CPD – tools for talking myopia

At the completion of this article, the reader should be able to …

• Effectively communicate predicted myopia progression and treatment benefits using visual aids from the BHVI calculator.
• Integrate International Myopia Institute (IMI) recommendations into clinical practice through measurement and management strategies.
• Promote early intervention and prevention in childhood myopia to reduce long-term visual impairment risks.

Thomas John Naduvilath

Information Science Manager
Brien Holden Vision Institute (BHVI)
Sydney, NSW

With childhood myopia on the rise, timely communication about progression and treatment is essential. THOMAS JOHN NADUVILATH, information science manager at Brien Holden Vision Institute, explains how the organisation’s free, evidence-based tool can help optometrists support early intervention and guide informed discussions with parents and patients.

Communicating with parents and patients about the risk of myopia onset in children and the risk of myopia progression up to adulthood is a challenging part of an optometry consultation. It is important to communicate the long-term sight-threatening risks associated with progressive myopia. This would pave the way to discussions about myopia management and current myopia control treatment strategies.

To aid in communication, online resources such as Vision Simulator¹ and myopia infographics^2,3 are freely available to explain myopia, the effect of the visual environment on myopia and the classification of myopia control options. In this space, Brien Holden Vision Institute (BHVI) was the first to introduce the online myopia calculator as a communication tool to assist eyecare practitioners to communicate with parents and patients the extent of myopia progression expected with standard correction and compare it to what could be expected with several myopia control treatment options.

The updated myopia calculator is a tool developed through BHVI’s collaboration with researchers from Shanghai Eye Disease Prevention and Treatment Centre in China, Ulster University in Northern Ireland, and Linnaeus University in Sweden. The estimates shown in the calculator are derived from evidence-based models^4,5 that were built using population and clinical studies and from meta-analysis of randomised clinical trials of myopia control options.

The online Myopia Calculator (https://bhvi.org/myopia-calculator-resources) includes three tools:

1.  A myopia progression calculator

2. An axial elongation calculator

3. A risk of myopia calculator

Each tool is available by selecting its corresponding tile on the webpage. Their practical use is demonstrated in the following three case  cenarios.

Scenario 1: Myopia progression calculator

Consider a scenario where an optometric consultation takes place with an eight-year-old female of Asian descent presenting with symptoms of blurred vision. Following subjective refraction, the optometrist diagnosed -1.50 D of myopia in the right eye and -1.25 D in the left. The parent wants the child’s myopia corrected with standard single vision spectacles, but the optometrist wants to introduce the concept of myopia control to the parent, rather than just myopia correction. Here, the myopia calculator is a useful tool to aid in this communication.

Open the Myopia Calculator web page and inform the parent that this a tool developed using data on myopic children to explain expected myopia progression in children wearing standard single vision spectacles compared to expected progression with myopia control options. Select the appropriate options from the drop-down lists based on the child’s demography (ethnic descent, gender and age and the child’s prescription in the more myopic eye). Based on the selected options, a graph is generated as shown in Figure 1.

The red line on the graph – important to be explained first – represents the expected average progression of myopia in dioptres based on selected risk factors if single vison correction is provided to the child. The shaded area around the red line represents the range of uncertainty around the population average provided.

The interpretation of the red line can be communicated in multiple ways to the parent and patient, such as:

1.  Given the child’s Asian background, current age of eight years and current refractive error of -1.50 D, the child’s myopia is typically expected to increase by 4.26 dioptres between the ages of eight and 17 years if the child uses single vision spectacles/contact lenses.

2. Given the child’s Asian background, current age of eight years and current refractive error of
-1.50 D, the child’s myopia is predicted on average to be -5.76 dioptres at 17 years.

3. The child’s current myopia of -1.50 D, which is classified as low myopia⁶ is predicted to increase to -5.8 D at the age of 17 years. The average predicted myopia at 17 years being in the -3.0 D to -6.0 D category, is associated with a significantly greater risk of uncorrectable visual impairment in adulthood.⁷ This risk exponentially increases if high myopia levels (≤-6.0 D) are reached.⁷

The optometrist can then communicate how to reduce this risk using myopia control treatment options, which are provided as a drop-down list in the calculator. The treatment options reflect generic treatment strategies, not specific brands, for example spectacles with optical elements include spectacles with highly aspherical lenslets (HAL)/defocus incorporated multiple segments (DIMS)/cylindrical annular refractive elements (CARE).

Given the child’s risk of becoming highly myopic in adulthood, let’s consider the scenario where the optometrist would like to discuss spectacles with optical elements as a treatment option. Once the specific treatment option is chosen from the treatment drop-down list, the green line on the graph is updated. For each myopia control treatment, the average efficacy in dioptres is obtained from meta-analysis of randomised clinical trials. Treatment efficacy is set at an average level. The slider beside the treatment option can be moved to the left for a worse-case scenario and right for a best-case scenario. The range of the slider reflects the 95% confidence limits of the treatment efficacy.

The green line on the graph represents the expected average progression of myopia in dioptres for the given child if spectacles with optical elements is used for managing myopia.

Communicating with parents

The interpretation of the green line can be communicated in multiple ways to the parent and patient, such as:

1.  If spectacles with optical elements are chosen for myopia management, then the child’s myopia is typically expected to increase by 1.36 D between the ages of eight and 17 years as opposed to 4.26 D with single vision lenses.

2. If spectacles with optical elements are chosen for myopia management, then myopia progression is expected to slow down by 2.90 D between eight and 17 years and as a percentage this amounts to 68% reduction in progression. Research shows that reducing myopia progression by just one dioptre during childhood can lower the risk of uncorrectable visual impairment by 40%.⁸

3. If spectacles with optical elements are chosen for myopia management, then the child’s myopia is typically expected to be -2.86 D at 17 years compared to -5.76 D with single vision lenes. With myopia control, the predicted average myopia at 17 years, which is between -0.5 D and -3.0 D, is associated with less risk of uncorrectable visual impairment in adulthood than it is with single vision lenses.⁷

Scenario 2: Axial elongation calculator

The updated BHVI calculator includes an axial elongation calculator in line with the International Myopia Institute (IMI) recommendations to use both spherical equivalent and axial length measures in the management of myopia in children.⁹

Axial length measures are used to monitor myopia progression and risk of long-term complications. In terms of absolute numbers, myopia seems to commence at an axial length of 23.85 mm¹⁰ and further stabilises to 25.2-25.5 mm at 16.2-16.5 years in myopic children,¹¹ while axial length of >=26 mm is associated with a significantly greater risk of uncorrectable visual impairment in older ages.⁷ Axial elongation, the preferred endpoint for assessing myopia progression in clinical research,¹² is now gaining momentum in clinical use. Evaluating both axial elongation and myopia progression is helpful when evaluating myopia management options.

The use of the axial elongation calculator is similar to the use of the myopia progression calculator. The current measured axial length in mm is an additional input in the axial elongation calculator.

Consider the previous scenario of an optometric consultation involving a parent and a myopic child, who is an eight-year-old female of Asian descent with -1.50 D in the more myopic eye and a measured axial length of 24 mm. When these values are input, the axial length graph is updated as shown in Figure 2.

Similar to myopia progression, the red line on the graph represents the expected average elongation of axial length in mm based on selected risk factors, and this can be communicated as follows:

1. Given the child’s Asian background, current age of eight years, current refractive error of -1.50 D and axial length of 24 mm, the child’s eye length is typically expected to increase by 2.32 mm between the ages of eight and 17 years. Though axial elongation is not constant across ages, a rough calculation of 2.32/(17-8) indicates a risk of fast myopic progression (>=0.22 mm/yr).¹³

2. Given the child’s Asian background, current age of eight years, current refractive error of
-1.50 D and axial length of 24 mm, the child’s axial length is typically expected to be 26.32 mm at 17 years. Axial length >=26 mm is associated with a significantly greater risk of uncorrectable visual impairment in adulthood.⁷

Like with the myopia progression calculator, the optometrist would like to introduce spectacles with optical elements to the parent, given the high risk of complications. The green line on the axial elongation graph represents the expected average elongation of eye length in mm for the given child if spectacles with optical elements is used for managing myopia. This can be communicated in multiple ways including:

1. If spectacles with optical elements are chosen for myopia management, then the child’s axial length is typically expected to increase by 1.09 mm between the ages of eight and 17 years as opposed to 2.32 mm with single vision lenses.

2. If spectacles with optical elements are chosen for myopia management, then elongation of eye length is expected to slow down by 1.23 mm between eight and 17 years and as a percentage this amounts to 53% reduction in elongation. Both myopia progression and axial elongation show a consistent percentage reduction of >50%.

3. If spectacles with optical elements are chosen for myopia management, then the child’s axial length is typically expected to be 25.09 mm at 17 years compared to 26.32 mm with single vision lenses. With myopia management, the predicted average axial length at 17 years, which is <26 mm, is associated with less risk of uncorrectable visual impairment in adulthood.⁷

Scenario 3: The risk of myopia calculator

The risk of myopia calculator helps to communicate the importance of the preventing or delaying the onset of myopia in children who are not yet myopic. Each year of myopia prevention is more effective than three years of myopia control therapy in lowering the level of myopia that the child reaches in adulthood.¹⁴ Identifying children at risk of developing myopia allows for the early introduction of prevention measures and, where appropriate, early intervention strategies. The risk assessment tool is developed using population-based data of non-myopic children followed over time.

Consider a scenario where an optometric consultation takes place with a child, who is a seven-year-old male of Asian descent of non-myopic parents. Subjective refraction revealed 0.25 D in the right eye and 0.25 D in the left. The parent is glad that the child requires no vision correction, but the optometrist realises that the child is at risk of becoming myopic and would therefore like to introduce strategies for myopia prevention and/or early intervention.

Using the risk of myopia calculator, the optometrist can select the appropriate options from the drop-down lists based on the child’s demography (ethnic descent, gender, age, parental myopia and child’s prescription). Based on the selected options, a risk gauge is generated as shown in Figure 3.

Based on the input risk factors, the calculator estimates the probability of becoming myopic within one year as 11% and within two years as 27%. The two-year probability of becoming myopic for this child is presented as a risk value categorised as low, slightly high, moderately high and significantly high. In this situation, the child’s risk of becoming myopic in the next two years is moderately high.

If the scenario is extended to the next year (age=eight years) where the child’s refractive error may progress to  0.0 D, then the child’s risk level increases from moderately high at seven years to significantly high at eight years.

The risk gauge can be used to increase awareness of myopia, discuss preventive strategies and early intervention to delay onset.

Summary

Of course, these tools were not developed to replace the optometrist’s clinical judgment – they were developed to enhance it. By offering clear, visual projections, the myopia calculator can encourage discussions with parents and reinforce management recommendations. As myopia becomes more common, tools like this can be a valuable addition to the clinician’s toolkit, helping eyecare professionals to offer treatments strategies and preventive measures with greater clarity and confidence.

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References

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