By Eef van der Worp
Contamac continues to be the sponsor of the World-Wide Education series – otherwise known as The Contamac Education Series – providing generic speciality lens education globally. The Contamac Education Series of the past year, led by myself, involved an array of live lectures and well-received live webinars. These lectures provide speciality lens education to optometry schools that may not always have easy access to this topic.
Lectures were delivered in various locations including schools and conferences, ranging from the Netherlands, Bloemfontein (South Africa), Prague (Czech Republic), Oregon (USA), Montreal (Canada) – truly a World-Wide series.
The topics of the Contamac Education Series ranged from corneal lenses, scleral lenses, to corneal topography and – increasingly – to speciality soft lens fitting. The latter, covered in more detail in this edition of Global Insight. Let’s begin.
Perhaps this analogy is little bit simplistic, but seems at least interesting that all of us use the greatest and latest technologies based on incremental technological advancements. Moving from one iPhone version to the next within the span of a year. As Philipp Polonyi – Sales & Marketing Director of Contamac – put it, “last year’s version is outdated within a short period as we continue to make new discoveries. What is striking though is that we seem unable to apply the same concept of incremental change to our contact lens industry, in particular when it comes to soft lens fitting.”
We know the “old” approach of soft lens fitting is inaccurate and whilst we are not entirely sure that our current thinking is the holy grail, we can be sure that it is more accurate than what we thought in the past.
In the latest editorial for Contact Lens and Anterior Eye, the journal of the British Contact Lens Association (BCLA) James Wolffsohn stated it quite frankly, in plain English and without a word of Dutch: “Keratometry – A technique that should be relegated to the clinical dark ages?” If a practitioner is just fitting soft contact lenses, keratometers can be safely mothballed and if they are fitting more complex gas permeable lenses, they should invest in better technology to assess the shape of the ocular surface – he states.
As current discussions continue, it is time to go back and prioritise the lens fit first when fitting lenses in our contact lens practices – and our speciality lens practices specifically – before considering optical solutions and alterations. As illustrated by websites like simplecontacts.com, the ‘soft lens fit’ has been downgraded to a $10 worth procedure, which can be done with a smartphone application. As for soft lens fitting – first and foremost we must find ways, and tools, to start fitting soft lenses again.
As mentioned in the BCLA 2017 keynote address that I was fortunate enough to present – our priority should be to move away from base curves when it comes to soft lens fitting. Base curve selection and fitting in soft lens practice has been proven to be a pretty useless procedure.
Just like our little fish-friend Nemo in the famous movie, we, as eyecare practitioners are – sometimes desperately – looking for something. Normal eyes, in our case: NEMO’S (Normal Eyes Measured Ocular Surfaces) to fit the standard arsenal of lenses that we have available to us. It is generally accepted that, when we are dealing with an anterior ocular surface with average dimensions, a standard frequent replacement lens is most likely the best lens option out there: they excel in material of choice, manufacturing technique and replacement frequency.
However, what if the eye’s dimensions are not ‘top of the bell-curve’? In that case, a speciality lens – either based on an extended parameter range or custom-made – could make a difference and could even play a prominent role in preventing a huge number of dropouts. But this first raises the question: what is a normal eye?
It may be hard to digest, but modern computer modelling would be able to answer this question better than we can in clinical practice. The new soft lens fitting modules that have been developed will calculate height maps for the area that the soft lens will cover. Dedicated algorithms calculate the sagittal height of the eye for the chord diameter of the proposed soft lens. When we know the given dimensions of a soft lens – sagittal height and beyond that – then the software can first determine whether a standard lens would fit in theory; it can suggest a standard lens that would fit ‘best’ or, alternatively, would suggest an out-of-standard lens or – if needed – a custom-made lens. A company in the Netherlands, for instance, recently reported such an algorithm for soft lens fitting based on a database of 10,000 eyes.
When doing a subjective refraction on a patient that has, let’s say, 6.00D of myopia, we don’t start from scratch with zero and increase in 0.25D steps to reach the -6.00. We typically start with -4.00 or -5.00 to find the optimal refraction. Similarly, with soft lens fitting, it would be great if technology could give us, to begin with, a ballpark estimate of where we are and where we could go.
Artificial intelligence can help, especially in our speciality lens industry, to do things better. That way, we’ll know when to fit a standard soft lens or whether an out-of-standard, or even a custom-made lens is needed for a given eye, and when to fit a scleral GP lens (versus a corneal GP lens) for instance. This may, to a large extent, depend on the amount of elevation difference on the ocular surface in microns. What about when to choose a toric (corneal or scleral) GP versus a spherical design? Again, it depends on differences in height. But it all starts by finding the normal eye – to distinguish it from the more challenging eyes.
We are moving away from Myopia Correction – to Myopia Control. This is much more than just a new modality for our contact lens practice – it is a shift in paradigm. In fact – we are managing the paediatric patient: hence Myopia Management would be the most appropriate term. We may be converting our practices from simply correcting ametropia and servicing our patients’ refractive needs to treating them in a therapeutic way, preventing or minimizing myopic retinopathy and potentially changing lives.
Orthokeratology is a great way of doing this, but is limited to some degree in its capacity. It can deliver excellent myopia control effect (up to 50%) in children with median amounts of myopia. But under 2.5D of myopia and over 4.5D of myopia, the effect seems to be limited. Hence there is a small range of applicable myopes. Typically, when children come in with mild myopia – of let’s say 1D – then soft bifocal options are the preferred option, in conjunction with atropine maybe for the high-risk profile group.
Control over the Fit
If this is true, we need to get our act together on the soft lens fit, especially because we are working with kids. But when it comes to soft lens fitting, we don’t quite have full control over it. In addition, unlike when fitting corneal GP lenses and orthokeratology, we don’t have adequate technology in our practices to measure the ocular surface shape around and beyond the corneal borders. The reason why this may become relevant is that when a soft lens is placed on the ocular surface, a certain amount of flexure will take place. Our studies at Montreal University and Pacific University show that this can be quite substantial. If there is an excessive amount of difference between the sagittal height of the lens and that of the ocular surface (over the same chord) – then this can have a substantial (negative) effect on lens flexure, on the optical performance of the lens on-eye – and potentially on the myopia controlling efficacy of that lens.
Another thing to consider is soft lens decentration. As it has become clear from scleral lens fitting, the anterior scleral shape is not symmetrical. In short: the nasal area of the anterior ocular surface is flatter compared to most other parts, and in particular it is flatter than the temporal side of the eyeball beyond the corneal borders. Hence, in both scleral and soft lens fitting, this may result in some sort of temporal decentration when the lens is placed on the eye. This decentration comes in addition to the negative influence of the geometrical centre of the eye versus the line-of-sight, which often already results in a temporal offset. If the central optics of the myopia control lens are too much out of line with the line-of-sight – this again can have a potential negative effect on the myopia control efficacy.
What all this means is that we will likely have to customize lenses for myopia control. Because ‘substantial amounts’ of plus in the periphery seem to be needed to take advantage of the myopia control effect, we may need to consider what lens modality would work best. For a young 9-year-old with low myopia, let’s go back to the earlier mentioned 1.00D myope for instance, what would be the best option? Many would consider orthokeratology, as it has proven to be one of the most robust myopia control modalities. But a standard orthokeratology lens may provide only +1.00D of peripheral defocus. That may not be enough. A dual-focus soft lens at this point may be the best option for that patient. If the patient progresses (to a lesser degree, presumably) to a higher level of myopia, then orthokeratology may be a good option later in life. In other words: it looks like we will have to customize both the modality (the type of myopia control) and the lens design from a fitting perspective.
The same is true in scleral lens practice. More and more it becomes clear that the sclera is not spherical in nature. In an article ‘Quantitative Assessment of Scleral Shape Patterns Using a New Wide Field Ocular Surface Elevation Topographer’ Greg DeNaeyer et al. propose a new classification system for scleral shape.
Of the analyzed 140 eyes, 5.7% of the plots were primarily spherical at a 16-mm diameter from the corneal center, and 28.6% were primarily regularly toric. 40.7% of cases had asymmetric troughs or asymmetric peaks. The remaining 25% had irregular peaks or troughs. In summary: it is relatively rare that the sclera is spherical (less than 300 microns of difference in different meridians), and in many cases toric haptic or more complex lens designs (such as quadrant specific) could be indicated.
Ritzmann et al. in Contact Lens and Anterior Eye looked at scleral shape at different chord lengths (diameters) using optical coherence tomography (OCT). At a 12.8 mm, the shape of the anterior eye was found to be nearly rotationally symmetric, but at a chord of 15.0 mm the shape became increasingly more asymmetric. Significant differences between opposing segments were found in the sagittal height and scleral angle measurements at a chord of 15.0 mm (both in sagittal height and in scleral angle). The nasal measurements revealed flatter scleral angles and concave corneoscleral transitions, whereas temporal scleral angles were steeper, with tangential or convex corneoscleral transitions.
Customized Lens Designs
This calls for more customized lens designs such as toric, quadrant specific or even fully customized lens shapes. Once the lens fit has been determined, then any kind of front optics can be applied. Because of scleral lens decentration, we see more toric overrefractions.
On one hand, this can be partially prevented by customized back surfaces (causing less decentration). But if a toric overrefraction is present, we can simply apply that to the front of the back toric scleral lens design (without additional stabilization). Also, multifocal optics and higher order aberration control optics can be applied quite simply.
We need to go back to the drawing board, to redefine contact lens education. Soft lens fitting is currently our biggest headache. We can actually learn a lot for corneal GP and orthokeratology lens fitting – in many parts of the world this is done solely and exclusively based on ‘evidence’ of real corneal shape data (from corneal topography). From that, accurate and smart software will design the best possible lens. Our job is to manage that. With scleral lenses – we are just starting to learn and embrace the modality better, which can and should be one of the main driving forces to excel further.
With regards to soft lenses – we need technology to first define whether we are dealing with a ‘normal eye’ and to classify that. That 75% or 80% of ‘NEMO’S’ could most probably – within limits – be fitted with standard lenses. But for the other 20% to 25% we should offer alternative lenses – either with extended parameter ranges (diameter and base curve – or better sagittal heights), or with custom-designs based on ocular shape topography.
But to echo Albert Einstein’s words: ‘We cannot solve our problems with the same thinking we used when we created them’. That is why education is such a crucial part in this revolution. Contamac should be proud of their role in providing and delivering generic contact lens education around the world, via the World-Wide Education Series. Newsletters and many other initiatives – to share, discuss and upgrade the methods we are using today.
Contamac Educational Series Feedback:
From Utrecht, The Netherlands:
We are very pleased with the opening lecture that you have given at Hèt Congres Vormstabiel. In a very humoristic, but scientific way, you led us through the history of contact lenses and into the present day. The panel discussion which you led was very helpful in clarifying the position of the different educational institutes that we have in the Netherlands, and highlighted the path we could follow. We would like to give special thanks to Contamac for sponsoring you!
We are overwelhmed with joy that we are able to set up lectures, such as The Contamac Education Series, with support from the industry. To help educate the workfield consisting of optometrists and contact lens specialists.
Roel Jonker, President of the Dutch Contact Lens Society ANVC
From Bloemfontein, South Africa:
The Skype lectures were very interesting and a great learning experience. I enjoyed the way Dr. Eef van der Worp explained difficult concepts with simple, informative, flow charts and captured the room with his witty presentation skills. I’m very grateful for the opportunity to learn from someone with a completely different background.
Ruella Munsamy, Student
I found the lectures with Eef van der Worp to be very beneficial as they provided so much insight and background into the subjects presented. It was great to hear him speak so passionately, and it really inspired me to excel in contact lenses.
Ane Jacobs, Student
From Pacific University College of Optometry, OR USA:
I want to say thank you for the support of Dr. Eef van der Worp. We at Pacific University within the contact lens department see him not only as a world leading authority in the area of eye shape and contact lens design, but as one of the greats to be able to interpret literature and have it make sense in clinical practice. He has an engaging and rich informational presentation style that not only comes through in person, but even via video conference as we recently saw when he addressed our third-year optometry students remotely. It was incredibly well received by the students!
Matthew Lampa, OD, FAAO, Associate Professor, Chief of Contact Lens Services
Soft Special Edition Newsletter
In line with Contamac’s World-Wide Education series, since 2010 Contamac continues to be the exclusive sponsor of Soft Special Edition, a quarterly newsletter on soft speciality contact lens research, developments, designs and materials.
Readers from all over the world have subscribed to this educational newsletter, which is available free to any eye care practitioner. To sign up, simply visit the Soft Special Edition website.