Guidance
2 The procedure
2 The procedure
2.1 Indications and current treatments
2.1.1 A cataract is the opacification of the eye's natural lens, usually causing gradual eyesight deterioration and potentially leading to blindness.
2.1.2 Current treatment involves replacing the opacified lens with an artificial lens, which is usually of fixed power (monofocal); this requires patients to use spectacles for near vision. IOLs have been developed that aim to give uncorrected vision (without spectacles), either because they are multifocal or because they have the capacity to change shape within the eye, in a similar manner to the native lens (accommodating lenses) (see section 3.1).
2.2 Outline of the procedure
2.2.1 The surgical procedure is the same as that of a cataract operation but involves implanting a multifocal IOL. Multifocal IOLs have different areas of refractive powers, allowing near and distant objects to be focused on the retina simultaneously, with the brain selecting out the required image for attention. Various devices can be used for this procedure. Cataract surgery is usually performed under a local anaesthetic.
Sections 2.3 and 2.4 describe efficacy and safety outcomes which were available in the published literature and which the Committee considered as part of the evidence about this procedure. For more details, refer to the Sources of evidence.
2.3 Efficacy
2.3.1 In a systematic review of 10 randomised controlled trials (RCTs), dependence on spectacles was reported to be 68% (316/467) and 95% (383/404) in multifocal and monofocal IOLs, respectively (odds ratio [OR] 0.17, 95% confidence interval [CI] 0.12 to 0.24). A non-randomised controlled trial of 280 patients reported that 92% and 80% of patients with multifocal and monofocal IOLs, respectively, did not need spectacles in the intermediate range (p = 0.004) (absolute numbers not reported). A second non-randomised trial of 495 patients reported more frequent spectacle independence with multifocal IOLs compared with monofocal IOLs (80% vs 8%; p < 0.0001).
2.3.2 The non-randomised controlled trial of 495 patients reported better uncorrected near visual acuity with multifocal IOLs (0.02 ± 0.12 logMAR) than with monofocal IOLs (0.41 ± 0.18 logMAR) (p < 0.0001). A further non-randomised controlled trial of 102 patients reported uncorrected distance acuity ≥ 20/40 and near acuity of Jaeger line 3 text ('J3') or better in 77% (78/101) and 46% (46/101) of patients with multifocal and monofocal IOLs, respectively (p < 0.0001). A case series of 671 patients reported distance acuity ≥ 20/40 and near acuity of J3 or better in 50% of multifocal IOL patients in the absence of preoperative pathology and postoperative macular degeneration.
2.3.3 Two of the RCTs included in the systematic review reported a statistically significant increase in patient overall vision satisfaction with multifocal IOLs compared with monofocal IOLs; two other RCTs reported no difference.
2.3.4 The Specialist Advisers considered key efficacy outcomes to include spectacle independence, uncorrected near and distance vision, postoperative refractive error, contrast sensitivity and quality of life.
2.4 Safety
2.4.1 In four RCTs in the systematic review, significantly more patients reported halos and glare with multifocal IOLs than monofocal IOLs (OR 3.55, 95% CI 2.11 to 5.96). A non-randomised controlled trial of 18 patients reported that photic symptoms occurred in 61% (11/18) and 39% (7/18) of eyes treated. The non-randomised controlled trial of 495 patients reported no significant differences in glare score between patients with multifocal IOLs and monofocal IOLs (0.80 points vs 0.93 points; p = 0.0824). In the systematic review, two RCTs reported decentration of multifocal IOLs in 8% (3/39) and 12% (3/25) of patients, respectively.
2.4.2 A non-randomised controlled trial of 40 patients that included these outcomes reported posterior capsule opacification requiring treatment in 29% (7/24), 25% (8/32) and 13% (3/24) of patients treated with bifocal, multifocal and accommodating IOLs, respectively, at 1 year (level of significance not stated). In a case series of 72 patients (97 eyes) treated with multifocal IOLs, laser capsulotomy was required in 56% (54/97) of eyes, at a mean follow-up of 34 months.
2.4.3 The Specialist Advisers considered key safety outcomes to include dysphotopsia and the need for replacement of multifocal IOLs with either multifocal or monofocal IOLs. They listed adverse events to include problems with intermediate vision, reduced contrast sensitivity, halos, glare, 'waxy vision' and reduced tolerance to astigmatism.