OpiCalc Logo

OpiCalc

989 Clinical Tools

Logo
OpiCalc
AMD Severity ScaleAstigmatism AssistantBarrett / SRK-T SimDiabetic Retinopathy RiskGlaucoma ProgressionGlaucoma Risk (OHTS)Graves CASHFA MD to VFI ConverterIOP Correction (CCT)LogMAR <-> SnellenMRD AssessmentROP Risk (G-ROP)SPEED Score (Dry Eye)SUN Uveitis GradingVertex Distance
OpiCalc Logo

OpiCalc

Open-access clinical infrastructure. Built to the standard every clinician deserves — fast, private, and free.

Zero data stored
Always free
Our mission & transparency

Get in Touch

Tool request, clinical feedback, or partnership inquiry — we read everything.

WhatsApp feedback
Email us
Partnership inquiry

© 2026 OpiCalc • Calculated Care

ProtocolsAboutPrivacyTerms

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

Related Ophthalmology Tools

AMD Severity Scale
Astigmatism Assistant
Barrett / SRK-T Sim
Diabetic Retinopathy Risk
Glaucoma Progression
Glaucoma Risk
Graves CAS
HFA MD to VFI Converter
IOP Correction
LogMAR <-> Snellen
Have feedback about this calculator?Let us know.