Feature, Report

Taking optical dispensing to the next level

The third Specsavers Dispensing Conference (SDC3) was run as a four-stop, one-day conference series that started in Perth and finished in Sydney, via Melbourne and Brisbane. Popular speakers, both new and returning, were present, continuing the momentum of previous events.

Mr Richard Couch, Specsavers’ head of ophthalmic lenses and dispensing advancent, introduced the day. He acknowledged the visual challenges of modern life, especially in relation to digital devices, and summarised some of the factors affecting the Australian ophthalmic optics market.

This included the surprise federal election result, the current state of the economy, myopia and the country’s ageing population.

He counselled that any solutions offered had to be evidence-based and not subjective. He also likened young optical dispensers to children; both have a lifetime of learning ahead of them.

Despite claims that artificial intelligence will ‘take over’ the practice, he believes that the human element of dispensing is not about to be replaced. Perhaps because of that, he regards a Certificate IV in optical dispensing to be the bare minimum needed to be effective, and pressed strongly for delegates to exceed that standard.

All in a day’s work

Ms Alicia Thompson, director of professional examinations at the Association of British Dispensing Opticians (ABDO), delivered the opening presentation. As with almost all of the day’s presentations, several case studies were used to elicit possible solutions to the problems presented.

As an introduction, Thompson listed a few issues that she found could lead to unsatisfactory outcomes. They include having a favourite go-to lens regardless of a patient’s specific requirents, assuming the patient is only seeking one pair of spectacles when multiple pairs would be better, never having enough time, falling into the rut of relying on previously successful solutions and dispensing lenses to match the frame.

One basis of the complex case studies provided to delegates was to demonstrate how easy it is to make flawed assumptions about how an appliance will be used.

Questions related to the following were suggested: What are their typical daily activities? What might the best lens type be for reading and near activities? What level of eye protection is required, if any?

Do occasional gardening activities necessitate physical, solar and radiation eye protection? Do hobbies require the need for good vision of very small or very large objects at various distances? What would the most suitable lens types be?

Thompson summarised that good communication requires a person to obtain and convey information and establish a professional relationship based on valid information and trust. To obtain useful and comprehensive information, it is essential that open questions be used. That is, questions that cannot be deflected with a simple yes or no answer.

She also recommended being empathetic, as well as noting body language to confirm if information has been received, rejected or not understood. While active listening is essential, she advised a conscious effort be made to avoid staring as it suggests inattention.

When conveying information, Thompson advised to avoid jargon and check the patient’s level of understanding periodically. The use of tools such as pictures, props, drawings, and diagrams should be ployed to deepen understanding.

Importantly, all advice given should be noted on the patient’s record. This includes lens type by name, applications suggested, and the cautions and provisos issued. That is so any subsequent queries can be addressed in a well-informed manner, rather than risking a ‘he said-she said’ scenario.

Patient perceptions are coloured by their recollections of previous conversations, quality of explanations regarding needs, costs, benefits, understanding of what transpired, what their role in the final decision was and how well informed they were at the time.

She also advised all dispensers perform some form of informal, but soundly based, visual task analysis. Regardless, if such an analysis is not made and a complaint lodged subsequently, the dispenser starts on the back foot and resolution becomes more difficult.

A suggested rule-of-thumb for calculating a tentative reading addition should be based on the use of half or two-thirds of the apparent amplitude of accommodation. Ultimately though, there is no substitute for trialling the proposed final near Rx in the real world. In older cases, mobility and dexterity issues might also have to be considered.

The pre-presbyopic patient

Ms Sofia Fazal, Carl Zeiss Vision UK professional services manager, opened her presentation on presbyopia by stating that 75% of adults are presbyopic.

She estimated that at some stage, about two-thirds of presbyopes are frustrated in their interactions with ophthalmic professionals because they are not listened to adequately.

Emphasising the significance of the lens, Fazal reported that consumers are now spending more on spectacle lenses than on spectacle frames, reversing past trends. Her general advice was to discuss the features and benefits of all products being recommended or sold.

After a brief overview of accommodation, she defined the pre-presbyopia range as spanning 35 to 45 years of age, subject to significant individual variation. She advised caution with the language and descriptions used when communicating presbyopic issues to patients, especially in the context of presbyopia being an undeniable sign of advancing age.

She estimated that up to 50% of those in their mid to late 30s exhibit early signs of presbyopia, perhaps because of modern life’s increasingly complex visual demands. Generally, females are affected earlier and more severely for reasons that have yet to be determined.

In addition to some form of visual task analysis, aspects of a patient’s life and personal history should also be ascertained. This includes general and ocular health, as well as history for factors like diabetes, medications, lifestyle, smoking status, alcohol consumption and any hint of presbyopia.

Singling out electronic devices, Fazal believes that smartphone usage has altered users’ visual behaviours. That is attributable, partly at least, to the use of such devices both while static and on-the-go. That, combined with an average of 5-6 hours per day internet usage across all devices, has clinical implications.

Smaller devices generally induce shorter working distances, translating to the possibility of ocular or visual symptoms by the time the user is in their early 30s. In one small study of digital eye strain, 59% of adults reported symptoms and at least 33% of those did nothing to alleviate their problem largely because most are simply unaware of the possibilities. Symptoms included eyestrain, dry eye, headaches, blurred vision, and neck and shoulder pain.

One diagram Fazal showed of various head-neck positions, spanning a slight tilt forward to having the face almost horizontal, revealed neck loading ranging from 7 kg to 27 kg. The actual weight of the anatomy involved was not the load-limiting factor, rather the mechanical ‘disadvantage’ caused by the extreme position.

When discussing dispensing issues with patients, she recommended the LOUD approach: Listen, Observe, Understand, and Discuss. She suggested product features and benefits be linked to the patient’s lifestyle in order to help control expectations early in the dispensing process.

Under the title Dispensing for Success, Fazal divided the care of pre-presbyopia into three groups:

  • Doing nothing but taking the opportunity to educate the patient about now and the future;
  • Contact lenses, including bifocal, multifocals, PPLs and aspherics;
  • Spectacles, the option chosen by over 60% of people.

Pre-presbyopia can often be helped with low-power (+0.50 DSph) readers, anti-fatigue lenses (e.g. +0.60 DSph), or PPLs including so-called degressive designs. The latter is an ideal introduction to PPLs in general. When dispensing, the postures encouraged by an appliance warrants consideration, especially its effect on head and neck positions.

Regardless of the appliance type chosen, key benefits should include easy to wear, ease of adaptation, suitability for all-day use, and a decrease in any dry eye symptoms.Benefits for the dispenser should include ease of fitting, fewer cases of intolerance, ready availability of suitable alternatives, and a suitable pathway to full-power PPLs later.

She finished with the statent: “Enlighten before leaving.”

Polarised spectacles: Benefits

Mr Craig Johnston representing Younger Optics, the manufacturers of NuPolar-Technology polarised spectacle lenses, gave a presentation on glare, polarised light, the history of polarised appliances and where polarised lenses can be used in practice.

He defined four main types of glare: distracting glare that causes eye fatigue, discomforting glare that induces squinting, disabling glare that blocks vision and blinding glare such as that caused by light reflections from snow.

Dr Edward Land is credited with producing the first polarising plastic film in 1929. Despite that early start, it was not until 1996 that polarised prescription lenses became available. Some shortcomings in those early products meant their popularity was relatively limited.

Like earlier polarised sunglasses, NuPolar products target horizontally polarised light, such as is reflected by broad expanses of horizontal surfaces like water and snow.

The successes of earlier polarised lenses were limited by the stability and repeatability of the tints offered, poor heat resistance, delamination, incomplete UVA and UVB protection, appliance thickness and difficulty with Rx accuracy.

Delamination is a thing of the past due to the chemical bonding process that is now used between component layers of the lens. The intimacy and efficacy of that bonding also translates to a thinner lens: 1.6 mm versus the 3.5 mm of old. Several neutral tints are available, and a yellow tint for the shooting sports is also offered.

A combination of Transitions and NuPolar Technology has recently been achieved. Now the tint range, a gradient tint option and even the colour can be controlled by a suitable choice of the base lens material and Transitions technology.

The Transitions Advantage lens has a lower overall efficiency than the 97%+ claimed for the standard product and does not offer much polarisation until the tint is at its darkest. Collectively, the main products have 12 tints available and the Transitions Drivewear product has just three.

The Rx product range includes finished and si-finished lens blanks available in various tints, refractive indices and materials. Bifocal, trifocal, and progressive lens designs are also available as is a semi-finished, front-surface mirror blank in standard refractive index material. The Drivewear product is interesting in that both UV and visible light, not just UV, drive its tint density.

To head-off the common question of the availability of a ‘clear’NuPolar lens, Johnston informed the audience that such a lens tint was not possible because the iodine crystals, even when aligned during manufacture, still contributed some colour. Light losses in the polarising process probably contribute to further loss. However, a very high overall efficiency is claimed, suggesting that such losses are small.

Overall, the tint reduces brightness and the polarising properties reduce both brightness and blinding glare. Interestingly, NuPolar lenses can also be tinted further as a secondary manufacturing step, but the audience was warned that in high myopic Rxs the clear, rear lens component would be apparent to an observer looking from the side.

Provided there is an adequate thickness presented, rimless and Nyline lens retention schemes are possible without the risk of delamination.

Johnston did warn delegates to be wary of frame shapes that result in high stress points around lenses, especially square shapes, because stress patterns can become apparent without the use of a Polariscope. He also noted that some LCD displays appear black because of the polarisation inherent in LCD displays or partial polarisation by other reflecting surfaces. OLED displays have no such problems.

RX analysis and complex needs

ABDO assistant director of professional examinations Ms Miranda Richardson gave a presentation on translating Rx data into optical appliances tailored for the individual patient.

In addition to taking an Rx at face value, she posed the following questions:

  • What is the Rx for?
  • What useful information is missing?
  • What are the suitable optical solutions?
  • What potential probls might be confronted?
  • Can the Rx be made?
  • What type of frame is wanted? Is it suited to the task?
  • Is the blank size needed available?
  • What will the overall and centre lens thicknesses be?
  • Even if possible, will the appliance’s appearance be accepted?
  • Does the patient know what it will look like?
  • Will the patient wear it?

In a one-year study, 72% of lab returns were frame-related, 21% were lens-selection related and 7% were due to incorrect measurements.

Richardson advised delegates to avoid square or rectangular frames for high Rxs as the frame shape accentuates lens curvature and edge thickness.

When dealing with cosmetic issues, it is important to consider previous appliances. If the patient has had similar Rxs in the past, they will be very familiar with likely appearance, weight and thickness, and might even be able to educate the dispenser about what to expect.

Other choices include the use of aspheric or blended aspheric lenses, high index materials and frame material choices. For example, non-metal frames tend to hide edge thicknesses better.

Other practical considerations include pantoscopic tilt and the sweep of the eyelashes in relation to lens back surfaces. She also suggested frames should be selected to match their optical centres to the patient’s eye positions as closely as possible, so gross asymmetry of the mounted lenses can be avoided.

Furthermore, frame size should be appropriate to the Rx they will be used for, taking likely appearance and weight into consideration.

To illustrate the point, she displayed an Rx that incorporated 30 prism dioptres base-in prism split equally between the eyes. Despite the choice of a small, metal frame, the realities of such an Rx were impossible to hide.

Richardson also pointed out that in many cases decisions made during dispensing resulted in a considerable difference to the final outcome, especially among those with high or difficult Rxs.

KEYNOTE SPEAKERS

Alicia Thompson

Richard Couch

Miranda Richardson

Mo Jalie

Sofia Fazal

Craig Johnston

Low power aspheric lenses: The lens guru speaks

Professor Mo Jalie, visiting professor in optometry at the University of Ulster and faculty member of the Essilor Academy Europe, has published more than 200 papers on ophthalmic optics, as well as many textbooks.

Although this was not his first visit to Australia, the chance to hear him speak was a great opportunity. He did not disappoint, and his topic of Aspheric Lenses for Low Powers is one seldom aired.

Starting with spherical lenses, Jalie confirmed that a spherical +4.00 DSph lens when used 30 ° off axis (peripherally), behaved as a +4.25 / +1.00 toric lens (+5.25 D tangentially [+4.24 + {+1.00}] and +4.25 D sagittally). From a clinical and a lens design point of view, a +4.00 D lens is desired regardless of the way it is used.

Jalie used field diagrams to illustrate his lecture. They plot spherical powers at oblique vertices against ocular rotation, usually out to 30 or 40 °. Usually, the tangential and sagittal powers are plotted separately. Coincidence or near coincidence of tangential and sagittal powers is good, and coincidence with little deviation from the nominal lens power is even better.

Before the advent of readily available aspheric surface lenses, designs did exist that offered freedom from oblique astigmatic error, such as the von Rohr 1910 design.

However, the lenses were steep and as the eye rotated away from their optical centres, their optical power decreased. The von Rohr design had almost coincident sagittal and tangential powers that were close to the nominated value until extreme peripheral viewing angles were used.

In 1917, Tillyer of American Optical (AO) designed a lens series that was free from mean oblique error (MOE) by forming a small circle of least confusion.

Tillyer was also responsible for the Percival lens, a product named after an English ophthalmologist who requested a lens that was free from MOE (the tangential [+0.15 D @ 35 °] and sagittal [-0.15 D @ 35 °] errors were almost equal and opposite, as well as being small until eccentricity was well beyond 30 °). It has a flatter lens form than Tillyer’s earlier design.

The so-called Point-Focal lens is a steeper design that has zero off-axis error (the difference between tangential and sagittal errors is zero). For example, the tangential and sagittal errors are coincident but not zero, and their overlapping plots deviate from the nominal power increasingly and negatively with increasing eccentricity.

Much later (1967) Davis, also from AO, designed a flatter lens that was virtually free from tangential error (a minimal tangential error form, but with detectable sagittal error [–0.25 D @ 40 °] raining).

Jalie then switched to aspheric surfaces based on conic sections using equations derived originally by Baker but still used extensively in CLs and descriptions of cornea shape. He reported that for eccentric points, tangential surface power decreases more rapidly than sagittal surface power. Generally, aspheric lenses are designed to minimise oblique astigmatism.

Taking the conic section extre of a hyperbola as a surface shape, it is possible to have a thinner, flatter lens that performs similarly to a spherical lens, though it has to be closer to the eye.

Lenses based on an ellipse tend to be good optically out to about 30° eccentric, after which performance declines rapidly due to increasing tangential astigmatism. Initially, aspheric lenses ployed aspheric front surfaces, but that has changed to a back-surface preference.

When toric lenses are considered in a similar vein to spherical lenses, it is desired that the astigmatic Rx rains constant regardless of the eccentricity of viewing.

That is not possible with conventional surface shapes because of meridional differences in the cylinder power delivered. With increasing eccentricity, the cylinder delivered in the 90 ° meridian is greater than that delivered in the 180 ° meridian.

Atoric surfaces

Enter atoric surfaces; designs that are an extension of aspheric design technology that optimise for both the sphere and cylinder powers of a lens. The result is a wider field-of-view and better vision quality, because the cylinder power varies little with direction of gaze.

They outperform best-form lenses (based on spherical surfaces) and aspheric lenses that are rotationally symmetric. Usually, they ploy two oblate ellipse sections.

It is also possible to have both lens surfaces aspherical with the aim of restoring off-axis performance, i.e. a bi-asphere, but in spherical Rxs there is little advantage. However, in toric Rxs there can be an advantage.

Tackling an old marketing furphy, Jalie raised the subject of point-of-sale lens distortion donstrators that purport to show the superiority of aspheric spectacle lenses. Those donstrators usually ploy high plus lenses (one spherical, one aspherical) for comparison purposes.However, because the practical exit pupil of the eye-spectacle lens optical system is in the eye when viewing through the paired lenses in the demonstrator, the comparison is invalid, unrealistic, and probably also somewhat dependent on viewing distance.

He also confirmed that when tilting aspheric spectacle lenses, it is necessary to offset the fitting height of the lens to compensate for the optical effects of the tilt. The agreed rule-of-thumb based on optical calculations is lowering the lens’ optical centre by 0.5 mm for each degree of tilt from the vertical.

His parting suggestions were that aspheric lenses were desirable in Rx above 7.25 D for comfort, aberration, and astigmatism reasons and they should also be considered for virtually all other Rxs.

Generally, the appearance of the lenses is superior, it is now possible to personalise all Rxs but he counselled his audience to pay particular attention to their centration, pantoscopic tilt, and vertex distance when fitted.

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