Cataract appropriateness tightrope

From a clinical perspective, a patient should have the right to a procedure if after being informed of the potential benefits and risks, he or she and the clinician both agree that the benefits outweigh the risks for that particular situation. Such decision making needs to be tempered by the fact that both clinicians and patients can overestimate benefits and underestimate risks of interventions for a variety of reasons.

From the perspective of public funding, the benefit versus risk bar may be higher than from a clinical decision-making perspective, and this should be determined at the societal level. The most common scenario where clinical and public funding appropriateness may differ is for refractive benefits of cataract surgery, which are most pronounced in presbyopic patients with a high prescription. In many societies, refractive outcomes have been placed (somewhat arbitrarily) in the cosmetic realm instead of in the medically necessary realm. Working under the premise that refractive benefits are not medically necessary, it is not clear whether the publicly funded system should be responsible for paying, and as such, a definition of a visually significant cataract is therefore desirable. We then need to be able to measure improvement after removal of this visually significant cataract, which is unfortunately quite difficult to parse out from the refractive benefit, at least functionally.

The definition of cosmetic versus medically necessary is difficult across all of medicine. For instance, mole removal in Ontario is only covered for “cancerous” lesions, without regard for cosmetic implications. An elderly patient could have a small, slow-growing, reasonably benign peripheral basal cell carcinoma removed on the taxpayers’ dime, yet a child may not receive complete coverage for a cleft lip and palate repair. Correspondingly, patients with mild cataracts, whose main complaint could actually be dry eyes, with anticipated modest visual gain, could have it removed on the taxpayers’ dime. Yet highly hyperopic patients intolerant of contact lenses who are legally blind when their glasses fall off are expected to pay out of pocket for refractive corneal laser surgery or refractive lens exchange. Both the quality and visual acuity through glasses can be limiting compared with a corneal or intraocular solution—so limiting that these individuals may not be eligible for particular vocations. However, from a societal perspective, we take no responsibility to help them. We should not minimize the refractive benefits of cataract surgery but instead celebrate and value them.

The first question is, which vision? Traditionally, high-contrast visual acuity as measured in a doctor's office has been our surrogate for “vision,” and often the higher the contrast, the better is the vision. However, this measurement can be a poor surrogate for activities that are important to patients, such as reading and driving at night. A common example is a posterior subcapsular cataract, where although the high-contrast visual acuity can still be quite good, the patient can have debilitating glare. Even accepting high-contrast visual acuity despite its limitations, we have to also address the refractive element. As discussed earlier, even significant deficits in uncorrected visual acuity are perceived as cosmetic. Best-corrected visual acuity is often considered in defining appropriateness, though it does not represent functional vision for many people. For instance, a common phenomenon that occurs as the cataract develops is a progressive myopic shift, where a patient's prescription becomes progressively nearsighted over time, requiring frequent and expensive assessments/updates of glasses. The pinhole variant of best-corrected visual acuity can actually be better than the vision achieved with a pair of glasses because it can mask astigmatism and higher-order aberrations. The best functional high-contrast visual acuity would be “habitual,” which is the current glasses prescription a patient has been using as they develop their cataract.

Another limitation of high-contrast visual acuity arises because of the increasing role of lens-based surgery for angle-closure glaucoma, which is performed more and more on patients with minimal cataract and intact central vision. Mounting evidence suggests that early and pre-emptive lens-based surgery can be more effective in reducing irreversible glaucomatous vision loss than laser peripheral iridotomy with observation or more invasive filtering surgery procedures.

There has been increased interest in patient-centred outcomes in guiding medical decision making; our own research has suggested discordance between patient-reported outcomes, visual acuity, and physician expectations. A measured approach to appropriateness likely includes carefully collected habitual visual acuity, patient-reported outcome measures, and some physician clinical discretion.

How to address appropriateness of the second eye is a matter of much debate. Traditionally, the eye with the worse visual acuity undergoes cataract surgery first. For many patients, this worse-eye intervention would largely correct most of their functional deficit, notwithstanding some potential limitations in binocular visual function. Relying solely on patient-reported outcomes would intentionally delay second-eye cataract surgery that is largely inevitable, though it could be considered in prioritization planning. An exception to this is patients with high refractive error, who suffer from prism and magnification differences between the two corrected eyes; these complaints should come out in carefully designed patient-reported outcome instruments.

In summary, we would differentiate privately funded and publicly funded cataract surgery appropriateness and also exercise caution in applying rigid high-contrast visual acuity cut-offs for cataract surgery appropriateness. Appropriate models should involve shared decision making between patients and clinicians, and measurement tools should incorporate objective clinical criteria and reproducible patient-reported outcome measures.

The authors have no proprietary or commercial interest in any materials discussed in this article.