The lens choices available to surgeons performing cataract surgery in 2010 are improvements on previous designs. Today's IOLs provide better quality of vision with reduced side effects, but we have not yet reached the nirvana of a perfect operation with the perfect lens for all situations; nor should we present any lens as such to our patients. Conversely, however, we should be careful not to undersell an excellent operation with excellent results.
Our predecessors had only the option of monofocal lenses, and the refractive outcome they aspired to was limited by the available means of biometry—mainly ultrasound Ascan, the accuracy of which was considerably more variable than today's predominant method of laser partial coherence interferometry with a surgeon-adjusted A constant. In 2010, we have the option not only of improved monofocal lenses (ie, blue-blocking, aspheric, Q-factor adjusted, and toric) but also improved predictability of the refractive outcome, which can allow us to plan monovision, mini-monovision, emmetropia, or myopia with greater accuracy.
Additionally, we are now able to choose from among a number of premium, presbyopia-correcting IOL options, including multifocal and accommodating IOLs. Deciding which patient will perform best with which lens is a complex process with many factors to take into consideration. The goal is to exclude patients who do not suit certain lenses and lenses that do not suit certain eyes. This article explores some of the factors that should go into our process of deciding on a lens choice.
PRIOR TO THE CONSULTATION
The following components of the assessment process are conducted prior to the surgeon's consultation. All are imperative to selecting the best IOL for the patient.
Identify expectations and demands. In our practice, the assessment begins when the patient enters the practice. Personnel are instructed to pay particular attention to patients' expectations and demands, which may be more forthcoming when patients are not in the presence of the doctor. The consultation maybe a stressful experience for some people, due to the large volume of information transmitted in a short time, and some patients may find it difficult to communicate their specific needs and expectations while assimilating the information presented to them.
Assess patients' priorities. Our patients complete a lifestyle questionnaire to facilitate a detailed description of their occupation and hobbies and to grade their most important visual tasks, such as reading at near, looking at a computer screen, or driving (including night driving). Extra counseling is imperative for patients who require perfect distance, intermediate, and near vision with no glare or halos. The surgeon must manage these patients' expectations so that they are more realistic. It may help to let the patient know that, as a surgeon, you share in his or her aspirations for quality of vision at all distances, but that it may not be feasible without the addition of spectacle correction or additional surgical intervention.
Choose the right lens. After I read the patient's questionnaire and receive a report from the staff member who performed the initial assessment, my first task is to exclude the unsuitable lenses. For patients with a fastidious and exacting nature, a multifocal IOL is unlikely to be suitable. If such a lens is implanted in a patient with this personality, there is potential for extra postoperative consultations in which the patient complains of glare and halos in various lighting conditions or relays what print can and cannot be read at various distances in the same fastidious manner. Likewise, those with visually exacting occupations and hobbies, such as artists, engineers, and musicians, expect a similar level of visual quality. Musicians who need to see the conductor in the distance, the sheet music in the intermediate area, and their instrument at near are not suitable for multifocal lenses. In contrast, patients with hobbies and occupations that depend on near vision and who are unwilling to wear reading glasses are not suitable for accommodating lenses.
Review clinical assessments. Before the patient sits in the consultation seat, standard assessment tests including visual acuity, refraction, topography, biometry, and Schirmer test should be performed. On review of these results, the lens choice may be narrowed before even meeting the patient. Conditions that may cause higherorder aberrations such as tear film and corneal irregularities or abnormalities suggestive of keratoconus should exclude the patient from receiving a multifocal lens. Adding a multifocal lens to a multifocal cornea, such as in a patient with keratoconus, can provide a confusing visual experience for the patient. Patients with topographic corneal astigmatism who are not eligible for limbal relaxing incisions (2.00 D or greater in my practice) would be excluded from accommodating lenses that are not available in a toric model.
Now the surgeon consultation begins. The first question I ask is, “What can we do for you?” in reply to which I normally hear, “Improve my vision please.” At this point, I phrase my reply as, “Would you like to improve your vision in the distance, the middle distance, or at near?” This implies that correction at all distances may not be achievable. This response begins to lower the patient's expectations. I usually follow up with: “While you think about that, let me look at your eyes.”
At the slit lamp, I look to see if the tear film is healthy and uniform, with good lid-wiping action enabling a smooth air-ocular interface. I also look for any deficiencies of the tear film that may create aberrations. Although such deficiencies do not preclude the use of a multifocal lens, they should be treated prior to surgery. Next, I determine if I am dealing with a healthy cornea and a normal endothelial cell count. Fuchs corneal endothelial dystrophy is increasingly common in our aging population, and it often presents concomitant with cataract. If the corneal disease is mild and the cataract more advanced, I am careful to inform the patient about the postoperative risk of irreversible corneal edema and the possibility for subsequent Descemet's stripping endothelial keratoplasty (DSEK). The lens selection must also be made with this in mind because the interface scatter caused by corneal lamellar surgery would cause problems with a multifocal IOL. I would select an aspheric monofocal lens in this case, aiming for moderate myopia to partially counter the early mild induction of hyperopia after DSEK.
In patients with prior uveitis, the accommodative response of the ciliary muscle is likely affected. Therefore, in patients with history or signs of prior intraocular inflammation (eg, synechiae or iris transillumination defects) I opt for an aspheric monofocal lens and inform the patient that, although his or her quality of vision will improve, reading glasses will be required. Similarly, for those with advanced diabetes, the use of an accommodating lens is less likely to be efficacious due to neuropathy affecting the ciliary muscle. However, the disease is not an absolute contraindication provided the patient is fully informed and willing.
For patients with diabetic maculopathy or any type of macular dysfunction such as previous central serous retinopathy, age-related macular degeneration, drusen, epiretinal membrane, or myopic degeneration, a multifocal lens is not a good option. The suggestion of such symptoms at the clinical exam should be confirmed with optical coherence tomography. The aberrations produced by multifocal lenses of any type require a perfect macula and neurological system to interpret the images appropriately. If there is any defect along this pathway, my threshold is lowered to suggest an optic with a single focal point, either accommodating or monofocal.
Patients should receive written material on the available options to read at home prior to the consultation. These messages are reinforced with audiovisual information programs, either available on our Web site or shown at our surgical center. Patients may also interact with existing patients at our seminars or in the waiting room. These educational tools and encounters will help formulate patients' perceptions of what is achievable and which product they may wish to select; however, this may be disadvantageous if patients decide upon a product not suited to them.
After determining what IOLs will not work for the patient, the surgeon must gather more information to help the patient choose the most suitable product. The final stage of the consultation should enable this conversation to happen; both sides must be clear on what outcomes are desired versus what can be achieved.
Two questions are essential to refine the choice of lens most suitable for the patient. First, I always tell the patient that, currently, no artificial lens is perfect. “None of the lenses available in 2010 can deliver perfect vision at near, to read a paper; at the middle distance, to see a computer; and at far distance, to see the television screen at the end of the room, without a compromise. Which would you prefer?” Such phrasing helps provide a context and gives the patient better understanding of what is achievable. It also helps you determine what is most important to your patient. Make sure you document the response.
The second vital question is, “Of the following—glare and halos, which may limit vision in low levels of light and may mean you cannot drive at night; needing to wear glasses to see small print at near; or needing glasses to watch TV and drive—which could you not tolerate after surgery?”
This question further excludes any unsuitable lenses, reinforces potential limitations, and helps the surgeon better understand what is most important to the patient. With the answers to these two questions, the surgeon can begin making decisions on lens choices.
BREAKING IT DOWN
For patients who will not tolerate glare and halos, multifocal lenses are immediately excluded. But for those who require good near vision, multifocal lenses are a good option.
It is difficult to choose a lens for those who will not tolerate glare but want good near vision. For these patients, there are three options: (1) create mini-monovision using an aspheric lens, with a refractive outcome of -1.00 D in one eye and emmetropia in the other; (2) implant monofocal lenses and tell the patient he or she will need reading glasses; or (3) implant an accommodating lens, which in my hands still requires reading glasses in approximately 20% of cases.
For patients requiring both distance and intermediate vision but not demanding great near vision (meaning they would accept reading glasses), I recommend an accommodating lens. I prefer a toric multifocal lens for patients with significant astigmatism who would tolerate some glare and halos and are not regular night drivers. I have found that outcomes with the AT.LISA Toric (Carl Zeiss Meditec, Jena, Germany) are superb.
I believe we are living in an exciting age for ophthalmic surgery, with advances in surgical and IOL technology providing improved outcomes and quality of life to our patients. But the old adage of under-sell and over-deliver is still relevant.
Damian B. Lake, MB, ChB, FRCOphth, is a Consultant Ophthalmologist at The CorneoPlastic Unit and Eye Bank, East Grinstead, and Centre For Sight, both in the United Kingdom. Dr. Lake states that he does not have any financial interest in the products or companies mentioned. He may be reached at e-mail: firstname.lastname@example.org.
- Patients may be more forthcoming about their expectations and demands when they are not in the presence of the doctor.
- Phrase your explanation to imply that correction at all distances may not be achievable.
- Reinforce the potential limitations of all lens designs