Outcome of corneal transplantation

In their article in this issue of the BJO (p 57) Saunders and colleagues describe a methodology by which they evaluate the visual health state of patients with severe corneal disease requiring transplantation surgery. Rather than dealing with visual acuity as the only preoperative and outcome parameters, they evaluate patients according to three criteria: (1) visual acuity, (2) ocular pain, and (3) visual function. Concerning the latter criterion, visual function, they utilise a tool called the VFA (visual function assessment),¹ which they have previously described; it is essentially a modification of the VF-14² and predominantly measures ocular function characterised by the ability to perform tasks such as driving, reading, cooking, etc. They found that patients who had a high preoperative priority score, as measured by the three above criteria, were more likely to have a good outcome. One measure in the study that is somewhat unclear, though, is how the results incorporate vision in the eye that did not receive a transplant. All too often our clinical trials and other studies fail to address the status of the second eye, perhaps a factor more important to the patient that the ocular intervention itself. The authors noted that 72.4% of patients demonstrated an improved VFA after transplant, but it is uncertain whether this was measured using only the operated eye or in a real world situation in which both eyes were used during the assessment.

The authors should be congratulated upon bringing more than visual acuity alone into the decision making process. Most ophthalmologists believe that the central visual acuity is the most important factor related to the quality of life of an ophthalmic patient. And over a century of experience suggests that they are probably right. But measurement of the visual acuity alone, while it typically is the primary benchmark for most evidence based data, does not necessarily provide the best value based data.

So the question arises, what is the difference between evidence based medicine and value based medicine, or in this case, evidence based ophthalmology and value based ophthalmology? Evidence based medicine incorporates the most reliable and reproducible data from clinical studies, particularly clinical trials. Value based medicine takes clinical efficacy delineated by evidence based data one step further and incorporates the evidence to measure the actual value of the therapy to a patient.

While the concept of value based medicine may sound nebulous, it is far from it. The concept of value can be quantified by assessing the improvement in length of life and/or quality of life conferred by an intervention. For there is really nothing else we do, or should do, in health care other than improve length and/or quality of life. With ophthalmological interventions, in which death is infrequently encountered, the value of an intervention can be essentially measured by the improvement in quality of life.

Why is value important? Every society has finite scarce resources that, in the best interest of its people, should be maximised to yield the highest return. This endeavour can be quite difficult in health care, in fact impossible unless value based health care is considered. As an example, suppose a financial officer responsible for a healthcare budget at a large company poses the following question to an ophthalmologist. “Doctor, you have just told me that laser treatment for macular oedema associated with branch retinal vein obstruction improves the average person's vision from 20/70 to 20/45. What does this mean in terms of value? The cardiologists were in here just before you and said that their evidenced based therapy improves the cardiac ejection fraction from 35% to 45%. What is the comparable value of your treatment and theirs?” With evidence based data alone, the question is virtually impossible to answer. With value based data it can be answered.

How does one measure value? Saunders and colleagues have attempted one method of measuring value by incorporating visual acuity, pain, and their visual function assessment as preoperative and postoperative criteria. The latter tool measures functional ability associated with various degrees of visual loss and has been considered by some to be a quality of life measure. We're not so sure, however, that it truly measures quality of life or value. We have previously noted a high correlation between the VF-14 and visual acuity, not surprising since those with better central visual acuity can perform more intricate visual tasks. The question can then be asked, how much more do such visual function tests really tell us than the central visual acuity alone? The answer is still uncertain. But perhaps more importantly, the visual function tests (VF-14,² the VFQ-25³ from the National Eye Institute and the visual function assessment¹) most commonly used to evaluate quality of life for ophthalmological interventions are generally not applicable across other medical specialties. And as much as we like to think that health care revolves around ophthalmology, those involved with healthcare policy have a much broader picture with which to deal.

“Data indicate that our interventions in ophthalmology are highly valued by patients”

There is a tool, however, that can measure the value associated with a healthcare intervention. And it can measure it across virtually all interventions in medicine. This evaluation tool is utility analysis.⁴ Developed in the 1940s to measure uncertainty, utility analysis was applied by researchers to health care in the 1970s. By convention, a utility value of 1.0 equates with perfect health and a value of 0.0 equates with death. There are a number of variants of utility value measure; one of the more popular variants, the time tradeoff methodology, essentially involves a theoretical scenario in which a patient is asked how many expected remaining years of life he or she would be willing to trade in return for a perfect health state. The proportion of years traded is then subtracted from 1.0 to yield the utility value. For example, if a person with 20/40 vision is willing to trade 4 of 20 hypothetical remaining years in return for perfect vision, the utility value would be 1.0 − 4/20 = 0.80. Unlike many of the quality of life tools in health care that primarily measure function, utility analysis is theoretically more all inclusive in that it encompasses function, as well as other important parameters such as fear of the unknown, pain, psychological overlay, family support systems, socioeconomic status, and others. Of utmost importance is the fact that utility analysis can also be combined with the costs of an intervention in cost-utility analysis.⁵ Cost-utility analysis has the ability to assess the resources expended for the value received from an intervention and can effectively compare interventions across all healthcare fields.

Patient perceived value is a basic component in the evaluation of what we do in health care, perhaps one of the most critical. Data from ophthalmic populations to date indicate indeed that our interventions in ophthalmology^4,5 are highly valued by patients. This information is of unsurpassed importance to stakeholders in the healthcare arena: patients, decision makers, planners, and providers as well. It should indeed be gratifying to those of us in the profession that the services we perform are so highly valued by the most important people in the process, our patients.

Many in health care refer to “evidence based medicine” as a very positive progression from the more anecdotal practice of medicine 20 years ago. But those in the business world and on the cutting edge of innovation speak of value. There is little doubt that, while “evidence based medicine” was the buzz phrase of the 1990s, moving forward it will be teamed with patient perceived value and cost-utility analysis to take healthcare quality to a yet higher level, “value based medicine”—the paradigm for the 21st century.