Introduction

The global demand for cost effective, timely, and high quality cataract surgery has never been greater, driven by an ageing population with high expectations and an ever increasing unmet need, particularly in developing countries. It is well-established that the leading cause of blindness and visual impairment in much of the world today is cataract.

The need for cataract surgery

We believe that, fundamentally, it should be possible to eliminate cataract blindness – there is an effective and reliable way to identify cases and a sight restoring treatment is available. Developed health systems such as those in Western Europe, North America and Australia have greatly reduced the prevalence of cataract by establishing an adequate cataract surgical rate (CSR). This term refers to the number of cataract operations performed per million population per year. It can be calculated from the number of surgical procedures and the population under consideration. In order to eliminate cataract blindness the CSR needs to equal the incidence (number of new cases) of cataract blindness – estimated at approximately 2000–3000 cases per million per year. If the CSR is less than 2000, the surgery rate will not keep up with the incidence, some people who become blind due to cataract will remain untreated and will remain blind until they die, and the backlog will continue to increase. This is the situation in much of the developing world.

If the CSR is 2000–3000, or more people who become blind due to cataract will be treated, the backlog will be abolished over a period of approximately 5 years. This applies if a visual acuity of <6/60 is used as the indication for surgery; a higher visual acuity cut-off will increase the required CSR. Figure 4.1 shows the CSR in WHO defined regions; only four regions have an adequate rate and millions of people have minimal or no access to surgery1.

Fig. 4.1 Estimates of global cataract surgical rates.

Reproduced with permission from Foster A. Cataract:Epidemiology and Service Delivery. Chapter 3. Survey of Ophthalmology 45, Supplement 1:S32 –44, 2000.

Cataract surgery outcomes

The solution to the world’s unmet need would seem to be increasing the number of operations but it is not sufficient to simply perform more surgery; the visual result of the procedure must be of the highest possible standard. Cataract surgery is a potentially sight restoring operation and our aim as surgeons must be to deliver the best possible visual outcomes with the lowest possible complication rate. Continuous monitoring of both individual and national outcomes is well-established practice in all modern eye units. Unfortunately this practice is not always a priority in developing countries where resources are scarce and a culture of audit and accountability is not necessarily well established. Yorston et al.2 have established the role of prospective monitoring in improving surgical outcomes.

The World Health Organization (WHO) has defined standards for the outcomes of cataract surgery (Fig. 4.2). There are three categories: Good (postoperative visual acuity outcome better than 6/18); Borderline (visual acuity outcome in the range 6/18–6/60); and Poor (visual acuity less than 6/60). The WHO recommendations for acceptable outcomes at 1 day postoperation are 40% cases achieving acuity between 6/6 and 6/18 (Good result); 50% of cases achieving a visual acuity between 6/24 and 6/60 (Borderline result); and no more than 10% cases at less than 6/60 (Poor result) with half of those due to intraoperative complications. In many situations it is difficult to obtain follow-up at 6–8 weeks, but by then the recommendations have risen to 85% of cases with a Good outcome and only 5% with a Poor outcome. Factors determining surgical outcome include ocular co-morbidity, the availability of preoperative biometry, surgical expertise/facilities and correction of residual refractive error.

Fig. 4.2 WHO Prevention of Blindness Programme Chart.

Reproduced with permission from Foster A. Cataract: Epidemiology and Service Delivery. Chapter 3. Survey of Ophthalmology 45, Supplement 1:S32–44, 2000.

Monitoring cataract surgical outcomes is crucial if the quality of surgery is to be improved over time. Poor results will constitute a significant barrier to cataract surgery uptake in any given service. Large population-based studies suggest a wide variation in surgical outcomes depending on the procedure performed. National data on the results of phacoemulsification surgery in the UK and Western Europe suggest that over 80% of patients achieve a final visual acuity of 6/12 or better with a complication rate of 4%, although a more recent study has analysed the complication rate in more detail and according to risk stratification3. Data from Eastern Africa and India show a wide variation in final visual acuity ranging between 38 and 80% of patients achieving 6/18 or better with a complication rate between 7 and 20% of cases. Many of these studies include patients undergoing extracapsular, intracapsular and even couching procedures so direct comparisons are not possible4–12.

Indicators of a successful service

How do we know we are delivering an optimum service? Regardless of whether we are working in Western Europe or Sub-Saharan Africa we need to identify robust indicators of performance. These may be targeted at global, national or regional level and require the best available data collection methodology.

Clearly the most relevant indicator is the prevalence of blindness and visual impairment due to cataract in any given population. This will be obtained from population-based epidemiological studies, where available, or RAAB (rapid assessment of avoidable blindness) data. Regular review of national or district cataract output (number of cataract operations per year) and cataract surgical rates will hopefully show a trend to maximum cataract surgical coverage. This indicates the proportion of need that is being met. Various parameters can be examined such as the proportion of aphakia or pseudophakia in relation to blindness due to cataract, or the proportion of cataract surgery with intraocular lenses. Finally, as previously outlined, regular accurate data collection on the quality of surgery in representative samples of the population is essential.

Cost of cataract surgery

In order to deliver an effective cataract service, wherever it is based, it must be affordable. Cost containment, cost recovery and income generation are fundamental considerations when planning and maintaining an adequate throughput of cataract operations.

Increasing capacity and maintaining the uptake of surgery will reduce unit costs overall; sourcing low cost technologies and cheap consumables will be priorities in planning any service in developing countries. These running costs must be covered by income generation, which in turn could be either fee for service or from subsidies. Cost recovery models such as variations in non-clinical care are well-established in both developed and developing countries.

Global inequalities in eye care provision – VISION 2020 The Right To Sight

The concept of global health care has emerged as a responsibility every developed nation increasingly accepts. Approximately 18 million people are blind from cataract world wide, the vast majority in Africa, Asia, Latin America and Eastern Europe. Projected figures suggest that this figure will double between 1990 and 2020. VISION 2020 is the global initiative for the elimination of avoidable blindness (Fig. 4.3). It was launched in 1999, jointly by the World Health Organization (WHO) and the International Agency for the Prevention of Blindness (IAPB) with an international membership of NGOs, professional associations, eye care institutions and corporations. Over two decades, it is hoped that VISION 2020 will prevent 100 million people from becoming blind. One of the principal objectives is ‘to provide cataract surgical services at a rate adequate to eliminate the backlog of cataract over a number of years, at a price that is affordable for all people, both rural and urban, in an equitable manner, and with a high success rate in terms of visual outcome and improved quality of life’. Some of the strategies that have been proposed to meet this target include creating a sustainable demand for cataract services. In order to achieve this, barriers to the uptake of existing services must be overcome. A degree of unmet need for surgery is present in all health care systems, but the reasons may well vary according to local economic, cultural and social differences. Identifying cases of blind and visually impaired from cataract requires the support of local communities both before surgery and in rehabilitation afterwards. Population screening for new cases should only be performed when surgical services are well-established and can meet demand by increasing the cataract surgical rate. This will necessitate developing local manpower and resources in order to provide services at a cost that all patients can afford.

Fig. 4.3 VISION 2020 is the global initiative for the elimination of avoidable blindness.

Used with permission of the International Agency for the Prevention of Blindness [IAPB].

Services should be readily available and close to where people live. Many communities live in remote areas and outreach facilities must be developed. Regardless of the type of service, VISION 2020 aims to promote high quality surgery with a good visual outcome. Preoperative biometry and intraocular lenses should be used for all patients. Monitoring of surgical outcomes should be encouraged to improve quality. Finally the initiative aims to work alongside local governmental and non-governmental bodies.

The targets for any cataract service are driven by the CSR (which depends on the prevalence of cataract, the visual acuity recommended for eligibility for surgery and demographic trends); the cataract surgical coverage, which should be the highest possible (at least 85%); and the quality of the service as measured by the WHO criteria (i.e. at least 85% of eyes achieve 6/18 or better postoperatively).

Conclusions

In the subsequent chapters of this section all aspects of cataract surgery will be discussed. It is entirely appropriate that every detail of the procedure should be explored and analysed in order to set a gold standard for performance and training. It is equally important that we extend our responsibilities for training and standard setting to include health care workers in less well developed delivery systems across the globe.