We read with great interest the article by Vehof and associates demonstrating the clinical characteristics of dry eye patients with chronic pain syndromes. The authors reported that chronic pain syndromes are associated with increased severity of dry eye symptoms. Nevertheless, the objective tests (ie, tear osmolarity test, tear breakup time, Schirmer test) showed similar results in dry eye patients with and without a chronic pain syndrome. As the authors pointed out, awareness of chronic pain syndromes might provide an insight into understanding the discordance between signs and symptoms of dry eye disease.
The study by Vehof and associates might be improved by adding some other objective dry eye tests. Tear meniscus height and tear film thickness measurements with Fourier-domain optical coherence tomography might be beneficial for better evaluation of dry eye patients. Since diurnal variations may affect tear function tests, it is important to mention about the time that the examinations were performed. When conducting researches related to dry eye tests, it would be better to describe and eliminate some confounding factors such as contact lens wear, pre-existing ocular surface disorders (ie, pinguecula, pterygium), history of cataract or refractive surgery operations, and type and frequency of ocular medications that were used by the patients.
Most of the patients who were included in the study by Vehof and associates had Sjögren disease. In our opinion, it is necessary to report the type of Sjögren disease: primary or secondary. Since secondary Sjögren syndrome is comorbidity of eye/mouth dryness and several systemic diseases (rheumatoid arthritis, systemic lupus erythematosus, scleroderma, etc), the outcomes of ocular examinations could be altered by those additional diseases. In addition, dry eye disease was found to be more common in people with type 2 diabetes. Since dry eye tests, corneal sensation, and thus ocular pain might be affected by diabetes mellitus, diabetic patients should be excluded from this type of study. Finally, systemic medications used in Sjögren syndrome such as hydroxychloroquine might affect visual acuity and thus Snellen scores that were also used in the analysis of the present study.