OPHTHALMOLOGY
Dry Eye Disease The “That Condition” of Eye Care BY GARY S. SCHWARTZ, MD, MA, AND JACOB R. LANG, OD, FAAO
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ne, thing that most medical specialties have in common with one another is they each have their version of That Condition (TC). Regardless of what type of doctor you are, you know what we are talking about. TC is that niggling condition that patients and doctors usually define by symptoms, rather than by disease entity. The symptoms can be chronic or acute, constant or intermittent, stable or progressive, and although they are usually neither life- nor sight-threatening, they are often significant enough to affect patients’ daily activities and quality of life. TC is usually multifactorial with many internal and external influences. It is difficult to both diagnose accurately and treat completely, and for these reasons, patients tend to hop from doctor to doctor in search of a cure. Almost every medical specialty will have their version of TC. For gastroenterologists, it is belly pain; for neurologists, it is headache; for dermatologists, it is itchiness; for gerontologists, it is dizziness; for many specialties, it is low back pain. In eye care, it is dry eye. As seen with other specialties’ versions of TC, dry eye is chronic, multifactorial, difficult to both diagnose properly, treat fully, and typically not life-threatening.
When we were in training twenty years ago (for JRL) and more (for GSS), research on Dry Eye Disease (DED) was scant. There were very few in-office tests at that time, and of those that were available, few were accurate, reproducible or frankly useful. Treatments were limited to over-the-counter lubricating eye drops, punctal occlusion, eye masks, room humidifiers and the advice to spend winter in a more humid area than Minnesota. Tropical areas, such as Hawaii and Florida, were recommended; the deserts and mountains of the American West were to be avoided. Despite our best efforts, the majority of patients did not see real improvement, and most continued to doctor-shop, hoping to find someone who could understand their problem enough to heal them. Out of all this demand was born the DED specialty. Although the optometry schools and medical school departments of ophthalmology have had important roles in the development of this specialty, for-profit therapeutics and device companies have taken the lead in much of the progress. And they are smart to lead this effort because DED affects an estimated 30 million Americans. It is also one of those chronic conditions that that gets worse with age. As the population ages, more people suffer from DED, with each individual suffering more with each passing year. Here is a brief look at the developments in diagnosis and therapy over the last 25 years.
Diagnosis The first step in curing patients of a condition is gaining an understanding of it. For DED, this means understanding what normal tears look like and how they differ from abnormal ones. DED is typically caused by more than just a decrease in the volume of tears, and so the name of the specialty is an unfortunate misnomer. Tear Film Dysfunction would be a better name, but DED is easier to market and for patients to grasp; it is therefore here to stay. In keeping with the early misunderstanding that all DED was caused by the eyes’ failure to make enough tears, most of the available tests from 20-30 years ago merely measured the volume of tears that a patient produced. The following analogy points out the problem with this system: managing a patient’s tear film problem by measuring only their tear volume is akin to managing a patient’s blood dyscrasia by measuring only their hematocrit. We eventually realized that tear volume was not always consistent with patients’ symptoms or examination findings. For example, many DED patients complain of watery eyes. Once we knew there had to be something else at play, it was only a matter of time before we figured out what that was. If the problem cannot always be attributed to the quantity of tears, it must often be attributed to their quality. Researchers looked at what constituted normal tears and discovered a rich combination of water, salts, organic molecules, e.g., hormones and enzymes, mucin, lipid, cells, e.g., inflammatory, bacteria, and other materials. They then looked at the tears from patients who were diagnosed with DED and found that different patients had abnormal amounts of any or all of what is normally found. Based on these observations, different tests have been marketed in an effort to identify the source of any patient’s problem.
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FENRUARY 2022 MINNESOTA PHYSICIAN
