- Email: [email protected]
Clinical results of phacoemulsification with the use of Healon5 or Viscoat
Clinical results of phacoemulsification with the use of Healon5 or Viscoat Manfred R. Tetz, MD, Mike P. Holzer, MD, Kerstin Lundberg, Gerd U. Auffarth, MD, Reinhard O.W. Burk, MD, Friedrich E. Kruse, MD ABSTRACT Purpose: To compare the ophthalmic viscosurgical devices Healon姞5 (viscoadaptive) and Viscoat姞 (dispersive) regarding their overall clinical performance during phacoemulsification and posterior chamber intraocular lens (IOL) implantation as well as their influence on intraocular pressure (IOP). Setting: Department of Ophthalmology, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany. Methods: In this prospective randomized patient- and observer-masked clinical study, the performance of Healon5 (sodium hyaluronate 2.3%) and Viscoat (sodium hyaluronate 3.0%– chondroitin sulfate 4.0%) was assessed by 3 surgeons during cataract surgery in 90 patients. Surgeons used a 5-point scale for the subjective assessment of the ease of injection, maintenance capacity during continuous curvilinear capsulorhexis, remaining capacity during phacoemulsification, facilitation of IOL implantation, removal from the eye, transparency, and overall performance throughout surgery. Intraocular pressure was measured preoperatively and 24 hours and 7 days postoperatively. Best corrected visual acuity was assessed preoperatively and 7 days postoperatively. Results: Overall intraoperative product performance was assessed as good or very good in 34 of 44 patients (77%) in the Healon5 group and in 16 of 46 patients (35%) in the Viscoat group (P ⬍ .001). Retention in the anterior chamber was graded good or very good in 36 patients (82%) in the Healon5 group and in 23 (50%) in the Viscoat group (P ⫽ .001). There were no statistically significant between-group differences in mean IOP preoperatively and 24 hours postoperatively. Conclusions: Surgeons graded Healon5 better than Viscoat in overall surgical performance and retention in the anterior chamber during phacoemulsification. These data support that Healon5 adapts to each step during surgery. J Cataract Refract Surg 2001; 27:416 – 420 © 2001 ASCRS and ESCRS
T
he introduction of ophthalmic viscosurgical devices (OVDs) 20 years ago1 substantially improved the efficacy and safety of cataract surgery and intraocular Accepted for publication June 9, 2000. Reprint requests to Manfred R. Tetz, MD, Department of Ophthalmology, Humboldt University Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany. © 2001 ASCRS and ESCRS Published by Elsevier Science Inc.
lens (IOL) implantation. A variety of OVDs are now available, and each possesses specific chemical and physical properties leading to different intraoperative behavior.2 The change from extracapsular cataract extraction to phacoemulsification in recent years has placed new demands on the performance of OVDs. This applies specifically to features influencing phacoemulsification and foldable IOL implantation techniques. In addition, 0886-3350/01/$–see front matter PII S0886-3350(00)00569-1
PHACOEMULSIFICATION WITH HEALON5 OR VISCOAT
maximum protection of the endothelium remains one of the most important functions of OVDs. This study compared the intraoperative features, including behavior during phacoemulsification, of 2 OVDs: Healon威5 (sodium hyaluronate 2.3%) and Viscoat威 (sodium hyaluronate 3.0%– chondroitin sulfate 4.0%), essentially the only ones that may remain in the anterior chamber during phacoemulsification.
Patients and Methods This open randomized parallel-group study compared Healon5 and Viscoat during cataract surgery with IOL implantation. The characteristics of the 2 OVDs are shown in Table 1. Both patients and observers were masked at the preoperative and postoperative examinations as to which OVD was used during surgery. The surgeon knew which OVD was being used by recognizing the different biophysical behaviors of the 2 substances. The study protocol was approved by an independent ethics committee, and the study was conducted in accordance with the Declaration of Helsinki. Patients provided informed consent before participation. Patients of either sex who were at least 40 years old and required cataract surgery were included. Patients were excluded if they had glaucoma, a preoperative dilated pupil diameter smaller than 5.0 mm, proliferative diabetic retinopathy, or a history of uveitis. Table 1. Physical and biochemical properties of Healon5 and Viscoat. Property
Healon5
Viscoat
Manufacturer
Pharmacia & Upjohn
Alcon
Ingredients per mL
23 mg NaHa
1. 40 mg CDS 2. 30 mg NaHa
Source
Rooster combs
1. Shark fin cartilage 2. Bacterial fermentation
Concentration (%)
2.3
1. 4.0 2. 3.0
Viscosity (mPas)
7 000 000
40 000
Molecular weight (Dalton)
4 000 000
1. 22 500 2. ⬎500 000
Osmolarity (mOsm/L)
309
330
pH value
7.0–7.5
7.25 ⫾ 0.25
Storage (°C)
2–8
2–8
The surgeons subjectively assessed the clinical performance (efficacy) during surgery of Healon5 and Viscoat using 7 criteria: ease of injection; maintenance capacity during continuous curvilinear capsulorhexis (CCC); remaining capacity during phacoemulsification; facilitation of IOL implantation; removal of the OVD from the eye at the end of surgery; transparency; overall performance throughout surgery. Ratings were done using a 5-point scale: very poor ⫽ 1; poor ⫽ 2; average ⫽ 3; good ⫽ 4; very good ⫽ 5. The scores were documented on a data sheet immediately after surgery. Phacoemulsification and removal times for every operation were noted. The OVDs were removed using the rock ’n roll technique described by Arshinoff 3 (S.A. Arshinoff, MD, “Rock ’n Roll Removal of Healon GV,” film presented at the Symposium on Cataract, IOL and Refractive Surgery, Seattle, Washington, USA, June 1996). Safety parameters and variables included intraocular pressure (IOP) measurement preoperatively and 24 hours and 7 days postoperatively using Goldmann applanation tonometry. Best corrected visual acuity was determined using Snellen charts preoperatively and 7 days postoperatively. A slitlamp examination was performed at all visits except on the day of surgery. Additional observations, complications, and adverse events defined by the study protocol were recorded throughout the study. Statistical Analysis Data were assessed using an observed-case analysis that included all patients receiving an OVD and providing data. A Wilcoxon rank sum test stratified by surgeon was used to test the null hypothesis of no difference between groups in the overall assessment (primary objective) of the OVDs during surgery against the alternative hypothesis that there was a between-group difference. The performance at individual intraoperative steps as well as transparency of the OVD (secondary objectives) were also tested using the Wilcoxon rank sum test stratified by surgeon. All statistical tests were 2-sided at the 5% significance level.
Results
CDS ⫽ chondroitin sulfate; NaHa ⫽ sodium hyaluronate
Ninety patients, 44 in the Healon5 group and 46 in the Viscoat group, were included in the study. The mean patient age was 72 years in both groups. Women made
J CATARACT REFRACT SURG—VOL 27, MARCH 2001
417
PHACOEMULSIFICATION WITH HEALON5 OR VISCOAT
up 48% of the Healon5 group and 46% of the Viscoat group. The observed-cases analysis showed that the overall intraoperative product performance was assessed as good or very good in 34 patients (77%) in the Healon5 group and 16 (35%) in the Viscoat group (P ⬍ .001). Seven eyes (3 Healon5; 4 Viscoat) did not fulfill the study protocol requiring an intact posterior capsule, use of only 1 OVD, and notification of intraocular complications (Table 2). An analysis excluding these cases yielded results similar to those of the total observed-case analysis: good or very good in 31 of 41 (75.5%) in the Healon5 group and 15 of 42 (36%) in the Viscoat group (P ⬍ .001). Thus, all 90 eyes were included in the trial analyses. The scoring of the 3 surgeons for all 7 criteria was significantly better in the Healon5 group than in the Viscoat group (P ⬍ .003) (Table 3 and Figures 1 to 7). The mean removal time was 53 seconds ⫾ 25 (SD) in the Healon5 group and 76 ⫾ 30 seconds in the Viscoat group. The difference between groups was statistically significantly (P ⬍ .001). There was no difference between mean IOP preoperatively and 24 hours postoperatively. Two patients in the Healon5 group had an IOP greater than 35 mm Hg (37 and 44 mm Hg) 24 hours postoperatively. No adverse outcomes were recorded. Best corrected visual acuity improved from between light perception and 0.6 preoperatively to between 0.4 and 1.0 7 days postoperatively. Complications and adverse events were few and comparable between the 2 groups.
Table 2. Number of patients with deviations from the original protocol or intraoperative complications. Alteration/Complication
Healon5
Viscoat
Posterior capsule break; anterior vitrectomy
1
1
Posterior capsulorhexis for dense posterior subcapsular cataract
2
0
Additional use of Healon GV to manage surgery
0
2
Corneal heating at incision site during phaco
0
1
418
Discussion Ophthalmic viscosurgical devices are the most commonly used tool to maintain space in the anterior chamber during cataract surgery. The compartmentalization during phacoemulsification may be one of the most important mechanical protecting features of OVDs. Many OVDs are commercially available, but no single product gives the surgeon full support during all steps of surTable 3. Patients with good or very good scores for objective assessment of Healon5 or Viscoat during surgery; observed-case analysis. Number of Patients (%) Parameter
Healon5 (n ⴝ 44)
Viscoat (n ⴝ 46)
Ease of injection
34 (77)*
27 (59)
Anterior chamber maintenance
†
34 (77)
31 (67)
Retention during phaco
36 (82)*
23 (50)
Facilitate IOL implantation
36 (82)*
20 (43)
Ease of removal
22 (50)*
Transparency
29 (66)*
13 (28)
Overall performance
34 (77)*
16 (35)
0
*P ⬍ .001 P ⬍ .003, Healon5 versus Viscoat
†
Figure 1. (Tetz) Overall performance of Healon5 and Viscoat.
Figure 2. (Tetz) Assessment of the injection of Healon5 and Viscoat.
J CATARACT REFRACT SURG—VOL 27, MARCH 2001
PHACOEMULSIFICATION WITH HEALON5 OR VISCOAT
Figure 3. (Tetz) Assessment of the maintenance capacity of Hea-
Figure 4. (Tetz) Assessment of the remaining capacity of Healon5
lon5 and Viscoat.
and Viscoat.
Figure 5. (Tetz) Assessment of the facilitation during IOL implan-
Figure 6. (Tetz) Assessment of the removal of Healon5 and
tation of Healon5 and Viscoat.
Viscoat.
gery.4 Ophthalmic viscosurgical devices vary markedly in their ability to remain in the anterior chamber during phacoemulsification.5,6 Viscoat was among the first OVDs reported to remain in the anterior chamber during phacoemulsification. Depending on their rheological properties (ie, viscosity, elasticity, and pseudoplasticity), OVDs also behave differently during injection, CCC, IOL implantation, and their removal.4,7 Agents with a high zero-shear viscosity provide good maintenance capacity, which is important during CCC and IOL implantation.7,8 Products with low viscosity at high shear rates simplify injection. However, the high zero-shear viscosity products currently available tend to leave the anterior chamber rapidly during the turbulent flow present during phacoemulsification. Although low zero-shear viscosity and “sticky” OVDs remain in the anterior chamber during phacoemulsification, they are more difficult to inject and remove. Based on the results of preclinical studies performed at Pharmacia & Upjohn in Sweden and at the Storm Eye Institute, Charleston, South Carolina, USA (unpublished data), Healon5 was developed. Healon5 has a molecular weight of 4 million d, similar to that of Healon威 (sodium hyaluronate 1%), and a concentration of
Figure 7. (Tetz) Assessment of the transparency of Healon5 and Viscoat.
23 mg of sodium hyaluronate per milliliter; the concentration in Healon is 10 mg/mL and in Healon GV威 (sodium hyaluronate 1.4%), 14 mg/mL. The 2 OVDs used in our study were assessed by dividing the surgical procedure into 5 steps. Each step was evaluated. In addition, transparency and overall performance were scored. The results from these assessments show that Healon5 received significantly higher grades during the steps of cataract surgery and in transparency and overall performance. Ease of removal received the lowest score in both groups. A rating of good or very good was reported in 50% of the Healon5 cases and in none of the Viscoat cases. Ease of removal is influenced by the OVD’s phys-
J CATARACT REFRACT SURG—VOL 27, MARCH 2001
419
PHACOEMULSIFICATION WITH HEALON5 OR VISCOAT
ical and biochemical properties. The study protocol required total removal of the OVD, and removal time was significantly longer in the Healon5 group than in the Viscoat group (P ⬍ .001). After this study was concluded, the 2-compartment technique (TCT)9,10 was developed to reduce removal times. In a study of 30 patients, the authors found that removal of Healon5 took an average of 44 seconds using the rock ’n roll technique and 18 seconds using the TCT. Our study also examined the influence of the OVDs on IOP. Preoperatively and 24 hours postoperatively, there was no significant difference between the Healon5 and Viscoat groups in IOP. Potential IOP peaks during the first 24 hours after cataract surgery using OVDs were addressed in another study.11 Viscoat has dispersive properties that do not change during the steps of cataract surgery. It tends to coat tissues, forming a protective layer; however, this property makes removal of Viscoat more difficult. The rheological features of Healon5 are both cohesive and dispersive. Thus, the agent adapts to different surgical situations and turbulences. The adaptive character of Healon5 may be the result of its molecular structure. At low turbulence, long molecular chains are entangled and maintain space (as cohesive OVDs do); thus, Healon5 stays in the anterior chamber during capsulorhexis (nonturbulent situation). During phacoemulsification and the accompanying increase in turbulence, the entanglement forces probably exceed molecular binding forces. Healon5 fractures into smaller pieces and starts behaving as a dispersive OVD. Thus, during phacoemulsification, Healon5 partially remains in the anterior chamber whereas a cohesive OVD such as Healon GV immediately leaves the eye.8 This clinical performance study showed that in a subjective assessment, the viscoadaptive OVD Healon5 performed significantly better during cataract surgery than the more dispersive Viscoat. The introduction of Healon5 provides a new surgical tool for use during cataract surgery that may have other applications. How-
420
ever, as with any new device, learning curves are to be anticipated.
References 1. Miller D, Stegmann R. Use of Na-hyaluronate in anterior segment eye surgery (editorial). Am Intra-Ocular Implant Soc J 1980; 6:13–15 2. Arshinoff S. The physical properties of ophthalmic viscoelastics in cataract surgery. Ophthalmic Pract 1991; 9:81– 86 3. Arshinoff SA. Rock ’n roll removal of Healon GV. In: Proceedings of the 7th Annual National Ophthalmic Speakers Program. Montreal, Canada, Medico¨pea 1997 4. Arshinoff SA. The physical properties of ophthalmic viscoelastics in cataract surgery. Proceedings of the National Ophthalmic Speakers Program (NOSP). Montreal, Canada, Medico¨pea International Inc, 1992; 7–12 5. Arshinoff SA. Dispersive-cohesive viscoelastic soft shell technique. J Cataract Refract Surg 1999; 25:167–173 6. Arshinoff SA. Healon威5. In: Buratto L, Giardini P, Bellucci R, eds, Viscoelastics in Ophthalmic Surgery. Thorofare, NJ, Slack, 2000; 393–399 7. Dick B, Schwenn O, Pfeiffer N. Einteilung der viskoelastischen Substanzen fu¨r die Ophthalmochirurgie. Ophthalmologe 1999; 96:193–211 8. Eisner G. Use of viscoelastical tools in ophthalmic surgery. In: Eisner G, ed, Ophthalmic Viscosurgery; a Review of Standards, Techniques, and Applications. Montreal, Canada, Medico¨pea, 1986 9. Tetz MR, Holzer MP. Two-compartment technique to remove ophthalmic viscosurgical devices. J Cataract Refract Surg 2000; 26:641– 643 10. Tetz MR, Holzer MP. Healon威5: clinical performance and special removal technique (TCT). In: Buratto L, Giardini P, Bellucci R, eds, Viscoelastics in Ophthalmic Surgery. Thorofare, NJ, Slack, 2000; 401– 404 11. Holzer MP, Tetz MR, Auffarth GU, et al. Effect of Healon5 and 4 other viscoelastic substances on intraocular pressure and endothelium after cataract surgery. J Cataract Refract Surg 2001; 27:213–218
From the Departments of Ophthalmology, Humboldt University Berlin, Campus Virchow Klinikum, Berlin (Tetz, Holzer), and Ruprecht-Karls University Heidelberg, Heidelberg (Auffarth, Burk, Kruse), Germany, and Pharmacia & Upjohn, Uppsala, Sweden (Lundberg).
J CATARACT REFRACT SURG—VOL 27, MARCH 2001
T
he introduction of ophthalmic viscosurgical devices (OVDs) 20 years ago1 substantially improved the efficacy and safety of cataract surgery and intraocular Accepted for publication June 9, 2000. Reprint requests to Manfred R. Tetz, MD, Department of Ophthalmology, Humboldt University Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany. © 2001 ASCRS and ESCRS Published by Elsevier Science Inc.
lens (IOL) implantation. A variety of OVDs are now available, and each possesses specific chemical and physical properties leading to different intraoperative behavior.2 The change from extracapsular cataract extraction to phacoemulsification in recent years has placed new demands on the performance of OVDs. This applies specifically to features influencing phacoemulsification and foldable IOL implantation techniques. In addition, 0886-3350/01/$–see front matter PII S0886-3350(00)00569-1
PHACOEMULSIFICATION WITH HEALON5 OR VISCOAT
maximum protection of the endothelium remains one of the most important functions of OVDs. This study compared the intraoperative features, including behavior during phacoemulsification, of 2 OVDs: Healon威5 (sodium hyaluronate 2.3%) and Viscoat威 (sodium hyaluronate 3.0%– chondroitin sulfate 4.0%), essentially the only ones that may remain in the anterior chamber during phacoemulsification.
Patients and Methods This open randomized parallel-group study compared Healon5 and Viscoat during cataract surgery with IOL implantation. The characteristics of the 2 OVDs are shown in Table 1. Both patients and observers were masked at the preoperative and postoperative examinations as to which OVD was used during surgery. The surgeon knew which OVD was being used by recognizing the different biophysical behaviors of the 2 substances. The study protocol was approved by an independent ethics committee, and the study was conducted in accordance with the Declaration of Helsinki. Patients provided informed consent before participation. Patients of either sex who were at least 40 years old and required cataract surgery were included. Patients were excluded if they had glaucoma, a preoperative dilated pupil diameter smaller than 5.0 mm, proliferative diabetic retinopathy, or a history of uveitis. Table 1. Physical and biochemical properties of Healon5 and Viscoat. Property
Healon5
Viscoat
Manufacturer
Pharmacia & Upjohn
Alcon
Ingredients per mL
23 mg NaHa
1. 40 mg CDS 2. 30 mg NaHa
Source
Rooster combs
1. Shark fin cartilage 2. Bacterial fermentation
Concentration (%)
2.3
1. 4.0 2. 3.0
Viscosity (mPas)
7 000 000
40 000
Molecular weight (Dalton)
4 000 000
1. 22 500 2. ⬎500 000
Osmolarity (mOsm/L)
309
330
pH value
7.0–7.5
7.25 ⫾ 0.25
Storage (°C)
2–8
2–8
The surgeons subjectively assessed the clinical performance (efficacy) during surgery of Healon5 and Viscoat using 7 criteria: ease of injection; maintenance capacity during continuous curvilinear capsulorhexis (CCC); remaining capacity during phacoemulsification; facilitation of IOL implantation; removal of the OVD from the eye at the end of surgery; transparency; overall performance throughout surgery. Ratings were done using a 5-point scale: very poor ⫽ 1; poor ⫽ 2; average ⫽ 3; good ⫽ 4; very good ⫽ 5. The scores were documented on a data sheet immediately after surgery. Phacoemulsification and removal times for every operation were noted. The OVDs were removed using the rock ’n roll technique described by Arshinoff 3 (S.A. Arshinoff, MD, “Rock ’n Roll Removal of Healon GV,” film presented at the Symposium on Cataract, IOL and Refractive Surgery, Seattle, Washington, USA, June 1996). Safety parameters and variables included intraocular pressure (IOP) measurement preoperatively and 24 hours and 7 days postoperatively using Goldmann applanation tonometry. Best corrected visual acuity was determined using Snellen charts preoperatively and 7 days postoperatively. A slitlamp examination was performed at all visits except on the day of surgery. Additional observations, complications, and adverse events defined by the study protocol were recorded throughout the study. Statistical Analysis Data were assessed using an observed-case analysis that included all patients receiving an OVD and providing data. A Wilcoxon rank sum test stratified by surgeon was used to test the null hypothesis of no difference between groups in the overall assessment (primary objective) of the OVDs during surgery against the alternative hypothesis that there was a between-group difference. The performance at individual intraoperative steps as well as transparency of the OVD (secondary objectives) were also tested using the Wilcoxon rank sum test stratified by surgeon. All statistical tests were 2-sided at the 5% significance level.
Results
CDS ⫽ chondroitin sulfate; NaHa ⫽ sodium hyaluronate
Ninety patients, 44 in the Healon5 group and 46 in the Viscoat group, were included in the study. The mean patient age was 72 years in both groups. Women made
J CATARACT REFRACT SURG—VOL 27, MARCH 2001
417
PHACOEMULSIFICATION WITH HEALON5 OR VISCOAT
up 48% of the Healon5 group and 46% of the Viscoat group. The observed-cases analysis showed that the overall intraoperative product performance was assessed as good or very good in 34 patients (77%) in the Healon5 group and 16 (35%) in the Viscoat group (P ⬍ .001). Seven eyes (3 Healon5; 4 Viscoat) did not fulfill the study protocol requiring an intact posterior capsule, use of only 1 OVD, and notification of intraocular complications (Table 2). An analysis excluding these cases yielded results similar to those of the total observed-case analysis: good or very good in 31 of 41 (75.5%) in the Healon5 group and 15 of 42 (36%) in the Viscoat group (P ⬍ .001). Thus, all 90 eyes were included in the trial analyses. The scoring of the 3 surgeons for all 7 criteria was significantly better in the Healon5 group than in the Viscoat group (P ⬍ .003) (Table 3 and Figures 1 to 7). The mean removal time was 53 seconds ⫾ 25 (SD) in the Healon5 group and 76 ⫾ 30 seconds in the Viscoat group. The difference between groups was statistically significantly (P ⬍ .001). There was no difference between mean IOP preoperatively and 24 hours postoperatively. Two patients in the Healon5 group had an IOP greater than 35 mm Hg (37 and 44 mm Hg) 24 hours postoperatively. No adverse outcomes were recorded. Best corrected visual acuity improved from between light perception and 0.6 preoperatively to between 0.4 and 1.0 7 days postoperatively. Complications and adverse events were few and comparable between the 2 groups.
Table 2. Number of patients with deviations from the original protocol or intraoperative complications. Alteration/Complication
Healon5
Viscoat
Posterior capsule break; anterior vitrectomy
1
1
Posterior capsulorhexis for dense posterior subcapsular cataract
2
0
Additional use of Healon GV to manage surgery
0
2
Corneal heating at incision site during phaco
0
1
418
Discussion Ophthalmic viscosurgical devices are the most commonly used tool to maintain space in the anterior chamber during cataract surgery. The compartmentalization during phacoemulsification may be one of the most important mechanical protecting features of OVDs. Many OVDs are commercially available, but no single product gives the surgeon full support during all steps of surTable 3. Patients with good or very good scores for objective assessment of Healon5 or Viscoat during surgery; observed-case analysis. Number of Patients (%) Parameter
Healon5 (n ⴝ 44)
Viscoat (n ⴝ 46)
Ease of injection
34 (77)*
27 (59)
Anterior chamber maintenance
†
34 (77)
31 (67)
Retention during phaco
36 (82)*
23 (50)
Facilitate IOL implantation
36 (82)*
20 (43)
Ease of removal
22 (50)*
Transparency
29 (66)*
13 (28)
Overall performance
34 (77)*
16 (35)
0
*P ⬍ .001 P ⬍ .003, Healon5 versus Viscoat
†
Figure 1. (Tetz) Overall performance of Healon5 and Viscoat.
Figure 2. (Tetz) Assessment of the injection of Healon5 and Viscoat.
J CATARACT REFRACT SURG—VOL 27, MARCH 2001
PHACOEMULSIFICATION WITH HEALON5 OR VISCOAT
Figure 3. (Tetz) Assessment of the maintenance capacity of Hea-
Figure 4. (Tetz) Assessment of the remaining capacity of Healon5
lon5 and Viscoat.
and Viscoat.
Figure 5. (Tetz) Assessment of the facilitation during IOL implan-
Figure 6. (Tetz) Assessment of the removal of Healon5 and
tation of Healon5 and Viscoat.
Viscoat.
gery.4 Ophthalmic viscosurgical devices vary markedly in their ability to remain in the anterior chamber during phacoemulsification.5,6 Viscoat was among the first OVDs reported to remain in the anterior chamber during phacoemulsification. Depending on their rheological properties (ie, viscosity, elasticity, and pseudoplasticity), OVDs also behave differently during injection, CCC, IOL implantation, and their removal.4,7 Agents with a high zero-shear viscosity provide good maintenance capacity, which is important during CCC and IOL implantation.7,8 Products with low viscosity at high shear rates simplify injection. However, the high zero-shear viscosity products currently available tend to leave the anterior chamber rapidly during the turbulent flow present during phacoemulsification. Although low zero-shear viscosity and “sticky” OVDs remain in the anterior chamber during phacoemulsification, they are more difficult to inject and remove. Based on the results of preclinical studies performed at Pharmacia & Upjohn in Sweden and at the Storm Eye Institute, Charleston, South Carolina, USA (unpublished data), Healon5 was developed. Healon5 has a molecular weight of 4 million d, similar to that of Healon威 (sodium hyaluronate 1%), and a concentration of
Figure 7. (Tetz) Assessment of the transparency of Healon5 and Viscoat.
23 mg of sodium hyaluronate per milliliter; the concentration in Healon is 10 mg/mL and in Healon GV威 (sodium hyaluronate 1.4%), 14 mg/mL. The 2 OVDs used in our study were assessed by dividing the surgical procedure into 5 steps. Each step was evaluated. In addition, transparency and overall performance were scored. The results from these assessments show that Healon5 received significantly higher grades during the steps of cataract surgery and in transparency and overall performance. Ease of removal received the lowest score in both groups. A rating of good or very good was reported in 50% of the Healon5 cases and in none of the Viscoat cases. Ease of removal is influenced by the OVD’s phys-
J CATARACT REFRACT SURG—VOL 27, MARCH 2001
419
PHACOEMULSIFICATION WITH HEALON5 OR VISCOAT
ical and biochemical properties. The study protocol required total removal of the OVD, and removal time was significantly longer in the Healon5 group than in the Viscoat group (P ⬍ .001). After this study was concluded, the 2-compartment technique (TCT)9,10 was developed to reduce removal times. In a study of 30 patients, the authors found that removal of Healon5 took an average of 44 seconds using the rock ’n roll technique and 18 seconds using the TCT. Our study also examined the influence of the OVDs on IOP. Preoperatively and 24 hours postoperatively, there was no significant difference between the Healon5 and Viscoat groups in IOP. Potential IOP peaks during the first 24 hours after cataract surgery using OVDs were addressed in another study.11 Viscoat has dispersive properties that do not change during the steps of cataract surgery. It tends to coat tissues, forming a protective layer; however, this property makes removal of Viscoat more difficult. The rheological features of Healon5 are both cohesive and dispersive. Thus, the agent adapts to different surgical situations and turbulences. The adaptive character of Healon5 may be the result of its molecular structure. At low turbulence, long molecular chains are entangled and maintain space (as cohesive OVDs do); thus, Healon5 stays in the anterior chamber during capsulorhexis (nonturbulent situation). During phacoemulsification and the accompanying increase in turbulence, the entanglement forces probably exceed molecular binding forces. Healon5 fractures into smaller pieces and starts behaving as a dispersive OVD. Thus, during phacoemulsification, Healon5 partially remains in the anterior chamber whereas a cohesive OVD such as Healon GV immediately leaves the eye.8 This clinical performance study showed that in a subjective assessment, the viscoadaptive OVD Healon5 performed significantly better during cataract surgery than the more dispersive Viscoat. The introduction of Healon5 provides a new surgical tool for use during cataract surgery that may have other applications. How-
420
ever, as with any new device, learning curves are to be anticipated.
References 1. Miller D, Stegmann R. Use of Na-hyaluronate in anterior segment eye surgery (editorial). Am Intra-Ocular Implant Soc J 1980; 6:13–15 2. Arshinoff S. The physical properties of ophthalmic viscoelastics in cataract surgery. Ophthalmic Pract 1991; 9:81– 86 3. Arshinoff SA. Rock ’n roll removal of Healon GV. In: Proceedings of the 7th Annual National Ophthalmic Speakers Program. Montreal, Canada, Medico¨pea 1997 4. Arshinoff SA. The physical properties of ophthalmic viscoelastics in cataract surgery. Proceedings of the National Ophthalmic Speakers Program (NOSP). Montreal, Canada, Medico¨pea International Inc, 1992; 7–12 5. Arshinoff SA. Dispersive-cohesive viscoelastic soft shell technique. J Cataract Refract Surg 1999; 25:167–173 6. Arshinoff SA. Healon威5. In: Buratto L, Giardini P, Bellucci R, eds, Viscoelastics in Ophthalmic Surgery. Thorofare, NJ, Slack, 2000; 393–399 7. Dick B, Schwenn O, Pfeiffer N. Einteilung der viskoelastischen Substanzen fu¨r die Ophthalmochirurgie. Ophthalmologe 1999; 96:193–211 8. Eisner G. Use of viscoelastical tools in ophthalmic surgery. In: Eisner G, ed, Ophthalmic Viscosurgery; a Review of Standards, Techniques, and Applications. Montreal, Canada, Medico¨pea, 1986 9. Tetz MR, Holzer MP. Two-compartment technique to remove ophthalmic viscosurgical devices. J Cataract Refract Surg 2000; 26:641– 643 10. Tetz MR, Holzer MP. Healon威5: clinical performance and special removal technique (TCT). In: Buratto L, Giardini P, Bellucci R, eds, Viscoelastics in Ophthalmic Surgery. Thorofare, NJ, Slack, 2000; 401– 404 11. Holzer MP, Tetz MR, Auffarth GU, et al. Effect of Healon5 and 4 other viscoelastic substances on intraocular pressure and endothelium after cataract surgery. J Cataract Refract Surg 2001; 27:213–218
From the Departments of Ophthalmology, Humboldt University Berlin, Campus Virchow Klinikum, Berlin (Tetz, Holzer), and Ruprecht-Karls University Heidelberg, Heidelberg (Auffarth, Burk, Kruse), Germany, and Pharmacia & Upjohn, Uppsala, Sweden (Lundberg).
J CATARACT REFRACT SURG—VOL 27, MARCH 2001