The Dry Eye Zone

Rebecca's Blog

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TFOS DEWS II: The idea that eye pain matters is relatively new to ophthalmology.

I was browsing through the beginning part of TFOS DEWS II's Pain and Sensation report on pain in dry eye disease and decided to share a couple of the introductory paragraphs. 

One of the things that dry eye patients as well as of course corneal neuropathic pain patients have a really hard time coming to grips with is how it is possible for them to experience and report symptoms that are dramatically affecting their lives, without receiving a physician response that seems appropriate and proportional to their experience. Some part of us is disturbed and disoriented by the disconnect, e.g. "Wait - if it feels this bad, something must be seriously wrong, yet they're acting like I'm fine! What does that mean? Do I have a rare condition that they are overlooking? Or am I crazy or just not coping well?"

So, in countless phone calls over the years, I've tried to explain to people things like the classic sign-symptom mismatch in dry eye, and also some possible reasons why ophthalmologists and optometrists respond the way they do (or don't) to reports of pain.

In that context, I really appreciate the history and additional insights that TFOS DEWS II's introduction sheds on this. All emphasis mine.

The use of the term ‘pain’ in eye care has been traditionally limited to a small number of pathological conditions, because conscious sensations originating at the ocular surface do not generally have a diagnostic interest.... In fact, most of the prevalent sight-threatening eye diseases, like open angle glaucoma, cataract or retinal pathologies, occur and progress without pain [2]....

In other words, traditionally, how you felt wouldn't matter because it doesn't contribute to figuring out what is wrong.

...Moderately unpleasant sensations accompany many common ocular surface diseases (allergic conjunctivitis, DED), but they have been described clinically, in most cases, with terms such as ‘dryness,’ ‘discomfort,’ and ‘itch,’ without making a direct, explicit association with pain sensations. Until a few decades ago, the term pain as a symptom of eye pathology was generally reserved for the sensations accompanying predominantly traumatic or infectious keratitis, iridocyclitis, angle closure glaucoma, and other entities [2]....

This helps explain why the word "pain" historically just doesn't compute. My iconic moment of realization about this was a small dry eye patient conference I hosted back in 2006, where we had both doctors and patients speaking. I remember the doctors being profoundly impressed with the patients' description of eye pain and what it meant to them.

Reports of pain after photorefractive surgery procedures [a/k/a LASIK, PRK, etc] and the ‘discomfort’ experienced by contact lens wearers finally directed the attention of eye care practitioners and researchers toward the origin and mechanisms of the unpleasant, and sometimes overtly painful, sensations arising from the ocular surface.

So as you can see, on top of the whole contact lens discomfort phenomenon which has been a huge deal in eyecare, the issue of post LASIK eye pain has been instrumental in drawing the eyecare professions' attention to corneal pain in general - including prompting the research that has filled the Pain and Sensation report. This ought to be at least a little gratifying to patients who have not found solutions or who have not felt that their issues were being heard.

This interest extended to ‘dryness’ sensations experienced by patients suffering from DED and by patients experiencing severe ocular surface symptoms, but with minimal or no clinical signs on slit-lamp examination.

There it is: the whole "pain without stain" phenomenon.

The underlying neurobiological mechanisms producing these sensations appear to be consistent with those mediating ocular pain in other eye pathologies, and unpleasant dry eye sensations should be considered and studied as a specific form of eye pain occurring in this particular disease.

This is huge, when you think about it. First of all, it gives us permission to re-articulate "unpleasant dry eye sensations" as PAIN. Because it really is. Second, it's saying pain in dry eye disease matters and must be studied, which is the whole premise of the report of course, but it really cannot be overstated.