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Time best remedy for LASIK-induced neurotrophic epitheliopathy
The condition, which affects 2% to 4% of all LASIK patients, usually resolves within 6 months.
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SEATTLE — For patients affected with LASIK-induced neurotrophic epitheliopathy (LNE), the best cure is patience.
“The solution is time,” said Steven E. Wilson, MD. “You can’t predict who these patients are ahead of time, which would be nice.”
In a clinical study, Dr. Wilson found that rose bengal staining in post-LASIK patients without previous dry eye is likely due to LNE, because there was no difference in mean tear production between patients with epithelial erosions and those without.
“What we found was there was no difference in tear production with a Schirmer’s test without anesthesia, indicating there was no difference in tear production between these patients, so therefore that was not the cause of the condition,” he said.
LNE causes
In every refractive surgery practice, Dr. Wilson said, between 1% and 4% of a patients undergoing LASIK will have a condition in which the eyes feel dry, with punctate staining on the corneal surface. This staining is usually relegated to the area of the LASIK flap.
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“This condition will remain for typically up to 6 months in a significant proportion of these patients. If it’s just on the edge of the flap, they may notice a little dryness and that’s it, but if it’s in the center of the flap, it does affect the vision for the length of time it takes to resolve,” Dr. Wilson said.
Since tear production in these patients was completely normal during these 6 months, Dr. Wilson had to look elsewhere for the answer to the problem.
“Based on my knowledge of corneal physiology in other patients, for example, patients that get a trigeminal nerve defect that causes corneal anesthesia, such as from trauma or surgery or other causes, they will often get an epitheliopathy showing that the epithelium of the cornea really needs the input from the nerves that are transected during LASIK.” he said. This sort of damage is similar to that in patients who had had damage of other kinds to the trigeminal nerve.
“Patients that get trigeminal nerve defects, not from LASIK but from a trauma will often have a breakdown of the epithelium and epithelial staining similar to LASIK patients. I think this situation is a milder form of that. I think it affects basically every patient, and that’s why some patients have a sensation of dryness even if they do not have staining on the cornea,” he said.
Other studies have shown that the nerves regenerate in about 6 months after LASIK, the same amount of time it takes for LNE to resolve in most cases.
“So that’s what we think most of these patients are,” Dr. Wilson said. “It’s important to point out that none of the patients in this study had dry eye prior to surgery. They were all totally normal patients, and that was a selection criterion for this study. If a patient does have existing dry eye prior to LASIK, they are much more likely to get this condition, and it’s more likely to be a severe condition. Again, it typically goes away at 6 months and they usually return to their baseline dry eye.”
The damage
When the stromal flap is created, the peripheral nerves are cut and the nerve trunks that carry sensation from the cornea to the limbus are cut as well.
“There are also some interesting corollaries,” Dr. Wilson said. “I think this condition is less common with small diameter flaps. It was not nearly as common for me to see this when I was using the Automated Corneal Shaper microkeratome (ACS, Bausch & Lomb), which I used for the first 2 years I was doing LASIK. So there you were dealing with not only a smaller flap, but also a nasal hinge. It may be in these situations you are more likely to spare major nerve trunks providing sensation to the central cornea. Eric Donnenfeld, MD, has shown that nasal flaps are less likely to cause ‘LASIK’ dry eye. Nowadays, we want to use a superior hinge and larger diameter flaps so we can treat hyperopia or perform hyperopic enhancement if a patient is overcorrected from initial LASIK.”
Even though other treatments are available, Dr. Wilson suggested that time was the best way to recover from LNE.
“While we should treat them like a dry eye patient, with artificial tears, ointments and punctal plugs (in some patients), these have a temporizing effect, but really don’t treat this condition which will, by 6 months, go away,” he said.
“There’s another thing you can do in some of these patients. This is for patients that have normal tear production. In patients who develop this rose bengal staining on the flap and have 8 mm or greater of wetting in 5 minutes with the Schirmer’s without anesthesia. You can put in a soft contact lens and that will give them enough smoothing that it makes their vision better. We don’t do that with all patients, but if they’re having a lot of central staining of the cornea that’s affecting their vision and they produce normal tears, then we have tried that successfully in some patients.
One other thing Dr. Wilson cautions against is doing enhancements in both eyes simultaneously.
“If you enhance them, you’re therefore lifting the flap and re-interrupting the nerves,” he said. “It’s virtually 100% that they’ll get the LNE again. In patients like that we often will stage their enhancement, do one eye, let it get to the point where their vision isn’t blurred and then do the second eye.”
For Your Information:
- Steven E. Wilson, MD, can be reached at the University of Washington, Department of Ophthalmology, Box 35685, Seattle, WA 98195, (206) 543-7250; fax: (206) 543-4414.