11 Premium Intraocular Lenses and Associated Problems

Before diving into the benefits and limitations of various premium IOLs, it is important to note a certain level of dissatisfaction with monofocal IOLs. Several studies have shown monofocal control groups to reveal a few noteworthy subjective outcomes. It has been reported that 3 to 8% of patients implanted with monofocal IOLs were found to have enough uncorrected near vision to read newspaper print. At the other end of the spectrum, results from several studies have reported incidence of positive dysphotopsias, such as glare, halos, and the night vision symptoms, despite not being graded as severe. Negative dysphotopsia is also a well-recognized and clinically frustrating photopsia, which occurs in patients who have received monofocal IOLs, and this manifests as temporal “crescent” of “missing vision.”1 There are two groups of presbyopia-correcting IOLs that are more widely utilized: accommodative and MFIOLs. While there are certain side effects and complications that are unique to their respective IOL designs, the overall approach to the assessment and management of the less-than-satisfied postoperative patient is a similar one.

Accommodative IOLs have been on the market for over 10 years, and have embraced the philosophy drawn out by the Helmholtz model of accommodation. The design and purpose of accommodative IOLs, such as the Crystalens, Tetraflex, and the 1 Component Unit (1CU) was to make an IOL pliable enough to bend and be displaced forward as the eye responds to its natural tendency to accommodate. The displacement forward would theoretically allow a pseudoaccommodative state, increasing the effective power of the lens, to address intermediate and near vision, and Heatley et al did an excellent job, mathematically demonstrating how 1-diopter accommodation could be achieved with an increase in effective pseudoaccommodation.2 A recent study using anterior segment imaging demonstrated axial shifts of the accommodating IOL were small, and in many cases the lens shifted backward on accommodative effort.³ A similar study used ultrasonic biomicroscopy (UBM) technology and showed a mean accommodative amplitude of 0.44 ± 0.24 diopters, which was calculated to be a range of accommodation approximately 0.25 to 0.75 diopters.⁴ This may clinically translate to variable amounts of near vision postoperatively, and a patient experiencing a lack of adequate pseudoaccommodative amplitude could certainly lead to dissatisfaction. Such inconsistent near vision outcomes were demonstrated by a large meta-analysis that reviewed four randomized clinical trials (RCTs) with the 1CU and the AT-45 IOLs, where considerable heterogeneity of effect was seen, with near vision ranging from 1.3 to 6 Jaeger units and 0.12 logMAR improvement.⁵

The shear design of accommodative IOLs does limit the degree of dysphotopsias, such as glare, halos, or starbursts. Takakura et al reported a large meta-analysis that reviewed two RCTs, each demonstrating no significant difference in glare or contrast sensitivity.⁶ With such a sound optical system, and toric options available, accommodative IOLs are excellent options for the patients who value uncorrected distance visual acuity (UCDVA) and who understand their uncorrected near visual acuity (UCNVA) may be limited and who do not want to risk having other secondary optical dysphotopsias. From the surgeon’s perspective, a low incidence of posterior capsule opacification and capsular fibrosis is crucial, as both can be a long-term detrimental factor for near vision needs in accommodating IOLs, not to mention what is known as Z syndrome. In Z syndrome, the capsule contracts and causes compression along the haptic–optic axis, resulting in asymmetric folding. The asymmetric vaulting of the lens resembles a Z, and results in tilting of the optic, which can lead to coma aberration, increased myopia, and increased astigmatism. For subtle cases and a high index of suspicion, diagnostic equipment, such as the NIDEK OPD III or iTrace, may help determine IOL tilt or Z syndrome. Capsular bag rigidity limits axial movement of the IOLs and therefore reduces accommodative capacity. An early posterior capsulotomy after postoperative 1 month has been advocated to prevent unwanted complications from capsular fibrosis. If a Z syndrome does occur, strategic neodymium:yttrium aluminum garnet (Nd:YAG) laser dissection of the anterior and/or posterior capsule, or even placement of a capsular tension ring, can effectively alleviate this complication.⁷

Regarding MFIOL technology, until 2005, they were designed with strictly refractive technology. This design had its limitations, and along came the first diffractive lenses, which have continually evolved. Complaints of glare and halos with night driving with earlier iterations were common, and this has continued to improve with refinements such as aspheric transitions between optical zones.⁸ Regardless of the dysphotopsia, UCNVA became attainable. Fortunately, newer generation low-add multifocals have led to decreased unwanted night vision dysphotopsias^9,10 and greater quality of overall vision, and have improved intermediate visual acuity. Several studies have shown less dysphotopsias, in the low adds compared to their respective 4.0 add models.¹¹ The subjective complaints of MFIOLs are of no surprise, as several objective studies have predicted these phenomena. There is overall significantly improved postoperative satisfaction in patients with + 2.75 or + 3.25 diopter add than those with a + 4.00 diopter add.¹²

The low-add multifocals can effectively provide both intermediate and near vision needs, and patients with the lowest add MFIOL can achieve significant spectacle independence.^9,10,13 Combining different strength MFIOLs can lead to greater near vision satisfaction. Mastropasqua et al reported a prospective nonrandomized single-blind observational study where patients received either the Restor SN6AD1 + 3.0 diopter lens or the Restor SV25T0 + 2.5 diopter lens in either eye, or one of each. The National Eye Institute’s Refractive Error Quality of Life instrument (NEI RQL42) questionnaire showed that combining the different IOLs produced better results in terms of expectations and activity limitations, while contrast sensitivity showed no difference between groups.¹² With any MFIOL, understanding our patient’s needs and requirement for near vision versus intermediate vision can be the difference between a 20/20 happy patient and a 20/20 unhappy patient.

A recent retrospective study reviewed a large group of patients who presented after either MFIOL implantation or an accommodative IOL placement. The chief complaint of 29 (59%) patients was blurry vision, both for distance and near; this was seen in 50 eyes (68%).14 An in vitro study by Vega and colleagues demonstrated that various MFIOLs could still lead to unwanted dysphotopsias. The SV25T0 + 2.5 had smaller but more intense halo formation than the ZKB00 + 2.75. The SV25T0 + 2.5 also showed a deceased halo size, but increase in intensity with an increase in pupil size from 3.0 to 4.5 mm ( Fig. 11.1).^15,16

Fig. 11.1 This is an in vitro simulation of oncoming headlights in a 5-mm pupil of two multifocal intraocular lenses (MFIOLs) with different add-ons. As demonstrated by the images, the IOL with the stronger add power, ReSTOR 3.0, has a wider halo and glare profile than the weaker low-add ReSTOR 2.5.

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