Intraocular Lens - Accommodating IOLs

Accommodating IOLs

One of the major disadvantages of conventional IOLs is that they are primarily focused for distance vision. Though patients who undergo a standard IOL implantation no longer experience clouding from cataracts, they are unable to accommodate, or change focus from near to far, far to near, and to distances in between. Accommodating IOLs interact with ciliary muscles and zonules, using hinges at both ends to “latch on” and move forward and backward inside the eye using the same mechanism as normal accommodation. These IOLs have a 4.5-mm square-edged optic and a long hinged plate design with polyimide loops at the end of the haptics. The hinges are made of an advanced silicone called BioSil that was thoroughly tested to make sure it was capable of unlimited flexing in the eye. There are many advantages to accommodating IOLs. For instance, light comes from and is focused on a single focal point, reducing halos, glares, and other visual aberrations. Accommodating IOLs provide excellent vision at all distances (far, intermediate, and near), project no unwanted retinal images, and produce no loss of contrast sensitivity or central system adaptation. Accommodating IOLs have the potential to eliminate or reduce the dependence on glasses after cataract surgery. For some, accommodating IOLs may be a better alternative to refractive lens exchange (RLE) and monovision.

The FDA approved Eyeonics Inc.’s accommodating IOL, Crystalens AT-45, in November 2003. Bausch & Lomb acquired Crystalens in 2008 and introduced a newer model called Crystalens HD in 2008. Crystalens is the only FDA-approved accommodating IOL currently on the market and it is approved in the United States and Europe.

Studies and peer reviews

In a September 2004 FDA trial involving 325 patients :

• 100% could see at intermediate distances (24" to 30") without glasses; the distance for most of life's activities
• 98.4% could see well enough to read the newspaper and the phone book without glasses.
• Some patients did require glasses for some tasks after implantation of the crystalens
• Vision was restored to 20/40 or better in 88% of patients compared to 35.9% of patients who received normal IOLs.

• In 2006, a 12 month study by Cummings et al. investigated contrast sensitivity and near visual acuity in patients who had received a Crystalens AT-45 versus those who received a standard IOL. Effectiveness was measured in terms of near, intermediate, and distance visual acuities and safety was evaluated by assessing complications. The study concluded that contrast sensitivity was not reduced compared to those receiving standard IOLs and provided good visual acuity at all distances in pseudophakic patients. There were no adverse complications reported. However, this study lacked a long-term follow up.
• Pepose et al. (2007) tested the combination of a multifocal IOL in one eye and an accommodating IOL in the other eye. The group found that any combination of Crystalens in one or both eyes was better for intermediate vision. ReSTOR (multifocal IOL) is better for near vision. The Crystalens and ReSTOR combination had better mean intermediate and near vision overall.
• Macsai et al. (2006) conducted a multicenter, nationwide study evaluating the visual outcomes of 112 cataract patients implanted with Crystalens IOL (n=56) versus standard monofocal IOLs (n=56). The Crystalens group demonstrated significantly better visual acuity compared to the monofocal patient group, as well as better distance and near vision 6 months post-operation.
• In overall FDA clinical results on uncorrected binocular vision in 124 patients, 92 per cent had distance vision of 20/25 or better, 98 per cent had intermediate vision of 20/25 or better, and 73 per cent had near vision of 20/25 or better 11 to 15 months after surgery. In addition, 73.5 per cent either did not wear spectacles or wore them most none of the time.
• Sanders et al. (2007) published visual performance results after Tetraflex accommodative intraocular lens implantation. They found that 6 months post-operatively, all patients had at least 1 diopter of accommodative amplitude. At 6 months, 92.2 per cent of eyes had 20/40 or better uncorrected distance visual acuity (UCDVA) and 50.6 per cent of eyes achieved 20/20 or better UCDVA. At near, 48.1 per cent of eyes achieved 20/40 or better uncorrected near visual acuity.
• However, at this time, there no long-term, well-designed clinical trials to support the accommodating technology of the Crystalens IOL.

Criticisms

• The main concern with accommodating IOLs is that there are no long-term, large-scale studies involving its use in patients. Such clinical studies using objective measurement techniques must be done to fully support the claim that accommodating IOLs can restore accommodative vision to the presbyopic eye.

• Though it is rare, potential complications include capsular bag contraction and posterior capsule opacification.

• It is more difficult to implant an accommodating IOL (due to the attachment of hinges) and recovery time may be longer than with a standard IOL.

• Patients should expect that his or her accommodative abilities will not be restored to perfect or near perfect function. Though vision is significantly improved, the degree of improvement will not be the same for all and some will still need glasses after surgery.

• Accommodating IOLs are expensive. Insurance companies do not cover these technologically advanced IOLs because long-term efficacy is still being determined.

• Older patients may not have the muscle strength to fully accommodate with the IOL. The longer the patient has compensated for presbyopia with reading glasses, the weaker the muscles used in accommodation are likely to be. If the patient cannot fully accommodate, reading glasses will still be needed.

Candidates

Generally, patients over 50 with cataract problems and no serious eye diseases are good candidates for the procedure. The patient must have functional ciliary muscles or zonules for haptics positioning. In addition, the pupils must dilate adequately, as the IOL will induce glares in low-light environments if the pupils dilate too large. Accommodating IOLs are beneficial not only for patients with cataracts, but also those who wish to reduce their dependency on glasses and contacts due to myopia, hyperopia and presbyopia.

Post-operative care is similar to that of normal IOLs. However, patients must include ophthalmologic exercises such as puzzles and word games as a part of their daily regimen in order to tone up their ciliary muscles and attain the maximum benefit from the accommodating lenses. These exercises should be done consistently for 3–6 months and the patient's performance monitored by their eye care professional.

Other promising multifocal/accommodating IOLs currently in clinical trials include Accommodative 1CU (HumanOptics, Erlangen, Germany), Smartlens (Medennium, Irvine, CA), and dual optic accommodating lenses such as Sarfarazi (Bausch and Lomb, Rochester, NY) and Synchrony (Abbott Laboratories, Abbott Park, IL).

Synchrony IOL is anticipated to receive FDA approval in 2012.