What are the limitations of the diopter radius?

While the diopter radius is highly validated, it should not replace clinical judgment. OpiCalc provides the latest evidence-based limitations for the diopter radius to ensure safe bedside use and optimal diagnostic accuracy.

How does the diopter radius compare to other Ophthalmology scores?

The diopter radius is a gold-standard diagnostic tool. OpiCalc provides side-by-side clinical guidance to help clinicians choose the most specific evidence-based tool for their patient's presentation.

Is the diopter radius free to use?

Yes. OpiCalc provides the diopter radius completely ad-free and optimized for mobile bedside use, ensuring you can calculate medical risk swiftly and without distraction.

OpiCalc

805 Clinical Tools

OpiCalc

AMD Severity Scale Astigmatism Assistant Diabetic Retinopathy Risk Diopter <-> Radius Glaucoma Progression Glaucoma Risk (OHTS)Graves CAS IOP Correction (CCT)ISNT Rule LogMAR <-> Snellen MRD Assessment SUN Uveitis Grading Vertex Distance

Diopter <-> Radius

Corneal Power (D)

Keratometric Result

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Millimeters (mm)

Guidelines & Evidence

Clinical Details

Section 1

Formula & Logic

Conversion Formula

Radius (mm) = 337.5 / Power (D) Power (D) = 337.5 / Radius (mm)

Standard Keratometric Index

The constant 337.5 is derived from the standardized keratometric refractive index (n = 1.3375), which accounts for the combined refractive power of the anterior and posterior corneal surfaces.

Section 2

Pearls/Pitfalls

Contact Lens Fitting

Flat corneas (low Diopter) have high radii (e.g., 40D ≈ 8.44mm)

Steep corneas (high Diopter) have low radii (e.g., 48D ≈ 7.03mm)

Base curve selection for contact lenses often starts 0.5mm to 1.0mm flatter than the mean K.

Last Comprehensive Review: 2026

Related Ophthalmology Tools

AMD Severity Scale

Astigmatism Assistant

Diabetic Retinopathy Risk

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