Eyeworld

85 EW FEATURE September 2015 World Cornea Congress highlights corneal burns from chemical injuries and the like. Neuropathic pain syndrome The lens can also help with pain patients. Dr. Gire recalls a group of teachers who unknowingly were exposed to UV light radiation. "They were the first patients I saw who had this pain syndrome where when I looked at their corneas, they had no staining," she said. A lot of such patients' symp- toms are akin to what dry eye pa- tients describe but are compounded significantly. These include severe light sensitivity, sensitivity to air movement, and pain that some describe as burning and others de- fine as substantial aching. "It's very intense pain that nothing can help with," Dr. Gire said. Perry Rosenthal, MD, part time assistant professor, Harvard Medical School, and founder of the Boston Foundation for Sight and the Boston EyePain Foundation, describes these symptoms as neuropathic pain. The pain system is a critical alarm system warning of imminent or actual tissue damage, he said, whereas neu- ropathic pain is caused by disease, damage, or dysfunction of the pain alarm system itself. He suggested that there are two categories of dry eye disease. One is caused by disorders of the tear-pro- ducing (lacrimal) gland in which there is a direct relationship between the reduced production of tears, symptoms, and the surface eye dam- age it causes. On the other hand, by far the largest group of patients suffers from inappropriate dry eye symptoms that cannot be explained by a reduced supply of tears or dry eye surface damage. Although current theory explains the latter disease by excessively rapid tear evaporation, Dr. Rosenthal thinks that the underlying cause is hy- persensitivity of the dry eye alarm. In other words, the tear thickness sensors in the corneal nerve endings have become extra sensitive and send messages that the tear layer is thinner than it is. The result is false dry eye symptoms, and the medical term for this nerve disease is corneal neuropathy. Dr. Rosenthal thinks there is a smaller group that suffers from devastating eye pain without a vis- ible cause. They often describe the pain as burning, aching, sharp, dry eye-like, and they may even have intense photosensitivity. Some also describe pain located behind and around their eyes, headaches and pain in their ears, face, and jaws. "Their eyes look perfectly normal, and they're generally dismissed by the doctors because they can't find anything wrong that can explain it," Dr. Rosenthal said. He theorizes that the pain is projected from structur- al changes in the trigeminal pain system in their brains. "About one- third of the cases are triggered by LASIK and similar surgeries," he said. "But it can also occur spontaneously, especially in patients who have a fibromyalgia phenotype." The onset of what he calls oculofacial pain can be delayed for months or even years after an apparently successful outcome of LASIK surgery. Dr. Rosenthal explained that this type of centralized pain is typ- ically intense and unrelenting even as its apparent origins are normal. "The reason for this remarkable disparity is that the perceived loca- tions of the pain are an illusion. It is actually projected from pain centers in the brain," he said. After LASIK or PRK, some patients suffer from this pain indefinitely and many are suicidal. "In these patients, topical anesthetic eye drops typically fail to completely suppress symptoms, indicating that much of the pain originates in the brain, probably in the trigeminal brainstem," he said. Dr. Rosenthal speculates that the underlying brain disease is a localized encephalopathy similar to that attributed to fibromyalgia. If confirmed, treating this pain will require the development of systemic drugs that down regulate the pain pathways in the brain, he said, add- ing that future breakthroughs will hinge on recognizing that the brain is an important part of the pain sys- tem and that things can go wrong here as well as in the cornea. He also believes alerting refractive patients about this possibility should be part of the informed consent. Dry eye-like symptoms are common after LASIK and simi- lar surgeries and typically resolve within a year. When needed, scleral lenses suppress dry eye-like symp- toms because they totally block tear evaporation. For some who have a combination of these pain syn- dromes, however, the sclera may be too tender for these lenses to be tolerated. Dr. Gire pointed out that while the PROSE reservoir currently con- tains saline, different medications can be tried. Already, some have used bevacizumab for neovascu- larization. "Going forward, I think there would be different treatments that could be applied within the lens, which remains there on the eye while the patient is awake," she said. "So there would be a way to have drug delivery constantly." EW Editors' note: The sources have no financial interests related to this article. Contact information Gire: anisagire@gmail.com Rosenthal: prosenthal@bostoneyepain.org Thomas: dha.bethesda.ncr-medical.list. wrnm-pao@mail.mil EyeWorld Monthly Pulse EyeWorld Monthly Pulse is a reader survey on trends and patterns for the practicing ophthalmologist. Each month we send an online survey covering different topics so our readers can see how they compare to our survey. If you would like to join the hundreds of physicians who take a minute a month to share their views, please send us an email and we will add your name. Email carly@eyeworld.org and put EW Pulse in the subject line. Poll size: 130 In a 65-year-old female patient with a history of herpes zoster ophthalmicus who asks whether she should get the Shingles vaccine (Zostavax), what would you recommend? Avoid the vaccine Get the vaccine Get the vaccine only if she has not had any keratouveitis flares in more than 5 years Get the vaccine if she is about to have cataract surgery In a 40-year-old female patient who complains of eye pain and light sensitivity after LASIK but has a completely normal eye exam, which management option would you most likely select? Recommend dry eye and blepharitis treatments Arrange for scleral contact lens or PROSE lens fitting Refer to a neurologist or pain specialist Prescribe serum tears A 28-year-old male patient with keratoconus has become contact lens intolerant. Which treatment would you most likely recommend for him? Corneal collagen crosslinking Intrastromal ring segment with corneal collagen crosslinking Deep anterior lamellar keratoplasty Penetrating keratoplasty

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