- Email: [email protected]
Corneal endothelial cell protection during phacoemulsification
Corneal endothelial cell protection during phacoemulsification Low- versus high-molecular-weight sodium hyaluronate Kazunori Miyata, MD, Shinji Maruoka, MD, Masaaki Nakahara, MD, Shinichiro Otani, MD, Ryohei Nejima, MD, Tomokazu Samejima, Shiro Amano, MD
Purpose: To compare the efficacy of low- and high-molecular-weight sodium hyaluronate in protecting corneal endothelial cells during phacoemulsification. Setting: Miyata Eye Hospital, Miyakonojo, Miyazaki, Japan. Methods: One hundred forty-nine eyes of 136 cataract patients were randomly assigned to have cataract surgery using sodium hyaluronate 1% with a low molecular weight (0.6 to 1.2 million d, Opegan姞) or sodium hyaluronate 1% with a high molecular weight (4 million d, Healon姞) during phacoemulsification. Each group was divided into 2 subgroups depending on the amount of ultrasound (% min) used during phacoemulsification, which was defined as the mean phacoemulsification energy (%) multiplied by phacoemulsification time (minutes). Corneal endothelial cell density was examined preoperatively and 3 months after surgery. The rate of cell loss was compared between the subgroups in the Opegan group and the Healon group. Results: In the subgroups with ultrasound of 50% min or less, the mean rate of endothelial cell loss 3 months after surgery was 3.2% ⫾ 4.1% (SD) in the Opegan group and 5.9% ⫾ 5.3% in the Healon group (P ⫽ .0214). In the subgroups with ultrasound over 50% min, the mean rate of endothelial cell loss 3 months after surgery was 7.5% ⫾ 10.6% in the Opegan group and 14.8 ⫾ 9.0% in the Healon group (P ⫽ .0029). Conclusions: The results suggest that Opegan is more effective than Healon in protecting corneal endothelial cells during phacoemulsification regardless of the amount of ultrasound energy used. J Cataract Refract Surg 2002; 28:1557–1560 © 2002 ASCRS and ESCRS
O
phthalmic viscosurgical devices (OVDs) play a crucial role in cataract surgery today by protecting corneal endothelial cells and maintaining space in the capsular bag or anterior chamber. Among various commercially available OVDs, sodium hyaluronate–chondroitin sulfate has been shown to be the most effective in remaining adherent to and protecting the corneal endothelium during phacoemulsification.1–3 However, this Accepted for publication May 1, 2002. Reprint requests to Shiro Amano, MD, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655 Japan. E-mail: [email protected]. © 2002 ASCRS and ESCRS Published by Elsevier Science Inc.
OVD can remain in the anterior chamber even after meticulous irrigation/aspiration (I/A) because of its low cohesiveness and can elevate intraocular pressure (IOP).1,2,4,5 Because sodium hyaluronate with a low molecular weight has characteristics between sodium hyaluronate with a high molecular weight and sodium hyaluronate–chondroitin sulfate, it can protect the corneal endothelium during phacoemulsification and can be removed at the end of surgery more easily than sodium hyaluronate–chondroitin sulfate. In this study, we compared the efficacy of lowand high-molecular-weight sodium hyaluronate 1% 0886-3350/02/$–see front matter PII S0886-3350(02)01540-7
CORNEAL ENDOTHELIAL CELL PROTECTION DURING PHACOEMULSIFICATION
in protecting corneal endothelial cells during phacoemulsification.
Patients and Methods This study comprised 146 eyes of 133 cataract patients who had phacoemulsification and posterior chamber intraocular lens (IOL) implantation at Miyata Eye Hospital from August 1995 through July 1996. No patient had systemic or ocular complications preoperatively. The patients were randomly assigned to have cataract surgery using sodium hyaluronate 1% with a low molecular weight (0.6 to 1.2 million d, Opegan威) or sodium hyaluronate 1% with a high molecular weight (4 million d, Healon威) during phacoemulsification. All patients were operated on by the same surgeon (K.M.), who had had similar experience with both OVDs. After topical anesthesia of lidocaine hydrochloride 4% (Xylocaine威) was administered, a superior 4.1 mm corneoscleral incision was made. About 0.1 mL of Opegan or Healon was injected into the anterior chamber. A capsulorhexis was created and hydrodissection performed. For phacoemulsification, the divide-and-conquer technique was used and the lens cortex was suctioned with I/A. The vacuum pressure and the aspiration rate during phacoemulsification were 80 mm Hg and 17 mL/min, respectively, before the lens nucleus was divided and 350 mm Hg and 20 mL/min, respectively, after the lens nucleus was divided. In both groups, Healon was injected into the capsular bag and anterior chamber and an AcrySof威 foldable acrylic IOL (MA60, Alcon) was implanted in the capsular bag. The OVDs were completely aspirated from the capsular bag and anterior chamber with an I/A tip. No eye received IOP-lowering medication. The amount of ultrasound (% min) was defined as the mean phacoemulsification energy (%) multiplied by phacoemulsification time (minutes). Each group was divided into 2 subgroups based on whether the amount of ultrasound (% min) was over 50% min or under 50% min. The IOP was measured with a noncontact tonometer (Xpert Plus, Tomey) preoperatively and 1 day and 1 week after surgery. Endothelial
Table 1.
cell micrographs were obtained with a specular microscope (Konan Robo-CA, Konan). More than 100 cells were analyzed per eye using a cell analysis system (Fully Automatic Non Contact Cell Analyzer, Konan). The examiner who did the endothelial cell count and preoperative and postoperative follow-ups was masked as to which group the eye belonged. The Mann-Whitney U test and unpaired t test were used to compare intraoperative and postoperative parameters between the subgroups. A P value less than 0.05 was considered significant.
Results The patients’ characteristics and the intraoperative parameters in each group are shown in Table 1. In the Opegan group, the amount of ultrasound was 50% min or less in 41 eyes and over 50% min in 50 eyes. In the Healon group, the amount of ultrasound was 50% min or less in 27 eyes and over 50% min in 28 eyes. There was no statistically significant difference in any parameter between the corresponding subgroups (Table 1). The mean IOP in the Opegan group was 11.2 mm Hg ⫾ 3.5 (SD) (range 4 to 18 mm Hg) preoperatively, 10.5 ⫾ 4.2 mm Hg (range 4 to 19 mm Hg) 1 day after surgery, and 10.2 ⫾ 3.5 mm Hg (range 3 to 17 mm Hg) at 1 week. The mean IOP in the Healon group was 10.9 mm Hg ⫾ 2.8 (range 6 to 20 mm Hg), 11.2 ⫾ 3.0 mm Hg (range 5 to 18 mm Hg), and 9.4 ⫾ 2.3 mm Hg (range 5 to 15 mm Hg), respectively. No eye developed IOP greater than 21 mm Hg. In the groups in which the amount of ultrasound was 50% min or less, the mean rate of endothelial cell loss 3 months after surgery was 3.2% ⫾ 4.1% in the Opegan group and 5.9% ⫾ 5.3% in the Healon group (P ⫽ .0093) (Table 2). In the groups in which the amount of ultrasound was over 50% min, the rate of
Preoperative characteristics and intraoperative parameters. Ultrasound 50% Min or Less
Parameter Number of eyes
Opegan
Healon
41
27
Ultrasound Over 50% Min
P Value*
Opegan
Healon
50
28
P Value*
Mean age (y)
69.8 ⫾ 9.7
74.6 ⫾ 6.4
.12
75.6 ⫾ 8.0
74.3 ⫾ 8.7
.72
Mean irrigation solution used (mL)
57.3 ⫾ 16.9
55.5 ⫾ 14.5
.66
76.8 ⫾ 29.9
86.4 ⫾ 32.9
.13
7.3 ⫾ 1.1
7.5 ⫾ 1.0
.48
11.0 ⫾ 4.1
10.2 ⫾ 2.3
.39
Mean surgical time (min) Means ⫾ SD *Unpaired t test
1558
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CORNEAL ENDOTHELIAL CELL PROTECTION DURING PHACOEMULSIFICATION
Table 2.
Corneal endothelial cell density and cell loss rate. Ultrasound 50% Min or Less
Parameter
Ultrasound Over 50% Min
Opegan
Healon
Opegan
Healon
Preop
2745 ⫾ 215
2555 ⫾ 265
2708 ⫾ 230
2692 ⫾ 306
3 months postop
2658 ⫾ 229
2404 ⫾ 278
2504 ⫾ 361
2302 ⫾ 409
3.2 ⫾ 4.1
5.9 ⫾ 5.3
7.5 ⫾ 10.6
14.8 ⫾ 9.0
Mean corneal endothelial cell density (per mm2)
Mean rate of endothelial cell loss 3 months postop (%) P value*
.0093
.0001
Means ⫾ SD *Mann-Whitney U test
endothelial cell loss 3 months after surgery was 7.5% ⫾ 10.6% in the Opegan group and 14.8% ⫾ 9.0% in the Healon group (P ⫽ .0001).
Discussion Based on their physical properties, OVDs can be divided into 2 groups: higher viscosity cohesive and lower viscosity dispersive.3 Commercially available sodium hyaluronate 1.0% to 1.6% is cohesive and sodium hyaluronate–chondroitin sulfate is dispersive. Cohesive agents are good at maintaining space, while dispersive agents are retained better in the anterior chamber. However, because of their low cohesiveness, dispersive agents can remain in the anterior chamber even after meticulous irrigation and aspiration, elevating IOP.1,2,4,5 The molecular structure of sodium hyaluronate 1% depends on its molecular weight.6 The molecules are apart from one another when the molecular weight is less than 0.35 million d and form a weak meshwork structure when the molecular weight is between 0.35 d and 1 million d. The meshwork structure becomes stronger as the molecular weight increases to between 1.0 million d and 1.6 million d and reaches a plateau dynamically when the molecular weight is over 1.6 million d. Because the molecular weight of Healon is 4 million d and the meshwork structure between molecules is very strong, Healon can be easily aspirated in a lump from the anterior chamber during phacoemulsification. In contrast, Opegan remains more adherent to the corneal endothelium during phacoemulsification because of its weaker meshwork structure. This is prob-
ably the reason for the smaller cell loss rate in the Opegan group than in the Healon group regardless of the amount of ultrasound energy used during phacoemulsification. Previous studies report that the cell loss rate after phacoemulsification with IOL implantation is greater in eyes with a hard nucleus than in those with a soft nucleus.7,8 Similarly, we found the cell loss rate was greater in cases in which more ultrasound energy was used. It seems reasonable that Opegan reduced cell loss in cases with a large amount of ultrasound energy as the Opegan remained adherent to corneal endothelium, protecting it from fragments of hard nucleus. However, our results indicate that Opegan also reduces cell loss in cases in which less ultrasound energy is used. Opegan probably protected the corneal endothelium not only from fragments of hard nucleus but also from the irrigation solution or the air bubbles that form during phacoemulsification. Common complications of the use of viscoelastic agents include elevated IOP,9,10 which occurs when OVDs are not completely removed intraoperatively and obstruct the trabecular outflow pathway. Dispersive OVDs are not easily aspirated from the anterior chamber because of their low cohesiveness1,2,4,5 and can contribute to a rise in IOP. In our series, an IOP rise was not observed in the Opegan or Healon group 1 day after the surgery, suggesting both OVDs were removed by I/A. Further studies are necessary to confirm the lack of IOP spikes during the first 24 hours after surgery. In conclusion, Opegan was more effective than Healon in protecting corneal endothelial cells during
J CATARACT REFRACT SURG—VOL 28, SEPTEMBER 2002
1559
CORNEAL ENDOTHELIAL CELL PROTECTION DURING PHACOEMULSIFICATION
phacoemulsification regardless of the amount of ultrasound energy used.
7.
References 1. Poyer JF, Chan KY, Arshinoff SA. Quantitative method to determine the cohesion of viscoelastic agents by dynamic aspiration. J Cataract Refract Surg 1998; 24: 1130 –1135 2. McDermott ML, Hazlett LD, Barrett RP, Lambert RJ. Viscoelastic adherence to corneal endothelium following phacoemulsification. J Cataract Refract Surg 1998; 24: 678 –683 3. Arshinoff SA. Dispersive-cohesive viscoelastic soft shell technique. J Cataract Refract Surg 1999; 25:167–173 4. Assia EI, Apple DJ, Lim ES, et al. Removal of viscoelastic materials after experimental cataract surgery in vitro. J Cataract Refract Surg 1992; 18:3–6 5. Fry LL. Postoperative intraocular pressure rises: a comparison of Healon, Amvisc, and Viscoat. J Cataract Refract Surg 1989; 15:415–420 6. Yanaki T, Yamaguchi T. Temporary network formation of hyaluronate under a physiological condition. 1. Mo-
1560
8.
9.
10.
lecular-weight dependence. Biopolymers 1990; 30:415– 425 Hayashi K, Hayashi H, Nakao F, Hayashi F. Risk factors for corneal endothelial injury during phacoemulsification. J Cataract Refract Surg 1996; 22:1079 –1084 Vajpayee RB, Bansal A, Sharma N, et al. Phacoemulsification of white hypermature cataract. J Cataract Refract Surg 1999; 25:1157–1160 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 Rainer G, Menapace R, Findl O, et al. Intraocular pressure after small incision cataract surgery with Healon5 and Viscoat. J Cataract Refract Surg 2000; 26:271–276
From the Meiwakai Medical Foundation, Miyata Eye Hospital, Miyakonojo, Miyazaki (Miyata, Maruoka, Nakahara, Otani, Nejima, Samejima), and Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo (Amano), Japan. None of the authors has a financial or proprietary interest in any material or method mentioned.
J CATARACT REFRACT SURG—VOL 28, SEPTEMBER 2002
Purpose: To compare the efficacy of low- and high-molecular-weight sodium hyaluronate in protecting corneal endothelial cells during phacoemulsification. Setting: Miyata Eye Hospital, Miyakonojo, Miyazaki, Japan. Methods: One hundred forty-nine eyes of 136 cataract patients were randomly assigned to have cataract surgery using sodium hyaluronate 1% with a low molecular weight (0.6 to 1.2 million d, Opegan姞) or sodium hyaluronate 1% with a high molecular weight (4 million d, Healon姞) during phacoemulsification. Each group was divided into 2 subgroups depending on the amount of ultrasound (% min) used during phacoemulsification, which was defined as the mean phacoemulsification energy (%) multiplied by phacoemulsification time (minutes). Corneal endothelial cell density was examined preoperatively and 3 months after surgery. The rate of cell loss was compared between the subgroups in the Opegan group and the Healon group. Results: In the subgroups with ultrasound of 50% min or less, the mean rate of endothelial cell loss 3 months after surgery was 3.2% ⫾ 4.1% (SD) in the Opegan group and 5.9% ⫾ 5.3% in the Healon group (P ⫽ .0214). In the subgroups with ultrasound over 50% min, the mean rate of endothelial cell loss 3 months after surgery was 7.5% ⫾ 10.6% in the Opegan group and 14.8 ⫾ 9.0% in the Healon group (P ⫽ .0029). Conclusions: The results suggest that Opegan is more effective than Healon in protecting corneal endothelial cells during phacoemulsification regardless of the amount of ultrasound energy used. J Cataract Refract Surg 2002; 28:1557–1560 © 2002 ASCRS and ESCRS
O
phthalmic viscosurgical devices (OVDs) play a crucial role in cataract surgery today by protecting corneal endothelial cells and maintaining space in the capsular bag or anterior chamber. Among various commercially available OVDs, sodium hyaluronate–chondroitin sulfate has been shown to be the most effective in remaining adherent to and protecting the corneal endothelium during phacoemulsification.1–3 However, this Accepted for publication May 1, 2002. Reprint requests to Shiro Amano, MD, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655 Japan. E-mail: [email protected]. © 2002 ASCRS and ESCRS Published by Elsevier Science Inc.
OVD can remain in the anterior chamber even after meticulous irrigation/aspiration (I/A) because of its low cohesiveness and can elevate intraocular pressure (IOP).1,2,4,5 Because sodium hyaluronate with a low molecular weight has characteristics between sodium hyaluronate with a high molecular weight and sodium hyaluronate–chondroitin sulfate, it can protect the corneal endothelium during phacoemulsification and can be removed at the end of surgery more easily than sodium hyaluronate–chondroitin sulfate. In this study, we compared the efficacy of lowand high-molecular-weight sodium hyaluronate 1% 0886-3350/02/$–see front matter PII S0886-3350(02)01540-7
CORNEAL ENDOTHELIAL CELL PROTECTION DURING PHACOEMULSIFICATION
in protecting corneal endothelial cells during phacoemulsification.
Patients and Methods This study comprised 146 eyes of 133 cataract patients who had phacoemulsification and posterior chamber intraocular lens (IOL) implantation at Miyata Eye Hospital from August 1995 through July 1996. No patient had systemic or ocular complications preoperatively. The patients were randomly assigned to have cataract surgery using sodium hyaluronate 1% with a low molecular weight (0.6 to 1.2 million d, Opegan威) or sodium hyaluronate 1% with a high molecular weight (4 million d, Healon威) during phacoemulsification. All patients were operated on by the same surgeon (K.M.), who had had similar experience with both OVDs. After topical anesthesia of lidocaine hydrochloride 4% (Xylocaine威) was administered, a superior 4.1 mm corneoscleral incision was made. About 0.1 mL of Opegan or Healon was injected into the anterior chamber. A capsulorhexis was created and hydrodissection performed. For phacoemulsification, the divide-and-conquer technique was used and the lens cortex was suctioned with I/A. The vacuum pressure and the aspiration rate during phacoemulsification were 80 mm Hg and 17 mL/min, respectively, before the lens nucleus was divided and 350 mm Hg and 20 mL/min, respectively, after the lens nucleus was divided. In both groups, Healon was injected into the capsular bag and anterior chamber and an AcrySof威 foldable acrylic IOL (MA60, Alcon) was implanted in the capsular bag. The OVDs were completely aspirated from the capsular bag and anterior chamber with an I/A tip. No eye received IOP-lowering medication. The amount of ultrasound (% min) was defined as the mean phacoemulsification energy (%) multiplied by phacoemulsification time (minutes). Each group was divided into 2 subgroups based on whether the amount of ultrasound (% min) was over 50% min or under 50% min. The IOP was measured with a noncontact tonometer (Xpert Plus, Tomey) preoperatively and 1 day and 1 week after surgery. Endothelial
Table 1.
cell micrographs were obtained with a specular microscope (Konan Robo-CA, Konan). More than 100 cells were analyzed per eye using a cell analysis system (Fully Automatic Non Contact Cell Analyzer, Konan). The examiner who did the endothelial cell count and preoperative and postoperative follow-ups was masked as to which group the eye belonged. The Mann-Whitney U test and unpaired t test were used to compare intraoperative and postoperative parameters between the subgroups. A P value less than 0.05 was considered significant.
Results The patients’ characteristics and the intraoperative parameters in each group are shown in Table 1. In the Opegan group, the amount of ultrasound was 50% min or less in 41 eyes and over 50% min in 50 eyes. In the Healon group, the amount of ultrasound was 50% min or less in 27 eyes and over 50% min in 28 eyes. There was no statistically significant difference in any parameter between the corresponding subgroups (Table 1). The mean IOP in the Opegan group was 11.2 mm Hg ⫾ 3.5 (SD) (range 4 to 18 mm Hg) preoperatively, 10.5 ⫾ 4.2 mm Hg (range 4 to 19 mm Hg) 1 day after surgery, and 10.2 ⫾ 3.5 mm Hg (range 3 to 17 mm Hg) at 1 week. The mean IOP in the Healon group was 10.9 mm Hg ⫾ 2.8 (range 6 to 20 mm Hg), 11.2 ⫾ 3.0 mm Hg (range 5 to 18 mm Hg), and 9.4 ⫾ 2.3 mm Hg (range 5 to 15 mm Hg), respectively. No eye developed IOP greater than 21 mm Hg. In the groups in which the amount of ultrasound was 50% min or less, the mean rate of endothelial cell loss 3 months after surgery was 3.2% ⫾ 4.1% in the Opegan group and 5.9% ⫾ 5.3% in the Healon group (P ⫽ .0093) (Table 2). In the groups in which the amount of ultrasound was over 50% min, the rate of
Preoperative characteristics and intraoperative parameters. Ultrasound 50% Min or Less
Parameter Number of eyes
Opegan
Healon
41
27
Ultrasound Over 50% Min
P Value*
Opegan
Healon
50
28
P Value*
Mean age (y)
69.8 ⫾ 9.7
74.6 ⫾ 6.4
.12
75.6 ⫾ 8.0
74.3 ⫾ 8.7
.72
Mean irrigation solution used (mL)
57.3 ⫾ 16.9
55.5 ⫾ 14.5
.66
76.8 ⫾ 29.9
86.4 ⫾ 32.9
.13
7.3 ⫾ 1.1
7.5 ⫾ 1.0
.48
11.0 ⫾ 4.1
10.2 ⫾ 2.3
.39
Mean surgical time (min) Means ⫾ SD *Unpaired t test
1558
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CORNEAL ENDOTHELIAL CELL PROTECTION DURING PHACOEMULSIFICATION
Table 2.
Corneal endothelial cell density and cell loss rate. Ultrasound 50% Min or Less
Parameter
Ultrasound Over 50% Min
Opegan
Healon
Opegan
Healon
Preop
2745 ⫾ 215
2555 ⫾ 265
2708 ⫾ 230
2692 ⫾ 306
3 months postop
2658 ⫾ 229
2404 ⫾ 278
2504 ⫾ 361
2302 ⫾ 409
3.2 ⫾ 4.1
5.9 ⫾ 5.3
7.5 ⫾ 10.6
14.8 ⫾ 9.0
Mean corneal endothelial cell density (per mm2)
Mean rate of endothelial cell loss 3 months postop (%) P value*
.0093
.0001
Means ⫾ SD *Mann-Whitney U test
endothelial cell loss 3 months after surgery was 7.5% ⫾ 10.6% in the Opegan group and 14.8% ⫾ 9.0% in the Healon group (P ⫽ .0001).
Discussion Based on their physical properties, OVDs can be divided into 2 groups: higher viscosity cohesive and lower viscosity dispersive.3 Commercially available sodium hyaluronate 1.0% to 1.6% is cohesive and sodium hyaluronate–chondroitin sulfate is dispersive. Cohesive agents are good at maintaining space, while dispersive agents are retained better in the anterior chamber. However, because of their low cohesiveness, dispersive agents can remain in the anterior chamber even after meticulous irrigation and aspiration, elevating IOP.1,2,4,5 The molecular structure of sodium hyaluronate 1% depends on its molecular weight.6 The molecules are apart from one another when the molecular weight is less than 0.35 million d and form a weak meshwork structure when the molecular weight is between 0.35 d and 1 million d. The meshwork structure becomes stronger as the molecular weight increases to between 1.0 million d and 1.6 million d and reaches a plateau dynamically when the molecular weight is over 1.6 million d. Because the molecular weight of Healon is 4 million d and the meshwork structure between molecules is very strong, Healon can be easily aspirated in a lump from the anterior chamber during phacoemulsification. In contrast, Opegan remains more adherent to the corneal endothelium during phacoemulsification because of its weaker meshwork structure. This is prob-
ably the reason for the smaller cell loss rate in the Opegan group than in the Healon group regardless of the amount of ultrasound energy used during phacoemulsification. Previous studies report that the cell loss rate after phacoemulsification with IOL implantation is greater in eyes with a hard nucleus than in those with a soft nucleus.7,8 Similarly, we found the cell loss rate was greater in cases in which more ultrasound energy was used. It seems reasonable that Opegan reduced cell loss in cases with a large amount of ultrasound energy as the Opegan remained adherent to corneal endothelium, protecting it from fragments of hard nucleus. However, our results indicate that Opegan also reduces cell loss in cases in which less ultrasound energy is used. Opegan probably protected the corneal endothelium not only from fragments of hard nucleus but also from the irrigation solution or the air bubbles that form during phacoemulsification. Common complications of the use of viscoelastic agents include elevated IOP,9,10 which occurs when OVDs are not completely removed intraoperatively and obstruct the trabecular outflow pathway. Dispersive OVDs are not easily aspirated from the anterior chamber because of their low cohesiveness1,2,4,5 and can contribute to a rise in IOP. In our series, an IOP rise was not observed in the Opegan or Healon group 1 day after the surgery, suggesting both OVDs were removed by I/A. Further studies are necessary to confirm the lack of IOP spikes during the first 24 hours after surgery. In conclusion, Opegan was more effective than Healon in protecting corneal endothelial cells during
J CATARACT REFRACT SURG—VOL 28, SEPTEMBER 2002
1559
CORNEAL ENDOTHELIAL CELL PROTECTION DURING PHACOEMULSIFICATION
phacoemulsification regardless of the amount of ultrasound energy used.
7.
References 1. Poyer JF, Chan KY, Arshinoff SA. Quantitative method to determine the cohesion of viscoelastic agents by dynamic aspiration. J Cataract Refract Surg 1998; 24: 1130 –1135 2. McDermott ML, Hazlett LD, Barrett RP, Lambert RJ. Viscoelastic adherence to corneal endothelium following phacoemulsification. J Cataract Refract Surg 1998; 24: 678 –683 3. Arshinoff SA. Dispersive-cohesive viscoelastic soft shell technique. J Cataract Refract Surg 1999; 25:167–173 4. Assia EI, Apple DJ, Lim ES, et al. Removal of viscoelastic materials after experimental cataract surgery in vitro. J Cataract Refract Surg 1992; 18:3–6 5. Fry LL. Postoperative intraocular pressure rises: a comparison of Healon, Amvisc, and Viscoat. J Cataract Refract Surg 1989; 15:415–420 6. Yanaki T, Yamaguchi T. Temporary network formation of hyaluronate under a physiological condition. 1. Mo-
1560
8.
9.
10.
lecular-weight dependence. Biopolymers 1990; 30:415– 425 Hayashi K, Hayashi H, Nakao F, Hayashi F. Risk factors for corneal endothelial injury during phacoemulsification. J Cataract Refract Surg 1996; 22:1079 –1084 Vajpayee RB, Bansal A, Sharma N, et al. Phacoemulsification of white hypermature cataract. J Cataract Refract Surg 1999; 25:1157–1160 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 Rainer G, Menapace R, Findl O, et al. Intraocular pressure after small incision cataract surgery with Healon5 and Viscoat. J Cataract Refract Surg 2000; 26:271–276
From the Meiwakai Medical Foundation, Miyata Eye Hospital, Miyakonojo, Miyazaki (Miyata, Maruoka, Nakahara, Otani, Nejima, Samejima), and Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo (Amano), Japan. None of the authors has a financial or proprietary interest in any material or method mentioned.
J CATARACT REFRACT SURG—VOL 28, SEPTEMBER 2002