Lipid layer assessment
Using interferometry in lipid layer assessment investigates the stability of the lipid layer and likelihood of evaporative dry eye. Measurement involves assessment of the interference pattern produced by the inner and outer surfaces of the lipid layer in tear film.
This has been shown to differentiate between patients with normal eyes and those with dry eyes because patients with dry eyes tend to have thinner lipid layers.2 However, these systems are more expensive.
Topography and aberrometry
Topography and aberrometry become more irregular with ocular surface disease. This increases higher-order aberrations on both whole eye wavefront and corneal wavefront due to poor tear film and corneal abnormalities.
Tear break-up time
Performing tear break-up time using sodium fluorescein dye (FTBUT) has long been done but is now performed using computer imaging to time the surface images and blinking.
This test is now referred to as non-invasive tear break-up time (NIBUT). Various systems allow this measurement, and further investigations will provide a better understanding of the usefulness of NIBUT patterns in addition to time measurements.
Tear meniscus measurement
This is used to assess secretion rate and film stability. It is performed with computers using infrared or visible light as well as OCT.
Matrix metalloproteinase 9 (MMP-9) measurement
This measurement is used in office testing to indicate the presence of proteins that stimulate the immune response and is associated with ocular surface disease progression.
Significant increases in MMP-9 results were found in women patients with autoimmune diseases—especially Sjögren syndrome—and thyroid disease.
1. White R, Rodriguez J, Lane KJ, Johnston P, Angjeli E, Abelson MB. Blink patterns in normal and dry eye subjects; beyond blink rate. Invest Opthalmol Vis Sci. 2010 Apr;(51):3366.
2. Hwang HS, Kim EC, Kim MS. Novel tear interferometer made of paper for lipid layer evaluation. Cornea. 2014 Aug;33(8):826-31.
3. Messmer EM, von Lindenfels V, Garbe A, Kampik A. Matrix metalloproteinase 9 testing in dry eye disease using a commercially available point-of-care immunoassay. Ophthalmology. 2016 Nov;123(11):2300-2308.