Non-invasive tear breakup time | Detects the changes in corneal power or differences in brightness of placido mires, which allows non-invasive measurement of tear breakup down. |
Optical coherence tomography | Measures back-scattered and back-reflected non-visible light to quantify structural measurements on the tear meniscus parameters such tear meniscus height, area and volume. |
Meibography | Infrared system provides two-dimensional details of the silhouette of meibomian glands and allows quantification of meibomian gland dropout and detailed morphological assessment of the meibomian glands. Optical coherence tomography and in vivo confocal microscopy meibography provides detailed images of the meibomian gland acini and ducts not seen on infrared imaging. |
Interferometry | Measures the colour and fringe interference pattern produced by specular reflection at the lipid–aqueous interface of the tear film. Provides quantitative values of the lipid layer thickness which is an indicator of meibomian gland function. |
In vivo confocal microscopy | Produces a resolution comparable to histological analysis, but allows a real-time non-invasive measurement of the ocular surface at a cellular level. |
Thermography | A non-invasive technique for measuring the surface temperature of a particular region of interest on the ocular surface. |
Wavefront aberrometry | Evaluates sequential changes of visual performance related to tear film dynamics by measuring the serial higher-order aberration in the central cornea up to the sixth-order Zernike polynomial after blinking. |
Light scattering property | Forward light scattering produces a veiling luminance on the retina, reducing the retinal image contrast which the patient experiences as glare. This can be measured using a double-pass imaging technique. |