In 2015, the World Health Organization (WHO) officially acknowledged myopia as a public health concern, prompting the establishment of the International Myopia Institute (IMI). The IMI was created with the goal of addressing the global challenges associated with myopia and high myopia.

The IMI recognises the need for consensus and clinical guidance amid the expanding and sometimes conflicting evidence on myopia development and management. IMI white papers, authored by leading experts, consolidate the latest research findings, provide consensus, and offer updates. By highlighting gaps in our current knowledge, they also provide a guide for ongoing and future research. Importantly, the papers help bridge the gap between research and practice, enabling busy clinicians easy access to the latest information in one place. All IMI articles and associated infographics are freely available on the IMI website.

The highly cited white papers appear every two years in a special issue of the top peerreviewed Investigative Ophthalmology and Visual Science (IOVS) journal. The first series was published in 2019; the second in 2021. Each white paper focusses on a specific aspect of myopia and these have included but have not been limited to, risk factors, prevention, genetics, interventions, impact of myopia, binocular vision and myopia, and pathological myopia.

The newly released third series of white papers, published in 2023, highlights key areas of myopia research and management that have been gaining interest. Key take home messages from the 2023 white papers are presented in this article.

MYOPIA IN INFANTS AND YOUNG CHILDREN

High myopia in infants and young children is relatively rare (prevalence <1%), but its impact on visual development and potential associated systemic or ocular disorders necessitates careful attention from eye care practitioners. This white paper provides an overview of the prevalence, aetiology, clinical evaluation, and management considerations for high myopia in this age group.1

Aetiology/Risk Factors

The aetiology and risk factors for high myopia in infants and young children differs from that of older children. One of the more notable environmental risk factors in this population is retinopathy of prematurity (ROP). Genetic factors also appear to play a larger role in this population as opposed to older groups. There are two main types of genetic aetiologies. The first one involves the interaction between numerous known genetic risk factors and environmental factors, like near work and outdoor exposure as we see in older children. The second, monogenic high myopia, results from mutations in a single gene and can occur independently or be associated with various eye and non-eye related features. Monogenic myopia can be broadly categorised into ametropic retinal dystrophies, connective tissue disorders (e.g., Stickler syndrome, Marfan syndrome), monogenic isolated high myopia, and other disorders causing corneal or lens malformations.

Clinical Evaluation

A thorough clinical evaluation is crucial to identify associated systemic or ocular disorders and assess the need for multidisciplinary involvement. Historytaking should focus on inheritance patterns, birth history, and developmental milestones. General clinical evaluation, visual acuity and colour vision evaluation, pupil reactions, and slit lamp and retinal examination can help to identify associated retinal diseases which are more common, as well as ROP, connective tissue disorders, and other ocular anomalies. Ocular biometry and imaging techniques, such as wide-angle fundus photography, optical coherence tomography (OCT), and electrophysiology also aid in diagnosing inherited retinal diseases. Ocular biometry is essential as there are many conditions such as ROP where the associated myopia tends not to be axial.

Role of Primary Eye Care Practitioners

Eye care practitioners play a crucial role in recognising the risk factors for syndromic forms of myopia in children and making timely referrals for further investigations when needed. Collaboration with ophthalmologists, clinical geneticists, genetic counsellors, and paediatricians may be necessary for a comprehensive evaluation and management plan.

Challenges of Optical Correction

Optical correction is essential for high levels of myopia to avoid amblyopia. However, the decision to prescribe correction depends on the severity of myopia and the child’s age as the emmetropisation process is still in play at this younger age and hence small amounts of myopia may not necessarily require correction.

Spectacles are the primary form of correction but contact lenses may be suitable for children with anisometropia or craniofacial abnormalities. Refractive surgery may be considered in certain cases where standard therapies are ineffective or impractical.

Management of Myopia Progression

Evidence-based recommendations are difficult to provide since this age group and syndromic forms of myopia have often been excluded from myopia progression trials.

Determining axial elongation as a prerequisite for myopia control therapy is important. For example, ROP and several forms of syndromic myopia tend to be corneal or lenticular rather than axial. Syndromic myopia often presents with high myopia by the age of five years, and progression is minimal thereafter.

Evidence from studies on infant primates suggest caution over the use of high concentrations of atropine for myopia control in the first year or two of life due to the risk of arrested development of the anterior segment. Caution must also be exercised with some monogenic forms of myopia. For example, it can have an adverse effect on cardiac treatment for Marfan’s syndrome, or photophobia can be exacerbated for patients with cone dystrophies.

Therefore, a case-by-case approach is necessary, considering the clinical heterogeneity and potential adverse effects of interventions.

Conclusion

The white paper concluded that optometrists need to be knowledgeable about the prevalence, aetiology, clinical evaluation, and management of high myopia in infants and young children. Recognising associated systemic or ocular disorders, ensuring appropriate optical correction, and considering myopia control interventions on a case-by-case basis are essential for providing optimal care to this patient population. Continuous education and collaboration with other healthcare professionals are vital for comprehensive management and improved visual outcomes.

MYOPIA IN YOUNG ADULTS

Myopia more commonly develops in childhood, but it can also manifest in adulthood between the ages of 18 and 40. This white paper aims to explore the existing evidence surrounding the onset, progression, risk factors, and management of myopia in adults, providing clinicians with valuable insights for patient care.2

When Does Juvenile-Onset Myopia Stabilise?

Stabilisation of juvenile-onset myopia typically occurs around the age of 15 for approximately half of the myopic population. By the age of 18, about 77% of individuals have reached stability, and by 21, this number rises to approximately 90%.

Prevalence of Adult-Onset Myopia

The prevalence of adult-onset myopia varies, with estimates ranging from 15% to 81%. Studies suggest that individuals with adult-onset myopia tend to end up with lower levels of myopia compared with those with childhoodonset myopia. This onset pattern is more commonly observed in college and university students in professional programs and certain occupation groups with high near work demands. The prevalence of adult-onset myopia does not appear to have changed over time.

Myopia Progression in Adults

Research evaluating myopia progression in adults, primarily university students in professional programs, has reported annual progression rates ranging from +0.02 to -0.23D in individuals aged 18 to 25 years and -0.03 to -0.18D in older participants, between 25 and 40 years of age. It is important to note that while overall mean changes in a large group of myopes are noted to be small, a proportion of adults continue to progress at clinically meaningful levels (greater than 0.5D per year). The proportion varies greatly between studies (22–56%). The annual rate of myopia progression among adult students appears to have remained stable for the past 35 years.

Risk Factors for Onset and Progression

The white paper noted that data on risk factors for adult myopia is limited and sometimes conflicting. However, it has been observed that the risk of myopia onset and progression decreases with age. University students and individuals in occupations that involve significant near work and limited outdoor time tend to have a higher risk. The rate of myopia progression appears to be similar between European and Asian adults.

Implications for Patient Care

While there are established modalities for managing myopia in children, it is challenging to predict their effectiveness in adults due to a lack of large-scale clinical studies focussing on myopia control in young adults. Conducting studies in young adults is more complex due to the lower progression rates observed, necessitating larger sample sizes and longer durations to observe meaningful effects. While kerato-refractive surgery can improve vision in individuals with myopia, it does not necessarily prevent long-term axial elongation. Consequently, undergoing surgery in the early 20s may result in the re-emergence of myopia later in life, leading to reduced long-term satisfaction and a reassessment of the costeffectiveness of the procedure.

Conclusion

Understanding myopia onset, progression, risk factors, and management in adulthood is important for clinicians in providing comprehensive care to their patients, the white paper concludes. While stabilisation of myopia typically occurs in adolescence, adult-onset myopia is not uncommon and should be carefully evaluated. Optometrists should consider the individual variations, risk factors, and limited evidence when developing management strategies for myopic adults. Further research is needed to explore effective myopia control interventions specifically designed for young adults and to enhance our understanding of this condition in the adult population.

MYOPIA AND THE CHOROID

There is emerging evidence that the choroid plays a role in both myopia development and myopia control. The growing evidence in this field warrants further attention, particularly for clinicians who may be grappling to understand how research findings might translate to clinical practice. This topic is the subject of the third IMI white paper in the 2023 series.3

Animal Models

Most of our understanding comes from animal models, which show that hyperopic defocus (e.g., the introduction of a minus lens on a chick’s eye) causes choroidal thinning, increases scleral growth, and results in myopia. The converse is true for myopic defocus. Short-term changes in the choroid resulting from this type of optical defocus predict longer-term eye growth in animal models. Choroidal thickness is influenced by physiological factors, such as diurnal rhythm and when normal diurnal variations are disrupted, refractive errors develop. The choroid secretes growth factors and neurotransmitter molecules that regulate angiogenesis, matrix turnover, and ocular growth, providing potential targets for myopia control. More research is needed to understand the mechanisms underlying these findings and explore the feasibility of optically or pharmacologically manipulating the choroid to prevent myopia.

Measuring Choroidal Change

The choroid can be difficult to visualise and quantify. Axial length can serve as a proxy for changes in choroidal thickness, but this approach has its limitations. Optical coherence tomography (OCT) enables high-resolution imaging of the choroid; however, the posterior border of the choroid is often difficult to detect, and the analysis of OCT images often requires manual segmentation. Researchers are actively working on developing automated methods. Additionally, alternative imaging techniques, like laser doppler velocimetry and optical coherence tomography angiography (OCT-A), are available for evaluating choroidal blood flow. To advance the field, it is crucial to continue developing and validating relevant instrumentation, establish measurement protocols, and enhance imaging techniques to precisely quantify changes in choroidal thickness.

Clinical Implications of Choroidal Imaging

There is no clear consensus on the role of choroidal imaging in the clinical management of myopia. Furthermore, many clinicians face obstacles when attempting to measure choroidal thickness, as current methods are costly, demanding, and time-consuming.

Findings from Human Studies

Key findings from human studies on choroidal thickness in relation to myopia include:

• Thinner choroids are generally associated with higher levels of myopia and longer axial lengths. Nasal-temporal asymmetry is consistently observed, with the nasal choroid being thinner.

• Physiological factors such as diurnal rhythm, physical activity, pregnancy, and water intake can influence choroidal thickness, although some findings are not consistent across studies.

• Pharmacological agents can cause small and transient changes in choroidal thickness. Atropine, homatropine, and alcohol have been associated with increased thickness, while tropicamide and caffeine have been linked to thinning. Other agents like phenylephrine, cyclopentolate, nicotine, and pilocarpine have conflicting evidence or show no significant changes.

• Optical factors also play a role in choroidal thickness. Exposure to certain lighting conditions, such as higher illumination or reading white text on a darker background, can increase thickness. Accommodation and reading black text on a lighter background may lead to thinning. Effects of hyperopic defocus, myopic defocus, and different light spectra or virtual reality on choroidal thickness vary across studies.

These findings highlight the complex interplay between physiological, pharmacological, and optical factors in influencing choroidal thickness and its relationship with myopia. Further research is needed to better understand these mechanisms and their clinical implications.

Implications for Myopia and Myopia Control

According to the white paper, there is insufficient evidence to determine whether short-term changes in choroidal thickness in response to optical or environmental cues, or after the use of pharmacological agents, can reliably predict longer-term changes in axial length. This makes it challenging to use choroidal thickness as a marker of efficacy for myopia control treatments.

So, what research questions still need to be addressed? The white paper suggests:

• Further investigation is needed to understand the exact nature of the choroid’s function in regulating eye growth. Is it an active mediator, a passive signal relay, a diffusion barrier, or a combination of these roles?

• Do the observed short-term changes in choroidal thickness have a lasting effect on the rate of ocular growth? Further research is required to determine if these transient changes contribute to the development and progression of myopia.

• The associations between thicker choroids and shorter eyes or less myopic refractive errors, as well as thinner choroids and longer eyes or more myopia, need to be examined to determine if they are causal relationships or simply by-products of altered growth.

Addressing these research questions will enhance our understanding of the role of choroidal thickness in myopia and myopia control, and provide valuable insights for the development of effective treatments.

GLOBAL TRENDS IN MYOPIA MANAGEMENT

A report on the results of an international survey of practitioners on myopia management attitudes and strategies in clinical practice is included in the white paper series.4 This paper reflects on how practices and attitudes regarding myopia management may have changed over the past decade based on other similar, previously published survey results. The latest results indicate that single vision spectacles and contact lenses are still the most prescribed methods of correction, although clinical activities related to myopia management, including the prescription of myopia control devices and therapies, appear to be increasing. More needs to be done to establish myopia control as the standard of care for progressive myopia around the world.

DIGEST FOR 2023

To help stakeholders keep up to date with this fast-moving field, new findings across some of the key topics covered in the previous IMI white paper series have been reviewed by experts and summarised as the IMI 2023 Digest.5

Updates on six topic areas were provided in the 2023 Digest but here, I will summarise some of the key points from just three of those topics including myopia definitions, myopia control interventions, and clinical management guidelines.

Myopia Definitions

Widely adopted definitions for myopia are important for many reasons, including diagnosis, patient management, data comparability between studies, and for meta-analysis in epidemiological research. The first IMI white paper defining myopia set refractive thresholds for myopia as ≤-0.5D and ≤-6.0D for high myopia when “ocular accommodation is relaxed”. The original paper did not stipulate the use of cycloplegia as this is difficult for primary eye care clinicians to conduct in many parts of the world, and such a definition would potentially invalidate many epidemiological studies in adults. However, this white paper update recognises that studies in children yield different results with and without cycloplegia, and a higher threshold in non-cycloplegic surveys may be more appropriate for myopia, but not a less myopic threshold for high myopia. The use of corrective formulas is also noted as a potential approach to account for differences observed when conducting clinical studies.

The concept of pre-myopia, originally defined in a previous IMI white paper6 has gained greater attention recently, particularly in Taiwan and China, where it is the most common refractive state in preschool and primary school children. Identifying predictive factors for myopia onset during the pre-myopic phase offers the potential for early intervention. More research, including longitudinal studies, is needed to understand this phase fully. Ongoing trials are exploring interventions like atropine for pre-myopia, with promising results in small trials but there is the need for larger, definitive studies.

Interventions and Clinical Management

Since the last IMI white paper series, there has been a growth in the number of specialty optical products in myopia control and more data on efficacy of existing products and combinations. As a general summary in relation to clinical trial evidence from randomised controlled trials:

• The IMI is observing enduring effects of myopia control with spectacles and dual focus contact lenses over longer trial periods and with older children (up to 15 years).

• Visual acuity (VA) and visual function are minimally impacted by treatments. For example, central VA with centre distance contact lenses, defocus incorporated multiple segments (DIMS) and highly aspherical lenslet (HAL) spectacles and different doses of atropine have been found to be comparable to control groups. Even when clinical trial subjects look through the peripheral ‘treatment’ area of myopia control spectacles, VA is reduced by less than a line.

• For orthokeratology, smaller treatment zones (i.e., smaller back optic zone diameter (BOZD)) are showing higher efficacy and we are seeing a reduction in anisometropia with more myopia control occurring on the more myopic eye.

• For combination therapy, we are finding orthokeratology combined with 0.01% atropine has higher efficacy compared to orthokeratology alone, but atropine combined with multifocal contact lenses showed no additional efficacy.

• Red light therapy is growing in popularity in China and showing high efficacy, but safety needs to be established. Violet light appears to have little effect on myopia control as observed in one study.

• Other treatments are deemed generally safe but longer-term trials are needed.

There is also increasing debate about how we should report and compare treatment effects from different studies. Due to control group differences, different study durations, and different wear time, control group data between studies is not comparable and hence the reporting of percentage efficacy (which is relative to control) may give misleading information if we are comparing one trial to the next. Few studies have compared treatments head-to-head within the same trial and hence using the same control groups. Those that have, are showing similar efficacy between treatments. Since compliance had been linked with efficacy, it is important to make a case-by-case recommendation on a treatment strategy, which is tailored to suit individual needs to maximise compliance.

CONCLUSION

By 2050, it is predicted that almost half of the global population will be myopic,7 with 10% at levels worse than -5.00 dioptres and hence at greater risk of sight-threatening complications and visual impairment. Every dioptre matters8 and hence every clinician should be supported and encouraged to introduce evidence-based myopia management to improve the quality of life and wellbeing of their patients, their families, communities, and the broader society. We commend all those who are striving to make this change and thank all those who have contributed to these efforts. We also invite all who are willing and interested to join the IMI in these efforts.

A full list of the IMI taskforce members and the complete IMI white papers can be found at myopiainstitute.org. The publication and translation costs of the clinical summary were supported by donations from the Brien Holden Vision Institute, ZEISS, EssilorLuxottica, CooperVision, Alcon, HOYA, Théa, and Oculus.

To earn your CPD hours from this article visit: mieducation.com/expanding-knowledge-theinternational-myopia-institute-white-papers-2023.

References
1. Flitcroft, I., Ainsworth, J., Chia, A., et al., IMI – Management and investigation of high myopia in infants and young children. Invest Ophthalmol Vis Sci 2023;64(6):3. DOI:10.1167/iovs.64.6.3. 2. Bullimore, M.A., Lee, S.S., Schmid, K.L., et al., IMI – Onset and progression of myopia in young adults. Invest Ophthalmol Vis Sci 2023;64(6):2. DOI:10.1167/iovs.64.6.2.
3. Ostrin, L.A., Harb, E., Nickla, D.L., et al., IMI – The dynamic choroid: New insights, challenges, and potential significance for human myopia. Invest Ophthalmol Vis Sci 2023;64(6):4. DOI:10.1167/iovs.64.6.4.
4. Wolffsohn, J.S., Whayeb, Y., Logan, N.S., et al., IMI – Global trends in myopia management attitudes and strategies in clinical practice – 2022 update. Invest Ophthalmol Vis Sci 2023;64(6):6. DOI:10.1167/iovs.64.6.6.
5. Sankaridurg, P., Berntsen, D.A., Bullimore, M.A., et al., IMI 2023 digest. Invest Ophthalmol Vis Sci 2023;64(6):7. DOI:10.1167/iovs.64.6.7.
6. Flitcroft, D.I., He, M., Jonas, J.B., et al., IMI – Defining and classifying myopia: A proposed set of standards for clinical and epidemiologic studies. Invest Ophthalmol Vis Sci 2019;60(3):M20-M30. DOI:10.1167/iovs.18-25957.
7. Holden, B.A., Fricke, T.R., Wilson, D.A., et al., Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. Ophthalmology 2016;123(5):1036-42. DOI:10.1016/j.ophtha.2016.01.006 [published Online First: 20160211].
8. Bullimore, M.A., Brennan, N.A., Myopia control: Why each diopter matters. Optom Vis Sci 2019;96(6):463-65. DOI:10.1097/OPX.0000000000001367.