System for continuous high-resolution measurement of distances in the eye

We describe a new system for accurate measurement of intraocular distances; it is used in conjunction with standard A-scan ultrasound equipment. A processing unit has been developed which enables selection of time intervals between echoes. Up to four intervals can be chosen and simultaneously measured. The output of the system is derived from a pulse duration-to-voltage converter which presents an output voltage proportional to the selected time interval. In this way variations in intraocular distances larger than about 0.01 mm can be detected.