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Posterior capsule opacification 5 yearsafter extracapsular cataract extraction
Posterior capsule opacification 5 years after extracapsular cataract extraction Karin Sundelin, MD, Johan Sj6strand, MD, PhD ABSTRACT Purpose: To find out whether there is a "hidden" group of patients with posterior capsule opacification (PCO) 5 years after cataract surgery and to establish the incidence of PCO.
Setting: Department of Ophthalmology, Sahlgrenska University Hospital, Gothenburg, Sweden.
Methods: A random sample (n = 164) was selected among patients who had extracapsular cataract extraction (ECCE) with intraocular lens implantation in 1991 (N = 1672). All surgically treated cases that required neodymium:YAG (Nd.:YAG) laser capsulotomy (n = 37) within the first 5 years after surgery were recorded. Patients still alive 5 years after surgery who had not had Nd:YAG treatment were offered an eye examination to determine whether PCO requiring capsulotomy existed.
Results:Thirty-seven of 110 patients (34%) alive 5 years after surgery had had an Nd:YAG capsulotomy during the first 5 postoperative years. Follow-up was possible in 51 of 73 untreated patients (70%). Clinically significant PCO according to specified criteria was found in 7 cases (14%). Half of them would benefit from treatment; the other half had visual impairment from other eye disease.
Conclusions: The estimated incidence of PCO 5 years after ECCE was 43%..Five years after surgery, there was an untreated group with clinically significant PCO, approximately 9% of the surgically treated population. This hidden group must be considered in, PCO studies, J Cataract Refract Surg 1999; 25:246-250
l xtracapsular cataract extraction (ECCE) with in,traocular lens (IOL) implantation has been performed increasingly since the beginning of the 1980s. The most common complication is posterior capsule opacification (PCO). ~It is generally accepted that PCO formation is a manifestation of proliferation of preequatorial epithelial cells. It consists of formations of Elschnig pearls, multiple layers of proliferated epithelium, and cells showing myofibroblastic differentiation on .the posterior capsule. Contraction of the myofibroblasts produces numerous tiny wrinkles in the posterior
E
Acceptedfbr publication July 15, 1998. Reprint requests to Karin Sundelin, Department of Ophthalmolog~ Sahlgrenska University Hospita~ 413 45 Gothenburg, Sweden. 246
capsule, resulting in visual distortion, z Posterior capsule opacification may be successfully treated with a neodymium:YAG (Nd:YAG) laser capsulotomy, which is preferred to surgical discission. 3 The Nd:YAG capsulotomy, however, has the disadvantages of inconvenience and cost to the patient, cost to society, and several medical complications, of which the most serious are retinal detachment and macular edema.4 It is therefore important to characterize risk factors for the development of PCO that impairs vision and to establish the impact of PCO on vision after cataract surgery. The incidence of PCO has been reported to be from 3% to more than 50%. Most studies in adults with a follow-up of 3 to 5 years report incidences approaching the latter figure. It is difficult to assess
J CATARACT REFRACT SURG---VOL 25, FEBRUARY 1999
PCO 5 YEARS AFTER ECCE
these studies because most are conducted using consecutive patients and therefore have varying follow-ups. In addition, exclusion criteria are not always accounted for. It is sometimes not evident whether follow-up means that patients are re-examined or whether material is collected only from medical records. In the latter case, patients who do not take active measures to schedule a follow-up examination are systematically excluded. Different authors have used varying criteria to classify their cases, and the indications for performing capsulotomies vary. Surgical techniques and materials are disparate. 3'5-13 The number of Nd:YAG laser capsulotomies performed is commonly used to measure the incidence of PCO. 3'5'6'1°'13 To obtain a more precise picture of the impact of PCO after ECCE and IOL implantation, estimation of its incidence in long-term follow-up studies in epidemiologically defined populations is important. In addition to patients treated for PCO, careful examination of untreated patients must be done. We examined a sample of cataract patients 5 years after surgery. The principal purpose of this initial study was to find and evaluate the proportion of "hidden" cases fulfilling our end-point criteria for PCO who may benefit from laser treatment. A secondary aim was to find the incidence of PCO. This information is needed to examine risk factors for PCO development, with the long-term goal of finding ways to prevent or delay it.
Patients and Methods A sample was selected from patients who had ECCE with IOL implantation during 1991 at the Eye Clinic of Sahlgrenska University Hospital. The Eye Clihic performed more than 90% of all cataract operations in a well-defined population of approximately 630,000 inhabitants at that time. In 1991, cataract surgery was done in 1672 patients. Because of seasonal variations in the frequency of surgery, 10% of the annual number of patients had surgery in January. They were considered a representative sample (n = 164). There were no indications of systematic differences between the sample and the total group of cataract surgery patients. Extracapsular cataract extraction with the goal of posterior IOL implantation was carried out in 1991 in a mixed population by 7 surgeons using the same
criteria for surgery. The lenses most commonly used were poly(methyl methacrylate) (PMMA) with polylSropylene (Prolene®) haptics or single-piece PMMA with heparin coating. The most frequent surgical technique was conventional ECCE, but 8 of 118 patients had small incision phacoemulsification and capsulorhexis. These 8 patients were included in the present study but have subsequently been excluded from the analysis. One patient was excluded from the sample because the surgery had been done using aft intracapsular technique. At the time of the study, 5 years after surgery, 45 persons had died (5 had had an Nd:YAG capsulotomy). The mean survival time after cataract surgery was 28.8 months. Thirty-seven patients had been treated with Nd:YAG laser capsulotomy within the 5 years after primary surgery. Left to evaluate were 73 individuals. They were all invited to an examination by 1 surgeon (K.S.) shortly after the 5 years had expired. The examination included measurement of best corrected visual acuity (BCVA) with optimal correction on a Snellen acuity chart, indirect ophthalmoscopy, slitlamp evaluation, and tonometry. Apart from the examination results, the following parameters were recorded: age; sex; type of operation; BCVA after surgery; serious intraoperative complications; comorbidity such as diabetes mellitus, glaucoma, uveitis, or other vision-reducing eye disease; and symptoms such as glare or reduced vision. Nine of the 51 patients examined had diabetes mellitus and 11 glaucoma in the treated eye. None had uveitis. The following definition of clinically significant PCO was used in accordance with the criteria for clinically significant PCO requiring Nd:YAG laser treatment: (1) redtiction in visual acuity by 2 lines compared with BCVA early in the postoperative period; (2) PCO seen against the red reflex by ophthalmoscopy; (3) PCO visible within the central area of the pupil seen at the slitlamp; (4) reports of glare, reduced vision, or both. If the patient had another visionreducing eye disease, all criteria had to be fulfilled except the first one. Patients with clinically significant PCO at the time of the examination were offered an Nd:YAG laser capsulotomy. Laser-treated patients were invited to a postlaser examination performed by a trained nurse. This examination included BCVA and the patient's subjective evaluation of the treatment.
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247
PCO 5 YEARS AFTER ECCE
Table 1.
Baseline patient characteristics at the time of ECCE surgery. ....
~i,~Che~actel;istic:~.
~
'
Number
Men
Women
Age (Years) at Surgery Mean +_ SD
Entire group
163
54
109
78 -+ 10.8
Alive 5 years after surgery
118
37
81
74 -+ 11.1
Dead 5 years after surgery
45
17
28
81 - 7.2
8
4
4
65 -+ 11.4
Treated* within 5 years after surgery
37
9
28
72 -+ 11.8
Untreated 5 years after surgery
73
24
49
76 - 10.2
Examined at follow-up
51
21
30
75 +- 10.5
Not attending follow-up
22
3
19
77 - 9.5
Small incision phacoemulsification
*Nd:YAG capsulotomy
In addition to the follow-up study 5 years after cataract surgery, the medical records of the 37 patients who had been treated within the first 5 years after primary surgery were analyzed. The time between surgery and laser treatment was recorded along with the type of surgery and serious intraoperative complications.
Results Seventy-three individuals were invited for examination; 51 (70%) attended. Twenty-two patients were unable to participate because of poor general health, old age, or change of address. Clinically significant PCO was discovered in 7 patients, and they were all treated with an Nd:YAG capsulotomy. Five were re-examined by the nurse after the laser treatment; 4 had improved visual function. Two did not attend the examination because of illness and old age. One patient acquired senile macular degeneration with severe loss of vision after her successful cataract operation. She did not benefit from the Nd:YAG capsulotomy. Mean age at the time of surgery was higher in the group not attending the follow-up examination than in those who did. The ratio of men to women was higher in the examined group than in the group treated within the first 5 years (Table 1). A comparison of the characteristics of the treated group (n = 37), examined group (n = 51), and those not attending (n = 22) shows no obvious differences in surgical technique or rate of complications. In all known cases of complications during surgery (5 of 110), an IOL could be implanted in the eye. The total incidence of clinically 248
significant PCO 5 years after surgery among the patients still alive is shown in Table 2. The incidence of PCO within the first 5 years after surgery was 34%. At the follow-up examination, 7 cases of hidden PCO were found. These, together with the 37 previously treated and an estimated 3 patients with PCO in the group not attending the follow-up examination, made the total estimated PCO incidence 43%. The estimate of PCO in the group not attending the follow-up examination was based on the assumption that the incidence was similar to that of the examined group. A comparison of the characteristics of all patients with PCO (excluding those who had died or had phacoemulsification) and those with no PCO is shown in Table 3. The proportion of women was greater in the PCO than in the no-PCO group (.01 < P < .05, chisquare). There was no difference in surgical technique or complications between the 2 groups. The time between surgery and Nd:YAG laser capsulotomy in the group treated within 5 years was divided into quartiles (15 months). During the first Table 2.
Incidence of clinically significant PCO at 5 years.
.Group
Proportion
Incidence (%)
Patients treated within 5 years after surgery
37/110
34
PCO discovered at follow-up examination
7/51
14
Patients with previously undetected PCO
7 + 3"/110
9
Total incidence of PCO*
37 + 7 + 3"/110
43
*Assumption: same percentage of undetected PCO among patients not attending the follow-up examination
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PCO 5 YEARS AFTER ECCE
Table 3. Characteristics and numbers of patients with and without PCO. With PCO (n = 44)
Without PCO (n = 44)
73 _+ 11.9
74 _+ 10.5
Male
10
20
Female
34
24
Characteristic Mean age (years) at time of surgery Sex
Complications
0*
3
All means _+ SD *Information not available for 2 patients.
quartile, 7 patients were treated, followed by 16, 11, and 3 in the remaining quartiles. Thus, almost all patients were treated within 45 months after surgery as only 3 patients were discovered to have PCO during the last 15 months before the present study. The 7 patients discovered to have hidden PCO in the follow-up study were not included in any quartile. It is unknown when the PCO in these 7 eyes became clinically significant, only that it was discovered shortly after 5 years had passed after primary surgery.
Discussion The 5 year PCO incidence of approximately 40% in this sample is comparable to that in other long-term follow-up studies with a high incidence. 6-8 It shows that PCO is the major complication of ECCE and that almost half of patients will need a postoperative Nd:YAG laser capsulotomy. Most needing laser treatment reach the stage of clinically significant PCO before the end of the fourth postoperative year, and few patients contacted an ophthalmologist to have a capsulotomy thereafter. An advantage of this study is that all participants were followed for 5 years. The participation rate of the study of PCO incidence was 81% (961118), consisting of 51 of 73 attending the follow-up examination and 37 patients treated for PCO within the first 5 postoperative years. Eight patients were excluded after the examination because they had small incision phacoemulsification. The dropout of 22 patients was the result of high average age and morbidity. The incidence of PCO in the those not attending the examination was
estimated to b e the same as in the group examined. One factor known to influence PCO is age. 6 .The younger the patient, the greater the risk of PCO. This was not substantiated in this study sample, which was limited in number. The death rate in this study was 270./0 (45/164) over 5 years. Mean age in the studied group was 78 years at the time of cataract surgery, which may explain the seemingly high death rate. In 1992, Street and Javitt 14 reported the 5 year mortality rate in patients who had had cataract extraction in 1984. For patients 77 years at surgery, the death rate was 39% in men and 23% in women. For those 78 years at surgery, the death rate was 41% and 25%, respectively. We consider these numbers to be comparable to those in the present study. No obvious difference was found in the rate of complications during surgery or in surgical techniques between the groups with and without PCO. An unexpected finding was the higher proportion of women in the group with PCO than in the group without PCO. In the group not attending the follow-up examination, only 3 patients were men. Even if they all had PCO and no woman in that group did, PCO would still be much more common among women in this limited study. This is in accordance with the results presented by Ninn-Pedersen and Bauer, 15 who showed a highly significant difference in PCO incidence between men and women, with the higher incidence among women. However, Westling and Calissendorfin6 did not find a sex or age difference in the risk for capsulotomy. The higher incidence of PCO in women than in men in this study could not be caused by women contacting a doctor at an earlier stage of PCO than the men did. All in the study group were invited to the follow-up examination, and they did not have to take active measures to come to the examination. It will be interesting to see whether PCO is also more common among women than in men in a larger ongoing epidemiological study. In 1989 in a long-term study of PCO, Moisseiev and coauthors 6 reported an untreated group of 15 of 127 cases. At the 1995 meeting of the European Society of Cataract & Refractive Surgeons, Lydahl presented a prospective study of 190 patients with a 2 year followup after cataract surgery. During the 2 years, 18.4% had had a capsulotomy and at the 2 year examination,
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249
PCO 5 YEARS AFTER ECCE
another 15.8% had clinically significant PCO. In the present study, 7 untreated patients with clinically significant P C O were found 5 years after cataract surgery. Two main groups could be identified: those with another eye disease who did not notice the reduced vision resulting from the PCO and those aware of vision reduction but who did not contact an eye clinic for examination. The frequency of previously undetected P C O was 9%, which in a study of this size means only a few individuals but extrapolated to the population in Sweden operated upon during a year (approximately 50 000) amounts to thousands of individuals. In this study, half the patients with previously undetected PCO would benefit from capsulotomy. Considering the large number of patients who will need capsulotomy at some point, the undetected cases of PCO still constitute a small group, and it would probably be too costly to carry out organized long-term follow-up examinations to find them. The resources needed for long-term follow-up of all patients having cataract surgery are great, and PCO is not blinding but rather treatable, even when treatment is delayed. Instead, improved information about PCO at the time of cataract surgery could increase patients' motivation for scheduling an eye examination if they experience decreasing vision. In conclusion, this study shows that the incidence of PCO 5 years after ECCE was about 40% and appeared to be more common in women than in men. There was an untreated group with PCO comprising approximately 9% of the surgically treated population. Half of them would have benefited from treatment, while the other half had another vision-reducing eye disease. The hidden group must be considered in epidemiological studies of PCO.
References 1. Apple DJ, Solomon KD, Tetz MR, et al. Posterior capsule opacification. Surv Ophthalmol 1992; 37:73-116 2. McDonnell PJ, Zarbin MA, Green WR. Posterior capsule opacification in pseudophakic eyes. Ophthalmology 1983; 90:1548-1553 3. Llesegang TJ, Bourne WM, Ilstrup DM. Secondary surgical and neodymium-YAG laser discissions. Am J Ophthalmol 1985; 100:510-519 . 4. Steinert RF, Puliafito CA, Kumar SR, et al. Cystoid macular edema, retinal detachment, and glaucoma after
250
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
Nd:YAG laser posterior capsulotomy. Am J Ophthalmol 1991; 112:373-380 Maltzman BA, Haupt E, Notis C. Relationship between a.ge at time of cataract extraction and time interval before capsulotomy for opacification. Ophthalmic Surg 1989; 20:321-324 Moisseiev J, Bartov E, Schochat A, Blumenthal M. Long-term study of the prevalence of capsular opacification following extracapsular cataract extraction. J Cataract Refract Surg 1989; 15:531-533 Wilhelmus KR, Emery JM. Posterior capsule opacification following phacoemulsification. Ophthalmic Surg 1980; 11:264-267 Sterling S, Wood TO. Effect of intraocular lens convexity on posterior capsule opacification. J Cataract Refract Surg 1986; 12:655-657 Nishi O. Incidence of posterior capsule opacification in eyes with and without posterior chamber intraocular lenses. J Cataract Refract Surg 1986; 12:519-522 Downing JE. Long-term discission rate after placing posterior chamber lenses with the convex surface posterior. J Cataract Refract Surg 1986; 12:651-654 Percival SPB, Setty SS. Analysis of the need for secondary capsulotomy during a five-year follow-up. J Cataract Refract Surg 1988; 14:379-382 Born CP, Ryan DK. Effect of intraocular lens optic design on posterior capsular opacification. J Cataract Refract Surg 1990; 16:188-192 Frezzotti R, Caporossi A. Pathogenesis of posterior capsular opacification. Part I. Epidemiological and clinicostatistical data. J Cataract Refract Surg 1990; 16:347352 Street DA, Javitt JC. National five-year mortality after inpatient cataract extraction. Am J Ophthalmol 1992; 113:263-268 Ninn-Pedersen K, Bauer B. Cataract patients in a defined Swedish population 1986-1990. VI. YAG laser capsulotomies in relation to preoperative and surgical conditions. Acta Ophthalmol Scand 1997; 75:551-557 Westling AK, Calissendorff BM. Factors influencing the formation of posterior capsular opacities after extracapsular cataract extraction with posterior chamber lens implant. Acta Ophthalmol 1991; 69:315-320
From the Department of Ophthalmology, Institute of Clinical Neuroscience, Sahlgrenska University Hospital, Gothenburg, Sweden. Presentedat the XIVth Congressof the European Society of Cataract & Rqfi'active Surgeons, Gothenburg, Sweden, October 1996. Supported by GOteborg Medical Society and the Swedish Medical Research Council grant 0226. Maths Abrahamsson, MD, and Bo Car&on, MD, provided helpful discussions.
J CATARACTREFRACTSURG--VOL 25, FEBRUARY1999
Setting: Department of Ophthalmology, Sahlgrenska University Hospital, Gothenburg, Sweden.
Methods: A random sample (n = 164) was selected among patients who had extracapsular cataract extraction (ECCE) with intraocular lens implantation in 1991 (N = 1672). All surgically treated cases that required neodymium:YAG (Nd.:YAG) laser capsulotomy (n = 37) within the first 5 years after surgery were recorded. Patients still alive 5 years after surgery who had not had Nd:YAG treatment were offered an eye examination to determine whether PCO requiring capsulotomy existed.
Results:Thirty-seven of 110 patients (34%) alive 5 years after surgery had had an Nd:YAG capsulotomy during the first 5 postoperative years. Follow-up was possible in 51 of 73 untreated patients (70%). Clinically significant PCO according to specified criteria was found in 7 cases (14%). Half of them would benefit from treatment; the other half had visual impairment from other eye disease.
Conclusions: The estimated incidence of PCO 5 years after ECCE was 43%..Five years after surgery, there was an untreated group with clinically significant PCO, approximately 9% of the surgically treated population. This hidden group must be considered in, PCO studies, J Cataract Refract Surg 1999; 25:246-250
l xtracapsular cataract extraction (ECCE) with in,traocular lens (IOL) implantation has been performed increasingly since the beginning of the 1980s. The most common complication is posterior capsule opacification (PCO). ~It is generally accepted that PCO formation is a manifestation of proliferation of preequatorial epithelial cells. It consists of formations of Elschnig pearls, multiple layers of proliferated epithelium, and cells showing myofibroblastic differentiation on .the posterior capsule. Contraction of the myofibroblasts produces numerous tiny wrinkles in the posterior
E
Acceptedfbr publication July 15, 1998. Reprint requests to Karin Sundelin, Department of Ophthalmolog~ Sahlgrenska University Hospita~ 413 45 Gothenburg, Sweden. 246
capsule, resulting in visual distortion, z Posterior capsule opacification may be successfully treated with a neodymium:YAG (Nd:YAG) laser capsulotomy, which is preferred to surgical discission. 3 The Nd:YAG capsulotomy, however, has the disadvantages of inconvenience and cost to the patient, cost to society, and several medical complications, of which the most serious are retinal detachment and macular edema.4 It is therefore important to characterize risk factors for the development of PCO that impairs vision and to establish the impact of PCO on vision after cataract surgery. The incidence of PCO has been reported to be from 3% to more than 50%. Most studies in adults with a follow-up of 3 to 5 years report incidences approaching the latter figure. It is difficult to assess
J CATARACT REFRACT SURG---VOL 25, FEBRUARY 1999
PCO 5 YEARS AFTER ECCE
these studies because most are conducted using consecutive patients and therefore have varying follow-ups. In addition, exclusion criteria are not always accounted for. It is sometimes not evident whether follow-up means that patients are re-examined or whether material is collected only from medical records. In the latter case, patients who do not take active measures to schedule a follow-up examination are systematically excluded. Different authors have used varying criteria to classify their cases, and the indications for performing capsulotomies vary. Surgical techniques and materials are disparate. 3'5-13 The number of Nd:YAG laser capsulotomies performed is commonly used to measure the incidence of PCO. 3'5'6'1°'13 To obtain a more precise picture of the impact of PCO after ECCE and IOL implantation, estimation of its incidence in long-term follow-up studies in epidemiologically defined populations is important. In addition to patients treated for PCO, careful examination of untreated patients must be done. We examined a sample of cataract patients 5 years after surgery. The principal purpose of this initial study was to find and evaluate the proportion of "hidden" cases fulfilling our end-point criteria for PCO who may benefit from laser treatment. A secondary aim was to find the incidence of PCO. This information is needed to examine risk factors for PCO development, with the long-term goal of finding ways to prevent or delay it.
Patients and Methods A sample was selected from patients who had ECCE with IOL implantation during 1991 at the Eye Clinic of Sahlgrenska University Hospital. The Eye Clihic performed more than 90% of all cataract operations in a well-defined population of approximately 630,000 inhabitants at that time. In 1991, cataract surgery was done in 1672 patients. Because of seasonal variations in the frequency of surgery, 10% of the annual number of patients had surgery in January. They were considered a representative sample (n = 164). There were no indications of systematic differences between the sample and the total group of cataract surgery patients. Extracapsular cataract extraction with the goal of posterior IOL implantation was carried out in 1991 in a mixed population by 7 surgeons using the same
criteria for surgery. The lenses most commonly used were poly(methyl methacrylate) (PMMA) with polylSropylene (Prolene®) haptics or single-piece PMMA with heparin coating. The most frequent surgical technique was conventional ECCE, but 8 of 118 patients had small incision phacoemulsification and capsulorhexis. These 8 patients were included in the present study but have subsequently been excluded from the analysis. One patient was excluded from the sample because the surgery had been done using aft intracapsular technique. At the time of the study, 5 years after surgery, 45 persons had died (5 had had an Nd:YAG capsulotomy). The mean survival time after cataract surgery was 28.8 months. Thirty-seven patients had been treated with Nd:YAG laser capsulotomy within the 5 years after primary surgery. Left to evaluate were 73 individuals. They were all invited to an examination by 1 surgeon (K.S.) shortly after the 5 years had expired. The examination included measurement of best corrected visual acuity (BCVA) with optimal correction on a Snellen acuity chart, indirect ophthalmoscopy, slitlamp evaluation, and tonometry. Apart from the examination results, the following parameters were recorded: age; sex; type of operation; BCVA after surgery; serious intraoperative complications; comorbidity such as diabetes mellitus, glaucoma, uveitis, or other vision-reducing eye disease; and symptoms such as glare or reduced vision. Nine of the 51 patients examined had diabetes mellitus and 11 glaucoma in the treated eye. None had uveitis. The following definition of clinically significant PCO was used in accordance with the criteria for clinically significant PCO requiring Nd:YAG laser treatment: (1) redtiction in visual acuity by 2 lines compared with BCVA early in the postoperative period; (2) PCO seen against the red reflex by ophthalmoscopy; (3) PCO visible within the central area of the pupil seen at the slitlamp; (4) reports of glare, reduced vision, or both. If the patient had another visionreducing eye disease, all criteria had to be fulfilled except the first one. Patients with clinically significant PCO at the time of the examination were offered an Nd:YAG laser capsulotomy. Laser-treated patients were invited to a postlaser examination performed by a trained nurse. This examination included BCVA and the patient's subjective evaluation of the treatment.
J CATARACTREFRACTSURG--VOL25, FEBRUARY1999
247
PCO 5 YEARS AFTER ECCE
Table 1.
Baseline patient characteristics at the time of ECCE surgery. ....
~i,~Che~actel;istic:~.
~
'
Number
Men
Women
Age (Years) at Surgery Mean +_ SD
Entire group
163
54
109
78 -+ 10.8
Alive 5 years after surgery
118
37
81
74 -+ 11.1
Dead 5 years after surgery
45
17
28
81 - 7.2
8
4
4
65 -+ 11.4
Treated* within 5 years after surgery
37
9
28
72 -+ 11.8
Untreated 5 years after surgery
73
24
49
76 - 10.2
Examined at follow-up
51
21
30
75 +- 10.5
Not attending follow-up
22
3
19
77 - 9.5
Small incision phacoemulsification
*Nd:YAG capsulotomy
In addition to the follow-up study 5 years after cataract surgery, the medical records of the 37 patients who had been treated within the first 5 years after primary surgery were analyzed. The time between surgery and laser treatment was recorded along with the type of surgery and serious intraoperative complications.
Results Seventy-three individuals were invited for examination; 51 (70%) attended. Twenty-two patients were unable to participate because of poor general health, old age, or change of address. Clinically significant PCO was discovered in 7 patients, and they were all treated with an Nd:YAG capsulotomy. Five were re-examined by the nurse after the laser treatment; 4 had improved visual function. Two did not attend the examination because of illness and old age. One patient acquired senile macular degeneration with severe loss of vision after her successful cataract operation. She did not benefit from the Nd:YAG capsulotomy. Mean age at the time of surgery was higher in the group not attending the follow-up examination than in those who did. The ratio of men to women was higher in the examined group than in the group treated within the first 5 years (Table 1). A comparison of the characteristics of the treated group (n = 37), examined group (n = 51), and those not attending (n = 22) shows no obvious differences in surgical technique or rate of complications. In all known cases of complications during surgery (5 of 110), an IOL could be implanted in the eye. The total incidence of clinically 248
significant PCO 5 years after surgery among the patients still alive is shown in Table 2. The incidence of PCO within the first 5 years after surgery was 34%. At the follow-up examination, 7 cases of hidden PCO were found. These, together with the 37 previously treated and an estimated 3 patients with PCO in the group not attending the follow-up examination, made the total estimated PCO incidence 43%. The estimate of PCO in the group not attending the follow-up examination was based on the assumption that the incidence was similar to that of the examined group. A comparison of the characteristics of all patients with PCO (excluding those who had died or had phacoemulsification) and those with no PCO is shown in Table 3. The proportion of women was greater in the PCO than in the no-PCO group (.01 < P < .05, chisquare). There was no difference in surgical technique or complications between the 2 groups. The time between surgery and Nd:YAG laser capsulotomy in the group treated within 5 years was divided into quartiles (15 months). During the first Table 2.
Incidence of clinically significant PCO at 5 years.
.Group
Proportion
Incidence (%)
Patients treated within 5 years after surgery
37/110
34
PCO discovered at follow-up examination
7/51
14
Patients with previously undetected PCO
7 + 3"/110
9
Total incidence of PCO*
37 + 7 + 3"/110
43
*Assumption: same percentage of undetected PCO among patients not attending the follow-up examination
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PCO 5 YEARS AFTER ECCE
Table 3. Characteristics and numbers of patients with and without PCO. With PCO (n = 44)
Without PCO (n = 44)
73 _+ 11.9
74 _+ 10.5
Male
10
20
Female
34
24
Characteristic Mean age (years) at time of surgery Sex
Complications
0*
3
All means _+ SD *Information not available for 2 patients.
quartile, 7 patients were treated, followed by 16, 11, and 3 in the remaining quartiles. Thus, almost all patients were treated within 45 months after surgery as only 3 patients were discovered to have PCO during the last 15 months before the present study. The 7 patients discovered to have hidden PCO in the follow-up study were not included in any quartile. It is unknown when the PCO in these 7 eyes became clinically significant, only that it was discovered shortly after 5 years had passed after primary surgery.
Discussion The 5 year PCO incidence of approximately 40% in this sample is comparable to that in other long-term follow-up studies with a high incidence. 6-8 It shows that PCO is the major complication of ECCE and that almost half of patients will need a postoperative Nd:YAG laser capsulotomy. Most needing laser treatment reach the stage of clinically significant PCO before the end of the fourth postoperative year, and few patients contacted an ophthalmologist to have a capsulotomy thereafter. An advantage of this study is that all participants were followed for 5 years. The participation rate of the study of PCO incidence was 81% (961118), consisting of 51 of 73 attending the follow-up examination and 37 patients treated for PCO within the first 5 postoperative years. Eight patients were excluded after the examination because they had small incision phacoemulsification. The dropout of 22 patients was the result of high average age and morbidity. The incidence of PCO in the those not attending the examination was
estimated to b e the same as in the group examined. One factor known to influence PCO is age. 6 .The younger the patient, the greater the risk of PCO. This was not substantiated in this study sample, which was limited in number. The death rate in this study was 270./0 (45/164) over 5 years. Mean age in the studied group was 78 years at the time of cataract surgery, which may explain the seemingly high death rate. In 1992, Street and Javitt 14 reported the 5 year mortality rate in patients who had had cataract extraction in 1984. For patients 77 years at surgery, the death rate was 39% in men and 23% in women. For those 78 years at surgery, the death rate was 41% and 25%, respectively. We consider these numbers to be comparable to those in the present study. No obvious difference was found in the rate of complications during surgery or in surgical techniques between the groups with and without PCO. An unexpected finding was the higher proportion of women in the group with PCO than in the group without PCO. In the group not attending the follow-up examination, only 3 patients were men. Even if they all had PCO and no woman in that group did, PCO would still be much more common among women in this limited study. This is in accordance with the results presented by Ninn-Pedersen and Bauer, 15 who showed a highly significant difference in PCO incidence between men and women, with the higher incidence among women. However, Westling and Calissendorfin6 did not find a sex or age difference in the risk for capsulotomy. The higher incidence of PCO in women than in men in this study could not be caused by women contacting a doctor at an earlier stage of PCO than the men did. All in the study group were invited to the follow-up examination, and they did not have to take active measures to come to the examination. It will be interesting to see whether PCO is also more common among women than in men in a larger ongoing epidemiological study. In 1989 in a long-term study of PCO, Moisseiev and coauthors 6 reported an untreated group of 15 of 127 cases. At the 1995 meeting of the European Society of Cataract & Refractive Surgeons, Lydahl presented a prospective study of 190 patients with a 2 year followup after cataract surgery. During the 2 years, 18.4% had had a capsulotomy and at the 2 year examination,
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another 15.8% had clinically significant PCO. In the present study, 7 untreated patients with clinically significant P C O were found 5 years after cataract surgery. Two main groups could be identified: those with another eye disease who did not notice the reduced vision resulting from the PCO and those aware of vision reduction but who did not contact an eye clinic for examination. The frequency of previously undetected P C O was 9%, which in a study of this size means only a few individuals but extrapolated to the population in Sweden operated upon during a year (approximately 50 000) amounts to thousands of individuals. In this study, half the patients with previously undetected PCO would benefit from capsulotomy. Considering the large number of patients who will need capsulotomy at some point, the undetected cases of PCO still constitute a small group, and it would probably be too costly to carry out organized long-term follow-up examinations to find them. The resources needed for long-term follow-up of all patients having cataract surgery are great, and PCO is not blinding but rather treatable, even when treatment is delayed. Instead, improved information about PCO at the time of cataract surgery could increase patients' motivation for scheduling an eye examination if they experience decreasing vision. In conclusion, this study shows that the incidence of PCO 5 years after ECCE was about 40% and appeared to be more common in women than in men. There was an untreated group with PCO comprising approximately 9% of the surgically treated population. Half of them would have benefited from treatment, while the other half had another vision-reducing eye disease. The hidden group must be considered in epidemiological studies of PCO.
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From the Department of Ophthalmology, Institute of Clinical Neuroscience, Sahlgrenska University Hospital, Gothenburg, Sweden. Presentedat the XIVth Congressof the European Society of Cataract & Rqfi'active Surgeons, Gothenburg, Sweden, October 1996. Supported by GOteborg Medical Society and the Swedish Medical Research Council grant 0226. Maths Abrahamsson, MD, and Bo Car&on, MD, provided helpful discussions.
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