Cataract surgery complications as a cause of visual impairment in a population aged 50 and over

The purpose of this study was to measure the extent to which complications relating to cataract surgery are a cause of visual impairment in a population aged 50 and over from the city of Campinas, São Paulo State, Brazil. An assessment of cataract surgery services was conducted using random cluster sampling, with the sample composed of 60 clusters of 40 people aged 50 years or older. Of the selected sample of 2,400 subjects, 92.67% were examined. Of these 2,224 examined subjects, 75 (3.37%) presented bilateral visual impairment and 164 unilateral, while a total of 314 (7.06%) eyes presented visual impairment. 352 eyes had undergone cataract surgery. The causes of visual impairment after surgery were concurrent eye disease (56%), surgical complications (28.8%) and refractive errors (15.2%). Cataract surgery complications represented the 5th most important cause of visual impairment. The other main causes were cataract, posterior segment disorders, diabetic retinopathy and glaucoma. These results suggest cataract surgery complications are a major cause of visual impairment in this population. Their prevention and treatment must be part of public health care policies. Blindness; Cataract; Cataract Extraction; Visual Acuity Introduction According to recent studies, age-related cataract is responsible for 48 per cent of blindness worldwide, representing around 18 million people. Although cataracts can be surgically removed, in many countries surgical services are inadequate, and cataract remains the leading cause of visual impairment. As people live longer, the number of people with cataract is growing. Cataract is also an important cause of low vision in both developed and developing countries. Even where surgical services are available, low vision associated with cataract may still be prevalent as a result of the long period spent waiting for operations and barriers to surgical uptake, such as cost, lack of information, and transportation problems 1. The most important causes of adult visual impairment in Brazil include cataract, glaucoma, retinal diseases and non-corrected refractive errors. Cataract accounts for between 40 and 50 per cent of the cases despite the many efforts that have been made over the past five years 2. Although it is widely recognized that cataract extraction and intraocular lens implantation is highly effective and successful, complications due to cataract surgery can result in significant visual impairment as well as additional health care costs 3. Other causes of poor outcome may be concomitant pathology or uncorrected refractive error 4. Cad. Saúde Pública, Rio de Janeiro, 24(10):2440-2444, out, 2008 2440 ARTIGO ARTICLE


Introduction
According to recent studies, age-related cataract is responsible for 48 per cent of blindness worldwide, representing around 18 million people.Although cataracts can be surgically removed, in many countries surgical services are inadequate, and cataract remains the leading cause of visual impairment.As people live longer, the number of people with cataract is growing.Cataract is also an important cause of low vision in both developed and developing countries.Even where surgical services are available, low vision associated with cataract may still be prevalent as a result of the long period spent waiting for operations and barriers to surgical uptake, such as cost, lack of information, and transportation problems 1 .
The most important causes of adult visual impairment in Brazil include cataract, glaucoma, retinal diseases and non-corrected refractive errors.Cataract accounts for between 40 and 50 per cent of the cases despite the many efforts that have been made over the past five years 2 .
Although it is widely recognized that cataract extraction and intraocular lens implantation is highly effective and successful, complications due to cataract surgery can result in significant visual impairment as well as additional health care costs 3 .Other causes of poor outcome may be concomitant pathology or uncorrected refractive error 4 .
The Rapid Assessment of Cataract Surgical Services (RACSS) is a protocol that can generate several reports including: prevalence of visual impairment, visual outcome after cataract surgery and major causes of poor visual outcome.There are many examples of RACSS surveys 5,6,7,8,9 .
The objective of this study was to measure the contribution made by cataract surgery complications in causing visual impairment in a population aged 50 and over from Campinas, São Paulo State, Brazil.

Population
According to data from the Brazilian Population Survey, Campinas has 969,396 inhabitants in an area of 801km 2 10 .The sampling frame was formed from the list of all enumeration areas of Campinas included in this survey, as published in the CD-ROM 10 .A column with the cumulative population was added to this list and from this column, 60 clusters were selected using random sampling.This provides a random selection with a probability proportional to the population size.In each cluster 40 people aged 50 and over were to be examined.In the year 2000, there were a total of 174,811 people aged 50 or older in Campinas, of which 2,400 had to be examined.The RACSS method was followed 8 .
The sample size of 2,400 was powerful enough to assess and confirm the expected prevalence of 3% of people with bilateral cataract visual impairment (visual acuity < 6/60 with available correction), with a variation between 3.7% and 2.3%, and a confidence interval of 90%.The study was approved by the Ethics Committee of the University of Campinas (UNICAMP) Medical School.The subjects, who were examined free of charge, agreed to participate in the study and signed an informed consent form.

Examination and field work
Visual acuity is written as a fraction.The number in the numerator position represents the test distance in meters between the eye and the chart being used.The number in the denominator position is the distance at which the subject can read the same figure.This notation quantifies visual discrimination of fine detail.Visual acuity was measured using a tumbling Snellen "E" chart letter of size 60 on one side and size 18 on the other side, at six and three meters.The test took place on the street in front of the peoples' houses, at daylight.Visual acuity was measured for each eye and the smaller letter chart was shown when the bigger could be seen.Visual acuity was assessed with a pinhole when it was less than 3/18, to detect if low vision was due to refractive errors.Patients were interviewed in a shaded place by means of eye examination with a torch, binocular loupe and direct ophthalmoscopy; no dilation of the pupil was used.The examination was performed as in other RACSS studies 5,6,7,8,9 .

Data
The input of data on the appropriate form was performed by one of the ophthalmologists.The forms were entered into a special software program, RACSS version 2.02 for Windows (World Health Organization/International Agency for the Prevention of Blindness, Geneva, Switzerland).The following reports were chosen: prevalence of visual impairment, visual outcome of cataract surgery and major causes of poor visual outcome.Further customized analysis was possible using the analysis facilities of Epi Info (Centers for Disease Control and Prevention, Atlanta, USA).

Results
From the target study population of 2,400, a total of 2,224 participants could be examined, representing coverage of 92.67%, with a mean age of 64 ± 12 years.The gender distribution was 42.04% (935) males and 57.96% (1,289) females.Of the population expected to be examined, 134 were not available and 42 refused the examination.
Patients who had previously been operated (a total of 229 persons with 352 operated eyes) all had their visual acuity measured.Of these, 328 eyes (93.2%) underwent surgery with placement of an intraocular lens (Table 2).The causes of visual impairment after surgery were concurrent disease in 37 eyes (56%), surgical complications in 19 eyes (28.8%) and refractive errors in 10 eyes (15.2%).

Discussion
In the present study, bilateral visual impairment was found in 3.37% and unilateral in 7.06% of the study population.Cataract surgery complications were the 5 th most important cause of visual impairment.They were responsible for the impairment in 4% of participants and 6.1% of the eyes.The other most important causes of visual impairment in order of significance were cataract, posterior segment diseases (including macular diseases but not senile macular degeneration), diabetic retinopathy and glaucoma.
Surgery only plays a small part in the cure of cataract.Much of what has happened in the last 15 years has been driven by the need for greater surgical output, a need that is met relatively eas-ily, rather than by a regard for vision outcomes and rehabilitation.Concern with auditing outcomes and assuring quality is a relatively recent phenomenon.It has come to show that despite all the attention given to cataract surgical detail, postoperative vision results are less positive, and complication rates greater than anticipated 11 .For example, an assessment of cataract surgery in India showed that 21% of patients had a very poor outcome (presenting visual acuity < 6/60), with another 35% having poor outcomes (6/18 to 6/60) 12 .In neighboring Nepal, 21% are even blind postoperatively, presenting a visual acuity of < 6/60 in both eyes.However, this improves to 7% with best correction 13,14 .
A population-based survey in KwaZulu-Natal showed that a campaign to increase cataract surgery had little effect on the prevalence of blindness, but shifted the etiology from cataract to uncorrected aphakia 15 .A high priority for cataract surgery must be to make intraocular lens implantation a routine part of cataract surgery, and to encourage prospective monitoring of outcomes in order to improve surgical results 4,16 .Further improvements can be achieved by ensuring that patients are refracted following surgery, and that they are provided with glasses to correct residual refractive error 17 .The greatest challenge for ophthalmologists, policy-makers, donors, and researchers is not developing new techniques or treatments, but ensuring that the high standards of both output and outcome that are currently manifest in some centers become the norm 17 .A survey at the State University of Campinas demonstrated that good quality surgery may improve vision status in 92.8% of blind patients 18 .
Our study had some limitations.For example, the frequency of postoperative cataract complications varies from between 0.13% for endophthalmitis to 19.7% for posterior capsule opacification 3 .A limitation of this manuscript is that it studies the presence or absence of cataract complications but not each one individually because RACSS was designed to study the global frequency.Another limitation is the eye examination method, non-dilated direct ophthalmoscopy, which limits the diagnosis.The dilatation of the pupil and use of other basic equipment such as the slit lamp and the applanation tonometer would give more precision to the results.However the RACSS methods used in this study are standardized and were previously tested and approved, and its results are comparable to those found around the world 5,6,7,8,9 .
To improve the outcome of our cataract surgery the following should be applied: (1) cataract surgeons must monitor their intraoperative complications and the visual outcome of their surgery; (2) program managers must ensure adequate training of cataract surgeons, ensure provision of adequate instrumentation and required surgical consumables and ensure that all cataract surgeons are monitoring the outcome of their surgeries 4 .

Conclusion
Cataract surgery complications are a major cause of visual impairment in the over-50 population in Campinas.Their prevention and treatment must be included in public health care policies.

Resumo
Objetivou-se avaliar a relevância das complicações de facectomias como causa de Contributors D. F. Oliveira and C. E. L. Arieta participated in the research design, data collection and analysis, manuscript review and final draft of the article.R. P. C. Lira participated in the research design, data analysis, manuscript review and final draft of the article.A. P. C. Lupinacci and M. Paccola participated in the research design, data collection and analysis, and final draft of the article.C. E. L. Arieta participated in the research design, data collection and analysis, manuscript review and final draft of the article.