- Email: [email protected]
One million cataract surgeries: Swedish National Cataract Register 1992–2009
REVIEW/UPDATE
One million cataract surgeries: Swedish National Cataract Register 1992–2009 Anders Behndig, MD, PhD, Per Montan, MD, PhD, Ulf Stenevi, MD, PhD, Maria Kugelberg, MD, PhD, Mats Lundstr€ om, MD, PhD
This review summarizes data collected by the Swedish National Cataract Register, which now contains data pertaining to more than a million cataract surgery procedures, representing 95.6% of the surgeries performed in Sweden during 1992 2009. During this period, the rate of cataract surgery rose from 4.47 to 9.00 per 1000 inhabitants. The mean patient age increased until 1999 but has slowly decreased since then. Preoperative visual acuity has risen steadily. The distribution between the sexes was stable until 2000, after which the proportion of women slowly decreased. Registration of subjective benefit has brought new knowledge regarding indications and expectations. An improved questionnaire, Catquest-9SF has been used since 2008. The outcome register generally shows good results from the surgery. Endophthalmitis has decreased from 0.10% to below 0.040%. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2011; 37:1539–1545 Q 2011 ASCRS and ESCRS
The Swedish National Cataract Register (NCR) was founded on January 1, 1992,1 primarily to monitor the effects of a newly initiated national healthcare guarantee. The register and its administrative unit, located in Blekinge Hospital, Karlskrona, Sweden,2,3 is financed by the Swedish Association of Local Authorities and Regions and is administered by a steering committee approved by the Swedish Ophthalmological Society.3 Reporting to the register is now primarily Internet-based via the homepage.A
Submitted: January 24, 2011. Final revision submitted: April 6, 2011. Accepted: May 1, 2011. From the Department of Clinical Sciences/Ophthalmology (Behndig), Umea˚ University Hospital, Umea˚, St. Erik Eye Hospital (Montan, Kugelberg), Karolinska Institutet, Stockholm, Department of Ophthalmology (Stenevi), Sahlgrenska University Hospital, M€ olndal, and EyeNet Sweden (Lundstr€om), Blekinge Hospital, Karlskrona, Sweden. Supported by the Swedish Association of Local Authorities and Regions and the Swedish National Board of Health and Welfare. Corresponding author: Anders Behndig, MD, PhD, Department of Clinical Sciences/Ophthalmology, Umea˚ University, SE-901 87 Umea˚, Sweden. E-mail: [email protected]. Q 2011 ASCRS and ESCRS Published by Elsevier Inc.
During the 18 years of the NCR, roughly 50 clinics have reported to the register with a mean reporting frequency of 95.6% of all cataract procedures performed. The register includes a core register and since 1994, an outcomes register. Since 1995, the patient's subjective benefit from surgery and, indirectly, the indications for surgery have been monitored via the Catquest questionnaire.4 Since 1998, each case of endophthalmitis associated with cataract surgery has also been registered. Since its inception, the NCR has monitored and reported trends and results of cataract surgery in Sweden and complications too uncommon to be assessed by individual clinics, such as unplanned postoperative aphakia5,6 and endophthalmitis.7–9 THE CORE REGISTER The following variables are registered in the core register for all cataract procedures: surgical unit; running number of the procedure; patient's year of birth, county, sex, visual acuity in both eyes; date when the patient was put on the waiting list; date of surgery; previous cataract surgery in the fellow eye; ocular comorbidity in the eye planned for surgery (macular degeneration, glaucoma, diabetic retinopathy, or other); surgical technique; position and material of the intraocular lens (IOL); intraoperative antibiotic prophylaxis; and occurrence of “communication between the anterior chamber and the vitreous.” The use of 0886-3350/$ - see front matter doi:10.1016/j.jcrs.2011.05.021
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specially designed IOLs (aspheric, yellow, or multifocal) and intraoperative difficulties warranting altered surgical techniques have been registered since 2008. COVERAGE OF THE NATIONAL CATARACT REGISTER The frequency of reporting clinics was high even in 1992. From 1992 to 2009, 1 079 087 of 1 128 516 cataract procedures were registered in the NCR, corresponding to 95.6% (Table 1). This means the NCR remains highly representative for Swedish cataract surgery. WAITING TIMES The waiting time for cataract surgery in Sweden increased during the early years of the NCR and reached a maximum in the year 2000, after which it decreased, particularly after 2006. A national guarantee of healthcare was in force between 1992 and 1996, and a similar guarantee was reintroduced in November 2005. Both guarantees state that the patient has the right to surgery within 3 months after the decision to operate is made.
Figure 1. Number of cataract procedures in the register divided by first-eye and second-eye surgeries.
instead of (as earlier) a maximum annual number. According to the World Health Organization definition, the surgery rate was between 8000 and 9000 procedures per 1 million citizens from 2000 to 2009 (Figure 2).
SURGERY VOLUMES The number of surgeries increased substantially during 1992 to 2002 and then leveled off (Figure 1). In 2009, however, about 10 000 more procedures were performed than in 2008. Closer analysis shows that this change occurred in the Stockholm region, where the reimbursement system was altered to include all cataract patients referred to the operating clinics
Table 1. Reporting frequency among participating clinics in the Swedish National Register. Percentage Reported, n (%) Year
R97%
90–96%
75–89%
!75%
Total Clinics, n
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
27 (68) 35 (74) 40 (78) 34 (68) 41 (87) 38 (78) 41 (84) 40 (83) 40 (77) 46 (79) 47 (81) 47 (84) 49 (86) 49 (88) 44 (80) 44 (83) 43 (81) 48 (84)
7 7 6 9 3 8 6 4 9 8 9 7 5 6 8 5 6 6
5 1 2 3 2 1 2 1 1 4 1 2 3 1 2 4 4 3
1 4 3 4 1 2 0 3 2 0 1 0 0 0 1 0 0 0
40 47 51 50 47 49 49 48 52 58 58 56 57 56 55 53 53 57
AGE DISTRIBUTION Figure 3 shows the age distribution for each of the 18 years. The mean age at surgery increased from 75.1 years in 1992 to 76.2 years in 1999, after which it decreased to 74.9 years in 2009. The likely explanations for this are first, the demographic profile of the population, with many people born in the 1940s, and second, the shortened waiting lists, meaning that cataract surgery now more closely reflects the true incidence of cataract in the population. SECOND-EYE SURGERY The proportion of patients having cataract surgery in the second eye increased from 28.5% to 40.4% from 1992 to 2009. In absolute numbers, the surgical
Figure 2. Total number of cataract operations per 1 million citizens in Sweden, 2000–2009.
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below this has continually decreased, from 44% in 1992 to 22% in 2009. The gradual increase in preoperative visual acuity is interpreted as a shift in the indications following improved surgical technique and results.
Figure 3. The total number of procedures in each age group during each year from 1992 to 2009.
volumes increased by 40 000, with roughly equal numbers of first eyes and second eyes (Figure 1). SURGICAL TECHNIQUE Surgical technique and type of IOL were added to the core registry in 1997. The first years of this registration showed the final transition to the phacoemulsification technique and to the use of hydrophobic acrylic IOLs.3
SEX A difference in surgical frequency between the sexes was noted early10 and has largely remained. The proportion of women was around 66% from 1992 to 2000 and gradually decreased to 61% in 2009. There appears to be a relationship between a high age at surgery and the percentage of women operated on, probably explained by differences in life expectancy between the sexes. The mean waiting time for surgery was 2.83 months for women (median, 2 months) and 2.72 months for men (median, 2 months). Surgery was performed within 6 months in 93.4% of the women versus 93.8% of the men. Surgical technique, complications, and results did not differ between the sexes, and ocular comorbidity was equally common in women (32.4%) and men (33.3%). Men were operated on outside their home county slightly more often (4.0% versus 3.2%). Figure 5 shows the parameters for surgical volume, mean age, and sex. Initially, the surgical volumes
VISUAL ACUITY The median visual acuity of the better eye was 0.5 in the early days of the NCR and rose to 0.6 in 1998; the median visual acuity of the eye planned for surgery increased from 0.1 in 1992 to 0.4 in 2009. The proportion of patients seeing 0.1 or less in the eye to be operated on or 0.8 or more in the other eye is shown on an annual basis in Figure 4. A functionally relevant visual acuity is 0.5 in the better eyedthe basic requirement for holding a driver's license in Sweden. The fraction of patients
Figure 4. Development of preoperative visual acuity, 1992 to 2009. The left bar shows the percentage of patients with visual acuity of 0.1 or less in the eye to be operated on; the right bar shows the percentage with a visual acuity 0.8 or more in the other eye. The lines are trend lines.
Figure 5. Number of cataract procedures (white; scale to the right), mean age (gray; scale to the left), and percentage of women having surgery (black; scale to the left), 1992 to 2009.
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increased gradually as more older patients were operated on, but the sex distribution remained constant. After the turn of the century, surgical volumes decreased, along with mean age and percentage of women. THE OUTCOME REGISTER The outcome register, in use since 1995, covers all operations of the participating clinics during the month of March, which corresponds to about 8% of all cases. Analyses show that March matches the rest of the year in terms of patient demographics. The following preoperative variables were registered: running number of the procedure, keratometric values (K values) in diopters (D) (with axes), and planned refraction. Postoperative registration included date of the final visit, visual acuity and refraction in both eyes, K values in the operated eye (with axes), ocular comorbidity in the operated eye, and reasons for loss to follow-up (poor compliance, death). When the data were registered and reported, the final visit occurred within 4 months of the procedure in 97.3% of the cases. Self-assessed visual function was evaluated with the Catquest instrument preoperatively and postoperatively; the final form was completed approximately 3 months after surgery. INDUCED ASTIGMATISM Figure 6 shows the induced astigmatism over the years. This parameter has diminished over time, probably owing to the transition from extracapsular technique via standard incision phacoemulsification to today's small incisions with foldable IOLs. However, one should be aware that deliberate modification of the astigmatism by placement of the incision might have influenced the results in recent years.
Figure 6. Mean induced astigmatism in diopters, assessed with the subtraction method, for the clinics participating in this registration from 1995 to 2009. Each year is represented by a box containing 50% of the values. The dark line is the median value and 95% of the values are within the vertical lines. The rings are outliers.
BIOMETRY PREDICTION ERROR Figure 7 shows the change in biometry prediction error over the years for the 9 clinics that participated in this registration every year since 1995. This variable reflects both the precision of the preoperative biometrical measurement and the surgical technique. Accurate determination of differences below 0.5 D are not possible because of limited measurement precision. Several factors may explain why the planned refraction was not achieved. Female sex, glaucoma, and a low preoperative visual acuity are risk factors for a larger biometry prediction error.11 The error was not smaller in second-eye surgeries than in first-eye surgeries, but the biometry prediction error has generally decreased over the years. From 1999, the refraction of the fellow eye has also been registered because too large a difference may influence visual comfort and lead to difficulties in performing daily tasks.12 Figure 8 shows the difference in refraction between the eye operated on and the fellow eye in patients having second-eye surgery. The median value has decreased from 0.5 to 0.4 D, and the spread of values has also decreased.
SUBJECTIVE (PERCEIVED) BENEFIT FROM SURGERY Results from various projects performed to evaluate the perceived benefit from surgery, measured by Catquest, are summarized below: The benefit from cataract surgery in patients 85 years of age or older without other ocular disease was as good as the benefit in younger patients.13
Figure 7. Biometry prediction error for the 9 clinics participating in the outcomes registration every year from 1995 to 2009. Each year is represented by a box containing 50% of the values. The dark line is the median value, and 95% of the values are within the vertical lines. Rings denote outliers and asterisks denote extreme values.
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Figure 8. Difference in refraction (spherical equivalent, absolute values) between the operated eye and the fellow eye. Only patients having second-eye surgery are included. Each year is represented by a box containing 50% of the values. The dark line is the median value, and 95% of the values are within the vertical lines. Rings denote outliers and asterisks denote extreme values.
The most common reason for no perceived benefit from surgery was ocular comorbidity in the eye having surgery.4,14 Cataract surgery in both eyes gave a significantly better outcome than surgery in 1 eye only.4,14,15 Younger patients who have had surgery in both eyes experienced the greatest improvement.14 Two common causes of perceived worsening at 6 months, compared with preoperatively, were cataract in the fellow eye and anisometropia.4 Patients with simultaneous age-related macular degeneration perceived a significantly improved visual function postoperatively. The strongest predictor for subjective improvement was the level of visual acuity achieved.16 Improvement in self-assessed visual function after cataract surgery was long-term; about 80% of those operated on 7 to 8 years earlier still experienced improved visual function.17 Women assessed their visual problems as more severe preoperatively and postoperatively, but the subjective improvement from surgery was slightly larger in women.18 Overall, cataract patients were significantly helped by surgery. After surgery, their subjective visual disturbance was reduced and their level of activity increased. REVISION OF CATQUEST During 2006, a revision of the Catquest questionnaire was initiated. The original questionnaire, developed from 1993 to 1995, was deemed dated in the face of
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modern demands regarding psychometric qualities and analysis of question constructions (item-response theory). The Catquest registration was temporarily paused in 2007 during the revision, in which both classical test theory and Rasch analysis were used.19 In 2008, the new instrument, Catquest-9SF, was tested by 6 clinics. A good correlation between the preoperative score and the visual acuity of the best eye before surgery (r Z 0.432) was demonstrated. The postoperative score correlated well with the visual acuity of the operated eye (r Z 0.470). The mean preoperative score was 0.35 logits G 1.7 (SD), and the mean postoperative score was 2.33 G 1.62 logits, a statistically significant improvement. The change in score from surgery corresponded to an effect size of 1.17 (improvement/SD). Thus, the good psychometric properties from the revision were confirmed; high precision, good targeting, and high effect size. Worsened self-assessed visual function was reported by 10.1% of the patients. In 2009, 24 clinics provided Catquest-9SF data. Table 2 shows the percentage of patients who perceived fewer restrictions in performing activities of daily life after cataract surgery. ENDOPHTHALMITIS REGISTER A registration of all endophthalmitis cases after cataract surgery was commenced in January 1998, with the participation of all clinics reporting to the NCR. For each suspected postoperative endophthalmitis case, a registration is made, including information about the result of the intraocular culture sample. A final report is made after 3 months, stating the type of prophylaxis used and the final visual acuity of the affected eye. The number of postoperative endophthalmitis cases was lower from 1999 to 2009 than in 1998 (Figure 9).7,8 From the end Table 2. Percentage of patients perceiving less restriction in performing activities of daily life after a cataract extraction.
Year
Percentage Reporting Less Restriction
Questionnaire
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
90.9 90.5 91.3 91.6 90.6 90.3 92.5 90.9 92.6 92.2 92.3 93.3 d 92.8 93.3
Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest No questionnaire Catquest-9SF Catquest-9SF
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of 1999, the type of prophylaxis used was assessed through enquiries to the participating clinics and, later, this information was included in the core register. Analyses clearly showed that intraocular cefuroxime reduced the frequency of postoperative endophthalmitis.8,9 The postoperative endophthalmitis registrations have led to several positive developments; diagnostic routines have improved and intracameral cefuroxime has been adopted all over the country, resulting in a decreased incidence of postoperative endophthalmitis. The results inspired the European Society of Cataract and Refractive Surgeons to perform a randomized multicenter study to evaluate different prophylaxis modalities. This study confirmed the Swedish experience, and intracameral cefuroxime has since become a suggested European standard.20,21 To further assess risk factors for postoperative endophthalmitis, the Swedish registrations were expanded in 2002 to include incision details, the use of an IOL injector, and posterior capsule rupture.9 The latter was associated with a higher risk for postoperative endophthalmitis, but IOL injectors could not be demonstrated to lower the risk. There was, however, a trend toward a relationship between strictly corneal versus sclerocorneal incisions and temporal versus 12 o'clock incisions and endophthalmitis (1 extra postoperative endophthalmitis case in 6000 procedures).9 CLINICAL IMPROVEMENT PROJECT In 2003, all clinics were invited to participate in a national clinical improvement project, aiming (among other things) to define national indications for cataract extraction (Swedish acronym NIKE). The NIKE instrument is based on the visual acuity of both eyes, a patient enquiry assessing problems in performing daily activities, cataract symptoms, and independent living. After a validation study involving 7 clinics, the instrument was deemed reliable and reproducible. A new NIKE-based variable, indication group, was added to the core register from 2005.22 The NIKE was reevaluated and revised in 2007.
Table 3. Posterior capsule rupture leading to a communication between the anterior and posterior segments, 2002 2009.
Year
Surgeries with Capsule Complication
Total Number of Surgeries
% Capsule Complication
2 121 1 902 1 767 1 594 1 284 1 367 1 216 1 328 12 579
75 770 73 994 75 681 77 591 72 568 72 306 72 443 82 470 602 823
2.8 2.6 2.3 2.1 1.8 1.9 1.7 1.6 2.1
2002 2003 2004 2005 2006 2007 2008 2009 Total period
POSTERIOR CAPSULE RUPTURE Posterior capsule rupture is one of the most significant intraoperative complications in cataract surgery and has been part of the core registration since 2002. Table 3 presents the results of 8 years of registration of posterior capsule rupture, showing a gradually declining incidence. An in-depth retrospective analysis of the causes of capsule rupture and the outcomes in these cases was performed in 10 clinics in 2006, investigating the procedures of 2003. This work resulted in 4 reports.23–26 FINAL REMARKS As an ophthalmic registry, the NCR has no precedent on an international level in coverage and persistence. The overall aim of the registry is to provide healthcare professionals and authorities with information regarding cataract care, patient characteristics, morbidity, and surgical quality and accessibility. The data should serve as benchmarking for further improvement. This 18-year review demonstrates a substantial positive development in Swedish cataract surgery. Complications have declined, and the outcome (visual gain, refractive precision, self-reported patient satisfaction) has improved. Surgery is now being performed in younger and healthier eyes, with a greater improvement potential, which correlates significantly with the improved results. In addition, if eyes with equal levels of preoperative vision are compared over this 18-year period, the results have improved, suggesting that refinement of surgical equipment and devices and improved surgical techniques have been instrumental in this development. REFERENCES
Figure 9. Incidence of confirmed endophthalmitis after cataract surgery in Sweden, 1998 to 2009.
€m M, Thorburn W. A National Cataract Reg1. Stenevi U, Lundstro ister. I. Description and epidemiology. Acta Ophthalmol Scand 1995; 73:41–44 €m M, Stenevi U, Ehinger B. Data reliability 2. Ha˚kansson I, Lundstro and structure in the Swedish National Cataract Register. Acta Ophthalmol Scand 2001; 79:518–523. Available at:
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http://www3.interscience.wiley.com/cgi-bin/fulltext/120709514/ PDFSTART. Accessed May 5, 2011 €m M, Stenevi U, Thorburn W. The Swedish National Lundstro Cataract Register: a 9-year review. Acta Ophthalmol Scand 2002; 80:248–257. Available at: http://www3.interscience. wiley.com/cgi-bin/fulltext/118927388/PDFSTART. Accessed May 5, 2011 € m M, Brege KG, Floren I, Stenevi U, Thorburn W. Impaired Lundstro visual function after cataract surgery assessed using the Catquest questionnaire. J Cataract Refract Surg 2000; 26:101–108 €m M, Brege KG, Flore n I, Lundh B, Stenevi U, Lundstro Thorburn W. Postoperative aphakia in modern cataract surgery. Part 2: detailed analysis of the cause of aphakia and the visual outcome. J Cataract Refract Surg 2004; 30:2111–2115 €m M, Brege KG, Flore n I, Lundh B, Stenevi U, Lundstro Thorburn W. Postoperative aphakia in modern cataract surgery. Part 1: analysis of incidence and risks based on 5-year data from the Swedish National Cataract Register. J Cataract Refract Surg 2004; 30:2105–2110 €m M, Stenevi U, Thorburn W. EndophthalmiMontan P, Lundstro tis following cataract surgery in Sweden. The 1998 national prospective survey. Acta Ophthalmol Scand 2002; 80:258–261. Available at: http://onlinelibrary.wiley.com/doi/10.1034/j.16000420.2002.800305.x/pdf. Accessed May 5, 2011 Wejde G, Montan P, Lundstrom M, Stenevi U, Thorburn W. Endophthalmitis following cataract surgery in Sweden: national prospective survey 1999–2001. Acta Ophthalmol Scand 2005; 83:7–10. Available at: http://www3.interscience.wiley.com/ cgi-bin/fulltext/120092610/PDFSTART. Accessed May 5, 2011 €m M, Wejde G, Stenevi U, Thorburn W, Montan P. EnLundstro dophthalmitis after cataract surgery; a nationwide prospective study evaluating incidence in relation to incision type and location. Ophthalmology 2007; 114:866–870 Lundstrom M, Stenevi U, Thorburn W. Gender and cataract surgery in Sweden 1992–1997; a retrospective observational study based on the Swedish National Cataract Register. Acta Ophthalmol Scand 1999; 77:204–208. Available at: http://onlinelibrary.wiley.com/doi/10.1034/j.1600-0420.1999. 770218.x/pdf. Accessed May 5, 2011 €m M. Factors related to the degree of sucKugelberg M, Lundstro cess in achieving target refraction in cataract surgery; Swedish National Cataract Register study. J Cataract Refract Surg 2008; 34:1935–1939 €m M, Brege KG, Flore n I, Stenevi U, Thorburn W. StratLundstro egy to reduce the number of patients perceiving impaired visual function after cataract surgery. J Cataract Refract Surg 2002; 28:971–976 € m M, Stenevi U, Thorburn W. Cataract surgery in the very Lundstro elderly. J Cataract Refract Surg 2000; 26:408–414; erratum, 635 €m M, Stenevi U, Thorburn W. Outcome of cataract surLundstro gery considering the preoperative situation: a study of possible predictors of the functional outcome. Br J Ophthalmol 1991; 83:1272–1276. Available at: http://www.ncbi.nlm.nih.gov/pmc/ articles/PMC1722851/pdf/v083p01272.pdf. Accessed May 5, 2011 €m M, Stenevi U, Thorburn W. Quality of life after firstLundstro and second-eye cataract surgery; five-year data collected by the Swedish National Cataract Register. J Cataract Refract Surg 2001; 27:1553–1559 € m M, Brege KG, Flore n I, Lundh B, Stenevi U, Lundstro Thorburn W. Cataract surgery and quality of life in patients with age related macular degeneration. Br J Ophthalmol 2002; 86:1330–1335. Available at: http://www.ncbi.nlm.nih.gov/pmc/ articles/PMC1771417/pdf/bjo08601330.pdf. Accessed May 5, 2011
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€ m M, Wendel E. Duration of self assessed benefit of cat17. Lundstro aract extraction: a long term study. Br J Ophthalmol 2005; 89:1017–1020. Available at: http://www.ncbi.nlm.nih.gov/pmc/ articles/PMC1772777/pdf/bjo08901017.pdf. Accessed May 5, 2011 €m M, Behndig A, Kugelberg M, Montan P, Stenevi U, 18. Lundstro Pesudovs K. The outcome of cataract surgery measured with the Catquest-9SF. Acta Ophthalmol (Oxf) 2009; Dec 21. [Epub ahead of print] €m M, Pesudovs K. Catquest-9SF patient outcomes 19. Lundstro questionnaire; nine-item short-form Rasch-scaled revision of the Catquest questionnaire. J Cataract Refract Surg 2009; 35:504–513 20. Barry P, Seal DV, Gettinby G, Lees F, Peterson M, Revie CW; for the ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery; preliminary report of principal results from a European multicenter study. J Cataract Refract Surg 2006; 32:407–410 21. Seal DV, Barry P, Gettinby G, Lees F, Peterson M, Revie CW, Wilhelmus KR; for the ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery; case for a European multicenter study. J Cataract Refract Surg 2006; 32:396–406 €m M, Albrecht S, Ha˚kansson I, Lorefors R, Ohlsson S, 22. Lundstro Polland W, Schmid A, Svensson G, Wendel E. NIKE: a new clinical tool for establishing levels of indications for cataract surgery. Acta Ophthalmol Scand 2006; 84:495–501. Available at: http:// onlinelibrary.wiley.com/doi/10.1111/j.1600-0420.2006.00707. x/pdf. Accessed May 5, 2011 n D, Lunsdtro €m M, Behndig A, Stenevi U, Lydahl E, 23. Arze Montan P. Capsule complication during cataract surgery: case-control study of preoperative and intraoperative risk factors; Swedish Capsule Rupture Study Group report 2. J Cataract Refract Surg 2009; 35:1688–1693 24. Jakobsson G, Montan P, Zetterberg M, Stenevi U, Behndig A, €m M. Capsule complication during cataract surgery: Lundstro Retinal detachment after cataract surgery with capsule complication; Swedish Capsule Rupture Study Group report 4. J Cataract Refract Surg 2009; 35:1699–1705 €m M, Montan P, Stenevi U, Behndig A. 25. Johansson B, Lundstro Capsule complication during cataract surgery: long-term outcomes; Swedish Capsule Rupture Study Group report 3. J Cataract Refract Surg 2009; 35:1694–1698 €m M, Behndig A, Montan P, Arze n D, Jakobsson G, 26. Lundstro Johansson B, Thorburn W, Stenevi U. Capsule complication during cataract surgery: background, study design, and required additional care: Swedish Capsule Rupture Study Group report 1. J Cataract Refract Surg 2009; 35:1679–1687; e1
OTHER CITED MATERIAL A. Swedish National Cataract Register (NCR), Karlskrona, Sweden, 2002. Available at: http://www.cataractreg.com. Accessed May 4, 2011
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First author: Anders Behndig, MD, PhD Department of Clinical Sciences/ Ophthalmology, Umeå University, Umeå, Sweden
One million cataract surgeries: Swedish National Cataract Register 1992–2009 Anders Behndig, MD, PhD, Per Montan, MD, PhD, Ulf Stenevi, MD, PhD, Maria Kugelberg, MD, PhD, Mats Lundstr€ om, MD, PhD
This review summarizes data collected by the Swedish National Cataract Register, which now contains data pertaining to more than a million cataract surgery procedures, representing 95.6% of the surgeries performed in Sweden during 1992 2009. During this period, the rate of cataract surgery rose from 4.47 to 9.00 per 1000 inhabitants. The mean patient age increased until 1999 but has slowly decreased since then. Preoperative visual acuity has risen steadily. The distribution between the sexes was stable until 2000, after which the proportion of women slowly decreased. Registration of subjective benefit has brought new knowledge regarding indications and expectations. An improved questionnaire, Catquest-9SF has been used since 2008. The outcome register generally shows good results from the surgery. Endophthalmitis has decreased from 0.10% to below 0.040%. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2011; 37:1539–1545 Q 2011 ASCRS and ESCRS
The Swedish National Cataract Register (NCR) was founded on January 1, 1992,1 primarily to monitor the effects of a newly initiated national healthcare guarantee. The register and its administrative unit, located in Blekinge Hospital, Karlskrona, Sweden,2,3 is financed by the Swedish Association of Local Authorities and Regions and is administered by a steering committee approved by the Swedish Ophthalmological Society.3 Reporting to the register is now primarily Internet-based via the homepage.A
Submitted: January 24, 2011. Final revision submitted: April 6, 2011. Accepted: May 1, 2011. From the Department of Clinical Sciences/Ophthalmology (Behndig), Umea˚ University Hospital, Umea˚, St. Erik Eye Hospital (Montan, Kugelberg), Karolinska Institutet, Stockholm, Department of Ophthalmology (Stenevi), Sahlgrenska University Hospital, M€ olndal, and EyeNet Sweden (Lundstr€om), Blekinge Hospital, Karlskrona, Sweden. Supported by the Swedish Association of Local Authorities and Regions and the Swedish National Board of Health and Welfare. Corresponding author: Anders Behndig, MD, PhD, Department of Clinical Sciences/Ophthalmology, Umea˚ University, SE-901 87 Umea˚, Sweden. E-mail: [email protected]. Q 2011 ASCRS and ESCRS Published by Elsevier Inc.
During the 18 years of the NCR, roughly 50 clinics have reported to the register with a mean reporting frequency of 95.6% of all cataract procedures performed. The register includes a core register and since 1994, an outcomes register. Since 1995, the patient's subjective benefit from surgery and, indirectly, the indications for surgery have been monitored via the Catquest questionnaire.4 Since 1998, each case of endophthalmitis associated with cataract surgery has also been registered. Since its inception, the NCR has monitored and reported trends and results of cataract surgery in Sweden and complications too uncommon to be assessed by individual clinics, such as unplanned postoperative aphakia5,6 and endophthalmitis.7–9 THE CORE REGISTER The following variables are registered in the core register for all cataract procedures: surgical unit; running number of the procedure; patient's year of birth, county, sex, visual acuity in both eyes; date when the patient was put on the waiting list; date of surgery; previous cataract surgery in the fellow eye; ocular comorbidity in the eye planned for surgery (macular degeneration, glaucoma, diabetic retinopathy, or other); surgical technique; position and material of the intraocular lens (IOL); intraoperative antibiotic prophylaxis; and occurrence of “communication between the anterior chamber and the vitreous.” The use of 0886-3350/$ - see front matter doi:10.1016/j.jcrs.2011.05.021
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specially designed IOLs (aspheric, yellow, or multifocal) and intraoperative difficulties warranting altered surgical techniques have been registered since 2008. COVERAGE OF THE NATIONAL CATARACT REGISTER The frequency of reporting clinics was high even in 1992. From 1992 to 2009, 1 079 087 of 1 128 516 cataract procedures were registered in the NCR, corresponding to 95.6% (Table 1). This means the NCR remains highly representative for Swedish cataract surgery. WAITING TIMES The waiting time for cataract surgery in Sweden increased during the early years of the NCR and reached a maximum in the year 2000, after which it decreased, particularly after 2006. A national guarantee of healthcare was in force between 1992 and 1996, and a similar guarantee was reintroduced in November 2005. Both guarantees state that the patient has the right to surgery within 3 months after the decision to operate is made.
Figure 1. Number of cataract procedures in the register divided by first-eye and second-eye surgeries.
instead of (as earlier) a maximum annual number. According to the World Health Organization definition, the surgery rate was between 8000 and 9000 procedures per 1 million citizens from 2000 to 2009 (Figure 2).
SURGERY VOLUMES The number of surgeries increased substantially during 1992 to 2002 and then leveled off (Figure 1). In 2009, however, about 10 000 more procedures were performed than in 2008. Closer analysis shows that this change occurred in the Stockholm region, where the reimbursement system was altered to include all cataract patients referred to the operating clinics
Table 1. Reporting frequency among participating clinics in the Swedish National Register. Percentage Reported, n (%) Year
R97%
90–96%
75–89%
!75%
Total Clinics, n
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
27 (68) 35 (74) 40 (78) 34 (68) 41 (87) 38 (78) 41 (84) 40 (83) 40 (77) 46 (79) 47 (81) 47 (84) 49 (86) 49 (88) 44 (80) 44 (83) 43 (81) 48 (84)
7 7 6 9 3 8 6 4 9 8 9 7 5 6 8 5 6 6
5 1 2 3 2 1 2 1 1 4 1 2 3 1 2 4 4 3
1 4 3 4 1 2 0 3 2 0 1 0 0 0 1 0 0 0
40 47 51 50 47 49 49 48 52 58 58 56 57 56 55 53 53 57
AGE DISTRIBUTION Figure 3 shows the age distribution for each of the 18 years. The mean age at surgery increased from 75.1 years in 1992 to 76.2 years in 1999, after which it decreased to 74.9 years in 2009. The likely explanations for this are first, the demographic profile of the population, with many people born in the 1940s, and second, the shortened waiting lists, meaning that cataract surgery now more closely reflects the true incidence of cataract in the population. SECOND-EYE SURGERY The proportion of patients having cataract surgery in the second eye increased from 28.5% to 40.4% from 1992 to 2009. In absolute numbers, the surgical
Figure 2. Total number of cataract operations per 1 million citizens in Sweden, 2000–2009.
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below this has continually decreased, from 44% in 1992 to 22% in 2009. The gradual increase in preoperative visual acuity is interpreted as a shift in the indications following improved surgical technique and results.
Figure 3. The total number of procedures in each age group during each year from 1992 to 2009.
volumes increased by 40 000, with roughly equal numbers of first eyes and second eyes (Figure 1). SURGICAL TECHNIQUE Surgical technique and type of IOL were added to the core registry in 1997. The first years of this registration showed the final transition to the phacoemulsification technique and to the use of hydrophobic acrylic IOLs.3
SEX A difference in surgical frequency between the sexes was noted early10 and has largely remained. The proportion of women was around 66% from 1992 to 2000 and gradually decreased to 61% in 2009. There appears to be a relationship between a high age at surgery and the percentage of women operated on, probably explained by differences in life expectancy between the sexes. The mean waiting time for surgery was 2.83 months for women (median, 2 months) and 2.72 months for men (median, 2 months). Surgery was performed within 6 months in 93.4% of the women versus 93.8% of the men. Surgical technique, complications, and results did not differ between the sexes, and ocular comorbidity was equally common in women (32.4%) and men (33.3%). Men were operated on outside their home county slightly more often (4.0% versus 3.2%). Figure 5 shows the parameters for surgical volume, mean age, and sex. Initially, the surgical volumes
VISUAL ACUITY The median visual acuity of the better eye was 0.5 in the early days of the NCR and rose to 0.6 in 1998; the median visual acuity of the eye planned for surgery increased from 0.1 in 1992 to 0.4 in 2009. The proportion of patients seeing 0.1 or less in the eye to be operated on or 0.8 or more in the other eye is shown on an annual basis in Figure 4. A functionally relevant visual acuity is 0.5 in the better eyedthe basic requirement for holding a driver's license in Sweden. The fraction of patients
Figure 4. Development of preoperative visual acuity, 1992 to 2009. The left bar shows the percentage of patients with visual acuity of 0.1 or less in the eye to be operated on; the right bar shows the percentage with a visual acuity 0.8 or more in the other eye. The lines are trend lines.
Figure 5. Number of cataract procedures (white; scale to the right), mean age (gray; scale to the left), and percentage of women having surgery (black; scale to the left), 1992 to 2009.
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increased gradually as more older patients were operated on, but the sex distribution remained constant. After the turn of the century, surgical volumes decreased, along with mean age and percentage of women. THE OUTCOME REGISTER The outcome register, in use since 1995, covers all operations of the participating clinics during the month of March, which corresponds to about 8% of all cases. Analyses show that March matches the rest of the year in terms of patient demographics. The following preoperative variables were registered: running number of the procedure, keratometric values (K values) in diopters (D) (with axes), and planned refraction. Postoperative registration included date of the final visit, visual acuity and refraction in both eyes, K values in the operated eye (with axes), ocular comorbidity in the operated eye, and reasons for loss to follow-up (poor compliance, death). When the data were registered and reported, the final visit occurred within 4 months of the procedure in 97.3% of the cases. Self-assessed visual function was evaluated with the Catquest instrument preoperatively and postoperatively; the final form was completed approximately 3 months after surgery. INDUCED ASTIGMATISM Figure 6 shows the induced astigmatism over the years. This parameter has diminished over time, probably owing to the transition from extracapsular technique via standard incision phacoemulsification to today's small incisions with foldable IOLs. However, one should be aware that deliberate modification of the astigmatism by placement of the incision might have influenced the results in recent years.
Figure 6. Mean induced astigmatism in diopters, assessed with the subtraction method, for the clinics participating in this registration from 1995 to 2009. Each year is represented by a box containing 50% of the values. The dark line is the median value and 95% of the values are within the vertical lines. The rings are outliers.
BIOMETRY PREDICTION ERROR Figure 7 shows the change in biometry prediction error over the years for the 9 clinics that participated in this registration every year since 1995. This variable reflects both the precision of the preoperative biometrical measurement and the surgical technique. Accurate determination of differences below 0.5 D are not possible because of limited measurement precision. Several factors may explain why the planned refraction was not achieved. Female sex, glaucoma, and a low preoperative visual acuity are risk factors for a larger biometry prediction error.11 The error was not smaller in second-eye surgeries than in first-eye surgeries, but the biometry prediction error has generally decreased over the years. From 1999, the refraction of the fellow eye has also been registered because too large a difference may influence visual comfort and lead to difficulties in performing daily tasks.12 Figure 8 shows the difference in refraction between the eye operated on and the fellow eye in patients having second-eye surgery. The median value has decreased from 0.5 to 0.4 D, and the spread of values has also decreased.
SUBJECTIVE (PERCEIVED) BENEFIT FROM SURGERY Results from various projects performed to evaluate the perceived benefit from surgery, measured by Catquest, are summarized below: The benefit from cataract surgery in patients 85 years of age or older without other ocular disease was as good as the benefit in younger patients.13
Figure 7. Biometry prediction error for the 9 clinics participating in the outcomes registration every year from 1995 to 2009. Each year is represented by a box containing 50% of the values. The dark line is the median value, and 95% of the values are within the vertical lines. Rings denote outliers and asterisks denote extreme values.
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Figure 8. Difference in refraction (spherical equivalent, absolute values) between the operated eye and the fellow eye. Only patients having second-eye surgery are included. Each year is represented by a box containing 50% of the values. The dark line is the median value, and 95% of the values are within the vertical lines. Rings denote outliers and asterisks denote extreme values.
The most common reason for no perceived benefit from surgery was ocular comorbidity in the eye having surgery.4,14 Cataract surgery in both eyes gave a significantly better outcome than surgery in 1 eye only.4,14,15 Younger patients who have had surgery in both eyes experienced the greatest improvement.14 Two common causes of perceived worsening at 6 months, compared with preoperatively, were cataract in the fellow eye and anisometropia.4 Patients with simultaneous age-related macular degeneration perceived a significantly improved visual function postoperatively. The strongest predictor for subjective improvement was the level of visual acuity achieved.16 Improvement in self-assessed visual function after cataract surgery was long-term; about 80% of those operated on 7 to 8 years earlier still experienced improved visual function.17 Women assessed their visual problems as more severe preoperatively and postoperatively, but the subjective improvement from surgery was slightly larger in women.18 Overall, cataract patients were significantly helped by surgery. After surgery, their subjective visual disturbance was reduced and their level of activity increased. REVISION OF CATQUEST During 2006, a revision of the Catquest questionnaire was initiated. The original questionnaire, developed from 1993 to 1995, was deemed dated in the face of
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modern demands regarding psychometric qualities and analysis of question constructions (item-response theory). The Catquest registration was temporarily paused in 2007 during the revision, in which both classical test theory and Rasch analysis were used.19 In 2008, the new instrument, Catquest-9SF, was tested by 6 clinics. A good correlation between the preoperative score and the visual acuity of the best eye before surgery (r Z 0.432) was demonstrated. The postoperative score correlated well with the visual acuity of the operated eye (r Z 0.470). The mean preoperative score was 0.35 logits G 1.7 (SD), and the mean postoperative score was 2.33 G 1.62 logits, a statistically significant improvement. The change in score from surgery corresponded to an effect size of 1.17 (improvement/SD). Thus, the good psychometric properties from the revision were confirmed; high precision, good targeting, and high effect size. Worsened self-assessed visual function was reported by 10.1% of the patients. In 2009, 24 clinics provided Catquest-9SF data. Table 2 shows the percentage of patients who perceived fewer restrictions in performing activities of daily life after cataract surgery. ENDOPHTHALMITIS REGISTER A registration of all endophthalmitis cases after cataract surgery was commenced in January 1998, with the participation of all clinics reporting to the NCR. For each suspected postoperative endophthalmitis case, a registration is made, including information about the result of the intraocular culture sample. A final report is made after 3 months, stating the type of prophylaxis used and the final visual acuity of the affected eye. The number of postoperative endophthalmitis cases was lower from 1999 to 2009 than in 1998 (Figure 9).7,8 From the end Table 2. Percentage of patients perceiving less restriction in performing activities of daily life after a cataract extraction.
Year
Percentage Reporting Less Restriction
Questionnaire
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
90.9 90.5 91.3 91.6 90.6 90.3 92.5 90.9 92.6 92.2 92.3 93.3 d 92.8 93.3
Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest Catquest No questionnaire Catquest-9SF Catquest-9SF
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of 1999, the type of prophylaxis used was assessed through enquiries to the participating clinics and, later, this information was included in the core register. Analyses clearly showed that intraocular cefuroxime reduced the frequency of postoperative endophthalmitis.8,9 The postoperative endophthalmitis registrations have led to several positive developments; diagnostic routines have improved and intracameral cefuroxime has been adopted all over the country, resulting in a decreased incidence of postoperative endophthalmitis. The results inspired the European Society of Cataract and Refractive Surgeons to perform a randomized multicenter study to evaluate different prophylaxis modalities. This study confirmed the Swedish experience, and intracameral cefuroxime has since become a suggested European standard.20,21 To further assess risk factors for postoperative endophthalmitis, the Swedish registrations were expanded in 2002 to include incision details, the use of an IOL injector, and posterior capsule rupture.9 The latter was associated with a higher risk for postoperative endophthalmitis, but IOL injectors could not be demonstrated to lower the risk. There was, however, a trend toward a relationship between strictly corneal versus sclerocorneal incisions and temporal versus 12 o'clock incisions and endophthalmitis (1 extra postoperative endophthalmitis case in 6000 procedures).9 CLINICAL IMPROVEMENT PROJECT In 2003, all clinics were invited to participate in a national clinical improvement project, aiming (among other things) to define national indications for cataract extraction (Swedish acronym NIKE). The NIKE instrument is based on the visual acuity of both eyes, a patient enquiry assessing problems in performing daily activities, cataract symptoms, and independent living. After a validation study involving 7 clinics, the instrument was deemed reliable and reproducible. A new NIKE-based variable, indication group, was added to the core register from 2005.22 The NIKE was reevaluated and revised in 2007.
Table 3. Posterior capsule rupture leading to a communication between the anterior and posterior segments, 2002 2009.
Year
Surgeries with Capsule Complication
Total Number of Surgeries
% Capsule Complication
2 121 1 902 1 767 1 594 1 284 1 367 1 216 1 328 12 579
75 770 73 994 75 681 77 591 72 568 72 306 72 443 82 470 602 823
2.8 2.6 2.3 2.1 1.8 1.9 1.7 1.6 2.1
2002 2003 2004 2005 2006 2007 2008 2009 Total period
POSTERIOR CAPSULE RUPTURE Posterior capsule rupture is one of the most significant intraoperative complications in cataract surgery and has been part of the core registration since 2002. Table 3 presents the results of 8 years of registration of posterior capsule rupture, showing a gradually declining incidence. An in-depth retrospective analysis of the causes of capsule rupture and the outcomes in these cases was performed in 10 clinics in 2006, investigating the procedures of 2003. This work resulted in 4 reports.23–26 FINAL REMARKS As an ophthalmic registry, the NCR has no precedent on an international level in coverage and persistence. The overall aim of the registry is to provide healthcare professionals and authorities with information regarding cataract care, patient characteristics, morbidity, and surgical quality and accessibility. The data should serve as benchmarking for further improvement. This 18-year review demonstrates a substantial positive development in Swedish cataract surgery. Complications have declined, and the outcome (visual gain, refractive precision, self-reported patient satisfaction) has improved. Surgery is now being performed in younger and healthier eyes, with a greater improvement potential, which correlates significantly with the improved results. In addition, if eyes with equal levels of preoperative vision are compared over this 18-year period, the results have improved, suggesting that refinement of surgical equipment and devices and improved surgical techniques have been instrumental in this development. REFERENCES
Figure 9. Incidence of confirmed endophthalmitis after cataract surgery in Sweden, 1998 to 2009.
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€ m M, Wendel E. Duration of self assessed benefit of cat17. Lundstro aract extraction: a long term study. Br J Ophthalmol 2005; 89:1017–1020. Available at: http://www.ncbi.nlm.nih.gov/pmc/ articles/PMC1772777/pdf/bjo08901017.pdf. Accessed May 5, 2011 €m M, Behndig A, Kugelberg M, Montan P, Stenevi U, 18. Lundstro Pesudovs K. The outcome of cataract surgery measured with the Catquest-9SF. Acta Ophthalmol (Oxf) 2009; Dec 21. [Epub ahead of print] €m M, Pesudovs K. Catquest-9SF patient outcomes 19. Lundstro questionnaire; nine-item short-form Rasch-scaled revision of the Catquest questionnaire. J Cataract Refract Surg 2009; 35:504–513 20. Barry P, Seal DV, Gettinby G, Lees F, Peterson M, Revie CW; for the ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery; preliminary report of principal results from a European multicenter study. J Cataract Refract Surg 2006; 32:407–410 21. Seal DV, Barry P, Gettinby G, Lees F, Peterson M, Revie CW, Wilhelmus KR; for the ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery; case for a European multicenter study. J Cataract Refract Surg 2006; 32:396–406 €m M, Albrecht S, Ha˚kansson I, Lorefors R, Ohlsson S, 22. Lundstro Polland W, Schmid A, Svensson G, Wendel E. NIKE: a new clinical tool for establishing levels of indications for cataract surgery. Acta Ophthalmol Scand 2006; 84:495–501. Available at: http:// onlinelibrary.wiley.com/doi/10.1111/j.1600-0420.2006.00707. x/pdf. Accessed May 5, 2011 n D, Lunsdtro €m M, Behndig A, Stenevi U, Lydahl E, 23. Arze Montan P. Capsule complication during cataract surgery: case-control study of preoperative and intraoperative risk factors; Swedish Capsule Rupture Study Group report 2. J Cataract Refract Surg 2009; 35:1688–1693 24. Jakobsson G, Montan P, Zetterberg M, Stenevi U, Behndig A, €m M. Capsule complication during cataract surgery: Lundstro Retinal detachment after cataract surgery with capsule complication; Swedish Capsule Rupture Study Group report 4. J Cataract Refract Surg 2009; 35:1699–1705 €m M, Montan P, Stenevi U, Behndig A. 25. Johansson B, Lundstro Capsule complication during cataract surgery: long-term outcomes; Swedish Capsule Rupture Study Group report 3. J Cataract Refract Surg 2009; 35:1694–1698 €m M, Behndig A, Montan P, Arze n D, Jakobsson G, 26. Lundstro Johansson B, Thorburn W, Stenevi U. Capsule complication during cataract surgery: background, study design, and required additional care: Swedish Capsule Rupture Study Group report 1. J Cataract Refract Surg 2009; 35:1679–1687; e1
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First author: Anders Behndig, MD, PhD Department of Clinical Sciences/ Ophthalmology, Umeå University, Umeå, Sweden