Topical eye anesthetic

A topical eye anesthetic is a topical anestheticthat is used to numb the surface of the eye. Examples of topical eye anesthetics are oxybuprocaine, tetracaine, alcaine, proxymetacaineand proparacaine.

Some topical eye anesthetics are also used in otolaryngology, like for example oxybuprocaine.

Use of topical eye anesthetics in ophthalmology

Topical eye anesthetics are used in ophthalmologyin order to numb the surface of the eye(the outermost layers of the corneaand conjunctiva) for the following purposes:

• In order to perform a contact/applanation tonometry.
• In order to perform a Schirmer's test(The Schirmer's testis sometimes used with a topical eye anesthetic, sometimes without. The use of a topical eye anesthetic might impede the reliability of the Schirmer's test and should be avoided if possible.).
• In order to remove small foreign objects from the uppermost layer of the cornea or conjunctiva. The deeper and the larger a foreign object which should be removed lies within the cornea and the more complicated it is to remove it, the more drops of the topical eye anesthetic are necessary to be dropped onto the surface of the eye prior to the removal of the foreign object in order to numb the surface of the eye with enough intensity and duration.

Duration of topical eye anesthesia

The duration of topical eye anesthesia might depend on the type of the topical eye anesthetic and the amount of eye anesthetic being applied, but is usually about half an hour.

Topical eye anesthetics abuse

Topical eye anesthetics can cause irreversible corneal damage and even complete destruction of the cornea when excessively used (excessive use means several times a day during several days or even weeks).

Some patients who suffer from eye pain, which is often considerably strong neuropathic paincaused by the irritation of the nerves within the cornea and/or conjunctiva, unfortunately try to illegally obtain oxybuprocaine or other eye anesthetics (for example by stealingthem at their ophthalmologist, by forgingmedical prescriptionsor by trying to order it via an online pharmacy) and secretly use the substance to numb their eye pain, often ending up with irreversible corneal damage or even destruction (which is a vicious cycleand causes even much more pain). Often, such patients finally require corneal transplantation.

This behaviour of the patients could be easily prevented by correct and timely information about centrallyacting substances that drastically reduce such eye pain (see next section). Unfortunately, ophthalmologists often do not inform their patients about the correct treatment of neuropathic eye pain.

Correct medical treatment of prolonged and chronic eye pain

In case of prolonged or chronic eye pain, especially neuropathic eye pain, it is highly advisable to use rather centrallyacting substances like anticonvulsants(pregabalin, gabapentinand in more serious cases carbamazepine) or antidepressants(for example SSRIsor the tricyclic antidepressantamitriptyline) than a topical eye anesthetic because a topical eye anesthetic very quickly begins to damage the cornea if applied too often. Even very small amounts of an anticonvulsant and/or an antidepressant can almost completely stop eye pain and does not damage the eye at all.

See also

• Local anesthetic
• Local anesthesia

References

• Corneal anesthetic abuse and Candida keratitis. PubMed, 1996
• Toxic keratopathy associated with abuse of low-dose anesthetic: a case report. PubMed, 2004
• Corneal complications following abuse of topical anesthetics. PubMed, 2002
• A clinico-pathological case report of necrotizing ulcerating keratopathy due to topical anaesthetic abuse. PubMed, 2002. (Actually a very special case where a medical doctor (!) abused topical eye anesthetics, probably (s)she did not know enough about centrally acting pain relievers

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It uses material from the http://en.wikipedia.org/wiki/Topical+eye+anesthetic Wikipedia article Topical eye anesthetic.