Appendix System Parameters
APPENDIX A
VELOCITY TABLES
VELOCITY OF SOUND USED IN
VARIOUS MEASUREMENTS
AXIAL LENGTH MEASUREMENT
Classification of Eye
Average
Velocity (m/s)
Cataract 1548
Dense Cataract 1548
Aphakic 1532
Normal (note 1) 1550
PMMA Pseudophakic (note 2) 1552
Acrylic Pseudophakic (note 2) 1549
Silicone Pseudophakic (note 2) 1507
SPECIFIC STRUCTURES
Structures
Velocity (m/s)
Cornea 1641
ACD 1532
Crystalline Lens 1640
Cataractous Lens 1629
Vitreous 1532
PMMA IOL 2718
Acrylic IOL 2120
Silicone IOL 1049
Silicone OIL 980
PMMA PSEUDOPHAKIC LENS
PMMA Lens Thickness
Average
Velocity (m/s)
(note 3)
0.5 mm 1549
0.6 mm 1551
0.7 mm (default) 1552
0.8 mm 1557
0.9 mm 1560
1.0 mm 1563
ACRYLIC PSEUDOPHAKIC LENS
Acrylic Lens Thickness (mm)
Average
Velocity (m/s)
(note 3)
0.7 mm 1547
0.8 mm (default) 1549
0.9 mm 1551
1.0 mm 1553
1.1 mm 1554
1.2 mm 1556
SILICONE PSEUDOPHAKIC LENS
Silicone Lens Thickness (mm)
Average
Velocity (m/s)
(note 3)
0.8 mm 1510
0.9 mm (default) 1507
1.0 mm 1505
1.1 mm 1502
1.2 mm 1499
1.3 mm 1496
Notes:
1. The velocity for a normal eye is not preset in the
instrument. To measure an eye requiring this
velocity the user must enter it for the tissue
velocity (TVEL).
2. The velocities preset in the system for
pseudophakic eye types are specified for the
following thickness of the pseudophakic lens:
PMMA lens thickness = 0.7 mm
Silicone lens thickness = 0.9 mm
Acrylic lens thickness = 0.8 mm.
To measure an eye with a pseudophakic lens of a
different thickness, see the appropriate table
corresponding to the pseudophakic lens for the
average tissue velocity to be used.
3. The Average Velocity is calculated based on an
axial length of 23.5 mm. These velocities are not
preset in the instrument and to measure an eye
requiring them the user must enter the value for
the tissue velocity (TVEL).
Doc # 0300-A-1901-3D Appendix - 1
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