To increase the accuracy of intraocular lens power calculation, an int
erface between an ultrasonic A-scanning device and a personal computer
,vas created, allowing for an on-line interpretation of the ultrasonog
ram in an M-mode fashion. On the same computer display, a video record
ing of the movements of the transducer probe relative to the eye was i
nserted to obtain simultaneous information on the external alignment o
f the transducer probe. The precision of the experimental set-up in th
e measurement of intraocular distances was compared with conventional
A-scanning procedures run in automatic mode. The video controlled M-mo
de biometry was found easy to operate and to result in reproducible ax
ial length determination: The median value of the standard deviation w
as found to be below 0.04 mm as compared to a value of about 0.10 mm w
ith conventional equipment. We concluded that video controlled M-mode
biometry has great potential in the endeavour to increase the accuracy
of intraocular lens calculation.