New applications in ultrasound technology

Historical perspective

It is only 50 years since ultrasound was first introduced to medical diagnosis; an astonishingly short period bearing in mind the impact this technique has exerted on all aspect of medical practices, including ophthalmology.

In our field, the early pioneers of ophthalmic ultrasound include Mundt and Hughes,1 Oksala and Lehtinen,2 and Gernet.3 Those workers are credited with the introduction of time-amplitude A-scan. Oksala was the first to produce results on the speed of sound in various ocular structures, and Gernet described the application of this technique in axial eye length measurements. Ossoinig4 worked extensively on the refinement and “standardisation” of A-scan and on its utilisation in tissue diagnosis.5 The fundamentals of standardised A-scan include a precise S-shaped sound amplification curve, a transducer emitting non-focused beam, and the external calibration of decibel gain by mean of “tissue model”. The technique of “standardised echography” as described by Ossoinig incorporates standardised A-scan, B-scan, and hand held continuous wave Doppler. This instrument combination coupled with well prescribed methods of examination is considered by many workers as the most accurate and reliable method of diagnostic ophthalmic ultrasound to date.

Baum and Greenwood6 jointly reported the first application of “brightness modulated” B-scan in ophthalmology. They employed an immersion method. In 1972 Bronson and Turner described the first contact B-scan,7 making ultrasound an easy and patient friendly imaging modality. This, and other significant work by Purnell8 and Coleman et al,9 led to major expansion and popularisation of B-scan.

The more recent development of duplex scanners and …