What are the limitations of the vertex distance?

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

How does the vertex distance compare to other Ophthalmology scores?

The vertex distance 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 vertex distance free to use?

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

Vertex Distance

Spectacle Power (D)

Vertex Distance (mm)

Guidelines & Evidence

Clinical Details

Section 1

When to Use

When to Calculate

Converting spectacle prescriptions > ±4.00D to Contact Lenses

Refractive surgery planning

Surgical back-calculation of IOL power

Section 2

Formula & Logic

Effective Power Formula

F_actual = F_frame / (1 - d * F_frame) d = Vertex distance in meters

Section 3

Pearls/Pitfalls

Direction of Shift

Moving a lens CLOSER to the eye (e.g. Glasses to CL): Minus lenses become weaker (require more minus), Plus lenses become stronger (require less plus).

CAP (Closer Add Plus): Practical acronym for vertex compensation.

Last Comprehensive Review: 2026

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