Symptoms and signs, and signs and symptoms, oh my
Have you learned about the difference between dry eye symptoms and dry eye signs yet? Great time to learn!
Symptoms = what you experience (pain, burning, light sensitivity, blurred vision, grittiness, dry sensation, redness, etc)
Signs = what the doctor can observe during an exam (hyperosmolarity, low TBUT, ocular surface staining, etc)
These two things might match, or they might occur in different proportions (you hurt a lot worse than you look or vice versa) or you might have one without the other.
For patients, the mismatch between these two things causes all kinds of problems. Here's a few:
Communication problems with your doctor, especially if your symptoms are worse than your signs.
Difficulty sticking to a treatment plan, because we patients naturally tend to do the treatments that make us feel better and ditch the treatments that don't
Difficulty getting a grip on what actually "works", because we define success by sensation while doctors define success by improved clinical findings
The excerpt below from TFOS DEWS II tries to explain some of the situations when the sign-symptom mismatch happens. Distilling it down a bit:
You could have "dry eye pain" that's actually not from dry eye but instead neuropathic. Dry eye treatment won't fix it.
You could have symptoms off and on but not be diagnosed because you're in early stages. If you're in that bucket, you might be at higher risk of getting dry eye from medical treatments ("iatrogenic" dry eye).
You could have bad dry eye but not feel it because dry eye itself could have reduced your corneal sensitivity.
You could look like you have dry eye, but not be feeling it (yet), for all kinds of reasons.
TFOS DEWS II Definition and Classification Report
7.3 Symptoms without signs: neuropathic pain
The Pain and Sensation Subcommittee report describes a clinical scenario of neuropathic pain due to either a lesion or disease in the somatosensory system, in which ocular pain symptoms disproportionally outweigh the clinical signs . This is an important distinction in the diagnosis, and the required pain management falls outside the scope of DED therapy .
7.4 Symptoms without signs: pre-clinical dry eye state
It is further recognized that symptoms consistent with DED, but in the absence of clinical signs, especially when the symptoms are intermittent, might indicate a pre-clinical dry eye state, or a scenario of emerging episodic dry eye. Ongoing evaluation for the development of signs and the control of symptoms through education and prevention are suggested. Studies evaluating the natural history of short and long-term preventative efforts in this patient group are needed . Determination of whether such individuals are at higher risk of developing iatrogenic DED, in comparison to those who are non-symptomatic, is also deserving of further investigation .
7.5 Signs without symptoms: reduced corneal sensitivity
Patients exhibiting signs of ocular surface disease, but reporting no symptoms of discomfort, require consideration of whether dry eye management is indicated. Corneal nerve damage secondary to longstanding DED is a recognized phenomenon and the reduced corneal sensitivity can mask discomfort. The dysfunctional sensation is a function of the underlying disease process. Other forms of corneal disease exist, where corneal sensation is reduced, and these should also be managed accordingly .
7.6 Signs without symptoms: predisposition to dry eye
Ocular surface changes in the absence of presenting symptoms may be noted during a preoperative examination for cataract or refractive surgery, for example, and signify early disease that might place the patient at risk of developing symptomatic DED following the surgical event . Preventative management should be considered, as described in more detail in the Iatrogenic report . Recently, asymptomatic MGD has been reported with a prevalence of double that of symptomatic MGD in a Caucasian population . While there are limited data on the natural history of DED, symptoms do become more common with age  and individuals with MGD are more likely to report an increase in severity of their symptoms with time , all of which may support an argument for intervention.
References from this excerpt:
 Belmonte C, Nichols JJ, Cox SM, Brock JA, Begley CG, Bereiter DA, et al. TFOS DEWS II pain and sensation report. Ocul Surf 2017;15:404–437.
 Stapleton F, Alves M, Bunya VY, Jalbert I, Lekhanont K, Malet F, et al. TFOS DEWS II Epidemiology report. Ocul Surf 2017;15:334–365.
 Gomes JAP, Azar DT, Baudouin C, Efron N, Hirayama M, Horwath-Winter J, et al. TFOS DEWS II Iatrogenic report. Ocul Surf 2017;15:511–538.
 Lienert JP, Tarko L, Uchino M, Christen WG, Schaumberg DA. Long-term natural history of dry eye disease from the Patient's perspective. Ophthalmology 2016;123(2):425–433.