Eyeworld

EW CORNEA 90 March 2015 by Ellen Stodola EyeWorld Staff Writer Corneal pain without stain Patients with corneal pain who have little to no signs can be frustrated by a problem that is often challenging to treat C orneal pain can be a real problem for patients, but it can be even worse when there are little or no signs. "Pain without stain" was the topic that Stephen Pflugfelder, MD, Baylor College of Medicine, Houston, focused on at the 2014 American Academy of Ophthalmol- ogy (AAO) meeting last October. "This is defined as symptomatic patients with minimal or no signs," he said. The symptoms may be typical of dry eye, such as burning, foreign body sensitivity, photopho- bia, and exquisite sensitivity to dry, drafty environments. These patients also have minimal or no relief from conventional dry eye treatments. Rapid tear break-up time (TBUT) is often the only objective sign in these cases. Chronic pain symptoms may lead to central sensitization. Keratoneuralgia One characteristic feature of "pain without stain" is that there is disconnect between signs and symptoms that may be dismissed or considered as hysterical or psycho- somatic. "Patients are often depressed and feel less productive," Dr. Pflugfelder said. Pain without stain suggests neuropathic pain, also termed keratoneuralgia, he said. "The cornea is very vulnerable to developing neuropathic pain," he said. It is the most exposed mucosal tissue in the body and is susceptible to environmental and surgical stress and trauma. The term "keratoneuralgia" was initially coined by Perry Rosenthal, MD, Dr. Pflugfelder said, and is an appropriately descriptive term. This issue can also be referred to as corne- al neuralgia or neuralgia pain. With keratoneuralgia, the nerve endings in the cornea become more sensitive to normal environmental stimuli, and increased sensitivity may be due to inflammatory media- tors. The diagnosis of keratoneural- gia is primarily clinical or by abnor- mal nerve by confocal microscopy. Treatment There are a number of steps to treat this condition, including shielding the cornea from the environment, using autologous plasma or serum drops, gabapentin or pregabalin, tricyclic antidepressants, counseling to improve coping with the pain, or referring to a colleague. "Unfortunately the outcome is often poor no matter what you do," he said. Dr. Pflugfelder discussed the topic after the AAO meeting, speak- ing about the number of patients with this problem and how he han- dles these cases. "It's not that common," he said. "But most cornea specialists I know see 1 or 2 patients a month with this problem." It may be easiest to identify the problem in patients who have a history of LASIK who come in complaining of symptoms similar to those of dry eye or saying they are sensitive to air drafts. Additionally, patients may be suffering from "pain without stain" or keratoneuralgia if they do not have any other objective findings. Dr. Pflugfelder said that many of the patients he sees for this come to him having already been treated with a number of medications but little to no improvement. "It's usually a diagnosis of exclusion," he said. Often rapid TBUT is the only sign, or perhaps there is a mild amount of fluorescein staining. Dr. Pflugfelder has not found any treatment that consistently works for these patients, and it often has to be trial and error to attempt to alleviate the pain. "In at least 50% of the cases, I still haven't adequately addressed their symptoms," he said. Sometimes patients suffering from keratoneuralgia can have other ocular problems as well, like a histo- ry of shingles or herpes zoster. They might have some other manifesta- tions of zoster in the eye like corneal opacities, but most often they do not have much. "Doctors should have an aware- ness of [keratoneuralgia]," he said. "Unfortunately, it's turned out to be a rare but serious side effect of LASIK." The issue is a particular prob- lem because it can affect productive people whose quality of life is being diminished. The pain can sometimes be so intense that people may want to commit suicide. Usually their vision is fine, but they have eye pain they are unable to deal with. It is analogous to other conditions where objective tests show minimal prob- lems, but the patient is experiencing severe pain, he said. EW Editors' note: Dr. Pflugfelder has financial interests with GlaxoSmithKline (Brentford, U.K.), Bausch + Lomb (Bridgewater, N.J.), and Allergan (Irvine, Calif.). Contact information Pflugfelder: stevenp@bcm.edu E very so often, ophthalmologists are faced with cases where they have limited treatment options. This can be extremely frustrating. It is even more difficult when the diagnosis is challenging. Imagine a patient who has severe dry eye complaints but minimal signs on slit lamp examination, i.e., "pain without stain." The patient may have a history of LASIK surgery or herpes zoster, but not neces- sarily. This month's "Cornea editor's corner of the world" explores the condition of keratoneuralgia. Stephen Pflugfelder, MD, discusses details of the diagnosis and man- agement of this challenging condition. Clara C. Chan, MD, FRCSC, FACS, cornea editor Cornea editor's corner of the world

• Cover