New classification of ophthalmic viscosurgical devices—2005

The applications of viscoelastic agents in vitreoretinal surgery

The introduction of viscoelastics in human ocular surgery dates back to 1972.Subsequntly, several substances were proposed as adjuvants, particularly for cataract surgery; however, the rheologic properties of ophthalmic viscosurgical devices (OVDs), such as viscosity, pseudoplasticity, and coatability led to their employment also in vitreoretinal surgery. OVDs can be used to separate tissues and create space, to break adhesions, to allow space for surgical manipulation, and to contain hemorrhage by dampening capillary oozing. We focus on the principles and clinical results of several viscosurgery techniques, such as viscodissection and viscodelamination for the management of proliferative vitreoretinopathy and diabetic retinopathy and suprachoroidal buckling for primary retinal detachment. Furthermore, we analyze the techniques in which OVDs served as adjuvants in macular hole surgery, particularly in the handling of the internal limiting membrane, and as volumetric substances against hypotony. Finally, we analyze recent perspectives on vitreous humor biochemical features. Preclinical research led to the belief that hyaluronic acid-based hydrogels could become ideal vitreous substitutes, thanks to their viscoelasticity, porosity, optical properties, and biocompatibility; however, although promising, long-term toxicity issues have limited studies on human subjects.

Injectable Fluorescent Bottlebrush Polymers for Interventional Procedures and Biomedical Imaging

Injectable biomaterials play a vital role in modern medicine, offering tailored functionalities for diverse therapeutic and diagnostic applications. In ophthalmology, for instance, viscoelastic materials are crucial for procedures such as cataract surgery but often leave residues, increasing postoperative risks. This study introduces injectable fluorescent viscoelastics (FluoVs) synthesized via one-step controlled radical copolymerization of oligo(ethylene glycol) acrylate and fluorescein acrylate. These bottlebrush-shaped polymers exhibit enhanced fluorescence intensity for improved traceability and facile removal postsurgery. To prevent aggregation, charged terpolymers were synthesized, ensuring intra- and intermolecular electrostatic repulsion. Dynamic light scattering and energy-conserved dissipative particle dynamics simulations revealed how the fluorescein content and monomer sequence affect the hydrodynamic size of these copolymers. Biocompatibility assessments showed that FluoVs maintained cell viability comparable to commercial hydroxypropyl methylcellulose and nonfluorescent poly(oligo(ethylene glycol) acrylate) controls. The FluoVs combine high fluorescence intensity, low viscosity, and excellent biocompatibility, offering intraoperative traceability and significant advancements for ocular and bioimaging applications.

Suggestion of serious incidents in medical devices used in anterior segment surgery. Proposing ideas (II)

The entry into force of the regulation on medical devices obliges ophthalmologists to identify and report possible serious incidents arising from their use. Faced with the doubts that may arise about what can or cannot be considered a serious incident, a working group of members of the Spanish Society of Refractive and Implant Eye Surgery (SECOIR) and the ophthalmology and vision sciences cluster (Cluster4Eye), have prepared a consensus document that aims to guide ophthalmologists on some of the incidents that, in the experience of the work team, are not common or can cause serious damage to the patient's function in relation to the use of medical devices. Incidents related to the use of viscoelastics, anterior capsule dyes, intraocular lenses, and other items used in anterior segment surgery have been addressed.

Impact of temperature on ophthalmic viscosurgical devices and clinical implications: a pilot study

PURPOSE

To evaluate how temperature affects the rheology of common ophthalmic viscosurgical devices (OVDs) and clinical implications.

SETTING

Tennent Institute of Ophthalmology, Glasgow, with Department of Mechanical and Aerospace Engineering, and Advanced Materials Research Laboratory, University of Strathclyde, Glasgow, United Kingdom.

DESIGN

Laboratory pilot study.

METHODS

The viscous and elastic responses of 3 OVDs (Eyefill-SC/Eyefill-C/Eyefill-HD) were measured using rotational and extensional rheometers at clinically relevant temperatures (5°C, 25°C, 37°C). Thermal properties were evaluated using differential scanning calorimetry and laser-flash analysis.

RESULTS

The OVDs tested exhibited viscoelastic properties and shear-thinning behavior. Apparent viscosities and relaxation time were higher at lower temperatures. The Eyefill-C and Eyefill-SC exhibited predominantly viscous character at low frequencies with a transition to predominantly elastic behavior at high frequencies. An increase in temperature led to a decrease in relaxation time under shear and extension. At low frequencies, Eyefill-C and Eyefill-SC moduli increase with decreasing temperatures. Eyefill-HD at 25°C and 37°C displays 2 crossover points, with the storage modulus dominating at low and high frequencies indicating a predominantly elastic behavior. Thermal property analysis revealed Eyefill-C had the lowest thermal conductivity.

CONCLUSIONS

This pilot study confirms our clinical experience that OVD properties are affected by low temperatures, with increased viscosities at low shear rates and higher relaxation times. Cold OVD can cause greater resistance to initiation of intraocular lens (IOL) injection system forces (compared with warmer OVD). Excessively forced injection using cold OVD could contribute to inadvertent cannula detachment if incorrectly assembled, or uncontrolled IOL release leading to avoidable injury.

Impact of Phacoemulsification on Trabeculectomy Bleb Function and Morphology in Primary Angle Closure Glaucoma: A Comparative Study of the Visco-Cushion Effect

Purpose This study evaluates the impact of phacoemulsification on trabeculectomy bleb morphology and intraocular pressure (IOP) control in patients with primary angle closure glaucoma (PACG). The study also evaluates possible alterations in these effects by intra-operative blocking of internal sclerostomy by high-density viscoelastic (visco-cushion). Methods This is a single-center, interventional, prospective study including patients with PACG who underwent phacoemulsification post-trabeculectomy. This study also evaluated the effect of sodium hyaluronate 1.4% as a cushion to block the sclerostomy site. Patients were divided into two groups: group A received this intervention, while group B did not. Postoperative IOP and the number of glaucoma medications at week 2, month 1, and month 4 were assessed as a measure of bleb function. Bleb morphology was analyzed at these timepoints using the Indiana Bleb Appearance Grading Scale (IBAGS) and anterior segment optical coherence tomography (AS-OCT). Results The study included 35 patients with a mean age of 59.91 ± 7.59 years. The mean interval between trabeculectomy and phacoemulsification was 6.83 ± 5.57 years (range: 1-20 years). Mean preoperative IOP was 15.43 ± 2.62 mm Hg, with 12 eyes needing anti-glaucoma medications (AGMs). Mean IOP at postoperative month 4 was 12.69 ± 2.32 mm Hg (p<0.001, chi-square test), with one eye needing AGM. IOP reduction was significantly lower in the visco-cushion group (p<0.05, ANOVA test). By the end of four months, 97.14% of patients showed complete success as compared with 65% preoperatively. Bleb morphology was noted to be maintained in up to 66% patients in terms of bleb height and extent on IBAGS, as well as bleb internal reflectivity and the number of microcysts, as noted on AS-OCT. The group without a visco-cushion exhibited a significant decrease in qualitative bleb height and microcystic spaces, along with an increase in bleb vascularity (p<0.05, Fischer exact test). Thirty patients (87.5%) showed a >20% decline in bleb height on AS-OCT, which was greater in group without visco-cushion (p<0.05, Mann-Whitney U test). Conclusion Use of a visco-cushion during phacoemulsification in PACG eyes with prior functioning trabeculectomy resulted in the retention of healthy bleb morphology parameters except bleb wall thickening. However, this protective effect on bleb morphology did not transcribe into IOP reduction. On the contrary, conventional phacoemulsification despite bleb height reduction, increased bleb vascularity, and decreased microcystic spaces resulted in better IOP control in the first four months after surgery. Longer follow-up of these cases is suggested to examine eventual fate of these bleb morphological alternations.

A Prospective, Randomized, Controlled Clinical Investigation Comparing the Efficacy and Safety of Sodium Hyaluronate-Based Ophthalmical Viscosurgical Devices FIDIAL PLUS and IAL®-F in Cataract Surgery

Purpose: To protect the corneal endothelium, various ophthalmical viscoelastic devices (OVDs) are used during cataract surgery. In this study, we compared two sodium hyaluronate-based OVD, the bacteria-derived FIDIAL PLUS OVD (test) with the animal-derived IAL®-F OVD (reference) during the surgical procedure. Methods: Fifty patients with bilateral cataract participated in the study: 50 eyes randomly received FIDIAL PLUS and 50 eyes received IAL®-F (ratio 1:1). Noninferior efficacy of FIDIAL PLUS compared with reference OVD (first objective) was evaluated using a paired t-test comparing the mean percent loss of corneal endothelial cells (CECs) with FIDIAL PLUS against the mean percent loss with IAL®-F. Corneal endothelial protection during cataract surgery with FIDIAL PLUS without significant (≥30 mmHg) postoperative intraocular pressure (IOP) increase (main secondary objective) was assessed using a repeated measures logistic model comparing the incidence of significant postoperative IOP elevation between the two groups. Safety, tolerability, and efficacy were also evaluated by assessing secondary endpoints before and after surgery. Results: FIDIAL PLUS showed a statistically noninferior efficacy compared with IAL®-F; there was no significant increase in IOP in either group or different trends of the secondary endpoints were observed between the OVD groups. The safety profile was similar in both OVD groups and no adverse device effects were reported. Conclusions: This study demonstrates the equivalent efficacy, tolerability, and safety of the bacteria-derived FIDIAL PLUS compared with the animal-derived IAL®-F, confirming the clinical value of this product.

Retention time of different ophthalmic viscosurgical devices during phacoemulsification in rabbit ocular model: A comparative analysis

BACKGROUND

To compare retention times of various ophthalmic viscosurgical devices (OVDs) and soft-shell combinations.

METHODS

Experimental study. Eighteen rabbit eyes were divided into six groups of three eyes, based on OVDs tested. A: Endocoat, B: HealonPro, C: Viscoat, D: Provisc, E: Endocoat and HealonPro and F: Viscoat and Provisc. OVDs were stained with 10% fluorescein dye before being injected into the anterior chamber. Phacoemulsification, using fixed parameters, was performed. If OVD persisted after 60 s, a standardised irrigation and aspiration technique replaced phacoemulsification. The time until central and complete clearance of the OVD were video-recorded and measured.

RESULTS

Mean central retention times (CRT) were found to be: HealonPro-5.33 ± 2.56 s, Provisc-3.33 ± 1.11 s, Endocoat-75.0 ± 3.26 s, Viscoat-62.33 ± 5.19 s, combining HealonPro with Endocoat-22.67 ± 4.75 s and Provisc with Viscoat-11.0 ± 0.82 s. The mean total retention time (TRT) was: Endocoat-80.0 ± 8.17 s, Viscoat-81.67 ± 2.09 s, HealonPro with Endocoat-81.33 ± 3.35 s, and Provisc with Viscoat-71.0 ± 2.94 s. For HealonPro and Provisc, CRT and TRT remained identical across all trials.

CONCLUSIONS

Retention times varied, with cohesive OVDs exhibiting shorter durations than dispersive OVDs. Among dispersive OVDs, TRTs were comparable; however, Endocoat displayed an extended CRT. In soft shell trials, the combination of HealonPro and Endocoat exhibited prolonged CRT and TRT, suggesting enhanced corneal protection.

Comparison of the Residual Amount of an Ophthalmic Viscosurgical Device Among Different Types of Intraocular Lens Implants in vitro

Purpose

Although ophthalmic viscosurgical devices are quite important for safe cataract surgery, currently, postoperative residual ophthalmic viscosurgical devices can cause various complications. Previously, we developed a method to visualize residual ophthalmic viscosurgical devices after irrigation/aspiration in vitro and found that the amount of residual ophthalmic viscosurgical device on a single-piece intraocular lens was greater than that on a three-piece intraocular lens. In the present study, we compared the amounts of residual ophthalmic viscosurgical device among various foldable intraocular lenses to investigate the factors that determine the quantity of residual ophthalmic viscosurgical device.

Patients and Methods

Simulated cataract surgery was performed in pig eyes using an ophthalmic viscosurgical device labeled with fluorescent silica particles. After the simulated surgery procedure, the fluorescent silica attached to the intraocular lens was observed and quantified by inductively coupled plasma-atomic emission spectrometry after intraocular lens removal. The amount of residual ophthalmic viscosurgical device was compared among five representative single-piece intraocular lenses and one three-piece intraocular lens.

Results

The distribution and amount of the residual ophthalmic viscosurgical device differed for each intraocular lens. The amount of silicon in the lens capsule differed among the intraocular lens types.

Conclusion

The postoperative residual tendency of ophthalmic viscosurgical devices differed among various single-piece intraocular lenses. The behavior of the intraocular lenses within the capsule affected the residual tendency. The removal of ophthalmic viscosurgical device in the lens capsule should be tailored for each intraocular lens to improve efficiency.

Corneal endothelial cell loss and intraocular pressure following phacoemulsification using a new viscous-cohesive ophthalmic viscosurgical device

PURPOSE

To compare results of two ophthalmic viscosurgical devices (OVDs)-Viscoat (a dispersive OVD, Alcon) and FR-Pro (a viscous-cohesive OVD, Rayner), in phacoemulsification surgery.

METHODS

A prospective randomized controlled study. Patients undergoing phacoemulsification were randomly assigned to receive one of the two OVDs. Exclusion criteria were age under 40, preoperative endothelial cell count (ECC) below 1,500 cells/mm2 and an eventful surgery. The primary outcome was change in ECC from baseline to postoperative month one and month three. Secondary outcomes were the difference between ECC at postoperative month one and month three, changes in IOP and occurrence of an IOP spike ≥ 30 mmHg after surgery.

RESULTS

The study included 84 eyes-43 in the Viscoat group and 41 in the FR-Pro group. Mean cell density loss at month one and month three was 17.0 and 19.2%, respectively, for the Viscoat group and 18.4 and 18.8%, respectively, for the FR-Pro group, with no statistically significant difference between the groups (p = 0.772 and p = 0.671, respectively). The mean ECC difference between the month one and month three visits was 50.5 cells/mm2 and was not statistically significant (p = 0.285). One eye in each group had an IOP spike ≥ 30 mmHg, both normalized by postoperative week one.

CONCLUSIONS

Viscoat and FR-Pro have comparable results following phacoemulsification surgery, suggesting that while FR-Pro is not a dispersive OVD, its endothelial cell protection may be comparable to one, perhaps due to the addition of sorbitol. Furthermore, a one-month follow-up of ECC seems sufficient in such trials.

Physical Characteristics, Clinical Application, and Side Effects of Viscoelastics in Ophthalmology

Purpose

To explain the physical properties of ophthalmic viscoelastic devices (OVDs), covering their structural units, optimal features, existing viscoelastic materials, clinical applications, and potential side effects.

Methods

This is a narrative review on the OVDs. A literature review was conducted in PubMed, Google Scholar, and Scopus databases. Studies that investigated physical characteristics, clinical applications, OVD commercial products, and their complications were included.

Results

We included 42 articles from 2010 and discussed physical characteristics, properties of a desirable OVD, structural units of common OVDs, OVD commercial products, clinical applications, and also complications of OVDs.

Conclusions

Today, viscoelastics hold a distinct and crucial role in intraocular surgery due to their remarkable properties. These materials safeguard the endothelium and epithelium, uphold anterior chamber depth, manage intraocular bleeding, ease tissue handling, and aid intraocular lens placement. Currently, the American market features 12 prevalent viscoelastic types, including 7 sodium hyaluronate derivatives (Healon, Healon-Greater Viscosity, Healon-5, Amvisc, Amvisc Plus, Advanced Medical Optics Vitrax, and Provisc), 2 hydroxypropyl methylcellulose 2% derivatives (OcuCoat and Cellugel), and 3 combinations of sodium hyaluronate and chondroitin sulfate (Viscoat, DisCoVisc, and DuoVisc). Despite the introduction of new viscoelastic materials annually, no single material encompasses all desired properties. Surgeons must select and employ suitable viscoelastics based on surgical conditions and patient requirements. Advancements in material development and understanding of physical properties and clinical applications continue to refine viscoelastic selection.

Polysaccharides in contact lenses: From additives to bulk materials

As the number of applications has increased, so has the demand for contact lenses comfort. Adding polysaccharides to lenses is a popular way to enhance comfort for wearers. However, this may also compromise some lens properties. It is still unclear how to balance the variation of individual lens parameters in the design of contact lenses containing polysaccharides. This review provides a comprehensive overview of how polysaccharide addition impacts lens wear parameters, such as water content, oxygen permeability, surface wettability, protein deposition, and light transmittance. It also examines how various factors, such as polysaccharide type, molecular weight, amount, and mode of incorporation into lenses modulate these effects. Polysaccharide addition can improve some wear parameters while reducing others depending on the specific conditions. The optimal method, type, and amount of added polysaccharides depend on the trade-off between various lens parameters and wear requirements. Simultaneously, polysaccharide-based contact lenses may be a promising option for biodegradable contact lenses as concerns regarding environmental risks associated with contact lens degradation continue to increase. It is hoped that this review will shed light on the rational use of polysaccharides in contact lenses to make personalized lenses more accessible.

Corneal Outcomes Following Cataract Surgery Using Ophthalmic Viscosurgical Devices Composed of Chondroitin Sulfate-Hyaluronic Acid: A Systematic Review and Meta-Analysis

Background

Ophthalmic viscosurgical devices (OVDs) are commonly used during cataract surgery to protect the corneal endothelium. A systematic literature review and meta-analysis were conducted to assess the clinical evidence of OVDs composed of chondroitin sulfate-hyaluronic acid (CS-HA) versus other OVDs in maintaining endothelial cell density (ECD) and corneal thickness (CT).

Methods

MEDLINE and EMBASE databases were searched from 2000 to 2020. Randomized controlled trials (RCTs, N ≥ 20 per group) comparing an OVD containing CS-HA (ie, VISCOAT^®, DuoVisc^® or DisCoVisc^®) to any other OVD were included. The identified comparators were limited to the OVDs found in the literature, which included those composed of HA-only or hydroxypropyl methylcellulose (HPMC). Outcomes of focus included changes in ECD (baseline to 3 months) and CT (baseline to 24 hours). Meta-analyses were performed using R software, to assess mean differences (MD) in ECD and CT change between CS-HA OVDs and HA-only or HPMC OVDs.

Results

A total of 966 abstracts were screened, and data were extracted from 12 RCTs. Meta-analyses using a random-effects model revealed significantly lower percent (%) decrease in ECD for CS-HA OVDs compared to both HA-only (MD: -4.10%; 95% CI: -5.81 to -2.40; p < 0.0001; 9 studies) and HPMC (MD: -6.47%; 95% CI: -10.41 to -2.52; p = 0.001; 2 studies) products. Similarly, % CT increase was significantly lower with CS-HA than with HA-only OVDs (MD: -3.22%; 95% CI: -6.24% to -0.20%; p = 0.04; 4 studies). However, there were no significant differences when comparing % CT change between CS-HA and HPMC OVDs (MD: 2.65%; 95% CI: -0.43% to 0.95%; p = 0.4; 2 studies).

Conclusion

CS-HA OVDs lead to less postoperative loss of endothelial cells and may better protect corneal endothelium during cataract surgery, relative to other OVDs. Future randomized studies may be needed to solidify these findings.

Evaluation of the Rheological Properties, Preclinical Safety, and Clinical Effectiveness of a New Dispersive Ophthalmic Viscoelastic Device for Cataract Surgery

Purpose

To evaluate the rheological properties of the ophthalmic viscoelastic device (OVD) PRO-149, its preclinical safety, and its effectiveness when used during cataract surgery in patients with age-related cataract.

Material and Methods

Control (HEC) and test (PRO-149) OVDs were compared through rheological measures, by two preclinical safety studies in rabbits, and under normal-use conditions during cataract removal and lens implantation in a parallel randomized clinical trial.

Results

Rheological properties were determined. Preclinical studies did not find any evidence of safety issues or toxicity. In the clinical trial, 36 subjects were included. After 29 days, there were no statistically significant differences in mean percentage of endothelial cell count change or in the postoperative intraocular pressure between groups. There were no significant differences between OVDs for any safety parameter studied. Finally, PRO-149 showed a statistically significant improvement in surgeon rating for ease of use during extraction (p < 0.05).

Conclusion

PRO-149 is a dispersive OVD. The rabbit models did not find evidence of clinical alterations or toxicity. The results of the clinical study support that the two studied OVDs were clinically similar in terms of safety and effectiveness for cataract surgery.

Trial Registration

The trial is registered at Clinical Trials.gov at NCT04702802 (21–01-11).

The safety and effectiveness of a new ophthalmic viscosurgical device-a randomized, controlled study

ClearVisc was significantly noninferior to Viscoat in the mean percentage of ECD loss from baseline to 3 months and proportion of patients with postoperative IOP ≥30 mm Hg at any follow-up.

To evaluate the safety and effectiveness of a new dispersive ophthalmic viscosurgical device (OVD) (ClearVisc) compared with an approved dispersive OVD (Viscoat) when used in cataract surgery.

Moxifloxacin releasing intraocular implant based on a cross-linked hyaluronic acid membrane

Intraocular antibiotic delivery is an important technique to prevent bacterial infection after ophthalmic surgery, such as cataract surgery. Conventional drug delivery methods, such as antibiotic eye drops, have limitations for intraocular drug delivery due to the intrinsic barrier effect of the cornea. Therefore, frequent instillation of antibiotic eyedrops is necessary to reach a sufficient bactericidal concentration inside the eye. In this study, an intraocular implant, MXF-HA, that combines hyaluronic acid (HA) and moxifloxacin (MXF) was developed to increase the efficiency of intraocular drug delivery after surgery. MXF-HA is manufactured as a thin, transparent, yellow-tinted membrane. When inserted into the eye in a dry state, MXF-HA is naturally hydrated and settles in the eye, and the MXF contained therein is delivered by hydrolysis of the polymer over time. It was confirmed through in vivo experiments that MXF delivery was maintained in the anterior chamber of the eye at a concentration sufficient to inhibit Pseudomonas aeruginosa and Staphylococcus aureus for more than 5 days after implantation. These results suggest that MXF-HA can be utilized as a potential drug delivery method for the prevention and treatment of bacterial infections after ophthalmic surgery.

Ophthalmic Viscosurgical Devices (OVDs) in Challenging Cases: a Review

Ophthalmic viscoelastic devices (OVDs) are currently used in cataract surgery and have significantly improved the safety and effectiveness of this surgical procedure. OVDs are classified according to the zero-shear viscosity and the cohesion-dispersion index in cohesive, dispersive, and viscoadaptives. OVDs create and maintain anterior chamber depth and visibility, protecting the corneal endothelium and other intraocular tissues during surgery. The selection of the most adequate OVD is especially relevant when performing cataract surgery in challenging cases, such as in hard, mature cataracts, flat anterior chamber, pseudoexfoliation syndrome, intraoperative floppy iris syndrome, or glaucoma surgery. In such cases, OVD is crucial for facilitating the surgical procedure and the associated minimal complication rate. The use of a combination of OVDs (soft-shell technique and modifications), the use of blue-colored OVDs, and the combination of sodium hyaluronate with lidocaine have also been described as useful tools in some of these challenging cases.

Advances in Understanding the Mechanism of Ophthalmic Viscosurgical Device Retention in the Anterior Chamber or on the Corneal Surface during Ocular Surgery

Retention durability, especially in the eye, is one of the most important properties of ophthalmic viscosurgical devices (OVDs) during ocular surgery. However, the information on the physical properties of OVDs is insufficient to explain their retention durability. The purpose of this study is to clarify the mechanism of OVD retention to improve understanding of the behavior of OVDs during ocular surgery. To elucidate the mechanism of OVD retention, we have developed a new test method for measuring repulsive force. As a result, the maximum repulsive force of OVDs was positively and well correlated with the retention durability of investigated OVDs. Consequently, we demonstrated that the repulsive force could be used as an index of retention durability on the ocular surface and in the eye. We directly compared the intraocular retention durability of three OVDs (Shellgan, Viscoat, and Opegan-Hi) in ex vivo porcine eyes. Opegan-Hi was immediately removed from the anterior chamber, but Shellgan and Viscoat remained largely in the anterior chamber as determined by fluorescence imaging. These results showed that the intraocular retention behavior of OVDs was similar to their ocular surface behavior in our previous report, suggesting that retention durability is dependent on the OVD itself. The retention durability of Shellgan seemed to be higher than that of Viscoat, and the maximum repulsive force of Shellgan was 1.35-fold higher than that of Viscoat. Therefore, the repulsive force might be a useful index for assessing the difference in the retention durability between OVDs such as Shellgan and Viscoat.

A primer on ocular viscosurgical devices

PURPOSE

To provide pharmacists with an overview of ocular viscosurgical devices (OVDs) and a comprehensive resource describing characteristics of commercially available agents.

SUMMARY

OVDs are substances that are injected into the eye during ophthalmic procedures, such as cataract surgery, to reduce injury to the endothelium that may result from surgical manipulation. Currently available OVDs are composed of one or more of the following active ingredients: sodium hyaluronate, sodium chondroitin sulfate, and hydroxypropylmethylcellulose. Rheologic properties of OVDs, such as viscosity, elasticity, pseudoplasticity, and cohesion, affect the products' function and performance. Based on rheologic properties, OVDs can be generally classified as cohesive or dispersive. Given each products' unique characteristics, OVDs are not interchangeable. An understanding of OVD characteristics and role in practice allows for improved product selection, which varies based on patient characteristics and procedure. Availability of OVD information and literature is generally lacking since OVDs are regulated by the US Food and Drug Administration (FDA) as medical devices. This primer includes an overview of relevant ophthalmic surgical practices and the landscape of comparative efficacy and safety literature to assist in formulary decision-making. This review also provides a comprehensive guide to commercially available OVDs and a discussion on practical considerations for the pharmacist.

CONCLUSION

Pharmacists may be tasked with handling OVDs in institutional settings. Knowledge about OVD rheologic properties, product characteristics, role in practice, and available literature is necessary for managing formularies and ensuring optimal product selection.

Achieving successful capsulorhexis in intumescent white mature cataracts to prevent Argentinian flag sign - A new multifaceted approach to meet the challenge

Purpose:

To present a case series of intumescent white cataract cases managed by a new surgical technique to attain a single stage Continuous Curvilinear Capsulorhexis (CCC).

Methods:

The series included 60 eyes of 60 patients with white cataract which underwent preoperative anterior chamber depth, lens thickness and ultrasonographic A-scan for intralenticular spikes. A partial size main port (~1.8mm) is created as the first entry into the anterior chamber (AC). A 30-gauge needle of insulin syringe entered through a limbal stab incision is used to decompress the anterior and posterior intralenticular compartments. Following which a standard size, one stage capsulorhexis was performed in a trypan blue stained capsule using microcapsulorhexis forceps entered through the partial sized trapezoidal main port. The main port was secondarily enlarged for phacoemulsification.

Results:

Based on the intraoperative findings, 43 eyes were categorized as Intumescent type-1 cataracts i.e., with presence of actual liquefied cortex aspirated using 30-gauge needle and 17 eyes as Intumescent type-2 cataracts, i.e., presence of swollen lens without any obvious liquefied cortex. Standard size, circular and centred CCC was achieved in 100% of the cases and no Argentinean flag sign was noted. Surgeon perceived raised intralenticular pressure in 41% of the cases in type-1 subset and 61% cases in type-2 subset (P-0.06). Posterior capsular plaque was observed in 22% of the cases, adherent cortex in 25% and anterior capsular plaque in 5% of the cases. At 6weeks follow up 92% patients had best corrected visual acuity of 20/40 or better.

Conclusion:

A multi-layered approach can help in attaining successful CCC in cases of white mature cataract with high intralenticular pressure.

Role of rheology in tears and artificial tears

The study of viscoelastic fluids as artificial tears dates back to the late 1970s. Healon, the first ophthalmic viscosurgical device, was approved in 1980, but studied extensively before then, exhibits very interesting shear-thinning properties that were found to be beneficial in both ophthalmic surgery and somewhat later as a tear replacement solution. Unlike the previous tear film replacements, which were mainly viscous in nature, viscoelastic solutions, particularly those based on hyaluronan, exhibited very interesting, potentially beneficial, rheological properties, especially when slightly altered to become elastoviscous. This review examines the rheological properties that are significant in artificial tear solutions. We define herein the necessary parameters that need to be further studied to design and formulate rheologically better artificial tears, which should provide enhanced efficacy compared with their predecessors.

Evaluation of femtosecond laser-assisted anterior capsulotomy in the presence of ophthalmic viscoelastic devices (OVDs)

The introduction of femtosecond laser-assisted cataract surgery is an alternative approach to conventional cataract surgery. Our study aimed to determine the effectiveness of femtosecond laser-assisted capsulotomy in the presence of different ophthalmic viscoelastic devices (OVDs) in the anterior chamber. Fresh porcine eyes (n = 96) underwent LDV Z8-assisted anterior capsulotomy, either in the presence of an OVD (Viscoat, Provisc, Healon, Healon GV or HPMC) or without, using 90% and 150% energies respectively. Following that, the capsule circularity, tag’s arc-length, tag-length, tag-area and rupture strength (mN) of the residual capsular bag were evaluated. We found that increasing energy from 90 to 150% across the OVD sub-groups improved the studied capsulotomy parameters. Amongst the 90% energy sub-groups, the circularity and tag-parameters were worse with Viscoat and Healon GV, which have higher refractive index and viscosity compared to the aqueous humour. Using 150% energy, Healon GV showed a significantly worse total arc-length (p = 0.01), total tag-length (p = 0.03) and total tag-area (p = 0.05) compared to the control group. We concluded that; an OVD with a refractive index similar to aqueous humour and lower viscosity, such as Healon or Provisc, as well as a higher energy setting, are recommended, to enhance the efficacy of laser capsulotomy.

Effects of Combinations of Ophthalmic Viscosurgical Devices and Suction Flow Rates on the Corneal Endothelial Cell Damage Incurred during Phacoemulsification

We examined the effects of different ophthalmic viscosurgical devices (OVDs) and suction flow rates during phacoemulsification on the amount of ultrasound power used and damage to the corneal endothelium. In total, 48 eyes of 24 patients who underwent phacoemulsification and intraocular lens insertion with different OVD settings in the left and right eye between February and August 2018 were examined retrospectively from medical records. Each of the following types of OVDs was used in either the right or left eye of each patient: a viscoadaptive OVD (V group) or a combination of dispersive and cohesive OVDs (soft-shell technique; S group). There was no significant difference in the lens nucleus hardness between the two groups. A 2.4 mm transconjunctival scleral incision was made, and phacoemulsification was performed by the same surgeon. The cumulative dissipated energy (CDE) and ultrasound time intraoperatively were compared between the two groups. The CDE was significantly larger in the V group (9.9 ± 4.6) than the S group (6.4 ± 3.0; p=0.006). The reduction rate of the endothelial cell density at the center of the cornea was significantly higher in the V group (4.1% ± 6.7%) than the S group (0.3% ± 4.5%; p=0.03) at 1 week postoperatively. Both groups had a good postoperative course. There was less corneal endothelial damage with the soft-shell technique combined with a normal flow setting than the viscoadaptive OVD combined with a low flow setting.

Quantitative Assessment of Ophthalmic Viscosurgical Devices on Visibility, Spreadability, and Durability as Corneal Wetting Agents for the Wet Shell Technique

Purpose

To evaluate ophthalmic viscosurgical devices (OVDs) as corneal wetting agents for the wet shell technique, a common procedure in Japan to maintain the wettability of corneal surfaces.

Methods

We surveyed Japanese ophthalmologists to determine the current state of the wet shell technique. After developing three ex vivo testing methods, we evaluated the corneal wetting properties of OVDs including 3% hyaluronic acid (HA) solution and OVD products, Opegan, Opelead, Viscoat, Shellgan, Discovisc, and Opegan-Hi.

Results

Overall, 214 ophthalmologists (70%) had performed the wet shell technique, and 91% of ophthalmologists who performed vitreous surgery had performed this technique. Using a questionnaire, we evaluated the performance of OVD as corneal wetting agents as follows: (i) visibility, smoothness of OVD surface; (ii) spreadability, coverage of the cornea; and (iii) retention durability, residual ratio of OVD on the corneal surface. The smoothness and spreadability of Opegan, Opelead, and 3% HA were superior to other OVDs. Adding an appropriate amount of balanced salt solution to the other OVDs improved smoothness and spreadability similar to that of Opelead or 3% HA. Shellgan and Viscoat, combination OVDs consisting of 3% HA and 4% chondroitin sulfate, showed high retention durability, resulting in remaining longer on the cornea compared with other OVDs.

Conclusions

Physical properties of OVDs tested in this study may provide useful information for ophthalmologists to select a suitable OVD when performing the wet shell technique.

D-sorbitol can keep the viscosity of dispersive ophthalmic viscosurgical device at room temperature for long term

The combination of 3% sodium hyaluronate (HA) and 4% sodium chondroitin sulfate (CS) is used as a dispersive ophthalmic viscosurgical device (OVD) during cataract surgery. For most OVDs containing HA, storage at 2–8 °C is recommended to preserve product characteristics. In order to develop a dispersive OVD that can be stored at room temperature, in this study, we searched additives which can stably maintain the viscosity, a key parameter of OVD, under preservation stability testing at 60 °C. The addition of D-sorbitol to a combination OVD, 3% HA and 4% CS, suppressed the reduction in viscosity compared with other OVDs with or without additives. The addition of D-sorbitol was also effective in improving the residual viscosity of the combination OVD after thermal treatment and light irradiation. Moreover, the OVD containing D-sorbitol can be stored at 25 °C with stably maintaining the initial viscosity for at least 24 months. In conclusion, the new dispersive OVD, 3% HA, 4% CS, and 0.5% D-sorbitol, can be stored at room temperature instead of under cold conditions and may represent an attractive option for clinical use because it is not necessary to bring the product to room temperature prior to use.

Addition Of D-Sorbitol Improves The Usability Of Ophthalmic Viscosurgical Devices

Purpose

To evaluate the effects of D-sorbitol addition on changes in the extrusion force of ophthalmic viscosurgical devices (OVDs).

Methods

OVD formulations; the mixtures of 3% hyaluronic acid (HA) and 4% chondroitin sulfate (CS) containing 0%, 0.5%, or 1.0% D-sorbitol were prepared. Each prefilled syringe of OVD was stored at room temperature for 0, 15, 30, 60, or 120 mins after a small amount of viscoelastic agent was discharged from the needle. The extrusion force values (kgf) of these OVDs when reused after storage were measured with a texture analyzer. Moreover, 10 healthy adults (5 men and 5 women) used a pinch sensor to measure the extrusion force values for the HA/CS combination without D-sorbitol which was stored in the above manner, and used a 4-step scale to score the usability of OVD.

Results

For the HA/CS combination without D-sorbitol, the extrusion force value was increased from its initial value (storage duration, 0 min) as storage duration increased. However, for the HA/CS combination containing 0.5% or 1.0% D-sorbitol, this value remained almost unchanged over time. Likewise, the pinch sensor-determined extrusion force values of HA/CS combination without D-sorbitol increased, depending on storage duration.

Conclusion

The addition of D-sorbitol to viscoelastic agent may suppress the needle clogging that occurs with OVD storage, and may improve the usability of OVDs during surgery.

Quantification of residual ophthalmic viscosurgical device after irrigation/aspiration in experimental cataract surgery in vitro

PURPOSE

To determine the distribution and quantity of ophthalmic viscosurgical device (OVD) retained in the lens capsular bag after irrigation/aspiration (I/A) in experimental cataract surgery.

SETTING

Department of Ophthalmology, Kashiwa Hospital, Jikei University School of Medicine, Japan.

DESIGN

Experimental study.

METHODS

Fifteen freshly enucleated porcine eyes were used. Sodium hyaluronate 1.0% (Healon) was mixed with a fixed concentration of silica nanoparticles encapsulating fluorescein isothiocyanate (labeled OVD), and it was injected separately into the capsular bag and injector cartridge for intraocular lens (IOL) insertion. After a 3-piece IOL (YA-60BBR) or a 1-piece IOL (iSert 255) was implanted within the capsular bag, OVD was removed by thorough I/A. Eyes that were injected with the labeled OVD into the capsular bag without IOL insertion were used as controls. The distribution of residual OVD in the capsular bag was observed under ultraviolet irradiation using Miyake-Apple view. Then, the excised capsular bag was dissolved in hydrogen fluoride, and silica concentration was measured quantitatively by elemental analysis.

RESULTS

The quantity of residual OVD in the capsular bag was 243.1 μg ± 1.3 (SD) in the 3-piece IOL-implanted group, 383.8 ± 11.1 μg in the 1-piece IOL-implanted group, and 99.0 ± 1.3 μg in the control group. In the 1-piece IOL-implanted eyes, OVD in the form of clumps tended to remain near the center of the optic on the posterior side, and the quantity of residual OVD was significantly greater than in 3-piece IOL-implanted eyes (P < .05).

CONCLUSION

The quantity of residual OVD after I/A could be determined indirectly using labeled OVD, and the quantity was significantly greater in 1-piece IOL-implanted eyes than in 3-piece IOL-implanted eyes.

[Evaluation of Rheological Properties of Cohesive Ophthalmic Viscosurgical Devices Composed of Sodium Hyaluronate with High Molecular Weight-2019]

Ophthalmic viscosurgical devices (OVDs), mainly containing sodium hyaluronate (HA), are used in cataract surgeries to protect the cornea endothelium. In this study, the rheological properties of 9 launched products (containing 1% HA) were evaluated. The molecular weights (MWs) of HA estimated based on intrinsic viscosity varied widely, between 1100-2500 kDa, and showed a particular value for each product. Of the 9 products, 6 are classified as cohesive OVDs and their product specifications show the same value for intrinsic viscosity (25-45 dL/g), with high MW HA (>2000 kDa); however, the MW of each HA showed a particular value (2200-2500 kDa) within the range of the product specification. As with the MW of HA, apparent viscosity and dynamic rheological parameters showed particular values for each OVD. The product Opegan-Hi exhibited the highest value of apparent viscosity at low shear rate, and a solid-like behavior among the OVDs. In a questionnaire survey among 198 cataract surgeons, 42% of surgeons had experienced a difference in ability to maintain the depth of anterior chamber during surgery among the different cohesive OVDs used. This suggested that surgeons select OVD properties based on surgical procedure and patient cases. In conclusion, we demonstrated that each OVD has particular rheological properties within the range of the product specification defined by the intrinsic viscosity. The results might provide useful information for surgeons in their selection of OVDs based on their experience.

Rheological and Adhesive Properties to Identify Cohesive and Dispersive Ophthalmic Viscosurgical Devices

The purpose of this study is to evaluate the usefulness of the rheological properties and adhesive force of ophthalmic viscosurgical devices (OVDs) as parameters for understanding and identifying the surgical behavior of cohesive and dispersive OVDs. The apparent viscosity, and the storage and loss moduli (dynamic rheological parameters) of 50% chondroitin sulfate (CS), 3% sodium hyaluronate (HA), Shellgan (the combination of 3% HA and 4% CS), Opegan (1% HA with a low molecular mass) and Opegan-Hi (1% HA with a high molecular mass) were obtained with a rheometer. The adhesive force of each sample was measured by using a texture analyzer. Opegan-Hi showed a solid-like behavior, while 50% CS showed a fluid-like behavior from their apparent viscosity and dynamic rheological parameters. Shellgan, 3% HA, and Opegan exhibited similar rheological properties and intermediate characteristics between Opegan-Hi and 50% CS, although their respective values were slightly different. Among these OVD samples, the adhesive force was higher in the order of 50% CS > Shellgan, 3% HA > Opegan > Opegan-Hi. The adhesive force of dispersive OVDs tended to be higher than that of cohesive OVDs, which correlated well with the removal times of OVDs from the eye that have previously been reported. In conclusion, we demonstrated that cohesive OVDs and dispersive OVDs have particular rheological and adhesive properties that can be applied to identify both types. These parameters obtained in this study provide useful information for a greater understanding and prediction of the behavior of OVDs in the eye during surgery.

A new histological evaluation method to detect residual ophthalmic viscosurgical devices for cataract surgery

Purpose

To establish a new evaluation method to quantify residual ophthalmic viscosurgical device (OVD) volume and corneal endothelium adhesion properties for phacoemulsification surgery.

Methods

We compared the performance of four OVDs (Viscoat®, Healon5®, Healon® and DisCoVisc®) using porcine eyes. First, OVDs were mixed with fluorescent-conjugated dextrans to render them visible under the microscope. A corneal side port was opened, followed by a continuous curvilinear capsulorhexis, and a corneal tunnel incision was made. OVDs were injected, then the lens was removed using one-handed phacoemulsification. After this procedure, the anterior segment of the eye was isolated via an equatorial incision and the tissue was immediately frozen in shimmering liquid nitrogen. Sagittal slices (20 μm) were cut with a Cryostat from limbus to limbus. Every tenth slide was imaged using a fluorescent microscope with a CCD camera. We evaluated the percentage of the corneal endothelium covered by each OVD as the OVD adhesion to corneal endothelium ratio (OAE ratio) and the volume of residual OVD in the anterior chamber.

Results

Viscoat® showed significantly higher endothelium coverage compared with both Healon® and DisCoVisc®. A statistically larger volume of Healon5® remained in the anterior chamber compared with Healon® and DisCoVisc®.

Conclusion

The new evaluation methods used here provide precise quantitative analysis of OAE ratio and residual OVD volume. These results show that Viscoat® and Healon5® have a high potential for coating the corneal endothelium during phacoemulsification and aspiration surgery.

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

PURPOSE

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.

SETTING

Department of Ophthalmology, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul, South Korea.

DESIGN

Experimental study.

METHODS

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 in vitro study, the retention time was measured in 3 groups of 45 porcine eyes during continuous phacoemulsification. In the in vivo study, the endothelial cell count (ECC) was measured before and 3 days after intermittent phacoemulsification in 12 rabbit eyes randomized to a poloxamer hydrogel or a dispersive OVD group.

RESULTS

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 in vitro study, the mean retention times were 5.53 seconds ± 1.77 (SD), 125.00 ± 29.34 seconds, and 221.53 ± 42.48 seconds 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 in vivo study, the mean decrease in ECC was significantly lower in the 26% poloxamer hydrogel group than in the dispersive OVD group (P = .029).

CONCLUSION

Thermoreversible hydrogels might be suitable substitutes for hyaluronic acid-based OVDs for corneal endothelial protection during phacoemulsification.

Angle stability and outflow in dual blade ab interno trabeculectomy with active versus passive chamber management

Purpose

To compare intraoperative angle stability and postoperative outflow of two ab interno trabeculectomy devices that excise the trabecular meshwork with or without active aspiration and irrigation. We hypothesized that anterior segment optical coherence tomography (AS-OCT) allows for a quantitative comparison of intraoperative angle stability in a microincisional glaucoma surgery (MIGS) pig eye training model.

Methods

Twelve freshly enucleated porcine eyes were measured with AS-OCT at baseline, at the beginning of the procedure and at its conclusion to determine the anterior chamber depth (ACD) and the nasal angle α in degrees. The right and left eye of pairs were randomly assigned to an active dual blade goniectome (aDBG) and a passive dual blade goniectome (pDBG) group, respectively. The aDBG had irrigation and aspiration ports while the pDBG required surgery under viscoelastic. We performed the procedures using our MIGS training system with a standard, motorized ophthalmic operating microscope. We estimated outflow by obtaining canalograms with fluorescent spheres.

Results

In aDBG, the nasal angle remained wide open during the procedure at above 90° and did not change towards the end (100±10%, p = 0.9). In contrast, in pDBG, ACD decreased by 51±19% to 21% below baseline (p<0.01) while the angle progressively narrowed by 40±12% (p<0.001). Canalograms showed a similar extent of access to the outflow tract with the aDBG and the pDBG (p = 0.513). The average increase for the aDBG in the superonasal and inferonasal quadrants was between 27 to 31% and for the pDBG between 15 to 18%.

Conclusion

AS-OCT demonstrated that active irrigation and aspiration improved anterior chamber maintenance and ease of handling with the aDBG in this MIGS training model. The immediate postoperative outflow was equally good with both devices.

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

PURPOSE

To evaluate the rheological properties of mixtures of different commercially available ophthalmic viscosurgical devices (OVDs) containing sodium hyaluronate and chondroitin sulfate.

SETTING

Eye Clinic, University of Trieste, Trieste, Italy.

DESIGN

Laboratory study.

METHODS

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.

RESULTS

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.

CONCLUSIONS

The mixture of dispersive and cohesive rheological properties in a single OVD might be an advantage during cataract surgery.

In Vivo Near-Infrared Fluorescence Imaging of Aqueous Humor Outflow Structures

The aim of this study has been to visualize the aqueous outflow system in patients affected by primary open angle glaucoma. A solution of indocyanine green (ICG) plus high viscosity viscoelastic solution was injected into the Schlemm canal during surgery in 10 glaucomatous patients undergoing canaloplasty. Soon after injection of the dye the borders of the scleral flap were completely stained due to partial reflux caused by the intrachannel resistance; progression of the dye along the Schlemm canal starting from the site of injection was then visualized. The filling of the collector channels was observed only in the patent portions of the Schlemm canal. The only noticeable aqueous veins were located in correspondence of the quadrant in which both the Schlemm canal and the collectors were patent. Lastly, a retrograde filling, of glomerular-shaped structures, deepest to the Schlemm canal was observed in the quadrants where the pathway was functioning. Our findings show that injection of a mixture composed of ICG and viscoelastic solution into the Schlemm canal allows a clear visualization of the functioning portions of the conventional outflow pathway. In addition, a retrograde filling of structures presumably located into the iris was also recorded. Clinical Trial Registration. Our study is registered in ISRCTN registry, number 54005880, DOI 10.1186/ISRCTN54005880.

Intraocular lens implantation without the use of ophthalmic viscosurgical device

The purpose of this study was to determine whether single-piece hydrophilic acrylic intraocular lens can be safely implanted without the use of ophthalmic viscosurgical devices. This retrospective study comprised 100 eyes having phacoemulsification and intraocular lens implantation without the use of ophthalmic viscosurgical device. 80 eyes with the use of a viscosurgical device are used as control group. In this intraocular lens implantation technique, the anterior chamber was maintained with an irrigation cannula and intraocular lens was implanted with a lens injector. Visual acuity, corneal clarity and edema, intraocular pressure, and corneal endothelial cell count were evaluated preoperatively and postoperatively at days 1, 7, and 30. Corneal endothelial cell count was repeated 2 weeks after surgery. Complications of this technique were also evaluated. No significant complications of this intraocular lens implantation technique, such as posterior capsule rupture, intraocular lens buttonholing, zonular dialysis, Descemet's tear/detachment, occurred. On the seventh postoperative day, 90 % of eyes achieved 20/20 or better vision. There was no difference in corneal endothelial cell loss between viscoelastic device-used and not-used cases (p = 0.356). When implanting intraocular lens without the use of ophthalmic viscosurgical device, significant intraoperative complications did not occur. The possible advantages are shortened surgery time, avoidance of postoperative IOP spike from ocular viscosurgical device (OVD) remnant, and reduced cost.

Prefilled syringes and usability of ophthalmic viscosurgical devices

Purpose

To examine the influence of the configuration of prefilled syringes on the usability of ophthalmic viscosurgical devices (OVDs).

Setting

Department of Ophthalmology, Jikei University School of Medicine, Tokyo, Japan.

Design

Experimental study.

Methods

The 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.

Results

The 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.

Conclusion

It 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.