Electronic Stethoscopes: Have you seen a stethoscope around an eye surgeon’s neck?

Ocular auscultation is the physical exam that consists of listening to the vascular sounds of the eye by placing the stethoscope on the surface of the eyelids and surrounding structures. This is because in some conditions the eye may show a ‘murmur’ .The eye does ‘murmur’ and listening to it may help an eye surgeon not miss a diagnosis

A complete medical consultation includes a detailed history taking asking patient about everything related to his complaints and a complete examination which includes inspection , palpating ( touching and feeling whether the part is hot or cold , soft or hard) , percussion and auscultation (hearing with a stethoscope).

Ocular auscultation is the physical exam that consists of listening to the vascular sounds of the eye by placing the stethoscope on the surface of the eyelids and surrounding structures.

This is because in some conditions the eye may show a ‘murmur’ .The eye does ‘murmur’ and listening to it may help an eye surgeon not miss a diagnosis

The ‘ocular murmur’ is produced as a sound due to the turbulent flow inside the vessels around the orbit of the eye, which can originate from localised diseases  (e.g. stenosis or narrowing of the carotid artery which is the artery running from the side of the neck ) or systemic conditions (e.g. anemia).

Moreover, ocular sounds called ‘bruit’ can help diagnosis of life-threatening conditions, such as subarachnoid haemorrhage, stroke, and carotid-cavernous fistulas. Ocular bruit has sometimes been reported as the only auscultatory finding in cases of symptomatic atherothrombotic vascular disease.

‘Hearing’ what the eye is ‘murmuring’ becomes important because one may miss these dangerous conditions which can also be picked up by the eye surgeon. Some cases like eye tumours may be vascular like the following picture.

Electronic Stethoscopes: Have you seen a stethoscope around an eye surgeon’s neck?

In some cases the ‘not hearing of murmur’ may tell a surgeon that the tumour is not vascular though imaging like CT scan or MRI may suggest erroneously that the tumour is completely made of blood vessels but an auscultation reveals that it is not as in this case

Sometimes it may be medico-legally important to demonstrate that pre-operatively there was a murmur and after surgery since the whole tumour is out and all its feeding blood vessels are out and so the ‘murmur’ is no longer heard

Electronic Stethoscopes: Have you seen a stethoscope around an eye surgeon’s neck?

In some cases like fluid pressure increase around the brain, the pulsations of the eye may not be ‘heard’ pre operatively and when the pressure is released the pulsations may be ‘heard’. This is demonstrated here in this picture of an eye optic nerve elevated and no ‘pulsations’ on the electronic stethoscope and when the swelling is reduced and the eye nerve is no longer elevated like a volcano, the ‘pulsations’ are picked up by the electronic stethoscope as seen in the graph below the 3 D picture of the eye nerve (optic nerve)

Electronic Stethoscopes: Have you seen a stethoscope around an eye surgeon’s neck?

 

Despite its clinical relevance, the auscultation of the orbit is often neglected in the routine neurological examination. This is because it needs special skills and special Stethoscopes like the FB stethoscope (Ford Bowles stethoscope which has a special bell besides the routine diaphragm to hear). These are the routine hearing through a pipe or acoustic stethoscope

Another problem with acoustic stethoscopes is that the sound level is extremely low.

Electronic stethoscopes overcome these low sound levels by electronically amplifying these ‘murmur’ or ‘bruit’ sounds. Electronic stethoscopes convert of acoustic sound waves obtained through the ‘chest piece’  into electronic signals which are then transmitted from specially  designed circuits and processed for best  hearing and also allow the energy to be amplified and optimized for listening at various different frequencies.

The circuitry also allows the sound energy to be digitized, encoded and decoded, to have the ambient noise reduced or eliminated, and sent through speakers or headphones or transmitted to different areas for telemedicine

Unlike acoustic stethoscopes, transducers in electronic stethoscopes vary widely. The simplest and least effective method of sound detection is achieved by placing a microphone in the ‘chest piece’  but this gives excessive sounds from surrounding which doesn’t allow one to listen to the sound coming out of the eye and this is called ‘ambient noise interference.’

Another method comprises placement of a piezoelectric crystal (crystal which converts sound to electricity or electricity to sound) at the head of a metal stick, the bottom of the stick being in contact with a diaphragm. Some manufacturers use a piezoelectric crystal placed within foam behind a thick rubber-like diaphragm.

Another manufacturer uses an electromagnetic diaphragm with a conductive inner surface to form a capacitive sensor. This diaphragm responds to sound waves identically to a conventional acoustic stethoscope, with changes in an electric field replacing changes in air pressure. This preserves the sound of an acoustic stethoscope with the benefits of amplification. No matter what type of sophisticated circuitry or transducer is utilized, practitioners need to be prepared for a difference in the sound quality between acoustic and electronic stethoscopes.

The fact that sounds are transmitted electronically allows electronic stethoscopes to offer features such as audio or serial data output, wireless transmission, and recording of sound clips for medico-legal purposes and also for telemedicine as well as training of students or continuing medical education needs of established surgeons

As a new advance which allows one to make clinical diagnosis , one may be enthusiastic about these since it may mean less investigations if the surgeon makes clinical diagnosis which can also be documented for medico-legal purposes as well as teaching purposes without having to order expensive imaging modalities repeatedly.

I’m so happy ‘hearing’ the eye!

The author is an opthalmologist