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Silicone oil content in ophthalmic viscosurgical devices
Silicone oil content in ophthalmic viscosurgical devices Arne Ohrstrom, MD, PhD, Bengt Svensson, MD, Susan Tegenfeldt, MD, Celadet Celiker, MD, Borje Lignell, MD Purpose: To examine the silicone oil content in 5 brands of ophthalmic viscoelastic devices (OVDs). Setting: Department of Ophthalmology, Central Hospital of Vasteras, Vasteras, Sweden. Methods: Phacoemulsification with intraocular lens (IOL) implantation was performed in 250 patients. Five brands of OVD were used, each one in 50 procedures. From each brand, 5 separate batches, each consisting of 10 syringes, were used. The 250 samples from identical batches were sent for spectrophotometric analysis, and 250 samples were used during surgery. Results: The silicone oil content varied significantly between the OVD brands. Conclusions: Silicone oil is a common contaminant in many OVDs. Ophthalmic viscosurgical devices with relatively low silicone oil content are available. J Cataract Refract Surg 2004; 30:1278–1280 2004 ASCRS and ESCRS
D
uring the past 10 years, surgeons have reported calcification of certain implanted intraocular lenses (IOLs),1–3 a problem particularly pronounced with the Hydroview威 lens (Bausch & Lomb). The manufacturer of this IOL suggested that the calcifications consisted of a layered mixture of calcium phosphate, fatty acids, and silicone. The silicone was found to have migrated from the gasket of the package to the IOL.4 The presence of silicone oil in an ophthalmic viscosurgical device (OVD) has been reported previously,5 although this is not normally declared in the description of OVD contents. We had the impression that the
amount of visible silicone oil varies greatly among OVD brands and aimed both to record the presence of visible silicone oil and to perform a spectrophotometric analysis of total silicone oil content in various brands.
Patients and Methods Phacoemulsification and IOL implantation were performed in 250 patients in an open study following approval by the Ethics Committee of the University of Uppsala. The 5 OVDs used in our clinic were tested. Patients were not informed because the study did not involve any divergence from our normal surgical procedures and no randomization was involved. Patients with concurrent ocular pathology were excluded.
Accepted for publication November 12, 2003. From the Department of Ophthalmology, Central Hospital, Vasteras 72189, Sweden. Presented at the ESCRS meeting, September 2002, Nice, France. This study was supported by a grant for cataract research by the County Council of Vastmanland, Sweden. None of the authors have a financial interest in any of the products mentioned. Reprint requests to Arne Ohrstrom, MD, Ogonkliniken Centrallasarettet, 72189 Vasteras, Sweden. E-mail: [email protected]. 2004 ASCRS and ESCRS Published by Elsevier Inc.
Methods The surgeon knew which OVD he or she was using, and thus the observations of visible silicone oil bubbles were not masked. The products were sodium hyaluronate 1.4% (Healon GV威, Pfizer), sodium hyaluronate 1.0% (Viscocorneal威, Corneal), sodium hyaluronate 1.4% (Allervisc威, Cornea Industrie), sodium hyaluronate 1.6% (Amvisc Plus, Bausch & Lomb), and sodium hyaluronate 3.0%–sodium chondroitin sulfate 4.0 (Viscoat威, Alcon). Five batches from each OVD were used to avoid the possibility of a single batch 0886-3350/04/$–see front matter doi:10.1016/j.jcrs.2003.11.037
SILICONE OIL CONTENT IN OPHTHALMIC VISCOSURGICAL DEVICES
Table 1. Mean silicone (Si) content, number of samples with measurable Si content, number below threshold, and number of positive visual observations of silicone oil droplets.
n
Below Threshold Si ⬍1 g/g
n Tot
Si-Oil Observations
1.96
22
28
50
2
Viscorneal
2.35
21
27
48
15
Allervisc
3.91
39
11
50
19
Amvisc
16.31
50
0
50
27
Viscoat
11.08
50
0
50
48
Mean Si g/g
Healon Gv
OVD
n ⫽ number of samples; n Tot ⫽ number of samples with measurable Si content; OVD ⫽ ophthalmic viscosurgical device
being nonrepresentative. When the capsular bag was filled with the OVD after phacoemulsification and prior to IOL implantation, the red reflex was used as a background for observation of visible droplets. The surgeon noted the presence or absence of silicone oil bubbles. A similar unused syringe from the same batch was sent to the SGAB analysis laboratory at the Lulea˚ Technical University, Sweden, for spectrophotometric analysis. These analyses were carried out by personnel unaware of the nature of the specimens to be analyzed. The analyses consisted of optical emission spectrometry of ionized plasma flowing through a field radiofrequency. Most elements emit a characteristic pattern of wavelengths at a critical temperature that can be used to identify and quantify substances. The machine used was an inductively coupled plasma-atomic emission spectrometer (ICP-AES ARL 3580), method EPA 200.7; the wavelength characteristic for silicon is 251.61 nm. The lower limit for detection was 1 g silicone/g.
Results In a large number of samples, the amount of silicone oil, if present, fell below the lower limit for detection (Table 1). This was especially true for Healon GV and Viscorneal, in which more than half of the samples had no detectable silicone oil. This complicated the statistical analysis of the data, and for this reason, the nonparametric Kruskall-Wallis test was used first, followed by a t test on those specimens with a measurable value. Nonparametric Test The Kruskall-Wallis test showed a significant difference (P⬍.001) in silicone oil content between (1) Healon GV and Viscorneal and (2) Viscoat and Amvisc, the latter 2 forming a high-content group and the former, a low-content group. Allervisc had a higher content than
Healon GV and Viscorneal (P⬍.05) and a significantly lower content than Viscoat and Amvisc (P⬍.01). Parametric Test The t test for independent data (Table 2) showed no significant differences between Healon GV, Viscorneal, and Allervisc. There was a highly significant difference (P⬍.0000001) between each of these and Amvisc and Viscoat, the latter 2 having higher content. Viscoat had a significantly lower concentration of silicone oil than Amvisc (P⬍.0001). Observations of Visible Oil The frequency of observed visible silicone oil bubbles was highest in Amvisc and Viscoat, correlating well with the measured content of the silicone oil (Table 1). These observations were unmasked and are not further analyzed.
Discussion Our results show significant variations in the silicone oil content of OVDs. The OVDs could be grouped roughly into high (Amvisc and Viscoat) and low silicone oil content (Healon GV, Viscorneal, and Allervisc). The Table 2. Basic descriptive statistics for the samples above threshold ⬎1 g/g. OVD
n
Mean
Min
Max
SD
Healon GV
22
1.96
1.05
4.53
0.82
Viscorneal
21
2.35
1.34
3.93
0.75
Allervisc
39
3.91
1.16
27.23
4.51
Amvisc
50
16.31
4.71
35.25
7.81
Viscoat
50
11.08
3.61
27.06
5.24
n ⫽ number of samples; OVD ⫽ ophthalmic viscosurgical device
J CATARACT REFRACT SURG—VOL 30, JUNE 2004
1279
SILICONE OIL CONTENT IN OPHTHALMIC VISCOSURGICAL DEVICES
measured concentration of silicone oil correlated with the number of observations of visible silicone oil bubbles. It is well known that silicone oil is used as a lubricant for the syringe used to deliver OVDs. However, the OVD injected into the eye should not be contaminated with this oil. The presence of oil is not apparent from content declarations of the various products. Experience from vitreoretinal surgery has shown that silicone oil reacts adversely with silicone IOLs, for example, by adhering to the surface.6 The manufacturer of the Hydroview lens has implicated silicone in the calcification of this soft acrylic polyhema lens (D. Schonfeld, “Researchers: Source of Hydroview IOL Calcification Found,” Ocular Surgery News, November 14, 2001, page 77).3 Others have suggested a role for silicone oil in IOL opacification.6,7 These hypotheses have not been proved conclusively, but as shown here, OVDs may be a source of intraocular silicone oil. Although the OVD should be completely removed from the eye at the conclusion of the procedure in most intraocular surgeries, this is not always the case. There may be some OVD inadvertently left behind the IOL or, in some cases of complicated cataract or glaucoma surgery or trauma, the surgeon may intentionally leave a small amount of OVD in the eye. Furthermore, new IOLs, made of new materials for which interactions with silicone oil are unknown, are frequently introduced.
1280
Because of these factors, silicone oil contamination appears to be an unnecessary risk. There is a small amount of silicone oil present in almost all OVDs. The easiest way to avoid leaving silicone oil in the eye following surgery is to use an OVD with a low content of silicone oil.
References 1. Bucher PJ, Bu¨chi ER, Daicker BC. Dystrophic calcification of an implanted hydroxymethylacrylate intraocular lens. Arch Ophthalmol 1995; 113:1431–1435 2. Werner L, Apple DJ, Escobar-Gomez M, et al. Postoperative deposition of calcium on the surfaces of a hydrogel intraocular lens. Ophthalmology 2000; 107:2179–2185 3. Pandey SK, Werner L, Apple DJ, Gravel JP. Calcium precipitation on the optical surfaces of a foldable intraocular lens: A clinicopathological correlation. Arch Ophthalmol 2002; 120:391–393 4. Ohrstrom A, Behndig A. Silicone oil bubbles in ophthalmic viscosurgical devices [letter]. J Cataract Refract Surg 2002; 28:389 5. Apple DJ, Federman JL, Krolicki TH, et al. Irreversible silicone oil adhesion to silicone intraocular lenses; a clinicopathological analysis. Ophthalmology 1996; 103:1555– 1561; discussion by TM Aaberg Sr, 1561–1562 6. Arthur SN, Peng Q, Apple DJ, et al. Effect of heparin surface modification in reducing silicone oil adherence to various intraocular lenses. J Cataract Refract Surg 2001; 27:1662–1669 7. McLoone E, Mahon G, Archer D, Best R. Silicone oil–intraocular lens interaction: which lens to use? Br J Ophthalmol 2001; 85:543–545
J CATARACT REFRACT SURG—VOL 30, JUNE 2004
D
uring the past 10 years, surgeons have reported calcification of certain implanted intraocular lenses (IOLs),1–3 a problem particularly pronounced with the Hydroview威 lens (Bausch & Lomb). The manufacturer of this IOL suggested that the calcifications consisted of a layered mixture of calcium phosphate, fatty acids, and silicone. The silicone was found to have migrated from the gasket of the package to the IOL.4 The presence of silicone oil in an ophthalmic viscosurgical device (OVD) has been reported previously,5 although this is not normally declared in the description of OVD contents. We had the impression that the
amount of visible silicone oil varies greatly among OVD brands and aimed both to record the presence of visible silicone oil and to perform a spectrophotometric analysis of total silicone oil content in various brands.
Patients and Methods Phacoemulsification and IOL implantation were performed in 250 patients in an open study following approval by the Ethics Committee of the University of Uppsala. The 5 OVDs used in our clinic were tested. Patients were not informed because the study did not involve any divergence from our normal surgical procedures and no randomization was involved. Patients with concurrent ocular pathology were excluded.
Accepted for publication November 12, 2003. From the Department of Ophthalmology, Central Hospital, Vasteras 72189, Sweden. Presented at the ESCRS meeting, September 2002, Nice, France. This study was supported by a grant for cataract research by the County Council of Vastmanland, Sweden. None of the authors have a financial interest in any of the products mentioned. Reprint requests to Arne Ohrstrom, MD, Ogonkliniken Centrallasarettet, 72189 Vasteras, Sweden. E-mail: [email protected]. 2004 ASCRS and ESCRS Published by Elsevier Inc.
Methods The surgeon knew which OVD he or she was using, and thus the observations of visible silicone oil bubbles were not masked. The products were sodium hyaluronate 1.4% (Healon GV威, Pfizer), sodium hyaluronate 1.0% (Viscocorneal威, Corneal), sodium hyaluronate 1.4% (Allervisc威, Cornea Industrie), sodium hyaluronate 1.6% (Amvisc Plus, Bausch & Lomb), and sodium hyaluronate 3.0%–sodium chondroitin sulfate 4.0 (Viscoat威, Alcon). Five batches from each OVD were used to avoid the possibility of a single batch 0886-3350/04/$–see front matter doi:10.1016/j.jcrs.2003.11.037
SILICONE OIL CONTENT IN OPHTHALMIC VISCOSURGICAL DEVICES
Table 1. Mean silicone (Si) content, number of samples with measurable Si content, number below threshold, and number of positive visual observations of silicone oil droplets.
n
Below Threshold Si ⬍1 g/g
n Tot
Si-Oil Observations
1.96
22
28
50
2
Viscorneal
2.35
21
27
48
15
Allervisc
3.91
39
11
50
19
Amvisc
16.31
50
0
50
27
Viscoat
11.08
50
0
50
48
Mean Si g/g
Healon Gv
OVD
n ⫽ number of samples; n Tot ⫽ number of samples with measurable Si content; OVD ⫽ ophthalmic viscosurgical device
being nonrepresentative. When the capsular bag was filled with the OVD after phacoemulsification and prior to IOL implantation, the red reflex was used as a background for observation of visible droplets. The surgeon noted the presence or absence of silicone oil bubbles. A similar unused syringe from the same batch was sent to the SGAB analysis laboratory at the Lulea˚ Technical University, Sweden, for spectrophotometric analysis. These analyses were carried out by personnel unaware of the nature of the specimens to be analyzed. The analyses consisted of optical emission spectrometry of ionized plasma flowing through a field radiofrequency. Most elements emit a characteristic pattern of wavelengths at a critical temperature that can be used to identify and quantify substances. The machine used was an inductively coupled plasma-atomic emission spectrometer (ICP-AES ARL 3580), method EPA 200.7; the wavelength characteristic for silicon is 251.61 nm. The lower limit for detection was 1 g silicone/g.
Results In a large number of samples, the amount of silicone oil, if present, fell below the lower limit for detection (Table 1). This was especially true for Healon GV and Viscorneal, in which more than half of the samples had no detectable silicone oil. This complicated the statistical analysis of the data, and for this reason, the nonparametric Kruskall-Wallis test was used first, followed by a t test on those specimens with a measurable value. Nonparametric Test The Kruskall-Wallis test showed a significant difference (P⬍.001) in silicone oil content between (1) Healon GV and Viscorneal and (2) Viscoat and Amvisc, the latter 2 forming a high-content group and the former, a low-content group. Allervisc had a higher content than
Healon GV and Viscorneal (P⬍.05) and a significantly lower content than Viscoat and Amvisc (P⬍.01). Parametric Test The t test for independent data (Table 2) showed no significant differences between Healon GV, Viscorneal, and Allervisc. There was a highly significant difference (P⬍.0000001) between each of these and Amvisc and Viscoat, the latter 2 having higher content. Viscoat had a significantly lower concentration of silicone oil than Amvisc (P⬍.0001). Observations of Visible Oil The frequency of observed visible silicone oil bubbles was highest in Amvisc and Viscoat, correlating well with the measured content of the silicone oil (Table 1). These observations were unmasked and are not further analyzed.
Discussion Our results show significant variations in the silicone oil content of OVDs. The OVDs could be grouped roughly into high (Amvisc and Viscoat) and low silicone oil content (Healon GV, Viscorneal, and Allervisc). The Table 2. Basic descriptive statistics for the samples above threshold ⬎1 g/g. OVD
n
Mean
Min
Max
SD
Healon GV
22
1.96
1.05
4.53
0.82
Viscorneal
21
2.35
1.34
3.93
0.75
Allervisc
39
3.91
1.16
27.23
4.51
Amvisc
50
16.31
4.71
35.25
7.81
Viscoat
50
11.08
3.61
27.06
5.24
n ⫽ number of samples; OVD ⫽ ophthalmic viscosurgical device
J CATARACT REFRACT SURG—VOL 30, JUNE 2004
1279
SILICONE OIL CONTENT IN OPHTHALMIC VISCOSURGICAL DEVICES
measured concentration of silicone oil correlated with the number of observations of visible silicone oil bubbles. It is well known that silicone oil is used as a lubricant for the syringe used to deliver OVDs. However, the OVD injected into the eye should not be contaminated with this oil. The presence of oil is not apparent from content declarations of the various products. Experience from vitreoretinal surgery has shown that silicone oil reacts adversely with silicone IOLs, for example, by adhering to the surface.6 The manufacturer of the Hydroview lens has implicated silicone in the calcification of this soft acrylic polyhema lens (D. Schonfeld, “Researchers: Source of Hydroview IOL Calcification Found,” Ocular Surgery News, November 14, 2001, page 77).3 Others have suggested a role for silicone oil in IOL opacification.6,7 These hypotheses have not been proved conclusively, but as shown here, OVDs may be a source of intraocular silicone oil. Although the OVD should be completely removed from the eye at the conclusion of the procedure in most intraocular surgeries, this is not always the case. There may be some OVD inadvertently left behind the IOL or, in some cases of complicated cataract or glaucoma surgery or trauma, the surgeon may intentionally leave a small amount of OVD in the eye. Furthermore, new IOLs, made of new materials for which interactions with silicone oil are unknown, are frequently introduced.
1280
Because of these factors, silicone oil contamination appears to be an unnecessary risk. There is a small amount of silicone oil present in almost all OVDs. The easiest way to avoid leaving silicone oil in the eye following surgery is to use an OVD with a low content of silicone oil.
References 1. Bucher PJ, Bu¨chi ER, Daicker BC. Dystrophic calcification of an implanted hydroxymethylacrylate intraocular lens. Arch Ophthalmol 1995; 113:1431–1435 2. Werner L, Apple DJ, Escobar-Gomez M, et al. Postoperative deposition of calcium on the surfaces of a hydrogel intraocular lens. Ophthalmology 2000; 107:2179–2185 3. Pandey SK, Werner L, Apple DJ, Gravel JP. Calcium precipitation on the optical surfaces of a foldable intraocular lens: A clinicopathological correlation. Arch Ophthalmol 2002; 120:391–393 4. Ohrstrom A, Behndig A. Silicone oil bubbles in ophthalmic viscosurgical devices [letter]. J Cataract Refract Surg 2002; 28:389 5. Apple DJ, Federman JL, Krolicki TH, et al. Irreversible silicone oil adhesion to silicone intraocular lenses; a clinicopathological analysis. Ophthalmology 1996; 103:1555– 1561; discussion by TM Aaberg Sr, 1561–1562 6. Arthur SN, Peng Q, Apple DJ, et al. Effect of heparin surface modification in reducing silicone oil adherence to various intraocular lenses. J Cataract Refract Surg 2001; 27:1662–1669 7. McLoone E, Mahon G, Archer D, Best R. Silicone oil–intraocular lens interaction: which lens to use? Br J Ophthalmol 2001; 85:543–545
J CATARACT REFRACT SURG—VOL 30, JUNE 2004