilitate cataract surgery and protect the corneal endothelium during the procedure. Choosing a dispersive hyaluronate OVD during the phaco procedure may allow for protection of the endothelial cells while suppressing the formation of free radicals. This may be the reason for the superior protective effect on the corneal endothelial cells of Vitrax compared with Celoftal and Healon.

In vitro behavior of ophthalmic viscosurgical devices during phacoemulsification

PURPOSE

To evaluate the behavior and aspiration of several ophthalmic viscosurgical devices (OVDs) during phacoemulsification.

SETTING

Department of Ophthalmology, Tokyo Dental College Suidobashi Hospital, Tokyo, Japan.

METHODS

Cohesive OVDs (sodium hyaluronate 1.0% [Healon and Provisc]), dispersive OVDs (sodium hyaluronate 3.0%-chondroitin sulfate 4.0% [Viscoat]), and new-generation OVDs such as viscoadaptive (sodium hyaluronate 2.3% [Healon5]) and viscodispersive (hyaluronic acid 1.65%-chondroitin sulfate 4.0% [DisCoVisc]) OVDs, were stained with fluorescein sodium. The movement of the OVDs during simulated cataract surgery was recorded in porcine eyes under an operating microscope and with a side-view video camera. The initial and complete aspiration times of each OVD during phacoemulsification using 20 and 40 mL/min flow rates and sleeves and the removal times using the irrigation and aspiration (I/A) tip at the end of surgery were evaluated from the recorded videos.

RESULTS

The complete aspiration time of the cohesive OVDs was less than 3 seconds but up to 20 seconds with a low flow rate of 20 mL/min with a smaller sleeve. Other OVDs remained in the anterior chamber during phacoemulsification with both flow rates. The removal time for cohesive OVDs was less than 4 seconds and for new-generation OVDs, 10 to 15 seconds. The dispersive OVD required a significantly (P<.05) longer removal time than other OVDs.

CONCLUSIONS

Cohesive OVDs are removed easily during phacoemulsification; however, the aspiration rate can be affected by fluidics. New-generation OVDs, such as Healon5 and DisCoVisc, remained in the anterior chamber during phacoemulsification and were removed easily by I/A at the end of surgery. The behavior of these OVDs is preferable during phacoemulsification.

Retention and removal of a new viscous dispersive ophthalmic viscosurgical device during cataract surgery in animal eyes

AIMS

To assess the retention and removal properties of a new viscous dispersive ophthalmic viscosurgical device (OVD), DisCoVisc, in comparison with those of cohesive (Provisc), dispersive (Viscoat), and viscoadaptive (Healon5) OVDs.

METHODS

In 20 porcine eyes, cataract surgery was simulated using one of the four OVDs which were stained with fluorescein for better visualisation. Three parameters were measured. Firstly, the presence/absence of OVDs in the chamber at the completion of phacoemulsification was recorded. Secondly, the time until the OVDs were completely removed from the anterior chamber using the phaco needle was measured. Thirdly, after intraocular lens (IOL) implantation, the time needed to completely remove the OVDs from the chamber with irrigation/aspiration tip was recorded.

RESULTS

At the completion of phacoemulsification, the OVDs retained in 0% (0/5) for Provisc, 80% (4/5) for Healon5, 100% (5/5) for DisCoVisc, and 100% (5/5) for Viscoat. The retention of OVDs during phacoemulsification was greatest with Viscoat followed by, in descending order, DisCoVisc, Healon5, and Provisc. The removal of OVDs after IOL implantation took longest with Viscoat followed by Healon5, DisCoVisc, and Provisc.

CONCLUSION

The viscous dispersive DisCoVisc showed excellent retention during phacoemulsification, while its removal after IOL implantation was very easy. When compared with the viscoadaptive Healon5, DisCoVisc was retained better in the chamber and was easier to remove. These features of DisCoVisc should be highly advantageous when considering covering the entire cataract surgery procedure with a single OVD.

Quantitative assessment of ophthalmic viscosurgical device retention using in vivo confocal microscopy

PURPOSE

To develop and apply a new laboratory method for in vivo quantitative assessment of the retention of ophthalmic viscosurgical devices (OVDs) following phacoemulsification.

SETTING

Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.

METHODS

Studies of both eyes of New Zealand White rabbits were performed. Six OVDs were evaluated: Provisc and Healon (both sodium hyaluronate 1%), Healon5 (sodium hyaluronate 2.3%), Amvisc Plus (sodium hyaluronate 1.6%), Viscoat (sodium hyaluronate 3%-chondroitin sulfate 4%), and a new viscous-dispersive OVD, DisCoVisc (sodium hyaluronate 3%-chondroitin sulfate 4%). The OVD was injected to fill the anterior chamber and a phacoemulsification needle inserted with the tip positioned just anterior to the lens capsule. Simulated phacoemulsification was performed for 1 minute using flow rates of 20, 40, and 60 mL/min; a vacuum level of 300 mm Hg; and ultrasound power of 60% using a Legacy phacoemulsification unit. The needle was removed, and silicone oil (1000 centistokes) was injected into the anterior chamber. The distance between the corneal endothelium and the OVD-silicone oil interface was measured using in vivo confocal microscopy through-focusing (CMTF).

RESULTS

Significant differences in residual thickness were found between the OVDs tested. Specifically, the residual thickness of both DisCoVisc (mean 324.5 microm +/- 163.7 [SD]) and Viscoat (251.4 +/- 100.9 microm) was significantly greater than that of Provisc (9.5 +/- 16.7 microm), Healon (3.8 +/- 11.3 microm), Healon5 (0.6 +/- 2.4 microm), and Amvisc Plus (65.6 +/- 134.0 microm) (P < .05, Dunn test). Ophthalmic viscosurgical device retention was greatest with DisCoVisc; however, there was no statistically significant difference between DisCoVisc and Viscoat in residual thickness. The flow rate did not have a significant effect on the residual thickness (Friedman 2-way analysis of variance by ranks).

CONCLUSIONS

Residual OVD thickness following simulated phacoemulsification could be quantitatively measured using in vivo CMTF. The results are consistent with human surgical experience in that the dispersive OVD (Viscoat) was better retained than the cohesive compounds. DisCoVisc, a new viscous-dispersive OVD, also showed retention compared with Viscoat under the experimental conditions.

Natural Course of Intraocular Pressure after Cataract Surgery with Sodium Chondroitin Sulfate 4%–Sodium Hyaluronate 3% (Viscoat)

PURPOSE

To investigate the natural course of intraocular pressure (IOP) and its peak after small-incision cataract surgery with chondroitin sulfate 4%-sodium hyaluronate 3% (Viscoat, Alcon Laboratories, Inc., Fort Worth, TX).

DESIGN

Observational case series.

PARTICIPANTS

This prospective study comprised 40 eyes of 40 consecutive cataract patients scheduled for small-incision cataract surgery.

METHODS

Cataract surgery was performed with sodium chondroitin sulfate 4%-sodium hyaluronate 3% as the ophthalmic viscosurgical device, which was removed as completely as possible from the eye at the end of surgery. The IOP was measured preoperatively and 30 minutes; 1, 2, 3, 4, 6, 8, and 20 to 24 hours; and 1 week postoperatively.

MAIN OUTCOME MEASURES

Postoperative IOP increase.

RESULTS

The mean IOP increased significantly at all observation times during the first 20 to 24 hours, with a peak increase of 13.4+/-9.4 mmHg after 1 hour (P<0.05). In all, 28 eyes (70%) had an IOP spike to 30 mmHg or higher. Sixty-eight percent of these spikes occurred at 30 minutes as well as at 1 hour and 2 hours postoperatively. At 20 to 24 hours, no eye had an IOP spike to 30 mmHg or higher.

CONCLUSIONS

Significant IOP increases were found during the first 24 hours, peaking at 1 hour after surgery. With a single postoperative IOP measurement, between 30 minutes and 2 hours after surgery, two thirds of these IOP spikes could be detected. To detect all IOP spikes, a second measurement between 4 and 6 hours after surgery would be necessary.

Free radical development in phacoemulsification cataract surgery

Phacoemulsification and aspiration (PEA) has become the most popular cataract surgery, due to the establishment of safe surgical techniques and development of associated instruments. However, corneal endothelial damage still represents a serious complication, as excessive damage can lead to irreversible bullous keratopathy. In addition to causes such as mechanical or heat injuries, free radical formation due to ultrasound has been posited as another cause of corneal endothelium damage in PEA. Ultrasound in aqueous solution induces cavitation, directly causing water molecule disintegration and resulting in the formation of hydroxylradicals, the most potent of the reactive oxygen species. Considering the oxidative insult to endothelial cells caused by free radicals, their presence in the anterior chamber may represent one of the most harmful factors during these procedures. Indeed, some researchers have recently started to evaluate PEA from the perspective of oxidative stress. Conversely, the major ingredient in ophthalmic viscosurgical devices (OVDs), which are indispensable for maintaining the anterior chamber in PEA surgery, is sodium hyaluronate, a known free radical scavenger. OVDs can thus be expected to provide some anti-free radical effect during PEA procedures. In addition, since commercially available OVDs display different properties regarding retention in the anterior chamber during PEA, the anti-free radical effect of OVDs is likely to depend on behavior during irrigation and aspiration. The present study followed standard PEA procedures in an eye model and measured hydroxylradicals in the anterior chamber using electron spin resonance. The kinetics of free radical intensity and effects of several OVDs during clinical PEA were also demonstrated. These studies may be of significance in re-evaluating OVDs as a chemical protectant for corneal endothelium, since the OVD has thus far only been regarded as a physical barrier. In addition, many reports about corneal endothelium damage during PEA have been published, but objective evaluation of various damaging factors has been difficult. The present assay of free radicals in a simulation of clinical PEA offers the first method to quantitatively assess stress on the corneal endothelium.

Effect of a fixed dorzolamide–timolol combination on intraocular pressure after small-incision cataract surgery with Viscoat

PURPOSE

To evaluate the effect of a fixed dorzolamide-timolol combination (Cosopt) on intraocular pressure (IOP) after small-incision cataract surgery with sodium chondroitin sulfate 4%-sodium hyaluronate 3% (Viscoat).

SETTING

Department of Ophthalmology, University of Vienna, Vienna, Austria.

METHODS

This prospective randomized study comprised 76 eyes of 38 patients scheduled for small-incision cataract surgery in both eyes. Patients were randomized to receive 1 drop of the fixed dorzolamide-timolol combination in 1 eye or no treatment (control) immediately after cataract surgery. The fellow eye received the other assigned treatment. Cataract surgery was performed with Viscoat in an identical fashion in both eyes. The IOP was measured preoperatively and 6 hours, 20 to 24 hours, and 1 week postoperatively.

RESULTS

Six hours after surgery, the mean increase in IOP was significantly lower in the dorzolamide-timolol group than in the control group (4.3 mm Hg +/- 5.6 [SD] versus 8.4 +/- 6.1 mm Hg; P =.003). Two eyes in the dorzolamide-timolol group and 9 in the control group had IOP spikes of 30 mm Hg or higher (P =.022). Twenty to 24 hours after surgery, the mean IOP change was -2.6 +/- 3.3 mm Hg in the dorzolamide-timolol group and 1.5 +/- 3.2 mm Hg in the control group (P<.001).

CONCLUSIONS

The fixed dorzolamide-timolol combination was effective in reducing IOP 6 hours and 20 to 24 hours after cataract surgery. However, it did not prevent Viscoat-induced IOP spikes of 30 mm Hg or higher.

Experimental study of viscoelastic in the prevention of corneal endothelial desiccation injury from vitreal fluid-air exchange

PURPOSE

To evaluate the usefulness of viscoelastic in protecting the corneal endothelium from desiccation injury associated with fluid-air exchange in a rabbit model.

DESIGN

Experimental study.

METHODS

Rabbit eyes undergoing pars plana lensectomy and vitrectomy were insufflated with either dry or humidified air for 20 minutes following introduction of either Opegan (sodium hyaluronate 1.0%; Santen, Osaka, Japan) or Viscoat (sodium hyaluronate 3%-chondroitin sulfate 4%; Alcon, Tokyo, Japan) into the anterior chamber. In two other groups of rabbit eyes, the same procedure was performed without using any viscoelastic agent. Corneas obtained from rabbits undergoing surgery were compared with corneas obtained from rabbits not undergoing surgery. Potential alterations in the corneal endothelium were investigated by scanning electron microscopy, by Phalloidin-FITC staining of actin and by in vitro measurements of corneal permeability for carboxyfluorescein using a diffusion chamber.

RESULTS

Scanning electron microscopy displayed less distortion of corneal endothelium with Opegan and Viscoat compared with the dry air-only exposed corneas. Using humidified air in Opegan and Viscoat coated corneas maintained the normal actin cytoskeleton during fluid-air exchange. Paracellular leakage was much less with Opegan and Viscoat use following infusion of dry air comparing to that of dry air-only group (P =.026 and P =.041). The difference was much more striking following humidified air infusion in Opegan or Viscoat coated corneas comparing to dry air-only infused corneas (P <.002 and P <.002).

CONCLUSIONS

Coating of rabbit corneal endothelium with Opegan or Viscoat before fluid-air exchange largely prevents dry air damage to the endothelium. Infusion of humidified air further protects corneal endothelium during fluid-air exchange in aphakic rabbit eyes.

Corneal endothelial cell protection with a dispersive viscoelastic material and an irrigating solution during phacoemulsification: low-cost versus expensive combination

PURPOSE

To evaluate the protective effect on corneal endothelial cells of a low-cost and an expensive combination of a dispersive viscoelastic material and an irrigating solution during phacoemulsification.

SETTING

Department of Ophthalmology, University of Vienna, Vienna, Austria.

METHODS

This prospective randomized examiner- and patient-masked study comprised 90 eyes of 45 consecutive patients with age-related cataract in both eyes. For each patient, the first eye was randomly assigned to receive hydroxypropyl methylcellulose 2% (Ocucoat) and Ringer's solution (low-cost combination) or sodium chondroitin sulfate 4%-sodium hyaluronate 3% (Viscoat) and an enriched balanced salt solution (BSS Plus) (expensive combination) during phacoemulsification. The contralateral eye received the other treatment. Endothelial cell function was evaluated by measuring corneal thickness (CT) using partial coherence interferometry, morphology assessment, and endothelial cell counts.

RESULTS

The acute postoperative increase in CT was +9.8 microm in the low-cost group and +10.9 microm in the expensive group; the difference between groups was not significant. After 1 month, the CT still differed significantly from baseline in the low-cost group. Three months after surgery, the CT had returned to baseline values in both groups. There was no significant between-group difference in endothelial cell counts or morphology.

CONCLUSIONS

During phacoemulsification in a nonselected patient population, there was no difference in acute postoperative corneal edema and endothelial cell morphology after 3 months between a Viscoat and BSS Plus combination and an Ocucoat and Ringer's solution combination. Eyes receiving the expensive combination had marginally faster recovery of corneal swelling by 3 months. However, the cost of Viscoat and 500 mL BSS Plus is 5 times that of Ocucoat and Ringer's solution.

Scheimpflug photography study of ophthalmic viscosurgical devices during simulated cataract surgery

PURPOSE

To evaluate by Scheimpflug photography the capacity of several commercially available ophthalmic viscosurgical devices (OVDs) to remain in the anterior chamber and maintain anterior chamber depth (ACD) during simulated cataract surgery in porcine cadaver eyes.

SETTING

Department of Preclinical Ophthalmology, Pharmacia & Upjohn AB, Uppsala, Sweden.

METHODS

Eighty eyes from newly slaughtered pigs were used. They were distributed equally among 8 OVDs: Amvisc Plus (sodium hyaluronate 1.6%), Biolon (sodium hyaluronate 1.0%), Biolon Prime (sodium hyaluronate 1.2%), Healon (sodium hyaluronate 1.0%), Healon GV (sodium hyaluronate 1.4%), Healon5 (sodium hyaluronate 2.3%), Provisc (sodium hyaluronate 1.0%), and Viscoat (sodium hyaluronate 3.0%-chondroitin sulfate 4.0%). Scheimpflug photographs were taken using a Nidek EAS-1000 instrument before surgery (control), after injection of the OVD, after continuous curvilinear capsulorhexis (CCC), and after lens extraction by phacoemulsification. Differences in the ACD with a P value less than 0.05 were considered statistically significant. The retention capacity was visually assessed.

RESULTS

Healon5 had a significantly higher capacity to maintain the ACD than the other OVDs after CCC and phacoemulsification. After injection, Healon5, Viscoat, and Biolon Prime showed similar ACD-maintaining capacities.

CONCLUSIONS

The capacity of Healon5 to maintain the ACD during cataract surgery, ie, neutralizing the vitreous pressure and stabilizing the anterior segment of the eye, was significantly higher than that of the other OVDs.

Viscoelastic protection from endothelial damage by air bubbles

PURPOSE

To determine whether viscoelastic materials effectively protect the corneal endothelium from air bubbles.

SETTING

Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.

METHODS

Human eye-bank and rabbit eyes had a standardized phacoemulsification procedure with or without viscoelastic material (Healon [sodium hyaluronate 1.0%], Healon GV [sodium hyaluronate 1.4%], or Viscoat [chondroitin sulfate 4.0%-sodium hyaluronate 3.0%]). The integrity of the endothelium was examined after the procedure with F-actin staining and scanning electron microscopy. Rabbit eyes with and without viscoelastic material (Healon or Viscoat) had a standardized irrigation/aspiration (I/A) procedure. The mucinous layer of the endothelium was examined after the procedure with transmission electron microscopy.

RESULTS

In the phacoemulsification experiment without viscoelastic material, with Healon, and with Healon GV, the endothelium of human and rabbit corneas had many areas of cell loss in a pattern consistent with air-bubble damage. With Viscoat, endothelial cells remained intact. In the I/A experiment, the mucinous layer of Viscoat-exposed rabbit endothelium appeared thinner. In the same experiments without viscoelastic material or with Healon, the mucinous layer of the endothelium appeared normal.

CONCLUSIONS

Viscoat effectively protected the endothelium from air-bubble damage. Viscoat appears to protect the endothelium by acting as a physical barrier. Its adherence is probably related to the way it interacts with the mucinous layer of the endothelium.

Intraocular pressure after bilateral cataract surgery using Healon, Healon5, and Healon GV

PURPOSE

To determine whether there is a difference in frequency or severity of postoperative intraocular pressure (IOP) spikes after bilateral phacoemulsification with complete ophthalmic viscosurgical device (OVD) removal when Healon5 (sodium hyaluronate 2.3%), Healon (sodium hyaluronate 1%), or Healon GV (sodium hyaluronate 1.4%) is used.

SETTING

York Finch Eye Associates and Humber River Regional Hospital, Toronto, Ontario, Canada.

METHODS

Bilateral cataract surgery was performed in 99 patients; 50 were randomly assigned to receive Healon5 in 1 eye and Healon GV in the fellow eye and 49, Healon in 1 eye and Healon GV in the fellow eye. The IOP was measured preoperatively as well as 5 and 24 hours and 7 days postoperatively. The mean IOP and standard deviation at each time interval were calculated for each OVD. The results were compared among the OVDs using Student t tests for each time at which IOP was assessed.

RESULTS

There were no significant differences in postoperative IOP spikes among the Healon5, Healon, and Healon GV groups; however, patients receiving lower viscosity OVDs had a lower mean IOP at 24 hours. All groups had increased IOP at 5 and 24 hours and reduced IOP at 7 days.

CONCLUSIONS

Within a family of molecularly similar OVDs, lower viscosity OVDs appear to cause slightly lower mean elevations in IOP in normal patients at 24 hours. However, if the OVD is removed, postoperative IOP spikes above 21 mm Hg appear related more to patient factors (eg, predisposition in glaucoma patients) and surgically induced trauma than to the specific long-chain non-cross-linked hyaluronan OVD used.

Anterior capsule dyes and labeled viscoelastic solutions to enhance contrast in EAS-1000 Scheimpflug images

PURPOSE

To enhance contrast in images produced by the EAS-1000 to facilitate evaluation of the rheological properties of viscoelastic substances during simulated cataract surgery.

SETTING

Department of Preclinical Ophthalmology, Scientific Affairs, Pharmacia AB, Uppsala, Sweden.

METHODS

Cataract surgery was performed in 200 fresh porcine cadaver eyes and documented by EAS-1000 Scheimpflug photography. The light scattering caused by anterior capsule dyes, labeled irrigation solutions, and labeled viscoelastic solutions was statistically analyzed in the images.

RESULTS

Visualization by light scattering was significantly enhanced by a fluorescein labeled viscoelastic solution and by an eosin-Y- or phloxine-B-dyed capsule (P < .05). A side effect of eosin Y and phloxine B was that the capsule became fragile, making it difficult to perform a continuous curvilinear capsulorhexis.

CONCLUSIONS

Fluorescein-labeled viscoelastic solutions are recommended to enhance contrast in the images when retention capacity is evaluated. Light scattering from capsule dyeing facilitated anterior chamber depth measurements in the images.

Anterior chamber depth estimation by Scheimpflug photography

PURPOSE

To obtain a model suitable for evaluation of the anterior chamber depth (ACD) maintaining capacity of viscoelastic substances--a critical parameter in cataract surgery.

METHODS

ACD was estimated using an anterior segment analysis system (EAS-1000, Nidek Co Ltd, Japan). Variation was studied as an effect of batch number and eye within batch, storage, globe fixation, globe position, and repeated analyses of Scheimpflug images.

RESULTS

Considerable variation in ACD was found between eyes, batches, and as a result of prolonged storage (biological factors). Different IOPs before surgery caused significant alterations in ACD after overfilling with a viscoelastic substance. No significant differences were found when the globe position was altered or when the ACD was re-estimated repeatedly from the same photograph.

CONCLUSION

Differences due to biological factors are more important than methodological errors caused by the Scheimpflug instrument. To reduce these variations when viscoelastics are evaluated, all measurements should be calculated as % of ACD before surgery and the anterior chamber should be overfilled with a viscoelastic solution.

Intraocular pressure rise after small incision cataract surgery: a randomised intraindividual comparison of two dispersive viscoelastic agents

AIM

To evaluate the effects of the dispersive viscoelastic agents Ocucoat (hydroxypropyl methylcellulose 2%) and Viscoat (sodium chondroitin sulphate 4%-sodium hyaluronate 3%) on postoperative intraocular pressure (IOP) after bilateral small incision cataract surgery.

METHODS

This prospective, randomised study comprised 80 eyes of 40 consecutive patients with age related cataract in both eyes scheduled for bilateral small incision cataract surgery. The patients were randomly assigned to receive Ocucoat or Viscoat during cataract surgery of the first eye. The second eye was operated later and received the other viscoelastic agent. Cataract surgery was performed with a temporal 3.2 mm sutureless posterior limbal incision, phacoemulsification, and implantation of a foldable silicone intraocular lens. The IOP was measured preoperatively as well as 6 hours, 20-24 hours, and 1 week postoperatively.

RESULTS

At 6 hours after surgery the mean IOP increased by 4.6 (SD 5.1) mm Hg in the Ocucoat group (p<0.001) and by 8.6 (8.1) mm Hg in the Viscoat group (p<0.001). The increase was significantly higher in the Viscoat group than in the Ocucoat group (p=0.004). Intraocular pressure spikes of 30 mm Hg or more occurred in two eyes in the Ocucoat and in nine eyes in the Viscoat group (p=0.023); 20-24 hours and 1 week postoperatively the mean IOP was not statistically different.

CONCLUSION

These findings indicate that Viscoat causes a significantly higher IOP increase and significantly more IOP spikes than Ocucoat in the early period after small incision cataract surgery.

Intraocular pressure after small incision cataract surgery with Healon5 and Viscoat

PURPOSE

To evaluate the effect of Healon5 (sodium hyaluronate) and Viscoat (sodium chondroitin sulfate-sodium hyaluronate) on intraocular pressure (IOP) after bilateral small incision cataract surgery.

SETTING

Department of Ophthalmology, University of Vienna, Vienna, Austria.

METHODS

This prospective randomized study comprised 70 eyes of 35 consecutive patients with age-related cataract in both eyes scheduled for bilateral small incision cataract surgery. The patients were randomly assigned to receive Healon5 or Viscoat during cataract surgery in the first eye. The second eye received the other viscoelastic substance. Cataract surgery was performed in an identical fashion in both eyes, with a temporal 3.5 mm sutureless posterior limbal incision, phacoemulsification, and implantation of a foldable silicone intraocular lens. The IOP was measured preoperatively and 6 hours, 20 to 24 hours, and 1 week postoperatively.

RESULTS

At 6 hours after surgery, the mean IOP increased by 5.2 mm Hg +/- 5.3 (SD) in the Healon5 group (P < .0001) and by 10.1 +/- 8.7 mm Hg in the Viscoat group (P < .0001). The increase was significantly higher in the Viscoat group than in the Healon5 group (P = .0016). Intraocular pressure spikes of 30 mm Hg or more occurred in 2 eyes in the Healon5 group and in 10 eyes in the Viscoat group (P = .0112). Twenty to 24 hours and 1 week postoperatively, the mean IOP in the 2 groups was not statistically different.

CONCLUSIONS

Viscoat caused a significantly higher IOP increase and significantly more IOP spikes than Healon5 in the early period after small incision cataract surgery.

Randomized clinical comparison of Healon GV and Viscoat

PURPOSE

To compare the ability of Healon GV (sodium hyaluronate 1.4%) and Viscoat (sodium chondroitin sulfate 4.0%-sodium hyaluronate 3.0%) to protect the corneal endothelium during endocapsular phacoemulsification and foldable intraocular lens (IOL) implantation.

SETTING

A small ophthalmology group practice.

METHODS

One hundred forty patients were randomized, 70 per group, in a prospective, partially masked study of cataract surgery using Healon GV or Viscoat. One ophthalmologist performed all surgery. Primary outcome variables were the 2 week postoperative changes in corneal thickness, endothelial cell density, mean endothelial cell size, and endothelial cell hexagonality. Several secondary variables were measured, and an analysis of the statistical power of the study was performed.

RESULTS

There were no statistically significant differences between groups in terms of age (P = .856), cataract density (P = .117), preoperative best corrected visual acuity (BCVA) (P = .892), postoperative BCVA (P = .969), amount of viscoelastic material used during surgery (P = .444), amount of irrigating solution used (P = .125), or phacoemulsification time (P = .088). It took longer to remove the Viscoat than the Healon GV (P < .001), and total operating time for the Viscoat group was longer (P < .001). Two weeks after surgery, there were no significant differences between groups in corneal thickness (P = .362), endothelial cell density (P = .351), or mean endothelial cell size (P = .610). However, Viscoat preserved the hexagonal shape of endothelial cells slightly better than Healon GV (P = .043). The study had sufficient power to detect clinically significant differences in corneal thickness, endothelial cell density, and endothelial cell size.

CONCLUSIONS

Healon GV and Viscoat were comparable in their ability to protect the corneal endothelium during endocapsular phacoemulsification and foldable IOL implantation. Results may vary, however, if phacoemulsification is performed anterior to the iris plane.

Dispersive-cohesive viscoelastic soft shell technique

Based on their physical properties, ophthalmic viscoelastic agents can be divided into 2 groups: higher-viscosity cohesive and lower-viscosity dispersive. Higher-viscosity cohesive agents are best at creating and preserving space, while lower-viscosity dispersive agents are retained better in the anterior chamber and are capable of partitioning spaces. The viscoelastic soft shell technique maximizes the advantages and minimizes the disadvantages of both groups by using dispersive and cohesive agents together in sequence based on the desired surgical goal.

Quantitative method to determine the cohesion of viscoelastic agents by dynamic aspiration

PURPOSE

To quantitatively determine the cohesion of ophthalmic viscoelastic agents using an in vitro method based on dynamic aspiration kinetics.

SETTING

Alcon Laboratories, Inc., Fort Worth, Texas, USA.

METHOD

Five viscoelastic agents were tested: Healon GV (sodium hyaluronate 1.4%); Provisc (sodium hyaluronate 1.0%); Healon (sodium hyaluronate 1.0%); Amvisc Plus (sodium hyaluronate 1.6%); Viscoat (sodium hyaluronate 3.0%-chondroitin sulfate 4.0%). Samples were placed into a tared polypropylene container using a positive displacement pipette. Calibrated vacuum was applied for 2 seconds to a polypropylene tip (inner diameter 0.5 mm) lowered into the viscoelastic sample. The quantity of viscoelastic agent remaining in the container after aspiration was determined gravimetrically. The procedure was repeated at various vacuum levels between 100 and 700 mm Hg. The percentage of viscoelastic agent aspirated was plotted against vacuum pressure. The slopes of these curves indicate the relative cohesion of the viscoelastic sample.

RESULTS

The cohesion-dispersion indices (percentage viscoelastic agent aspirated/100 mm Hg) were Healon GV (72.3) > Provisc (46.0) > Healon (31.2) = Amvisc Plus (21.4) > Viscoat (3.4).

CONCLUSION

The method provided a quantitative basis for the clinical classification of viscoelastic materials as cohesive or dispersive. The aspiration kinetics profile (curve shape), maximum rate of removal, and vacuum levels at which the bolus removal of the viscoelastic agent started (break point) were useful in characterizing the viscoelastic agents. Because the results agree with the clinical impression of cohesion/dispersion, this method may be used to predict the surgical performance of viscoelastic agents.