DEAL WITH DRY EYES!

DEAL WITH DRY EYES

Introduction

Dry eye syndrome (DES) is a disorder of the preocular tear film that results in damage to the ocular surface and is associated with symptoms of ocular discomfort. DES is also called keratoconjunctivitis sicca (KCS), keratitis sicca, sicca syndrome, xerophthalmia, dry eye disease (DED), ocular surface disease (OSD), or dysfunctional tear syndrome.

Dry eye disease is characterized by instability of the tear film that can be due to insufficient amount of tear production or due to poor quality of tear film, which results in increased evaporation of the tears.

ALL ABOUT TEARS

The tear film consists of three layers:

An oily layer;

A watery layer;

A layer of mucus.

Each layer has its own purpose.

The oily layer, produced by the meibomian glands, forms the outermost surface of the tear film. Its main purpose is to smooth the tear surface and reduce evaporation of tears.

The middle watery layer makes up most of what we ordinarily think of as tears. This layer, produced by the lacrimal glands in the eyelids, cleanses the eye and washes away foreign particles or irritants.

The inner layer consists of mucus produced by the conjunctiva. Mucus allows the watery layer to spread evenly over the surface of the eye and helps the eye remain moist. Without mucus, tears would not stick to the eye.

PATHOGENIC FACTOR:

ETIOLOGY

1. Aqueous production deficient dry eye disease

-Sjögren’s syndrome (SS) is characterized by the combination of aqueous tear deficiency.

-Non-Sjögren’s syndrome are associated with disease of the tear gland such as vitamin A deficiency, trachoma, sarcoidosis, and lymphoma.

2. Evaporative dry eye disease.

- Eyes dry out because of greater tear evaporation as in case of reduced blinking and lid surface anomalies.

- Environmental factors such as central heating, dry climate, air pollution, wind, chemical burns, contact lens wear, or reduced blinking because of driving, watching TV, and computer work can affect the tear film and proceed up to infection, corneal ulcer, and blindness.

-Evaporative loss of tear fluid and dry eyes are usually associated with inadequate lipid layer. The lipid layer stabilizes and retards evaporation of the underlying aqueous layer.

-Rosacea, blepharitis, and MGD (meibomian gland dysfunction) are major causes of evaporative dry eyes. In case of ocular disease rosacea, there is abnormal production of lipids due to meibomian gland dysfunction.

SYMPTOMS

The main symptom of dry eyes is dry and gritty feeling in the eyes. The additional symptoms include burning or itching in the eyes, foreign body sensation, excess tearing, pain and redness of the eyes, and photophobia in some cases.

Sometimes it is also associated with a stringy discharge and blurred, changing vision.

DIAGNOSIS

1. Tear Film Breakup Time (TBUT)

The time required for the tear film to break up following a blink is called TBUT. It is a quantitative test for measurement of tear film stability . The normal time for tear film breakup is 15–20 sec. A fluorescein strip is moistened with saline and applied to the inferior cul-de-sac. After several blinks, the tear film is examined using a broad-beam of slit lamp with a blue filter for the appearance of the first dry spots on the cornea. TBUT values of less than 5–10 seconds indicate tear instability and are observed in patients with mild to moderate dry eye disease . TBUT can also be measured without the addition of fluorescein to the tear film and is called noninvasive BUT (NIBUT). It uses a grid or other patterns directed on the precorneal tear film for observation of image distortion and time from opening the eyes to the first sign of image distortion is measured in seconds .

2. Epithelial Staining

In a staining method, special dyes such as Rose Bengal, lissamine green, and fluorescein are used to determine abnormalities of surface of the eye, quality of tear film, and severity of dryness. It is simple and easy way to recognize the severity of the dryness. Mild cases of DES are detected more easily using Rose Bengal than fluorescein stain and conjunctiva is stained more intensely than the cornea . Staining pattern can be photographed and graded using one of several scoring systems

Fluorescein pools in epithelial erosions, stains degenerating or dead cells, and stains the cornea more than the conjunctiva. Rose Bengal and lissamine green stain dead, devitalized cells as well as healthy cells with inadequate protection . Lissamine green is preferable to Rose Bengal as it avoids the pain, discomfort, and corneal toxicity that are associated with Rose Bengal. However it is somewhat less sensitive and more transient and thus more difficult to appreciate on slit-lamp examination .

3. Schirmer Test

Schirmer test quantitatively measures the tear production by the lacrimal gland during fixed time period. The basic test is performed by instilling topical anaesthetic and then placing a thin strip of filter paper in the inferior conjunctival sac. The patient’s eyes are closed for 5 minutes and the amount of tears that wets the paper is measured in terms of length of wet strip. This Schirmer II test measures tear of lacrimal gland by stimulation of lacrimal reflex arc and wetting of <15 mm after 5 minutes is considered abnormal. The results are variable as any manipulation of the eyelid can alter the results of the test. Further tear drainage can affect the results. Value of less than 6 mm of strip wetting in 5 minutes is accepted as diagnostic marker for aqueous tear deficiency. The Schirmer I test measures both basic and reflex tearing and is performed in a similar way to basic test but without use of a topical anaesthetic.

4. Tear Function Index (TFI)

It is a more specific and sensitive test for quantitative measurement of the tears. It evaluates the tear dynamics of production and drainage and helps detect subjects suffering from dry eye. Its numerical value is obtained by dividing the Schirmer II test value in millimeters by tear clearance rate. The higher the numerical value of TFI, the better the ocular surface. Values below 96 suggest dry eyes. It is also called Liverpool modification .

5. Tear Osmolarity

Osmolarity of normal eye is 309–312 mOsm/L and the value increases with severity of dry eye disease. It gives qualitative information of tear production. It is a very sensitive test but lacks specificity. the best single method for diagnosis and severity determination of DES, when compared with other tests such as TBUT, staining, Schirmer test, and meibomian gland grading.

6. Impression Cytology

The information of etiology of the disease can be obtained from biopsy of conjunctival and lateral lacrimal glands . Impression cytology serves as a minimally invasive alternative to ocular surface biopsy. Progression of ocular surface changes such as marked decrease in goblet cell count and keratinization is monitored by collecting superficial layers and examined microscopically . It is a very sensitive method but requires proper staining and expert microscopic evaluation.

7. Fluorophotometry

This method is costly and uses the decay of sodium fluorescein for measurement of tear flow and volume. The tear turnover rate, defined as the percentage by which the fluorescein concentration in tears decreases per minute after instillation, is also reduced in patients with symptomatic DES . Delayed clearance has been associated with increased tear cytokine concentration, which may contribute to chronic inflammation .

8. Tear Fluid Protein Immunoassays

The protein component of tears may be quantified by measuring tear lysozyme, tear lactoferrin, epidermal growth factor (EGF), aquaporin 5, lipocalin, and immunoglobulin A (IgA) concentrations with enzyme-linked immunosorbent assay (ELISA) techniques.

9. Tear Ferning Test (TFT)

The tear ferning test (TFT) can be used to help diagnose the quality of tears/mucin, DES, and hyperosmolarity. A drop of tear fluid is collected from the lower eyelid and then placed onto a microscope slide and allowed to dry by evaporation. Different forms of branching crystallization patterns are observed and classified. The test diagnoses dry eyes on the basis of the ferning patterns .

10. Other Tests

Meibomian gland dysfunction (MGD) is diagnosed by techniques such as meibometry, meibography, or meiboscopy . Tear evaporation is tested by means of evaporimetry. Meniscometry is used to help diagnose aqueous rear deficient dry eyes.

MANAGEMENT

CONCLUSION

The overarching complexity of the dry eye disease makes it challenging to diagnose and manage accurately. With development of objective tests with precise diagnostic value and minimal disruption of physiological function, accurate diagnosis of disease is possible.

REFERENCES

https://www.hindawi.com/journals/ap/2015/704946

American academy of ophthalmology

Dry eye disease by Dr.Samar Kumar basak