Dry eye or Keratoconjunctivitis sicca (KCS) is the name that describes several clinical diseases in Ophthalmology; all of them altering the preocular tear film, which causes a disease of the ocular surface whereby tear volume, tear composition and other hydrodynamic factors are altered.
Dry eye symptoms
Dry eye is a disease that does not go unnoticed by the patient. The symptoms are usually clear and unpleasantly frequent:
- Sensation of “grit in the eyes”.
- Dry eyes
- Intolerance to contact lenses due to the same dryness.
- Fluctuations in vision that last until one or more blinks restore a tear film that is optimally suitable for vision.
- Epiphora, i.e., abundant and constant lacrimation
- Burning eyes
- Itching, tingling or irritation of the skin around the eyes
- Photophobia
The presentation of these symptoms is highly variable. Precisely one of the characteristics of dry eye is the diurnal and nocturnal differences in the incidence of its symptoms. For example, aqueous secretion decreases greatly in the evening and is minimized during nighttime sleep, which, together with the hypoxia common during this period with the eyes closed, is accompanied by a significant increase in symptoms upon awakening.
Diagnosis of dry eye
The correct diagnosis of the pathology is what can best lead us to the most appropriate treatment. There are several study methods and objective diagnostic tests that are used clinically to measure the integrity and stability of the preocular tear film. However, there is currently no single test that can diagnose all types of dry eye. What is needed is to have a diagnosis that provides knowledge of the degree of severity, the subsystem affected and the origin in order to develop a more specific treatment accordingly.
The diagnostic tests currently available in ophthalmology are as follows:
Anamnesis
The anamnesis is a verbal examination, in which the ophthalmologist must listen to the patient’s description of his disease, and simultaneously help him to remember the situations and symptoms that he spontaneously does not mention, because he does not relate them to his disease. It is necessary to know the symptoms, when they started, how they evolved, how they have been treated and in which situations they improve and worsen.
Also of great interest are the family history and above all the personal history, the patient’s habits and place of work and housing, without forgetting the treatments taken for other reasons, since some or several of them may be the cause of dry eye or exacerbate it.
Exploratory findings
Within the semiology of dry eye we can distinguish between biomicroscopic findings or those detected with the slit lamp and those observed with the naked eye, such as the following:
- Lack of brightness in the eyes and sad looking gaze.
- Repetitive eye rubbing or the need to touch the eyes frequently.
- Increased blinking frequency and in some cases blepharospasm.
- Conjunctival keratic and perikeratotic congestion.
- Inflammation of the palpebral edges, sensation of excess tearing of the palpebral edges, etc.
And, after observing the ocular surface and the skin surrounding the eyes, other aspects should also be observed, such as: the skin of the face for acne rosacea, seborrheic dermatitis, etc.; palpate the parotid, submaxillary and submandibular glands; examine the mouth for the amount of saliva; look at the hands for signs of joint inflammation; petechial eruptions and eczema, etc.
Tests for quantitative and qualitative tear analysis
Schirmer’s test: This test was devised by Schirmer in 1903 and consists of placing a strip of filter paper in the eye socket. The patient should remain blinking normally for 5 minutes, seated in the examination cabinet, in which there should be neither strong lights nor air currents. After 5 minutes the strip is removed and the linear millimeters moistened on the part of the strip not inserted behind the eyelid are noted. Thus, a value higher than 15 mm is considered normal, and a result lower than 5.5 mm is considered diagnostic of aqueous tear deficiency.
Jones basal secretion test: Later, in 1966, Jones proposed to perform the test after applying anesthetic, in order to quantify the “basal” tear production, as opposed to the “reflex” production that would be measured by the Schirmer I test. In this case a figure of less than 10 mm is considered pathological.
Lacrimal clearance test: Despite the limitations in its performance, it should be noted that this test has a higher correlation than the Schirmer test with symptoms of ocular irritation and is more frequent with older age, meibomian disease and decreased corneal-conjunctival sensitivity.
Other tests or laboratory tests: There are tests that require more sophistication for its realization and that would be in this section:
- Osmolarity study
- Proteinogram (by electrophoresis)
- Tear film aqueous layer crystallization tests
Film stability analysis
Tear breakup time: This test is performed by applying a drop of fluorescein to the eye and quantifying the appearance of a black spot after the last blink. Often the test will need to be repeated more than once, to avoid environmental factors such as heat or drafts. It is considered normal for the dye to remain on the eye for 10 to 15 seconds, and if it gives a lower value, it is indicative of poor tear quality, but does not differentiate the clinical type of dry eye.
Fluorescein in one eye during tear tear tear breakup analysis.
Ocular surface analysis
Fluorescein staining: instillation of 1-2% fluorescein or by means of paper strips allows the ophthalmologist to observe in a few seconds the corneal areas where there is an absence of epithelium. Fluorescein also allows a better visualization of the size of the lacrimal meniscus and mucous filaments. Cobalt blue light is required for visualization.
Rose Bengal: Rose Bengal has the ability to stain devitalized and keratinizing cells and those not covered by mucin. Staining is evaluated without blue light, mucin secretion and filaments are also stained by pink bengal. Therefore, the use of fluorescein and pink allows to objectify epithelial damage and the state of the mucin layer. This dye causes intense stinging, even more marked in dry eyes.
Classification according to degree of lesion or staining with rose bengal
Lissamine green: to reduce the intense stinging caused by pink bengal, 1% lissamine green has been proposed, with similar properties but with better tolerance and lower toxicity.
Histological tests
Impression cytology: of all the histological tests, impression cytology is the most widely used due to its simplicity, minimal aggressiveness, possibility of anatomical localization and the abundant information it can provide. It consists of obtaining superficial layers of the epithelium by applying a filter paper to various areas of the eye and studying them.
Other less frequently used tests are conjunctival biopsy, which provides good information on the disease at the cellular level. Lip and salivary gland biopsy may be necessary to confirm the diagnosis of Sjögren’s syndrome, although this is not routinely indicated.
Hematologic tests for dry eye
Its main interest is in patients with Sjögren’s syndrome, which is an autoimmune disease that affects the exocrine glands and leads to dryness. Anemia, leukopenia, relative lymphocytosis, eosinophilia, eosinophilia, thrombocytosis, thrombocytopenia, increased erythrocyte sedimentation rate or hypercreatininemia among many other related pathologies can be found by these tests.
Diagnostic criteria in dry eye
Despite all the existing diagnostic tests already described, other studies claim that an analysis of symptoms alone is not sufficient for a differential diagnosis, as the same symptoms are often present in patients with different types of dry eye.
In short, and as a final conclusion, despite the existence of multiple tests and examinations (which is why there are so many and so diverse), for the diagnosis of dry eye, the most efficient, important and really effective way is to perform a good anamnesis and examination by an experienced ophthalmologist, in the doctor’s office.