VectorINSPECTOR 2.4.4 Vector Analysis Of The Induced Change Between Refractions (SIRC)
Data Entry Sph Cyl Axis BVD
Corneal Plane Power Sph Cyl Axis
Pre-Rx Data
Refraction 1 (Minus Cyl)
Post-Rx Data
Refraction 2 (Minus Cyl)
Intended Result
Spherical Equivalent
Refraction 1 SpEquivalent
Induced Change Sph Cyl Axis
Refraction 2 SpEquivalent
SIRC (Plus Cyl)
Change In SpEquivalent
SIRC (Minus Cyl)
Absolute Vector Angle Error (Degrees)
Ref 1 to Ref 2  Axis Change (Deg)
Intended Refractive
Direction of change
Change (IRC)
Mag of cyl error (SIRC - IRC)
IRC (minus Cyl)
Achieved Magnitude of IRC (Cylinder)
IRC (Plus Cyl)
Minus Cyl Data
Plus Cyl Data
Pre Rx
Pre Rx
Intended
Intended
Achieved
Achieved
Vector Addition of Refractions - Over-Refraction Calculation
Sphere Cylinder Axis BVD
Refraction 1
Refraction 2
Refraction 1 + 2 (Corneal Plane) Plus Cyl
Refraction 1 + 2 (Corneal Plane) Minus Cyl
Desired BVD For Over Ref Lens (mm)
Refraction 1 + 2 (Plus Cyl) At Desired BVD
Refaction 1 + 2 (Minus Cyl) At Desired BVD
VectorINSPECTOR 2.4
This module performs vector addition of two refractions
Enter Refraction One into the upper row of white boxes
Enter Refraction Two into the lower white box row
The desired Back Vertex Measurement may be entered which then presents the over-refraction
as a lens combination at the desired BVD.
Note that since the back vertex power calculation is not linear there is a difference between 
two lenses of given power at a given back vertex distance and the sum of those two lenses.
e.g. two lenses of -5.0 DS at back vertex distance 15mm each have a corneal plane power of 
-4.65 DS.  Adding these together to determine an over-refraction gives -9.30 DS.  Taking this 
corneal plane power and converting this to a BVD of 15mm gives -10.81 DS.
Pre op Keratom Pre op Refraction
Post op Keratom Post op Refraction
K1 K1 Axis K2 Sph Cyl Axis BVD K1 K1 Axis K2 Sph Cyl Axis BVD
Pre-Op K-Cyl Post-Op K-Cyl Vect Change Cornea Change Eye
Non Corneal Change 
Cyl Axis Cyl Axis Sph Cyl Axis SE Sph Cyl Axis Sphere Cyl Axis
This calculator determines the change between pre-op and post-op keratometry for cataract surgery and the refractive change.
Subtraction of the corneal change from the refractive change is the non-first corneal surface change.
This allows determination of the effect of posterior corneal and lens change after surgery.
Julian Stevens
Videokeratography / Keratometry Change In Cylinder Vector Calculator
Refractive Index
Approx Diameter of
Power Axis
Cylinder Axis Keratometric Mires (mm)
Pre K1
Pre K2
Post K1
Post K2
Sphere Cyl
Axis
Vector Delta K (Plus Cyl) @
Vector Delta K (Minus Cyl) @
VectorINSPECTOR 2.4
Back Vertex Distance Calculator
Sphere Cylinder Axis BVD
Refraction
Desired BVD
Corneal Plane Power
Power At Desired BVD
VectorINSPECTOR 2.4
Visual Acuity Conversion 6 Meters 4 Metres 20 Feet Decimal Logmar
Enter VA
Denominator
Decimal To VA
Enter Decimal
Denominator
LogMAR to VA
Enter LogMAR
VectorINSPECTOR 2.4
Denominator
 
Corneal Radius to Dioptre to Radius Calculator
Index Used
Enter Radius or Dioptric Value
Useful Refractive Indices
 
Whole Cornea (Keratometer Standard) 1.3375
 
Corneal Epithelium (Anterior Surface)  1.401
 
Corneal Stroma (Anterior) 1.38
 
Corneal Stroma (Posterior) 1.373
 
VectorINSPECTOR 2.4
 
 
 
Calculator by Mr Julian Stevens, Consultant Ophthalmologist, Moorfields Eye Hospital, 81 Britannia Walk, London N1 7RH
www.julianstevens.co.uk