Evaluating the current procedures for presbyopia correction

This month’s column looks at contact lens monovision, CK, multifocal IOL, diffractive-multifocal IOL and accommodating IOL.

Issue: September 1, 2004

ByWilliam F. Maloney, MD

We continue with part 2 of our consideration of the approaches to pseudophakic correction of presbyopia. In the last column, I mentioned that, for me, the surgical correction of presbyopia has developed into a broad-ranging approach, utilizing one of several alternative techniques selected according to each patient’s reading vision needs. I have learned that our task is not to eliminate a fixed amount of presbyopia, but rather to restore the particular segment of near focus that is of most concern to each candidate.

Some presbyopes want a result that restores small-print reading such as for stock listings, while others seek only social reading such as a restaurant menu. At this stage, such a moving target requires more than one approach. There is no universally suitable outcome because of widely varying reading needs. Therefore, the targeted result, in accordance with a set of individual factors, ought to determine the procedure selected. There is no one-size-fits-all approach.

Until we achieve a cure that fully restores the dynamic, seamless, infinite range of autofocus once experienced with natural accommodation, we will be required to deal in the art of selecting the best compromise with our presbyopia treatments.

$OSN Lens-Based Refractive Surgery [logo]$ In this effort, we regularly use a preop questionnaire, a series of preop tests and the focus zone chart (Figures 1, 2 and 3) to determine each patient’s individual presbyopia profile. The focus zone chart assures that the patient is an integral part of selecting the desired outcome as well as the inherent compromise involved in the procedure selected.

Now let us look at how we might use the information from these three tools in selecting the best procedure among those currently available or soon to be in use: contact lens monovision, conductive keratoplasty, multifocal IOL, diffractive-multifocal IOL, accommodating IOL and pseudophakic monovision (blended reading vision implants).

Figure 1. Custom focal lens implants

Figure 2. Custom focal implants preop assessment

Figure 3. Focus zone chart

Source: Maloney WF

Partial presbyopia treatments

The first differentiation is between patients with partial presbyopia and full presbyopia.

Absent high ametropia, partial presbyopes with a useful amount of accommodative amplitude still available to them are generally not candidates for pseudophakic correction. These younger, “entry-level” presbyopes (typically age 38 to 45 years) are nevertheless often very good candidates for either contact lens monovision or CK. Either of these procedures can supplement the range of accommodation that remains and satisfy most of these patients until they become more fully presbyopic and thus appropriate candidates for one of the pseudophakic treatments.

Contact lens monovision

Favorable Profile Factors:
This is the only non-spectacle alternative for those with an aversion to any surgical procedure. It is highly suitable for patients with a questionable adaptability profile since it is totally reversible. Since the correction is readily increased, it is ideal for very early presbyopes. It is also a good alternative for those with significant ametropia.

Unfavorable Profile Factors:
Intolerance to contact lenses and dry eye syndrome are relative contraindications here. Corneal astigmatism greater than 1.5 D will reduce corrected acuity for both distance and reading unless toric lenses are used. Large pupils in those who regularly drive at night are also a potential problem. Distortion and halos from headlights can be a difficulty in the reading eye, especially for women in this age range whose scotopic pupils can still be quite large. Nevertheless, I would encourage surgeons to provide any interested candidate with a bona fide trial, given the reversibility of this approach. Many motivated patients will adapt to these compromises or be willing to wear spectacles for night driving in order to read without glasses or bifocals.

CK

Favorable Profile Factors:
Near emmetropic early- to mid-presbyopes who do not require distance correction and primarily want social reading (zone 2) are the best CK candidates. More experienced CK surgeons can usually correct somewhat more presbyopia as well as up to 1.5 D of hyperopia in the distance eye in order to minimize the interocular focus difference and also improve uncorrected distance focus.

Unfavorable Profile Factors:
Corneal pathology and corneal astigmatism greater than 1.5 D are relative contraindications. Night driving is again a potential problem due to defocus blur and halos in the reading eye, especially with large scotopic pupils. Look in particular for specific activities that require uncompromised distance acuity such as aviation or activities that require fine stereo acuity. When these potential problems are a concern, a 2-day contact lens trial will generally tell whether or not the patient will adjust to CK monovision.

I have found that most early presbyopes, even those with a preconceived aversion to contact lenses, typically do quite well with non-spectacle treatments. Remember that monovision and CK will most often be a temporary solution. When patients experience one of these early corrections for presbyopia, typically they remain highly motivated to maintain their freedom from reading glasses or bifocals. These patients will be ideal candidates for one of the pseudophakic treatments once they are fully presbyopic.

Full presbyopia treatments

Each of these procedures to treat full presbyopia is used for both RLE candidates and cataract patients who elect optional presbyopia correction at the time of their cataract surgery.

Multifocal IOL

Favorable profile factors:
Hyperopic presbyopes who want social reading (zone 2) are the best candidates for the Advanced Medical Optics Array IOL. This is one treatment modality in which a large pupil is not detrimental since there is typically less than 0.75 D of pseudophakic monovision utilized. This minimal degree of interocular IOL power difference makes the Array a logical choice for candidates who demonstrate a low interocular defocus threshold (less than 1.5 D).

Unfavorable profile factors:
Patients who need consistent zone 1 reading capability or who regularly read without glasses are generally not good candidates unless at least 0.5 D of myopia is targeted for the reading eye. Since a multifocal IOL presents both eyes with a new and different “vision system,” the adaptation process is more than just blur suppression. Adaptation usually occurs over a period of months. Therefore, patients with a low neuroadaptation profile or who are impatient may not be candidates.

Diffractive-multifocal IOL

I have no firsthand experience with the Alcon ReStor IOL thus far. Therefore, my thoughts here are solely based on preliminary reports from others. The early indications are that the ReStor IOL can consistently deliver zone 1 reading acuity. If so, we need to learn if this stronger magnification comes at the expense of the zone 2 focus range. This is what we experience with bifocals and the reason why some patients need trifocals, so it is a reasonable question. Whether or not this is the case, this IOL may be a valuable addition for those who seek zone 1 reading, especially if they also seek uncompromised far distance (zones 4 and 5).

Favorable profile factors:
Hyperopic presbyopes with low interocular defocus threshold who seek zone 1 reading may be the best candidates for this IOL. However, we need more information about the reduction, if any, on zone 2 focus before we know which patients are best suited for this modality. Large pupils will presumably favor this IOL, as with the Array.

Unfavorable profile factors:
If zone 2 reading is diminished, then patients who seek both zones 1 and 2 will likely do better with pseudophakic monovision. In addition, if the neuroadaptation process is the same as with the Array IOL, then the same caution concerning candidates with low neuroadaptation capability will apply.

Accommodating IOL

I have no firsthand experience with the eyeonics Crystalens IOL yet. I have, however, reviewed all the available data and the minutes from meetings with the FDA panel (incidentally, a fascinating read) in an attempt to get a solid understanding of where this new technology may fit in relation to the alternatives.

We are going to come back to a more detailed consideration of the accommodating IOL in a future column. So far, my general impression, and that of several of the first European investigators of this IOL, is that the accommodative lens does not consistently provide zone 2 and almost certainly not zone 1 focus without the accommodative effect of pseudoaccommodation together with some degree of pseudophakic monovision accomplished by targeting the reading eye for some degree of myopia.

At this early stage, as we attempt to assess the advantages and disadvantages of the accommodating IOL over the modalities we are already using, it is not enough to tell us that patients with an accommodating lens can “read.”

If we are to say “yes” to the accommodating IOL, then we must also say “no” to one of these other modalities, each of which has also allowed the right patients to “read.”

In my view, we simply need to know more before we can say “yes” to an accommodating IOL on behalf of a given patient. We need to know what specific range of reading focus this IOL can deliver reliably, and we need to know the compromises inherent in this IOL. We need to know what degree its accommodative effect results from the 1 D to 2 D of pseudoaccommodation associated with a standard IOL, and we need to know what role, if any, monovision is playing here. Only then can we know which candidates to point in this new direction and thus correctly say “no” one of these alternatives.

Next month

In part 3 of this series, we will look at the last approach currently on our list of presbyopia treatments — pseudophakic monovision, or as I usually refer to it, blended reading vision implants.

For Your Information:

William F. Maloney, MD, an associate clinical professor at the University of California, Irvine, and head of Eye Surgery Associates, of Vista, Calif., is a well-known teacher of cataract and lens-based refractive surgery techniques. He can be reached at 2023 West Vista Way, Suite A, Vista, CA 92083; 760-941-1400; fax: 760-941-9643; e-mail: MaloneyEye@yahoo.com. Dr. Maloney has no financial interest in any ophthalmic product, and has no financial relationship with any ophthalmic company.