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Great Expectations: A Guide to Successful Multi-Focal Soft Contact Lens Fitting

By Christopher Miller, ABOC, NCLE

The two most fun and equally challenging contact lens fits are first time wearers and presbyopes. It’s all about expectations, for both the fitter and the patient.

Recent data indicate that about 45 million people—about 15 percent of all Americans—wear contact lenses, according to the Consumer Barometer December ’09 (Jobson Optical Research & the Vision Council).

Contact lenses are classified in two major categories—spherical and specialty. Spherical lenses contain a single refractive power and are by far the most commonly prescribed. Varieties of specialty lenses include toric (to correct astigmatism), multifocal (to correct near and distance vision), cosmetic tint, and extended wear. According to industry data, spherical lenses accounted for 70 percent of dispensing visits and 57 percent of total soft lens sales in 2003.¹ Within the specialty segment in 2003, toric, cosmetic tint, and multifocal lenses accounted respectively for 16 percent, 9 percent, and 5 percent of patient visits when contacts lenses were dispensed.2 However, the number of new bifocal wearers continues to increase. Current numbers indicate that 33 percent of the US population will be between 40 and 59 years of age by the end of 2010 with 14.5 million turning 40 within the next four years. That’s one person turning presbyopic every eight seconds. These statistics indicate that a very large potential market exists for multifocal contact lenses (MF). Therefore, it is an area in which you can easily develop as a portion of your specialty practice.

This list suggests that the easiest and perhaps the first patients to begin fitting should be emerging presbyopes and people who work in offices or needing excellent intermediate vision. Lucky for us, this amounts to a large percentage of our presbyopic patients and after gaining some experience and success we can begin to fit the more difficult ones as well.

LENS DESIGNS

Your arsenal: Center Distance and Center Near designs. These lenses are concentric in design (see diagram below) giving simultaneous vision where the near, intermediate, and far powers are simultaneously corrected. They work on the principle that the pupils constrict during accommodation, as they turn inward to read and dilate when relaxing for distance vision. CooperVision lenses are available as both distance and near center designs while the Bausch + Lomb, CIBA, and Vistakon designs are near center. Some lenses are labeled with add powers; others as either low or high.

Personal experience has shown that they all work well depending on fitting objectives. Understanding the patient’s lifestyle and more importantly, their work’s visual requirements, will help determine the fitting objective with the following list of available lenses and the fitting process below will be seven different fitting objectives and the suggested starting lens combinations in the order of fitting difficulty.

TWO MAJOR GOALS

First, provide binocular vision whenever possible. Second, deliver a solution that works more than 80 percent of the time.

THE FITTING PROCESS AND OBJECTIVES

Your aim is to give patients binocular 20/20 distance vision. Binocular vision is required for depth perception and comfort. In addition to this, you have to find out which is more important to your patient most of the time; their intermediate or near vision. You are only able to get best vision in one of these zones, with the other zone being acceptable but not as clear. This is because the intermediate zone power though being progressive, has an somewhat fixed range depending on the add power being chosen with the higher powers having a shorter depth range and lower powers a greater depth. This is similar to what professional photographers have to figure out when choosing which F stop to use in order to increase or decrease the depth of field of focus.

When taking the patient’s history, determine the most important usage zones. This should take about the first five minutes of the fitting process. It might help to explain that the best vision possible is single vision, i.e.; one pair for distance, one pair for intermediate, and another for near, but that this is also very inconvenient as you never seem to be able to find your glasses when you really need them. So, even though multifocals are a compromise in vision, their convenience usually are the best choice for most patients.

Next, assess whether they currently use multifocal glasses or readers, their job responsibilities, and listen carefully to how they describe the way they use their eyes for 80 percent of the day. Take notes. Next, hand them a reading chart and ask what size line they need to be able to read “80 percent of the time.” Write down the required near/intermediate acuities as your fitting objective.

It has been the author’s experience that most patients are OK with J4-J5 at near which is also quite adequate for computer. Affirm your near and intermediate vision objective out loud by asking, “If I am able you give you this line, J4, near vision, would you be happy with that?” Watch their reaction and body language closely before proceeding, as it is easier to eliminate the difficult fits now rather than three or four visits later. Affirm the possible need for low power reading glasses for occasional sharp near vision. Overall it is best to promise little and attempt to deliver a lot. Explain the costs up front and the extra amount of time necessary to fit these specialty lenses.

When reviewing the Rx, remember to determine the spherical equivalent for low amounts of astigmatism (-1.00 cylinder power and under) by adding half the cylinder to the sphere power algebraically. Compensate for vertex powers over +/- 4.50D power when necessary (see examples). Determine the dominant eye (see below) and whether a modified fitting is required because often your changes in power to sharpen either the distance or near vision will be in one eye only.

Insert the lenses and let them settle for about ten minutes. Hand them the reading chart again and wait for the “wow”. Even after fitting over a thousand patients with multifocal contacts I am still pleasantly surprised when I hear it.

Check both distance and near visual acuity and compare this with your fitting objective and note it in the chart. Check other vision tasks, at a computer station for intermediate vision, their telephone or watch for adequate near vision. Have them note how much larger their intermediate field is with these lenses comparing them to multifocal glasses if they wear them. Have readers close by and let them try them if they need to. This is the point in the process when expectations are changed. Now, prepare the patient for using their new contacts in daily tasks.

Move to the slit lamp and check for centering and movement with upward gaze. Note any lag with the blink, as it should be similar to a regular soft lens fit. Instruct patients not to compare vision from eye to eye by closing one then the other. They will quickly learn to adapt to their new vision and they will find that it improves day by day. A follow-up appointment is recommended for seven to 10 days to assure visual acuity, fit, and comfort.

If all looks good, dispense with solutions, a new case, and readers if they need them. Contraindications 20/20 uncorrected distance vision (most times), critical care decision makers or those with high visual needs, unreasonably high expectations, and/or busy people who don’t keep appointments or don’t want to listen to the education about their lenses, care and wearing schedules.

Modified Monocular Multifocal Fitting For some people, no matter how much you try, you may not be able to fit with two lenses of the same design. If they need better distance vision or better near and you have already tried a higher or lower add in one eye or the other, then you might have to try a modified monocular approach. A modified monocular fitting is where one eye is fit with a regular MF and the other fit with either SV or a different distanreading power than what was prescribed. Normal monovision fits the dominant, or most used eye, for distance vision; the other eye being corrected for reading. Two simple single vision lenses are used. Although this may seem unusual, the system generally works extremely well after just a short period of adaptation. The brain is able to resolve vision in favor of the better image.

Specialist contact lens practitioners have regularly corrected for distance and reading with monovision since the 1950’s so the system is very well proven. In a modified approach consider using a single vision lens fit for best distance, intermediate, or near with a multifocal on the other eye. Another approach might be to use a low add on the dominant eye and on the non-dominant eye add half of the add power to the distance power algebraically and use a medium add power (see 2nd suggested powers in example #3). This effectively gives the patient 20/20 distance on the dominant eye and on the non-dominant an intermediate power in the distance portion of the lens and the full near power in the near portion. The advantage of this approach is that it enhances the intermediate vision which is great for many tasks. Always let the patient test the lenses for a week before attempting any other lens changes.

A word should be added here that just because a patient was previously fit in mono-vision doesn’t necessarily mean that you should fit them with a modified fitting first. I always try a binocular MF fit first to see if their acuities are acceptable. It is the author’s experience that many previous mono fits are among the easiest to convert to binocular multifocal vision.

FOLLOW UP AND TROUBLESHOOTING

Check the fit, noting centration and lens movement when blinking. Recheck visual acuities, be sure cell phone and reading card are acceptable. Record the results and compare with original fitting objective and expected visual acuities. Check for patient’s comfort, wearing time, and satisfaction with vision. Note any dry eye symptoms, use of comfort drops, or sleeping in lenses. Ask about any blurring at night or difficulties when reading (good lighting is needed for proper pupil constriction). Ask if they are using readers occasionally or not at all. When making a change consider whether more plus or more minus is needed keeping in mind that sharper near vision (using a higher add) equals less intermediate field. Make changes only when necessary and have the patient wear the lenses another week to assess success. If the patient’s satisfaction is high, dispense a supply of lenses.

PICKY PATIENT?

All of us have patients that require more of our skills than others. We also have an occasional patient that isn’t afraid to ask if there is more that we can do. It’s not that they aren’t seeing well or that their lenses are uncomfortable. These patients fall into a category all their own and need reassurance that the fitter has done everything in our power to meet their visual requirements.

They probably ask the same question to their other health care providers, auto mechanic, or anyone else from whom they purchase for products and services. Let’s just say they are quality conscious. The author has seen practitioners change the prescription or fitting and undo the entire fitting and testing process just because the patient asked them, “Is this the best you can do?” Remember when a patient asks this, the patient isn’t necessarily asking to change anything, but may need reassurance that you have done everything in your power to give them the best vision possible.

Remember to verify acuities against the initial fitting objectives. Always reassure them first but if still reluctant to complete the fitting and different fitting options have been explored, as a last resort offer to put them back into distance lenses with readers. Try a monocular fit if they were fit that way previously. The patient’s response will tell if their vision was adequate or not.

GREAT EXPECTATIONS, GREAT RESULTS

Multifocals are easier to fit than imagined; much easier than their counterpart in glasses, and many patients will be thrilled that for the opportunity to try them. This is one lens that truly gives great results and what more could any of us expect?

Watch for more daily and other hydrosilicone multifocals coming soon.

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