Abstract
PURPOSE
To investigate the prevalence and visual acuity (VA) outcomes of cataract surgery in a low- to middle-income population in São Paulo, Brazil.
DESIGN
Population-based, cross-sectional study.
METHODS
Cluster sampling was used in randomly selecting those ≥50 years old for VA measurement, refraction, and ocular examination. Participants were queried as to the year and type of facility for previous cataract surgery. Surgical procedure and evidence of surgical complications were noted. Main outcome measures were presenting and best-corrected vision, and the principal cause for eyes presenting with VA ≤20/40.
RESULTS
A total of 4,224 eligible persons were enumerated and 3,678 (87.1%) were examined. The prevalence of cataract surgery was 6.28% (95% confidence interval [CI], 5.29% to 7.27%). Surgical coverage for presenting VA <20/63 in both eyes because of cataract was 61.4%. Unoperated cataract impairment/blindness was associated with older age and lack of schooling. Among the 352 cataract-operated eyes, 41.2% presented with VA >20/40, 28.1% with VA 20/40 to 20/63, 14.2% with VA <20/63 to 20/200, and 16.5% with VA <20/200. With best correction, the percentages were 61.9%, 17.6%, 8.2%, and 12.2%. Intraocular lenses were found in 90.6% of cataract-operated eyes; half appeared to have been operated by phacoemulsification. Refractive error and retinal disorders were the main cause of vision impairment/blindness in operated eyes.
CONCLUSIONS
Cataract surgery has increased in São Paulo, but many remain visually impaired/blind because of cataract. Refractive error and other causes of impairment are common in cataract-operated eyes. Emphasis on the quality of VA outcomes and sustained government subsidy to provide access to affordable modern cataract surgery are needed.
Cataract blindness is recognized as a public health issue in almost all less-developed countries, necessitating an increase in the number of cataract surgeries worldwide. In response, actions to improve access to modern cataract surgery were implemented in Brazil in 1999 through a national program for elective surgeries.1 With an increase in manpower, equipment, intraocular lenses (IOL), and other supplies, free-of-charge surgery became more readily available in public hospitals. The result has been a substantial increase in the annual rate of cataract surgery throughout Brazil: from approximately 600 per million population (100,000 surgeries) in the years immediately prior to 1998, to 920 (153,000) in 1999, 1,345 (228,200) in 2000, 1,540 (267 000) in 2001, and 1,815 (320,000) in 2002.2 In São Paulo, the most populated and industrialized state in the country, these new actions were particularly effective because of its better-structured public services, including major tertiary ophthalmic resources.
Although cataract surgery has become increasingly accessible in recent years, cataract blindness remains a major public health problem, particularly in the poorest areas of the country.3 Little is known about risk factors associated with visual impairment and blindness because of unoperated cataract or poor visual acuity (VA) outcomes following cataract surgery. The objective of the present study is to describe the prevalence of cataract surgery, surgical coverage among those visually impaired or blind from cataract, risk factors for unoperated cataract, VA outcomes following cataract surgery, and the causes of poor outcomes in cataract-operated eyes. Although important for public health planning, such data are not currently available for Brazil.
The present data come from a recent population-based survey of visual impairment and blindness among adults in 3 low- to middle-income districts in the city of São Paulo (the São Paulo Eye Study).4 The 3 urban districts, with a 2000 census population of 346,170, are fairly representative in socioeconomic terms of the urban population throughout Brazil. (Brazil has a total population of 169,799,170, with 81.2% living in urban areas.) Adults 50 years or older were 13.8% of the population in the 3 study districts, with 44.7% of these male vs 18.4% throughout the urban areas of Brazil, with 44.9% male. Literacy is 89.8% in the 3 districts, compared with 89.7% for urban Brazil. Rates for completion of primary and middle school are 52.6% and 38.3%, respectively, in urban Brazil, compared with 43.4% and 49.3% in the study districts. Household income up to 3 times the minimum wage (approximately US $600/month at the time of data collection) is 49.9% in the 3 study districts vs 50.5% for the urban areas of Brazil.5
METHODS
THE STUDY POPULATION WAS SELECTED THROUGH CLUSter sampling based on geographically defined census sectors. Those ≥50 years of age were identified through a door-to-door enumeration and asked to come to an examination site for ophthalmic assessment. Written informed consent was obtained at the examination site, followed by VA measurements, refraction, and a basic eye examination.4 The examination protocol is similar to the one used in earlier studies in Nepal, India, and China.6–12
Ophthalmic technologists measured presenting distance visual acuity (PDVA), with spectacles if the participant presented with them, using retro-illuminated logarithm of the minimum angle of resolution tumbling E charts. (During the enumeration process participants were asked about spectacle wear and advised to bring their glasses to the eye exam.) Those with PDVA ≤20/40 were autorefracted and best-corrected visual acuity (BCVA) was determined. Cataract-operated persons were queried as to the year of surgery and type of surgical facility for each operated eye, and whether the surgery resulted in unreimbursed out-of-pocket payments. Slit-lamp examination of the anterior segment, lens, and anterior vitreous was performed by an experienced ophthalmologist. Intraocular pressure (IOP) measurement by applanation tonometry was also performed. Pupils of eyes with BCVA ≤20/40 were dilated for fundus examination. The type of cataract surgery (based on wound size and placement, and the presence of sutures) and posterior capsule status were noted in the examination of cataract-operated eyes. A principal cause of visual impairment/blindness was assigned by the examining ophthalmologist using a 14-item list for eyes with PDVA ≤20/40. Refractive error was assigned as the cause for eyes improving to >20/40 with best correction.
Further details regarding the study area, the enumeration of subjects, VA measurements, and the eye examination are available in an earlier article.4
Visual acuity measurements were categorized as: normal vision, >20/40; near-normal vision (mild visual impairment), 20/40 to 20/63; visual impairment, <20/63 to 20/200; moderate blindness, <20/200 to 20/400; and severe blindness, <20/400. The total burden of cataract-related visual impairment/blindness was calculated as the sum of the number of unoperated bilaterally impaired/blind persons, attributable to cataract in one or both eyes, plus the number of persons already operated and presumed to have been bilaterally impaired/blind when first operated on for cataract. Because preoperative vision status was not available, already-operated persons were presumed to have been bilaterally impaired/blind at the time of initial cataract surgery if both eyes were operated on, or if only 1 eye was operated on and the unoperated fellow eye was visually impaired/blind. Surgical coverage among cataract-impaired/blind persons was calculated as the ratio of the already-operated visually impaired/blind to the unoperated visually impaired/blind plus the already-operated visually impaired/blind (ie, the already-operated visually impaired/blind divided by the total cataract impairment/blindness burden). To the extent that not all cataract-operated eyes were impaired/blind when operated on, as presumed, the actual surgical coverage rate is somewhat less than that calculated.
The association of age, gender, and schooling with already-operated cataract, unoperated cataract, total cataract burden, and surgical coverage was investigated with multiple logistic regression. The association of calendar year of surgery, type of surgical facility, surgical procedure, age, gender, and schooling with both PDVA and BCVA in cataract operated eyes was also investigated.
Statistical analyses were performed using Stata/SE Statistical Software, Release 8.0, 2003 (Stata Corp, College Station, Texas, USA). Confidence intervals (CI) for prevalence estimates and regression odds ratios (OR) were calculated taking cluster sampling design effects into account. P values ≤.05 were considered statistically significant.
RESULTS
OVER AN 18-MONTH PERIOD, BETWEEN JULY 31, 2004 AND December 3, 2005, 4,224 persons ≥50 years of age were enumerated and 3,678 (87.1%) were examined. Two hundred and thirty-one persons (357 eyes) had been operated on for cataract, representing a cataract surgery prevalence of 6.28% (95% CI, 5.29% to 7.27%). Among the 319 eyes with an IOL, 161 had phacoemulsification, 157 had extracapsular cataract extraction (ECCE), and 1 had intracapsular cataract extraction (ICCE) with an anterior chamber IOL (Table 1). There were 37 aphakic eyes: 23 operated with ECCE, 13 with ICCE, and 1 with phacoemulsification. In 1 eye, it was not possible to ascertain the surgical procedure.
TABLE 1.
Number of Cataract-Operated Eyes by Surgical Procedure and Year of Surgery (the São Paulo Eye Study)
| Year of Surgery
|
||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Procedure | ≤1995 | 1996 | 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | All |
| ICCE | 12 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 13 |
| ECCE | 18 | 0 | 0 | 1 | 2 | 1 | 0 | 0 | 1 | 0 | 0 | 23 |
| ECCE-IOL | 39 | 5 | 11 | 9 | 10 | 11 | 21 | 18 | 20 | 9 | 4 | 157 |
| PHACO-IOL | 10 | 0 | 6 | 0 | 14 | 19 | 28 | 25 | 18 | 34 | 7 | 161 |
| Other/Undetermineda | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 3 |
| All | 79 | 5 | 17 | 10 | 26 | 33 | 49 | 44 | 40 | 43 | 11 | 357 |
ECCE = extracapsular cataract extraction; ECCE-IOL = extracapsular cataract extraction with intraocular lens implantation; ICCE = intracapsular cataract extraction; PHACO-IOL = phacoemulsification with intraocular lens implantation.
Includes one ICCE-operated eye with an anterior chamber IOL, one phacoemulsification-operated eye without an IOL, and 1 eye in which it was not possible to ascertain the surgical procedure.
The calendar year of surgery for the 357 operated eyes ranged from 2005 (the last year of the survey) to more than 4 decades earlier. As shown in Table 1, the number of cataract surgery procedures began to increase in 1999, coinciding with the introduction of the government’s cataract surgery initiative. Because examinations were carried out beginning in July 2004 (and continuing through December 2005), the relatively small number of procedures reported for 2005 is as expected. It is also possible that the discontinuation of the government’s initiative in May 2005 may have contributed to this decrease in the number of procedures for 2005.
Two-thirds of the surgeries were carried out in public health insurance system (SUS) facilities, with the remaining one-third in private hospitals and clinics or private insurance system facilities (Table 2). One-fourth of the patients experienced unreimbursed out-of-pocket payments for the cataract surgery, the IOL, or both.
TABLE 2.
Cataract-Operated Eyes by Type of Facility and Payment Status (the São Paulo Eye Study)
| Out-of-Pocket Paymenta
|
|||||
|---|---|---|---|---|---|
| Facility Type | None | Surgery | IOL | Both | Total |
| Public insurance system | 213 (93.4) | 4 (1.8) | 11 (4.8) | 0 (0.0) | 228 (64.4) |
| Private insurance system | 44 (50.0) | 1 (1.1) | 39 (44.3) | 4 (4.5) | 88 (24.9) |
| Private hospital/clinic | 11 (28.9) | 2 (5.3) | 7 (18.4) | 18 (47.4) | 38 (10.7) |
| Total | 268 (75.7) | 7 (2.0) | 57 (16.1) | 22 (6.2) | 354 (100.0) |
IOL = intraocular lens.
Data are given as number (%) of cataract-operated eyes; 3 operated eyes are not included because of missing information.
Lens status and spectacle usage (as noted at the exam site) among the 231 cataract-operated persons is shown in Table 3. Two hundred and six (89.2%) were pseudophakic in one or both eyes, including 4 who were pseudophakic in one eye and aphakic in the fellow eye. Twenty-five (10.8%) were aphakic in one or both eyes, including one with undetermined lens status, and 9 (36.0%) were without glasses for distance correction.
TABLE 3.
Bilateral Lens Status and Spectacle Usage for Cataract-Operated Persons (the São Paulo Eye Study)
| Spectacle Usage
|
|||||
|---|---|---|---|---|---|
| Lens Status | None | Distance Lenses | Bifocal/Multifocal | Reading Lenses | Total |
| Aphakic, unoperated | 5 (33.3) | 4 (26.7) | 4 (26.7) | 2 (13.3) | 15 (6.5) |
| Pseudophakic, unoperated | 42 (47.2) | 4 (4.5) | 37 (41.6) | 6 (6.7) | 89 (38.5) |
| Aphakic, pseudophakic | 0 (0.0) | 0 (0.0) | 3 (75.0) | 1 (25.0) | 4 (1.7) |
| Aphakic, aphakic | 1 (11.1) | 5 (55.6) | 3 (33.3) | 0 (0.0) | 9 (3.9) |
| Pseudophakic, pseudophakic | 37 (32.7) | 13 (11.5) | 58 (51.3) | 5 (4.4) | 113 (48.9) |
| Undetermined, unoperated | 1 (100.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 1 (0.4) |
| All | 86 (37.2) | 26 (11.3) | 105 (45.5) | 14 (6.1) | 231 (100.0) |
Visual acuity could not be measured in 3 of the 231 cataract-operated individuals (36 of the 3,678 examined) because of cognitive impairment. Of the 228 with VA measurements, 191 (83.8%) were presumed to have been bilaterally visually impaired/blind at the time of surgery, as defined in the METHODS section (Table 4). An additional 120 persons were bilaterally impaired/blind because of unoperated cataract. Accordingly, a total of 311 of the 3,642 study participants with VA measurements (8.54%) were affected by bilateral cataract visual impairment or blindness. Surgical coverage in this cohort (PDVA <20/63 in both eyes) was 61.4%. (Surgical coverage within the blind cohort [PDVA <20/200] was 89.7%.)
TABLE 4.
Cataract Surgery and Presenting Visual Impairment/Blindness Because of Cataract by Age, Gender, and Schooling (the São Paulo Eye Study)
| Number Examineda | Cataract-Operated
|
Unoperated Cataract Visually Impaired/Blind
|
Total Cataract Visual Impairment/Blindness Burden
|
Surgical Coverage
|
||||||
|---|---|---|---|---|---|---|---|---|---|---|
| All Operated
|
Presumed Visually Impaired/Blind
|
|||||||||
| No. | Prevalenceb | No. | Prevalenceb | No. | Prevalenceb | No. | Prevalenceb | % | ||
| Age (years) | ||||||||||
| 50 to 59 | 1739 | 27 | 1.55 | 19 | 1.09 | 9 | 0.52 | 28 | 1.61 | 67.9 |
| 60 to 69 | 1124 | 67 | 5.96 | 52 | 4.63 | 27 | 2.40 | 79 | 7.03 | 65.8 |
| ≥70 | 779 | 134 | 17.2 | 120 | 15.4 | 84 | 10.8 | 204 | 26.2 | 58.8 |
| Gender | ||||||||||
| Male | 1527 | 91 | 5.96 | 73 | 4.78 | 37 | 2.42 | 110 | 7.20 | 66.4 |
| Female | 2115 | 137 | 6.48 | 118 | 5.58 | 83 | 3.92 | 201 | 9.50 | 58.7 |
| Schooling | ||||||||||
| None | 560 | 58 | 10.4 | 54 | 9.64 | 54 | 9.64 | 108 | 19.3 | 50.0 |
| Primary | 1983 | 121 | 6.10 | 97 | 4.89 | 50 | 2.52 | 147 | 7.41 | 66.0 |
| ≥Secondary | 942 | 36 | 3.82 | 28 | 2.97 | 7 | 0.74 | 35 | 3.72 | 80.0 |
| Unknown | 157 | 13 | 8.28 | 12 | 7.64 | 9 | 5.73 | 21 | 13.4 | 57.1 |
| All | 3642 | 228 | 6.26 | 191 | 5.24 | 120 | 3.29 | 311 | 8.54 | 61.4 |
Not including 36 persons with missing visual acuity measurements because of cognitive impairment associated with stroke or other disability. Three of these persons were cataract operated: two were women with pseudophakia in both eyes, aged 74 and 76 with some schooling; one was a man with aphakia in 1 eye, aged 79 with no schooling.
Crude prevalence per 100 examined participants.
In multiple logistic regression modeling, already operated visual impairment/blindness was associated with older age (Table 5). Unoperated cataract impairment/blindness was associated with older age and lack of formal schooling. Age and schooling were also significant for the total burden of cataract visual impairment/blindness. Schooling at the secondary level or higher was significant for surgical coverage.
TABLE 5.
Relation of Age, Gender, and Schooling to Cataract Surgery and Cataract Visual Impairment/Blindness (the São Paulo Eye Study)
| Cataract-Operated Impaired/Blind | Unoperated Cataract Impaired/Blind | Total Cataract Visual Impairment/Blindness Burden | Surgical Coverage | |
|---|---|---|---|---|
| Age (years) | ||||
| 50 to 59 | Reference | Reference | Reference | Reference |
| 60 to 69 | 4.57 (2.55 to 8.22)a | 4.07 (1.86 to 8.87)a | 4.48 (2.82 to 7.11)a | 1.18 (0.43 to 3.21) |
| ≥70 | 17.5 (9.94 to 30.7)a | 15.9 (8.79 to 28.7)a | 19.3 (12.9 to 28.8)a | 1.12 (0.46 to 2.73) |
| Gender | ||||
| Male | Reference | Reference | Reference | Reference |
| Female | 1.14 (0.87 to 1.50) | 1.37 (0.93 to 2.04) | 1.25 (0.99 to 1.58) | 0.91 (0.56 to 1.48) |
| Schooling | ||||
| None | Reference | Reference | Reference | Reference |
| Primary | 0.86 (0.52 to 1.63) | 0.43 (0.24 to 0.77)b | 0.60 (0.43 to 0.83)b | 1.90 (0.81 to 4.46) |
| ≥Secondary | 0.94 (0.54 to 1.63) | 0.22 (0.09 to 0.59)b | 0.53 (0.35 to 0.81)b | 3.96 (1.22 to 12.8)b |
Data are given as adjusted odds ratios (95% confidence interval) obtained by multiple logistic regression.
< .001.
≤ .05.
PDVA and BCVA for cataract-operated eyes are shown in Table 6. PDVA ≥20/63 was found in 244 eyes (69.3%), and 280 eyes (79.5%) with BCVA ≥20/63. Fifty-eight eyes (16.5%) presented blind (PDVA <20/200). Forty-three (12.2%) remained blind with best correction.
TABLE 6.
Presenting and Best-Corrected Visual Acuity Outcomes in Cataract-Operated Eyes (the São Paulo Eye Study)
| Best-Corrected Visual Acuity
|
||||||
|---|---|---|---|---|---|---|
| >20/40
|
20/40 to 20/63
|
<20/63 to 20/200
|
<20/200 to 20/400
|
<20/400
|
All
|
|
| Presenting Visual Acuity | No. (%) | No. (%) | No. (%) | No. (%) | No. (%) | No. (%) |
| >20/40 | 145 (100.0) | 145 (41.2) | ||||
| 20/40 to 20/63 | 55 (55.6) | 44 (44.4) | 99 (28.1) | |||
| <20/63 to 20/200 | 13 (26.0) | 15 (30.0) | 22 (44.0) | 50 (14.2) | ||
| <20/200 to 20/400 | 2 (9.1) | 0 (0.0) | 3 (13.6) | 17 (77.3) | 22 (6.3) | |
| <20/400 | 3 (8.3) | 3 (8.3) | 4 (11.1) | 1 (2.8) | 25 (69.4) | 36 (10.2) |
| All | 218 (61.9) | 62 (17.6) | 29 (8.2) | 18 (5.1) | 25 (7.1) | 352 (100.0) |
Table 7 identifies principal causes for the 207 cataract-operated eyes with PDVA ≤20/40. Refractive error was the most common cause in eyes with VA 20/40 to 20/63, and retinal disorders were the main cause in eyes with acuity <20/63.
TABLE 7.
Causes of Vision Impairment/Blindness in Cataract-Operated Eyes by Presenting Visual Acuity (the São Paulo Eye Study)
| Presenting Visual Acuity
|
|||||
|---|---|---|---|---|---|
| 20/40 to 20/63
|
<20/63 to 20/200
|
<20/200 to 20/400
|
<20/400
|
All
|
|
| Principal Cause | No. (%) | No. (%) | No. (%) | No. (%) | No. (%) |
| Refractive errora | 55 (55.6) | 13 (26.0) | 2 (9.1) | 3 (8.3) | 73 (35.3) |
| Other retinal disordersb | 6 (6.1) | 15 (30.0) | 4 (18.2) | 12 (33.3) | 37 (17.9) |
| Macular degeneration | 11 (11.1) | 5 (10.0) | 8 (36.4) | 0 (0.0) | 24 (11.6) |
| PCO | 8 (8.1) | 5 (10.0) | 0 (0.0) | 0 (0.0) | 13 (6.3) |
| Diabetic retinopathy | 3 (3.0) | 5 (10.0) | 2 (9.1) | 2 (5.6) | 12 (5.8) |
| Corneal opacity/scar | 1 (1.0) | 0 (0.0) | 2 (9.1) | 8 (22.2) | 11 (5.3) |
| Optic atrophy | 0 (0.0) | 4 (8.0) | 0 (0.0) | 2 (5.6) | 6 (2.9) |
| Amblyopia | 3 (3.0) | 0 (0.0) | 2 (9.1) | 0 (0.0) | 5 (2.4) |
| Glaucoma | 1 (1.0) | 0 (0.0) | 0 (0.0) | 4 (11.1) | 5 (2.4) |
| Retinal detachment | 0 (0.0) | 0 (0.0) | 0 (0.0) | 2 (5.6) | 2 (1.0) |
| Other causes | 4 (4.0) | 2 (4.0) | 1 (4.5) | 1 (2.8) | 8 (3.9) |
| Undetermined | 7 (7.1) | 1 (2.0) | 1 (4.5) | 2 (5.6) | 11 (5.3) |
| All | 99 (47.8) | 50 (24.2) | 22 (10.6) | 36 (17.4) | 207 (100.0) |
PCO = posterior capsule opacification.
Includes 2 aphakic cases without corrective spectacles.
Includes 25 eyes with maculopathy, 4 with high myopia, 3 with vitreous opacity, 2 with chorioretinitis, 2 with retinitis pigmentosa, and 1 unspecified.
Table 8 shows the percentage of cataract-operated eyes with PDVA and BCVA ≥20/63 by age category, gender, schooling, calendar year of surgery, type of surgical facility, and surgical procedure. The association of PDVA and BCVA ≥20/63 with these covariates was explored with logistic regression. To maintain independence between eyes, only the 228 first-operated eyes were included in the regression: 129 ICCE/ECCE-operated eyes, including 8 aphakic eyes without spectacles, and 99 phacoemulsification-operated eyes. With presenting vision, phacoemulsification (OR, 2.05; 95% CI, 1.07 to 3.93) was statistically significant, and schooling at the secondary level or above was marginally significant (OR, 2.84; 95% CI, 0.98 to 8.24). With best-corrected vision, schooling at the primary level was significant (OR, 1.69; 95% CI, 1.02 to 2.80) while schooling at the secondary level remained marginally significant (OR, 3.86; 95% CI, 0.93 to 16.0). Phacoemulsification was not significant with best-corrected vision (P = .130).
TABLE 8.
Presenting and Best-Corrected Visual Acuity of Cataract-Operated Eyes by Age, Gender, Schooling, Time Period of Surgery, Type of Facility, and Procedure (the São Paulo Eye Study)
| Number (%) of Eyes | % Presenting Visual Acuity ≥20/63 | % Best-Corrected Visual Acuity ≥20/63 | |
|---|---|---|---|
| Age (years) | |||
| 50 to 59 | 38 (10.8) | 71.1 | 86.8 |
| 60 to 69 | 104 (29.5) | 69.2 | 76.0 |
| ≥70 | 210 (59.7) | 69.0 | 80.0 |
| Gender | |||
| Male | 143 (40.6) | 67.8 | 78.3 |
| Female | 209 (59.4) | 70.3 | 80.4 |
| Schooling | |||
| None | 93 (26.4) | 64.5 | 75.3 |
| Primary | 184 (52.3) | 70.1 | 79.3 |
| ≥Secondary | 55 (15.6) | 74.5 | 83.6 |
| Unknown | 20 (5.7) | 70.0 | 90.0 |
| Time period of surgery | |||
| ≤1995 | 79 (22.4) | 59.5 | 75.9 |
| 1996 to 2000 | 90 (25.6) | 73.3 | 85.6 |
| ≥2001 | 183 (52.0) | 71.6 | 78.1 |
| Type of facility | |||
| Public insurance | 225 (63.9) | 68.4 | 80.0 |
| Private insurance | 124 (35.2) | 71.0 | 79.0 |
| Unknown | 3 (0.9) | 66.7 | 66.7 |
| Procedure | |||
| ICCE/ECCE | 192 (54.5) | 62.0 | 75.5 |
| Phacoemulsification | 160 (45.5) | 78.1 | 84.4 |
| All | 352 (100.0) | 69.3 | 79.5 |
ECCE = extracapsular cataract extraction; ICCE = intracapsular cataract extraction.
DISCUSSION
A MAJOR STRENGTH OF THIS STUDY IS THAT IT WAS conducted in a randomly selected, population-based sample from 3 representative urban districts of São Paulo. The large sample size and objective measurement of VA contributed to the strengths of the study, and the high examination response rate minimized bias relating to participant self-selection. Although the findings are primarily applicable to low- to middle-income adults in São Paulo, they are also likely to have relevance to urban populations throughout Brazil.
Although we did not seek access to clinical charts to validate the accuracy of the calendar year of surgery as reported by participants, it is apparent that the volume of cataract surgery was influenced by the new government initiative in 1999 expanding subsidized access to modern cataract surgery: In the subsequent 2 years, surgical volume appears to have tripled from pre-1999 levels. This increase in volume was a major factor in achieving a high surgical coverage rate among the cataract-impaired/blind. It should be recognized, however, that because mortality disproportionately affected the earlier years, the increase in surgical volume was, in reality, somewhat less than that suggested by Table 1. Further, because examinations began in July 2004 and continued through December 2005, the number of cataract-operated eyes reported for 2005, and even 2004, are an incomplete account of the number of cataract surgeries actually performed during these latter years. Thus, the data shown in Table 1 are only an approximation of the temporal influence of the 1999 government initiative, and provide little insight into whether the discontinuation of the initiative in May 2005 led to a decrease in the volume of cataract surgery.
The surgical coverage rate (89.7%) among the bilaterally blind cohort (PDVA <20/200) was higher than that found in Rapid Assessment of Cataract Surgery Services (RACSS) surveys in Paraguay, Peru, and Argentina.13–15 Eye care delivery in urban vs rural settings is likely to account for some of the differential—as is the fact that these countries did not have national programs to improve access to cataract surgery prior to the implementation of the RACSS surveys. Although the surgical coverage calculations were based on similar assumptions, the RACSS protocol uses simplified VA testing and a cursory ophthalmic examination; thus, any direct comparisons with our findings should be viewed with some skepticism.
The prevalence of PDVA <20/63 among cataract-operated eyes was 30.7%. The difference between this and the 20.5% rate based on BCVA indicates that normal vision can be restored in an additional 10% of cataract-operated eyes with simple refractive correction. With PDVA ≤20/40, the differential widens to 20% (58.8% to 38.1%). These differences between PDVA and BCVA underscore the importance of ensuring that the implanted IOL is of appropriate power and of minimizing postoperative astigmatism.
The finding of 69.3% cataract-operated eyes having PDVA ≥20/63 is higher than that reported with the same clinical protocol in Shunyi County (China),7 Rajasthan (India),9 Sivaganga (India),11 and Tirunelveli (India).10 A large percentage of eyes with uncorrected aphakia and surgical complications is a major consideration in explaining the relatively poor vision outcomes in these other studies. The RACSS studies in Buenos Aires (Argentina)15 and Paraguay13 reported comparably good PDVA outcomes, while the study in semi-rural Peru14 reported considerably worse outcomes.
Despite the enormous cost and burden of cataract surgery in developed country settings such as the United States,16 the Los Angeles Latino Eye Study (LALES) is the only major population-based study in that country to report on postoperative visual impairment and causes in cataract-operated individuals.17 Their finding that 74.7% of cataract-operated eyes presented with VA ≥20/63, and 81.3% with best-corrected vision, is only marginally higher than the 69.3% and 79.5%, respectively, in São Paulo. For VA ≥20/40, the respective percentages are 51.9% and 67.8% in LALES, compared with 41.2% and 61.9% in São Paulo. In a population-based study in Victoria, Australia, 85% of cataract-operated eyes were reported to have had BCVA ≥20/40.18 Similarly, a national survey of over 100 United Kingdom hospitals reported BCVA ≥20/40, at final refraction within 3 months of discharge, in 92% of patients without ocular comorbidity and in 77% of those with coexisting eye disease.19
Aside from refractive error (35.3%), the most common causes of PDVA ≤20/40 in cataract-operated eyes were maculopathy and other retinal disorders (17.9%), age-related macular degeneration (AMD) (11.6%), posterior capsule opacification (PCO) (6.3%), diabetic retinopathy (5.8%), and corneal opacity/scarring (5.3%). The primary causes of PDVA ≤20/40 among cataract-operated eyes in the LALES Study were comparable: refractive error was the most common cause (33.0%), followed by AMD (13.3%), diabetic retinopathy (10.8%), corneal opacity (7.9%), PCO (7.4%), and glaucoma (5.4%).18 Because visual field assessment was not performed and specific observation of the optic nerve was not mandated, glaucoma as a cause of visual impairment is likely to have been underestimated in our study. It is important to note that because some of these pathologies may have been coexisting at the time of cataract surgery, and not always identifiable in cases with dense lens opacity, a rigorous preoperative examination to determine whether the patient is visually impaired/blind from cataract, rather than impaired/blind with cataract, is needed to help screen out cases in which cataract surgery is unlikely to improve vision.
Together, uncorrected refractive error and PCO accounted for over 40% of cataract-operated eyes with PDVA ≤20/40. Although uncorrected and undercorrected ammetropia are easily treated with spectacles, many may go without refractive correction because of factors such as access to eye care services, cost of glasses, and an unperceived need for sharp vision. Similarly, PCO can be readily treated with a yttrium-aluminum-garnet-laser capsulotomy, but patients attributing their loss of vision to a failure of cataract surgery may hesitate to seek the necessary follow-up examination. Thus, for the vision-restoring potential of cataract surgery to be fully realized, the importance of periodic, postoperative follow-up care must be stressed to all patients.
Although it is expected that an emphasis on increasing cataract surgical volume will continue in Brazil, equal attention must be given to ensuring surgical quality and postsurgical monitoring. The lack of appropriate refractive spectacles for a large proportion of cataract patients is clearly a problem, as is the need for greater attention in ensuring that the IOL implant is of appropriate power. Awareness campaigns to reduce barriers to cataract surgery, adequate postsurgical follow-up, and monitoring of VA outcomes are neglected components in the management of this prevalent eye disease.
Acknowledgments
THIS STUDY WAS SUPPORTED BY THE WORLD HEALTH ORGANIZATION (WHO), GENEVA, SWITZERLAND (UNDER THE National Institutes of Health, Bethesda, Maryland contract no. N01-EY-2103); Fundação de Amparo à Pesquisa do Estado de São Paulo-FAPESP, São Paulo, SP, Brazil Grant no. 04/06670-9 (Dr Salomão); Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPq Brasília, DF, Brazil research fellowship (Drs Salomão, Berezovsky, and Belfort); Fundo de Apoio aos Docentes e Alunos da UNIFESP – FADA, São Paulo, SP, Brazil research fellowship (Drs Salomão, Berezovsky, and Belfort). Involved in design of study (S.R.S., A.B., A.A.-F., G.P.P., R.B.J., L.B.E.); conduct of study (S.R.S., A.B., A.A.-F.); collection of data (S.R.S., F.S.S., A.B., A.A.-F., M.H.M., S.S.W., A.V.C.); management (S.R.S., A.B., A.A.-F., L.B.E.), analysis (S.R.S., F.S.S., A.B., A.A.-F., M.H.M., S.S.W., A.V.C., G.P.P., R.B.J., L.B.E.), and interpretation of data (S.R.S., F.S.S., A.B., A.A.-F., M.H.M., S.S.W., A.V.C., G.P.P., R.B.J., L.B.E.); preparation, review, or approval of the manuscript (S.R.S., F.S.S., A.B., A.A.-F., M.H.M., S.S.W., A.V.C., G.P.P., R.B.J., L.B.E.). The study adhered to the Declaration of Helsinki and was cleared by the WHO Secretariat Committee on Research involving Human Studies and the Committee on Ethics in Research of the Federal University of São Paulo (UNIFESP).
The authors are grateful to ophthalmic technologists/orthoptists Celina Tamaki-Castro, Josenilson M. Pereira, Luana M. Cinoto, M. Valeria Ferrari, Meiry A. Furusato, Nívea N. Cavascan, and Paula Y. Sacai, Vision Institute, Department of Ophthalmology, Federal University of São Paulo (UNIFESP), São Paulo, Brazil, for assistance in clinical examinations and to Rafael W. Cinoto for assistance in data management and statistical analysis.
Biographies
Biosketch
Arnaud Araújo-Filho, MD, received his medical degree from ABC School of Medicine, Brazil. He completed his residency in Ophthalmology and fellowship in Corneal, External Diseases, and Cataract at Federal University of São Paulo–UNIFESP, Brazil. Dr Araújo-Filho was actively involved in the creation of the Cataract Institute at UNIFESP. His research interests include cataract and refractive surgery and ocular epidemiology with a particular emphasis in prevention of cataract blindness and outcomes of cataract surgery.
Biosketch
Solange R. Salomão, PhD, is currently Coordinator of the Ophthalmic Epidemiology Center and an Associate Professor at the Department of Ophthalmology, Federal University of São Paulo–UNIFESP, São Paulo, Brazil. She graduated in Orthoptics and completed her PhD in Psychobiology at UNIFESP with post-doctoral fellowship at the Retina Foundation of the Southwest, Dallas, Texas. Dr Salomão’s area of research interest are ocular epidemiology, visual electrophysiology, normal and abnormal visual development and Leber’s hereditary optic neuropathy.
Footnotes
The authors indicate no financial conflict of interest.
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