Sir,

We read with interest Firat and Doganay’s1 recent report on effects of dry eye on corneal biomechanics. We propose the authors missed the opportunity to review an interesting hypothesis because of inadequate study design and methodology. Whereas the report aimed to determine effects of dry eye, the disease classification and study enrolment criteria were poorly defined. We would like to bring to the authors attention the International Dry Eye Workshop report (2006) that provides a standardized classification for diagnosis and grading severity of dry eye.2 Including patients with significant ocular surface disorders may have allowed accurate conclusions. The absence of significant difference in corneal thickness probably reflects milder disease in the study group.3

Goldman applanation tonometry (GAT) is based on assumptions of the tear film and known to be affected by the central corneal thickness. The Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY, USA) is a non contact tonometer that measures the biphasic corneal response to generate a cornea compensated intraocular pressure (IOPcc). The more interventional contact GAT measurements were surprisingly recorded earlier in the sequence of measurements. Data for analysis and comparison of IOP between the two instruments or even the Goldmann-correlated IOP measurement, IOPG (average of the biphasic pressure readings generated by the ORA) vs IOPCC, are not provided. The results are duplicated in text and bar chart format, as opposed to use of a scatter plot with range of measurements and do not contribute to the discussion.

The authors’ hypothesis on effect of dry eye in IOP measurements (traditional and newer cornea compensated values) and corneal biomechanics can have important clinical implications. However, the lack of definition and severity grading of dry eye makes it difficult to draw accurate conclusions.