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📑 New paper digest · Clark & Wong 2026 · Am J Ophthalmol
Latest Research · Pediatric Myopia · Monitoring Metric

Monitoring Childhood Myopia: SER or Axial Length?
A 2026 Meta-Analysis Perspective

Published March 2026 in American Journal of Ophthalmology, this systematic review and meta-analysis (Clark RA, Wong RK; 70 population-based observational studies) proposes: for most children, spherical equivalent refraction (SER) should be the primary metric for myopia monitoring; axial length (AL) should be reserved for the minority entering the long-eye tail. Key findings: (1) retinal pathology risk escalates steeply at AL ≥ 26 mm (Hisayama 5-year myopic maculopathy incidence: 0.4% → 12% across AL strata); (2) but cataract and POAG risk gradients are clearer with SER than AL; (3) about 90% of myopic eyes never exceed AL 26 mm — only 10% enter the long-eye tail. This digest covers methods, normal AL variability, long-but-emmetropic eyes, the three disease comparisons, and the paper's limitations and disclosures. This is a 'new research perspective' — not a current international guideline; IMI and others still emphasize AL.

28 min readLast updated · 2026-11-05Dr. Hsiao →
The original paper discloses author consulting relationships with myopia-control manufacturers (CooperVision, Sydnexis, Vyluma; one author also consulted for Alcon on unrelated topics). This article presents the paper's perspective for awareness; it is not current clinical standard of care. IMI and other guidelines continue to treat axial length as an important monitoring metric.
In this article· 13 sectionsClick to collapse
  1. 11. Common clinic scenarios
  2. 22. Bottom line: what you really need to know
  3. 33. Common parent Q&As
  4. 44. Why this 'AL vs SER' debate?
  5. 55. How was the study conducted?
  6. 66. Finding 1: 'Normal AL' is not one number
  7. 77. Finding 2: 'long but emmetropic' healthy individuals exist
  8. 88. Finding 3: AL vs SER — which predicts which disease?
  9. 99. The '90% vs 10%' framework: the authors' core recommendation
  10. 1010. Common myths
  11. 1111. Advanced: for readers who want more depth
  12. 1212. Summary: what you can do
  13. 13References
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兒童近視監測:度數尺 vs 眼軸尺對照 Diagram: 兒童近視監測:度數尺 vs 眼軸尺對照 Two Rulers, Two Perspectives SER vs Axial Length mapped to disease risk SER ruler Spherical equivalent (refraction) 0 D Emmetropia −1 D Mild myopia −3 D Moderate −6 D High myopia ↑ Cataract ↑ Glaucoma (clearer gradient) Authors' view 90% by SER 10% by AL AL ruler Eyeball length (mm) 23 mm Emmetrope mean 25 mm +1.3 SD (~P90) 26 mm Long: top 1–3% ≥27 mm Risk escalates ↑ Retinal pathology (esp. ≥ 26 mm) Clark & Wong 2026 (70 population studies, GRADE moderate) * SER for cataract/glaucoma; AL for retinal pathology — complementary, not exclusive
Two measurements, two perspectives. Core observation of Clark & Wong 2026: SER provides clearer risk gradients for cataract and glaucoma and is relatively unaffected by height, sex, or ethnicity — suitable as the primary monitoring metric for most children. AL is most sensitive to retinal pathology, especially ≥ 26 mm, but only about 10% of myopic eyes enter that long-eye tail. The authors recommend SER as the primary monitoring metric, with AL reserved as a tracking tool for the long-tail subgroup, ideally interpreted using percentiles (age, height, sex, ethnicity adjusted) rather than a single absolute cutpoint. Conceptual adaptation of original Figures 2–3.

1. Common clinic scenarios

'Doctor, my daughter's axial length is 24.8 mm now — is she already high-risk? I read online that 26 mm means maculopathy.'

'Last time the clinic only checked refraction, not axial length — was that incomplete?'

'AL 25 mm but only −2.0 D — is that serious? Compared to another child with AL 25 mm and −5.0 D, who's at higher risk?'

With myopia-control awareness rising, axial length (AL) has become a routine clinic measurement. But parental anxiety about 'AL numbers' has followed — as if crossing a threshold guarantees blindness. The March 2026 systematic review and meta-analysis in American Journal of Ophthalmology (Clark RA, Wong RK) pooled 70 population-based studies and proposed an important observation: 'AL 26 mm' is not a universal high-risk threshold; for most children, refraction (SER) is actually a more practical monitoring metric.

This article translates the paper's key points into clinic language: how the study was done, what it found, what its limitations are, how it differs from current guidelines (e.g., IMI), and how to interpret your child's AL number honestly.

2. Bottom line: what you really need to know

30-second takeaways

  • 'AL 26 mm' is not a universal red line — normal AL varies by ≥ 1 mm across age, sex, height, and ethnicity, which is the same order of magnitude as the proposed 'high-risk' cutpoint
  • For retinal pathology: AL is a strong structural predictor (OR 3.85 per +1 mm, 95% CI 1.70–8.72); risk escalates steeply in the AL ≥ 26 mm long-eye tail
  • For cataract and POAG: SER provides a clearer risk gradient — posterior subcapsular cataract (OR 4.58), POAG (OR 2.95) both rise with deeper myopia
  • The '90% vs 10%' framing: about 90% of myopic eyes stay below AL 26 mm; only 10% enter the long-eye tail
  • 'Long but emmetropic' healthy eyes exist: eyes with AL ≥ 26 mm make up roughly the top 1–3%, and a minority of them have normal refraction, mostly in taller males — proving AL 26 mm doesn't necessarily mean disease
  • The authors recommend: SER as the primary metric for most children; AL interpreted as a percentile-based trajectory (adjusted for age, height, sex, ethnicity), not a single absolute number
  • Evidence strength: moderate (GRADE) — this is a 'new research perspective', not yet a rewritten guideline; IMI and others still emphasize AL
  • Practical approach: ophthalmology clinics still measure both, with individualized interpretation by the physician

3. Common parent Q&As

Q1: 'My child's axial length is 25 mm — should I worry?'
A: A single number doesn't tell the whole story. Per Clark & Wong (2026), normal adult mean AL is ~23.6 mm with SD ~1.1 mm — so 25 mm is roughly +1.3 SD; and children's AL increases with age: cross-sectionally, each additional year of age corresponds to ~0.12 mm longer AL (~1.2 mm over 10 years), while longitudinal cohorts following the same children report mean growth of ~0.25–0.30 mm/year. Retinal pathology risk escalates mostly at AL ≥ 26 mm — the Hisayama cohort's 5-year myopic maculopathy incidence (data from Japanese adults aged 40+): 0.4% at AL ≤ 24.9 mm; 1.8% at 25.0–25.9 mm; 6.4% at 26.0–26.9 mm; 12.0% at ≥ 27 mm (Ueda et al. 2020, JAMA Ophthalmol). AL 25 mm shouldn't trigger panic, but discuss with the ophthalmologist: (1) current refraction? (2) AL growth rate over the past year? (3) family myopia history. Trajectory matters more than absolute value.
Q2: 'Why do some clinics only check refraction, not axial length?'
A: AL measurement requires optical biometers (e.g., IOL Master, Lenstar, Pentacam AXL) — not all ophthalmology clinics or optometry offices have them. For mild early myopia, refraction alone tracks change adequately. But for progressing myopia, myopia-control candidates, or higher diopters, AL provides a more stable efficacy indicator (refraction is influenced by accommodation, pupil size, time of day; needs cycloplegia). The International Myopia Institute's 2025 instrumentation report (Jones et al., IOVS) recommends incorporating AL during myopia control. But Clark & Wong (2026) emphasize: interpret AL as a 'percentile' against the child's individual characteristics (height, sex, ethnicity), not as a single absolute number.
Q3: 'Which is more accurate — axial length or refraction?'
A: The 'accuracy' question depends on what you mean. AL is a structural measurement (eyeball front-to-back length; optical biometry has high repeatability), unaffected by accommodation, an irreversible structural indicator. Refraction is an optical measurement affected by cornea, lens, pupil, accommodation — so pediatric refractions typically need cycloplegia. Clark & Wong (2026)'s core observation: their clinical predictive power differs by disease — AL is stronger for retinal pathology (especially ≥ 26 mm long eyes); SER provides a clearer dose-response for cataract and POAG. So it's not 'which is more accurate' but 'which is more useful for the disease you want to predict'.
Q4: 'My child's AL is below 26 mm — does that mean absolutely safe?'
A: 'Absolutely safe' is too strong. Per Clark & Wong (2026): (1) retinal pathology risk is relatively low below AL 26 mm (Hisayama 5-yr myopic maculopathy: 0.4% at AL ≤ 24.9 mm; 1.8% at 25.0–25.9 mm); but (2) cataract and POAG risk don't require 'long eyes' — moderate-to-high myopia (~ −3 to −6 D and beyond) elevates both: posterior subcapsular cataract OR 4.58 (95% CI 1.35–15.55); POAG OR 2.95 (1.93–4.51) vs emmetropia. AL < 26 mm doesn't mean risk-free. And once myopia is established, AL doesn't shorten. Persistent outdoor time, follow-up, and (if needed) myopia-control treatment remain the practical strategy.
Q5: 'How strong is the 2026 evidence? Will it change current practice?'
A: 'Moderate' evidence — unlikely to change clinic SOP overnight. GRADE assessment by Clark & Wong (2026): prevalence analyses = moderate; incidence and descriptive analyses = lower. The main strength is pooling cross-ethnicity, cross-age population data. Main limitations: (1) English-only, PubMed + Embase only, no gray literature; (2) all observational, residual confounding cannot be fully excluded; (3) several analyses with k < 3 are only descriptive; (4) both authors disclose consulting with myopia-control companies (CooperVision, Sydnexis, Vyluma; one author also consulted for Alcon on unrelated topics) — stated in the paper. Current guidelines (e.g., IMI 2025) still emphasize AL; this paper is a 'challenging-mainstream' perspective requiring time to accumulate consensus. In the short term, ophthalmology clinics will continue measuring both.
Q6: 'What can I do to prevent my child's myopia from worsening?'
A: Whichever metric you ultimately monitor, prevention principles don't change: (1) ≥ 2 hours of outdoor activity daily — Taiwan's Health Promotion Administration '3010120' advice calls for ≥ 120 minutes outdoors every day, the 2025 IMI white paper on light supports about 2 hours outdoors daily, and the AAO Refractive Errors PPP notes that more time outdoors reduces the likelihood of myopia onset; but the evidence is mainly for delaying onset, and for slowing progression in children who are already myopic it is less definitive (IMI 2025; Xiong et al. 2017 meta-analysis); (2) limit near-work time, with a 10-minute break after every 30 minutes (Health Promotion Administration advice); (3) correct posture and adequate lighting; (4) regular follow-up — Taiwan's Health Promotion Administration advises at least one vision check a year; for children who are myopic or on myopia control, follow your ophthalmologist's advice on visit intervals and tests (such as refraction and AL); (5) discuss individualized myopia control (DIMS lenses, ortho-K, low-dose atropine) with the ophthalmologist; in Taiwan, low-dose atropine drops (0.1–0.5 mg/mL) are NHI-covered for children and adolescents aged 18 or younger, one bottle per 4 weeks, with no pre-approval required (Taiwan NHI drug reimbursement rules, updated 2026-10-22, section 14.9.6) — discuss the details with your doctor. The Clark & Wong (2026) 'AL vs SER' debate is about monitoring, not 'whether to intervene' — intervention rests on lifestyle + necessary treatment.
Q7: 'What does "long but not myopic" mean? Is it normal?'
A: Yes. Clark & Wong (2026) found across European, East Asian, and Singaporean cohorts: eyes of 26–27 mm (or above) make up the top 1–3% of samples, and a minority of them still have normal refraction (SER −0.50 to +0.50 D). These are usually taller males — longer eye but weaker corneal/lens power, which compensates and keeps refraction emmetropic. The implication: 'AL 26 mm' is not a universal red line — for these individuals, 26 mm is their emmetropic baseline, not pathology. This is why the authors recommend AL be interpreted by percentile (adjusted for height, sex, ethnicity), not a single absolute cutpoint.
Q8: 'For DIMS-type control methods, do we still track axial length?'
A: Yes, clinics still track AL. Reasons: (1) Most myopia-control trials track AL as a key efficacy outcome alongside refraction (e.g., the Lam 2020 BJO DIMS RCT used refraction progression as the primary outcome and axial elongation as the secondary outcome; the Al-Shammari 2026 meta-analysis analyzed both) — high repeatability, unaffected by accommodation, ideal for 'before-vs-after wearing' progression-rate comparison; (2) but for future-disease-risk counseling, Clark & Wong (2026) recommend combining with SER. In practice, clinics measure both: AL for tracking control efficacy, SER for cataract and POAG long-term risk discussion. Follow-up frequency and details should follow your child's ophthalmologist's recommendation.

4. Why this 'AL vs SER' debate?

① Myopia is a global public health issue

Holden et al. (Ophthalmology 2016) projected that by 2050, global myopia prevalence will approach 50% and high myopia ~10%. Myopia isn't just blurry vision — it elevates the risk of myopic maculopathy, retinal detachment, glaucoma, and cataract (Tideman et al. 2016, JAMA Ophthalmol; Clark & Wong 2026 refs 2, 12-14). Myopia control is fundamentally about reducing decades of future disease risk, not just lens thickness.

② Previously: AL was the preferred 'structural endpoint'

Over the past decade, myopia-control trials and guidelines (e.g., the IMI series) have progressively positioned AL as the core monitoring metric, mainly because:

  • AL is a structural measurement — unaffected by accommodation; optical biometers (e.g., IOL Master) are highly precise
  • 'AL 26 mm' has been linked with uncorrectable visual impairment and myopic maculopathy in multiple adult cohorts (e.g., Tideman 2016; Hashimoto 2019)
  • Pediatric AL growth rate reflects myopia progression — a common efficacy endpoint in trials

③ The question Clark & Wong 2026 raises

The 2026 meta-analysis asks: For whom, for which disease, and how strongly does 'AL 26 mm' predict outcomes?

  • Most myopic children never reach 26 mm — adult mean AL is ~23.6 mm (SD 1.1 mm; emmetropic eyes ~23 mm); 26 mm sits at +2 SD or beyond
  • 'Normal AL' varies substantially — by ≥ 1 mm across age, sex, height, ethnicity
  • The common diseases myopia actually causes (cataract, glaucoma) track with SER, not just AL

5. How was the study conducted?

① Search and inclusion criteria

  • Databases: PubMed + Embase (English-only)
  • Time range: Jan 1, 1990 – July 31, 2025
  • Inclusion: population-based observational studies (cross-sectional or cohort), ≥ 200 eyes (or 200 participants if single-eye analysis), reporting AL and/or SER with demographics or disease outcomes
  • Excluded: case reports, clinic-based series, non-human studies, reports lacking relevant AL/SER + outcome data
  • Results: 2432 records → 1747 deduplicated → 76 full texts → 70 studies included

② Statistical methods

  • PRISMA-compliant reporting; protocol registered on PROSPERO (CRD420251123893)
  • Random-effects model (DerSimonian-Laird τ²) with Hartung-Knapp confidence intervals; pooling required k ≥ 3; otherwise narrative synthesis
  • Risk of bias: Newcastle-Ottawa Scale; overall low to moderate
  • Certainty: GRADE; moderate for prevalence, lower for incidence and narrative
  • Software: R 4.5.1 (meta, metafor packages)
  • Pre-specified but infeasible: diagnostic accuracy analyses (SER/AL thresholds vs visual acuity) and Bayesian network meta-analysis (SUCRA ranking) — dropped due to incompatible reporting

③ Three main analysis components

  1. Normative AL variation: how do age, sex, height, ethnicity shape 'normal' AL?
  2. AL–SER relationship: how tightly do they couple? Do 'long but emmetropic' eyes exist?
  3. Which predicts which disease better: separate analyses for retinal pathology, cataract, and POAG (glaucoma)

6. Finding 1: 'Normal AL' is not one number

The first observation of Clark & Wong (2026): 'normal AL' is actually a distribution modulated by demographic factors, not a fixed value. This is the foundation of the subsequent argument.

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Factor Effect on AL (adult or child, as reported) Pooled estimate (k = studies)
Age (children) ~0.12 mm longer per year of age +0.12 (95% CI 0.08–0.17), k=3, I²=97%
Age (adults) Essentially stable (~0.014 mm/year) +0.014 (0.006–0.021), k=4, I²=93%
Height (adults) ~0.11 mm longer per +10 cm height +0.11 (0.08–0.15), k=8, I²=85%
Sex (children, female–male) Girls' eyes ~0.38 mm shorter than boys −0.38 (−0.47 to −0.29), k=6, I²=98%
Ethnicity E.g., Han children ~1.0 mm longer than Kyrgyz peers; East Asian eyes generally longer Narrative (population-specific)

* Data from Clark & Wong 2026 Table 1 and narrative; I² > 75% indicates high heterogeneity.

① Why this matters

The authors make a key point: height/sex/ethnicity create AL differences of 0.3–1.0 mm — the same order of magnitude as the 'AL 26 mm' threshold itself. A tall East Asian boy with AL 25.5 mm and a short girl with AL 25.5 mm occupy completely different 'positions in the normal distribution' — the first may still be within emmetropic norms; the second is a substantial deviation.

This grounds the authors' recommendation: 'interpret AL as a percentile, not an absolute threshold' — much like pediatric growth charts (height, weight) use age- and sex-adjusted percentiles, not single numbers.

② Pediatric AL growth rate

Pediatric AL elongates ~0.08–0.17 mm/year on average (cohort means 0.25–0.30 mm/year), corresponding to ~−0.3 D/year refractive shift. But the coupling is loose: 1 mm AL change ≈ 1 D SER change in most cohorts (the schematic-eye expectation is 2.7 D/mm, but 60% of cohorts fall in the 'weak-coupling' band |β| < 1.35 D/mm). So fast AL growth doesn't guarantee fast SER progression, and vice versa.

7. Finding 2: 'long but emmetropic' healthy individuals exist

This is the finding in Clark & Wong (2026) that most directly challenges 'AL 26 mm = red line'.

The authors examined multiple child and adult cohorts (European-ancestry Australian, Northern Irish, Beijing, Singaporean, etc.) and found: eyes reaching 26–27 mm or more make up the top 1–3% of samples, and a minority of these remain in the emmetropic range (SER −0.50 to +0.50 D). For these individuals:

  • Their eyes are longer (AL ≥ 26 mm)
  • But corneal and/or lens power is correspondingly weaker — exactly compensating
  • So vision is normal, refraction is normal, no myopia
  • They are mostly taller males

💡 Why this matters

'AL ≥ 26 mm' does not necessarily mean 'myopic' or 'high-risk'. For these 'long but emmetropic' individuals, 26 mm is their emmetropic baseline — a natural extension of body proportions, not a disease signal. This is why the authors emphasize: interpret AL relative to the individual's emmetropic baseline AL — a shorter female may baseline near 23 mm, a taller East Asian male may baseline near 24.5 mm, and reaching 26 mm represents very different 'distance from baseline' for each.

The authors illustrate with a conceptual calculation: under different 'emmetropic baseline' assumptions, reaching AL 26 mm carries very different relative risks. With emmetropic baseline 23.2 mm (short-eye baseline), RR at 26 mm ≈ 44; with baseline 23.6 mm (pooled mean), RR ≈ 25; with baseline 24.6 mm (long-eye baseline), RR ≈ 7 (Clark & Wong 2026 Figure 4, conceptual). So a fixed absolute cutpoint over-flags some groups and under-flags others.

8. Finding 3: AL vs SER — which predicts which disease?

This is the paper's main result. The authors analyzed three disease families separately:

① Retinal pathology (any myopic retinopathy)

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Predictor Pooled estimate (95% CI) k / I² Clinical interpretation
AL per +1 mm OR 3.85 (1.70–8.72) k=4, I²=69% ~4-fold higher odds per +1 mm
AL threshold near 26 mm (study-defined) vs shorter OR 121.62 (2.31–6394.29) k=3, I²=88% Huge OR but very wide CI (sparse outcomes)
SER per −1 D (descriptive) OR 1.5–1.8 k<3(敘述性) 50-80% higher odds per −1 D
SER high myopia vs emmetropia (descriptive) OR 2–12(單一離群值 54) k<3(敘述性) High myopia clearly elevated; wide range

* Data from Clark & Wong 2026 Table 2. 'Descriptive' means k < 3, no pooling possible; only trend summary.

5-year absolute incidence (Hisayama cohort)

The authors cite Ueda et al. 2020 (JAMA Ophthalmol) Hisayama 5-year incidence to translate relative risk into absolute terms:

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AL range 5-year myopic maculopathy incidence
AL ≤ 24.9 mm0.4%
AL 25.0–25.9 mm1.8%
AL 26.0–26.9 mm6.4%
AL ≥ 27.0 mm12.0%

The key takeaway: absolute risk is very low below AL 25 mm (0.4%) but rises steeply at ≥ 26 mm. So AL is a strong red-flag indicator for retinal pathology — but only when entering the long-eye tail.

② Cataract (by subtype)

The cataract analysis matters because it represents the common myopia-related disease most patients will face. Clark & Wong (2026) stratified cataract into three subtypes:

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Subtype Predictor Pooled (95% CI) Clinical interpretation
Nuclear (most common age-related) SER moderate/high vs emmetropia OR 3.09 (1.85–5.16)
HK CI 1.38–6.91, k=4
~3-fold prevalence
Nuclear AL per +1 mm (descriptive) 接近 1.0(k<3) Near-null
Posterior subcapsular (PSC) SER moderate/high vs emmetropia OR 4.58 (2.18–9.64)
HK CI 1.35–15.55, k=4
~4-5 fold prevalence
PSC AL per +1 mm (descriptive) 1.1–1.3(k<3) Modest but imprecise
Cortical SER moderate/high vs emmetropia OR 1.07 (0.80–1.43)
HK CI 0.67–1.71, k=4
Near-null

* Data from Clark & Wong 2026 Table 3 (prevalence analyses; HK CI = Hartung-Knapp adjusted CI). Incidence analyses had fewer studies (k); most were borderline or null.

Key observation: for cataract, SER is the useful predictor — and only for nuclear and PSC subtypes; cortical is unrelated. AL's overall effect on cataract is modest: near-null for nuclear, even slightly protective for cortical, and only modestly positive (but imprecise) for PSC (all descriptive, k < 3).

③ Primary open-angle glaucoma (POAG)

Scroll horizontally to read the table. With a keyboard, focus the table area and use the arrow keys.

Predictor Pooled (95% CI) k / I² Clinical interpretation
AL per +1 mm OR 1.37 (1.29–1.46) k=5, I²=0% 37% higher odds per +1 mm
SER moderate/high myopia vs emmetropia OR 2.95 (1.93–4.51) k=7, I²=59% ~3-fold higher risk
SER any myopia vs emmetropia OR 1.62 (1.34–1.95) k=6, I²=0% Even mild myopia elevates risk

* Data from Clark & Wong 2026 Table 4.

Key observation: AL is associated with POAG, but only 37% higher risk per +1 mm; whereas SER moderate/high myopia carries 2.95-fold POAG risk vs emmetropia. SER provides a more intuitive and stronger risk gradient. Clinically: even before AL reaches 26 mm, moderate/high myopia substantially raises POAG risk, requiring long-term IOP and visual-field monitoring.

9. The '90% vs 10%' framework: the authors' core recommendation

Combining the three findings, Clark & Wong (2026) propose a practical '90% vs 10%' framework:

💡 The authors' two-tier strategy

  • For ~90% of myopic eyes: SER-first monitoring — AL typically stays below 26 mm; SER provides a more practical, demography-agnostic metric for cataract, POAG, and overall management
  • For the ~10% entering the long-eye tail (AL ≥ 26 mm): AL becomes the focus — this is the retinal-pathology high-risk subgroup; needs more intensive fundus monitoring
  • How to interpret AL: as a percentile (age, height, sex, ethnicity adjusted), not a single absolute cutpoint — analogous to pediatric growth charts

The core message: for the vast majority of families and children, refraction (SER) is the most direct, meaningful monitoring metric. AL measurement is not unimportant, but functions more like an 'advanced screening tool' — its value emerges when a child's AL trajectory clearly deviates toward the long-eye tail.

⚠️ Important: this is a 'new research perspective', not yet a guideline

The Clark & Wong (2026) recommendation is not yet in international guidelines. The IMI (International Myopia Institute) 2025 reports (Jones et al. on instrumentation; Tahhan et al. IMI 2025 Digest) continue to treat AL as a core metric. So:

  • Clinics will continue to measure both and interpret jointly per individual
  • Myopia-control trials (DIMS, low-dose atropine, ortho-K) still use AL as a key efficacy outcome — 'rate of progression' comparison remains useful
  • If you see your child's AL number, don't panic, but also don't dismiss the meaning of 'increasing diopter vs emmetropia'
  • This 2026 meta-analysis is 'inviting clinical reconsideration', not 'immediate practice change'

10. Common myths

Myth 1: 'AL above 26 mm guarantees blindness.'
Truth: No. A core finding of Clark & Wong (2026) is the existence of 'long but emmetropic' healthy individuals — AL ≥ 26 mm eyes make up roughly the top 1-3%, and some of them have normal refraction and vision. AL 26 mm is not a disease threshold; retinal pathology risk depends on where the eye sits relative to the individual's emmetropic baseline. Even in the Hisayama long-term cohort, 5-year myopic maculopathy at AL 26.0–26.9 mm was 6.4% — meaning over 90% of individuals did not develop it. AL ≥ 26 mm warrants closer monitoring but does not equal 'guaranteed blindness'.
Myth 2: 'Below 26 mm = no concerns at all.'
Truth: Wrong too. Retinal pathology risk is relatively low below AL 26 mm, but cataract and POAG risks don't wait for 'long eyes' — moderate/high myopia (SER ~ −3 D and beyond) elevates risk: nuclear cataract OR 3.09; PSC OR 4.58; POAG OR 2.95 (vs emmetropia). 'AL < 26 mm' ≠ 'lifetime immunity'; deeper diopters still accumulate future ophthalmic complication risk.
Myth 3: 'AL is a hard endpoint while refraction is messed up by accommodation, so AL is always more accurate.'
Truth: Partially right. AL is a structural measurement, unaffected by accommodation — very useful for tracking short-term progression (e.g., before/after DIMS lens wear). But Clark & Wong (2026) emphasize 'long-term disease prediction' — for which SER actually has clearer associations with cataract and POAG, because these diseases involve multiple myopia-associated structural factors beyond eyeball length. So 'more accurate' depends on the question: AL tracks progression; SER often better predicts disease risk.
Myth 4: 'This 2026 paper is just industry promotion.'
Truth: Both authors disclosed consulting relationships with myopia-control companies (CooperVision, Sydnexis, Vyluma; one author also consulted for Alcon on unrelated topics), but the study itself was not industry-funded — the funding section explicitly states 'not supported by any government or non-government source.' The work also follows PRISMA, PROSPERO pre-registration, GRADE certainty, and Newcastle-Ottawa bias assessment. Disclosed conflicts ≠ proven bias, but readers should be aware. This is exactly why this article keeps emphasizing 'moderate-strength evidence' and 'guidelines haven't changed' — to provide balance, not elevate a single paper to new standard.
Myth 5: 'If SER matters more, we don't need to measure AL.'
Truth: Misread. Clark & Wong (2026) recommend a 'two-tier strategy', not 'abandon AL'. For the roughly 10% of myopic eyes entering the long-eye tail (AL ≥ 26 mm), AL's retinal-risk prediction is crucial; for tracking myopia-control efficacy (e.g., DIMS), AL remains the primary outcome. The reasonable practice: 'measure both, but interpret AL with individual characteristics and trajectory in mind'.

11. Advanced: for readers who want more depth

This section uses somewhat more technical language and suits medical students, residents, optometrists, and readers interested in methodology. General readers can stop at the previous section.

① Why does SER show subtype-specific cataract associations?

The three cataract subtypes (nuclear, cortical, PSC) respond very differently to myopia:

  • Nuclear + PSC are particularly sensitive to myopia (OR 3.09 and 4.58); PSC most impacts reading vision clinically and presents at younger ages
  • Cortical is essentially unrelated to myopia (OR 1.07) — likely because its main risk factors are sun/UV exposure, not refraction
  • Mechanistic hypothesis: myopic vitreous biochemistry and lens capsular stress distribution may accelerate nuclear and PSC opacification; cortical region is more shaped by external UV exposure than internal eye structure

② Why Hartung-Knapp and random-effects matter

  • Random-effects models assume each study has its own 'true effect' (unlike fixed-effects which assume one common value) — especially suitable for pooling across populations, ages, and designs
  • Hartung-Knapp-Sidik-Jonkman adjustment refines random-effects CIs — when k is small, traditional DerSimonian-Laird CIs tend to be too narrow; HK gives more conservative CIs with better nominal coverage
  • The study uses HK across all three disease analyses — methodologically more rigorous, which is why some CIs look wide (e.g., PSC OR 4.58, HK CI 1.35–15.55) — honest reflection of uncertainty

③ How GRADE certainty was assigned

  • GRADE (Grading of Recommendations Assessment, Development and Evaluation) is an internationally recognized evidence framework: high / moderate / low / very low
  • Observational studies start at 'low', but may be upgraded for a large effect, a dose-response gradient, or when all plausible confounding or bias would reduce the effect (GRADE Working Group, Guyatt et al. 2011)
  • In Clark & Wong (2026), the supplement (Supplementary Table S4) rates certainty qualitatively: retina × AL per mm, cataract × SER severity (nuclear, PSC), and POAG × SER severity were 'moderate'; downgrading domains were inconsistency (all three) plus risk of bias (cataract, POAG); the stated rationale includes a strong association (retina), consistent direction (cataract), and multiple population-based cohorts with a large effect (POAG)
  • Cataract × AL exposures were rated 'low': downgraded for imprecision and inconsistency (small k, wide CIs, mixed directions). The main text summarizes certainty as 'moderate for prevalence, lower for incidence and descriptive blocks'; the supplement lists only downgrading domains and does not state reasons for upgrading

④ Why diagnostic accuracy and Bayesian network meta-analysis were dropped

The authors transparently report what was pre-specified but proved infeasible:

  • Diagnostic accuracy (SER/AL thresholds vs visual acuity) — too few studies reported compatible VA + SER + AL data
  • Bayesian network meta-analysis (SUCRA ranking) — because exposure definitions (different SER/AL thresholds) lacked common comparators

This is why the paper's conclusion relies on 'pairwise OR comparison + conceptual synthesis' rather than 'network-meta ranking'. The 'SER-first' recommendation is therefore based on OR magnitudes and clinical reasoning, not statistical ranking of metrics. Readers should keep this boundary in mind.

⑤ Contrast with IMI guidelines

IMI (International Myopia Institute) is the most influential international body in myopia management. Its 2025 instrumentation report (Jones et al., IOVS) and annual digest (Tahhan et al., IOVS) still place AL as a core tracking metric, emphasizing optical biometers. Clark & Wong's (2026) view is a 'complement-and-challenge' stance — not replacing AL, but proposing:

  1. SER-first for routine monitoring and long-term disease-risk counseling in most children
  2. AL-secondary for tracking control efficacy and identifying long-tail children
  3. Interpret AL by percentile, not by a single absolute cutpoint

Time and additional studies will be needed before this recommendation enters guidelines — expect 2-5 years of follow-up work in this space.

12. Summary: what you can do

If your child's most recent exam shows AL or SER changes: don't fixate on one number — look at the trajectory. How much change in the past 6-12 months? Is it reasonable for the child's age, height, and sex? Is the child's actual vision clear? These matter more than absolute numbers.

What to prepare for the ophthalmologist visit: (1) current SER and AL values; (2) rate of change over the past year (X D progression; Y mm AL elongation); (3) parental and sibling myopia history; (4) outdoor time, near-work hours, screen time; (5) any current or past myopia-control strategies (low-dose atropine, ortho-K, DIMS lenses).

What cannot be replaced: regardless of metric choice, ≥ 2 hours of outdoor activity daily, a 10-minute break after every 30 minutes of near work, correct posture and lighting, regular follow-up, adequate sleep — these are everyday foundations of myopia prevention and control (outdoor time and breaks follow Taiwan's Health Promotion Administration '3010120' advice), unchanged by this new paper.

What not to do alone: don't self-interpret risk from online AL thresholds; don't stop myopia-control treatment on your own; don't fixate on absolute numbers while ignoring the child's overall situation; don't dismiss one metric's value because of another's. Every child is individual — final interpretation belongs in the ophthalmologist's office.

One final note: Clark & Wong (2026) offer an important reminder — AL 26 mm is not an absolute red line; 'normal AL' varies by individual; for most children, SER is a more practical monitoring metric. But this is a 'new perspective', not a 'new standard'; the ophthalmology field needs more time to build consensus. Hopefully this digest enables a deeper, more evidence-grounded conversation at your child's next visit.

References

  1. [本文主要來源] Clark RA, Wong RK. Spherical Equivalent Refraction Versus Axial Length for Monitoring Childhood Myopia and Estimating Disease Risk: A Systematic Review and Meta-Analysis. Am J Ophthalmol. 2026;286:235-247. doi:10.1016/j.ajo.2026.03.007
  2. [全球近視流行病學] Holden BA, Fricke TR, Wilson DA, et al. Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. Ophthalmology. 2016;123(5):1036-1042. doi:10.1016/j.ophtha.2016.01.006
  3. [眼軸與不可矯正視覺障礙] Tideman JWL, Snabel MC, Tedja MS, et al. Association of axial length with risk of uncorrectable visual impairment for Europeans with myopia. JAMA Ophthalmol. 2016;134(12):1355-1363. doi:10.1001/jamaophthalmol.2016.4009
  4. [Hisayama AL 與黃斑部病變] Hashimoto S, Yasuda M, Fujiwara K, et al. Association between axial length and myopic maculopathy: the Hisayama Study. Ophthalmol Retina. 2019;3(10):867-873. doi:10.1016/j.oret.2019.04.023
  5. [Hisayama 5 年發生率] Ueda E, Yasuda M, Fujiwara K, et al. Five-year incidence of myopic maculopathy in a general Japanese population: the Hisayama Study. JAMA Ophthalmol. 2020;138(8):887-893. doi:10.1001/jamaophthalmol.2020.2211
  6. [「每一屈光度都重要」] Bullimore MA, Brennan NA. Myopia control: why each diopter matters. Optom Vis Sci. 2019;96(6):463-465. doi:10.1097/OPX.0000000000001367
  7. [IMI 近視定義與分類] Flitcroft DI, He M, Jonas JB, 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
  8. [IMI 2025 儀器報告] Jones D, Chow A, Fadel D, et al. IMI—Instrumentation for myopia management. Invest Ophthalmol Vis Sci. 2025;66(9):7. doi:10.1167/iovs.66.9.7
  9. [IMI 2025 Digest] Tahhan N, Bullimore MA, He X, et al. IMI—2025 Digest. Invest Ophthalmol Vis Sci. 2025;66(12):27. doi:10.1167/iovs.66.12.27
  10. [近視控制療效綜述] Brennan NA, Toubouti YM, Cheng X, Bullimore MA. Efficacy in myopia control. Prog Retin Eye Res. 2021;83:100923. doi:10.1016/j.preteyeres.2020.100923
  11. [近視臨床試驗儀器報告] Wolffsohn JS, Kollbaum PS, Berntsen DA, et al. IMI–Clinical myopia control trials and instrumentation report. Invest Ophthalmol Vis Sci. 2019;60(3):M132-M160. doi:10.1167/iovs.18-25955
  12. [新加坡馬來族眼科研究] Singapore Malay Eye Study (SiMES). 多篇收錄於 Clark & Wong 2026 文獻 41、43。
  13. [新加坡印度族眼科研究] Singapore Indian Eye Study (SINDI). 多篇收錄於 Clark & Wong 2026 文獻 59、63。
  14. [IMI 2025 光照白皮書] Ashby R, Harb EN, Ostrin LA, et al. IMI: The role of light in refractive development and myopia: evidence from animal and human studies. Invest Ophthalmol Vis Sci. 2025;66(15):5. doi:10.1167/iovs.66.15.5
  15. [戶外活動與近視統合分析] Xiong S, Sankaridurg P, Naduvilath T, et al. Time spent in outdoor activities in relation to myopia prevention and control: a meta-analysis and systematic review. Acta Ophthalmol. 2017;95(6):551-566. doi:10.1111/aos.13403
  16. [GRADE 升級原則] Guyatt GH, Oxman AD, Sultan S, et al. GRADE guidelines: 9. Rating up the quality of evidence. J Clin Epidemiol. 2011;64(12):1311-1316. doi:10.1016/j.jclinepi.2011.06.004
  17. [國健署 3010120 原則] 衛生福利部國民健康署。兒童護眼運動 國健署推動3010120 幫助孩子從小存好視力(新聞稿,2022 年 7 月 8 日發布)。
  18. [姊妹文:DIMS 兒童近視控制] 本站延伸閱讀:兒童近視控制鏡片(DIMS)有效嗎?2026 新整合分析重點解析