A practical guide by Pieter Naude – B.Optom CAS(NECO)
According to the latest WHO data published in 2018, life expectancy in South Africa is: Male 60.2, female 67.0 and total life expectancy are 63.6 which gives South Africa a World Life Expectancy ranking of 153. This average of 63.6 increased from being only 52.5 years of age in 2006. With more presbyopes every year due to our ageing population, this isn’t just a topic to think about anymore, it is time to understand it and get your bag of tricks ready. This is something that we need to offer as an option to all our presbyopic patients, especially those with low astigmatism (less than -0.75D).
General Contact Lens Statistics
In South Africa, contact lenses are seldom our go-to option. Statistically, we are far below some of the developed countries. Only 4% of the South African population wears contact lenses. It is important for us to notice the potential. Of this 4%, monthly disposable lenses make up the majority of the market at 80%, with toric lenses at 8.2%, and daily at lenses 22%. Presbyopic lenses only make up 2.7%. 1. Contact lenses have the potential to be a significant part of your revenue stream. With every successful fit, you are almost guaranteed that the patient will revisit your store every six months. This is positive for revenue, but also important from a marketing perspective. It is important that the consumer is reminded of your brand regularly. Optometrists tend to steer away from recommending contact lenses to presbyopes, because they deem multi focals to be more profitable and hassle-free. It is important to understand your patient’s mindset and use the opportunity. Contact lenses are a great additional sale, but what if it becomes a necessity? Multifocal contact lenses satisfy 80% of your needs, 80% of the time. A typical response is “The only way that I know I am wearing my lenses is the fact that I can see.” So, you can still sell the spectacles and have the recurrent contact lens sales. This article will, however, focus more on the actual dispensing of contact lenses and not the economic advantage that it has.
The reality is that no matter how good the technology or design, fitting presbyopes is time-consuming. A little more time on diagnostic fitting and patient education are acceptable to most of us. However, these visits often leave us behind schedule and frustrated. Proper appointment book planning will go a long way and some clever consultation room manoeuvres to reschedule a patient when you know more time is needed, will come in handy. Ultimately the success of the fitting depends on what you are prepared to put in. There is a lot of science behind these lens designs and there is a definite art to the lens prescribing. Before I discuss some of my fitting guidelines, here are some of the exciting new features in multifocal lens designs.
In recent times, there have been a wealth of new innovations, specifically regarding multifocal lenses. These innovations involve lens material characteristics, advancements in reducing lens replacement schedules for soft lenses, and incorporation of multifocal lens optics into specialty lenses such as hybrid and scleral lenses, among many others. 4
Advancements in multifocal optical lens design, present in mass-produced as well as in customised soft lenses, that may consider even pupil size. Moreover, there are increasing numbers of soft multifocal lenses that also correct astigmatism. When it comes to recent advancements in multifocal optical design, two lens designs that stand out. That of extended depth of focus (EDOF from the Brain Holden Institute) as well as the ability to offset the multifocal optics in custom soft multifocal lenses. 4
Extended Depth of Focus (EDOF)
At face value, the concept of EDOF appears very similar to the known Centre Distance design that we know, but it is new to contact lens design and construction. The effect has been summarised as essentially a centre-distance multifocal with approximately 8D to 11D of relative plus power at the pupil and approximately 20D of relative plus power at the edge of the pupil.5 This is way more than the traditional +3.50D that we are used to.
This dramatic power shift across the optic zone is a major departure from the more traditional and more subtle lower amounts of add power obtained by using asphericity, commonly utilised in many commercially available soft multifocal lenses. It is this significantly higher plus power that is created in the peripheral portion of the optic zone that is responsible for the “extended” depth of focus.4
Another significant innovation in multifocal contact lens design is the ability to offset the multifocal optics, to better align with the visual axis. It was described at the 2016 Global Specialty Lens Symposium. Soft contact lenses frequently decentre in the temporal direction due to scleral shape changes. Additionally, our visual axis is relatively nasal to the geometric centre of the cornea. Therefore, the authors summarised that these two findings work against each other in terms of the on-eye performance of not only soft multifocal lenses, but also of scleral multifocal lenses.6
There are now custom soft multifocal contact lenses that can be designed with the optics offset nasally to better align with the patients’ visual axis. (Figure 1).
That might be a lot to take in, but it is important to understand the basic functioning of these lenses. The question remains: “What can I do immediately if I need to make changes to my existing patient in the chair?” What follows isn’t always the only options available, but it guides the decision-making process and helps to achieve an above-average success rate with multifocal lenses.
Adaptation is not instant
There is a reason why the manufacturers’ fitting guides recommend a single lens as an endpoint, with the occasional adjustment. Our neurological system needs to learn how to use multifocal optics. Therefore, most of our patients will see better after a few weeks of wear. A recent study reported that new multifocal lens wearers experience a significant decrease in the amount of light distortion after fifteen days of wear, especially in the dominant eye.2 Proper education about the adaptation process is key to successful prescribing. One can say that a well-motivated patient is far more likely to succeed.3
Once you have carefully selected a possible patient, consider trying a pair of lenses as per the fitting guide. Encourage patients to wear them during tasks that are less visually taxing at first before jumping into their normally high-speed, visually demanding work environments. Also, reassure your patient that changes can be made. Making them too early in the process could reduce their chances of long-term success.
Don’t overdo it
For patients to be able to wear the lenses during the adaptation period, they must be comfortable enough and function visually. My golden rule; is if a pair of dispensed lenses allow patients to see comfortably at a distance and functionally at near, then they are likely to see even better at near when they return for a follow-up visit. Use real-life acuity measures such as cell phones rather than the reduced Snellen chart to gauge needed add power. The Snellen chart and reduced Snellen chart still provides a good constant tool to determine if a patient would cope with his distance or near vision. I tend to steer away from the 6/6 line and is happy to achieve V/A OU of 6/7.5 (6/HAPPY) on my initial fit. I am not too concerned if patients can’t see the bottom line on the reading card. They may think that the lens isn’t strong enough. I then remind them that if I add some power, it is added for both distant and near vision. Once they see that more plus actually blurs their distant vision, the penny drops. There are ways to address the reading issue which will be discussed later. Reassuring patients that changes can be made, and that adaptation is part of the process, is important.
Understand the available designs
Optically, there are mainly four multifocal designs available. Centre near, centre distance, concentric, and aspheric. Be sure to understand what you are using so that you can switch the design of the optics if adaptation is unsuccessful.
Centre near and centre distance are self-explanatory. Centre near means that the reading portion of the lens is located in the centre of the lens. This tends to allow for a little more distortion at a distance as the brain needs to learn how to suppress the defocused light that enters through the centre of the pupil. If we move the near focus to the edges of the lens (centre distance design), the patient can suppress the defocused light by simply constricting the pupil. This emphasises again why adequate adaptation time is needed before we make any adjustments. The sensory system needs to take control of the involuntary pupillary muscles. For some people, it can be a quick adjustment, but for others, it can take up to fourteen days. These designs are usually alternated between the two eyes, and although binocular vision is achieved, one eye would do leading work for distance vision, and the other would do the leading work for near vision. Please note that similar design layouts can be used on a patient; for example, two centre distance lenses can be acceptable for some patients and still provide reasonably good reading.
Aspheric designs are more suited for prescriptions associated with low or high add powers. The added power can then vary, for example, high add can be from +2.00D to +2.50D. Although the lens container might indicate a certain power, it should be noted that the effective power may sometimes even be less than indicated on the blister. These contact lens designs are usually fitted with equal add powers for both eyes and may offer an improved binocular feeling for the patient.
Keys to success
It starts with patient education, aligning expectation, and patient motivation. The 5 “P” principle applies. “Proper Preparation Prevents Poor Performance”. Use your subjective findings and make sure that you provide the maximum plus prescription that the patient can tolerate at a distance. You must do an ocular dominance test. I want to also emphasise the importance of a blur acceptance test. The latter may be associated with a Cooper Vision product, but it has helped me on all lenses. Efficient exam room techniques can improve your success with multifocal contact lenses by helping you make educated changes at the appropriate time. Ask yourself: what do I want to improve? Reading or distance vision? Make the appropriate changes accordingly.
Fitting the patient
I always start by showing the patient their uncorrected V/A on the Snellen chart. I then hand them the reading card. This works well with hyperopes, because they can hardly read the first paragraph. I do this just before I insert the first trial lenses. I want the patient to remember what she was able to see. Once the lenses are in, 8 out of 10 hyperopic patients would report an improved distance V/A, regardless of the design you choose. Remember to give maximum plus but do not overplus. I never occlude one eye, and I use +0.25/-0.25 flippers with an ARC coating to determine if the patient can tolerate any more plus at distance. If they cannot tolerate any more plus, hand them the reading card. I want them to be able to read the 0.63 line, which is at least a 4-5 line improvement from what they were able to see before. To most patients, this will be a good enough motivation to get them going until their follow-up exam in one week’s time.
They can be a little trickier, especially if their refractive error is close to their required additional power, for example, a 45-year-old patient with a -1.50D script. No correction can read as well as their own eyes. What is key for their success is to show them their poor distance V/A and explain to them that the challenge is to see good at both distance and near and not just at one of the two. Be careful not to over plus these patients, they are very sensitive to hyperopic blur, but maximum plus is very important. Again the +0.25/-0.25 flippers would be your tool to determine this once you inserted the theoretical best trial lenses. Before I hand the reading card to the patient I test to see if the patient would not tolerate just maybe a +0.25 more in front of the non-dominant eye. If they do, keep this in the back of your mind should they battle with near vision. It can be a good first move to adjust the lens. It is also possible to improve distance vision by using two Centre Distance lenses, but it may have too much of a negative effect on the reading. Reduce the add given in the dominant or sensory dominant eye can help the distance V/A, and the last step could be to add -0.25 on the spherical component of the lens, either OU or just on the dominant eye.
You need to determine the eye with the least amount of astigmatism (less than -0.75D). Use this eye for the multifocal lens. Fit the other eye with a distance toric lens. Note that I am not thinking dominant vs. non-dominant now. The multifocal eye needs to be a centre near design or an aspheric design if you hope to achieve reasonable to good near vision. Provide maximum plus for the toric lens and have your flippers ready. Ensure that the patient cannot tolerate any more plus before moving to the reading card.
A new product is the custom made multifocal toric contact lenses. These lenses are made to specifically fit the corneal diameter and base curves of each patient, which allows for better alignment. Not to be forgotten is that rigid or hybrid multifocal lens designs will be a good choice for higher astigmatism, but it is a discussion for another time.
I add this table for easy referencing.
Some last pearls
- +1.00 ready readers! Remember that the patient was frustrated to not see up close at all. If they now only need to use readers for very small print or prolonged near tasks, that is a good trade-off, in my opinion. It is also handy to help them get through the first weeks of adaptation. My success rate drastically improved since I started handing out +1.00 ready readers with my first trial lenses.
- The flippers are a good and clinical approach to establish if the patient can tolerate any more plus, and they perceive it as a good guided approach. I prefer to use ARC coated flippers. Remember we induce glare when we fit presbyopic lenses, and therefore I don’t want to reduce the contrast sensitivity any further by adding a lens in front of the patient’s eyes that will contribute to the glare.
- Near Boost. An important technique to improve near visual acuity. Ensure that you understand the blur acceptance test. If you know which eye can tolerate the most blur, increase the plus correction on the distance power of the lens in that eye with +0.25 or max +0.50. If you boost the plus too much, you will decrease binocularity again. Some patients might be happy to lose a bit of binocularity for improved reading. Remember the first rule, though: don’t make too many adjustments at the beginning. Review your findings a week later.
I found that success depends more on the patient’s ability to be comfortable with their distance vision. If the patient can tolerate a slight reduction in the add power (under correct the add) in the dominant eye, it helps to get them through the first week. Keep those +1.00 ready readers ready.
Patients will see your confidence and trust your skill if you educate them along the way. Happy presbyopic prescribing!
- Alcon Business Day
- Fernandes et al, 2018
- Messer : Contact Lens Spectrum, Volume: 33
- Mathew Lampa, OD : Contact Lens Spectrum, Volume: 33
- Cooper et al, 2018
- Zheng et al, 2016 Global Specialty Lens Symposium
- Pieter Naudé : In practice experience
- Contact Lens Society Presbyopic Conference @ Midrand 2015