Intraocular Lenses for Cataract Surgery

What Is the Issue? A cataract is an opacity of the lens and is the leading cause of reversible visual impairment worldwide. There are no medical treatments for cataracts but surgical procedures that replace the lens with a synthetic lens (called an intraocular lens [IOL]) have shown to be effective for restoring vision. Premium lenses, including lenses to correct astigmatism (called toric lenses), are available but may not be covered by public or private health plans. Given that there is an increased cost associated with toric lenses, there is a need to evaluate their effectiveness compared to other available corrective options, including glasses. What Did We Do? To inform decisions about the appropriate use of astigmatism-correcting IOLs, CADTH sought to identify and summarize literature that evaluates the clinical effectiveness of toric lenses against other corrective options. An information specialist conducted a search of peer-reviewed and grey literature sources. One reviewer screened citations, and selected and critically appraised the included studies. What Did We Find? One systematic review (SR), 3 randomized controlled trials (RCTs), 1 prospective nonrandomized study, and 6 retrospective nonrandomized studies were identified that evaluated the clinical effectiveness of toric versus nontoric IOLs implanted during cataract surgery, including 1 with a pediatric focus. Toric IOLs may be better than nontoric IOLs for postoperative astigmatism, but this may be dependent on the measurement of astigmatism evaluated (e.g., corneal astigmatism, residual refractive astigmatism, subjective refraction astigmatism, autorefraction astigmatism, spherical equivalent astigmatism, cylinder astigmatism, surgically induced astigmatism). Toric IOLs may be better than nontoric IOLs for postoperative uncorrected visual acuity (VA), but it is unclear if this results in a clinically meaningful difference to the patient. None of the studies reported on spectacle independence. Patient-centred outcomes were seldomly reported across the studies, and rarely used validated tools, making it difficult to conclude if there were patient-centred outcome differences between toric and nontoric IOLs. Harms were reported across the studies through intraoperative complications, postoperative complications, and adverse events. Postoperative complications were statistically higher in the toric group in the SR, but there were not statistically significant differences in harms reported in the primary studies. What Does it Mean? It is difficult to draw conclusions across the studies and outcomes due to the variation in how outcomes were reported or because few studies report on these outcomes. A proposed minimum set of core outcomes for cataract surgery was published in 2015. The studies included in this report did not align with this minimum set of outcomes. For example, as VA is not synonymous with improved visual functioning for patients, evaluating patient-reported visual functioning with a patient-reported outcome measure (PROM) tool is part of the minimum set of core outcomes. Future research should incorporate core outcomes, including PROMs. Although toric IOLs statistically improved uncorrected VA, when compared to nontoric lenses, statistical significance does not imply a difference that is clinically meaningful to a patient.