CLINICAL TOOLS
The calculation. Without the friction.
Optical conversions and pressure change, with transparent formulas. Values stay in your browser.
Refraction
SE = S + C/2 · S′ = S + C · C′ = −C · A′ = A ± 90°
Spherical equivalent removes astigmatic information. Transposition preserves the optical prescription.
Vertex distance
Spectacle plane → corneal plane. Use each principal meridian separately for a spherocylindrical lens.
Fcornea = Fspectacle / (1 − d × Fspectacle), d [m]
Paraxial thin-lens conversion; not a contact-lens fitting or IOL power formula.
Visual acuity
logMAR = −log₁₀(decimal)
Mathematical conversion. Snellen fractions are approximate; counting fingers, hand movements and light perception cannot be converted reliably.
IOP reduction
100 × (PIO₀ − PIO₁) / PIO₀
A negative value indicates an increase. The calculation does not set an individual target pressure or correct for corneal thickness.
Check units and measurements before clinical use. These tools perform arithmetic, not diagnosis or prescribing.