THE DRY EYE The dry eye per se is not a disease entity, but a symptom complex occurring as a sequelae to deficiency or abnormalities of the tear film. Etiology 1. Aqueous tear deficiency. It is also known as keratoconjunctivitis sicca. It is seen in conditions like congenital alacrimia, paralytic hyposecretion, primary and secondary Sjogren’s syndrome, Riley Day syndrome and idiopathic hyposecretion. 2. Mucin deficiency dry eye. It occurs when goblet cells are damaged, as in hypovitaminosis A (xerophthalmia) and conjunctival scarring diseases such as Stevens-Johnson syndrome, trachoma, chemical burns, radiations and ocular pemphigoid. 3. Lipid deficiency and abnormalities. Lipid deficiency is extremely rare. It has only been described in some cases of congenital anhydrotic ectodermal dysplasia along with absence of meibomian glands. However, lipid abnormalities are quite common in patients with chronic blepharitis and chronic meibomitis. 4. Impaired eyelid function. It is seen in patients with Bell’s palsy, exposure keratitis, dellen, symblepharon, pterygium, nocturnal lagophthalmos and ectropion. 5. Epitheliopathies. Owing to the intimate relationship between the corneal surface and tear film, alterations in corneal epithelium affect the stability of tear film. Clinical features Symptoms suggestive of dry eye include irritation, foreign body (sandy) sensation, feeling of dryness, itching, non-specific ocular discomfort and chronically sore eyes not responding to a variety of drops instilled earlier. Signs of dry eye include: presence of stringy mucus and particulate matter in the tear film, lustureless ocular surface, conjunctival xerosis, reduced or absent marginal tear strip and corneal changes in the form of punctate epithelial erosions and filaments. Tear film tests These include tear film break-up time (BUT), Schirmer- I test, vital staining with Rose Bengal, tear levels of Fig. 15.3. Elimination of tears by lacrimal pump mechanism. lysozyme and lactoferrin, tear osmolarity and A B C 366 Comprehensive OPHTHALMOLOGY conjunctival impression cytology. Out of these BUT, Schirmer-I test and Rose Bengal staining are most important and when any two of these are positive, diagnosis of dry eye syndrome is confirmed. 1. Tear film break-up (BUT). It is the interval between a complete blink and appearance of first randomly distributed dry spot on the cornea. It is noted after instilling a drop of fluorescein and examining in a cobalt-blue light of a slit-lamp. BUT is an indicator of adequacy of mucin component of tears. Its normal values range from 15 to 35 seconds. Values less than 10 seconds imply an unstable tear film. 2. Schirmer-I test. It measures total tear secretions. It is performed with the help of a 5 × 35 mm strip of Whatman-41 filter paper which is folded 5 mm from one end and kept in the lower fornix at the junction of lateral one-third and medial two-thirds. The patient is asked to look up and not to blink or close the eyes (Fig. 15.4). After 5 minutes wetting of the filter paper strip from the bent end is measured. Normal values of Schirmer-I test are more than 15 mm. Values of 5-10 mm are suggestive of moderate to mild keratoconjunctivitis sicca (KCS) and less than 5 mm of severe KCS. 3. Rose Bengal staining. It is a very useful test for detecting even mild cases of KCS. Depending upon the severity of KCS three staining patterns A, B and C have been described: ‘C’ pattern represents mild or early cases with fine punctate stains in the interpalpebral area; ‘B’ the moderate cases with extensive staining; and ‘A’ the severe cases with confluent staining of conjunctiva and cornea. Treatment At present, there is no cure for dry eye. The following treatment modalities have been tried with variable results: 1. Supplementation with tear substitutes. Artificial tears remains the mainstay in the treatment of dry eye. These are available as drops, ointments and slowrelease inserts. Mostly available artificial tear drops contain either cellulose derivatives (e.g., 0.25 to 0.7% methyl cellulose and 0.3% hypromellose) or polyvinyl alcohol (1.4%). 2. Topical cyclosporine (0.05%, 0.1%) is reported to be very effective drug for dry eye in many recent studies. It helps by reducing the cell-mediated inflammation of the lacrimal tissue. 3. Mucolytics, such as 5 percent acetylcystine used 4 times a day help by dispersing the mucus threads and decreasing tear viscosity. 4. Topical retinoids have recently been reported to be useful in reversing the cellular changes (squamous metaplasia) occurring in the conjunctiva of dry eye patients. 5. Preservation of existing tears by reducing evaporation and decreasing drainage. Evaporation can be reduced by decreasing room temperature, use of moist chambers and protective glasses. Punctal occlusion to decrease drainage can be carried out by collagen implants, cynoacrylate tissue adhesives, electrocauterisation, argon laser occlusion and surgical occlusion to decrease the drainage of tears in patients with very severe dry eye. SJOGREN’S SYNDROME It is an autoimmune chronic inflammatory disease with multi-system involvement. It typically occurs in women between 40 and 50 years of age. Its main feature is an aqueous deficiency dry eye — the keratoconjunctivitis sicca (KCS). In primary Sjogren’s syndrome patients present with sicca complex– a combination of KCS and xerostomia (dryness of mouth). In secondary Sjogren’s syndrome dry eye and/or dry mouth are associated with an autoimmune disease, commonly rheumatoid arthritis. Its pathological features include focal accumulation and infiltration by lymphocytes and plasma cells with Fig. 15.4. Schirmer test. destruction of lacrimal and salivary glandular tissue.
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