High myopia vs low myopia: what’s the difference?

This comparison uses the IMI two-category definition. Some clinicians and studies also use a separate “moderate myopia” category. ¹

The −6.00 D boundary is a classification, not a point at which risk suddenly switches on. Your optometrist interprets each eye separately and considers the full examination.

Myopia means distant light focuses in front of the retina when the eye’s focusing system is relaxed. A more negative prescription represents more short-sightedness. For example, −7.00 D is stronger myopia than −2.00 D. ¹

Spherical equivalent is the sphere plus half the cylinder. A prescription of −5.00 sphere with −2.00 cylinder has a spherical equivalent of −6.00 D, meeting the high-myopia definition. Looking at the sphere alone can therefore be misleading.

Axial length is the distance from the front to the back of the eye. In childhood myopia, excessive eye growth is a major reason the prescription becomes more negative. Tracking that growth adds information that a glasses prescription alone cannot provide. ^{4, 5}

There is no single eye-length number that separates healthy from unhealthy eyes. An eye longer than 26 mm warrants interpretation in context, but this is not the IMI definition of high myopia and does not diagnose pathological myopia. Age, corneal and lens power, previous measurements and retinal findings all matter. ^{1, 3}

Our axial length monitoring page explains how we use repeat measurements to assess change, including during myopia-control treatment.

No. “Low” describes the current prescription, not its future speed of change. A young child starting at −1.00 D may have many years of progression ahead. Earlier onset, younger age and family history help inform risk, but no single factor predicts exactly where a child’s prescription will finish. ⁴

Do not wait for a child to reach the high-myopia range before discussing management. Conversely, an adult with high myopia may have a stable prescription and still need ongoing eye-health surveillance.

Myopia is associated with increased risk of retinal detachment, myopic maculopathy, glaucoma and some types of cataract. Risks generally rise with greater myopia, but complications can also occur at lower prescriptions. These are population associations, not a prediction that an individual will lose vision. ²

High myopia describes refractive error. Pathological myopia describes characteristic structural changes at the back of the eye, such as myopic maculopathy or a posterior staphyloma, an outward bulging of the eye wall. The two often overlap, but neither label can be substituted for the other. Pathological changes can occur without meeting the high-myopia prescription threshold. ³

Seeing clearly with glasses is reassuring about correction, but it does not rule out early disease. Likewise, laser vision correction or OrthoK can reduce the prescription needed for clear vision without removing the retinal risks associated with an elongated eye. ^{1, 3}

Glasses and contact lenses correct blur. For stronger prescriptions, lens material, frame size and fit can improve practical comfort and appearance. OrthoK or refractive surgery may be options for selected patients, but suitability is individual. Our OrthoK for high myopia and astigmatism page explains the assessment and the possibility of partial correction.

Myopia-control treatments aim to slow progression. Options for children include myopia-control spectacles, selected soft contact lenses, OrthoK and atropine. Standard single-vision glasses provide clear vision but do not provide an established myopia-control effect. It is inaccurate to say that wearing the correct glasses causes progression. ^{4, 5}

Treatment choice considers age, progression, eye health, practical handling and family preferences. Slowing progression aims to limit the final degree of myopia; it cannot guarantee prevention of future eye disease. Our comparison of myopia-control treatments explains the options in more detail.

Children and teenagers

Discuss active management from diagnosis, including when the prescription is still low. Assess the response through regular reviews rather than assuming clear vision means treatment has controlled eye growth. Outdoor time with sun protection and breaks from prolonged close work support healthy habits. Outdoor time is better established for reducing myopia onset than for controlling existing myopia, so it does not replace prescribed treatment. ^{4, 5}

Adults

Myopia can begin or continue progressing in adulthood, particularly in younger adults. However, evidence for myopia-control treatment is much stronger in children, so childhood treatment results should not be promised to adults. A changing prescription deserves assessment before deciding on management. ⁶

Older adults

A shift towards a more minus prescription does not always mean the eye is elongating. Changes in the eye’s natural lens, including cataract, can contribute. An examination helps distinguish a correction change from eye disease. Longstanding high myopia still warrants attention even if glasses have not changed for years. ^{1, 2}

The schedule depends on age, progression, treatment and findings. A child with low but progressing myopia may need more frequent appointments than an adult with a stable higher prescription. There is no automatic “annual for low, more often for high” rule.

Optometry Australia recommends ocular biometry every six months where available in myopia management, and annual dilated retinal examination for high myopia or as clinically indicated. IMI guidance also recommends annual dilation in high myopia. Treatment reviews or concerning findings can require earlier checks. ^{4, 5}

Reviews may include prescription, axial length, eye pressure, optic nerve and retinal assessment, with OCT or other imaging where indicated. Scans complement the examination; a routine central retinal image does not replace assessment of the peripheral retina.

Seek urgent eye care for new flashes, a sudden increase in floaters, a shadow or curtain across vision, or sudden loss of vision. These can indicate a retinal tear or detachment and may occur without pain. Do not wait for a routine appointment or assume you only need stronger glasses. If prompt eye care is unavailable, attend an emergency department. ⁷

If you or your child have myopia, bring previous prescriptions and eye reports so we can compare the pattern over time. We will explain the findings and discuss correction, monitoring and whether myopia management is appropriate.

Call Vision Camberwell Optometrists on 03 9882 5666. We are at 784 Burke Road, Camberwell. Our myopia management page provides an overview of assessment and care.

References

1. Flitcroft DI, He M, Jonas JB, et al. IMI: Defining and Classifying Myopia, A Proposed Set of Standards for Clinical and Epidemiologic Studies. Investigative Ophthalmology & Visual Science. 2019;60(3):M20–M30.
2. Haarman AEG, Enthoven CA, Tideman JWL, et al. The Complications of Myopia: A Review and Meta-Analysis. Investigative Ophthalmology & Visual Science. 2020;61(4):49.
3. Ohno-Matsui K, Wu PC, Yamashiro K, et al. IMI Pathologic Myopia. Investigative Ophthalmology & Visual Science. 2021;62(5):5.
4. Optometry Australia. Position Statement on Myopia Management. 2024.
5. Gifford KL, Richdale K, Kang P, et al. IMI: Clinical Management Guidelines Report. Investigative Ophthalmology & Visual Science. 2019;60(3):M184–M203.
6. Bullimore MA, Lee SSY, Schmid KL, et al. IMI: Onset and Progression of Myopia in Young Adults. Investigative Ophthalmology & Visual Science. 2023;64(6):2.
7. National Eye Institute. Retinal Detachment. Accessed 5 October 2026.