Over 3 decades ago, one of us (A.S.) described cataract as an “epidemiologic problem” in this journal. We’ve learned a great deal about the epidemiology of cataract in the years since, and dramatically improved our approaches to its removal and pseudophakic correction. But unoperated cataracts remain the major cause of avoidable blindness and severe visual impairment in low-income and many middle-income countries. Indeed, in many low-income countries unoperated cataracts account for fully half of all blindness.

We now know a good deal more about the numbers of visually disabling cataract in the world, their prevalence in different regions and ethnic groups, the higher hurdles women in poor communities face in receiving appropriate access to care, and some of the factors that increase the risk of developing cataract in the first place (genetics, sunlight exposure, smoking). But the primary problem at present is that most low- and middle-income countries have yet to grapple with the difficult task of providing high-quality cataract surgical services to those who need them, particularly those residing in poor, rural communities.

Allen Foster cleverly devised a metric by which we could at least begin to consider how far cataract surgical output lags behind cataract surgical needs: the “cataract surgical rate” or “CSR” (the number of cataract operations performed per million people in the population). No one knew what the “right” CSR should be, but it was assumed at the time that rates in the United States and other wealthy countries, which were then roughly 3500 per million, were a reasonable target to aim for. This has remained a useful metric, though as it becomes applied more widely, we’ve begun to recognize the complexities of its interpretation.

For one thing, the CSR in wealthy countries has risen to roughly 5000 or higher, as improvements in postoperative vision have encouraged patients to have the operation at ever milder degrees of visual impairment. In addition, “aging” populations will necessarily require a higher CSR for equivalent benefit, since more people will have cataracts needing attention, as will those populations, like India’s, where cataracts occur at an earlier age. Where the population pyramid is broad-based, because of high fertility and many younger people, the appropriate CSR may well be lower; indeed, Lewallen and associates recently suggested that an appropriate target CSR for sub-Saharan Africa might be half that of the United States. This of course assumes intervening at comparable levels of visual impairment.

India is an example of a country that has truly risen to the challenge. Three decades ago the CSR was only 500; today it is estimated to be 10 times that rate, approaching the CSR of the United States. But exactly what does that mean? Ultimately, a high CSR should mean a lower prevalence of cataract blindness and visual impairment. But this will only occur if 2 conditions are met. The first is that the outcomes of cataract surgery are excellent, and those who have undergone cataract surgery are returned to normal visual functioning. Unfortunately, numerous evaluations of cataract outcome in developing countries have shown that outside highly developed centers, as many as one third or more of the patients who have undergone cataract surgery remain severely visually impaired. The second is that the overall CSR reflects a relatively homogeneous access to cataract surgery across the population. But urban areas almost inevitably experience far higher CSRs than rural areas. The CSR for the western Indian state of Gujarat is reportedly over 12 000; yet in 1 well-studied district the prevalence of bilateral cataract blindness among those 50 years and older was nearly 6%, accounting for 3 out of every 4 blind eyes.

Of the 4 major avoidable causes of blindness originally given priority by the WHO Program for Blindness Prevention and the International Agency for the Prevention of Blindness, the prevalence of 3 of them (trachoma, xerophthalmia, and onchocerciasis) has dramatically declined, largely through widespread public health interventions. The fourth, cataract, remains more or less unchanged, largely because cataract requires skilled surgical intervention.

The International Council of Ophthalmology (ICO) has spent 2 years grappling with the issue of unmet cataract surgical need and has come to conclude that since ophthalmology “owns” cataract surgery, it also “owns” the problem of unmet cataract surgical needs. Its recently adopted Position and Policy Statement, “Access to Cataract Surgical Services,” lists a number of approaches for increasing these services and making them more accessible to those who need them.

The most readily and immediately effective interventions are most relevant to nations that already graduate significant numbers of ophthalmologists. In far too many, these graduates have not been adequately trained to perform pseudophakic surgery, particularly inexpensive, small-incision (phaco-less) surgery appropriate to low-income populations. In other instances, trained and experienced cataract surgeons are not nearly as productive as they might be, because they do not possess the high-throughput surgical orientation that can be achieved with well-trained teams of assistants and more efficient management techniques. Lastly, only a few model systems exist for reaching the poor, particularly the rural poor.

A number of approaches have proven successful. The Aravind Eye System in India, with its cross-subsidization of the poor by those who can afford to pay the “full freight,” has proven to be a successful economic model; screening villages for visually disabling cataract patients, and transporting them to secondary hospitals specializing in high-throughput cataract surgery, has been both efficient and effective. Comparable approaches employed by many other institutions, both small and large, throughout the Asian subcontinent have proved equally impactful. Most patients return to their villages as “satisfied customers,” their excellent visual outcome driving increased demand for cataract surgery. In contrast, China has yet to embark on the same dramatic investment in increasing cataract surgical rates as India, and, as a result, the prevalence of blindness in India has begun to fall, while that in China has risen. A number of ambitious pilot projects are now getting underway in China, particularly ones aimed at training graduate ophthalmologists unskilled in cataract surgery to use small-incision techniques. But it is hard to see how these will dramatically change the landscape any time soon, given the relatively small investment being made and the enormity of the task.

The ICO also recognizes a very different set of circumstances, as is prevalent in much of sub-Saharan Africa: few trained ophthalmologists to begin with. Here the problem of dealing with unmet cataract surgical needs is particularly problematic. A variety of interventions are proposed. Since most African nations graduate few physicians to begin with, there are few available for training in ophthalmology. More medical graduates are needed, and they must be retained, by adequate opportunities and incentives, from emigrating to wealthier nations (in the recent past, more Ghanaian medical graduates worked in the U.K. than in Ghana). In addition, in many African nations ophthalmology training can last 5 to 7 years; as seen in other countries, residency training can be dramatically shortened without loss of surgical excellence.

Besides too few ophthalmologists, reaching the rural poor in sub-Saharan Africa is considerably more challenging than it is in Asia. The population density is much lower and transportation infrastructure far less developed. Meeting the needs of sub-Saharan Africa, where the estimated CSR is only about 200 (and the vast majority of surgery is limited to urban centers), will prove particularly challenging. Some ICO representatives from Africa have suggested that many ophthalmologists well trained in cataract surgery remain “underutilized.” Whether that is because of low reimbursement rates, inadequate facilities, equipment and supplies, or other issues awaits clarification.

Because the shortage of ophthalmologists is often so persistent and severe, and the logistics of reaching the rural poor so immense, some African countries (Ethiopia, the Congo, Tanzania) have periodically embarked on programs that train non-ophthalmologist cataract surgeons to meet local needs. But speeding the training and encouraging the retention of larger numbers of qualified ophthalmologists, removing barriers to their productivity, and instituting more effective systems for delivering cataract services should provide quicker returns and therefore has higher priority. Where countries decide to augment their use of non-ophthalmologist cataract surgeons, these individuals need to be trained, supervised, and their outcomes monitored by well-qualified ophthalmologist surgeons, appropriately compensated for their efforts.

The ICO is considering ways in which it might help overcome at least some of the obstacles impeding needed access to cataract surgical services provided by ophthalmologists. These may well involve gathering more information about extrinsic factors limiting ophthalmologists’ productivity, developing educational programs that promote efficiency and quality in the delivery of cataract surgical services by ophthalmologists, curricular reforms that would reduce the number of years of residency training, and advocacy for additional resources where these are limiting much-needed care.