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Cataract surgery outcomes at a UK independent sector treatment centre
  1. Zeba A Syed1,
  2. Javad Moayedi2,
  3. Mehdi Mohamedi2,
  4. Jacob Tashter2,
  5. Teresa Anthony2,
  6. Celadet Celiker2,
  7. Georges Khazen3,
  8. Samir A Melki1,2,4
  1. 1Massachusetts Eye & Ear Infirmary, Boston, Massachusetts, USA
  2. 2UK Specialist Hospitals, London, UK
  3. 3Lebanese American University, Beirut, Lebanon
  4. 4Boston Eye Group, Boston, Massachusetts, USA
  1. Correspondence to Dr Samir A Melki, Cornea and Refractive Surgery Service, Massachusetts Eye & Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA; samir_melki{at}


Background/Aims The goal of this study was to review cataract surgery outcomes at three independent surgery treatment centres established by the UK Specialist Hospitals (UKSH) and to compare these outcomes with recognised benchmarks.

Methods All patients who underwent cataract surgery at UKSH between July 2005 and March 2013 were included. Complication rates were obtained using annual quality reports, logbooks kept in operating theatres and outpatient departments, and electronic medical records. Refractive outcomes and biometry results between December 2010 and March 2013 were obtained from electronic medical records. Results were compared with previously published benchmarks.

Results This study reviewed 20 070 cataract surgeries. UKSH had lower rates of several operative complications compared with the Cataract National Dataset benchmark study. These included choroidal haemorrhage, hyphaema, intraocular lens complications, iris damage from phacoemulsification, nuclear fragment into the vitreous, phacoemulsification wound burn, posterior capsule rupture or vitreous loss or both, vitreous in anterior chamber, and zonular dialysis. UKSH had lower rates of postoperative complications including corneal decompensation, cystoid macular oedema, iris to wound, posterior capsule opacification with yttrium aluminium garnet indicated, raised intraocular pressure, retained soft lens matter, uveitis, vitreous to section, and wound leak. Biometry outcomes at UKSH were significantly better than recently published benchmarks from the National Healthcare Service.

Conclusions This is the first large-scale retrospective study of cataract surgery outcomes in the UK independent sector. The results indicate comparable or lower rates for most complications as compared with data collected in a previously published study.

  • Public health
  • Treatment Surgery

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The UK has witnessed a dramatic rise in the number of cataract operations performed in the National Health Service (NHS) annually over the last several decades. A 10-fold rise occurred in England between the years 1968 and 2003, with notable regional variation.1 Cataract surgery is now the most common operation performed in the NHS, and 332 625 operations were reported in England between 2009 and 2010.2

Although the publicly funded NHS provides the majority of UK healthcare, independent sector treatment centres (ISTCs) provide an important albeit minority part of this care, particularly for elective surgical procedures.3 The UK independent sector is viewed as a partner to the NHS, delivering over 80 000 operations and treatments annually for NHS patients.4 By the end of 2007, ISTCs performed 4% of cataract procedures nationally.5 There are no data to our knowledge reporting cataract surgery outcomes in the independent healthcare sector.

The goal of this study was to review and assess cataract surgery outcomes at three ISTCs over an 8-year period and to compare outcomes to those previously reported from NHS facilities.

Materials and methods

Patient selection

All patients who underwent cataract surgery at UK Specialist Hospitals (UKSH) between July 2005 and March 2013 were included in this study. These patients had a lens opacity causing interference in vision with confirmation of cataract by slit-lamp biomicroscopy. Patients were not eligible for cataract surgery at UKSH if they were under 18 years of age or if they had medical comorbidities such as a high suspicion of cancer or an unstable physical status at a level of 3 or above based on the American Society of Anesthesiologists classification system. Other exclusion criteria included pregnancy and a body mass index of more than 40 or 45 for cases operated upon under general or local anaesthesia, respectively. Due to their low number (334), cases operated upon by surgeons in training were analysed separately. The same clinical pathway was strictly adhered to by all surgeons.

Data gathering

This study involved a compilation of outcomes data starting in July 2005 from three ISTCs established by UKSH, a ‘for-profit’ organisation contracted with the NHS to provide medical services. Its first ISTC, Shepton Mallet Treatment Center (SMTC), was established in July 2005. This was followed by the Emersons Green Treatment Center (EGTC) and the Devizes Treatment Center (DVTC) in November 2009. EGTC and DVTC are collectively referred to as AGW due to their overlapping service to the geographical areas of Avon, Gloucester and Wiltshire.

Preoperative assessment was performed by a consultant surgeon in the outpatient setting. Biometry was performed either via optical coherence biometry (IOL Master, Zeiss, LOC) or via immersion ultrasonic measurement (Alcon Occuscan, Alcon Fort Worth, Texas, USA) for SMTC and Sonomed Pacscan 300 (Lake Success, New York, USA) for AGW. Ultrasonic measurements were performed in cases where IOL Master measurements were deemed unreliable or unobtainable.

Data on complication rates were collected using three methods. First, we reviewed annual reports produced by the treatment centres. These reports allow for ongoing evaluation of quality of care provided at the institutions as required by their contract with the UK Department of Health. Second, we reviewed logbooks kept in operating theatres and outpatient departments. Outcomes data between July 2005 and December 2010 were collected manually into complication logs kept in the theatre and outpatient department. Finally, we reviewed complications from the electronic medical record (EMR) (Medisoft, Leeds, UK) used at these ISTCs. In December 2010, Medisoft was implemented at SMTC and AGW. Another EMR system (Maxims, Woburn Sands, UK) was used at AGW between 2009 and 2010 for documentation of operative complications. Patients were followed for a period of 30 days to assess for complications related to their cataract surgery.

Biometry results were reviewed for the period extending from December 2010 until March 2013, as this time span provided the most comprehensive and reliable data due to the implementation of Medisoft. A refraction target was set by the surgeon preoperatively when choosing the lens implant for each individual patient. The patient's biometry data collected in the outpatient department were used to identify the most appropriate implant. The patients were examined by community optometrists 4–5 weeks postoperatively. This refractive measurement was sent to the ISTC for comparison to the predicted spherical equivalent target.

Data analysis

Complication rates were compared with published benchmarks from the Cataract National Dataset (CND).6 Refractive outcomes were compared with biometry benchmarks recently published by the Leeds Teaching Hospital NHS Trust.7 UKSH data was compared with national outcomes using ORs, emphasising the fold increase of complications between the two entities. χ2 tests were employed to detect differences in complication rates and biometry outcomes between groups. Fisher's exact testing was used when criteria for χ2 testing were not met. Statistical analyses were performed using MATLAB (MathWorks, Natick, Massachusetts, USA). Differences were reported as statistically significant if the p value was ≤0.05.


A total of 20 070 cataract extractions were performed at UKSH between July 2005 and March 2013. At SMTC, the mean age of patients undergoing cataract surgery was 75.7 (±11.98) years, with 39.0% of patients male and 61.0% female. At AGW, the mean age was 75.0 (±13.85) years, with 40.2% patients male and 59.8% female. Cataract surgeries at SMTC were performed by two permanent and eight locum eye surgeons, while those at AGW were performed by seven permanent and seven locum surgeons. All surgeons were on the specialist register of the General Medical Council and had extensive prior cataract surgery experience.


The type of anaesthesia could be retrieved for 9776 cases at SMTC and 5979 cases at AGW. A minority of cases were performed under general endotracheal anaesthesia (1.95% at SMTC and 0.40% at AGW). The rest of the cases were performed under a combination of topical and intracameral anaesthesia. Very few topical cases were supplemented with sub-Tenon's anaesthesia. The latter figures were not recorded.

Operative complications

The presence or absence of operative complications was noted in all cases. The type, number and percentage of the total for each operative complication at UKSH are shown in table 1. At UKSH, the most frequent operative complication was posterior capsule rupture (PCR) or vitreous loss or both, occurring in 107 cases with a total incidence of 0.53%. This includes cases involving anterior vitrectomy, zonular dialysis with vitreous loss, and vitreous to section at the end of surgery.

Table 1

Operative complication rates at UKSH compared with the national benchmark and UKSH trainees

ORs were obtained to compare operative complications at CND and USKH. Statistically significant differences are presented in table 1. In comparison to this national survey, UKSH had lower rates of choroidal or suprachoroidal haemorrhage, hyphaema, intraocular lens complications, iris damage from phacoemulsification, nuclear fragment into the vitreous or dropped nucleus, phacoemulsification wound burn, PCR or vitreous loss or both, vitreous in anterior chamber and zonular dialysis (table 1).

Due to the small number of cases (334), operations performed by surgeons in training were analysed separately. ORs comparing operative complications of trainees and full surgeons were obtained. These results are presented in table 1. Compared with full surgeons, trainees had higher rates of corneal epithelial abrasion, hyphaema, iris damage from phacoemulsification, nuclear fragment into the vitreous or dropped nucleus, PCR or vitreous loss or both, and zonular dialysis.

Postoperative complications

As with operative complications, all patients were followed to assess for the presence or absence of postoperative complications. Type, number and percentage of postoperative complications are displayed in table 2. The most common postoperative complication at UKSH was corneal decompensation, occurring in 119 cases with a frequency of 0.59%.

Table 2

Postoperative complication rates at UKSH compared with the national benchmark

ORs were obtained to compare postoperative complications at CND and USKH. Statistical outcomes from these comparisons are presented in table 2. UKSH had lower rates of corneal decompensation, cystoid macular oedema or macular oedema, iris to wound, posterior capsule opacification with yttrium aluminium garnet indicated, raised intraocular pressure (>21 mm Hg), retained soft lens matter, uveitis, vitreous to section, and wound leak or rupture.

The rate of infectious endophthalmitis was 0.07% and 0.03%, respectively, before and after intracameral antibiotics became standard practice at UKSH in 2009. This difference was not statistically significant.

A cluster of toxic anterior segment syndrome (TASS) cases occurred at the SMTC over a 2-year period from 2007 to 2009. This has become a rare occurrence since the establishment of new procedures, most notably a more thorough irrigation of the reusable cannulae prior to sterilisation. TASS was diagnosed by the presence of unexpected inflammation in the anterior segment with or without hypopyon. It was distinguished from infectious endophthalmitis by the absence of pain or conjunctival hyperaemia. The diagnosis was further confirmed by improvement on intensive topical steroid therapy.

Biometry outcomes

Postoperative biometry data were reviewed for all EMR data between December 2010 and March 2013. In total, data were available for 2602 cases at UKSH. Results are compared with cataract surgery outcome standards established by the Leeds Teaching Hospital NHS Trust in table 3. At UKSH, 66.76% of eyes were within 0.5 dioptres (D) of predicted spherical equivalent compared with the 55.0% benchmark proposed by the Leeds Teaching Hospital NHS Trust. In addition, 89.90% of eyes were within 1.0 D of predicted spherical equivalent at UKSH compared with the 85.0% benchmark value proposed by the Leeds Teaching Hospital NHS Trust. Both of these differences were statistically significant (table 3).

Table 3

Biometry outcomes at UKSH compared with the national benchmark


There have been no published reports of cataract surgery outcomes from the independent healthcare sector in the UK. The existence of the independent sector alongside the NHS has long been a source of debate.8 A particular area of concern is the process of regulation and quality assurance within that sector.9 While the NHS is structured with line management and accountability through to the Department of Health and Secretary of State, the independent sector consists of a variety of individual and group providers. For this reason, organisations such as the Care Quality Commission have been appointed to be responsible for regulation of this sector.10 Outcomes data within the independent sector are crucial to ensure that appropriate standards of quality are provided to all patients, regardless of the source of care. Although the results of this article do not necessarily extend to all ISTCs, it reviews a significant number of cases performed in that setting and provides a first insight on quality data.

Several national surveys of cataract surgery outcomes have been performed in the UK.6 ,11 A study by Zaidi et al12 found that current cataract surgeries are associated with superior outcomes as compared with two Department of Health funded National Cataract Surgery Surveys. He suggested that we should ‘set the bar higher’ for expectations of outcomes after cataract surgery. The British Royal College of Ophthalmologists addressed this issue by shaping the CND,6 and encouraging national adoption of a data set for electronic data collection. Benefits of such a database would include ongoing evaluation of individual surgeons for annual appraisal, consistent monitoring of clinical results and continued revision of standards of care for cataract outcomes.6

This study has examined several indicators of cataract surgery outcomes at three ISTCs sharing one management structure and adhering to the same clinical governance. Although PCR, vitreous loss and endophthalmitis rates are perhaps the most representative measures of cataract surgery outcomes, a variety of other operative and postoperative outcome measures were collected and compared with recognised benchmarks.

The rate of PCR or vitreous loss or both at UKSH was significantly lower than the CND. The mean benchmark rate of PCR in the UK has trended downwards over the last 15 years. The 1997–1998 National Cataract Surgery Surveys ,13 the National UK Audit of 200411 and the 2009 CND reported rates of PCR of 4.4%, 2.68% and 1.92%, respectively.6 This trend is consistent with the rate of 1.1% reported by Zaidi et al12 at the Western Eye Hospital in London in 2007. A recent large-scale European study including 11 national societies reported a total capsule complication rate of 1.2%.14 It is possible that the lower rate of PCR in this study is due to the difference in the period at which the data was collected. Another explanation may be the level of experience of the operating surgeons. One national survey reported that just over half of NHS cataract operations were performed by consultants, approximately 13% by non-consultant career grade surgeons and just over a third by surgical trainees.6 Surgical training was started at UKSH in November of 2011 and the trainees’ rate of complications was clearly higher than consultants’. This is consistent with data collected in the USA that found that Veterans Health Administration institutions affiliated with training programmes had nearly twice the rates of corrective surgery after cataract extraction than those institutions without such programmes.15

In data derived from the CND study, Johnston et al16 reported rates of PCR for independent surgeons to be 1.41%, an elevated figure when compared with the UKSH rate (0.53%). Given that UKSH data mostly reflects cases performed by consultants, we have used the CND PCR figure of 1.41% (instead of 1.92% which reflects the rate among all surgeons). In an effort to use a similar method of data gathering to the CND, we compared PCR rates at UKSH before and after implementation of electronic health records. There was no significant difference in the PCR rate related to the method of data collection (table 4).

Table 4

EMR data

The endophthalmitis incidence at UKSH dropped from 0.07% to 0.03% after the implementation of intracameral antibiotics at the end of procedures (p>0.05). Although not statistically significant, the downward trend is consistent with the results shown by several studies.17–19

Significantly lower rates were found at UKSH for most other operative and postoperative complications (tables 1 and 2). It is possible that patients undergoing cataract surgery in ISTCs are healthier, accounting for better outcomes. Browne et al20 have shown that patients treated in the independent sector have fewer comorbidities and have less severe primary conditions. However, after adjustment for preoperative characteristics, patients undergoing cataract surgery in ISTCs still reported fewer postoperative problems and achieved a slightly greater improvement in functional status and quality of life than those treated in NHS facilities.20 NHS hospitals may be presented with more complicated cataracts from patients already being managed at their facility for other ocular morbidities. These may include patients with chronic uveitis, previous posterior vitrectomy or history of retinal detachment who are more likely to remain within an NHS facility rather than be referred to the independent sector. These patients usually present with operative and postoperative challenges that may be reflected in the difference in outcomes. To avoid misrepresentation, Sparrow et al21 recommended developing a robust method of risk adjustment to account for complexity in the case mix of each surgeon. Narendran et al22 reported a simple composite risk estimation system that could be used in prospective studies of cataract outcomes to allow a reliable comparison of different providers. A possible explanation to the difference in outcomes seen in this audit is the strict adherence of all surgeons to the same clinical pathway. This allows standardisation of clinical operations which has been shown to improve quality of care.23

Biometry outcomes are a key indicator of accuracy of refractive results after cataract surgery. UKSH biometry outcomes were statistically better than those reported by the Leeds Teaching Hospital NHS Trust in terms of proportion of cases within 0.5 D and 1.0 D of target refraction, although, it is important to note that refractive outcomes of 95% within 1.0 D of target refraction have been achieved in other national settings.24

It is difficult to explain this difference without studying preoperative factors, such as astigmatism. It must be noted that the capture rate of postoperative refraction was only about 10% at UKSH, compared with more than 60% in the Leeds study. A larger sample size may have affected results.

There are several limitations to this study. One limitation is the bias inherent to self-reporting of complications. Measures implemented at UKSH should have minimised the impact of this limitation. These included systematic video recording of the majority of cataract surgeries and periodic audits to verify accuracy of operative complication reporting. Similarly, many postoperative examinations were performed by more than one surgeon as well as by community optometrists, allowing reporting by more than one observer. Biometry outcomes were not subject to the self-reporting bias as they were compiled from examinations performed by optometrists independent of UKSH. Another limitation of this study is the possibility that patients may have sought care elsewhere for a complication related to their cataract surgery, leading to an underreporting of postoperative complications.

In summary, this is the first report of outcomes from a large series of cataract operations at UK ISTCs. The results indicate lower rates of complications, including PCR, as compared with a previously reported benchmark. A more representative comparison would be possible if surgeons’ outcomes could be adjusted for case mix complexity. The Royal College of Ophthalmologists has recently been awarded a contract by the Healthcare Quality Improvement Partnership to conduct an audit of cataract surgery outcomes over 3 years from 2014 to 2017.25 This will promote an even better understanding of current surgical practices and allow for standardised benchmarking.



  • Contributors All authors have contributed to the collection of data for this project. In addition, ZAS and SAM contributed to the writing and editing of this manuscript. GK contributed to statistical analyses of the data.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.