Wednesday, February 27, 2008

7.25 Gee, I feel faint

(Geronimo Mercuriale, 1530-1606 -from

In 1580, Geronimo Mercuriale formulated the concept of syncope and demonstrated that it was associated with a slow pulse rate: "Ubi pulsus sit rarus semper expectanda est syncope".

The precise cause of syncope, commonly known as fainting, is hard to pin down. The mechanisms, however, are quite well-known, for at least a few hundred years. Essentially, people faint because of a mixture of (1) cardiac inhibition from enhanced parasympathetic tone, and (2) vasodilation from sympathetic withdrawal. Simply put, a slowed heart rate that reduces blood flow to the brain thereby causing a patient to faint.

Like migraine headaches, there are many triggers for syncope - officially "vasovagal syncope", for example, stress, standing upright for too long [known to happen to the Guards at the Buckingham Palace], pain, the sight of blood, hunger, prolonged hyperthermia, just to name a major few. For a few seconds, the patient feels light-headed, experiences nausea, sweating, ringing in the ears, and visual disturbances, before losing consciousness. The patient then keels over and this is when the injuries occur.

(Changing of guards - before somebody fainted.)

(Avoiding the sight of blood, Mr Patroclus?)

Feeling faint in an eye doctor's office? Of course that happens. This is often confused with feeling dizzy or having blackouts; both of which need to be neurologically evaluated. And it is not quite the "true syncope" but the "near syncope". In other words, the patient has all the signs and symptoms but stops short of passing out. This occurs usually from four activities: (1) contact tonometry (both applanation and indentation - the instruments must touch the cornea to get IOP readings); (2) first-time contact lens trial; (3) slit-lamp biomicroscopy; and (4) insertion of punctal plugs. In all situations, once the patient's eyes or eyelids are touched by the tip of the tonometer, by the doctor or an assistant when inserting a contact lens, or by the doctor's pulling down the patient's lower eyelid for a closer view of the palpebral conjunctiva or the puncta, usually at the slit-lamp, vasovagal reflex kicks in within minutes. Interestingly, most patients are young and healthy, possibly for the first time in their lives, their eyes are now manipulated by a stranger. The eyes/eyelids are indeed under some mechanical pressure albeit quite minor yet the physical reaction is quite dramatic.

First aid is to have the patient lie down while raising his/her feet or at least lower the head, so the brain can get back some much-needed blood.

Call an ambulance? Nah. The patient recovers on his/her own within minutes. Although it is not unheard of that a complete cardiac work-up is ordered if the patient ends up in the ER. And at least one patient brought a lawsuit against one eye doctor for some unspecified damages and emotional stress (remember: this is the United States of America, home to many personal injury barristers).

Some patients are disappointed that they probably won't be able to wear contacts, ever. Some are a bit embarrassed yet are quite happy to have a tale for their loved ones. Fortunately, vasovagal syncope, true or near, is never fatal.

Think about this: For patients with a history of having trouble instilling eyedrops or inserting contacts, it may not be a matter of dexterity but a mild form of vasovagal reaction.


sepehr said...

a patient with all these sympthoms occured in every time she wears contact lenses,what can do?
is there any remedy? or she will have to forget about her lenses?

EyeDoc said...

To avoid a drop in blood pressure, have the patient put the lenses on while lying down with legs raised. Or drink a lot of sports/energy drinks (e.g., Gatorade) before hand may also work.

Anonymous said...

thanks for sharing.