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About this tool
Log spectacle powers by date and get dioptres per year, a least-squares trend line, IMI severity bands and an axial-length equivalent.
The Myopia Progression Log turns a list of dated spectacle prescriptions into a progression rate in dioptres per year, calculated as the change in spherical equivalent divided by the elapsed time. It fits a least-squares trend line across every reading, places the current power on the International Myopia Institute severity bands (myopia at -0.50 D, high myopia at -6.00 D) and converts the dioptric change into an approximate axial-length equivalent at about 2.7 D per millimetre. Parents tracking a child's glasses and adults watching their own power drift get a record worth bringing to an appointment.
Open Myopia Progression Log on AltFTool — it loads instantly in your browser.
Enter each spectacle prescription as Date, Sphere (D) and Cylinder (D), pressing Add a reading for every extra appointment.
Set Project ahead (years) — the log combines sphere with half the cylinder and fits a least-squares trend line across all readings.
Read the Progression rate in D/yr with its severity band, trend line slope and axial-length equivalent, then press Copy result.
Combines sphere and half the cylinder so astigmatism does not distort the trend.
Shows each gap between appointments as well as the least-squares slope across all readings.
Uses the published -0.50 D myopia definition, the -6.00 D high myopia definition and the -0.50 D/year progression marker.
A change of about -0.50 dioptres a year or more is the figure eye care professionals generally use to describe a progressing myope, and -0.75 D a year or faster is often called rapid. Younger children typically progress faster, so age matters as much as the number.
Add half the cylinder to the sphere. A prescription of -2.00 sphere with -1.00 cylinder has a spherical equivalent of -2.50 D. This is the single figure used to compare prescriptions over time and to define myopia severity.
Roughly 1 mm of axial elongation corresponds to about 2.5 to 3.0 dioptres in an adult-sized eye, so this log uses 2.7 D per mm. It is an approximation for context only — actual axial length is measured with optical biometry in a clinic and is the more reliable measure in children.
Several approaches are used in clinical practice, including specific spectacle and contact lens designs, orthokeratology and low-concentration atropine drops, alongside more time outdoors. Which of these is appropriate depends on age, progression rate and eye health, so it is a conversation for an optometrist or ophthalmologist rather than something to start on your own.