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Axial Length (ALM)
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Summary of Results
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Signal-to-Noise Ratio
Signal Curves
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IOLMaster — Axial Length Measurements
ALM Signal Curves.

Valid Signal Curves

Axial Length Measurement

  • Very good signals (signal-to-noise ratio > 10)
  • Several secondary maxima visible (system specific)
  • Clear media, correctly fixating patient
  • Slight ametropia

Axial Length Measurement

  • Clear signal (SNR display GREEN)
  • Secondary maxima visible
  • Relatively clear media

Axial Length Measurement

  • Signal in "Borderline SNR" (uncertain) range (SNR display YELLOW)
  • Steep rise of measuring signal
  • Such readings are marked on the display by an exclamation mark and the message "Borderline SNR" (uncertain reading)
IOL Master warning

This reading may be used after verification and comparison with other data from this series of measurements.


Maladjustments on the Graph

Axial Length Measurement

  • Low signal (SNR display RED)
  • Error message is displayed.
  • The measuring signal cannot be clearly distinguished from the noise.
Possible reasons:
  • Unsteady (non fixating) patient
  • Strong ametropia
  • Dense medial opacity along the visual axis

Repeat the measurement!
Ask the patient to fixate steadily.


IOLMaster Help

Zeiss IOLMaster® Tutorial Version 5

Zeiss IOLMaster®

Optical Biometry

Intraocular Lens Power Calculations

East Valley Ophthalmology
5620 East Broadway Road
Mesa, Arizona 85206

Tel: +1-480-981-6111
FAX: +1-480-985-2426

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