Tear film lipid layer interferometry grading patterns. From Yokoi et al., Correlation of tear lipid layer interference patterns with the diagnosis and severity of dry eye. Am J Ophthalmol. 1996; 122: 818–24 [35]. A = Grade 1 (gray uniform), B = Grade 2 (gray non-uniform), C = Grade 3 (few colors non-uniform), D = Grade 4 (many colors non-uniform), E = Grade 5 (partly exposed corneal surface).