myopia calculator

What this myopia calculator does

This calculator helps you translate a glasses prescription into a more standardized value called spherical equivalent (SE). SE is often used in research and clinical discussions to summarize refractive error, especially when astigmatism is present.

In addition to SE, the calculator gives:

• A simple myopia severity category (low, moderate, high, very high).
• A basic 5-year projection based on age and outdoor time.
• An optional axial-length-based risk flag if that data is available.

How the calculator works

1) Spherical equivalent formula

For each eye:
SE = Sphere + (Cylinder ÷ 2)

Example: if Sphere = -3.00 D and Cylinder = -1.00 D, then SE = -3.50 D.

2) Myopia category (based on average SE)

• Not myopic / borderline: greater than -0.50 D
• Low myopia: -0.50 D to -2.99 D
• Moderate myopia: -3.00 D to -5.99 D
• High myopia: -6.00 D to -9.99 D
• Very high myopia: -10.00 D or more

3) Simple 5-year progression estimate

The projection uses age-based averages from common epidemiologic patterns and applies a modest reduction if daily outdoor time is 2+ hours. This is not a personalized medical forecast, but it can help frame conversations with your eye-care provider.

Why myopia monitoring matters

Myopia is more than a glasses number. As myopia increases, the eye can become longer (increased axial length), and this may raise risk for retinal detachment, myopic maculopathy, glaucoma, and other complications later in life. Monitoring progression early is important for children and teens.

Evidence-based ways to slow myopia progression

• More outdoor time: especially in childhood; target at least 2 hours/day when feasible.
• Myopia-control contact lenses: including dual-focus or multifocal options in eligible patients.
• Orthokeratology: overnight corneal reshaping in selected cases with careful follow-up.
• Low-dose atropine: prescribed by clinicians when appropriate.
• Regular follow-up: serial refraction and axial length checks improve decision-making.

Important limitations

This tool does not replace a full eye exam. It does not account for corneal topography, binocular vision issues, accommodation, retinal findings, treatment adherence, family history, or ethnicity-specific risk gradients. Use it as a planning and education aid only.

Bottom line

If your child or teen has progressing myopia, early intervention can make a meaningful long-term difference. Use this calculator to understand the numbers, then take those results to a qualified eye-care professional for a personalized plan.