dry eye

Plowing Through a Field of Uncertainty

The more we learn about dry eye, the more we need to understand.

Kelly Nichols, O.D., M.P.H., Ph.D.

In all the years I have been involved in dry eye research, this year seems to hold the most uncertainty—on a number of fronts. It is as though the more we learn about the condition, the further we are from a full understanding. In addition, corporate mergers, acquisitions and new companies all have altered the clinical and research landscape in ocular surface disease (OSD). Certainly, all these changes can be seen as opportunities for professional growth.

Pioneers blaze the trail

When we look at advances in the management of dry eye, we find that early on a few pioneers charted the course. Their big ideas, sweeping statements and hypotheses have been left out there for future scientists to prove or disprove. The advances seem monumental. Yet as future advances are made, these ideas seem smaller in context—that is, a chipping away at the problem, so to speak. That does not mean that these advances are not significant, and often it takes more careful thought and really a paradigm-shifting notion, however small, to really impact our understanding.

Take, for example, the tear film. Once thought to be 7µm in thickness and three layers thick (mucin, aqueous and lipid), it is now generally accepted the tear film is 3µm-to-4µm thick, and there are two layers: a mucin-aqueous gradient “gel” and a lipid layer. Taken at face value, the comparative differences do not seem that dramatic.

What changed is our ability to accurately measure tear film thickness with interferometric techniques, which have been confirmed with anterior segment OCT. In addition, we now have a better understanding of mucins—MUC 16 is not a membrane-bound mucin and thus, is mobile and capable of forming a gradient in the aqueous.

So, what role does the mucin really play in the health and disease of the ocular surface? We still do not fully understand, but incremental yet logical steps forward in our knowledge of mucin biology will ultimately provide that answer.

Competing interest vs. symbiosis

In today's world, science is not the only driver in the process. Marketing plays a significant role in clinical care. Some would argue for the better, others the opposite. Regardless, we are in a different place than we were 15 years ago. Direct-to-consumer marketing, the Internet and education by industry representatives all result in increased awareness of disease states by both patients and clinicians.

What is to be believed? Besides marketing claims, we are influenced by supportive science for therapeutics, clinician practice patterns, education and our peers. Our colleagues help us to decipher the science so that we can revise what we know, rather than change the paradigm completely.

Chip, chip, away

Are we at the point at which we are chipping away? Consider that early discussions of conditions with the terminology blepharitis, meibomian gland disease or dysfunction (MGD), keratoconjunctivitis sicca, meibomitis, and meibomian keratoconjunctivitis, among others, led to the concept of dry eye disease and no less than 10 different classification schemes for some component of dry eye or blepharitis through the years. This terminology became accepted as “ocular surface disease” (OSD), a family of conditions impacting the front of the eye and associated adnexa. Our profession has widely adopted the diagnosis and management of OSD, and the field continues to move forward.

The re-boot

But sometimes I wonder: Don't we just need a re-boot to start the thinking all over? Take, for example, another condition: A 64-year-old female in above-average health, post-menopause, average height and weight. She probably uses a bit too much salt, doesn't exercise enough and enjoys a glass of wine in the evening. At her annual physical (really a biennial event), her blood pressure is measured, and the value is significantly out of the normal range. As simple as that (well almost), she is diagnosed with high blood pressure. After careful review of her family and personal history, she may be prescribed a drug to treat hypertension. Straightforward, right?

The problem in applying the same analogy to dry eye disease is that we have no single accepted diagnostic test, and the tests we do use correlate poorly with symptoms. Would it be easier if we had one test? From the doctor standpoint, yes. From the patient standpoint—the same patient who views the television and Internet as viable sources of medical information—yes. So, what can we do to simplify, rather than complicate, dry eye? Here are my suggestions:

1. Ask about symptoms. Have the patient describe in his/her own words how his/her eyes feel, when they feel the worst and how it is impacting his/her life. Record this information, and refer to it at follow-up visits. Note current treatments, including frequency of application.
2. Look at the lids. Twenty years ago, we looked at the lids, but at some point, we stopped. So start—express the meibomian glands. If you see a blocked gland on slit-lamp evaluation in symptomatic patients with quiet lids, you will be surprised by what you find. Be patient—press, move laterally, press, move back, re-press. Look at the quality of the secretions, and record your description.
3. Stain. Most practitioners use fluorescein to assess tear break-up and staining of the cornea. Wait at least one minute before fully evaluating corneal staining. Believe me, you will see more. Then, use lissamine green, and again, wait a minute or two before you observe the ocular surface. This dye takes time to color mucin and devitalized cells. A band-like pattern across the inferior third of the cornea usually means either incomplete blink or possible MGD. A new product, Fluramene (Noble Vision Group), can do the job of both staining agents with one drop.
4. Follow up. This takes valuable chair time, but is worth it in the long run. Recently, there has been a lot of discussion among clinicians with dry eye clinics about the best time to follow-up on a dry eye or MGD patient. Data suggest that dry eye patients are not overly compliant with therapy—the drop-off from prescribed or non-prescribed treatments is usually four-to-six weeks. Therefore, a six-week follow-up may be the best way to keep your patient on track, and at this appointment, discuss improvements as well as changes to the treatment regimen.

It only takes a few minutes

It only takes a few minutes to order a coffee, do a refraction, add vital dye to the eye. It only takes a few minutes to listen to a patient—it is what we do best. It takes a few minutes to listen to a pharmaceutical representative in your office, a few minutes to learn something in a continuing education lecture. So why should you add additional minutes to the medical exam? The answer: Because your ability to correctly diagnose and treat ocular surface disease is not only crucial to your clinical success with each patient, but also to your ability to advance your practice financially and recruit patients.

And in the search for pharmaceuticals, I can tell you that the industry is not waiting a few minutes (or longer). They are moving forward with dry eye programs and studies to answer the needs of clinicians and patients. Even in the midst of a corporate re-boot, we are moving forward with the medical model in ocular surface disease. Does uncertainty bring clarity? We all want to know the answer to this question. Uncertainty forces decisions, and thus the journey continues. Twenty years from now, we will look back at what we did not know, and we will acknowledge the pioneers in dry eye disease. I hope optometry continues to be a big part of that effort. OM