Cohesive Ophthalmic Viscosurgical Device Research Articles

Application of thermoreversible hydrogel (poloxamer 407) to protect the corneal endothelium during phacoemulsification in porcine and rabbit eyes

To evaluate the effectiveness of thermoreversible (poloxamer) hydrogels as a substitute for ophthalmic viscosurgical devices (OVDs) during phacoemulsification in porcine and rabbit eyes and compare their endothelial protective effect with that of hyaluronic acid-based OVDs. Department of Ophthalmology, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul, South Korea. Experimental study. Fluorescein-stained poloxamer hydrogels (20%, 22%, 24%, and 26% [weight/weight%]) and cohesive (sodium hyaluronate 1.0% [Provisc]) and dispersive (sodium hyaluronate 3.0%-chondroitin sulfate 4.0% [Viscoat]) OVDs were injected into the anterior chamber of porcine eyes incubated at 32°C. In the invitro study, the retention time was measured in 3 groups of 45 porcine eyes during continuous phacoemulsification. In the invivo study, the endothelial cell count (ECC) was measured before and 3days after intermittent phacoemulsification in 12 rabbit eyes randomized to a poloxamer hydrogel or a dispersive OVD group. The optimum concentration of thermosensitive hydrogel was 26%, at which no gel-to-sol phase transition occurred in the anterior chamber, with a 21°C irrigation solution. In the invitro study, the mean retention times were 5.53seconds±1.77 (SD), 125.00±29.34seconds, and 221.53±42.48seconds in the cohesive OVD, dispersive OVD, and 26% poloxamer hydrogel groups, respectively (P<.001). Throughout the 5-minute intermittent phacoemulsification, the 26% poloxamer hydrogel remained in the anterior chamber as a semisolid gel. In the invivo study, the mean decrease in ECC was significantly lower in the 26% poloxamer hydrogel group than in the dispersive OVD group (P=.029). Thermoreversible hydrogels might be suitable substitutes for hyaluronic acid-based OVDs for corneal endothelial protection during phacoemulsification.

Comparison of Floaters after Cataract Surgery with Different Viscoelastics.

Purpose: To investigate whether there is a difference between symptoms of floaters according to the type of ophthalmic viscosurgical devices(OVDs) used during phacoemulsification. Methods: A total of 112 eyes had undergone standard phacosurgery with the dispersive OVDs(Group1). Group2 comprised 117 eyes that underwent phacosurgery with the dispersive OVDs, but between continuous curvilinear capsulorhexis and hydrodissection, some OVDs had been removed. Group3 included 120 eyes that had undergone phacosurgery with the cohesive OVDs. Results: 14 eyes (12.5%) of Group1 had new-onset floater after surgery whereas 6 eyes (5.13%) in Group2, and 7 eyes (5.83%) in Group3 at the day after and a week after surgery. This was significantly higher in Group1 than Group2 and Group3, respectively (p=0.047,0.049). Conclusion: Cataract surgery with dispersive OVD can predispose the eye to an increased floater symptom. Therefore, surgeons should consider release some OVDs during hydrodissection with dispersive viscoelastics and keep trying to avoid IOP surge during surgery.

Lens decompression technique for prevention of intraoperative complications during phacoemulsification of intumescent cataract.

Purpose:To evaluate intraoperative complications during phacoemulsification of intumescent cataract using lens decompression technique.Methods:Participants with intumescent cataract scheduled for phacoemulsification were recruited and divided into two groups. In both groups, after the anterior capsule was stained with trypan blue, the anterior chamber was filled peripherally with a dispersive ophthalmic viscosurgical device (OVD) followed centrally by a higher viscosity cohesive OVD (Healon GV). In Group 2, a 25-gauge needle was then inserted into the lens center and liquid cortex aspirated by pulling back on the syringe plunger. The outcomes measured were the incidence of capsular radial tears and the incidence of conversion to extracapsular cataract extraction (ECCE).Results:In Group 1 (20 eyes), capsular radial tears occurred in four eyes, and in two eyes, the procedure had to be converted to ECCE. In Group 2 (20 eyes), no capsular radial tears or conversion to ECCE was reported.Conclusion:Lens decompression technique reduced the risk of capsular radial tears and conversion to ECCE during phacoemulsification of intumescent cataract.

Mixed polymeric systems: New ophthalmic viscosurgical device created by mixing commercially available devices

To evaluate the rheological properties of mixtures of different commercially available ophthalmic viscosurgical devices (OVDs) containing sodium hyaluronate and chondroitin sulfate. Eye Clinic, University of Trieste, Trieste, Italy. Laboratory study. Blends were obtained combining a superviscous cohesive OVD (Healon GV [sodium hyaluronate 1%]) and a medium-viscosity dispersive OVD (Viscoat [sodium hyaluronate 3.0%-chondroitin sulfate 4.0%]). The 2 substances were combined in different ratios, and the rheological characteristics were analyzed to find the optimum proportion. A new viscous dispersive OVD, Discovisc (hyaluronic acid 1.6%-chondroitin sulfate 4.0%) was evaluated for comparison. The storage modulus, loss modulus, crossover point, complex viscosity, shear viscosity, and pseudoplasticity were studied. The rheological properties of the mixed solution (1:1 and 3:1) showed intermediate characteristics in comparison with the 2 original substances, characterized by a viscosity comparable to that of the superviscous cohesive OVD, but at a higher shear rate (similar to the medium-viscosity dispersive OVD). The new viscous dispersive OVD performed similarly to the medium-viscosity dispersive OVD at low shear rates but was comparable to the superviscous cohesive OVD at high shear rates. The mixture of dispersive and cohesive rheological properties in a single OVD might be an advantage during cataract surgery.

Prefilled syringes and usability of ophthalmic viscosurgical devices.

PurposeTo examine the influence of the configuration of prefilled syringes on the usability of ophthalmic viscosurgical devices (OVDs).SettingDepartment of Ophthalmology, Jikei University School of Medicine, Tokyo, Japan.DesignExperimental study.MethodsThe maximum force needed to extrude the whole OVD (extrusion force) was compared among viscous cohesive OVDs (OPEGAN Hi® 0.85 mL and Healon® 0.85 mL) and very low viscosity dispersive OVDs (OPEGAN® 0.6 mL and OPEGAN® 1.1 mL). Additionally, to exclude the influence of any differences between syringes of viscous cohesive OVDs on the extrusion force, empty syringes of the same configuration were refilled with the same products. In addition, the syringe inner surface and that of the piston attached to the tip of the plunger were measured.ResultsThe extrusion force of Healon 0.85 mL (3.28±0.19 kgf) was significantly (P<0.01) higher than that of OPEGAN Hi 0.85 mL (2.54±0.23 kgf). The inner syringe chamber for Healon 0.85 mL was vial shaped and had a built-in needle in the Luer tip, which was clearly different from OPEGAN Hi 0.85 mL. There were no significant differences in the extrusion force between refilled syringes. The extrusion force of OPEGAN 1.1 mL (3.44±0.12 kgf) was significantly (P<0.01) higher than that of OPEGAN 0.6 mL (1.63±0.06 kgf). The syringe of OPEGAN 1.1 mL was obviously bigger than that of OPEGAN 0.6 mL.ConclusionIt was confirmed that the configuration of the syringes is another determinant of the extrusion force and a factor related to the difference in usability among products that meet the same cohesive class.

Tri-soft shell technique

Soft-shell techniques exist for lower viscosity dispersive with higher viscosity cohesive ophthalmic viscosurgical devices (OVDs) (soft-shell technique [SST]), viscoadaptive OVDs with balanced salt solution (ultimate soft-shell technique), intraoperative floppy-iris syndrome (soft-shell bridge), and many specific modifications for disinserted zonular fibers, frayed iris strands, Fuchs endothelial dystrophy, small holes in the posterior capsule with protruding vitreous, capsular dye use, and others. Soft-shell techniques exist because it is rheologically impossible to control the surgical environment with a single OVD as well as with an ordered combination of rheologically different OVDs. Surgeons frequently confuse these techniques because of their multitude. This paper unifies all SSTs into a single improved tri-soft shell technique (TSST), from which basic specific applications to unusual circumstances are simple and intuitive. As shown with previous SSTs, the TSST allows surgeons to perform complex tasks with greater surgical facility and to protect endothelial cells better than with single OVDs.

Enlarging the Big-Bubble During Deep Anterior Lamellar Keratoplasty

During big-bubble deep anterior lamellar keratoplasty, a bubble that is not large enough can be formed. Further air injection can result in the rupture of the posterior lamella, necessitating conversion to penetrating keratoplasty. We describe some techniques to safely enlarge the big-bubble in such a circumstance. In cases in which a white-margin bubble forms that has extended to the trephination margin, the bubble is collapsed and the margins are extended by blunt dissection. For cases of an undersized clear-margin bubble, the bubble is enlarged by gentle injection of a cohesive ophthalmic viscosurgical device into the bubble cavity. Using these techniques, big-bubbles were safely extended beyond the trephination margin for both white- and clear-margin bubbles. An undersized big-bubble can safely be extended using blunt dissection for white-margin bubbles and ophthalmic viscosurgical device injection for clear-margin bubbles.

Evaluation of Intraocular Reactivity to Organic Contaminants of Ophthalmic Devices in a Rabbit Model

To evaluate the intraocular reactivity to organic contaminants of ophthalmic devices in the rabbit. Experimental animal study. Fifty New Zealand white rabbits. The rabbits were allocated to 10 groups of 5 each to receive 2 different doses of human albumin and nonhuman nucleic acids and their respective vehicle controls, a denatured cohesive ophthalmic viscosurgical device (OVD) and a denatured dispersive OVD and their respective nondenatured controls. All 10 eyes in each treatment group received bilateral intracameral injection of the test materials. All the eyes in the study were examined by slit-lamp biomicroscopy at baseline and 6, 9, 24, 48, and 72 hours. Pachymetry was also performed on eyes exposed to albumin, protein vehicle control, and the OVDs at these time points. Corneal thickness, grade of corneal clouding, anterior chamber (AC), cells, flare and fibrin, iridal hyperemia, cell and fibrin on lens surface, and onset time. There were no inflammatory signs in any eyes exposed to human albumin. Anterior chamber cells (1+ to 3+) and flare and fibrin (1+ to 2+), along with cells and fibrin on the lens surface, were seen in the eyes exposed to the nucleic acid samples, and they resolved in 24 hours. Mild (mostly 1+) conjunctival congestion, cells, flare, and fibrin were seen in a few eyes exposed to the 2 denatured OVDs and their controls, with the response durations being shorter in the denatured OVD eyes (24 hours) than in the nondenatured OVD eyes (48 hours). Anterior chamber inflammation was generally observed in fewer denatured OVD eyes than in nondenatured OVD eyes, particularly the dispersive OVD eyes. Intracameral injection of human albumin protein did not cause ocular inflammation. Nucleic acid intracamerally injected into rabbit eyes caused acute inflammation that quickly resolved. Cohesive and dispersive OVD denatured by drying and steam sterilization alone did not cause ocular inflammation.

Rabbit Ocular Reactivity to Bacterial Endotoxin Contained in Aqueous Solution and Ophthalmic Viscosurgical Devices

To describe the ocular reactivity of the rabbit to bacterial endotoxin contained in an aqueous medium and in a cohesive and a dispersive ophthalmic viscosurgical device (OVD). Experimental, randomized animal study. Seventy-five New Zealand white rabbits. This study was performed using 75 rabbits to evaluate the ocular reactivity to bacterial endotoxin contained in Dulbecco's phosphate-buffered saline (DPBS), a cohesive OVD, and a dispersive OVD. For each test material, 25 rabbits were randomized into 5 groups and were exposed to the test material containing 0.75 endotoxin units (EU), 0.25 EU, 0.08 EU, and 0.02 EU of endotoxin or the vehicle control. The rabbits in each group received bilateral intracameral injection of 0.05 ml of the same test material. All eyes were examined by slit-lamp biomicroscopy at baseline, 3, 6, 9, 24, 48, and 72 hours after injection. At 24 and 72 hours, slit-lamp biomicroscopy (and additionally indirect ophthalmoscopy) was performed through dilated pupils. Corneal clouding, anterior chamber (AC) flare, cells and fibrin, vitreous haze and cells, cells and fibrin on lens surface, lens opacities, and onset time. The inflammation seen after exposure to the 3 endotoxin-spiked materials followed the same general time course. Anterior chamber cells, flare, iris hyperemia, and conjunctival congestion were seen as early as 3 hours. They started to diminish after 6 hours (DPBS eyes) and 9 hours (OVDs) and were not detectable at 48 and 72 hours, respectively. The AC inflammation was more severe in the OVD eyes than in the DPBS eyes. Anterior chamber fibrin was seen in the OVD eyes only, which persisted through 72 hours in many eyes. A trend toward a dose-response relationship was seen for AC cells and flare and the presence of cells and fibrin on the lens surface in all 3 treatment groups in the first 24 hours. Inflammation was seen after intracameral injection of as little as 0.02 and 0.08 EU in OVD and DPBS eyes, respectively. Observed responses to intracamerally injected endotoxin in OVDs were more severe and of longer duration than those in aqueous medium.

Central thickening of the donor posterior corneal disc in femtosecond-laser-assisted Descemet’s stripping endothelial keratoplasty

A 49-year-old man complained of progressive visual disturbance oculus dexter (OD), which commenced 1 year earlier. He had undergone cataract extraction OD 20 years earlier and presented with recurrent uveitis over the 5 years before his latest presentation. Best corrected visual acuity (BCVA) OD was 20/100 and intraocular pressure (IOP) was 16 mmHg. Slit-lamp microscopy showed a superiorly distorted iris, aphakia, diffuse corneal edema, and Descemet’s folds. Aphakic bullous keratopathy was diagnosed, and FS-DSEK with secondary intraocular lens (IOL) sulcus fixation was planned. Institutional review board approval and the patient’s written informed consent were obtained. FS laser (60 kHz IntraLase; Abbott Medical Optics, Inc., Santa Ana, CA, USA) was used to prepare a deep horizontal lamellar interface in the donor cornea. The donor corneoscleral rim was placed in a Barron artificial anterior chamber (Katena Products, Inc., Denville, NJ, USA). The pressure in the artificial anterior chamber was assessed by palpation and titrated by controlling irrigation solutions. Intraoperative pachymetry measured the central thickness of the donor cornea as 560 lm. The raster spot pattern was used. Raster energy level of 1.8 lJ was employed to prepare for a horizontal lamellar cut at an intended depth of 390 lm. With the patient under retrobulbar anesthesia, cohesive ophthalmic viscosurgical devices (OVDs) were inserted through the recipient paracentesis site to maintain the anterior chamber. Through a 2.75-mm limbal incision at 9 o’clock of the limbus, a ?11.0 D three-piece IOL (Sensar AR40E, Abbott Medical Optics) was inserted into the anterior chamber and transsclerally sutured with 10-0 Prolene employing the ab externo approach [2]. The target refraction of the inserted IOL was emmetropic. An 8.0-mm-diameter circle of Descemet’s membrane and endothelium was stripped from the recipient cornea using a Price-Sinskey hook (Moria Inc., Doylestown, PA, USA). A 9.0-mm-diameter DPCD was inserted into the anterior chamber through a 5.5-mm limbal incision, and the end of the 10-0 nylon suture was pulled through the paracentesis site. Filtered air bubbles were injected into the recipient anterior chamber and pressed against the DPCD for 10 min. Two months postoperatively, uncorrected visual acuity (UCVA) was 20/400 OD, and the IOP was 17 mmHg OD. J. Y. Kim K.-H. Kim M. J. Kim H. Tchah Department of Ophthalmology, University of Ulsan College of Medicine, Asan Medical Center, 388-1 Pungnap-2dong, Songpa-gu, Seoul 138-736, Republic of Korea

Rotational Stability of a Single-Piece Hydrophobic Acrylic Intraocular Lens During Removal of Ophthalmic Viscosurgical Devices

To compare the effect of cohesive and dispersive ophthalmic viscosurgical device (OVD) on intraoperative rotational stability of the intraocular lens (IOL) with single-piece hydrophobic acrylate platform. Prospective, comparative study. This institutional clinical study included 60 eyes of 60 patients who underwent phacoemulsifcation. The patients were equally divided into cohesive OVD (Healon GV; Abbott Medical Optics, Abbott Park, Illinois, USA) group and dispersive OVD (Viscoat; Alcon Laboratories, Fort Worth, Texas, USA) group. Image analysis from the captured digital image was used to measure intraoperative rotation of single-piece hydrophobic acrylate IOL (SA60AT or SA60NT) during OVD removal. Mean intraoperative rotation was 7.42 degrees +/- 4.16 (standard deviation) in dispersive OVD group and 13.08 degrees +/- 5.25 (standard deviation) in cohesive OVD group (P < .001). Twenty-one cases (70%) maintained the alignment within 10 degrees during removal of OVD with dispersive OVD, while only 9 cases (30%) did so with cohesive OVD (P = .005). Counterclockwise rotation was observed in 33% of the all cases. This study showed that a significant amount of IOL rotation occurred during OVD removal. Intraoperative rotational stability of IOL was greater with Viscoat than with Healon GV.

Viscoanaesthesia in cataract surgery: a prospective, randomized clinical trial

We aimed to compare viscoanaesthesia (VisThesia) with intracameral lidocaine in cataract surgery carried out under topical anaesthesia. In this prospective study 98 patients were randomly assigned to receive VisThesia (group 1, n = 49) or 0.5 cc of 1% unpreserved lidocaine (group 2, n = 49). All surgery was carried out by one surgeon using clear corneal technique. Pachymetry, the status of the cornea and anterior chamber, and intraocular pressure (IOP) were checked pre- and postoperatively. Mean pain scores were 0.12 (maximum: 3) in group 1 and 0.37 in group 2; the difference between the groups was not statistically significant (95% confidence interval [CI] 0.003-0.487; p = 0.05). A total of 48 patients in group 1 (98%) and 49 in group 2 (100%) reported no discomfort or only mild discomfort. No significant differences in flare and cells in the anterior chamber or IOP were found between the two study groups. There was a significantly greater frequency of corneal oedema in group 1 (p = 0.001). Postoperative central corneal thickness values were also significantly higher in group 1 (95% CI 11.64-57.24; p = 0.003). Results suggest that viscoanaesthesia provides a level of comfort during cataract surgery under topical anaesthesia similar to that facilitated by intracameral lidocaine. However, patients who are given viscoanaesthesia may have increased risk for postoperative corneal oedema.

Comparison of the corneal endothelial protective effects of Healon‐D and Viscoat

The use of dispersive ophthalmic viscosurgical devices (OVDs) has been shown to provide significant protection against air bubble damage to the corneal endothelium when compared with cohesive OVDs. We compared the corneal endothelial protective effects of a new dispersive OVD, Healon-D, with Viscoat. Healon-D and Viscoat were used in a randomized and masked fashion in the anterior chamber of 40 rabbit eyes during a procedure where ultrasound at 70% continuous energy was delivered for 2 min. Two millilitres of air bubbles were injected into the anterior chamber during the first minute of the procedure on each eye. Corneas were then stained with trypan blue and alizarin red and evaluated via light microscopy for endothelial injury. Both denuding of the endothelial layer, as well as damage to endothelial cells were quantified by using the Evaluation of Posterior Capsule Opacification digital imaging system. The denuded area for eyes treated with Healon-D and Viscoat were not significantly different (medians of 0.004167and 0.003333, respectively, P = 0.8908). There was no significant difference in the area of endothelial cell damaged (medians of 0.02183 and 0.01433, respectively, P = 0.4565). When the denuded and damaged areas were calculated together, there was also no difference in the total injured area (medians of 0.05817 and 0.05821, respectively, P = 0.5740). The new dispersive OVD Healon-D is equally as effective as Viscoat in protecting the corneal endothelial layer from denuding and damage from air bubbles during anterior segment surgery.

Effect of a new cohesive ophthalmic viscosurgical device on corneal protection and intraocular pressure in small-incision cataract surgery

To compare the corneal protective and intraocular pressure (IOP) effects of a new cohesive ophthalmic viscosurgical (OVD), Neocrom Cohesive (sodium hyaluronate 1.4%), with those of Healon (sodium hyaluronate 1.0%) in cataract surgery. Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. This randomized patient-masked examiner-masked study with fellow-eye comparison comprised 29 cataract surgery patients. Surgery was performed with Neocrom Cohesive in 1 eye and Healon in the other eye. Central corneal thickness (CCT) was measured preoperatively and 1 day and 3 months postoperatively; endothelial cell density (ECD), preoperatively and 3 months postoperatively; and IOP, preoperatively and 6 hours and 1 day postoperatively. The mean CCT change from preoperatively to postoperatively in the Neocrom Cohesive, respectively, group and Healon group was +16.0 microm +/- 25.7 (SD) (P<.01) and +7.0 +/- 17.1 microm (P<.05), respectively, at 1 day and -5.7 +/- 10.8 microm (P<.01) and -4.7 microm +/- 9.5 microm) (P<.01), respectively, at 3 months. The mean ECD change at 3 months was 8 +/- 155 cells/mm(2) in the Neocrom Cohesive group (P = .8) and -46 +/- 139 cells/mm(2) in the Healon group (P = .08). The mean IOP increase was +2.2 +/- 3.5 mm Hg (P<.01) and +1.4 +/- 4.2 mm Hg (P = .14), respectively, 6 hours postoperatively and +0.9 +/- 4.3 mm Hg (P = .37) and 0.0 +/- 3.5 mm Hg (P = .77), respectively, at 1 day. There was no significant difference between Neocrom Cohesive and Healon in the changes in CCT, ECD, and IOP after cataract surgery.

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

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

Effects of Topical Dorzolamide on IOP after Phacoemulsification with Different Types of Ophthalmic Viscosurgical Devices

To evaluate the effect of topical dorzolamide on postoperative intraocular pressure (IOP) after routine phacoemulsification surgery with different type of ophthalmic viscosurgical device (OVD). Patients who were scheduled for phacoemulsification with intraocular lens (IOL) implantation were evenly divided into four groups. Group I (83 eyes) received one drop of topical dorzolamide immediately after surgery and 1.4% NaHa (BD Visc) was used as a cohesive OVD during IOL implantation. Group II (83 eyes) did not receive any topical antiglaucoma medication after operation and 1.4% NaHa was used as a cohesive OVD. Group III (83 eyes) received topical dorzolamide and 1% NaHa (Healon) was used, and Group IV (83 eyes) did not receive any topical and 1% NaHa was used in operation. Mean postoperative IOPs were compared between groups. Eyes with 1.4% NaHa usage (18.2+/-9.2 mmHg) had higher mean postoperative IOPs than eyes with 1% NaHa usage (15.5+/-5.3 mmHg) (p=0.002). Mean postoperative IOPs were lower in eyes with dorzolamide application (15.6+/-7.2 mmHg) than in eyes without any medication (18.1+/-8.5 mmHg) both in eyes with 1.4% NaHa and 1% NaHa usage (p=0.003). Dorzolamide application caused an average 2.5 mm decrease in mean postoperative IOPs in both groups. Effects of OVDs on IOP rises after phacoemulsification surgery are closely related to their molecular structure. Increase in viscosity rendered higher postoperative IOP increments. However, topical dorzolamide application effectively reduced postoperative IOP increments in eyes with both Healon and BD Visc use.

In vitro behavior of ophthalmic viscosurgical devices during phacoemulsification

To evaluate the behavior and aspiration of several ophthalmic viscosurgical devices (OVDs) during phacoemulsification. Department of Ophthalmology, Tokyo Dental College Suidobashi Hospital, Tokyo, Japan. 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. 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. 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.

Removal times for a dispersive and a cohesive ophthalmic viscosurgical device correlated with intraocular lens material

Purpose: To investigate the removal times of ophthalmic viscosurgical devices (OVDs) with different intraocular lens (IOL) designs and materials. Setting: Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA, and Heidelberg IOL & Refractive Surgery Research Group, Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany. Methods: In a standardized laboratory setup, the Miyake-Apple posterior view video technique was used to evaluate OVD removal from capsular bags in human autopsy eyes implanted with poly(methyl methacrylate) (PMMA), silicone, and acrylic IOLs. The cohesive OVD ProVisc® (sodium hyaluronate 1.0%) and the dispersive OVD Viscoat® (sodium hyaluronate 3.0% and chondroitin sulfate 4.0%) were stained with fluorescein for better visualization. The open-sky preparation and an Alcon Series 20000® Legacy® phaco machine with a flow rate of 25 mL/min and a vacuum setting of +500 mm Hg (maximum irrigation/aspiration) were used. The time needed for complete removal of the cohesive and dispersive OVDs with each IOL type was measured and analyzed statistically. Results: The mean removal times for both OVDs were as follows: Alcon MZ60BD PMMA IOL—25.0 seconds ± 3.7 (SD) (Viscoat), 15.9 ± 6.9 seconds (ProVisc); Alcon AcrySof® MA60BM IOL—35.5 ± 10.0 seconds (Viscoat), 25.6 ± 4.7 seconds (ProVisc); Chiron/Bausch & Lomb C1043 silicone IOL—46.5 ± 10.5 seconds (Viscoat), 17.3 ± 2.1 seconds (ProVisc); AMO SI-30 silicone IOL—33.5 ± 3.1 seconds (Viscoat), 15.3 ± 6.3 seconds (ProVisc); and Pharmacia 912 silicone IOL—18.3 ± 5.8 seconds (Viscoat), 19.8 ± 4.3 seconds (ProVisc). Conclusions: Differences in OVD removal times were detected. The removal time for the cohesive OVD correlated with the IOL material. Overall, the time needed for complete removal was significantly longer for the dispersive OVD than for the cohesive OVD.

Understanding, retaining, and removing dispersive and pseudodispersive ophthalmic viscosurgical devices

Purpose: To analyze and explain the rheologic behavior of pseudodispersive viscoadaptive ophthalmic viscosurgical devices (OVDs) and compare it with that of dispersive OVDs. Setting: York Finch Eye Associates and Humber River Regional Hospital, Toronto, Ontario, Canada. Methods: Poiseuille's law was used as a basis of understanding fluid aspiration. Each OVD class was analyzed to determine how well it fit the law and why. Results: Higher viscosity cohesive OVDs are removed in a manner predicted by Poiseuille's law. Lower viscosity dispersive and viscoadaptive OVDs are not. Conclusions: Lower viscosity dispersive OVDs possess inadequate cohesion to maintain continuous contact with the aspiration port during irrigation/aspiration, whereas viscoadaptive OVDs are too rigid to permit scrolling around obstacles in the eye (the intraocular lens), also resulting in interrupted contact with the aspiration port. Dispersion and pseudodispersion represent opposite ends of a spectrum of increasing cohesion and rigidity correlating with increasing zero-shear viscosity and are not similar.