Abstract
Purpose
Cataract is the leading cause of reversible blindness in developing countries, with variable visual outcome following surgery. This work aims at assessing the outcomes of cataract surgery at Kasr Al Ainy Hospital and identifying the reasons for borderline and poor outcome in the studied group.
Methods
A total of 150 eyes of patients with cataract and no other ocular pathology were included in this study. Uncorrected visual acuity (UCVA) and corrected visual acuity (CVA), complete ocular examination using slit-lamp, applanation tonometry, and ophthalmoscopy were performed for all patients. Biometry for intraocular lens power calculation and operative data were recorded. Patients were followed for 6 weeks; UCVA, CVA, and any complications were noted.
Results
Mean preoperative CVA was 0.16 ± 0.16 (SD) and mean postoperative CVA was 0.66 ± 0.33 (p<0.001). Forty-two percent of surgeries were performed by junior staff under training. Thirty-five surgeries were complicated by posterior capsular rupture. Mean CVA at 6 weeks in the uncomplicated group was 0.77 ± 0.22; in the complicated group, 0.28 ± 0.34 (p<0.001). Biometry was accurate in 51.6% of cases. Most important causes for suboptimal outcome were aphakia, astigmatism, posterior capsular opacification, and corneal edema.
Conclusions
Kasr Al Ainy Hospital achieved CVA 6/9 or more in 69.3% and CVA 6/18 or more in 81.3% of patients. The capsular complication rate was high at 23.3%. The high complication rate is attributed to the nature of the teaching hospital where most surgeons were in their learning periods.
Introduction
Cataract is the leading cause of reversible blindness in developing countries. In 2010, WHO estimated that there are almost 18 million people who are bilaterally blind from cataract in the world, representing almost half of the causes of blindness due to eye diseases (1).
Visual outcome following cataract surgery can be used to monitor the quality of cataract surgery service. The could be done by examining the records of patients who have undergone cataract surgery to assess preoperative and postoperative corrected visual acuity (CVA), the surgical procedure, and any reported complications. Another method involves a population-based assessment in which a random sample of the population is examined and the visual acuity (VA) of those who have undergone cataract operations is measured to estimate the prevalence of severe visual impairment and blindness related to cataract (2).
The WHO Prevention of Blindness and Deafness developed standards for cataract surgery outcomes. It considered outcome to be good when CVA ranged between 6/6 (20/20) and 6/18 (20/60) for 85% of the cases operated. Borderline outcome was considered CVA less than 6/18 (20/60) to 6/60 (20/200) in fewer than 15% of the cases operated for cataract. Poor outcome was defined as CVA less than 6/60 (20/200), which should occur in fewer than 5% of cases operated for cataract (3, 4).
This work assesses the outcomes of cataract surgery at Kasr Alainy Hospital in Cairo University and identifies the reasons for borderline and poor outcome in the studied group.
Methods
A hospital-based observational, prospective study that included 150 eyes of 150 patients who underwent phacoemulsification in Kasr Al Ainy Hospital was conducted to measure postoperative visual outcome. Patients were recruited from the outpatient clinic of Kasr Alainy Hospital, Cairo University, between August 2014 and July 2015.
Patients 40 years or older being treated for cataract with no other ocular pathologies that might interfere with visual outcome were included in the study. Patients with traumatic cataracts and those who had cataract surgery for cosmetic reasons were excluded. Patients with ocular pathologies that may affect visual outcome such as corneal opacities, glaucoma, age-related macular degeneration, hereditary dystrophies, diabetic retinopathy, or any other retinal vascular disease were also excluded. Patients with subluxated lens and pseudoexfoliation, which may pose a risk for surgical complications, were excluded. The study was approved by the ophthalmology department of Cairo University.
Written informed consent was obtained from each participant. Adequate history-taking was done, uncorrected VA (UCVA) and CVA were performed using the illuminated Snellen chart, a thorough slit-lamp examination was done for cataract grading (cortical, nuclear, or mixed), applanation tonometry was performed to record the intraocular pressure, and fundus examination was performed by indirect ophthalmoscopy. Intraocular lens (IOL) power was calculated by different formulae, depending on the axial length and the operator's experience. The IOL power usually was chosen to obtain postoperative emmetropia (-0.50 D).
Phacoemulsification was performed in all patients under retrobulbar or peribulbar anesthesia using lidocaine 2% and bupivacaine 0.75%. All the patients were operated upon by means of phacoemulsification. All the surgical details were recorded. The rank of the surgeon (whether senior staff or under training), any intraoperative complication, and the type of IOL implanted were recorded.
The patients were examined on the first postoperative day. The UCVA was recorded and slit-lamp examination was done, taking notes on the corneal condition, the surgical wound, anterior chamber depth and IOL position, red reflex, and any signs of uveitis or endophthalmitis. Fundus was examined in cases with complicated surgery to exclude any dropped parts and to exclude peripheral retinal breaks.
Patients were prescribed topical steroid and antibiotic eyedrops. At 1 week, 4 weeks, and 6 weeks from the surgery, the UCVA was recorded, refraction was done by autorefractor, and the CVA was recorded.
Visual outcome was categorized using the WHO standard, where good outcome is CVA 6/6 (20/20) to 6/18 (20/60), borderline vision is less than 6/18 (20/60) to 6/60 (20/200), and poor vision is less than 6/60 (20/200).
If the CVA was less than 6/9 (20/30) for no obvious cause, macular optical coherence tomography (Optovue RTVue-100; Fremont, CA, USA) was done to exclude Irvine-Gass syndrome or other retinal pathology. Visual acuity was transferred to decimal equivalent for statistical analysis.
Statistical Methods
Data were coded and entered using the statistical package SPSS version 22 (Chicago, IL, USA). Data were summarized using mean, standard deviation, median, minimum, and maximum for quantitative variables and frequencies (number of cases) and relative frequencies (percentages) for categorical variables. Comparison of quantitative variables was done using the nonparametric Mann-Whitney U test when comparing 2 groups. Comparison between values measured before and after operation was done using the nonparametric Wilcoxon signed-rank test. For comparing categorical data, chi-square test was performed. Exact test was used instead when the expected frequency is less than 5. p<0.05 was considered statistically significant.
Results
A total of 150 patients (72 male, 78 female) were operated on. The mean age of the patients was 58.6 ± 8.3 years (range 40-78). One hundred patients were healthy, 24 (16%) were diabetic, and 26 (17.3%) were hypertensive with normal fundus. Eighty-seven surgeries (58%) were performed by senior staff and 63 (42%) surgeries were carried by junior staff under training. Grading of cataract was as follows: 62 (41.3%) had cortical cataract, 14 (9.3%) nuclear, and 74 (49.3%) had mixed cataract. Mean preoperative CVA was 0.16 (20/125) ± 0.16 SD.
The preoperative CVA distribution is shown in Table I.
Preoperative corrected visual acuity (CVA) of patients
A total of 115 surgeries (76.6%) were uneventful and 35 (23.3%) were complicated by posterior capsular rupture (33 cases had posterior capsular rupture and 2 cases had zonular dialysis). Figure 1 shows the distribution of complications by surgeon rank. Mean CVA at 6 weeks in the uncomplicated group was 0.77 ± 0.22 (∼20/25) as compared to the complicated group, which was 0.28 ± 0.34 (∼20/80) (p<0.001).
Percentage of complicated cases according to surgeon rank.
A total of 140 patients (93.3%) had primary IOL implantation during the surgery, and 10 patients (6.7%) were left aphakic. The different types of IOL implanted are shown in Table II.
Types and number of intraocular lenses (IOLs) implanted during surgery
AC IOL = anterior chamber intraocular lens; PMMA = polymethylmethacrylate.
Postoperative UCVA after 6 weeks from the operation ranged from no light perception (NLP) (0.00) to 1.0 (20/20) with a mean of 0.31 ± 0.2 (20/60). Postoperative CVA after 6 weeks from the operation ranged from NLP (0.00) to 1.0, mean 0.66 ± 0.33 (∼20/30).
The distribution of postoperative UCVA and CVA after 6 weeks is shown in Table III.
Postoperative uncorrected visual acuity (UCVA) and corrected visual acuity (CVA) after 6 weeks
VA = visual acuity.
At 6 weeks, there was a statistically significant difference between the postoperative UCVA and CVA (p<0.001).
Postoperative refraction after 6 weeks (spherical equivalent) ranged between -8.50 and +2.00 D, with a mean of -0.98 ± 1.23. Table IV shows the distribution of the postoperative refraction after 6 weeks.
Postoperative refraction after 6 weeks
Comparison between preoperative and postoperative CVA after 6 weeks shows a statistically significant difference, as shown in Table V.
Comparison between preoperative corrected visual acuity (CVA) and postoperative CVA after 6 weeks
A total of 104 of our patients (69.3%) achieved CVA of 6/9 (20/30) or more. A total of 46 patients (30.7%) achieved CVA less than 6/9 (20/30). Causes of suboptimal VA (below 6/9) (20/30) are shown in Table VI.
Causes of suboptimal visual acuity below 6/9 (20/30)
We could not find an explanation for the CVA being less than 6/9 (20/30), and examination of the eye was normal. Thus macular optical coherence tomography (OCT) was done for these patients. Three showed interruption at the inner segment/outer segment junction; the rest had normal OCT, so amblyopia was suggested, or diminution of vision due to aging.
A case of full-thickness macular hole that was missed during the preoperative assessment.
Discussion
The outcome of cataract surgery is as important as measuring the quantity of surgical operations performed. However, the outcome of cataract surgery is not always as good as assumed; the WHO has set standards for outcome of cataract surgery. In this study, 81.3% of patients achieved CVA of 6/18 (20/60) or better (good outcome), 4.0% of patients achieved CVA less than 6/18 (20/60) but better than 6/60 (20/200) (borderline outcome), and the remaining 14.7% of patients achieved CVA less than 6/60 (20/200) (poor outcome). These results are comparable to the WHO standards. Our results are nearly in line with the WHO recommendations for good and borderline outcome but a higher percentage of poor outcome was recorded (14.7%). This may be due to the higher rate of surgical complications: there were 35 (23.3%) complicated cases. Thirty-three of them were complicated primarily by posterior capsular rupture and 2 other patients had zonular dialysis during the surgery. There was a statistically significant difference between the CVA for the uncomplicated cases and the complicated cases with p value less than 0.001.
The rate of capsular complications in different studies ranged from 0.9% to 1.95%, and good outcome was achieved in 87.8%-95.1% (5–6–7). The low percentage of posterior capsular rupture in these series may be due to a higher percentage of cases operated by consultants and better facilities available. The high complication rate in the current study may be due to the fact that Kasr Al Ainy is a teaching hospital and the junior staff that operated more than 42% of the cases were still in training. More than 49.3% of the patients had dense cataract, which increases the risk of complications, especially posterior capsular rupture. Poor outcome also can be explained by a short follow-up for the patients and the nature of some pathologies that take more time to improve, such as corneal edema. Our study did not include the outcome of the second interventions done after the phacoemulsification surgery such as secondary implantation for aphakic patients and cases of primary posterior capsular opacification after performing YAG capsulotomy; this would have improved results in the poor outcome group.
The rate of capsular rupture and the visual outcome are comparable to the Kange and coworkers (8) study that was conducted to compare VA of patients after cataract surgery with and without intraoperative complications to assess the outcome on postoperative follow-up. They found that 142 (79.3%) were uneventful, while 37 (20.7%) patients had intraoperative posterior capsular rupture, compared to 23.3% in our study. A final VA of 20/40 or better was achieved in 77.65% of their patients, which was comparable to our results, where CVA of better than 6/18 (20/60) was achieved in 81.3% of the studied sample.
Biometry error was high in the current study (48.4%), which significantly reduced the UCVA. This could be explained by the fact that biometry was conducted by different operators, with different levels of experience using different formulae. Also, noncontact optical biometry could not be used in many cases with very dense cataracts. Uncorrected refractive error was the main cause (72.9%) of visual impairment in pseudophakic eyes in a study by Kandel and coworkers (9). In another study, 73.2% of cataract patients were within ± 1.0 D of the target refraction after surgery (10). A refractive accuracy (absolute deviation of target refraction from spherical equivalent) of ≤1 D was reported in 72%-97% of the patients and a total of 45%-80% of the patients showed a refractive accuracy of ≤0.5 D in different studies (11).
Ten patients (6.6%) in this study were initially left aphakic. The high rate of aphakia in our study may be related to the high rate of posterior capsular rupture during surgery. Although 8 totally aphakic patients were found to achieve CVA more than 6/60 (20/200), we categorized them in the poor outcome category, as their secondary intervention was done after the 6 weeks of follow-up. Compared to other studies, rate of posterior capsular rupture and rate of aphakia following cataract surgery performed by phacoemulsification and extracapsular cataract extraction was 10.5% for posterior capsular rupture, and a total of 11 cases (1.9%) were left aphakic (12).
Corneal edema was the cause of poor outcome in 6 patients (4%). This edema resolved in 4 patients after treatment about 3 months later and their vision improved. The other 2 patients (1.3%) had nonresolving corneal edema and were scheduled for keratoplasty.
In our study sample, Kasr Al Ainy Hospital achieved CVA 6/9 (20/30) or more in 69.3% and CVA 6/18 (20/60) or more in 81.3% of patients. The capsular complication rate was high at 23.3%. The main causes of poor outcome were the high rate of capsular complication that resulted in aphakia in 6.6% and surgically induced astigmatism in 6%. A high complication rate is attributed to the nature of the teaching hospital, where most surgeons were in their learning periods.
Many variables caused suboptimal outcome following phacoemulsification surgery in our study. Each of these variables presented in a small number of patients, representing a high percentage as the sample size was small, and this led to bias in the results, especially during comparison with other studies that included larger numbers of patients.
Footnotes
Financial support: No financial support was received for this submission.
Conflict of interest: None of the authors has conflict of interest with this submission.