
What is the average Axial Length for a normal eye & what is the normal range?
Average length 23.6mm; Average range for most individuals 22.0mm ‐ 24.5mm

In most individuals what is the average difference between both eyes
within 0.3mm

What is the average Axial length for children of different ages?
Newborn to 120days is 17.02mm ‐ 19.43mm; 5months to 18months is 20.09mm ‐ 20.14mm; 19months to 10years is 22.01mm ‐ 23.12mm

What are the average values for the corneal thickness, anterior chamber depth & thickness of the crystalline lens?
Corneal thickness=0.55mm; Anterior chamber depth=3.24mm; Crystalline Lens=4.63mm

What is the Sound Velocity of the Cornea?
1,641 m/sec

What is the Sound Velocity of the Aqueous/vitreous?
1,532 m/sec

Wha is the Sound Velocity of a Crystalline Lens?
1,641 m/sec (this value may decrease with age)

What is the Sound Velocity of Solid Tissue?
1,550 m/sec

What is the Sound velocity of an IOL Implant?
 PMMA  2,720 m/sec; correction factor of +0.4mm
 Silicone  980 m/sec; correction factor of 0.8mm
 Silicone  1,090 m/sec; correction factor of 0.6mm
 Acrylic  1,900 m/sec; correction factor of +0.3mm
 Acrylic  2,120 m/sec; correction factor of +0.2mm

What is the Sound Velocity of Silicone Oil?
9801,040 m/sec

What is the Sound Velocity of an Aphakic Eye?
1,532 m/sec

What is the Sound Velocity of a Phakic eye (average)?
1,550 m/sec

What is the Sound Velocity of a Pseudophakic Eye?
 1,532 m/sec +/ correction factor
 PMMA  correction factor of +0.4mm
 Silicone  correction factor of 0.8mm
 Silicone  correction factor of 0.6mm
 Acrylic  correction factor of +0.3mm
 Acrylic  correction factor of +0.2mm

What are some possible causes of an Erroneously SHORT AEL Measurement?
 Corneal compressions (contactmethod),
 Sound velocity too slow,
 Corneal gate to right of corneal spike,
 Retinal gate incorrectly positioned at spike in vitreous cavity,
 Gain set too high,
 Lens measured too thin,
 Macular thickening/detachment,
 Misalignment of the sound beam

What are some possible causes of an Erroneously LONG AEL Measurement?
 Air bubble in fluid bath (immersion method),
 Fluid bridge (contact method),
 Sound velocity too fast,
 Retinal gate to right of retinal spike,
 Gain set too low,
 Lens measured too thick,
 Posterior staphyloma eccentric to macula,
 Misalignment of the sound beam

