Presbyopia-correcting lens implants have improved over the past decade and have become an excellent option for patients who wish to reduce their dependence on glasses. However, there are a number of factors that contribute to the success of this technology. Patient education is imperative. The patient must have realistic expectations regarding the outcome of surgery and understand the limitations of the chosen lens. When these IOLs—sometimes referred to as PCIOLs—are selected appropriately, the majority of patients are satisfied with the outcome.
Lens Selection
For surgeons who are considering or just beginning to offer PCIOLs to their patients, it can be difficult to determine which model IOL to use. In the United States, our options are limited to the ReSTOR and TECNIS multifocals from Alcon and AMO respectively, and the Crystalens and TRULIGN (toric Crystalens) accommodating lenses from Bausch + Lomb. Studies in the literature support each of these specific lenses and sometimes combinations of lenses (i.e. mixing and matching lenses to maximize their strengths and minimize their weaknesses).
The multifocal IOLs consistently provide the broadest range of vision but have a higher rate of glare/halo and should be used judiciously or not at all in patients with ocular conditions that can reduce contrast sensitivity. The ReSTOR IOL is pupil dependent so in dim lighting conditions the lens is distance dominant. The TECNIS multifocal is pupil size independent and now comes in three add powers. The accommodating IOLs have less risk of dysphotopsias and do not alter contrast sensitivity, but the near vision can be quite variable. If a patient has difficulty due to side effects from a particular IOL, then a different style IOL should be considered for the fellow eye.
Patient Selection
As previously mentioned, patient selection and education is key for a “20/happy” result. Good candidates for these lenses are individuals who have realistic expectations, healthy eyes, and understand the limitations of the procedure. Once all the necessary information from the patient’s history, (lifestyle, visual needs, previous ocular surgery), exam (ocular conditions that can interfere with IOL function), and ancillary testing (corneal topography, macula OCT, etc.) is reviewed, the surgeon is able to determine the most appropriate PCIOL and then counsel the patient about side effects, potential for neuroadaption, and possible need for a laser enhancement if the refractive target is not achieved.
The target refraction should be set at emmetropia for multifocal IOLs and mini-monovision (aim -0.75 to -1.00 D in nondominant eye) for Crystalens.
Multifocal IOLs are my lens of choice because they provide the broadest range of clear vision without correction. Although some patients initially notice glare/halo from bright lights, I have found that they usually adapt to this quickly. Fortunately, I have not encountered a patient who was unable to tolerate the dysphotopsias and desired a lens exchange.
Pre-Op Considerations
In addition, it is very important preoperatively to identify any eye pathology that could interfere with the final vision, especially when considering a multifocal lens design. Ocular surface disease should be treated aggressively prior to surgery to ensure a normal tear film and accurate biometry measurements. Corneal astigmatism must be treated at the time of surgery or afterwards, because more than 0.5 D of cylinder can reduce acuity. Most surgeons agree that contraindications to multifocal lenses include irregular astigmatism (due to ectasia, scarring, or previous corneal refractive surgery), macular disease, and limited visual potential.
There has been some suggestion that patients with normal visual potential who adapt to a multifocal IOL and subsequently develop visual loss from glaucoma, macular or retinal pathology, continue to do well with the IOL. Personally, I have seen such patients and they continue to be happy with their multifocality. Therefore, in certain circumstances, I think it is reasonable to consider use of a multifocal IOL in patients with macular pathology.
In two situations, I have inserted multifocal IOLs in patients with preexisting macular pathology and these patients have been very pleased with the results. Both patients were multifocal contact lens wearers: one had residual metamorphopsia after an epiretinal membrane peel, and the other had a mild epiretinal membrane that had been stable for many years. Both patients were very happy with multifocal IOLs in their fellow healthy eyes, liked the vision with a multifocal contact lens in the eye with macular distortion and therefore wanted a multifocal IOL in that eye. In both instances, we had lengthy discussions about the possibility of poor vision and need for IOL exchange, and the patients were fully informed about the risks, benefits, and complications.
Post-Op Considerations
Success with PCIOLs also requires the ability to properly manage postoperative issues. I extend the use of a topical steroid and nonsteroidal anti-inflammatory agent so patients instill these drops for a total of 2 months after surgery in order to reduce the risk of cystoid macular edema, posterior capsular opacification, ocular surface disease, and rebound iritis. This is particularly important for patients receiving multifocal IOLs because even subtle amounts of these postoperative complications can significantly interfere with the performance of the lens.
All patient concerns must be addressed promptly. Often, the patient just requires reassurance that their symptoms are normal and will improve over time as they adapt to their new vision. For disturbing glare and halos that do not improve over time, miotic agents such as brimonidine or weak pilocarpine are usually helpful. Vision training may also be effective in special situations.
For patients with blurry vision, the treatment depends on the etiology: dry eye should be treated before and after surgery, CME that does not respond to topical therapy may require intravitreal injection, and PCO tends to occur more frequently with Crystalens and should be treated early to prevent anterior vaulting of both or one (Z-syndrome) haptic. Residual refractive error can be surgically corrected when the refraction has stabilized. If the refractive target was met but the patient notices difficulty with near vision (typically Crystalens) or computer vision (typically multifocal lens with high add), then I gently remind them of our preoperative discussion regarding the strengths and weaknesses of the lens, demonstrate what their reading vision would have been like had they chosen a basic monofocal IOL (-2.50 or -3.00 glasses), and then prescribe a pair of glasses to use when needed.
In summary, PCIOLs are an excellent option for those individuals who desire more independence from glasses. The expanded family of multifocal IOL add powers allows us to customize the near focus and reduce glare/halo depending on the patient’s preferred reading or computer distance, but patient selection and postoperative management are critical for successful outcomes.