EyeWorld Asia-Pacific June 2014 Issue

57 EWAP DEVICES June 2014 Views from Asia-Pacific Louis TONG, MD Singapore National Eye Centre 11 Third Hospital Avenue, Singapore 168751 Tel. no. +65-98186221 louis.tong.h.t@snec.com.sg I read with interest the article “Newer dry eye diagnostic tools show promise” by Michelle Dalton. I agree with the article that newer tools like tear osmolarity and inflammatory biomarkers show promise for clinical practice. In our experience, for example, we showed that patients using chronic glaucoma medications or who have had trabeculectomy surgeries have significantly elevated tear osmolarities compared with controls, even though their tear breakup times and Schirmer’s test results were not significantly reduced 1 . Nevertheless,tear osmolarity may be a common pathway in dry eye pathology and might not be useful for distinguishing subtypes of dry eye. The article correctly mentioned the difficulty of measuring preocular tear osmolarity and the difficulty of making repeat measurements in routine clinical practice. I concur with the author that the InflammaDry MMP9 assay can be used to ascertain the presence of inflammation. Certain drugs like doxycyclines can inhibit MMPs and directly address the specific problem. Unfortunately, the dichotomous nature of the test result limits its role in routine clinical practice. Incidentally, there is another commercial assay that measures low tear lactoferrin for dry eye assessment. 2 Another tool that may become more accessible for monitoring dry eye in the future is in vivo confocal microscopy for alterations of corneal nerves. As the interviewed physicians pointed out, it does not require fanciful tools to commence treatment for symptomatic patients with dry eye. Clinical judgement is more relevant. However, in some instances I feel it would be useful for clinicians to have a biomarker assay that can monitor inflammatory markers along a linear scale, for monitoring disease progression or treatment outcome. Even though treatment modalities for dry eye are rather limited, there are now at least 12 other specific therapies being evaluated clinically for dry eye 3 . When some of these treatments eventually become routinely available, it will be more relevant to determine the subtype of dry eye using a diagnostic test. References 1. Lee SY, Wong TT, Chua J, Boo C, Soh YF, Tong L. Effect of chronic anti- glaucoma medications and trabeculectomy on tear osmolarity. Eye (Lond) . 2013 Oct;27(10):1142-50. 2. TearScan Lactoferrin Diagnostic Test Kit product information. Advanced Tear Diagnostics. N.p., n.d. Web. 28 May 2014. <http://teardiagnostics.com/wp- content/uploads/2014/02/Lf-Data-Sheet-TearScan-02282014.pdf> 3. Karpecki PM. Why Dry Eye Trials Often Fail. Review of Optometry. N.p., 15 Jan 2013. Web. 28 May 2014. <http://www.revoptom.com/content/c/38714/> Editors’ note: Dr. Tong has no financial interests related to his comments. Prashant GARG, MD Associate Director and Dr. G Chandra Sekhar Distinguished Chair of Education, LV Prasad Eye Institute LV Prasad Marg, Banjara Hills, Hyderabad 500034, India Tel. no. +91 40 30612555 Fax no. +91 40 23548271 prashant@lvpei.org D ry eye disease is a relatively common condition and with the inclusion of symptoms of discomfort and visual disturbance in its ambit many more patients are qualifying for the diagnosis of dry eye. This state poses several challenges but two that are very crucial from the clinicians’ perspective are: (1) how to distinguish functional from organic cases, and (2) how to objectively monitor the response to therapy. These questions become most challenging in milder forms of the disease with patients presenting only with symptoms but no evidence of damage to the ocular surface or tear film instability. The development of the TearLab osmolarity system and the InflammaDry test are attempts in that direction. It is hoped that these tests will provide not only objective evidence but also will quantify the change with regard to tear osmolarity and inflammatory biomarkers, the two most important changes associated with dry eye states. If there is increase in tear osmolarity or the test is positive for inflammatory markers in a patient with history suggestive of dry eye, clinicians will be sure of their diagnosis and can use this information during the course of treatment to assess the efficacy of treatment. However, the situation is not as simple as it appears here. Several questions need to be answered before these or similar tests can become part of a routine dry eye work-up: • What is the variability of test values in the normal population? What cutoff values should one use to confidently say that these values are abnormal or indicative of dry eye states? • What is the test–retest variability? This information will be crucial in deciding the value of changes noticed over time, specifically while evaluating the response to therapy. • What are other factors other than dry eye state that can alter the values of these tests? For example, diurnal variation or reduced blink while watching television or working on a computer screen can alter tear properties such as osmolarity. • Is there a linear correlation between the disease severity and degree of change in the test values? • Is there a possibility that patients with mild disease do not show alterations in these parameters? If so, should we be treating these patients? To summarize, while the development of such diagnostic tools is a welcome move it is clear we are still not there. Editors’ note: Dr. Garg has no financial interests related to his comments.