IOLMaster — Anterior Chamber Depth.

Measurement of Anterior Chamber Depth (ACD)

WARNING: The anterior chamber depth may only be measured on phakic eyes! ACD measurements of pseudophakic eyes result in measuring errors and/or incorrect readings. The readings for pseudophakic eyes do not reflect the anterior chamber depth.

Note The keratometer measurement must be performed before anterior chamber depth measurement!

Activate ACD Mode:

• Click on the ACD icon
• Press key <V>, or
• Press the <SPACE BAR> in KER mode (KER)

• Fine adjust the IOLMaster, so that:

  • the fixation point is displayed in optimum focus in the rectangle on the screen (only the fixation point should be within the rectangle, not all the other image details).
  • the image of the cornea is not interfered with by reflections, otherwise the reading will be incorrect
  • the anterior crystalline lens is optimally visible.

As a rule, the image of the fixation point will lie between the images of the cornea and the crystalline lens. It should be close to (but not within) the optical section of the crystalline lens! For system reasons, the corneal image will be out of focus.

Note The alignment of the IOLMaster, particularly in the case of small pupils, requires a certain amount of practice on the part of the operator and cooperativeness on the part of the patient. The alignment procedure is easier on a dilated pupil (see also Tips for keratometer measurement, page 82ff.).

• Take the measurement by pressing the button on the joystick.

Note Before starting, tell the patient to look steadily at the yellow fixation light - NOT into the slit projector, as the latter will flicker during the measurement. When an acoustic signal is heard - the slit will again illuminate steadily - the measurement has been completed and the ACD values will be calculated.

Note Anterior chamber depth on the IOLMaster is interpreted as the distance between the anterior vertex of the cornea and the anterior vertex of the eye lens. Hence, the displayed distance includes the thickness of the cornea. Calculation of the anterior chamber depth requires the input of the corneal radius. If a valid keratometer measurement was performed prior to ACD measurement, the system will automatically use the measured radius for the calculation. If for any reason the IOLMaster was unable to measure the corneal curvature, a window will appear requesting you to type in the radius (if the cornea is astigmatic, the values of both principal meridians).

• Enter a value between 4.0 and 13.0 mm (use decimal point). Proceed with OK or the <ENTER> key.

  If you have selected the display Corneal K's, please enter a number between 26 and 80 (D). When entering the corneal K's, make sure that the same keratometer refractive index is set on the IOLMaster as on the keratometer used for the measurement (see Setup).

The anterior chamber depth measurement may be repeated as often as desired.

If additional measurements are taken of anterior chamber depth, the previous readings will be overwritten. To restore the last (just overwritten) readings, press shortcut keys <CTR> + <Z> ("UNDO" function).

Note The "UNDO" function itself cannot be undone.