2% hydroxypropyl methylcellulose as a viscous surgical adjunct A multicenter prospective randomized trial S. Gregory Smith, M.D., Richard L. Lindstrom, M.D.
B TR
T
multicent r pro pecti
Ke
Word
rn al ndoth lium , xtra 'ap lIlar atara·t xtra tion , intra ·ttlar pr . Ul" , pha 'o mul ificati n , p t haml I" I n implantati n , odium h)aluronat • '{ u1m' mi ro ' op • 2~ hydroxypropyl 111 thyl lIulo '
Methylcellulose has long been in use in ophthalmology, particularly in topical medications. l Methylcellulose is a naturally occurring nontoxic carbohydrate that has many chemical derivatives including methylcellulose, hydroxypropyl methylcellulose, hydroxybutyl methylcellulose, carboxypropyl methylcellulose, and hydroxypropyl cellulose. In 1983 Fechner and Fechner2 reported on the use of hydroxy propyl methylcellulose in cataract and intraocular lens (IOL) surgery and concluded that it appeared safe and effective for this use. Smith et al. 3 found that 2% hydroxypropyl methylcellulose was more effective than balanced salt solution in extracapsular cataract extraction (ECCE) and posterior chamber lens insertion in cats in a prospectively controlled study. Aron-Rosa and coauthors 4 found that methylcellulose was more effective than air in protecting the corneal endothelium in human subjects. The purpose of our study was to determine
whether 2% hydroxypropyl methylcellulose protected the corneal endothelium safely and effectively and facilitated cataract/implant surgery in humans by comparing it to 1% sodium hyaluronate.
MATERIALS AND METHODS The form of methylcellulose used in this study was
2% hydroxypropyl methylcellulose (HPMC) in bal-
anced salt solution manufactured by Storz Ophthalmics (Occucoat®). It has a viscosity of 4,000 centistokes and a molecular weight of 90,000 daltons. The study design was a prospective multicenter clinical trial in which eight surgeons participated. Two hundred six patients had ECCE or phacoemulsification with posterior chamber IOL implantation; 11 had secondary IOLs; 3 had phacoemulsification or ECCE with anterior chamber lens insertion.
Supported in part by Storz Instrument Company and an unrestricted grant from Research to Prevent Blindness, Presented in part at the First Annual Symposium on Viscoelastic Substances, Northern Eye Institute, Manchester, England, July 1985, and at the European Intraocular Implant Lens Council, 6th Annual Meeting, Copenhagen, Denmark, August 1988. The authors have no commercial or proprietary interest in the products discussed and will not receive any remuneration resultingfrom their use, S, Gregory Smith, M. D., currently serves as a paid consultant to Storz Ophthalmics. Richard L. Lindstrom, M. D., served as medical monitor for the study presented. Reprint requests to S. Gregory Smith, M.D., 1700 Shallcross Avenue, Suite 2, Wilmington, Delaware 19806.
J CATARACT REFRACT SURG-VOL
17, NOVEMBER 1991
839
Patients were assigned the use of 2% hydroxypropyl methylcellulose (Occucoat) or 1% sodium hyaluronate (Healon®) by prospective random number generation; 166 eyes received Occucoat and 56 received Healon-a 3:1 ratio. Patients were excluded from the study if they had glaucoma, corneal guttata, history of iritis, or a preoperative endothelial cell count that could not be accurate Iv read. All patients had specular microscopy preope;atively and again at three months after surgery. Each center used a CooperVision video unit or Keeler Konan specular microscopy control. The independent observer eliminated any patient with unreadable photographs or a small sample size. Clinical examination and intraocular pressure (lOP) were evaluated preoperatively, as well as one day, one week, and three months postoperatively. The study was not truly masked because the surgeons were able to identify the viscous agent at the time of surgery by its behavior and packaging. All specular microscopy photographs were evaluated by one independent observer who was masked as to the patient's identity and what type of viscous agent was used intraoperatively. Surgeons completed a form for each visit, one day, one week, and three months postoperatively. If a patient missed a 24-hour visit but was seen at 48 hours, the specular microscopy results were not included in the 24-hour visit, but the results at the one week and three month visits were included in the tabulation. The surgeons evaluated whether the substance subjectively facilitated surgery intraoperatively. The presence of corneal edema, uveitis, synechial formation, lOP increase, and other adverse reactions were evaluated during the clinical examinations. The grading systems used are described in Table 1.
RESULTS Intraocular Pressure At 24 hours the average rise of lOP from baseline in the Occucoat group (150 patients) was 9.8%; in the Healon group (47 patients) it was 11.5%. These differences were not statistically significant. At one week the lOP was - 6.0% for the Occucoat group and - 9.4% for the Healon group (P= NS). At three months the pressure had dropped 7.0% on average for the Occucoat group and 5.1% for the Healon group (P= NS). Surgeons handled the viscous material in various ways; some removed it routinely in all cases except when there was iris prolapse while others left it in to see what effect it had on the lOP at 24 hours. The material was removed from 123 patients in the Occucoat group who were not on lOP-reducing medications. The patients had an average lOP 840
J CATARACT REFRACT
Table 1. Grading system for corneal edema and uveitis.
Corneal edema None:
Cornea clear
Mild:
~Iicroedema with accumulation of fluid limited to the stroma
Moderate:
Gross edema with intercellular microcystic accumulation of fluid in the epitheiium
Severe:
Folds in Descemet's membrane, gross edema with stromal il1\'olvement: vertical striae noted
Uceitis None:
Clear
Mild:
Few (1 to 9) cells per high power field
Moderate:
Many (10 to 40) cells per high power field
Severe:
40 or more cells per high power field (hypopyon)
increase of5.5%. The material was removed from 36 patients in the Healon group who were not on IOPreducing medications. The average increase was 3%. The difference was not statistically significant. At one week, the average lOP from the preoperative baseline was - 6.1 % for the Occucoat group and -16.7% for the Healon group. This was statistically significant (P > .05). At three months, the average lOP decrease was 6.1 % for the Occucoat group and 6.0% for the Healon group (P= NS). Patients were not routinely on glaucoma prophylaxis at the end of the surgery and this was left to the surgeon's discretion. In the Occucoat group, 26.5% of patients had an lOP rise of 5 mm Hg or more during the study and 33.3% of the Healon patients had a similar rise. The maximum lOP measured was 40 mm Hg in the Occucoat group at 24 hours and 41 mm Hg in the Healon group at 24 hours.
Cornea The clinical evaluations of corneal status are reported in Table 2. There was a gradual resolution of all corneal edema in both groups and from the data available at three months all corneas were free of edema. No statistically or clinically significant differences between the two groups were noted. Specular microscopy was performed at the three month postoperative visit. The Occucoat group (109 patients) had an average cell loss of 12.0%. The Healon group (36 patients) had an average cell loss of 9.8%. These differences were not statistically significant. One hundred thirty three of the 145 patients who had specular microscopy performed at three months
SURG-VOL 17, NOVEMBER 1991
Table 2. Corneal edema. Postoperative Interval 1 day 1 week 3 months
Viscoelastic Material
None
Mild
Moderate
Severe
HPMC
34.3%
41.6%
10.2%
9.0%
4.8%
Healon
30.4%
51.8%
7.1%
3.6%
7.1%
HPMC
82.5%
13.3%
2.4%
1.8%
0
Healon
69.5%
19.6%
1.8%
8.9%
0
N/A
HPMC
94.6%
0
0
0
5.4%
Healon
91.1%
0
0
0
8.9%
had ECCE and 12 patients had phacoemulsification. The average cell loss of the 99 ECCE patients who received Occucoat (average age 71.7 years) was 11.8%. The average cell loss of the 34 ECCE patients who received Healon (average age 67.3 years) was 9.3%. This was not statistically significantlv different. In'the ten patients who had phacoemulsification with Occucoat (average age 65.3 years), the average mean cell loss was 14.5%; in the two patients who had phacoemulsification with Healon the mean cell loss was 17.5%. While endothelial cell loss was slightly higher in the phacoemulsification group, these differences were not statistically significant and no conclusions can be reached. The uveitis improved over time. The available data, at three months, show that in 92.8% of the Occucoat patients and in 91.1% of the Healon patients the postoperative uveitis had resolved completely (Table 3). No statistically significant difference was noted at any time interval. Postoperative complications are listed in Table 4. No significant differences were noted.
protect the corneal endothelium. The average cell loss in the Occucoat group was 12.1 %; in the Healon group it was 10.0%. In analyzing only ECCE with posterior chamber implantation, the average cell loss was 12.2% in Occucoat patients and 9.9% in Healon patients. These results reveal no statistical or clinically significant differences. The lOP in patients who had the viscoelastic material removed and who were not on lOP-reducing drugs increased in the early postoperative period and decreased an average of 6% at three months in both groups. There were no statistically significant differences, except at one week in the Healon group as opposed to the Occucoat group. No conclusions can be drawn about pressure elevations that occurred prior to 24 hours. The results of substudies evaluating early (two to six hours) postoperative lOP rises will be the subject of another paper. The incidence of uveitis was similar in each group, with no severe reactions reported for Occucoat and one severe uveitis reported for Healon. As would be expected, there was a gradual improvement in the amount ofiritis throughout the postoperative course, with near complete resolution at three months. Complications are usually associated with surgery and there were no serious complications that could be attributed to either viscoelastic. The incidence of cystoid macular edema (CME)
DISCUSSION In this study of ECCE or phacoemulsification with posterior chamber lens implantation and secondary lens implantation, Occucoat was found to
Table 3. Uveitis. Postoperative Interval 1 day 1 week 3 months
Viscoelastic Material
None
Mild
Moderate
Severe
N/A
HPMC
33.7%
46.4%
14.5%
0
5.4%
Healon
32.1%
50.0%
10.7%
0
7.1%
HPMC
58.4%
37.3%
3.0%
0
1.2%
Healon
60.7%
35.7%
1.8%
1.8%
o
HPMC
92.8%
1.8%
0
0
5.4%
Healon
91.1%
0
0
0
8.9%
J CATARACT
REFRACT SURG-VOL 17, NOVEMBER 1991
841
Table 4. Postoperative complications.
The surgeons felt that Occucoat facilitated surgery in all but one case. This study agrees with the earlier reports of Fechner and Fechner,2 Aron-Rosa and coauthors,4 and Leisegang and coauthors.8 Occucoat effectively protected the corneal endothelium and facilitated surgery in ECCE and posterior chamber lens insertion.
Number of Patients (%) Postoperative Complication
Occucoat
Healon
Vitreous to the wound
1 (0.6%)
0
Detached Descemet's membrane
0
1 (1.8%)
Synechias to IOL
1 (0 .6%)
0
Hyphema
6 (3.8%)
5 9( .6%)
Precipitates on IOL
1 0( .6%)
1 1.8%) (
Retinal detachment
1 (0 .6%)
0
Vitrectomy
4 (2.3%)
0
Capsulotomy CME
46 (26.4%) 3 (1.9%)
REFERENCES
12 (20.7%) 0
was 1.9% in the Occucoat group and 0 in the Healon group. However, four patients in the Occucoat group had vitrectomy and one had vitreous to the wound, whereas no patients in the Healon group had this procedure or complication. Alarge percentage of both groups had opening of the posterior capsule, which has been shown to be a risk factor for CME.5-7 The study was not designed to evaluate strictly for CME so there are a number of uncontrolled factors that prevent comparison. Occucoat was reported to maintain the anterior chamber in 99.4% of cases (not reported in 0.6% of cases). Healon was reported to maintain the anterior chamber in 80.4% of cases (not reported in 19.6%).
842
J CATARACT REFRACT
1. Fleming TC , Merrill DL, Girard LJ. Studies of the irritating action of methylcellulose . Arch Ophthalmol 1959; 61: 565-567 2. Fechner PU, Fechner MU. Methylcellulose and lens implantation. Br J Ophthalmol 1983; 67:259-263 3. Smith SG, Lindstrom RL, Miller RA, et al. Safety and efficacy of 2% hydroxypropyl methylcellulose in cat and monkey cataract-implant surgery. Am Intra-Ocular Implant Soc J 1984; 10:160-163 4. Aron-Rosa D, Cohn HC, Aron J-J, Bouquety C . Methylcellulose instead of Healon® in extracapsular surgery with intraocular lens implantation . Ophthalmology 1983; 1235-1238 5. Charles S. IOL as a barrier in vitreoretinal disease-remove it or leave it? Cataract 1985; 2(7):24-26 6. Winslow RL, Taylor BC, Harris WS. A one-year follow-up of cystoid macular edema following intraocular lens implantation. Ophthalmology 1978; 85:190-196 7. Percival P. Clinical factors relating to cystoid macular edema after lens implantation. Am Intra-Ocular Implant Soc J 1981; 7:43-45 8. LiesegangTJ, Bourne WM, Ilstrup DM. The use of hydroxypropyl methylcellulose in extracapsular cataract extraction with intraocular lens implantation. Am J Ophthalmol 1986; 102:723-726
SURG-VOL 17, NOVEMBER 1991
B TR
T
multicent r pro pecti
Ke
Word
rn al ndoth lium , xtra 'ap lIlar atara·t xtra tion , intra ·ttlar pr . Ul" , pha 'o mul ificati n , p t haml I" I n implantati n , odium h)aluronat • '{ u1m' mi ro ' op • 2~ hydroxypropyl 111 thyl lIulo '
Methylcellulose has long been in use in ophthalmology, particularly in topical medications. l Methylcellulose is a naturally occurring nontoxic carbohydrate that has many chemical derivatives including methylcellulose, hydroxypropyl methylcellulose, hydroxybutyl methylcellulose, carboxypropyl methylcellulose, and hydroxypropyl cellulose. In 1983 Fechner and Fechner2 reported on the use of hydroxy propyl methylcellulose in cataract and intraocular lens (IOL) surgery and concluded that it appeared safe and effective for this use. Smith et al. 3 found that 2% hydroxypropyl methylcellulose was more effective than balanced salt solution in extracapsular cataract extraction (ECCE) and posterior chamber lens insertion in cats in a prospectively controlled study. Aron-Rosa and coauthors 4 found that methylcellulose was more effective than air in protecting the corneal endothelium in human subjects. The purpose of our study was to determine
whether 2% hydroxypropyl methylcellulose protected the corneal endothelium safely and effectively and facilitated cataract/implant surgery in humans by comparing it to 1% sodium hyaluronate.
MATERIALS AND METHODS The form of methylcellulose used in this study was
2% hydroxypropyl methylcellulose (HPMC) in bal-
anced salt solution manufactured by Storz Ophthalmics (Occucoat®). It has a viscosity of 4,000 centistokes and a molecular weight of 90,000 daltons. The study design was a prospective multicenter clinical trial in which eight surgeons participated. Two hundred six patients had ECCE or phacoemulsification with posterior chamber IOL implantation; 11 had secondary IOLs; 3 had phacoemulsification or ECCE with anterior chamber lens insertion.
Supported in part by Storz Instrument Company and an unrestricted grant from Research to Prevent Blindness, Presented in part at the First Annual Symposium on Viscoelastic Substances, Northern Eye Institute, Manchester, England, July 1985, and at the European Intraocular Implant Lens Council, 6th Annual Meeting, Copenhagen, Denmark, August 1988. The authors have no commercial or proprietary interest in the products discussed and will not receive any remuneration resultingfrom their use, S, Gregory Smith, M. D., currently serves as a paid consultant to Storz Ophthalmics. Richard L. Lindstrom, M. D., served as medical monitor for the study presented. Reprint requests to S. Gregory Smith, M.D., 1700 Shallcross Avenue, Suite 2, Wilmington, Delaware 19806.
J CATARACT REFRACT SURG-VOL
17, NOVEMBER 1991
839
Patients were assigned the use of 2% hydroxypropyl methylcellulose (Occucoat) or 1% sodium hyaluronate (Healon®) by prospective random number generation; 166 eyes received Occucoat and 56 received Healon-a 3:1 ratio. Patients were excluded from the study if they had glaucoma, corneal guttata, history of iritis, or a preoperative endothelial cell count that could not be accurate Iv read. All patients had specular microscopy preope;atively and again at three months after surgery. Each center used a CooperVision video unit or Keeler Konan specular microscopy control. The independent observer eliminated any patient with unreadable photographs or a small sample size. Clinical examination and intraocular pressure (lOP) were evaluated preoperatively, as well as one day, one week, and three months postoperatively. The study was not truly masked because the surgeons were able to identify the viscous agent at the time of surgery by its behavior and packaging. All specular microscopy photographs were evaluated by one independent observer who was masked as to the patient's identity and what type of viscous agent was used intraoperatively. Surgeons completed a form for each visit, one day, one week, and three months postoperatively. If a patient missed a 24-hour visit but was seen at 48 hours, the specular microscopy results were not included in the 24-hour visit, but the results at the one week and three month visits were included in the tabulation. The surgeons evaluated whether the substance subjectively facilitated surgery intraoperatively. The presence of corneal edema, uveitis, synechial formation, lOP increase, and other adverse reactions were evaluated during the clinical examinations. The grading systems used are described in Table 1.
RESULTS Intraocular Pressure At 24 hours the average rise of lOP from baseline in the Occucoat group (150 patients) was 9.8%; in the Healon group (47 patients) it was 11.5%. These differences were not statistically significant. At one week the lOP was - 6.0% for the Occucoat group and - 9.4% for the Healon group (P= NS). At three months the pressure had dropped 7.0% on average for the Occucoat group and 5.1% for the Healon group (P= NS). Surgeons handled the viscous material in various ways; some removed it routinely in all cases except when there was iris prolapse while others left it in to see what effect it had on the lOP at 24 hours. The material was removed from 123 patients in the Occucoat group who were not on lOP-reducing medications. The patients had an average lOP 840
J CATARACT REFRACT
Table 1. Grading system for corneal edema and uveitis.
Corneal edema None:
Cornea clear
Mild:
~Iicroedema with accumulation of fluid limited to the stroma
Moderate:
Gross edema with intercellular microcystic accumulation of fluid in the epitheiium
Severe:
Folds in Descemet's membrane, gross edema with stromal il1\'olvement: vertical striae noted
Uceitis None:
Clear
Mild:
Few (1 to 9) cells per high power field
Moderate:
Many (10 to 40) cells per high power field
Severe:
40 or more cells per high power field (hypopyon)
increase of5.5%. The material was removed from 36 patients in the Healon group who were not on IOPreducing medications. The average increase was 3%. The difference was not statistically significant. At one week, the average lOP from the preoperative baseline was - 6.1 % for the Occucoat group and -16.7% for the Healon group. This was statistically significant (P > .05). At three months, the average lOP decrease was 6.1 % for the Occucoat group and 6.0% for the Healon group (P= NS). Patients were not routinely on glaucoma prophylaxis at the end of the surgery and this was left to the surgeon's discretion. In the Occucoat group, 26.5% of patients had an lOP rise of 5 mm Hg or more during the study and 33.3% of the Healon patients had a similar rise. The maximum lOP measured was 40 mm Hg in the Occucoat group at 24 hours and 41 mm Hg in the Healon group at 24 hours.
Cornea The clinical evaluations of corneal status are reported in Table 2. There was a gradual resolution of all corneal edema in both groups and from the data available at three months all corneas were free of edema. No statistically or clinically significant differences between the two groups were noted. Specular microscopy was performed at the three month postoperative visit. The Occucoat group (109 patients) had an average cell loss of 12.0%. The Healon group (36 patients) had an average cell loss of 9.8%. These differences were not statistically significant. One hundred thirty three of the 145 patients who had specular microscopy performed at three months
SURG-VOL 17, NOVEMBER 1991
Table 2. Corneal edema. Postoperative Interval 1 day 1 week 3 months
Viscoelastic Material
None
Mild
Moderate
Severe
HPMC
34.3%
41.6%
10.2%
9.0%
4.8%
Healon
30.4%
51.8%
7.1%
3.6%
7.1%
HPMC
82.5%
13.3%
2.4%
1.8%
0
Healon
69.5%
19.6%
1.8%
8.9%
0
N/A
HPMC
94.6%
0
0
0
5.4%
Healon
91.1%
0
0
0
8.9%
had ECCE and 12 patients had phacoemulsification. The average cell loss of the 99 ECCE patients who received Occucoat (average age 71.7 years) was 11.8%. The average cell loss of the 34 ECCE patients who received Healon (average age 67.3 years) was 9.3%. This was not statistically significantlv different. In'the ten patients who had phacoemulsification with Occucoat (average age 65.3 years), the average mean cell loss was 14.5%; in the two patients who had phacoemulsification with Healon the mean cell loss was 17.5%. While endothelial cell loss was slightly higher in the phacoemulsification group, these differences were not statistically significant and no conclusions can be reached. The uveitis improved over time. The available data, at three months, show that in 92.8% of the Occucoat patients and in 91.1% of the Healon patients the postoperative uveitis had resolved completely (Table 3). No statistically significant difference was noted at any time interval. Postoperative complications are listed in Table 4. No significant differences were noted.
protect the corneal endothelium. The average cell loss in the Occucoat group was 12.1 %; in the Healon group it was 10.0%. In analyzing only ECCE with posterior chamber implantation, the average cell loss was 12.2% in Occucoat patients and 9.9% in Healon patients. These results reveal no statistical or clinically significant differences. The lOP in patients who had the viscoelastic material removed and who were not on lOP-reducing drugs increased in the early postoperative period and decreased an average of 6% at three months in both groups. There were no statistically significant differences, except at one week in the Healon group as opposed to the Occucoat group. No conclusions can be drawn about pressure elevations that occurred prior to 24 hours. The results of substudies evaluating early (two to six hours) postoperative lOP rises will be the subject of another paper. The incidence of uveitis was similar in each group, with no severe reactions reported for Occucoat and one severe uveitis reported for Healon. As would be expected, there was a gradual improvement in the amount ofiritis throughout the postoperative course, with near complete resolution at three months. Complications are usually associated with surgery and there were no serious complications that could be attributed to either viscoelastic. The incidence of cystoid macular edema (CME)
DISCUSSION In this study of ECCE or phacoemulsification with posterior chamber lens implantation and secondary lens implantation, Occucoat was found to
Table 3. Uveitis. Postoperative Interval 1 day 1 week 3 months
Viscoelastic Material
None
Mild
Moderate
Severe
N/A
HPMC
33.7%
46.4%
14.5%
0
5.4%
Healon
32.1%
50.0%
10.7%
0
7.1%
HPMC
58.4%
37.3%
3.0%
0
1.2%
Healon
60.7%
35.7%
1.8%
1.8%
o
HPMC
92.8%
1.8%
0
0
5.4%
Healon
91.1%
0
0
0
8.9%
J CATARACT
REFRACT SURG-VOL 17, NOVEMBER 1991
841
Table 4. Postoperative complications.
The surgeons felt that Occucoat facilitated surgery in all but one case. This study agrees with the earlier reports of Fechner and Fechner,2 Aron-Rosa and coauthors,4 and Leisegang and coauthors.8 Occucoat effectively protected the corneal endothelium and facilitated surgery in ECCE and posterior chamber lens insertion.
Number of Patients (%) Postoperative Complication
Occucoat
Healon
Vitreous to the wound
1 (0.6%)
0
Detached Descemet's membrane
0
1 (1.8%)
Synechias to IOL
1 (0 .6%)
0
Hyphema
6 (3.8%)
5 9( .6%)
Precipitates on IOL
1 0( .6%)
1 1.8%) (
Retinal detachment
1 (0 .6%)
0
Vitrectomy
4 (2.3%)
0
Capsulotomy CME
46 (26.4%) 3 (1.9%)
REFERENCES
12 (20.7%) 0
was 1.9% in the Occucoat group and 0 in the Healon group. However, four patients in the Occucoat group had vitrectomy and one had vitreous to the wound, whereas no patients in the Healon group had this procedure or complication. Alarge percentage of both groups had opening of the posterior capsule, which has been shown to be a risk factor for CME.5-7 The study was not designed to evaluate strictly for CME so there are a number of uncontrolled factors that prevent comparison. Occucoat was reported to maintain the anterior chamber in 99.4% of cases (not reported in 0.6% of cases). Healon was reported to maintain the anterior chamber in 80.4% of cases (not reported in 19.6%).
842
J CATARACT REFRACT
1. Fleming TC , Merrill DL, Girard LJ. Studies of the irritating action of methylcellulose . Arch Ophthalmol 1959; 61: 565-567 2. Fechner PU, Fechner MU. Methylcellulose and lens implantation. Br J Ophthalmol 1983; 67:259-263 3. Smith SG, Lindstrom RL, Miller RA, et al. Safety and efficacy of 2% hydroxypropyl methylcellulose in cat and monkey cataract-implant surgery. Am Intra-Ocular Implant Soc J 1984; 10:160-163 4. Aron-Rosa D, Cohn HC, Aron J-J, Bouquety C . Methylcellulose instead of Healon® in extracapsular surgery with intraocular lens implantation . Ophthalmology 1983; 1235-1238 5. Charles S. IOL as a barrier in vitreoretinal disease-remove it or leave it? Cataract 1985; 2(7):24-26 6. Winslow RL, Taylor BC, Harris WS. A one-year follow-up of cystoid macular edema following intraocular lens implantation. Ophthalmology 1978; 85:190-196 7. Percival P. Clinical factors relating to cystoid macular edema after lens implantation. Am Intra-Ocular Implant Soc J 1981; 7:43-45 8. LiesegangTJ, Bourne WM, Ilstrup DM. The use of hydroxypropyl methylcellulose in extracapsular cataract extraction with intraocular lens implantation. Am J Ophthalmol 1986; 102:723-726
SURG-VOL 17, NOVEMBER 1991
