Diagnosis of dry eye

We are changing our point of view on how to approach the dry eye, from diagnostic tests to therapeutic strategies. Up to now, the analysis of the tear, its quantity and quality, was performed in a very mechanical way and very little practice. Tests were performed with a high rate of error, as Schirmmer test, strips of paper that attempt to measure the amount of tears generated in the lachrymal gland, a complex, tedious and largely ineffective test, (performed in the same way that proposed Otto Schirmmer in 1903).

We currently propose to evaluate the anatomical structures of the ocular surface as well as the eyelids and then study the tear and the tear film, not in a static but a dynamic way. We are interested in the balance between the tear that is generated in the lachrymal glands and the dynamics of evacuation by the tear ducts. The dynamics of the tear film formation in each blink is also important. Tear film stay a few seconds humidifying the eye and preventing it to blink constantly.

Let’s look in more detail how we can analyze the main factors for dry eye diagnosis and subsequent treatment:

Main factors for the diagnosis of dry eye

  •  Subjective discomfort, what “feels” the patient
  • Palpebral dynamics
  • Meibografy
  • State of the eyelid margin
  • Tear film dynamics
  • Corneal-conjunctival epithelium
  • Tear osmolarity
  • Level of the eye surface inflammation

1.- Subjective discomfort, what does the patient “feel”:

From a practical standpoint, in a patient with dry eye, we want to know the symptoms they have and how it affects their daily lives. There are different tests that establish what kind of discomfort is more relevant in each case through a series of questions. One of the most popular is the OSDI test which, in our experience, has helped us to classify more patients with dry eyes, so we can understand better what our patients feel and look for the best way to relieve their discomfort.

Remember that dry eye is one of the most disabling processes. Patients suffer great anxiety because they cannot perform their daily activities and see a great misunderstanding in the people around them so know the symptoms and try to relieve them as soon as possible is one of the most important aspects that we currently give to the treatment of dry eye.

2.- Palpebral Dynamics:

We want to know if the blink is correct, both in frequency and quality, if it is complete or not and if it sets a good tear film. For such studies, we have devices that can record blinking with high frequency video and allow us to analyze it perfectly.

3 – Meibography.:

Perhaps the most novel aspect in the diagnosis of dry eye is the study of the meibomian glands. We have already said that they have a key role in its genesis. In most cases these glands are affected, there is less production and secretion of lipids on tears and these patients have a more quickly evaporation of the tear film, leaving the ocular surface exposed to direct contact with air. By using a test known as meibography, these glands can be visualized and we can observe their functional status, if the inflammation or an atrophic process has already started. This information is essential to determine the appropriate treatment for each patient.

MEIBOGRAFIA

Figure 2 –. (A) Performing infrared Meibography. (B) Meibomian glands of the upper eyelid and lower eyelid (white vertical bands). (C) Normal appearance of the meibomian glands and (D) Patient with a significant decrease in the number of meibomian glands and their quality, showing loss of their rectilinear aspect toward a sinuous aspect.

 

4 – State of the eyelids margin:

This is one of the key points; we know that in most cases of dry eye there are changes in the lining of the eyelids, which lies in between the area of the eyelashes and the conjunctiva that lines the eyelids inside, called eyelid margin, where the orifices of the meibomian glands are. In the case of dry eye a change of this mucosa occurs, as if the skin out over the eyelid was advancing inward (metaplasia epidermizating), leading to plug the orifices of the meibomian glands. It is essential to note this fact to solve it, as we shall see with more detail in the section on treatment.

glándulas de meibomio

Figure 3 – (A) Normal appearance of the eyelid margin with capping output meibomian gland orifices (black arrows) (B) Eyelid margin with more vascularization and occlusion of meibomian glands orifice (blue arrows) (C) Hyperkeratinisation on the eyelid marign (blue arrows) (D) Eyelid margin hyperkeratinization with capping and disappearance of meibomian glands orifices.

 

5.- Tear film.

The study of tear film is essential and must be analyzed dynamically. We want to know the constitution, stability and how it breaks. Up to now, we have used little ineffective methods, stained with dyes such as fluorescein, to measure the break up time of the tear film (BUT). It was valued, but we realised that stains induce changes that alter the results and do not help the diagnosis.

We currently have methods that allow us to sign up, by videography, the tear film, the dynamics of the particles in it, its evolution over time and how to break it, always without dyes or other substances that might alter the results.

Another key aspect of the tear film is to know its structure, the layers that constitute it, especially the outer lipid layer, essential to control evaporation and break the tear film. Currently we have a technology that informs us of this lipid layer, how it is maintained and how to break of the tear film.

Keratograf-meibografo

Figure 4 –. Study of the tear film by Keratograf ®. (A) Study of the tear film break up time without colorants, (B) Determination of the river and tear meniscus height. (C) Analysis of the lipid layer.

 

6 – State of the corneal-conjunctival epithelium:

The consequences of the direct action of the air on the ocular surface and inflammation at this level produce tissues damage, so it is important to study their implications in each case. Generally, we use vital dyes (lissamine green), which show the altered cells as well as those areas that have already disappeared and left exposed the sensory nerve endings, responsible for the discomfort of grittiness and burning felt by patients with dry eye.

Cytological studies are recommended in severe cases, analyzing cells of the ocular surface obtained by scraping or applying nitrocellulose filter paper on the ocular surface to remove the superficial 2-3 layers of cells (Impression cytology), allowing us to see microscopic changes that take place inside the cells.

Tinción-con-Rosa-de-Bengala

Figure 5 .- (A) Staining with Rose Bengal showing the conjunctival and corneal epithelium damaged (arrows), (B) Staining of the cornea with lissamine green, white light with blue light. (C) Impression cytology showing the epithelial cells of the conjunctiva and (D) impression cytology with PAS showing conjunctival goblet cells

7 .- Tear Osmolarity:

The osmolarity of the tear is one of the most important factors that has been given recently because more than 90% of the cases is high, since it is a common factor in all cases of dry eye and guides us on the level of gravity and the evolution of patients, and how they are responding to the treatment.

Analysis of tear osmolarity has become popular with the advent of new measurement systems, very accurate and easy to use (TearLab ®).

osmolaridad

Figure 6 .- Tear osmolarity detection with TearLab ® system.

 

8 .- Level of inflammation on the ocular surface.

It is one of the most important new factors that have been recently taken. I personally think that it is a revolution to focus on the inflammation to define the treatment of patients with dry eye. Inflammation is present in both cases of dry eye, primary or associated with other diseases, such as rheumatism, Sjögren or autoimmune disorders, as well as in cases of hormonal changes associated with menopause. In all cases, an inflammatory reaction occurs in the ocular surface exacerbating the deterioration of tissues and is responsible for the discomfort that patients notice.

Until recently, not much importance was given to the inflammatory process in dry eye but now we have seen that its presence is fundamental in the evolution of the disease, it is essential to measure and adjust the treatment to reduce it. Fortunately, we have a simple and very effective test to detect inflammatory mediators in the tear, called metalloproteinase 9 (MMP-9), the RPS InflammaDry Detector ®, a point-of-care test.

ojo-seco-InflammaDry

Figure 7 .- Study of ocular surface inflammation by detecting inflammatory mediators (MMP-9) in the tear film: RPS InflammaDry Detector ®.