October 2015

 

REFRACTIVE SURGERY

 

Dryness after LASIK


by Maxine Lipner EyeWorld Senior Contributing Writer

 
 

Taking the time to ask about depression and chronic overlapping pain and working with pain specialists and mental health experts is vital to getting to the problem. Anat Galor, MD

 

For some post-LASIK patients it may be important to think about corneal nerves and their role in propagating dry eye.

Source: Anat Galor, MD

A pain imposter?

All too commonly, after undergoing LASIK patients come in complaining of what appears to be dry eye. Data from the literature suggest that from 20 to 55% of post-LASIK patients have chronic dry eye symptoms such as a burning pain, a feeling of irritation evoked by heat or cold, and sensitivity to light or wind, according to Alexandra E. Levitt, a fourth-year medical student, University of Miami. However, in some of these cases dry eye may be an erroneous description. Recent findings in the April 2015 issue of Molecular Pain indicate that there is a lot of overlap with the way patients would also describe neuropathic pain elsewhere in the body, Ms. Levitt reported.

Launching such a study was only logical, pointed out fellow investigator Anat Galor, MD, staff physician, VA Medical Center, and associate professor of clinical ophthalmology, Bascom Palmer Eye Institute, Miami. We know that when we do LASIK we sever nerves, she said. It makes sense for us to say, Lets look at other models in other fields and see what those fields have done to try to combat persistent symptoms after other surgeries. Thinking of LASIK in terms of its neurobiology of severing nerves and considering what can be done to remedy symptoms stemming from this is important, she thinks. Ms. Levitt described the study as a systematic review of this theme of LASIK being linked to other types of persistent pain. We were trying to pull from the LASIK-specific literature the neuroscience of corneal pain and persistent postoperative pain elsewhere in the body, she said, adding that the idea was to try to systematically review those fields.

This could offer valuable insights for LASIK practitioners, Dr. Galor said. In guarding against postoperative problems when surgery is done elsewhere in the body, such as for mastectomy and hysterectomy, she pointed out that there have been studies examining the use of nerve protectants such as pregabalin or gabapentin for patients just prior toand a few days aftersurgery.

Parallels to pain

Almost all of those studies showed that this regimen was able to decrease the frequency of persistent symptoms after surgery, Dr. Galor said. When we were looking at the epidemiology we found it was interesting that the chronic symptoms after other surgeries are very similar to those of LASIK. Investigators gleaned that at 6 months postoperatively, 2030% of LASIK patients have chronic symptoms, as did 1020% of mastectomy, thoracotomy, and surgical gallbladder patients. There have been so many surgeries where this model has been used, Dr. Galor said. What we wanted to do in our review was to highlight those parallels to say that maybe strategies to treat persistent symptoms in those models would also work in LASIK patients. Investigators did indeed find parallels. Ms. Levitt pointed out that there are a lot of striking similarities between persistent pain in other fields and symptoms described by postoperative LASIK patients. Akin to the sensitization that occurs with whats referred to as allodynia in neuropathic pain, such as when someone stubs a toe after breaking it, post-LASIK patients are hypersensitive to light, wind, and eye drops, she said. Likewise, neuropathic pain patients can have secondary hyperalgesia in which not only the area of initial injury is more sensitive to pain but also the tissue in the surrounding area, served by nerves in the same pathway, Ms. Levitt said. For some of these dry eye patients not only is their cornea more sensitive but also their conjunctiva and other nerves even in the distribution of some of the branches of the trigeminal nerve. Its pretty compelling evidence there are a lot of analogous processes being described. Also, there is the phenomenon of pain without stain, she said. In a lot of these patients, if youre looking at objective signs of changes in the tear film or irritation of the cornea, you wont find anything on clinical exam, she said, adding that even so patients will describe the symptoms of pain that can be quite debilitating. This is very similar to neuropathic pain elsewhere in the body, Ms. Levitt said. The fact that patients have pain and its disconnected from the pain processes at the site of the initial injuries is one indicator of neuropathic pain. There are a lot of parallels that make a compelling case for changing how practitioners conceptualize the chronic dry eye symptoms they see after refractive surgery, she said.

Clinical implications

Dr. Galor views all of this as potentially important from both a preventative and a treatment perspective. What we would like to do is study prevention using some of these agents like pregabalin and gabapentin at the time of LASIK to see if we can reduce persistent symptoms, she said. She currently has a large population of patients with neuropathic pain characteristics who can be challenging to treat. I try traditional things like artificial tears and topical cyclosporine; however, by the time they see me theyve already tried everything, she said. My go-to right now is autologous serum tears that contain, among other factors, nerve growth factor. She had great success using this in patients who have had intractable symptoms of neuropathic pain such as burning and photophobia, which have been classified as dry eye. My hypothesis is that nerve growth factor may normalize, enhance, or stabilize the function of the corneal nerves, she said. Were interested in studying that more and seeing if it is nerve function and not something else that is being helped by the autologous serum tears. Dr. Galor hopes practitioners come away from the study with the understanding that not all dry eye symptoms are caused by dryness on the ocular surface and that these can be driven by the corneal nerve pathway. Sometimes theyre being driven because the corneal nerve pathway is dysfunctional, and if we ignore this component of dry eye, were missing the whole picture, she said, adding that dry eye also tends to travel in conjunction with overlapping pain conditions such as depression and anxiety. To me dry eye is more than just the eye; its the corneal pain pathway or the corneal sensory pathway, and its also the entire patient, she said. Taking the time to ask about depression and chronic overlapping pain and working with pain specialists and mental health experts is vital to getting to the problem.

Editors note: The sources have no financial interests related to this article.

Contact information

Galor
: AGalor@med.miami.edu
Levitt: alevitt@med.miami.edu