Exposing the LASIK Scam

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 Post subject: Impaired Tear Secretion or ?Phantom? Cornea?
PostPosted: Sun Aug 19, 2007 1:20 am 
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Eye Dryness Sensations After Refractive Surgery: Impaired Tear Secretion or ?Phantom? Cornea?

Journal of Refractive Surgery Vol. 23 No. 6 June 2007
Carlos Belmonte, MD, PhD

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A negative side effect of this therapy is the high incidence of abnormal sensations that occur to the ocular surface. The most common complaint is ocular dryness, which appears in >40% of patients who undergo PRK and LASIK, particularly on waking.


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The application during photorefractive surgery of a laser beam to the stromal surface, after debridement of the epithelium (PRK) or cutting a corneal flap with a microkeratome (LASIK), incurs damage to the corneal nerves.3 Corneal nerves are present in the external third of the stroma and form a dense subepithelial plexus from which branches ascend, traversing the Bowman?s layer to enter the basal epithelial layer.


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Corneal denervation, by eliminating this continuous sensory input, is expected to decrease the reflexly maintained basal flow of tears and change their composition.


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Nerve damage is evidenced morphologically by an altered appearance of stromal and subepithelial nerve trunks seen with confocal microscopy in operated human corneas and by a reduction in their number, which persists months after surgery.27,28 Experimental studies in animals have additionally shown that after injury of the peripheral branches, some of the corneal trigeminal ganglion neurons die, whereas the rest initiate, with variable success, the regeneration of their peripheral, cut stumps and form nerve-end neuromas in the borders of the wound.29,30 Also, peripheral axons of uninjured neurons innervating neighboring territories sprout and invade temporarily the denervated areas with new axonal branches. 14,29,31 Furthermore, injured nerves exhibit altered functional properties. In intact afferent fibers, impulse generation occurs exclusively at the sensory endings.32 Nerve fibers cut during surgery lose their distal end, ie, the transduction area where specific stimuli are converted into a discharge of propagated nerve impulses. Consequently, responsiveness to natural stimuli is impaired. It is well established that axotomized sensory neurons also change the expression of ion channels involved in the transduction and generation of nerve impulses.33,34 This leads to abnormal intrinsic electrical excitability at injured nerve stumps, which causes appearance of spontaneous impulses (ectopic activity) and abnormal responsiveness to minimal stimuli at damaged sensory fibers, producing dysesthesias and neuropathic pain of peripheral origin. This neuropathic pain develops spontaneously or is evoked by stimuli that under normal conditions would not elicit such a response, applied on or near the cut end of an injured sensory nerve, giving rise to abnormal sensations including the ?phantom limb? sensations reported by patients with amputated extremities.35


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Moreover, the spontaneous sensations of eye dryness, soreness to touch, and other dysesthesias seen in LASIK patients postoperatively may not be primarily due to real surface dryness consecutive to a reduced sensory input after denervation, but rather to an abnormal background activity and an aberrant responsiveness to stimuli of the cut and regenerating nerve endings33,34,45 (Fig 2B).


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Thus, experimental evidence demonstrates that nerves of operated corneas are not silent?they exhibit an abnormal ongoing activity and an altered responsiveness to stimuli.


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If this interpretation of the origin of postoperative ocular dryness sensation is confirmed, the therapeutic strategies for patients suffering this problem after photorefractive surgery need to be revised and should perhaps be directed not only to replace tear fluid but also to attenuate the abnormal impulse discharges of the damaged nerves of the cornea.


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Therefore, the use of ion channel antagonists that block the enhanced excitability of injured and regenerating nerve fibers, attenuating their neural input, appear to be a promising strategy to complement the treatment of dry eye sensations and other dysesthesias experienced by photorefractive surgery patients.

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Broken Eyes

"The price good men pay for indifference to public affairs is to be ruled by evil men." Plato


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 Post subject: Re: Impaired Tear Secretion or ?Phantom? Cornea?
PostPosted: Sun Aug 19, 2007 3:47 am 
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Broken Eyes wrote:
Eye Dryness Sensations After Refractive Surgery: Impaired Tear Secretion or ?Phantom? Cornea?

Journal of Refractive Surgery Vol. 23 No. 6 June 2007
Carlos Belmonte, MD, PhD

From the full text:

Quote:
Moreover, the spontaneous sensations of eye dryness, soreness to touch, and other dysesthesias seen in LASIK patients postoperatively may not be primarily due to real surface dryness consecutive to a reduced sensory input after denervation, but rather to an abnormal background activity and an aberrant responsiveness to stimuli of the cut and regenerating nerve endings33,34,45 (Fig 2B).


Quote:
If this interpretation of the origin of postoperative ocular dryness sensation is confirmed, the therapeutic strategies for patients suffering this problem after photorefractive surgery need to be revised and should perhaps be directed not only to replace tear fluid but also to attenuate the abnormal impulse discharges of the damaged nerves of the cornea.

[/quote]

This is an excellent article that helps explain that post-LASIK dry eye pain is not always solely due to dry eyes. Unlike non-LASIK dry eyes, LASIK dry eyes are caused by the cutting of corneal nerves. If these nerves grow back abnormally and thereby respond to stimuli abnormallly, you end up with eye pain that your LASIK MD will attribute to "classic" dry eye when he/she knows (assuming he/she reads LASIK research literature) that it is likely due to nerve damage as noted in the article posted above.

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 Post subject:
PostPosted: Sun Aug 26, 2007 7:57 am 
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Joined: Sat May 12, 2007 9:18 pm
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Location: Studio City, CA
Phantom pain?! I mentioned this in a previous post reply.
Somebody toss me a biscuit! :D
I wonder if any neurologists anywhere can shed light or insight on corneal nerve damage.


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