Understanding ocular biometric measurements

Introduction

The histograms and outliers have not revealed any non-sense data - in a statistical sense. However, the data that was collected from the eye examinations as part of the NIES in 2008 was not accompanied with a comprehensive glossary. In order to understand the measurements, and determine whether some values are outside of the possible measurable outcomes, compiling a glossary would be useful.

Keratometry - measure of corneal radius of curvature

R K-value H = Right K-value Horizontal
R K-value H Axis = Right K-value Horizontal Axis
R K-value V = Right K-value Vertical
R K-value V Axis = Right K-value vertical Axis
L K-value H = Left K-value horizontal
L K-value H Axs = Left K-value horizontal axis
L K-value V = Left K-value Vertical
L K-value V Axis = Left K-value vertical Axis

Note: I cannot determine the unit of measurement for the keratometry values with certainty through research but I suspect that the K-values are given as dioptric power (or refractive power) which would be dependent on the curvature of the cornea, and the axes measurements are in degrees.

Pachimetry - measure of central corneal thickness (CCT) (unit of measurement = micron; measurement range = 200microns to 1100microns) (http://dghtechnology.com/product/pachmate-2/)

R Pachimetry - Right Pachimetry
L Pachimetry - Left

Axial length - measurement from anterior to posterior poles of the eye (unit of measurement = mm; measurement range = 14mm to 38mm) (https://www.zeiss.com/meditec/int/products/ophthalmology-optometry/cataract/diagnostics/optical-biometry/iolmaster-500.html#technical-data)

R Axial Length = Right Axial Length
L Axial Length = Left Axial Length

Anterior chamber depth (ACD) - measurement between corneal endothelium and anterior capsule of crystalline lens (unit of measurement = mm; measurement range = 1.5mm to 6.5mm) (https://www.zeiss.com/meditec/int/products/ophthalmology-optometry/cataract/diagnostics/optical-biometry/iolmaster-500.html#technical-data)

AC Depth R = Anterior chamber depth Right
AC Depth L = Anterior chamber depth Left

Intraocular Pressure (IOP) - measurement of fluid pressure in the eye (unit of measurement = mm of mercury mmHg; measurement range = 5mmHg to 55mmHg) (http://www.reichert.com/product_details.cfm?skuId=2980&skuTk=1037022486#.WtrPFJe-nb0)

R IOP mmHg = Right IOP
L IOP mmHG = Left IOP

Cup-to-disc ratio (CDR) - measures the diameter of the optic cup relative to the total diameter of the optic disc (measurement range = 0 to 0.99) (http://bjo.bmj.com/content/bjophthalmol/82/10/1118.full.pdf)

CDR RE = cup to disc ratio right eye
CDR LE = cup to disc ratio left eye