RHEOLOGIC CHARACTERIZATION OF OPHTHALMIC VISCOSURGICAL DEVICES
CONTAINING SODIUM HYALURONATE AND SODIUM CHONDROITIN SULFATE Masoud
Jafari, PharmD, PhD Alcon Research Ltd, Fort Worth, Texas, USA and
Steve A. Arshinoff, MD Humber River Regional Hospital, University
of Toronto, Toronto, Canada, & McMaster University, Hamilton,
Ontario, Canada Disclosures:Dr. Jafari is an employee of Alcon and
Dr. Arshinoff is a consultant to Alcon. Alcon funded this study and
provided assistance with the preparation of this ePoster.
Slide 2
Introduction Background Subjectively, surgeons understand how
the intraoperative feel of one ophthalmic viscosurgical device
(OVD) differs from another, but Quantitative descriptions of the
physical characteristics of OVDs assist surgeons to understand OVDs
better, and provide critical information to help companies improve
OVDs. Objective The purpose of this study was to evaluate various
OVDs containing sodium hyaluronate or containing both sodium
hyaluronate and chondroitin sulfate, in terms of: Rheological
properties (related to deformation and flow), and
Cohesive/dispersive properties (related to whether an OVD holds
together or can be easily pulled apart). 2
Slide 3
Methods I Rheology: Some OVDs behave like a fluid when
manipulated, but then settle into a nearly solid state when at
rest; these characteristics indicate pseudoplasticity. To test
whether OVDs behaved more like liquids or more like solids under
various conditions, we used a Bohlin Controlled Stress Rheometer
(Bohlin Rheologic AB; Lund, Sweden), at the standard and surgically
relevant temperature of 25 C, to test OVD viscosities under zero
shear (ie, at rest), and OVD viscosities under shear rates from
0.001 seconds -1 (very slow) to 1000 seconds -1 (very fast), to
yield a pseudoplasticity curve 3
Slide 4
Methods II Cohesion/Dispersion Evaluation: OVDs were evaluated
in terms of the Cohesion-Dispersion Index, which is A value between
0 (very dispersive) and 100 (very cohesive) Reported as the % OVD
aspirated / 100 mm Hg Derived by testing how much of a 0.5-ml
sample of OVD is aspirated into a pipette tip when a given amount
of vacuum is applied, using the automated model as described in the
referenced article. 1 1. Poyer JF, Chan KY, Arshinoff SA.
Quantitative method to determine the cohesion of viscoelastic
agents by dynamic aspiration. J Cataract Refractive Surg.
1998:24(8);1130-1135 vacuum line pipette tip OVD 4
Slide 5
Materials: OVDs Evaluated OVDManufacturer Polysaccharide
Content Hyaluronic AcidChondroitin Sulfate Total Poly- saccharide,
% % MW, kDa %MW, Da Viscoat OVD Alcon (USA) 3%5004%22,5007%
DisCoVisc OVD Alcon (USA) 1.65%17004%22,5005.65% Ixium HCS OVD LCA
Pharmaceutical (France) 2%24002%50,0004% Vitrax OVD AMO (USA)
3%645-- 3% Opegan Hi OVD Santen (Japan) 1%2000-- 1% Healon OVD AMO
(USA) 1%4000-- 1% Beyond differences in polysaccharide content as
shown above, these OVDs also differ in their excipients, such as
salts. *We had intended to test Chondrovisc OVD, but samples from
the Turkish manufacturer (AkAkin Ilac San) were not available to us
in the US. 5
Slide 6
Results: CohesionDispersion Index More Cohesive More Dispersive
0 = max dispersive 100 = max cohesive 6
Slide 7
Results: Zero-Shear Viscosity More Viscous Less Viscous 7
Slide 8
Less viscous (more thinning) Ixium HCS Results: Rheological
Profiles The figure below shows how viscosity decreased as shear
rate increased for the OVDs containing hyaluronic acid (HA) or
containing both HA and chondroitin sulfate (CS): The 2 OVDs without
CS and with high-molecular-weight, low-concentration HA (Opegan Hi
OVD and Healon OVD) were most susceptible to shear thinning (curves
begin to drop with a steeper slope at arrows). The OVD without CS
and with low-molecular-weight, high-concentration HA (Vitrax OVD)
had the lowest viscosity at low shear, and low shear thinning. The
3 OVDs with both HA and CS (DisCoVisc OVD, Viscoat OVD, and Ixium
HCS OVD) had intermediate viscosity at low shear and were resistant
to shear thinning. 8
Slide 9
Discussion/Conclusions: OVDs with only Hyaluronic Acid as
Polysaccharide Study Results: OVDs with only hyaluronic acid as
polysaccharide exhibitedClinical Implications zero-shear
viscosities from 45,000 Pa.s for lower- molecular-weight OVDs, to
240,000 to 426,000 Pa.s for higher-molecular-weight OVDs These high
zero-shear viscosities are best to create and maintain space
maintenance during surgery in the absence of high fluid turbulence.
Cohesion-Dispersion Indices (CDIs), in units of % aspirated / 100
mm Hg, ranging from 2.8% for lower-molecular- weight OVDs, to 32% -
60% for higher- molecular-weight OVDs Low CDI value indicates high
retention despite fluid turbulence, but difficult removal during
irrigation/aspiration. High CDI values indicate that the OVDs stay
together when pulled and so are easily aspirated at the end of
surgery, but perhaps also during turbulent phases of phaco. 9
Slide 10
Study Results: OVDs with both hyaluronic acid and chondroitin
sulfate exhibited..Clinical Implications zero-shear viscosities
from 50,000 to 250,000 mPa.s These OVDs are available with a wide
range of initial space-maintaining properties. Cohesion-Dispersion
Indices (CDIs) ranging from 3.4% to 21% aspirated per 100 mm Hg Low
CDIs correlate to more dispersive characteristics, with longer
retention in the anterior chamber of the eye during turbulent
phases of surgery, and easier breakup of OVDs when pulled more
difficult removal at the end of surgery. Discussion/Conclusions:
OVDs with both Hyaluronic Acid and Chondroitin Sulfate 10
