Is -4.00 Myopia Bad?
Short answer: −4.00D is moderate-to-high myopia. You're still below the clinical threshold for 'high myopia' (−6.00D), but axial length at this level is approaching 26mm — the zone where structural risk begins to increase meaningfully. Annual dilated retinal exams are important.
Where -4.00 sits in the risk spectrum
Myopia severity is better understood through axial length (the physical length of the eye in millimetres) than through the diopter number alone. Two people can have the same prescription from different amounts of axial elongation — and axial length is what determines long-term structural risk, not the diopter number itself.
| Prescription | Approx. axial length | Structural risk category |
|---|---|---|
| -1.00D | ~24.2mm | Low |
| -2.00D | ~24.7mm | Low–Moderate |
| -3.00D | ~25.2mm | Moderate |
| -4.00D | ~25.8mm | Moderate–High |
| -5.00D | ~26.1mm | High |
| -6.00D | ~26.6mm | High (IMI threshold) |
| -8.00D | ~27.5mm | Very High |
| -10.00D | ~29.0mm | Extreme |
AL–refraction mapping is approximate (±2–3D individual variation). Based on Flitcroft 2012; Tideman et al. 2016. Your row is highlighted.
Clinical perspective
At −4.00D, axial length is approximately 25.5–26.0mm — approaching the structural threshold. Tideman et al. 2016 (JAMA Ophthalmol) showed that eyes at 26mm have approximately 3× the retinal detachment risk of eyes at 24mm. Ophthalmoscopic monitoring of the peripheral retina becomes more important at this level.
For parents: what this means for a child at -4.00
A child at −4.00D should already be in active myopia management. The question at this stage is which modality is working, and whether combination therapy is needed to slow further elongation.
What to do at -4.00
Active myopia management is strongly indicated for any child at −4.00D who is still progressing. Combination therapy (two modalities) may be considered for fast progressors.
Calculate your exact progression rate
Enter age and two axial length measurements. Get progression rate, AL percentile, and projected prescription at age 18 — with and without treatment.
Check progression now →This page is for educational purposes and does not constitute medical advice. Diopter-to-axial-length conversions are approximations (±2–3D individual variation). MyopiaTracker is a decision-support tool — not a diagnostic device. Consult a qualified optometrist or ophthalmologist for personalised advice.