Topcon ALADDIN HW3.0, User Manual

Page: 53 / 170

ALADDIN
- User manual Rev. 19 EN of 10/07/2019
53
11.8 Acquisition of axial length measurements (AL)
Interpretation of axial length measurements. As a rule, an interference signal is produced if the measuring
light is reflected by the retinal pigmented epithelium of the eye. This signal is utilized for axial length
measurements.
Note: Ultrasonic biometrical instruments measure the axial length as the distance between the cornea and
the inner limiting membrane, because the sound waves are reflected at this membrane. To ensure that the
measured values obtained with the ALADDIN HW3.0 are compatible with those obtained through acoustic
axial length measurement, the system automatically adjusts for the distance difference between the inner
limiting membrane and the pigmented epithelium. The displayed axial length values are thus directly
comparable to those obtained by immersion ultrasound, and no re-calculation or correction factors are
necessary. Deviations may nevertheless occur between the displayed axial lengths and ultrasonic readings
(particularly in the applanation procedure).
By selecting this mode, the acquisition environment shown in Figure 32 appears.
Figure 32
The side columns show the measurements performed for the two eyes (OD = right, OS = left).
For each acquisition, six measurements of the axial length are performed. The information displayed is the
same as in the “full sequence” acquisition. The six measurements are reported as a group result in the
collapsed view, to expand the view and see each single measurement press the arrow next to AL title to
expand/collapse the view.
Figure 33