Dry eye is a rising menace of modern day living in pollution and stress and is the commonest problem of eye. Most of us have suffered from dry eye one time or the other. One has to suspect dry eye from the symptoms/history, since the patient does not complain of dryness of eye, as such in most cases. The patient comes with symptoms of foreign body sensation, burning and photophobia. Those with acute external disease have maximum symptoms. Those with chronic disease have minimum symptoms. The term discomfort may be the summation of his symptoms. In patients with kerato-conjuntivitis sicca (KCS), symptoms are usually less pronounced on awakening and worsen as the day progresses. Patients with blepharitis are highly symptomatic on awakening, better within an hour or so, and worsen again later in the day. Are symptoms worsening as the patient is ageing? Is there a seasonal component? What effect does the environment cause on his symptoms?
Ask the patient what is being done now and what has been done in the past to treat the dry eye condition. A detailed list of any topical lubricants and medication must be obtained, including drops as well as ointment. Patients should be asked whether they have had previous placement of temporary collagen plugs. If so, note whether there was improvement in symptoms and whether epiphora occurred and, if so, for how long. Ask if and when silicone punctual plugs were placed or whether previous permanent occlusion with laser or cautery has been performed. If punctal occlusion was done, did symptoms improve or, at least, did it allow a decrease in the use of topical lubricants?
The use of systemic medications must also be noted, as many systemic medications affect tear secretion. The use of systemic steroids and other immunosuppressives such as hydroxychloroquine (Plaquenil), methotrexate and cyclophosphamide (Cytoxan), which may be used in treating patients with Sjogren’s syndrome and other collagen vascular disease should be noted. Patients with decreased tear secretion are at risk for ocular surface infections owing to decreased levels of tear immunoglobulins, lactoferin, and lysozyme. The use of systemic immunosuppressives puts the patient at even greater risk.
Controversy surrounds the issue of which is the best test to use, Schirmer’s or Jones’s. To determine the maximum amount of tear secretion, use a Schirmer’s test without anaesthesia, whereas to determine the minimum amount of tear secretion, use Jones’s basal tear secretion test. For example, in patients with moderate to severe KCS, where it is important to determine whether a functional lacrimal gland is present, use a Schirmer’s test. In suspected mild KCS or contact lens-induced dry eye, where it is important to determine the basal level of tear production, Jones’s test is more appropriate.
Fluorescein or invasive tear breakup time (BUT) is the time elapsed from the blink to appearance of the first random dry spot after application of topical fluorescein to the ocular surface. But is decreased in dry eye patients.
Of all the clinical tests available, rose bengal staining is the most useful and must be part of every dry-eye workup. Also fluorescein stains areas of epithelial cells loss and may actually be a vital dye. Sterile fluorescein impregnated strips or a 2% solution can be used. A drop of fluorescein is applied to the inferior marginal tear strip, and the patient is asked to blink and roll the eyes to ensure mixing. The amount of conjunctival and corneal staining can be graded similarly to rose bengal scoring on a scale of 0 to 4+. As with rose bengal dye, conjunctival staining occurs in mild to moderate KCS and corneal staining in more severe KCS.
The definitive cure of dry eye remains elusive. Dry eye can often be successfully controlled with available therapies including artificial tears, lacrimal punctal plugs and treatment of accompanying diseases eg. meibomitis and allergic conjunctivitis. The mainstay of therapy for dry eyes is the replacement of deficient tear production with tear substitutes. Initially normal saline was used and was found to provide immediate relief in many cases. Later artificial tear containing cellulose ethers such as methylcellulose and hydroxymethylcellulose were added. These thick preparations did indeed last somewhat longer than normal saline, but they tended to blur vision. Further developments included the use of polyvinyl alcohol, a film forming polymer that was believed to have an attraction to the ocular surface.
A wide variety of artificial tear preparations now exist, among which are preparations containing adsorptive polymers, some viscous and others nonviscous. Further attempts to devise a beneficial artificial tear include the use of sodium hyaluronate (Healon) solution and concentrated preparations of methylcellulose. Some years ago, sustained release artificial tear inserts (Lacriserts) became available. These 5mg hydroxypropylcellulose rods dissolve on contact with the ocular surface and release a viscous watery coating. The effects of one of these inserts can last 6 to 12 hours after insertion. The inserts provide a thick precorneal tear film and are particularly useful in KCS with an exposure component. Drawbacks include the development of a shimmering vision, particularly 2 to 3 hours after instillation, which is noted most on attempted reading. Their cost and the difficulty in managing them has limited their usefulness. Lacriserts are effective in patients with severe symptoms, who cannot be managed with frequent instillation of artificial tears.
Preservatives in the artificial tears retard the growth of microbial organisms but also usually have toxic effects on the ocular surface. The frequent use of drops containing preservatives can induce a significant degree of iatrogenic surface disease. The most commonly employed preservatives are benzalkonium chloride, chlorobutanol, thimerosal and chlorhexidine, the most toxic of which is benzalkonium chloride. This cationic detergent emulsifies lipids of cell walls. Chronic use of preservatives containing solutions, particularly in an otherwise compromised ocular surface, can result in irritation, lacrimation, hyperemia, photophobia and even corneal edema. Over the past several years, a number of preservative free products have been formulated. It probably is wiser to recommend the use of preservative free artifical tears to avoid the likelihood of worsening the ocular surface condition from preservative toxicity. Preservation of tear by punctal occlusion with silicon plugs or collagen plug temporarily or by heat or laser application permanently can help in relieving the symptoms of dry eye. The use of acetyl cysteine (10-20%) can help decrease the viscosity of mucus on ocular surface. Such drugs as epidermal growth factor (EGF) and aldose reductase inhibitors (ARI) although not direct treatment for dry eye, do help to protect the corneal epithelium.
There is considerable interest in the immunological aspects of dry eye. Immune targeted dry eyes can modify the lymphocytic activities in the conjunctiva and lacrimal gland. Indeed, cyclosporine-A has reported to be effective for the treatment of canine dry eye andmay also be effective for certain types of dry eye in humans.
Dr. R. Kumar is a Consultant Ophthalmologist: H. No. 232, Sector 16-A, Chandigarh.