Progress in Treating Dry Eye?
BY LEO SEMES, OD, FAAO
A recent review of publications over the past 60 years revealed that treatment for dry eye has offered little consistent relief for this common problem (Doughty and Glavin, 2009). Using rose bengal (RB) staining scores as a yardstick, this meta-analysis offered little guidance from published studies. For example, variations in scoring allowed only limited comparisons among topical treatments, which included the usual suspects of polymeric tear supplements, carbomer gels, and hyaluronic acid-based products. In fact, the authors reported that a 25-percent to 33-percent improvement of RB staining scores over a 30-day treatment was as well as could be expected.
So have we made any progress in this field?
Understanding Dry Eye
Characterization of ocular surfacing deficiencies has broadened, as has our knowledge of etiologies. For example, in this generation, we have learned the role of osmolarity and inflammatory components, which has led to novel therapies such as new polymeric formulations of tear supplements. In addition, we now invoke oral supplementation of omega-3 free fatty acids.
We have learned much about diagnosis and the descriptive specification of abnormalities of the ocular surface. Indeed, it is no longer just about the aqueous phase. Ocular surface investigations involve the complex interactions of all components of the tear film. Think about how much the role of meibomian gland function has evolved. And we have learned about the subjective rating of “dry eyes.”
Three years ago, a codification and stratification of ocular surface problems appeared (Lemp, 2007). From this, the researchers assigned four levels of severity of what they termed dysfunctional tear syndrome (DTS). Treatment recommendations were developed for each of the levels, ranging from tear supplements to topical steroids and immunomodulators to nutritional support and even to surgery in the most severe instances (Gipson, 2007).
Every clinician has a template for managing dry eye, targeted to the patient’s specific symptoms and clinical signs. And while that protocol may be effective, we should look to prospective clinical trials for general guidance. Unfortunately, except for results from the cyclosporine trial, relatively few of these are available. So clinicians are left to interpret the current literature and to look forward to upcoming and novel treatments.
Developments in Treatment
A survey of the recent progress shows a variety of options for managing ocular surface disease patients. These include laboratory reports of new polymer formulations and the incorporation of hyaluronic acid (Johnson et al, 2008; de la Fuente et al, 2008). Other polysaccharides have shown promise in clinical studies as well. Tamarind seed polysaccharide has demonstrated increased ocular surface adsorbance and retention. It may even prove superior to certain hyaluronic acid preparations (Rolando and Valente, 2007). In addition, combinations of current polymeric formulations are being blended with therapeutic ocular surface media to enhance nutrient properties with minimal viscosity and toxicity (Liu et al, 2009).
Finally, the surgical aspect of treatment for severe ocular surface problems continues to progress. Stem cell and other tissue engineering measures are showing promise for rehabilitation of the corneal and conjunctival surface (Schrader et al, 2009; Notara et al, 2010).
Progress is Being Made
The management of dry eye is complex and convoluted. Yet, improved and refined diagnostic techniques along with the ever expanding therapeutic realm makes the future brighter and virtually unlimited for treating ocular surface disease. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #176.
Dr. Semes is a professor of optometry at the UAB School of Optometry.