# Advances in the Noninvasive Diagnosis of Dry Eye Disease
## 12 Pros and Cons of Noninvasive DED Imaging  
The novel non-invasive diagnostic techniques for DED offer numerous advantages over conventional tests. The main advantage is related to their automated nature, which means that they do not require the clinician's judgment to determine a score. This is clinically relevant as subjective DED markers, such as fluorescein BUT and corneal staining, feature low inter-observer repeatability due to their lack of standardization [4]. Moreover, most of these novel diagnostic techniques do not require direct contact with the eye, and therefore have little/no effect on the volume and properties of the tear film. Thus, they can be used as screening tools (e.g., prior to ocular surgery) by trained medical personnel (not necessarily an ophthalmologist), before proceeding with more invasive ocular surface examinations in case of the detection of abnormal values. Furthermore, they provide clear and detailed reports summarizing all the results of the tests for each patient examination, which can be used for future reference and comparison (Figures 1 and 2).  
The daily report is useful for educating patients and encouraging treatment compliance: \"A picture is truly worth a thousand words\". All-in-one devices (one machine for more tasks) make it possible to reach the diagnosis of DED in less time compared to a traditional workup (e.g., 3 min are enough to perform a complete ocular surface workup with Idra), and represent a guide for imaging-based treatment: the deficient layer(s) of the tear film is/are identified and a targeted therapy can be prescribed. Similarly, monitoring patient's course over time is also made easier by using these devices and the trend of a single parameter (e.g., NIBUT) after a given therapy can be graphically reported and analyzed (Figure 3).  
Figure 1: Dry eye report obtained with the use of Keratograph 5 M (Oculus Optikgeräte GmbH, Wetzlar, Germany). A combination of five parameters, including tear meniscus height, non-invasive break-up time, redness, meibography, and conjunctival chassis, is displayed on a radar chart in a pentagonal shape.  
Figure 3: Trending graph obtained with the use of IDRA (Sbm Sistemi, Inc., Torino, Italy) related to noninvasive break-up time values collected at different time points.  
Figure 2: Dry Eye report obtained with the use of IDRA (Sbm Sistemi, Inc., Torino, Italy), including noninvasive break-up time, eye blink, lipid layer, tear meniscus height, and loss area of meibomian glands.  
Finally, we would like to provide some recommendations for the improved use of noninvasive diagnostic tools. Firstly, as in traditional DED tests, in the noninvasive workup attention should be paid to the order in which diagnostic exams are performed. In fact, although these tests usually do not require contact with the ocular surface, light-induced tearing should be considered, since it could influence the results of subsequent examinations. Secondly, in the case of significant differences between the two eyes of the same patient, results should be interpreted with caution, and multiple evaluations of both eyes are advisable.