Progressive addition lenses can be notoriously difficult to successfully dispense, but there are several techniques that can be used to ensure patients are left satisfied.
How do I find progressive lenses that are right for me?
The secret behind good eyeglasses with progressive lenses is having them customized by an experienced eye care professional. Because not all eyeglasses with progressive lenses are the same. When it comes to the lenses, in particular, it’s very important that everything is adjusted correctly – the refraction values, the frames, and the correct fit on the wearer’s face. So, we would definitely recommend against making a quick purchase online – even if you know your prescription or refraction values. Eyeglasses with progressive lenses have to fit correctly, and this depends on a whole range of parameters because eyeglasses are always an interplay between the wearer’s face, the lenses, and the frame. And there’s also the fact that the consumer often isn’t aware of which additional options such as blue light protection or photochromy (self-tinting lenses) might be beneficial in their case.
And there are two other important factors. The eye care professional has access to all the measuring and centering systems that are crucial when it comes to taking precise measurements of the eye. Among other things, it’s possible to precisely measure the human eye down to a hundredth of a diopter, which makes it possible to prescribe wearers eyeglass lenses that make their vision even clearer and richer in contrast. And if you do have any difficulties with getting used to the eyeglasses right away, the in-store optician is right there to support you with their advice and expertise.
How come some people love their progressive addition lenses (PALs) and others just can’t quite get used to them?
The answer is often in the prescription.
It’s important to know that lenses are not prescribed to magnify objects, but purely so that the object we are looking at is focused onto the retina. Magnification (or minification in the case of minus lenses), is a direct result of prescription power and actually an unwanted by-product of lens power.
When a PAL wearer looks down to read, they only have a small area in which to view their reading matter and so for plus lens wearers (hyperopes), the reading material they are looking at is actually magnified; they see less of the page in their limited reading zone and the higher the add power, the worse this becomes.
Often we find that some presbyopes do not appreciate their new freeform design lenses and ask why “these new and more expensive lenses are not as good as my old lenses?”
What happens, is that the wearer’s prescription is governing where and how the wearer needs to look to read. There is also prismatic effect at near point, which complicates what they can see and, more to the point, what they cannot see.
Plus lenses will create some base out prism on convergence. The image is displaced towards the apex of the prism, further complicating the reading image by necessitating slightly more convergence.
Minus prescription wearers (myopes) on the other hand, experience the opposite and generally will see a wider area through the reading zone because their prescription actually minifies the image, and they can see a lot more through their reading zone. The prismatic effect of the minus prescription will be base in (or less base out, considering the add power), which also works to benefit these short-sighted PAL wearers by lessening the amount of convergence required for reading.
Understanding this should help to realise that all wearers’ prescriptions are different and so too will be their level of acceptance of their new progressive addition lenses.
Remember, for two presbyopes with the same add (say +2.00), one a hyperope with a +2.00 distance Rx and one a myope with a -2.00 distance Rx, the power at near point will be very different – +4.00D and Plano respectively. So it is common for low add myopes to not like their PALs and prefer to remove their glasses to read.
Lens positioning
But that’s not all, when the patient undergoes a refraction, the prescription is determined by the optometrist who uses either a phoroptor head or a trial frame. Both of which use optically precise, 38mm flat form, glass bi-convex or bi-concave lenses positioned perpendicularly in front of the patient’s eyes – the perfect script in the circumstances and the perfect starting point for lens recommendation.
You see, there is another important difference to be considered here, the difference of how each individual lens is positioned on each diverse wearer.
The final position of the lenses in the spectacles will be different to the lenses used to determine the prescription in the first place. To experience the effects of this, take a powered spherical stock lens and focus it on a lensmeter, then tilt the lens and watch the focus change.
Most frames will have some pantoscopic angle
What happens with this small experiment is you have created astigmatic error on a spherical lens by tilting it, which replicates what happens when the spectacle frame is positioned on the wearers face at a different angle to the phoropter head or trial frame. Of course, there will be varying degrees of astigmatic error depending on power and how the frame sits on each individual face.
However, lens laboratories can optimise freeform lenses accordingly – to do this they use default measurements if you do not provide them. But by providing the actual position of wear measurements, your lab can personalise the lenses for your patients with lenses that place the true power in the as worn position of the frame and provide a better visual experience for the wearer, and better adaptation rates.
Consult Your Eye Care Professional
Every person is unique—and so are their eyes! Your eye care professional will assess your habits, your daily activities, and your working environment to better understand how you will be using your lenses. Your posture and face shape are also important considerations. Eye care professionals need this information so they can recommend a product that will suit your needs.
Your prescription optician is trained to advise you on the wide range of products available from the world’s largest manufacturers of corrective lenses. There are lots of progressive lenses to choose from—there’s an option to fit each person’s viewing area. Your eye care professional can recommend the product that will best suit your lifestyle. After you clearly explain your daily activities, they’ll be able to offer you a lens that’s well suited to your needs and that will be as comfortable as possible. The goal is for your lenses to give you the most natural vision possible at all working distances.
Multiple measurements are required to adjust progressive lenses. In addition to taking your prescription into account, your eye care professional will look at how the frame fits your face and other factors to make sure your progressive lenses are customized just for you.
Wear Your Glasses
This might seem obvious, but it bears repeating. It’s normal not to want to wear your glasses if you’re experiencing visual discomfort, but wearing your new glasses every day from morning to night (if possible) will help you adapt quicker. The sooner you start wearing them, the more natural your vision will become at all distances and the sooner you can enjoy all the benefits of your new lenses! For the same reason, we recommend you don’t alternate between your new and old glasses for the first few days.
Don’t Delay the Inevitable
It’s best to start wearing progressive lenses as soon as you begin to experience presbyopia, while it’s not as important to correct your near-range vision. That way it’s easier to adapt to the lenses because the overlapping areas are smaller and less bothersome. Plus, your eye lens is still flexible enough to easily accommodate changes in distance. Since presbyopia is a visual disorder that evolves over time, adapting when you only need to make small corrections will make it easier to manage further adjustments later.
Move Your Head, Not Your Eyes
Depending on the product you select, your eye care professional may take measurements so your lenses can be manufactured based on how much you move your head relative to your eye when looking at something. In general when you’re looking at something far away, you’ll need to use the upper part of your glasses. When looking at something nearby, tilt your head slightly to look through the bottom of the lens. Position what you’re looking at right in front of you. This will help you optimize your viewing areas so you don’t get annoyed by the blurry areas that may appear on the periphery.
When you want to look in a specific direction, turn your whole head instead of just moving your eyes. You might have to turn your head more than you’re used to, to avoid blurry areas on your glasses. As you’re getting used to the lenses, try not to take stairs too quickly or step down off sidewalks in a hurry because you may have trouble seeing the steps! With time, seeing with progressive lenses will become second nature.
Sources:
5 Ways to Quickly Adapt to Wearing Progressive Lenses Published by Opto-Réseau on October 10, 2018
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At Golden Eye Optometry, we view good vision care as front line protection at every age. A routine eye exam can detect more than poor vision. It can shed early light on glaucoma, macular degeneration, cataracts and diabetes.
