Monofocal Intraocular Lens
At the time of cataract surgery, the surgeon replaces the cataract with an intraocular lens implant (IOL). This implant is a standard part of cataract surgery and usually involves placement of a monofocal (single focus) IOL. Most often, this is a foldable lens that is composed of acrylic material. The folded lens is inserted into the eye through a microscopic incision and is then unfolded and rotated into the correct orientation. For most people this incision is self-sealing and does not require the use of sutures (stitches). A monofocal lens has a fixed focal length, meaning the lens is in focus at a single distance. Usually the goal is either good distance or good near vision, but a monofocal lens cannot fix for both distances. This form of IOL has been used successfully for decades and has a wonderful track record. The cost of a standard monofocal lens is covered by Medicare and most third-party health insurances (aside from the applicable deductibles and co-pays) and the visual quality with glasses or contacts is unsurpassed by any other lens technology. During the preoperative evaluation, data is obtained that allows the doctor to determine the IOL power that is most appropriate for the best postoperative outcome. The doctor and the patient will decide whether the implanted lens will be for the distance or near vision focal length.
The FDA has approved the use of multifocal, accommodating and astigmatism correcting IOLs. These lenses include AMO’s ReZOOM®, Alcon’s ReSTOR®, Bausch & Lomb’s Crystalens®, and Alcon’s AcrySof® Toric IOL. These lenses offer alternative focusing characteristics that may benefit some patients, however, they are not covered by insurance and in some cases there are additional risks. The difference between these lenses and the standard IOL is that they are likely to decrease the amount an individual relies upon glasses after cataract surgery.
The fastest growing type of IOL in this category is the TORIC®. This IOL helps to minimize, and in some cases eliminate, the amount of astigmatism allowing patients with astigmatism to have improved uncorrected vision after cataract surgery. In virtually all cases, patients who have corneal astigmatism will see better without glasses if they use the TORIC IOL than if they had chosen the standard monofocal IOL. There is not significant added risk to cataract surgery when using the TORIC IOL, therefore, ophthalmologists and patients alike have embraced this technology and are using it more and more frequently, despite the added cost.
ReSTOR Multifocal IOL
The ReStor® and ReZOOM® IOLs act similarly to a bifocal contact lens; therefore, helping to correct both the distance and near vision. However, these lenses focus light at multiple distances simultaneously which can degrade vision quality and result in halos and difficulty with night vision. For some patients, this compromise is worthwhile but many prefer the superior quality of vision achieved with a standard monofocal lens, understanding they will rely on glasses more often for reading.
The Crystalens® is an accommodating lens that moves within the eye to allow for better focus at near, intermediate and distance vision ranges. Generally the quality of vision with the Crystalens is good and the depth of field is superior to that obtained with a standard monofocal lens. The depth of field is not as great as would be ideal; however, therefore many patients still require reading glasses after Crystalens implantation. The greater concern, however, is that the Crystalens, by virtue of its movement, has the potential to move into undesirable positions and therefore in rare instances, results in increased glasses dependence or mechanical complications requiring removal. The majority of patients, however, will have successful outcomes with improved depth of field compared with a monofocal lens implant.
If a patient is identified as a good candidate for one of the above mentioned alternative lenses, the surgeon and the patient will decide which lens choice is optimal for his/her desired postoperative outcome. It is important to understand that these lens options are not covered by Medicare or other third-party health insurance policies. Therefore, additional fees do apply. Prior to surgery the doctor and patient will determine which lens is most appropriate for a given patient.
It is the job of the surgeon to assist the patient in making an informed decision regarding which IOL to select for implantation during cataract surgery. It is helpful to know that all lenses, both standard monofocal and the alternative lenses mentioned above, will most likely result in improved best corrected vision and better quality of life following cataract surgery.