Try This 5-Step Program
BY JEROME S. LIEBLEIN, O.D.
More presbyopes should be wearing multifocals. Improve your numbers with this simple guide.
A contact lens specialist and internationally known lecturer, Dr. Lieblein is in private practice in San Diego.
Not long ago, Dr. Gerald Lowther noted that many spectacle-wearers say they haven't tried contact lenses because their practitioner hasn't suggested them, so they assume contact lenses must not be suitable for them. "Trends in Lens Care 1995" reported that only 20 percent of the patients who wear spectacles have discussed contact lenses with their doctors.
According to some reports, there are 80 million presbyopes in the United States and that number is increasing at a rate of five million people a year. In the first quarter of 1994, the number of patients wearing multifocal contact lenses increased 22 percent over the previous year. Still, the over-40 population accounts for less than 20 percent of the total number of contact lens wearers, and the total multifocal population is only one percent of the contact lens market.
EVALUATING THE MATURE CONTACT LENS CANDIDATE
We know we must consider a patient's physical characteristics as well as acuity, occupation and motivation. When evaluating presbyopes, we must also factor in the ocular changes due to aging as well as the fact that some of these older patients may be taking medications that could affect their success with contact lenses.
As we mature, tear production decreases and there is a loss of goblet cells that keep the eye moist. This increasing dryness can increase deposition on the lens surface. The corneal changes that are due to metabolic activity of the presbyope combined with the increased thickness of a multifocal contact lens require an increase in the permeability of the lens. We must use materials that promote better exchange of gases, and then monitor the cornea for hypoxic changes that could signal lens intolerance.
Simultaneous and alternating designs function basically the same way in soft materials as in gas permeable materials. With simultaneous designs, both distance and near are superimposed, and the brain selects the image that's in focus. Comfort is good. Rotation is not a problem, and prism is not required.
With alternating designs, distance is viewed through the upper portion of the lens and the near segment must move up for reading. Lens position is lower lid-dependent, and the upper lid induces the translation. Rotation can be a problem, so prism is incorporated to stabilize the lens. Vision is very clear and sharp.
Deciding on the proper design seems to create the most confusion. You can't choose one brand and apply it to every patient. Diagnostic sets will help you determine the most effective design for each patient. Many manufacturers offer a 100 percent guarantee on the return of lenses, and in fact, I won't use a lens that's not guaranteed. This allows you to order the first lens as a diagnostic lens and evaluate the dynamics of vision, movement and position more accurately. This first lens becomes your 'trial set' and makes a major difference in success or failure. Fellow practitioners often tell me that cost is the reason they haven't tried bifocal contact lenses. All the lenses I discuss here are warranted and allow for a choice of translating or simultaneous designs. I'll start with gas permeable lenses because visual acuity is crisper and there are more design options.
THE 5-STEP METHOD FOR ALTERNATING DESIGNS
Bifocal fitting should not be time-consuming nor physically draining. Limit yourself to just a few lenses and follow this method.
Step 1 -- Examine Lid Position: If the lower lid is at or slightly above the limbus, use an alternating lens. If the lower lid is below the limbus, use a simultaneous lens. Indicate the lower lid position for both eyes.
Step 2 -- Record Keratometer Measurements: Choose the base curve for the trial lens using the manufacturer's recommendations. For example, for the Solitaire II, start 0.50D flatter than K; for the FluoroPerm ST, fit on K.
Step 3 -- Evaluate: Use the slit lamp to observe the base curve relationship and evaluate lower edge position. If the lenses don't fit or translate as they should, refit with flatter or steeper lenses. For instance, if the lower edge is below the lower lid, then steepen 0.1mm; if the lower edge is above the lower lid, then flatten 0.1mm. It's not necessary to overrefract as the lens will not work. If the lower edge is at the lower lid margin and the fluorescein pattern shows a well-fit lens with optimum movement, then go to Step 4.
Step 4 -- Observe Segment Placement: Use an ophthalmoscope to observe the height of the bifocal with retroillumination. The bifocal should be just at the lower pupillary margin. Raise or lower as needed. If the seg is below the lower pupillary margin (LPM), order 0.3 higher; if the seg is above the LPM, order 0.3 lower; if the seg bisects the pupil, order 0.6 lower. (Note: These are averages that work well to determine the first lens with each product.) When the seg is at the LPM, proceed to Step 5.
Step 5 -- Determination: Take your overrefraction and add it to the trial lens power. This is your calculated net. Overrefract at near for the add power. Record diameter, base curve, distance and near power, prism and seg height. Order the lens.
THE 5-STEP METHOD FOR SIMULTANEOUS DESIGNS
Simultaneous designs are usually posterior aspheric with eccentricity values greater than one. Good centration is critical with apical clearance and little movement. Early presbyopes do well with simultaneous designs, and they're great for computer operators.
Step 1 -- Examine Lid Position: Regardless of the lid configuration, I always try a LifeStyle Gp first. If the LifeStyle doesn't do what I expect and the upper lid is above the limbus, I try a Unilens or a Total-Vue.
Step 2 -- Select a Base Curve: Use the manufacturer's guide for the initial lens. For example, Unilens recommends fitting 1.75D steeper than flat K; LifeStyle says calculate their E.Q.; and Quality recommends fitting 4.00D steeper than flat K.
Step 3 -- Evaluate: Make sure the lens is riding the way the manufacturer recommends. The Total-Vue and the Unilens should center; the LifeStyle Gp should be a lid attachment. Refit until the desired fit, movement and comfort are attained, then go to Step 4.
Step 4 -- Observe: The Unilens and the Total-Vue should have a central fluorescein pool of 3mm in the pupil area. The fluorescein pattern will show some peripheral touch, but the lens should not be tight. The LifeStyle Gp will show an even alignment fit with a very slight central pool.
Step 5 -- Determination: Do your spherical overrefraction and add the power to the trial lens. This is your calculated distance. Check the near and add the needed power to the trial lens. Record the base curve, diameter and powers for near and distance. Order the lens.
FluoroPerm ST Bifocal (Paragon Vision Sciences)
Solitaire II (Tru-Form)
TIPS FOR SOFT LENS SUCCESS
Hydrogel lenses are relatively easy to fit. Of the 16 types available, I use four: LifeStyle 4-Vue (center distance), Unilens (center near), Sunsoft Multifocal (center near), and Horizon Bi-Con 55 (center near, for astigmatism only). Select the one or two that work well for you.
The secret with any soft simultaneous lens is not to do a monocular acuity check. Typically, vision is not as sharp as it is with single vision and when patients compare, they're dissatisfied. Perform binocular acuity testing and explain that vision will improve as they wear the lenses. If initial acuity is not at least 20/30 near and distance, patients will not be happy.
I balance the distance vision first. Monocularly, I try for 20/30 each eye, and then binocularly decrease power to weakest 20/30. The near acuity should be 20/30 also. Then decrease distance a quarter diopter at a time for best acuity without affecting near vision. If near is unacceptable, add plus to the near eye for modified monovision in quarter-diopter steps to achieve comfort and vision. If the patient is not satisfied with his vision, sending him home with the lenses could result in a failure. If the vision is acceptable (not necessarily perfect), it should improve as the patient wears the lenses.
If a patient cannot accept the lenses because either the near or distance vision is not acceptable, add power to the distance and suggest that the patient wear spectacles for near. Many patients will be happy with bifocal contact lenses if they can attain acceptable near vision 75 percent of the time, and then use spectacles for those critical near tasks.
LifeStyle Gp (The LifeStyle Co.)
Unilens RGP (Unilens Corp. USA)
COMMITTED TO CONTACT LENSES
Once a patient is committed to trying multifocals, they are committed to contact lenses. Multifocal contact lenses are not 100 percent successful, so if your patient is not satisfied, shift gears and try monovision or single vision and eyeglasses. Too many patients leave a doctor's office feeling they failed in multifocals and can never wear contact lenses.
Fitting multifocals is easy and the resultant benefits are generous. The keys to success are:
- Patient screening
- Realistic expectations
- Adequate adaptation period
- Always push plus
Not many practitioners prescribe multifocal contact lenses, so if you do, your happy, satisfied patients will stay with you and refer and refer.
Horizon Bi-Con 55 Toric Bifocal (Westcon)
LifeStyle 4-Vue (The LifeStyle Co.)
Sunsoft Multifocal (Sunsoft Corp.)
Unilens Soft Aspheric Multifocal (Unilens Corp. USA)
Acknowledgement: The 5-Step Method was designed by Sequoia Optical. With their permission, I altered and changed it to my fitting technique.