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Recognizing causes, manifestations of ocular pain, Ophthalmology Times, 2 Dec 2013 - click link for full article - a great printout for your doc
'Dr. Margolis explained that many patients present reporting chronic pain after refractive surgery, yet with perfectly normal appearing eyes. These patients complain of the same symptoms: allodynia, hyperalgesia, burning pain, and spontaneous pain.
“After the first month, most of the abnormal sensations are not due to dryness,” he said. “If you look at the literature, most of the studies suggest that tear metrics are normal. To call it dry eye after that is doing a disservice. These changes follow neural injury. Not surprisingly, there’s nerve damage, just like in [herpes] zoster.”'
'Dr. Margolis touched on the molecular basis of nociception, specifically on the different channels that mediate nociceptive input, as well as different types of receptors that mediate different kinds of pain. These include:
•TRPV1 channel: Heat responsive TRPV1 receptors will respond to sustained stimuli, heat, and inflammatory mediators with poorly localized pain and burning.
•TRPM8 channel: Here, cold responsive receptors will respond to tear evaporation and regulate tear secretion.
•MrgprDr channel: These mechanically responsive receptors, will signal a turned-in eyelash with very acute and sharp well-localized pain.
•TLR7 channel: These receptors are itch responsive.
“Mechanoreceptors will give you sharp, acute, well localized pain,” Dr. Margolis said. “Cold receptors give you feeling of dryness in response to cold and evaporation. Polymodal receptors give you burning pain in response to chronic stimuli.”
Surgery and/or trauma increase the sensitivity of cold receptors, thus increasing the sensation of dryness. Allergies increase the sensitivity of polymodal receptors, but decrease the sensitivity of cold receptors. Finally, inflammation increases the sensitivity of the polymodal receptors.'
'The ability to distinguish between acute pain and chronic pain is very important in this assessment, Dr. Margolis continued. “They are not the same thing,” he stressed.
Acute pain is proportional to stimulus, fairly well localized, and rapidly dissipating.
Chronic pain is characterized by hyperalgesia, allodynia, and a burning sensation.
Dr. Margolis related that chronic pain is not just prolonged acute pain, but a maladaptation of the nervous system, and it is characterized by a dramatic anatomical and biochemical re-organization of the nervous system.'
'Managing chronic ocular pain includes talking to the patient, treating underlying conditions, reducing exposure and evaporative tear loss, and reducing ocular manipulation, Dr. Margolis added.
“It’s really important to talk to these patients,” he said. “No one is listening to them. All the other doctors have told them they have dry eye; they’ve put plugs in them; they’ve done various other things. That’s usually not what is going on.”
To treat chronic pain, ophthalmologists must also familiarize themselves with all of the systemic medications used to treat chronic pain, Dr. Margolis stressed. [see full article for his suggested meds]
“We’re all trained as general physicians,” he said. “There is no reason why you should not be able to do this.”'
'Dr. Margolis explained that many patients present reporting chronic pain after refractive surgery, yet with perfectly normal appearing eyes. These patients complain of the same symptoms: allodynia, hyperalgesia, burning pain, and spontaneous pain.
“After the first month, most of the abnormal sensations are not due to dryness,” he said. “If you look at the literature, most of the studies suggest that tear metrics are normal. To call it dry eye after that is doing a disservice. These changes follow neural injury. Not surprisingly, there’s nerve damage, just like in [herpes] zoster.”'
'Dr. Margolis touched on the molecular basis of nociception, specifically on the different channels that mediate nociceptive input, as well as different types of receptors that mediate different kinds of pain. These include:
•TRPV1 channel: Heat responsive TRPV1 receptors will respond to sustained stimuli, heat, and inflammatory mediators with poorly localized pain and burning.
•TRPM8 channel: Here, cold responsive receptors will respond to tear evaporation and regulate tear secretion.
•MrgprDr channel: These mechanically responsive receptors, will signal a turned-in eyelash with very acute and sharp well-localized pain.
•TLR7 channel: These receptors are itch responsive.
“Mechanoreceptors will give you sharp, acute, well localized pain,” Dr. Margolis said. “Cold receptors give you feeling of dryness in response to cold and evaporation. Polymodal receptors give you burning pain in response to chronic stimuli.”
Surgery and/or trauma increase the sensitivity of cold receptors, thus increasing the sensation of dryness. Allergies increase the sensitivity of polymodal receptors, but decrease the sensitivity of cold receptors. Finally, inflammation increases the sensitivity of the polymodal receptors.'
'The ability to distinguish between acute pain and chronic pain is very important in this assessment, Dr. Margolis continued. “They are not the same thing,” he stressed.
Acute pain is proportional to stimulus, fairly well localized, and rapidly dissipating.
Chronic pain is characterized by hyperalgesia, allodynia, and a burning sensation.
Dr. Margolis related that chronic pain is not just prolonged acute pain, but a maladaptation of the nervous system, and it is characterized by a dramatic anatomical and biochemical re-organization of the nervous system.'
'Managing chronic ocular pain includes talking to the patient, treating underlying conditions, reducing exposure and evaporative tear loss, and reducing ocular manipulation, Dr. Margolis added.
“It’s really important to talk to these patients,” he said. “No one is listening to them. All the other doctors have told them they have dry eye; they’ve put plugs in them; they’ve done various other things. That’s usually not what is going on.”
To treat chronic pain, ophthalmologists must also familiarize themselves with all of the systemic medications used to treat chronic pain, Dr. Margolis stressed. [see full article for his suggested meds]
“We’re all trained as general physicians,” he said. “There is no reason why you should not be able to do this.”'