Carlos G. Arce MD, Paulo Schor MD, Mauro Campos MD

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Traffic Light Color Distribution for Custom Color
Scales Application to Elevation, Curvature,
Power, and Thickness Maps

• Carlos G. Arce MD, Paulo Schor MD, Mauro Campos
  MD

Ocular Bioengineering and Refractive Surgery
Sectors, Institute of Vision Department of
Ophthalmology, Paulista School of
Medicine Federal University of São Paulo, Brazil
Financial Disclosure Authors do not have
financial or commercial interest in mentioned
equipments Dr Arce is Consultant Territory
Manager for Latin America, Vista Optics Limited,
Widnes, UK RD Consultant, Ziemer Group AG,
Port, Switzerland Speaker, Bausch Lomb do
Brasil, and Diretor Geral, R.E.I. Comércio
Ltda., Campinas, SP (cgarce_at_terra.com.br)
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Traffic Light Color Distribution for Custom Color
Scales

• INTRODUCTION
• Most topographic color scales use a normal fixed
  value in one of their green steps
• Orbscan II and IIZ use as default the 42 D for
  curvature and the 600 µm for pachymetry
• Galilei uses as default 43 D and 550 µm,
  respectively
• In these cases when steps are small ( 0.5 D or
  10 µm) extreme colors are achieved fast
• When steps are big ( 1.5 D or 25 µm) typical
  patterns may be diluted or missed
• Therefore, colors do not have specific or
  constant meaning in default scales
• METHOD AND PARAMETERS
• Color scales were modified by using a border
  line value as a fixed step in the yellow range
• ORBSCAN II and IIZ (Bausch and Lomb, Rochester,
  NY)
• Anterior Elevation 30 µm in the 4th yellow
  with a 7 µm step
• Posterior Elevation 50 µm in the 4th yellow
  with a 13 µm step
• Axial Keratometric Curvature 47 D in the 2nd
  yellow with a 1 D step
• Pachymetry 500 µm in the 2nd yellow with a 15
  µm step
• GALILEI (Ziemer Ophthalmics, Port, Switzerland)
• Anterior Elevation 15 µm in the 2nd yellow
  with a 5 µm step

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Traffic Light Color Distribution for Custom Color
Scales
Colors and patterns change according to size of
steps in default scales
Orbscan Default Scale (35 colors) Anterior and
Posterior Elevation 5 µm steps Axial Curvature
0.5 D steps Pachymetry 10 µm steps
Orbscan Default Scales Anterior and Posterior
Elevation 10 µm steps Axial Curvature 1.5 D
steps Pachymetry 20 µm steps
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Traffic Light Color Distribution for Custom Color
Scales
Patterns and colors become independent of size of
steps in these custome scales
Orbscan Custom Scale (35 colors) Anterior
Elevation 7 µm steps Posterior Elevation 13 µm
steps Axial Curvature 1.0 D steps Pachymetry 15
µm steps
Orbscan Custom Scale (70 colors) Anterior
Elevation 4 µm steps Posterior Elevation 6 µm
steps Axial Curvature 0.50 D steps Pachymetry 7
µm steps
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Violet ? Blue ? Green ? Yellow ? Orange ? Red
Normal Curvature and Thickness
Examples with Orbscan II
Go for it...! Green light
Flat and t Thick Cornea
Flat Cornea and Normal Thickness
Why?... Blue sign
Border line Curvature and Thickness
Caution! Yellow light
Asymmetric Border Line Curvature and Normal
Thickness
Very Asymmetric Steep Curvature and Normal
Thickness
Stop..! Red light
Very Asymmetric Steep Curvature and Thin
Pachymetry
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Violet ? Blue ? Green ? Yellow ? Orange ? Red
Steep Curvature and Normal Thickness
Examples with Galilei
Steep Asymmetric Curvature and Border Line
Thickness
Caution! Yellow light
Steep Asymmetric Anterior and Posterior Curvatures

• Default Galilei Scale
• for Anterior and Posterior Sagital Curvatures
• and for Thickness
• 2nd Yellow
• 47 D in Curvature
• 500 µm in Pachymetry

Stop..! Red light

• ANSI Scale for Anterior
• and Posterior Elevation
• Green at the middle
• Zero value for Anterior and
• Posterior Elevation

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Traffic Light Color Distribution for Custom Color
Scales

• CONCLUSIONS
• By the simple strategy of using a border line
  value as a fixed yellow step, each color of
• topographic scales begin to have the same
  meaning despite the step size or the
• type of map
• Identification of color patterns is easy and
  simplifies the interpretation of maps
• Similar approach may be used with both the
  Orbscan II, IIZ and the Galilei
• Everything above 47 D or below 500 µm (STEEP,
  THIN, or HIGH) will be orange or RED
• meaning STOP!
• Everything close to these selected border line
  value (LIMIT OF NORMALITY) will be
• YELLOW meaning CAUTION!
• Everything within the NORMAL values will be
  GREEN suggesting GO FOR IT!
• BLUE will indicate the opposite (FLAT, THICK, or
  DEEP) of the pathologic sign