Article Date: 2/1/2001

PROGRESSIVES
How Progressive Do You Want To Be?
These steps may be the blueprint you need for greater PAL success.
By Irwin Shwom, O.D., R.D.O Everett, Mass.

Progressive addition lenses (PALs) have made our lives easier and richer. But how's your success rate? Success with PALs isn't an easy task without a consistent plan of action when fitting these lenses. I know that many of you leave fitting PALs to your technicians, but neither you nor your technician should miss out on these ideas to achieve more success with them.

Finding a scapegoat

After years of experience in both the opticianry and optometric ends of our field, I've discovered that many us find it easier to blame our patients for not adapting to PALs rather than to search for better solutions so they can adapt to these lenses.

For PALs to become the workhorses of our practice that they should be, we need only make sure we consistently follow a few steps when fitting patients with PALs.

Here are the seven steps that I follow:

1. "scope out" the right patient candidates
2. explain PALs to them
3. examine and prescribe
4. select frames that make the lenses work
5. "dot" them
6. fabricate them
7. adjust them.

Once we've done all of these, then, and only then, can we assign to our patients the relatively simple task of getting used to PALs.

Scope out the right patient candidates

I've found that most successful PAL users need to present to us with some concern regarding their inability to visually function smoothly and completely with their emerging presbyopia. Initiate a full discussion with your patient about the alternatives of two pairs of glasses and lined bifocals, listing all the advantages and disadvantages, prior to recommending PALs. After having this discussion with patients, I've found that for most of them, PALs provide a more than reasonable visual alternative.

Patient candidates for PAL use fall into a couple different categories. For instance, patients who are considered:

• "head pointers" will sight targets in their peripheral fields and always move their head toward the target. By far the most successful patients we have are "head pointers."
• "eye turners" keep their heads still and search peripheral targets with their eyes only. You can fit them with PALs, but they have a larger rate of failure. Reforming them into "head turners" just creates frustration for both the patient and you.

Searching

You can fit monocular patients successfully with progressives at a cost. Even when we do everything correctly, those monocular patients who're in need of wide fields of view, especially at near, are limited by many of today's PAL designs. In our office, we fully advise successful monocular progressive users of the field limitations and demonstrate these limitations to them where possible.

Strabismic patients who function monocularly fit into the above description. Despite some limitations, they can be successfully fitted with PALs. Intermittent and large phoric patients have shown relatively large failure rates. A basic tenet of successful PAL fitting has been, "Both eyes and the nose need to be pointing to the same target at the same time," and they don't always meet that criterion.

Head tilting patients are all right as long as they're constant and repeatable. Patients with mild to moderate degrees of head tilting from vertical can be successfully fitted with PALs as long as this is a normal and natural position for them to remain in.

Discourage patients who drive at night and lift their chin upward to decrease the glare of oncoming headlights from using progressives.

Explain them

Negative selling isn't something I like to do, but it's important to explain up front things that PALs don't do well.

Backing up a car isn't easy for PAL users. If you were to look way back over your right shoulder now, you'd notice how your chin moves up. Think about what occurs when we raise our chins with a PAL. Good for reading, bad for distance.

Lying down while watching television isn't easy, either. When we lie on our backs, our chins again rise. This helps with reading, but unless a television is mounted at or near the ceiling, we're now looking out of the reading/intermediate portion of the progressive.

For long-term, detail tasks, PALs aren't necessarily the best option. Although we've made great strides to a truly wide field of view for near tasks, especially in higher add powers, we know that we've yet to reach optical nirvana. The relatively limited width continues to create visual comfort issues for even my happiest patients.

I've still found nothing more comfortable for a uni-distance focal length task than to have a pair of single vision near-only glasses to read with for extended periods of time. In situations like this, I can continue to feel comfortable prescribing progressives. But in this situation, you have a great opportunity to offer a pair of prescription readers as appropriate adjunctive therapy.

Active patients

Rock climbing, hiking, cycling and some racquet sports are also difficult for PAL users. Odd head tilt requirements along with the need for quick eye movements consistently remain on target for single clear vision. Given these conditions, I'd fit a PAL only to an experienced wearer, but never to a rookie.

Unfortunately, the lens design always has an area that is out of focus for the patient. We all know that the optical engineers in our field have done a great job of designing today's new progressives, but they know and share with us their frustration in not being able to make the perfect progressive.

Unwanted, but inherent, astigmatism exists in every PAL design. Most of the unwanted power is located in the lens in both the nasal and temporal portions of the intermediate and near segments of the lens. As opposed to waiting for patients to tell me about the "blur" they see at intermediate and/or near, I demonstrate that to them up front.

I use a standard Amsler grid chart and have the patient move the glasses closer and farther from the chart to demonstrate the "by design out of focus zones" in the PAL. Doing this has dramatically cut down on my patients' objections to peripheral blur at near symptoms.

Examine and prescribe

A great refraction has no substitute, regardless of the technologies that we use to get there. Knowledge and comfort with your refracting and prescribing techniques are a must. This is no time to try "new" techniques on the refracting side of the table.

Prescribe your full-powered prescription for both distance and near, making sure not to add "extra power" at either distance or near for compensation. The compensation has already been done for you in most new lens designs.

In prescriptions with greater than 5.00D of power, know the distance at which you're refracting and the vertex distance at which you'll fit your patients. Here's the opportunity to prescribe "small" changes in the final prescription to get your desired visual outcome. We do it with contacts, so we can also successfully do it with PALs.

I've found that the unequal image size found in anisome- tropic patients creates about the same amount of post fitting frustration as conventional lined bifocals.

Patients who report classic difficulties while reading with lined bifocals will report the same effects with PALs. However, I've found that prescribing a slab-off compensatory prism, a widely underused but successful option, fixes this problem.

Also, I've had great success fitting patients who meet all standard fitting criteria, but who also have a relatively large amount of astigmatism. With today's super-calculated, computed and manufactured PALs, astigmatism doesn't pose a big problem for a successful fitting.

Select the best lens

How do we know which PAL to fit? To be honest, this is where you have to try them yourself and decide. My lens representatives do an excellent job of providing us with information on the comparable strengths and features of their company's lens designs. However, I've found that I need to try them on myself first to "see" what they're trying to tell me, then decide where I can best use the lens.

• Decide what your patients need for an intermediate/near "ramp power" (rate of lens power change). If we're fitting PALs with segment heights of 16 mm or so, you need to remember that the patient only has a relatively short ramp to get from his full distance prescription to his full near prescription. If the patient expresses that he'd like to see and do everything quickly, then this PAL design might not be a success. The rate of lens change might be too quick.
  In opposition, a PAL that has a minimum fitting height of 21 mm or more has relatively slower acting optics (longer ramp) from maximum distance to maximum near powers.
• Select frames that make your lenses work. In our office, I choose frames that make my lenses work well. I've found in my dispensary that once I permanently adopted that philosophy everything -- including successful PAL fittings -- flourished. It's only when I let our patients tell me what they want that I sometimes still get into trouble.
• One of the biggest challenges is making sure that the frames I most often sell have an adequate "B" dimension to make my PALs work. Not only do I pay attention to the near minimum fitting heights of my recommended PALs, but I also need to ensure that the patient's eyes are far enough away from the top rim of the frame to make the distance aspect of the PAL useful.
  I've recently run into a risk of PAL failures due to post-fitting symptoms of difficulty with distance visual acuity. The failures were because of PALs I fitted when I didn't pay attention to choosing frames with an appropriate "B" dimension compatible with a good visual outcome at both distance and near.

Make it work

Use adjustable nose pads. Unless you have a super adjustable, pliable, fixed bridge resin frame, always fit PALs with frames that have adjustable nose pads. You need the feature of adjustability while dispensing to make those last-minute tweaks on the completed spectacles. You also need to use adjustable face form and pantoscopic tilt capabilities.

Choose frames that either incorporate this feature or that you can manipulate at either the fabrication or the dispensing time. These types of frames have the ability to be rounded to the face and create between 10 to 15 degrees of pantoscopic frame tilt. You should be discouraged from using any frame that you can't reasonably bend or won't maintain a position.

Once you've found the frames that work best, supply them in multiple bridge sizes in your dispensary. As I walk into my own dispensary, I see many frame shapes that look nice, but similar, from a distance. I'll carry the same effective shape frame in multiple sizes but each one has the nose pads mounted in a different place on the frame.

For instance, if I'm looking for an oval-shaped frame, and the one I've initially selected causes the frame to sit too high on the patient's face, I just look for the same type of frame that has the nose pads mounted a little higher on the frame. This feature causes the frame to drop a bit, creating a better fitting advantage.

Don't purchase a frame that you'd use for fitting PALs if you can't make adjustments smooth-ly, fully and without breakage. Some frame designs and materials make adjusting more challenging than necessary.

Dot 'em

You've heard it for years: "Place the optical center of the patient's lenses directly in front of his line of sight for the required tasks." Fitting PALs is no different. The concept of dotting the optical center is a necessary technique we all must master.

Remember that the patient's right eye sights his left eye and the patient's left eye sights his right eye. Don't cross sight because that causes parallax, resulting in a false optical center and possible PAL rejection.

Make sure you're at the same height as your patient when dotting so that you see eye to eye. Either get up to his height or have him come down to yours.

Have the patient place the adjusted frame on before and after dotting in the position that he's most likely to wear them. Before I asked patients to do this, I consistently had a high rate of PAL failures.

Think about it: I want frames to fit certain ways, so I place them where I think they should be on the patient's face. Patients listen to me in my office, but once they've left, the real world takes over, and they adjust the frames to their comfort level.

Of course, this doesn't always mesh with how I've adjusted the spectacles. At the time of dotting, I'm as insistent as I can be that my patient place the frame on his nose and face in a location that they "most likely" will end up using them. In most situations, I can be kept in the positive column of PAL success by making small, easy-to-do compensations on frame fit.

Dot the patient's pupil location in a consistent manner. I've found that searching, locating and dotting the nasal aspects of the patient's pupil has helped a lot in making me accurate with proper centration of the finished distance PAL.

Fabricate them

With today's patternless edgers and computerized lens layout technology, this is the easy part. Let the machines do it. Uncut finished PAL lenses come with marking dots that are easy to locate and use.

After you've used the standard layout and blocking techniques, edge, finish and insert the completed lens like any other simple single vision job. Nothing special is required to edge and finish these in your own in-office lab.

Inspect the finished job optical center using the lens manufacturer's layout charts and against the dotted sample lenses. Should your dots not line up with the prescribed fitting centration, stop and either re-align the lenses in the frame or throw them away and start again. This isn't a situation where close is good enough.

Adjust them

After you've completed and inspected the finished eyeglasses, ensure that the finished product is "bench fitted" with 10 to 15 degrees of pantoscopic tilt.

• We know that all PALs by design are aspheric. However, there's been a wonderful proliferation of single vision and multifocal aspheric lens designs. In the past 10 years, keys to successful fitting have been to fit and adjust frames so that they rest as close to the apex of the cornea as is reasonable.
  When fitting PALs, I loosely think of these lenses as contact lenses. I'd never fit a contact lens at any appreciable distance from the tear film, so I try not to do the same with PALs. The closer to the eye I fit the progressive, the better it works.
• It makes no sense to fit curved lenses to curved eyes with flat fitting frame fronts. We need to fit curved lenses to curved eyes with curved frame fronts. I've found that many frames today have less face form to better fit the flatter aspheric single vision lenses. Well, this might work well for these lens combinations, but this is a recipe for potential failure when fitting PALs.
• Maneuver nose pads to control the visual outcome. Using the proper pliers and techniques can help you create the final vertex fitting distance that will make the PAL work easily and effectively.

Times are good

We've never had a better or easier time to prescribe, fit and troubleshoot PALs. Today, most progressives work well "out of the box." Certainly, some work better than others, and we've all developed our favorites. With the unveiling of the next generation of lenses fitting progressives just gets easier.

Dr. Shwom's brother, Leonard C. Shwom, O.D., R.D.O., contributed to this article.

Dr Shwom is in private practice in Everett, Mass. He's an associate professor at the New England College of Optometry in Boston. If you have your own "Tricks of the Trade" on progressive addition lenses, please send them to: Irwin M. Shwom, O.D., R.D.O., 421 Broadway, Everett, Mass. 02149-3435. Phone: (617) 387-1904. E-mail: bubba421@aol.com.

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Optometric Management, Issue: February 2001